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PUBLICATION

National Bureau of Standards

Library, E-01 Admin. Bid*

OCT 6 1969 NBS TECHNICAL NOTE 495

Methods of Measurement for

Semiconductor Materials, Process

Control, and Devices

Quarterly Report

April 1 to June 30, 1969

.....

Hi
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UNITED STATES DEPARTMENT OF COMMERCE

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NATIONAL BUREAU OF STANDARDS • Lewis M. Branscomb, Director

NBS TECHNICAL NOTE 495

ISSUED SEPTEMBER 1969

Nat. Bur. Stand. (U.S.), Tech. Note 495, 45 pages (Sept. 1969)

CODEN: NBTNA

Methods of Measurement for Semiconductor

Materials, Process Control, and Devices

Quarterly Report

April 1 to June 30, 1969

Edited by W. Murray Bullis

Electronic Technology Division

Institute for Applied Technology

National Bureau of Standards

Washington, D.C. 20234

Jointly Supported by

National Bureau of Standards

Defense Atomic Support Agency

U.S. Navy Strategic Systems Project Office

and

National Aeronautics and Space Administration

NBS Technical Notes are designed to supplement the Bureau's regular publications program. They provide a means for making available scientific data that are of transient or limited interest. Technical Notes may be

listed or referred to in the open literature.

For sale by the Superintendent of Documents, Government Printing Office

Washington, D.C, 20402 - Price 50 cents

CONTENTS

PAGE

1. Introduction and Highlights 1

2. Resistivity 6

3. Carrier Lifetime 8

4. Inhomogeneities 12

5. Infrared Methods 14

6. Hall Effect 15

7. Deep-Level Studies 15

8. Gold-Doped Silicon 16

9. High Field Effects 16

10. Specification of Germanium"^ 17

11. Metallization Evaluation 21

12. Processing Facility .

13. Wire Bond Evaluation 23

14. Die Attachment Evaluation 31

15. NASA Measurement Methods 31

16. Second Breakdown 33

17. Thermal Properties of Devices 33

18. Thermographic Measurements 36

19. Microwave Diode Measurements 36

20. Silicon Nuclear Radiation Detectorst 37

Appendix A. Joint Program Staff 40

Appendix B. Committee Activities 41

Appendix C. Solid-State Technology and Fabrication Services . . ^2

Appendix D. Joint Program Publications 43

t Related Projects

iii

METHODS OF MEASUREMENT FOR

SEMICONDUCTOR MATERIALS, PROCESS CONTROL, AND DEVICES

Quarterly Report

April 1 to June 30, 1969

ABSTRACT

This quarterly progress report, fourth of a series,

describes NBS activities directed toward the development

of methods of measurement for semiconductor materials,

process control, and devices. Principal emphasis is

placed on measurement of resistivity, carrier lifetime,

and electrical inhomogeneities in semiconductor crystals

evaluation of wire bonds; and measurement of thermal properties of semiconductor devices. Other tasks involve

study of infrared measurement methods, deep-lying impurities

in InSb, gold in silicon, and high field effects; establishment of a processing facility; evaluation of aluminum metallization and wafer die attachment; review of NASA measurement methods ; and measurement of Hall effect in semiconductor crystals, second breakdown in transistors, and

noise in microwave diodes. Related projects on silicon

nuclear radiation detectors and specification of germanium

are also described. Supplementary data concerning staff,

committee activities, technical services, and publications

are included as appendixes.

Key Words: carrier lifetime; die attachment; electrical

properties; gamma detectors; germanium; gold-doped silicon;

indium antimonide; metallization; methods of measurement;

microelectronics; nuclear radiation detectors; resistivity;

semiconductor devices; semiconductor materials; semiconductor

process control; silicon; thermal resistance; thermographic

measurements; wire bonds.

1. INTRODUCTION AND HIGHLIGHTS

This is the fourth quarterly report to the sponsors of the Joint

Program on Methods of Measurement for Semiconductor Materials , Process

Control, and Devices. The report is subdivided according to tasks which

have been identified as parts of the Program. Sections 2 through 10 deal

with methods of measurement for materials; sections 11 through 15, with
1. INTRODUCTION AND HI6HLI6HTS

methods of measurement for process control; and sections 16 through 20,

with methods of measurement for devices.

Activity is under way on several different methods for measuring

resistivity. Following the decision last quarter to redirect the emphasis from studies of the voltage-breakdown method for measuring resistivity of epitaxial layers to studies of the spreading resistance and

capacitance-voltage techniques for this measurement, effort on this task

has been expanded with the addition of a new staff member. Work on the

traditional four-probe method for measuring resistivity is continuing. A

round robin being conducted with ASTM Committee F-l for the purpose of

extending the range of applicability of the standard method to higher

and lower resistivity values is nearly complete, and the Committee has

expressed an interest in further studies to extend the range up to the

10,000 fl-cm material which is suitable for fabrication of silicon nuclear

radiation detectors. The detailed study of this method as applied to

measurements on epitaxial and diffused layers is also continuing.

Carrier lifetime is highly sensitive to the presence of impurities

which may not affect the resistivity of a semiconductor but which can adversely affect the performance of transistors and other minority car- rier devices. Methods for comparing lifetime in bulk crystals and in

device structures are essential to an understanding of the influence of

both naturally- occurring and neutron-induced recombination and trapping

centers in silicon. Several different methods for measuring carrier

lifetime in semiconductors are being studied. A revised procedure for

making lifetime measurements by the photoconductive decay method is being

prepared for the consideration of ASTM Committee F-l. Significant improvements have been made in the hardware associated with the steadystate photomagnetoelectric-photoconductivity equipment. The scope of

this task is being extended to include consideration of lifetime measurements in device structures, such as transistor base regions, as well as on bulk crystals.

The work on the deep-lying defect in indium antimonide is nearing

completion. The defect has been identified as a lattice vacancy which is

thought to occur in the indium sub-lattice. This conclusion is based on the results of resistivity, Hall coefficient, and carrier lifetime measurements on high-resistivity indium antimonide specimens before and after

the introduction of lithium. Although this study, which has been con- ducted as a doctoral thesis topic, is not applicable to characterization

of silicon, it does provide new insight into the properties of III-V

compounds

Poor adhesion of metal films is a significant cause of device failures. The first efforts on the metallization evaluation task are being
1. INTRODUCTION ANO HIGHLiGHTS

directed toward the development of more reliable test methods for determining film adhesion. The scratch test for determining the adhesion

characteristics of aluminum metallization films deposited on silicon and

silicon oxide has been selected for detailed study, and apparatus for

performing this test has been constructed. At the same time, the literature on thin-film adhesion testing is being methodically searched.

The small fraction of wire bonds which fail constitutes a serious

problem in semiconductor device reliability. A significant portion of

the Joint Program is directed toward the evaluation and development of

methods for testing wire bonds to identify bonds which may fail. A

critical review of this field is well under way; field visits to 27 different organizations have been completed, and most of the relevant literature in the field has been obtained. The review is expected to focus on the advantages and limitations of the various practices now employed in

the industry and to pinpoint areas where additional information must be

obtained. At the same time experimental efforts have been initiated in

several areas.

1. An improved method for grasping the wire during a pull test was developed last quarter. Since the wire is grasped without deformation and the bond may be pulled in any direction,

this convenient method, which involves the use of a quicksetting hot-melt glue, permits increased control of the

test conditions. It is also possible to test single bonds.

2. Preliminary studies of ultrasonic bonding with aluminum ribbon wire- have demonstrated that lower bonding pressures than

those required for round wire of the same cross section will

produce satisfactory bonds. This suggests that harder and

stronger ribbon wire may be used to make bonds without the

risk of damage to the semiconductor die. The use of the

harder wire is expected to result in stronger bonds. As

an added advantage it turns out to be easier to use the

ribbon wire than round wire for making ultrasonic bonds.

3. Initial tests of a number of ultrasonic bond monitoring

techniques have led to the selection of a capacitor microphone technique for future studies. An extension tip

damped with silicone rubber and polytetrafluoroethylene was developed to improve the resolution of the capacitor microphone system.

4. Resonance characteristics of a nickel magnetos trictive transducer, tapered horn, and bonding tool were measured under

both constant current and constant voltage conditions. These

results suggest that a system with a constant current source

is less sensitive to variations in the source frequency

than is one with a constant voltage source. It was also
1. INTRODUCTION AND HIGHLIGHTS

found that the maximum tip vibration amplitude occurred at

a different frequency from the transducer resonance as indicated by a current meter in series with the transducer

coil.

5. It was also established that resonance modes of bonding

tools can be observed with the high-resolution capacitor

microphone. Thus detailed studies of bonding tool resonance

including torsional and other modes of vibration can be

undertaken.

An abrupt decrease in d-c current gain in interdigitated mediumpower transistors was observed to occur at the same operating condition

as that for which the thermal resistance as measured by the forwardbiased base-emitter voltage abruptly increases. The observation by means

of thermographic phosphors of hot-spot formation at the same operating

condition suggests that the relatively simple measurement of d-c current

gain may be a practical method for identifying the onset of hot-spot formation.

Organizational plans were completed for the Symposium on Silicon

Device Processing to be held in June, 1970 under the joint sponsorship

of ASTM Committee F-l and NBS. The Symposium is intended to bring together engineers and applied scientists actively engaged in the silicon

device technology field so that they may discuss the most advanced

measurement methods for process control and materials characterization

in an unhurried and informal atmosphere. The basic theme of the meeting

is to stress the interdependence of measurements, techniques, facilities,

and materials as they relate to the overall problems of inproving and

advancing silicon device sciences and technologies. The opening session

will consist of invited papers on silicon crystal growth, surface preparation, diffusion, epitaxy, and silicon oxides and nitrides. Subsequent sessions will deal with the unit processing operations , epitaxy and

diffusion , from the standpoint of the required techniques and facilities

as well as the properties and characterization of their product. Surface

preparation and interdependence of the unit processing operations will

also be discussed.

The Joint Program was undertaken last year to focus NBS efforts to

enhance the performance, interchangeability , and reliability of discrete

semiconductor devices and integrated circuits through improvements in

methods of measurement for use in specifying materials and devices and

in control of device fabrication processes. These improvements are intended to lead to a set of measurement methods which have been carefully

evaluated for technical adequacy, which are acceptable to both users and

suppliers, and which can provide a common basis for the purchase specifications of government agencies. In addition, such methods will provide

a basis for controlled improvements in essential device characteristics,
1. INTRODUCTION ANO HIGHLIGHTS

such as uniformity of response to radiation effects. The Program is

supported by the National Bureau of Standards [1], the National Aeronautics and Space Administration [2], the Defense Atomic Support Agency

[3], and the U. S. Navy Strategic Systems Project Office [4]. Because

of the cooperative nature of the Program, there is not a one-to-one corre- spondence between the tasks described in this report and the projects

by which the Program is supported. Although all sponsors subscribe to

the need for the entire basic program for improvement of measurement

methods for semiconductor materials, process control, and devices, the concern of certain sponsors with specific parts of the Program is taken

into consideration in planning.

