NBS TECHNICAL NOTE

472

Methods of Measurement for Semiconductor

Materials, Process Control, and Devices

Quarterly Report

July 1 to September 30, 1968

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U.S. DEPARTMENT OF COMMERCE

National Bureau of Standards
NATIONAL BUREAU OF STANDARDS

The National Bureau of Standards1 was established by an act of Congress March 3, 1901. Today, in addition to serving as the Nation's central measurement laboratory,

the Bureau is a principal focal point in the Federal Government for assuring maximum application of the physical and engineering sciences to the advancement of technology in industry and commerce. To this end the Bureau conducts research and

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following areas of science and engineering

:

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UNITED STATES DEPARTMENT OF COMMERCE

C. R. Smith, Secretary

NATIONAL BUREAU OF STANDARDS • A. V. Astin, Director

NBS TECHNICAL NOTE 472

ISSUED DECEMBER 1968

Methods of Measurement for Semiconductor

Materials, Process Control, and Devices

Quarterly Report

July 1 to September 30, 1968

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. Naval Ammunition Depot

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 1

2. Resistivity 4

3. Carrier Lifetime 7

4. Inhomogeneities 9

5. Infrared Methods 11

6. Hall Effect 12

7. Deep Level Studies 14

8. High Field Effects 15

9

.

Specification of Germaniumt 16

10. Processing Facility 21

11. Wire Bond Evaluation 23

12. NASA Measurement Methods 24

13. Second Breakdown 25

14. Thermal Properties of Devices 26

15. Microwave Diode Measurements 28

16. Silicon Nuclear Radiation Detectorst 30

Appendix A. Joint Program Staff 31

Appendix B. Committee Activities 32

Appendix C. Solid State Technology and Fabrication Services .... 33

Appendix D. Electron Devices Data Service 34

Appendix E. Joint Program Publications 35

Appendix F. ASTM Standards Relevant to Integrated Circuit

Processing 36

t Related Projects

iii
ABSTRACT

This quarterly progress report describes NBS activities

relating to: measurement of resistivity, carrier lifetime,

inhomogeneities , and Hall effect in semiconductor crystals;

study of infrared measurement methods , properties of deeplying impurities (in InSb), and high field effects; establishment of a processing facility; evaluation of wire bonds; re- view of NASA measurement methods; and measurement of second

breakdown in transistors, thermal properties of devices, and

noise in microwave diodes. Projects on silicon nuclear radiation detectors and specification of germanium are also described. Supplementary data concerning staff, committee

activities, technical and information services, and publications

are included as appendixes. A list of ASTM Standards relevant

to integrated circuit processing is also included.

Key Words: carrier lifetime; electrical properties; germanium;

methods of measurement; microelectronics; resistivity; semiconductor devices; semiconductor materials; semiconductor process control; silicon; thermal properties; wire bonds.

IV
METHODS OF MEASUREMENT FOR

SEMICONDUCTOR MATERIALS, PROCESS CONTROL, AND DEVICES

Quarterly Report

July 1 to September 30, 1968

1. INTRODUCTION

Through long contact with the semiconductor industry, the Electronic

Technology Division of the National Bureau of Standards has gathered

substantial evidence of the need for improved measurement methods and

standards for semiconductor materials characterization, for process con- trol, and for device characterization. These methods and standards are needed for satisfactory buyer-seller exchanges , for economy in government purchasing, and for improved product uniformity, interchangeability

,

and reliability. The need is recognized both by industry and by government. NBS as a national center for measurement development, without

vendor or user bias, and already competent in the field, has repeatedly

been singled out as the uniquely appropriate organization to provide

assistance in the resolution of these problems.

NBS has therefore undertaken and partially funded a Joint Program on Methods of Measurement for Semiconductor Materials, Process Control,

and Devices. Added financial support has been supplied by concerned

government agencies. The Program includes extensive participation in

and cooperation from industrial standards organizations. It is cooperative in nature because:

(1) guidance is required in establishing priorities for the work

of the Program, and

(2) close contact must be maintained with the prospective

users of the methods and standards in both industry and

government in order to insure that the methods under

development are useful and will be accepted and applied.

Objectives of the Joint Program are enhancement of 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 , such as uniformity of

response to radiation effects.

These objectives are being approached through:

(1) evaluation of the technical adequacy of relevant measurement methods developed in industrial or other agency

organizations and recommendation of modifications to
these methods where such modifications are appropriate,

(2) development of specific methods selected in accordance

with the guidance received from participating groups,

(3) assistance to standardizing groups in industry and

government agencies as is appropriate to encourage the

rapid development, publication, and implementation of

improved measurement method standards , and

(4) consultation with sponsors, other government agencies,

manufacturers , and users regarding measurement requirements and applications.