Additional background information on the Program and individual

tasks may be found in earlier reports in this series (see Appendix D). Besides the tasks sponsored under the Joint Program, this report contains

descriptions of activity on related projects supported by NBS or other

agencies. Although the specific objectives of these projects are different from those of the Joint Program, much of the activity undertaken in

these projects will be of interest to Joint Program sponsors. The

sponsor of each of these related projects is identified in the description of the project.

1. Through Research and Technical Services Projects 4251120. 42511 93

4251126, 4252128, 4254111, 4254112, and 4254115.

2. Through Order ER- 11897, Electronics Research Center. (NBS Project

4259523) J "

3. Through Inter-Agency Cost Reimbursement Order 808-69. (NBS Pronect

4259522)

r° ]ect

4. Administered by U. S. Naval Ammunition Depot, Crane, Indiana through

Cost Reimbursement Order P09-0016. (NBS Project 4259533)
METHODS OF MEASUREMENT FOR SEMICONDUCTOR MATERIALS

2. RESISTIVITY

Objective : To develop improved methods, suitable for use throughout

the electronics industry, for measuring resistivity of bulk, epitaxial,

and diffused silicon wafers.

Progress : A round robin based on the ASTM four-probe method for

measuring resistivity of silicon wafers [l] is being conducted in co- operation with ASTM Committee F-l on Materials for Electron Devices and

Microelectronics to determine the precision which can be expected when

measuring bulk silicon wafer resistivity down to 0.001 fi-cm and up to

2000 fi-cm. All data have been received from the eight participating

laboratories, and all calculations have been checked. Tabulation of the

results is nearly complete.

To assist in the extension of the method to epitaxial and diffused

layers, studies of the dependence upon current, probe force, and surface

condition of the resistivity of silicon wafers as measured by the fourprobe method are continuing. Material in the resistivity range 0.001 to

1000 fl-cm is being studied at probe forces of 25, 50, 100, and 150 g and

current values between 0.1 and 10 times the values recommended for its

resistivity level in the ASTM procedure [1]. Three surface conditions,

lapped (with 5 ym alumina), mechanically polished, and chemically polished, are being used.

Measurements are also being made of the contact resistance between

the probe points and the wafer surface as a function of current, probe

force, and surface condition. The results of these measurements are expected to aid in designing appropriate analog circuits used to test

the voltage measuring equipment in these four-probe measurements. Both

resistivity and contact resistance measurements have been completed on wafers with lapped surfaces.

Calculations of the results of measurements made as part of a Committee F-l sponsored round robin based on a proposed two-probe method

[2] for measuring the resistivity of cylindrical silicon crystals have

been completed and sent to the coordinator of the round robin.

(F. H. Brewer)

1. "Method of Test for Resistivity of Silicon Slices Using Four Pointed

Probes'* (ASTM Designation: F84-68T), 1968 Book of ASTM Standards,

Part 8, November, 1968. This method covers the range 0.05 to 120

fl-cm.

2. For a general description of the two-probe method see "Method of Test

for Resistivity of Semiconductor Materials" (ASTM Designation:

F43-57T), 1968 Book of ASTM Standards, Part 8, November, 1958.
2. RESISTIVITY

Commercially available components have been selected for use in the

measurement of spreading resistance. Design plans are being developed

for a probe holder assembly which incorporates features described in the

literature [3]. Several materials are being considered for use as probe

tips in the spreading resistance apparatus. These include tungsten

carbide, stainless steel, osmium, tungsten-ruthenium alloy, and silicon

carbide. A source of silicon carbide with controlled doping level has

been found, and a procedure for laboratory use, but it may be prohibitively complex for large scale use. No further fabrication refinements are planned until it is determined whether silicon carbide is a satisfactory

probe material.

The suitability of an available spectrophotometer for measuring

epitaxial layer thickness and bulk resistivity by infrared techniques

as suggested by ASTM Committee F-l [4, 5] is being evaluated.

(J. R. Ehrstein)

Instrumentation has been surveyed for the purpose of establishing

a capability for measuring doping profiles in epitaxial films by the

capacitance-voltage technique [6], In addition to the knowledge of the

diode fabrication procedures and the method of epitaxial layer growth,

a good understanding of this measurement method requires study of the

effects of the frequency used for the capacitance measurement. Since a large amount of data is required to profile a single epitaxial layer,

it is intended to automate the data-taking process. However, instrumentation for capacitance measurement which is capable of being automated has only been found for use at 100 kHz and 1 MHz„ Hence it may be

necessary to concentrate work at these two frequencies and to sample

effects at other frequencies with equipment which is not automated.

(J. R. Ehrstein and G. N. Stenbakken)

3. J. M. Adley, M. R. Poponiak , C. P. Schneider, P. A. Schumann, Jr.,

and A. H. Tong, "The Design of a Probe for the Measurement of the

Spreading Resistance of Semiconductors," Semiconductor1 Silicon,

R. Haberecht and E. Kern, Eds., The Electrochemical Society, New

York, 1969, pp. 721-731.

4. "Method of Test for Thickness of Epitaxial Layers of Silicon on Substrates of the Same Conductivity Type by Infrared Reflectance"

(ASTM Designation: F95-68T), 1968 Book of ASTM Standards, Part 8,

November, 1968.

5. P. A. Schumann, and R. P. Phillips, "Comparison of Classical Approximations to Free Carrier Absorption in Semiconductors," Solid-State

Electronics 10, 943-948 (1967).

6. G. W. Reuttinger, S. J. Regas , D. J. Sidor, and B. Schwartz, "An

Automatic Test Set for Measuring Dopant Concentration Profiles in

Epitaxial Films" Solid-State Electronics 12, 31-39 (1969).
2. RESISTIVITY

Plans : Results of the four-probe resistivity round robin will be

fully tabulated and reported to ASTM Committee F-l. Several 10,000 ft-cm

wafers will be evaluated for uniformity prior to the initiation of a new

round robin to extend the method to a still higher resistivity range.

The investigation of the dependence upon current and probe force of

resistivity as measured by the four-probe method and of contact resistance between the probe point and the surface of the wafer will proceed.

Measurements will be made for the same range of variables previously

used, first on mechanically, and then on chemically, polished surfaces.

Preliminary measurements by the spreading resistance method of

resistivity of epitaxial layers will be made. Special emphasis will be

given to solution of problems related to the low signal levels which

occur and the high electrical isolation required by the method. A more

versatile spreading resistance probe assembly will be designed and fabrication will begin.

Capability will be established for measuring impurity concentration

and epitaxial thickness by infrared methods although available instrumentation may limit the range of concentration or thickness which can be

measured.

3. CARRIER LIFETIME

Objective : To determine the fundamental limitations on the precision and applicability of the photoconductive decay method for measuring

minority carrier lifetime and to develop alternate methods for measuring

minority carrier lifetime in germanium and silicon which are more precise, more convenient, or more meaningful in the specification of material for device purposes.

Progress: Dispersion of light in the unusually thick lenses of the

optical system in the steady-state photomagnetoelectric effect-photoconductivity (PME-PC) equipment made focusing the infrared illumination

difficult to approximate by visible light. The problem was eliminated by

changing to a front-surface-mirror optical system. In addition, the new system also provides greater illumination intensity with the same light

source.

In order to determine whether the unused harmonics of the trapezoidal wave form of the chopped light were producing unwanted effects in

the PME-PC measurement, the chopper was modified to produce a sinusoidal

variation of light intensity by rotating an array of equi-spaced circular holes past a stationary slit with a width approximately equal to the
3. CARRIER LIFETIME

diameter of each of the circular holes [1], A similar arrangement on the same chopper modulated the illumination of a photodiode to generate

a reference signal. The nonlinear response of the photodiode generated

higher order harmonics. The second harmonic, which had an amplitude a third that of the fundamental, was reduced 27 dB by an electronic lowpass filter. Such harmonic purity is not required for operation of the

lock-in amplifier, but it is required for the substitution method of

measuring the PME and PC currents because the calibration of these

currents is based on the rms voltage input to the precision attenuator

and only the fundamental component is utilized; therefore, the indicated

current is low by the ratio of the rms value of the fundamental to the

rms value of the fundamental plus harmonics. These modifications substantially improved operation of the equipment and are now being used

in connection with the deep-level studies (see Section 7).

(W. E. Phillips and A. W. Stallings)

Equipment for extending the measurement capability of the photoconductivity decay (PCD) lifetime apparatus to shorter lifetimes was considered. Planned studies on gold-doped silicon specimens will provide an opportunity to evaluate the applicability of the PCD method for measuring

lifetimes in the nanoseconds or tens-of- nanoseconds range. The following systems are being evaluated: (l) a short-duration flash tube, (2) a steady light modulated rectangularly by a Pockels cell, and (3) a steady

light modulated sinusoidally by a Pockels cell. The study includes an estimate of the performance of each of these systems, an estimate of the

cost involved to assemble each system, and a survey of manufacturers

from whom the equipment could be purchased.

The study of the contactless PCD lifetime measurement technique of

Nishizawa, et at.. [2] was continued. In this technique, the specimen is

placed on a specimen holder which consists of two D-shaped electrical

contacts embedded in a plastic block. The contacts are separated from

each other by about 1 mm and are connected in parallel with the tank circuit of an r-f oscillator. The speoimen is placed on an insulator, such

as a piece of vinyl tape, mica, or one or more glass slides, which is

placed on the contacts and serves as the dielectric of the capacitance

connecting the specimen to the tank circuit. When the specimen illumination is varied, the change in conductivity of the specimen causes a change in the loading of the oscillator, which changes the Q of the

1. For an analysis of a similar system, see R. B. McQuistan, "On Radiation Modulation," J. Opt. Soc. Am. 29, 70-74 (1959).

2. J. Nishizawa, Y. Yamoguchi, N. Shoji, and Y. Tominaga, "Application

of Siemens Method to Measure the Resistivity and Lifetime of Small

Slices of Silicon," Ultrapurifioation of Semieonduetor Materialss MacMillan Co., New York, 1962, pp. 636-644.
3. CARRIER LIFETIME

circuit, and produces a modulation of the oscillator amplitude. Demodulation of the oscillator output yields an illumination-dependent signal

which is observed on an oscilloscope. The time constant of the signal

which is observed after the illumination is extinguished is used to calculate the specimen lifetime.

The main difficulty with this technique is that the time constant of

decay of excess carriers in the specimen is not always equal to the time

constant of the demodulated oscillation envelope signal. This occurs be- cause the equivalent resistance of the specimen is not in parallel with

the tank circuit but is part of a network composed of the two coupling

capacitors, specimen holder capacitances, and a resistor representing the

effective specimen resistance. When a transformation is applied to this

network it is found that changes in the effective specimen resistance and

changes in the equivalent parallel resistance are not always proportional.

Experimentally this leads to erroneously long lifetime measurements. It was found, however, that by centering the specimen on the specimen holder

so that its longitudinal axis is perpendicular to the specimen holder

slot, and by reducing the coupling capacitance by elevating the specimen

as far above the specimen holder as possible consistent with obtaining a measurable signal, the maximum difference between contactless and standard PCD lifetime measurements on a group of twelve specimens under con- ditions of identical illumination was eight percent.

An apparatus to measure PCD lifetime by a second contactless method

[3] is being constructed so that it may be compared with the method

described above. In this method one measures the power absorbed by a specimen placed in a slotted cage inside the coil of an r-f oscillator

tank circuit

A draft of a revised standard procedure for measuring carrier lifetime by the PCD method has been prepared and is being reviewed prior to

submission to ASTM Committee F-l. (R. L. Mattis)

Efforts on the study of the correlation of carrier lifetime in silicon with characteristics of nuclear radiation detectors made from the same material (see Section 20) were concentrated in the area of diode

recovery measurements of carrier lifetime. Voltage decay measurements on point-contact diodes were continued. Point-contact diodes were selected

for study because their fabrication leaves the bulk semiconductor material unaltered by heat treatment. Although the initial region of linear

voltage decay seen with junction devices was not observed in point3. R. M. Lichtenstein and H. J. Willard, Jr., "Simple Contactless Method

for Measuring Decay Time of Photoconductivity in Silicon," Rev. Soi.

Instrvm. 38, 133-134 (1967).

10
3. CARRIER LIFETIME

contact diodes (NBS Tech. Note 488, p. 6) it has been suggested [4]

that the tail of the decay curve should be an exponential function of the

lifetime. Measurements on diodes fabricated from wafers of several

values of resistivity so far failed to reveal an exponential tail. Since

the early portion of the voltage decay depends on the effective junction

radius of the point-contact rather than the lifetime [5, 6], efforts were

shifted to the reverse recovery technique. However, the recovery curves

did not exhibit the flat region of constant reverse current such as was seen with p-n junction diodes so it was not possible to interpret them in

terms of carrier lifetime. It can therefore be concluded that neither

the voltage decay technique nor the reverse recovery technique is readily

adaptable to making lifetime measurements with point-contact diodes.

Consideration of alternate types of diodes for this study led next

to the surface barrier diode. Diodes for initial studies are being fabricated on p-type silicon with resistivity of 1500 ft -cm. Ohmic contact

is made to the base by an evaporated layer of gold on a lapped surface.

The barrier is formed on the wafer by evaporating gold on the face of

the wafer after etching.

An experiment to study the reproducibility of the reverse recovery

technique for measuring carrier lifetime in p-n junction diodes is being

conducted. Lifetimes of a group of seven commercial diodes have been

measured monthly for a period of six months. (A. J. Baroody)

Plans: Study of the surface photovoltage method will be resumed

when PME-PC measurements on indium antimonide are completed (see Section

7).

A decision will be made regarding the extension of the PCD measurement capability to shorter lifetimes. Comparisons of the two contactless

methods for measuring PCD lifetime will be undertaken when the apparatus

for the second method is completed. The draft of the revised standard

method for PCD measurements will be reviewed and submitted to ASTM Committee F-l for its consideration.

Voltage decay measurements of diode recovery lifetimes will be made

on surface barrier diodes. The voltage decay technique will also be

applied to p-i-nt alloyed, and diffused diodes which will be fabricated.

Mathematical and experimental investigation of the dependence of the

H. L. Armstrong, "On the Tail in the Transient Behavior of PointContact Diodes," Proo. IRE 45_, 696-697 (1957).

H. L. Armstrong, "On Open Circuit Transient Effects in Point-Contact

Rectifiers," J. Appl. Phys., 27_, 420-421 (1956).

B. R. Gossick, "On the Transient Behavior of Semiconductor Rectifiers," J. Appl. Phys. 27, 905-911 (1956).

11
3. CARRIER LIFETIMF

carrier lifetime as measured by diode recovery techniques upon injection

levels in the various diode structures will be continued.

Results of the experiment to study the reproducibility of the re- verse recovery technique will be analyzed. When this is completed, the

dependence of the measured reverse recovery time on the frequency and

amplitude of the input square wave will be studied. Efforts to modify

the circuitry to permit forward to reverse current ratios between 0.01

and 100 will continue.

A study of methods for measuring minority carrier lifetime in transistor structures will be undertaken. The problems encountered and the

contradictions between methods and with bulk measurements will be

investigated in regard to making more meaningful carrier lifetime meas- urements for device purposes. On the basis of such findings, further

experimental carrier lifetime measurements under various geometries will

be planned.

4. INHOMOGENEITIES

Objective : To develop improved methods for measuring inhomogeneities responsible for reduced performance and reliability of silicon devices and, in particular, to evaluate a photovoltaic method as a means

to accomplish this.

Progress: It was decided to concentrate on the problems encountered

in the surface treatment of p-type silicon. A number of surface treatments for reducing the surface recombination velocity, s, in p-type silicon were tried but their use continued to result in the observation of

anomalous photovoltages as described previously (NBS Tech. Note 475,

p. 8). Further investigation of these treatments was suspended, however,

when success was achieved by modifying a treatment used earlier which had

not consistently reduced s.

This treatment involves an etch (10 HNO3 + 1 HF) to remove the work

damage induced in shaping the specimen and an oxidizing agent (hot sodium

dichromate) to create a surface accumulation layer which inhibits the

diffusion of minority carriers to the surface. Consistent reductions in

s were achieved with this treatment by increasing the etching time in the

treatment from about 1.5 min to about 4.5 min which increased the thickness of the material removed from about 15 ym to about 50 urn. Apparently

the shorter etching time used previously did not always remove enough of

the work-damaged silicon.

Reproducible results have been obtained, using this preparation,

with four p-type bar-shaped silicon specimens (two with resistivity of

12
4. INH0H06ENEITIES

'vM-O fi-cm and two of ^10 fi-cm). Two of these specimens were ones for

which the surface treatment using the shorter etching time had been un- successful. Resistivity profiles obtained from two-probe measurements

were available for two of the specimens. They agreed with the respective

photovoltaic resistivity profiles to within 1 percent* Such agreement

is typical of previous measurements on silicon and germanium when the

surface treatment had been successful.

A new airtight enclosure for the specimen holder with a transparent top for the light probe has been incorporated in the measurement

apparatus. The use of the enclosure has much improved shielding from

stray light and air currents

Originally, the enclosure was constructed as part of the equipment

to be used to maintain a controlled ambient atmosphere for the specimen

during the surface treatment and the photovoltaic resistivity measurements if this proved to be necessary. Use of a controlled atmosphere was suspended at least until work on n-type silicon indicates that such measures will be required.

A preliminary attempt was made to reduce s by placing the specimen

between transparent capacitor plates and applying a voltage to induce an accumulation layer in the specimen surface. No measurable effect was observed for applied voltage as high as 550 V. Additional study of this

method was suspended in view of the success of the surface treatment on p-type silicon.

To increase the generally smaller values of photovoltage and photoconductivity measured on circular specimens, a 500-W incandescent lamp

was tried. Because of the less efficient focusing element in the lamp,

the intensity of light that reached the specimen was not significantly

greater than that obtained from the 150-W lamp used previously. Another

alternative which has been considered but not yet tried is the use of a helium-neon laser with an output power of 50 mW at 1.15 ym and of 5 mW

at 1.084- ym. The output power at 1.15 ym is estimated to be greater

than the power incident on the specimen from the incandescent lamp because of the highly inefficient optical means of forming the light probe

from the lamp.

Work on circular specimens was deferred during this quarter to con- centrate on improving the surface treatment of p-type silicon.

(D. L. Blackburn and H. A. Schafft)

Plans: Photovoltaic resistivity measurements will be made on p-type

silicon bars with a resistivity of about 1 fl-cm to investigate problems

in making measurements at lower resistivity levels.

Photovoltaic resistivity measurements will be made on n-type germanium and p-type silicon circular specimens to substantiate the

13
4. INH0M06ENEITIES

usefulness of the equation which relates resistivity gradient to photovoltage (NBS Tech. Note 488, p. 9).

Efforts will be made to improve the surface treatment for n-type

silicon. The first treatment to be examined is similar to the one used

successfully for p-type silicon except that a reducing agent is substituted for the oxidizing agent.

A preliminary trial of a laser source will be made to determine its

utility as a light probe for circular specimens.

5. INFRARED METHODS

Objective : To evaluate impurity photoconductivity as a method for

detecting low concentrations of deep-lying impurities such as copper,

gold, iron, and nickel in silicon and germanium, and to assist ASTM

Committee F-l in extending the applicability of infrared absorption as a method for detecting impurities such as oxygen and carbon in silicon and

germanium.

Progress : Specimens of copper-doped germanium were prepared for

impurity photoconductivity measurements by diffusing copper, which had

been electroplated on the surfaces, into the germanium for a time sufficient to saturate the specimen. A specimen with 10 14 copper atoms/cm3 was prepared by heating at 570°C for 288 hours, and a specimen with 10 15

copper atoms/cm3

, by heating at 650°C for 48 hours. The specimens were

quenched in water. So that the results will be useful for the germanium

program (see Section 10), the starting material was 20 fi-cm p-type

germanium, rather than n-type which is normally used for infrared detectors. Measurements are made with the specimen mounted on the cold

finger of a liquid helium cryostat. The electrical circuit consists of a d-c power supply and load resistor in series with the specimen. The

response as a function of wavelength is determined across either the load

resistor or specimen with a lock-in detector. So far photoconductivity

has been observed only to 20 urn, but improvements are under way so that

response can be detected at longer wavelengths. The long wavelength

limit for copper in germanium is 31 um, which corresponds to the copper

impurity level at 0.04 eV above the valence band. (W. R. Thurber)

Plans : Photoconductivity measurements will continue on the germanium specimens saturated with copper.

A summary report will be prepared describing the work completed on the determination of oxygen in silicon and germanium by infrared absorption methods.

14
6. HALL EFFECT

Objective: To establish a facility for making measurements of Hall

coefficient as a function of temperature between 4 and 350 K and to

improve methods for collecting and interpreting Hall effect data.