The concepts and methodology of the Joint Program have evolved from

several projects that have been carried out in the Division during the

past several years. In these projects it was clearly established that

one of the key elements in the development of realistic, useful standards is cooperation and liaison with both manufacturers and users. This

is accomplished through participation in technical committee activities

of organizations such as the American Society for Testing and Materials

(ASTM) and the Electronic Industries Association (EIA) and through

personal contacts with and visits to industrial plants and government

laboratories. These contacts also serve to provide Program staff members

with a broader view of the problems faced by industry and help to insure

that the output of the Program will be useable in the field.

It was also established that there is a critical need for analysis

and review of existing measurement methods. Hence, one of the first

activities undertaken in connection with the detailed study of a measurement is the collection and collation of available information con- cerning both commonly used and alternate methods for making this measurement, evidence of the relevance of the measurement to device characteristics, and the level of precision required. In addition to providing a foundation for future experimental work, published bibliographies

and summary review papers which result from this activity are often

widely distributed and prove to be extremely valuable to both sponsors

and industry.

The Joint Program was established formally during the latter part of

fiscal year 1968 with support from NBS Cl] , the National Aeronautics and

Space Administration [2], and the Defense Atomic Support Agency [3].

During the present quarter, the U. S. Naval Ammunition Depot at Crane,

Indiana, also began support of the Program [4]. The concern of certain

sponsors with specific parts of the Program is taken into consideration

in program planning. It should be emphasized, however, that all sponsors

subscribe to the need for the entire basic program for improvement of

measurement methods for semiconductor materials, process control, and

devices

.

A number of tasks have been identified as parts of the Program.

These tasks were selected during an initial program review in April 1968.

Some are continuations of projects already in progress; others have been

started since the inception of the Program; still others are for future

implementation. Because of the cooperative nature of the Program, there

2
is not a one-to-one correspondence between these tasks and the projects

by which the Program is supported.

Quarterly progress reports for the Program will be subdivided

according to these tasks. Sections 2 through 9 deal with methods of

measurement for materials; sections 10 through 12, with methods of meas- urement for process control; and sections 13 through 16, with methods of

measurement for devices. In this first report, which covers the period

July through September 1968, objectives and background information are included together with a report of activity during the reporting period

and an indication of the direction the work will take during the next

reporting period. In addition to tasks sponsored under the Joint Program, this report contains descriptions of activity in 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 RTS (Research and Technical Services) Projects 4251120,

4251123, 4251126, 4252128, 4254111, 4254112, and 4254115.

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

4259523)

3. Through Inter Agency Cost Reimbursement Order 814-68. (NBS Project

4259522)

4. Through Cost Reimbursement Order P09-0016. (NBS Project 4259533)
2. RESISTIVITY

Objective: To develop improved methods, suitable for use throughout the electronics industry, for measuring resistivity of bulk, epitaxial, and diffused silicon wafers.

Background : Resistivity is the most widely used parameter in the

exchange of silicon across the interface between crystal grower and device manufacturer as well as in the design and production control of

semiconductor devices. This parameter is important because of its relation to the density of free carriers in semiconducting materials and because of the fact that the electrical characteristics of semiconductor

devices depend in a critical way on the free carrier density in the

various regions of the device structure.

In 1960, NBS was asked by ASTM Committee F-l on Materials for

Electron Devices and Microelectronics to investigate the problems asso- ciated with the measurement of resistivity of bulk silicon wafers. This

work [l] led to the formulation of a standard method for measuring re- sistivity of silicon slices by a four-probe method which was developed

in cooperation with Committee F-l [2]. With the use of this method it is now possible to make the measurement with a precision of ±2 per cent [3]

in the resistivity range between 0.005 and 120 fi-cm.

Although this represented a substantial increase in the quality in

the measurement there remains considerable need to extend the range of

applicability of the method to both higher and lower resistivities of

bulk wafers as well as to resistivity measurements on specialized structures such as epitaxial and diffused layers. The present phase of the

project is concerned with these extensions. In addition the expanded

scope includes other methods for making resistivity measurements on epitaxial and diffused layers.

Accomplishments during reporting period : A round-robin experiment

based on the standard four-probe method is being conducted in cooperation

with Committee F-l to determine the precision which can be expected when

measuring bulk silicon wafer resistivity as low as 0.001 fi-cm and as high

as 1000 fl-cm. Preliminary returns indicate that the resistivity range

can be extended with no loss in precision. (F. H. Brewer)

A series of experiments designed to determine the effect of variation in measuring current, probe force, specimen surface condition, and

sheet resistance on the measurement of resistivity by the standard fourprobe method has been started. These factors are most significant when

four-probe measurements are made on epitaxial and diffused layers. Initial measurements, concerned with variations of measuring current, were

made on bulk silicon wafers previously used in round-robin experiments.

(F. H. Brewer and W. M. Bullis)
Initial measurements were made on bulk silicon wafers in order to

obtain a better understanding of the various parameters which significantly influence the measurement of resistivity of epitaxial layers by

the three-probe voltage breakdown method.