Progress : The Hall effect apparatus is being modified to permit

automatic measurements on high-resistivity materials. The design work

is essentially completed, operational amplifiers have been purchased, and

a new specimen holder is being fabricated.

The report concerning the use of a time-shared computer to control

the Hall experiment is nearly complete. Work on the report on Hall

measurements and their interpretation is continuing.

(W. R. Thurber and W. M. Bullis)

Plans : Work will continue on the new Hall apparatus which will be

used for measurements of high-purity germanium (see Section 10) and golddoped silicon (see Section 8).

The two reports now being prepared will be completed and published.

7. DEEP -LEVEL STUDIES

Objective : To determine the nature and origin of the deep- lying

centers in high-resistivity indium antimonide.

Progress : From the results of resistivity, Hall coefficient, and

carrier lifetime measurements on high-resistivity indium antimonide before and after the introduction of lithium, it was concluded that the

residual deep-lying energy level in indium antimonide is associated with

a lattice vacancy, probably on the indium sublattice. Lithium added to

the material fills the vacancies and removes the residual level [1].

The change caused by the addition of lithium was clearly evident in

the lifetime measurements : at liquid nitrogen temperature , the electron

lifetime was four orders of magnitude greater in the specimens treated

with lithium. The interpretation of lifetime data was not completely

unambiguous, however, because the variation of lifetime with temperature

was not of the form required by elementary theory. In particular, the

lifetimes calculated from photoconductivity and photomagnetoelectric

1. J. L. Scales, "Investigation of the Residual Defect in Indium

Antimonide," Ph. D. thesis, Physics Department, University of Maryland (March, 1969).

15
7. DEEP-LEVEL STUDIES

effect measurements are expected to be equal at some warmer temperature,

according to the theory, but this was not observed.

Consequently attempts have been made to improve the lifetime measurements. The optical system was changed, and a new light chopper was made (see Section 3). In addition a null method was adopted for measuring the induced photo-voltages. In the new arrangement, the specimen

is driven with a sinusoidal voltage that has the same frequency as, but

can be adjusted to be 180 deg out of phase with, the induced signal. By

varying the amplitude of the driving voltage, one can null out the induced photo-voltage without turning off the light or changing any experimental condition, as was previously necessary. (J. L. Scales)

Plans : Some lifetime measurements on Li-treated and untreated

specimens will be repeated, using the improved apparatus and the null

techniques for making measurements. It is hoped that the discrepancy

between theory and experiment at the warmer temperatures can be resolved.

A final report will be prepared on completion of the measurements.

8. GOLD-DOPED SILICON

Objective : To characterize n- and p-type silicon doped with gold

and to develop a model for the energy level structure of gold-doped

silicon which is suitable for use in predicting its characteristics.

Progress : Work on establishment of procedures for diffusing gold

into silicon wafers was initiated. A gold film, 40-nm thick, was vacuum

evaporated onto the polished surface of a number of 10-fi-cm boron-doped

silicon wafers preparatory to carrying out diffusions. No difficulty was experienced with the adhesion of the gold to the silicon surface.

(J. Krawczyk)

Plans : Gold diffusions will be carried out at 850°C, 950°C, 1050°C,

1150° C, and 1250°C for one-half hour to obtain specimens containing

different amounts of gold. Diffusions will be done in an oxygen atmosphere.

Electrical measurements on specimens before and after gold diffusion

will begin.

9. HIGH FIELD EFFECTS

Objective : To study the physical characteristics of hot carrier

semiconductor structures and relate these to performance of devices.

16
9. HIGH FIELD EFFECTS

Progress: The priority assigned to this task has been reduced to

permit acceleration of the wire bond evaluation task (see Section 13).

(G. G. Harman)

Plans : As time becomes available, further measurements will be

made. The effect of strong magnetic fields will be investigated and the

temperature dependence of the oscillation will be studied.

10. SPECIFICATION OF GERMANIUM1

"

Objective : To measure the properties of germanium crystals and to

correlate these properties with the performance of germanium gamma-ray

detectors in order to develop methods for the early identification of

crystals suitable for fabrication into lithium- compensated gamma-ray

detectors.

Progress : Pulse height distributions (gamma-ray peaks) produced by

monoenergetic gamma-rays in Ge(Li) detectors are being studied to deduce

information on crystal quality. Spectral -data obtained from collimatedbeam scanning of Ge(Li) detectors have been analyzed by a specially

written computer program, PEAKFIT-III, written in OMNITAB programming

language [1], Each data set, consisting of the 662-keV 137 Cs gamma-ray

peak and a pulser-generated peak at somewhat higher equivalent energy, is

analyzed to obtain the positions of the peak centroids, resolution at

1/2 and 1/10 maximum peak height, the detector contribution to peak width,

AE n » and the ratio of the variance in the number of ion pairs produced

to the number of ion pairs produced, a

2 /N. The background distribution

was fitted by a polynomial of degree 2 and subtracted from the raw data

prior to peak analysis [2], Using the method of least squares a function

of the following form is fitted to the spectral peaks:

Y(xi

) = exp (a + bx^ + cx^ 2

) (1)

where Y(x-j_) is the number of counts in channel x^ and a, b, and c are adjustable constants.

t Supported by the Division of Biology and Medicine, U. S. Atomic

Energy Commission. (NBS Project 4259425)

1. J. Hilsenrath, G. G. Ziegler, C. G. Messina, P. J. Walsh, and R. J.

Herbold, OMNITAB3 A Computer Program for Statistical and Numerical

Analysis, NBS Handbook 101, rev. ed. , January, 1968.

2. The origin of the distribution of points between the full energy peak

and the Compton "knee" is the subject of continuing study.

17
10. SPECIFICATION OF GERMANIUM

Reports of measurements of an effective Fano factor which have

previously been made using uncollimated gamma-ray sources included

attempts to dissociate the effects of carrier trapping and noise from the

result [3-5], These studies yielded a value of about 0.13 for the Fano

factor in germanium. In the present work, using a collimated source of

gamma-rays, it has been possible to determine explicitly the region of a Ge(Li) detector where carrier trapping is minimized and thus obtain a better measure of the Fano factor.

Measurements of the detector resolution (AED

) of a 2-cm 3 Ge(Li) detector as a function of both electric field and beam scanning position

between the n

+-i and i-p junctions were made by recording pulse height

spectra of the 662-keV L37 Cs gamma-ray peak along with a pulser-generated peak. Analyses of AED

as a function of scanning position showed

that at low electric fields electrons were preferentially trapped in the

detector; at high fields the trapping was greatly reduced. However,

irradiation of the region 0.5 to 1.5 mm from the n

+ -contact, where the

effect of electron trapping is minimized because the signal is due mainly

to holes traversing the i-region, yielded the greatest improvement in

detector resolution.

The quantity a

2 /N plotted against distance from the n+ -contact of

the detector is shown in Fig. 1. At the top of the figure, the boundaries of the t-region are indicated at 0.5 and 5.5 mm from the contact

surface. The depth of the n

+-region (500 ym) is in good agreement with

measurements made after the initial diffusion of lithium into the crystal

[6]^ The data for a field of 1200 V/cm (single measurements) show that

a

2 /N increases (from increased AE

n

) as the beam moves toward the i-p

junction. Spectra are obtained when the beam is centered at the ft +- contact (0 mm) due both to the finite width of the beam and to the larger

width of the secondary ionization sheath produced in the detector. These

points are shown only for reference purposes. Data points at an electric

field of 2400 V/cm show values of a

2 /N which are significantly lower than

0.13 by one-sided 99.5 percent confidence interval t-test [7] in the

3. H. R. Bilger, "Fano Factor in Germanium at 77°K," Phys. Rev. 193 , 283-253 (1967).

4. J. M. Palms, P. Venugopalo Rao, and R. E. Wood, "The Characteristics

of an Ultra-High Resolution Ge(Li) Spectrometer for Singles and

Coincidence X-Ray Gamma-ray Spectra," IEEE Trans. Nuel. Sei. NS-16 , 36-46 (January, 1969).

5. A. H. Sher and B. D. Pate, "Determination of the Fano Factor in Germanium at 77°K," Nuel. Instr. and Meth. 3 to be published.

6. A. H. Sher, "Lithium Ion Drift Mobility in Germanium," J. Appl.

Phys. 40, 2600-2607 (1969).

7. M. G. Natrella, Experimental Statistics, NBS Handbook 91, rev. ed.

1966, p. 3-20.

18
cvj

u. / i I + . n -l

i ~ni" -i- T 1 i-p

o

0.6

Ge(Li) DETECTOR 83- 2

0.5 o 1200 V/cm

. 2400 V/cm

-

0.4

o

-

o

0.3 -

( )

0.2' L ° o 1

i

i

. <

>

>

< i

o . '

0.1 -

i I

'

' < I

[ *

F = 0.13 -

i i J .

n n i i i .__ _ .1 ..... i 12 3 4

DISTANCE FROM n+

- CONTACT (mm)

Fig. 1: a

2 /N as a function of distance from the n

+ -contact of Ge(Li)

detector 83-2. Error bars on the data points for the field of

2400 V/cm are the 95 percent confidence interval estimates of

the mean [7]. Estimated standard deviations are smaller.

19
10. SPECIFICATION OF 6ERMANIUM

region from 0.5 to 1.5 mm. The error bars represent the two-sided 95

percent confidence interval [7] of the mean of at least four measurements.

The mean value of c

2 /N for data points from 2.0 to 4.5 mm is 0.114 but is

not significantly different from 0.13 by the above t-test. Analysis as in earlier reports [3-5] of the response of the detector operated at 2400

V/cm when irradiated by an uncollimated 137Cs source yielded a

2 /N = 0.133.

If the upper limit of F is given by a

2 /N, the present results show that

for the region of this detector near the n

+ -contact , where electron trapping is negligible, F < 0.13. It is difficult to assign a specific value

for the Fano factor, however, as secondary ionization effects make detailed knowledge of the beam width difficult to obtain , but it is

probable that an upper limit for the Fano factor is a

2 /N - 0.10, the

average value in the region 0.5 to 1.5 mm from the contact. These results

have been submitted for presentation at the 1969 Nuclear Science Symposium. (A. H. Sher and W. J. Keery)

Specimens of germanium doped with copper were prepared for lowtemperature impurity photoconductivity measurements so that data could be

obtained on crystals with known impurity concentrations before examining

crystals included in the germanium study (see Section 5). A liquid nitrogen cryostat with a germanium window has been constructed to study the

infrared response of germanium p-i-n diodes in order to determine if

correlations exist between the two infrared analytical techniques. A

suitable preamplifier for use with the cryostat is being constructed.

(W. R. Thurber and A. H. Sher)

Plans: Lithium mobility studies (including effects of surface type)

and detector performance measurements with emphasis on carrier trapping

utilizing a collimated gamma-ray beam and subsequent analysis of the peak

shape will be continued. Impurity photoconductivity measurements (see

Section 5) will be made on germanium crystals which show high degrees of

charge-trapping. Infrared response measurements at 77 K will be made on Ge(Li) detector structures fabricated from the same material.

20
METHODS OF MEASUREMENT FOR SEMICONDUCTOR PROCESS CONTROL

11. METALLIZATION EVALUATION

Objective : To improve methods for measuring the properties of thin

metal films with initial emphasis on adhesion of aluminum metallization

deposited on various substrates.

Progress: The literature search on thin film adhesion has indicated

that the scratch test appears to be the only adhesion test which is

presently capable of yielding quantitative and consistent data. The

scratch test basically consists of mechanically loading a spherically

tipped stylus, and then drawing it smoothly across a thin metal

film. The film adhesion force is proportional to the minimum loading on the stylus at which the film under the stylus is removed.

A simple scratch test apparatus has been assembled to perform

preliminary studies on this test method. Except that a dynamometer is

used both as the loading force generator and as the measuring device,

this apparatus is similar to the apparatus outlined in the draft method

for performing the scratch test which is now being developed by ASTM

Committee F-l.

In order to calculate the shear force required to remove a film from

its substrate when making a scratch test, it is necessary to know the

radius of curvature of the stylus tip. The shear stress is a sensitive

function of the tip radius, thereby making an accurate determination of

this quantity quite necessary. The tip radii of the diamond styli now being used are less than 25 ym. Shadowgraph techniques for determining

the radius of curvature were found to be inadequate. Instead, techniques

are being developed to determine the geometry of the tip from a series of

photomicrographs

An extensive listing of unclassified reports and abstracts related

to thin metallic films and adhesion, supplied by the Defense Documentation Center, is being searched for work relating to thin film adhesion

testing. (J. Oroshnik)

To permit operation of the substrate at higher temperatures during

evaporations carried out to prepare film samples, a platinum-bonded silicon sandwich temperature detector was constructed to replace the goldbonded unit previously described. During assembly, the unit cracked,

most probably due to the thermal expansion mismatch between the silicon

and platinum. It is believed that this can be remedied by using a con- siderably thinner platinum foil or by sputtering about 800 nm of plati- num on the silicon surfaces to be alloy-bonded. (W. K. Croll)

21
11. METALLIZATION EVALUATION

Plans : The literature search on thin film adhesion will continue.

Suitable optical systems will be considered for observing the scratches

produced with the adhesion test device. Since transmitted light is most

convenient for observing a scratch at the failure point, the initial

system which will use visible light will be suitable for aluminum films

deposited on transparent substrates. Later, a second system which will

use infrared light will be built for use with films deposited on silicon

dioxide substrates over silicon. Work will also continue on developing

a satisfactory method for determining the radius of curvature of the

stylus tip.

Consideration of the pull test as an alternative method for measuring adhesion strength will continue. A search will be made for a ce- ment suitable for bonding to aluminum dots . Modifications to the design

of the platinum-bonded silicon sandwich temperature sensor will be made,

and a new sensor will be constructed.

12. PROCESSING FACILITY

Objective : To establish a microelectronics fabrication laboratory

consisting of the facilities necessary for the production of specialized

silicon devices for use in research on measurement methods.

Progress : The photomasking facility was developed to the point that

12.5-um (0.5-mil) lines can be photoetched in either aluminum or silicon

dioxide. This resolution is sufficient for the devices currently needed

for wire bonding and other research studies. (J. Krawczyk)

The assembly of a pinhole camera was undertaken for the purpose of

making photomasks. Using very simple optical techniques, photomask sets

suitable for present requirements can be produced at relatively low cost

and with a very modest equipment investment.

A groove grinding device was designed and built which produces a polished cylindrical groove in the surface of the silicon wafer for measuring junction depths [l]. The grooving technique was found to be more

convenient and faster than the conventional angle lapping method [1].

Preliminary studies of various staining techniques for delineating junctions have been initiated. (T. Leedy)

A new heat-treating furnace and its associated control equipment was assembled and put into operation. This furnace, which has a working bore

1. B. McDonald and A. Goetzberger, "Measurement of the Depth of Diffused

Layers in Silicon by the Grooving Method," J. Eleotroohem. Soo.

109, 141-144 (1962).

22
12. PROCESSING FACILITY

of about 7.5 cm, will accommodate fifteen 2. 5- cm diameter wafers within

its flat zone. It has a maximum working temperature of 1010° C , provision for atmospheres of dry hydrogen, helium, or nitrogen, and allows

considerable flexibility in heat treating evaporated aluminum films.

(W. K. Croll and J. Krawczyk)

Several circuit analysis computer programs are being investigated to

determine their usefulness in establishing fabrication conditions for

devices which may be required for research on measurement methods. Since

the effects of variations of diffusion concentrations on gain and frequency response may be predicted, it is possible to test various fabrication parameters prior to actual construction of devices. Each of these

computer programs has its own advantages. SNAP-II [2] has the capability

of solving circuit problems in the frequency domain, and includes provisions for sensitivity testing and Monte Carlo analysis. ECAP [3] is

characterized by its ease of computer programming and its ability to

solve problems in either the frequency or time domain. CIRCUS [4] simulates the time domain response of an electronic circuit to an arbitrary

forcing function. (T. F. Leedy)

Plans : Mechanical work on the photomasking camera should be com- pleted by the end of the next quarter. Further studies of staining techniques for junction delineation will continue. The computer programs

will become operational on the NBS computer and further studies of their

applicability to the needs of the Program will be made.

13. WIRE BOND EVALUATION

Objective: To survey and evaluate methods for characterizing wire

bond systems in semiconductor devices and where necessary to improve

2. T. D. Price, C. M. Kimme , and J. R. Gliessman, "User's Manual for

SNAP-II Computer Program," Prepared for U. S. Naval Weapons Center,

China Lake, California, by ARINC Research Corporation, Western

Division, Santa Ana, California. Publication 474-01-1-909.

(Available from Naval Weapons Center.)

3. IBM Application Program, "1620 Electronic Circuit Analysis Program

(ECAP) (1620-EE-02X) User's Manual," (Available from either IBM,

Technical Publications Department, 112 East Post Road, White Plains,

N. Y. 10601 or UNIVAC Division of Sperry Rand Corporation, P. 0. Box

8100, Philadelphia, Pa. 19101.)

4. L. D. Milliman, W. A. Massena, and R. H. Dickhaut, "CIRCUS—A Digital

Computer Program for Transient Analysis of Electronic Circuits —User's

Guide," Prepared for U. S. Army Material Command, Harry Diamond Laboratories, Washington, D. C. 20438, by The Boeing Company, P. 0. Box

3999, Seattle, Washington, 98124, Publication 346-1.

23
13. WIRE BONO EVALUATION

existing methods or develop new methods in order to detect more reliably

those bonds which eventually will fail.

Progress : A new request, accompanied by a more detailed description

of project requirements, was sent to the Defense Documentation Center

(DDC) for a search of reports and work units for possible inclusion in

the bibliography. DDC used a two-level search strategy: only those

reports and work units were selected which were indexed in at least one category in each of the two levels. Level one contained the categories:

semiconductor devices, integrated circuits, and microelectronics. Level

two contained the categories: circuit interconnections, bonding, bonded

joints, and ultrasonic welding. A total of 41 work units and a report

bibliography containing 357 entries were received from DDC. About one- fourth of these work units and entries were found to be of interest. In

consultation with a DDC official it was concluded that the search con- ducted had collected all reports of interest within the limits imposed

by the indexing.

The survey of the journal literature continued. A patent search was conducted which found 44 patents of interest. A request for a bibliographic search was sent to the Reliability Analysis Center [1], A list

of 93 references (DDC reports, company reports, and journal papers) was received shortly before the end of the quarter.

(H. A. Schafft and E. C. Cohen)

The preparation of a detailed outline of the critical review survey

paper is in progress. (H. A. Schafft)

Work on the evaluation of aluminum ribbon wire has continued during

the quarter. New 1.5 by 0.5-mil wire which has the same cross section as 1-mil round wire was received from the vendor. This wire contained 1 percent silicon and had a nominal tensile strength of 14 g. It was obtained

from the same source as the round wire used in comparisons and both had

the same specifications except for dimensions. Experiments were made

using various bonding tools, ultrasonic power levels, and bonding pressures. The bonds were made to aluminum metallization evaporated on both

silicon and silicon oxide. It was found that the present ribbon wire

with 14-g tensile strength produces bonds with statistically similar pull

strengths to equivalent round wire. Under constant ultrasonic energy

conditions ribbon wire requires lower absolute bonding force than round

wire. In addition, this is distributed over a larger area. Hence, hard

wire (>24-g tensile strength), which would result in considerably greater

bond strengths, can be used without greater damage to the semiconductor

chip. Hard ribbon wire for such tests has been ordered.

1. Administered for the Department of Defense by the Rome Air Development Center, U. S. Air Force, and operated for that Center by the

IIT Research Institute, 10 West 35th Street, Chicago, Illinois 60610,

24
13. WIRE BONO EVALUATION

In addition the bonding operator finds ribbon wire more convenient

to use than round wire. Ribbon wire is easier to grasp with tweezers,

and there is less chance of damaging it in the process. The wire stays

centered under the bonding tool and accurate centering on a small pad is

easier and quicker. (K. 0. Leedy)

Near the end of the quarter, work was initiated on the effect of

metallization sintering temperature on bond strength. Sintering at temperatures ranging from 425 to 575°C is being investigated.

(W. K. Croll, K. 0. Leedy, and L. R. Williams)

Several methods of monitoring ultrasonic parameters during the bonding operation were investigated. The first method used a non-contacting

magnetic pickup placed near the tungsten carbide bonding tool. The tool

is weakly ferromagnetic since the tungsten carbide particles are cemented

with cobalt. The loading of the bonding tool results in decreasing tool

velocity or vibrational amplitude and hence an output signal that de- creases in amplitude during bond formation. Therefore, this method affords

some indication of bond quality. There was some inconvenience in using

this system while actually making a bond because the available shielded

polarized magnetic pickup coil was larger than desired. Further work

on this system has been postponed until a smaller coil can be obtained.

Another form of ultrasonic parameter monitoring was studied by

observing the 60-kHz voltage applied across the ultrasonic transducer

from a relatively high impedance source. The transducer which drives the

bonding tool was of the nickel magnetostrictive type having an acoustical

Q of about 100. The tool loading during bond formation results in lowered impedance of the transducer and a corresponding decrease in voltage

across the transducer. Thus the information on bond quality obtained by

this method is presumably similar to that which would be obtained with

the magnetic pickup system.

As a third approach, ceramic transducers were placed at various

points on the ultrasonic horn and on the tungsten carbide bonding tool

[2]. The bond monitoring information obtained from this system was similar to the other methods. The high- impedance transducer required electrostatic shielding to avoid stray pickup.

The final parameter monitoring experiment involved the use of a capacitor microphone to detect the ultrasonic pressure radiated from the

2. S. Bonis, "Poseidon Semiconductor Captive Line Process Development,"

Progress Report, 16 September 1968 to 15 November 1968, Report

R6 8-4566, Raytheon Company, Space and Information Systems Division,

Sudbury, Mass. 01776 (AD 844820L).

25
13. WIRE BOND EVALUATION bonding tool tip during bond formation [3]. Addition of a simple directional extension cone damped with silicon rubber and polytetrafluoroethylene to the microphone allowed sufficiently high resolution to detect

the sound pressure from a 0.5-mm diameter area located within 1 mm of

the bonding tool tip. A related experiment was performed by measuring

the ultrasonic vibration transmitted (from tool through wire into the

chip) from the substrate. Both procedures gave results that may be use- ful in bond monitoring, but were experimentally awkward because of the

physical size of the available ultrasonic microphone. However, this is

the only simple way that one can measure a known parameter, sound pressure, which is directly related to the bonding tip motion. The other

methods measure an indirect parameter or a vibration at some point remote

from the actual bonding operation. Therefore, despite its physical awkwardness , the capacitor microphone has been selected as the primary means

for studying the bonding process and for understanding the significance

of various other ultrasonic bond monitoring methods.

An additional method of studying the ultrasonic bonding tool motion

was considered. This consists of reflecting light, possibly a laser

beam, off the bonding tool or horn and observing the amplitude modulation. Commercial equipment exists that is capable of such measurements.

However, since the microphone method has sufficient resolution for the

purpose, the investment required to set up the optical system does not

appear to be warranted at the present time.

The objective of these ultrasonic bond monitoring studies was to

assemble equipment and survey various possible monitoring methods. No

statistical study of the resulting bonds has yet been made and no single

method has been chosen as being practical for in-process bond monitoring.

All of these methods gave the same qualitative results, although only the

microphone gave results in terms of known parameters. All methods give some information on the bonding tool loading as manifested by a change

in tip vibration amplitude due to deformation of the wire. Only a much

more intensive investigation can determine the relative sensitivity of

each method to subtle changes in bonding conditions. (H. K. Kessler)

In studying any physical system, in this case the ultrasonic bonding

system, it is necessary to characterize the important components in a way

that is meaningful to the end use. There is no consensus on such subjects

as the optimum impedance of the ultrasonic power supply (constant current

or constant voltage) or the effect of sweeping the ultrasonic drive frequency. To begin characterization of the power supply, resonance curves were made using a nickel magnetos trictive transducer including the

tapered horn and bonding tool. The ultrasonic sound pressure was measured directly in front of the bonding tool tip using the high-resolution

3. Neil Scott, Hughes Aircraft Company, Newport Beach, California 92663,

private communication.

26
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27
13. WIRE BOND EVALUATION extension cone on the microphone. This gave the entire system response

in the direction of the longitudinal axis of the horn. Measurements were made at both constant voltage and constant current as a function of frequency. The frequency was measured to within several hertz with a digital frequency meter. Sound pressure data were taken directly from the

tool tip with various bonding tool extensions as well as directly off

the end of the horn.

Typical resonance curves are shown in Fig. 2. The electrical Q of

the system as measured in the external circuit was about 130. It is

obvious from Fig. 2 that the acoustical Q is strongly dependent on the

impedance of the external driving circuit. Even a small-value resistor

inserted in series with the power supply will affect the acoustical Q

appreciably. The constant voltage (low impedance source) curve is very

sharp: Q - 270. For this case a driving source with extremely stable

frequency is required. In addition heavy loading of the bonding tool tip

could throw this system off resonance. The constant current curve (higher impedance source) has a lower Q (- 140) with a broad, almost flat,

top. Values of Q as low as 100 have been observed with slightly different power supply characteristics. It is apparent that constant current

drive would result in relatively constant ultrasonic tool motion even if

the source frequency drifted or a large load were applied to the bonding

tool.

The ultrasonic microphone was used to examine the displacement

amplitude of the bonding tool tip while the transducer was driven in the

swept-frequency mode with a relatively low Q system. The envelope of

the displacement amplitude for three values of the center frequency, f

Q

, is displayed in Fig. 3. The shape of the envelope can be changed significantly by relatively small changes in the center frequency. Thus, to

maintain reproducible bonding conditions, it is necessary both to have a stable oscillator and to exercise care in tuning the ultrasonic system

even when the swept-frequency mode is used.

While making the above measurements it was found that the maximum

tip vibration amplitude occurred at a different frequency from the transducer resonance as indicated by a current meter in series with the transducer coil. Thus, it is apparent from the swept-frequency oscillograms

and the acoustical resonance curves that regardless of the power supply

characteristics an ultrasonic microphone is almost essential for tuning

the ultrasonic system of a bonding machine.

In addition to the detailed resonance curve around the normal 60-kHz

operating frequency, the broad frequency response of the system was measured at the vibrating tool tip. There were from 13 to 18 other

resonances between 7 and 90 kHz. Different bonding tool extensions do

not appreciably effect the 60-kHz resonant frequency but many of the

other resonances are dependent on specific extension lengths.

28
IENHH

Fig. 3 Three oscillograms of the sound pressure from the tip of a bonding tool. These patterns result from sweeping the frequency of

the power supply by approximately 1200 Hz. The vertical axis is

proportional to bonding tool displacement. The horizontal axis

is time (1 ms/division) . The sweep period is about 4 ms

A: f

Q

= 60.50 kHz (manufacturer's specification).

B: f = 61.00 kHz (system was tuned to give maximum

ultrasonic output without sweeping).

C: f

Q

= 61.38 kHz (pattern least affected by slight

detuning of the center frequency).

29
13. WIRE BONO EVALUATION

It has been reported that the resonant nodes of bonding tools can be seen by sprinkling lycopodium dust over the tool [4]. Other powders, that

may be more readily available, have been found to perform the same function [5]. The powder-delineated nodes have been clearly observed by

using the ultrasonic microphone with its high-resolution extension tip.

With this system the resonant maxima can also be clearly observed. By

studying the amplitude of the sound pressure around the perimeter of the

bonding tool it is expected that torsional and other modes of vibration

can be observed. One common opinion is that varying the drive frequency

around the resonance (sweeping or wobbling) may excite such different

vibrational modes. (G. G. Harman)

There are many advantages to ball bonding as opposed to wedge bonding. The ball is commonly used with gold wire in thermocompression bonding and occasionally for ultrasonic stitch bonding. However, gold does

not easily bond ultrasonically . If an aluminum ball could be easily and

Teproducibly formed on 1-mil wire, then it should be possible to make

strong ultrasonic ball bonds. Because of oxide formation, aluminum does

not ball when flamed. In a feasibility experiment performed to make such

a ball a capacitor discharge across a spark gap supplied the necessary

heat to melt the aluminum wire, and dry nitrogen prevented oxide formation. A number of good aluminum balls were made. There was more variability in their diameter than would be desired for production use, but

the results were sufficiently good to warrant continued investigation.

(H. K. Kessler)

Plans: The collection of papers for the bibliography, the assignment of key words for each entry, and the indexes will be completed and

the typing of the manuscript will be under way by the end of the next

quarter. Work on the critical review paper will continue.

Investigation of the tensile strength of wire and wire bond systems

after burn- in at various temperatures will continue. In some cases devices will be operated for greatly extended periods in order to simulate

normal system operation. These tests will include wire obtained from

several different sources. Cross correlations will be made between the

optimum-angle pull strength, the loop height, and the length of normal

stitch bonds with the use of the hot-melt-glue bond puller. The work

on ribbon wire will resume when new, harder wire is received. The effect

of metallization sintering time and temperature on ultimate wire bond

strength will continue.

4. S. Bonis, "Poseidon Semiconductor Captive Line Process Development,"

Progress Report, 16 November 1968 to 15 March 1969, Report R69-4198,

Raytheon Company, Space and Information Systems Division, Sudbury,

Mass. 01776.

5. Such as Shell VPI #250, Shell Oil Company, New York, New York 10020,

30
13. WIRE BONO EVALUATION Several ultrasonic bond monitoring systems will be investigated in

greater detail with emphasis on the use of an ultrasonic microphone in an effort to obtain a fundamental understanding of such systems. Ultimately

the results will be compared with wire pull and "push" tests. A high- current pulse method for nondestructive wire bond testing will be in- vestigated and the feasibility study of aluminum wire ball formation will be concluded.

14. DIE ATTACHMENT EVALUATION

Objective : To evaluate methods for the detection of poor die

attachment in semiconductor devices with initial emphasis on the determination of the applicability of thermal measurements to this problem.

Progress: The literature search on the techniques utilized in

evaluating the uniformity and quality of semiconductor device die attachment was continued. This search is being carried out in conjunction with

the Wire Bond Evaluation search (see Section 13). An industrial organization concerned with both the manufacturing and utilization of semiconductor devices was visited to discuss the techniques used to detect poor

die attachment. The information gathered thus far indicates that not

only is a precise die bond evaluation technique needed but also a more repeatable technique for making die bonds themselves.

X-ray equipment capable of conveniently detecting voids in the die

attachment was installed and is operational. Radiographs can be made on

a variety of film types and sizes. (F. F. Oettinger)

Plans: The literature search on the techniques utilized in evaluating the uniformity and quality of semiconductor device die attachment

will continue. Radiographic studies of various chip and packaging con- figurations will be made to determine practical sizes and locations for

voids. Following these studies fabrication of test diodes with con- trolled voids will begin.

15. NASA MEASUREMENT METHODS

Objective : To review existing semiconductor test method standards

for materials and process control measurements and to prepare interim

test methods in a standard format as may be appropriate.

Progress: A draft of an interim method for measuring oxide and

metallization thickness has been completed and has been sent to the

NASA Electronics Research Center for review.

31
15. NASA MEASUREMENT METHODS

Responses were tabulated for the ASTM Committee F-l questionnaire

on use and adequacy of ASTM standards for microcircuit processing.

The tabulation has been sent to the ASTM Committee F-l Chairman and is

consistent with the preliminary conclusions reported previously (NBS

Tech. Note 475, p. 24). (W. E. Phillips)

A review of NASA test methods [1] was completed and sent to the NASA

Electronics Research Center.

Information on various leak testing methods currently in use or proposed by NASA, the military and other organizations was assembled and

presented to ASTM Committee F-l. The Committee will modify existing

tentative and draft methods as a result of this activity. (W. M. Bullis)

Plans: In connection with other tasks, procedures for determining

junction depth (see Section 12) and conductivity of thin metallic films

will be reviewed. Additional assistance will be given ASTM Committee F-l

in the development of standard procedures for leak testing.

"Test Standards for Microcircuits ," Draft of NASA-STD-XX-3, December

1, 1968.

32
METHODS OF MEASUREMENT FOR SEMICONDUCTOR DEVICES

16. SECOND BREAKDOWN

Objective: To maintain an awareness of progress in the field of

second breakdown and to assist both manufacturers and users of semiconductor junction devices in the development and use of meaningful specifications for maximum operating conditions free from second breakdown.

Progress : The first draft of the manuscript on "Failure Modes"

was completed and submitted to the task group of the JEDEC Committee on Power Transistors, JS-6, responsible for writing a chapter titled "Users

Guide for Power Transistors." This chapter is to be part of a JEDEC

suggested standard to be titled "Recommended Standards for Power Transistors ."

A definition for second breakdown was proposed to Committee JS-6

for possible use in "Recommended Standards for Power Transistors" and to

the technical adviser to the U. S. National Committee of IEC Technical

Committee No. 4-7 on Semiconductor Devices. (H. A. Schafft)

Plans: Assistance will be given to the JS-6 group in the revision

of the initial drafts of the chapter "Users Guide for Power Transistors"

The review of the status of the second breakdown field with particular emphasis on radiation-induced effects will begin after work on the

wire bond bibliography and survey is complete (see Section 13).

17. THERMAL PROPERTIES OF DEVICES

Objective : To evaluate and, if necessary, improve electrical meas- urement techniques for determining the thermal characteristics of semiconductor devices

Progress : The literature search and the review of the methods of

measurement of thermal resistance and transient thermal response of semiconductor devices were continued. Since thermal resistance alone, either

steady-state or transient, is inadequate for fully characterizing thermal

performance of semiconductor devices, the scope of the literature search

has been expanded to include articles on other semiconductor properties

which contain information of value in understanding thermal behavior.

(M. Sigman and F. F. Oettinger)

The circuit modifications that were made to reduce the switching

transients caused by the termination of the power pulse were only partially successful, but measurements can be made within 15 ys after the

33
17. THERMAL PROPERTIES OF DEVICES termination of the power pulse, which is sufficient for present studies.

It was also found that for temperatures above 50°C increasing the lowlevel metering current (from 0.5 to 1.0 mA for 25- and 35-W transistors)

did not appreciably change the slope of the calibration curve (forwardbiased base-emitter voltage, VRF , versus temperature).

Measured values of thermal resistance, Rq, and of d-c current gain,

hpp, were compared when they were plotted as functions of power dissipation for a given device. Abrupt changes in the curves for both types

of measurements were observed at corresponding operating points. An

example of such curves is shown in Fig. 4 for a power transistor rated

at 35-W maximum dissipation with the case held at 25°C. In making these

measurements the transistor under test was operated in a common- emitter

configuration with a variable constant- current source in the base. The

collector current was held constant by varying the base current as the

collector-emitter voltage was varied. The h FF was determined from the

ratio of collector to base current. Thermal resistance was measured

using VgE as the temperature indicator by interrupting the collector

voltage supply and simultaneously reducing the base drive to the re- quired low-level metering current.

In a further measurement made using thermographic phosphors to

detect hot-spot formation it was observed that hot spots developed at

operating conditions corresponding to those at the appearance of the

abrupt changes in Rq and h

FFj

.

The curves of h „ versus power illustrate the fact that until the

point of abrupt change is reached the increase in h fE is almost entirely

due to temperature effects for the type of interdigitated transistor

structure studied. Below the abrupt change, within the experimental

error of the procedures, all the curves are approximately coincident. At

a given abscissa the power dissipation, and hence the indicated temperature, is the same for all four curves although the voltages and currents

vary 'widely from curve to curve. The change in hF£ with increasing power

is therefore primarily a function of the temperature rather than of collector voltage or current. In the case of the 100- and 200-mA curves,

the increase in the slope of h

FE versus power which appears somewhat before the abrupt change could be evidence of charge carrier multiplication.

The plotted data also indicate the fact that the device is more sus- ceptible to lateral thermal instabilities at the high voltage-low cur- rent operating condition than at the high current- low voltage con- dition [1].

If the observed correlation between h FE and R

Q

exists for other

transistor types, the use of hF£ measurements may provide both the user

1. D. Navon and E. A. Miller, "Thermal Instability in Power Transistor

Structures," Solid-State Electronics 12, 69-78 (1969).

34
1601-

14

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100-

80

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10 12 14 16 POWER (W)18 20 22 24

Fig. 4 D-c current gain and thermal resistance versus power dissipation

for a 35-W silicon n-p-n transistor. All data points were within

the specified maximum operating areas for the device.

35
17. THERMAL PROPERTIES OF DEVICES

and supplier of devices with a more convenient screen for thermal instabilities than the difficult and lengthy measurement of Rq.

(S. Rubin, R. L. Gladhill, and F. F. Oettinger)

Plans: The literature search will continue. Writing of the review

paper on the methods for measurement of thermal resistance and transient

thermal response of semiconductor devices will begin.

Work will continue to determine the extent of the correlation between h and Rq as measured by the Vg£ technique on transistors with

different geometry and structure. The results obtained will be cor- related with thermographic studies of the uncased transistors (see

Section 18). The hpE test apparatus will be modified to provide automatic

control of the collector current by providing a servo- loop to control the

base drive so that the collector current will remain constant during the

voltage sweep. This will allow an investigation of the repeatibility of

the data for the same, and for differing, sweep speeds.

18. THERMOGRAPHIC MEASUREMENTS

Objective : To evaluate the utility of thermographic techniques for

detection of hot spots and measurement of temperature distribution in

semiconductor devices.

Progress : A photometric microscope has been substituted for the

camera for recording the light output of the thermographic phosphors.

The equipment has been used to obtain qualitative results which indicate

that temperature differences on transistor chips can be recorded. Quantitative results must await modification of the equipment to eliminate

all extraneous visible light from the microscope system.

(G. J. Rogers and F. F. Oettinger)

Plans : After modification of the photometric microscope system is

completed, the equipment will be used to record temperature distributions

on the surface of transistor chips. These results will be compared with

the results obtained by electrical measurements using hpp and VRF as temperature-sensitive parameters. Studies of the spatial resolution and

temperature resolution of the phosphors will be resumed.

19. MICROWAVE DIODE MEASUREMENTS

Objective : To study the problems and uncertainties associated with

measurement of microwave mixer diode properties and to improve the

methods of measurement for selected characteristics.

36
19. MICROWAVE 0I00E MEASUREMENTS

Progress : Technical activity on this task has been deferred until

the negotiations to determine the priority of specific problems to be

studied are complete. Discussions have been held with representatives

of the Electronic Industries Association, the Defense Electronic Supply

Center, the IEEE Microwave Theory and Technique Group, the Defense- Atomic

Support Agency, the Air Force Weapons Laboratory, the Naval Electronic

Systems Command, the Navy Applied Science Laboratory, the Air Force

Material Laboratory, the Air Force Avionics Laboratory, and others to

determine further the nature of the work which is to be undertaken in

this area. (R. C. Powell)

Plans : Negotiations will be continued. Detailed studies are ex- pected to begin late next quarter.

20. SILICON NUCLEAR RADIATION DETECTORS1

"

Objective : To conduct a program of research, development, and device evaluation in the field of silicon nuclear radiation detectors with

emphasis on the improvement of detector technology, and to provide con- sultation and specialized device fabrication services to the sponsor.

Progress : The chamber for the thermal cycling and life-testing of

detectors under space-simulated conditions has been assembled, baked out,

and evacuated to a pressure of approximately 10 -9 torr. Electrical

wiring and installation of the unit, which will provide thermal cycling

for the detectors between -20 and +50°C, remain to be completed. Equipment is being obtained for the system which will automatically monitor

the leakage current and noise of detectors while in storage under bias.

The principal problem anticipated with' this system is the excessive noise

from the elaborate switching network during the measurement of detector

noise. Circular, finger- type spring contacts were designed and made for

mounting Si(Li) detectors in the IMP-I radiation detector telescopes.

Assistance was 'provided to the sponsor with the testing and evaluation of

the detectors for the IMP-I telescopes.

The sensitive faces of two different types of 2-mm thick Si(Li)

detectors , each with double concentric grooves which define an annular

guard-ring detector surrounding the central circular detector, were

scanned with a 1-mm diameter beam of light from a pulsed GaAs lightemitting diode. The objective was to determine the amount of cross- talk

between the central detector and the annular detector. The response of

Supported by Goddard Space Flight Center, National Aeronautics and

Space Administration. (NBS Project 4254M-29) Irradiations were

carried out at Goddard Space Flight Center.

37
iu;

1

CP

U-l LUCO

1

2 i/V V

2

LLJ

U-l

/ V y

i i^i i i ^ i i .300 .200

SENSITIVE SURFACE EVAPORATED-Au

INCHES

.200 .300

CROSS-SECTION -H K" LIGHT BEAM DIAMETER

(b)

1

—

<J3 LU /' "*% rc _ / » LLJ 2 / 1 CO A / X ^ A ' n *

\

>'' /\

LU

/ \

'

1-X 11 1\l

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x

i .300 .200 .100 INCHES

.200 .300

• •>••• I Jl I I I I I I I I I I I I I I I I I I J I I I J III i I ll> III I I llll 2V-^ i v_y 2 DETECTOR CROSSSECTION

SENSITIVE SURFACE

EVAPORATED-Au

h- LIGHT BEAM DIAMETER

Fig. 5 Relative pulse height response of two Si (Li) detectors to a collimated beam from a pulsed GaAs light-emitting diode scanned

along the diameter of the sensitive surface. Each detector has

a central region (1) which is used to detect radiation incident

normal to the sensitive surface and an annular region (2) which

is used as an ant i- coincidence detector for radiation entering

from the side of the device. A large uniform response throughout

region (1) and a small response from each region at the transition

point is sought in these detectors.

38
20. SILICON NUCLEAR RAO I AT I ON DETECTORS

each region in terms of pulse height as a function of beam position along

a diameter is shown in Fig. 6. A cross-sectional view of each detector

(drawn to scale) is shown below each scan. The irregular response shown

in Fig. 6 (b) could be caused by a nonuniformity in the layer of metallization applied on the sensitive surface, incomplete depletion of the

silicon near the surface, or poor charge collection in the depletion

region due to inhomogeneities in the crystal.

Efforts on the study of the correlation of carrier lifetime in silicon with the characteristics of detectors made from the same material

have been concentrated in the area of diode recovery measurements of

carrier lifetime (see Section 3). (B. H. Audet)

As part of the continuing investigation of the effects of radiation

damage in silicon detectors by protons and electrons, a study has been

made of the response of two 1-mm thick silicon, surface-barrier, totally

depleted detectors to radiation damage by 1-MeV electrons, which have a range of 1.5 mm in silicon. A 20-mm2 spot on the barrier contact of one detector and on the ohmic contact of the other detector were irradiated

with fluences up to 10 15 electrons/cm2

.

After irradiation of the barrier contact with 3 * 10 13 electrons/cm2 the detector leakage current, capacitance, and noise increased sharply at

the normal operating voltage. Decreasing collection efficiency for alpha

particles incident on the barrier contact was observed with increasing

fluence. However, counting with alpha particles through the ohmic con- tact of this device was degraded only slightly for fluences up to 10 14

electrons/cm2

.

When the ohmic contact of the other device was irradiated with electrons, a slow increase in detector leakage current, capacitance, and noise

was observed with increasing fluence. The collection efficiency for

alpha particles incident on either contact was changed very little for

fluences to 10 15 electrons /cm2

. These results are similar to previous

observations in which the electrons did not penetrate through the entire

detector; radiation is more detrimental to surface-barrier detectors when

it is incident on the barrier contact. (Y. M. Liu and J. A. Coleman)

Plans: Establishment of the detector storage and monitoring system

and the high-vacuum test chamber facilities will continue. A study of

the noise contribution of the switching network will be emphasized.

Additional detectors for the IMP-I telescopes will be tested. Evaluation

of the resistivity, carrier lifetime, oxygen content, and lithium ion

mobility in a 50-mm diameter, dislocation-free silicon crystal will be

undertaken. Radiation damage by 400-keV electrons in surface-barrier detectors will be studied. The sensitivity of avalanche detectors to lowenergy (<10-keV) electrons will be evaluated.

39
Appendix A

JOINT PROGRAM STAFF

Coordinator: J. C. French

Consultant: C. P. Marsden

Semiconductor Characterization Section

Dr. W. M. Bullis, Chief

A. J. Baroody, Jr

D. L. Blackburn

F. H. Brewer

Mrs. E. C. Cohen"

M. Cosman

Dr. J. R. Ehrstein

R. L. Gladhill

G . G . Harman

F. R. Kelly§

H. K. Kessler

Mrs. K. 0. Leedy

Semiconductor Processing Section

R. L. Mattis

Dr. W. E. Phillips

Miss T. A. Poole"1"

Miss D. R. Ricks*

Dr. J. L. Scalest

H. A. Schafft

A. W. Stallings

G. N. Stenbakken

W. R. Thurber

Miss R. E. Young

+

Dr. J. A. Coleman, Chief

Miss D. A. Adamson§

B. H. Audet

H. A. Briscoe

R. D. Claytoni

W. K. Croll

R. T. Daltont

Mrs. S. A. Davis"1"

H. E. Dyson"

H. A. Gitelsoni

W. J. Keery

E. I. Klein

J. Krawczyk

T. F. Leedy

Y. M. Liu

J. Oroshnik

R. C. Schaevitzt

Dr. A. H. Sher

L. M. Smith

G. P. Spurlock

Miss E. D. Willisi

Mrs. C. F. Bolton

Mrs. R. Y. Cowan

Miss B. S. Hope+

F. F. Oettinger

M. K. Phillips

+

Electron Devices Section

J. C. French, Chief

R. C. PowellG. J. Rogers

S. Rubin

M. Sigman

L. R. Williams

- Part Time

t Guest Worker

§ Summer

+ Secretary

40
Appendix B

COMMITTEE ACTIVITIES

ASTM Committee F-l; Materials for Electron Devices and Microelectronics

F. H. Brewer, Task Force on Resistivity

W. M. Bullis , Editor, Subcommittee IV, Semiconductor Crystals

J. A. Coleman, Secretary, Subcommittee V, Semiconductor Processing

Materials

J. R. Ehrstein, Task Forces on Epitaxial Resistivity and Epitaxial

Thickness

J. C. French, Chairman, Subcommittee VIII, Editorial

T. F. Leedy, Task Force on Photomasking

J. Oroshnik, Task Forces on Thin Films, Thick Films, and Photomasking

W. E. Phillips, Task Forces on Crystal Perfection, Encapsulation,

Thin Films, and Thick Films

A. H. Sher, Task Force on Germanium

M. Sigman, Editor, Subcommittee V, Semiconductor Processing Materials

W. R. Thurber, Task Forces on Impurities in Semiconductors and Germanium

Electronic Industries Association:

MED 32, Active Digital Circuits: F. F. Oettinger, TG 32.5, Thermal

Resistance and Test Methods

MED 41, Physical Characterization Requirements: F. F. Oettinger,

TG 41.6, Thermal Considerations

Joint Electron Device Engineering Council (EIA-NEMA):

JS-3, UHF and Microwave Diodes: R. C. Powell, Microwave Diode

Specification Problems

JS-6, Power Transistors: H. A. Schafft, Consultant on Second

Breakdown Specifications

JS-9, Low Power Transistors: F. F. Oettinger, Thermal Resistance

Measurements

TS-14, Thyristors: F, F. Oettinger, Thermal Resistance of SCR's

IEEE:

Nuclear Science Group: J. A. Coleman; Administrative Committee;

Nuclear Instruments and Detectors Committee; Editorial Board,

Transactions on Nuclear Science; Chairman, 1970 Nuclear

Science Symposium

Magnetics Group: S. Rubin; Chairman, Galvanomagnetic Standards

Subcommittee

IEC TC47, Semiconductor Devices and Integrated Circuits:

F. F. Oettinger, U. S. Experts Advisory Committee

S. Rubin, Technical Expert, Galvanomagnetic Devices

NAS-NRC Semiconductor Detector Panel:

J. A. Coleman

41
Appendix C

SOLID-STATE TECHNOLOGY & FABRICATION SERVICES

Technical services in areas of competence are provided to other NBS

activities and other government agencies as they are requested. Usually

these are short-term, specialized services that cannot be obtained

through normal commercial channels. Such services provided during the

last quarter are listed below and indicate the kinds of technology available to the program.

1. Hall effect samples - (H. K. Kessler)

Ohmic contact dots were applied to epitaxial GaAs Hall effect samples for the Harry Diamond Laboratories

2. Radiation detectors - (B. H. Audet and A. H. Sher)

A 3-mm thick Al-p-Si surface-barrier silicon detector which

operated successfully at liquid helium temperature was made

for the Nuclear Spectroscopy Section. Assistance was provided to the Center for Radiation Research in developing and

testing special Ge(Li) gamma-ray detectors.

3. Quartz and glass fabrication - (E. I. Klein)

Various glass-to-metal seals were prepared for several

groups. A programmed annealing of special quartz specimens

was carried out for the Metrology Division.

42
Appendix D

JOINT PROGRAM PUBLICATIONS

Prior Reports :

"Methods of Measurement for Semiconductor Materials, Process Control, and Devices, Quarterly Report, July 1 to September 30, 196 8," NBS

Tech. Note 472, December, 1968.

"Methods of Measurement for Semiconductor Materials, Process Control, and Devices, Quarterly Report, October 1 to December 31, 1968,"

NBS Tech. Note 475, February, 1969.

"Methods of Measurement for Semiconductor Materials, Process Control, and Devices, Quarterly Report, January 1 to March 31, 1969," NBS

Tech. Note 488, July, 1969.

Current Publications :

A. H. Sher, "Lithium Ion Drift Mobility in Germanium" J. Appl. Phys. 40 , 2600-2607 (May, 1969).

G. G. Harman, "Topological Features of Hot-Carrier Induced Anisotropic

Breakdown on Silicon Diode Surfaces," J. Res. Natl. Bur. Standards^

73A S 321-331, (May-June, 1969).

+ W. M. Bullis and R. I. Scace, "Measurement Standards for Integrated

Circuit Processing," to appear in Proc. IEEE3 Special Issue on Materials

and Materials Problems in Microelectronics, September, 1969.

A. H. Sher and W. J. Keery, "Variation of the Effective Fano Factor in a Ge(Li) Detector," accepted for presentation at the Nuclear Science Symposium, San Francisco, October, 1969.

General Electric Company, Auburn, N. Y. 13021 (Chairman, ASTM Committee F-l. ) 43
THE NATIONAL ECONOMIC GOAL

Sustained maximum growth in a free market economy, without inflation,

under conditions of full employment

and equal opportunity

THE DEPARTMENT OF COMMERCE

The historic mission of the Department

is "to foster, promote and develop the

foreign and domestic commerce" of the United States. This has evolved, as a result of legislative and administrative

additions, to encompass broadly the re- sponsibility to foster, serve and promote

the nation's economic development and

technological advancement. The Department seeks to fulfill this mission through

these activities:

***$<*•*

MISSION AND

FUNCTIONS

OF THE

DEPARTMENT OF

COMMERCE

"to foster, serve and

promote the nation's

economic development

and technological

advancement"

Participating with other government

agencies in the

creation of national

policy, through the

President's Cabinet and its subdivisions.

• Cabinet Committee

on Economic Policy

• Urban Affairs Council

•Environmental

Quality Council

Promoting progressive business policies and

growth.

• Business and Defense Services

Administration

• Office of Field Services

Assisting states, communities and

individuals toward economic progress.

• Economic

Development

Administration

• Regional Planning

Commissions

• Office of Minority Business Enterprise

NOTE: This schematic is neither an organization chart nor a program outline for budget purposes. It is a general statement

of the Department's mission in relation to the national goal

of economic development.

JULY 1969

Strengthening

the international economic position

of the United

States.

• Bureau of International Commerce

• Office of Foreign

Commercial

Services

• Office of Foreign

Direct Investments

• United States

Travel Service

• Maritime

Administration

Assuring effective • use and growth of the

nation's scientific and technical resources.

• Environmental Science Services

Administration

• Patent Office

• National Bureau of Standards

• Office of Telecommunications

• Office of State

Technical Services

Acquiring, analyzing

and disseminating

information concern

ing the nation and

the economy to hel| achieve increased

social and economic

benefit.

• Bureau of the Census

• Office of Business Economics
1

NBS TECHNICAL PUBLICATIONS

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charts. Published in three sections, available separately: • Physics and Chemistry

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Technical Notes. This series consists of communications and reports (covering both other agency and

NBS-sponsored work) of limited or transitory interest. Federal Information Processing Standards Publications. This series is the official publication within

the Federal Government for information on standards

adopted and promulgated under the Public Law

89-306, and Bureau ot the Budget Circular A-86

entitled, Standardization of Data Elements and Codes

in Data Systems.

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The Clearinghouse for Federal Scientific and

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