A number of observations were noted. A distinct breakdown voltage

could be observed on many specimens only after the contact had been

electrically formed properly. Usually, forming required that currents in excess of the breakdown current be passed through this contact for a period of time. Once a contact was properly formed, a repeatable breakdown curve could be obtained regardless of the time interval between any

successive readings. It did not appear to be neccessary to form n-type

specimens to the same extent as p-type specimens

.

Preliminary results indicated that surface preparation and cleaning

did not significantly affect the value of the breakdown voltage; however,

large variations were observed in breakdown current. Studies of the

effect of various duty cycles were also initiated. Tentative indications

were that less forming time is needed to reach a stable breakdown if the

width of the voltage pulse is reduced. (J. R. Ehrstein)

Plans for next quarter: It is hoped that all participants in the

round-robin experiment will have completed their measurements and that

the analysis will be started. Experimental work on the effects of varying measuring current and probe force will be continued.

The dependence of voltage breakdown on the duty cycle used will be

studied in order that the type of generating equipment to be used for

further work can be determined. The dependence of voltage breakdown on

the forming process will be investigated further in order to determine

what forming, if any, gives the most reproducible resistivity measurements .

The results of this project are summarized in a report prepared

for the NASA Electronics Research Center, sponsors of the con- cluding phase: W. Murray Bullis , "Standard Measurements of the

Resistivity of Silicon by the Four-Probe Method," NASA-CR-86032,

N68-18067, December 29, 1967.

"Method of Test for Resistivity of Silicon Slices Using Four

Pointed Probes" (ASTM Designation: F84-68T), 1968 Book of ASTM

Standards3 Part 8, November, 1968.

This precision figure is three times the average relative sam- ple standard deviation obtained in a recent round-robin experiment involving 5 laboratories and 8 specimens

.
Fig. 1 Test Set-up for Precision Measurements of Resistivity of Sili- con Wafers by the Four-Probe Method.
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.

Background : Minority carrier lifetime is a basic parameter for the

specification of semiconducting materials for transistors, diodes, and

similar devices. Photoconductive decay measurements are made routinely

on many crystals used in the fabrication of these devices. Although this

measurement suffers both from lack of precision and from limitations in

the range of applicability, it is the only method for determination of

carrier lifetime which has been accepted as standard [1, 2], In the

initial phase of this project [3] begun in December 1966, preliminary but

detailed studies of the photoconductive decay method were accompanied by

the establishment of facilities for making measurements by the photomagnetoelectric method, the diode recovery time method, and the surface

photovoltage method [M-]. In addition, a critical survey of the various

methods used to measure carrier lifetime reported in the literature was compiled and an annotated bibliography was prepared [5], At the present

time, work on the four methods for making lifetime measurements is con- tinuing.

Accomplishments during reporting period : Detailed studies of the

photoconductive decay method were continued. The principal efforts were concerned with the determination of bulk lifetime from a measured value

of filament lifetime in rectangular silicon bars. Measurements were

made on a bar sample whose size was successively reduced. Bulk lifetime

was calculated from the filament lifetime by means of a formula which

assumes an infinite value of surface recombination velocity. In order

to obtain a consistent value of bulk lifetime- it was necessary to assume

a mobility for the minority carrier which was substantially larger than

that which is normally obtained. The reason for this discrepancy is not

yet understood. A cryostat was set up in order to enable measurements of

photoconductive decay lifetime to be made over the temperature range between 77 and 350 K. An initial study of the dependence of lifetime on temperature in the range -10 to 50°C showed that variations from 1 to 5 per cent per degree could be expected. (R. L. Mattis)

Increased emphasis was placed on the measurement of carrier lifetime

by diode recovery methods . The instrumentation was modified to permit

greater flexibility in measuring current plateau and current decay

characteristics . In addition new circuitry to enable voltage decay observations to be made was constructed and is being tested.

(A. J. Baroody)
The vacuum chamber and specimen holder of the steady-state photomagnetoelectric-photoconductive (PME-PC) equipment have been modified to

permit lower temperatures to be achieved. Serious difficulties have been

encountered in using this equipment on silicon wafers. Since minoritycarrier diffusion length can be measured directly by the surface photovoltage technique, the emphasis on PME-PC measurements for silicon is no longer necessary. The equipment, however, is being used in connection

with the study of deep-lying impurity levels in indium antimonide (see

Section 7). (W. E. Phillips and A. W. Stallings)

Plans for next quarter : The discrepancy in the bulk lifetime calculations from photoconductive decay filament lifetime measurements will be

further investigated. Work on lifetime interpretation for various re- combination models will be emphasized. PME-PC measurements on indium

antimonide will be completed. Diode recovery lifetime measurements will

be made on several types of diodes including lithium-drifted p-i-n

devices

.

1. "Method for Measuring the Minority-Carrier Lifetime in Bulk

Germanium and Silicon" (ASTM Designation: F28-66), 1968 Book of

ASTM Standards 3 Part 8, November 1968.

2. "Measurement of Minority-Carrier Lifetime in Germanium and Silicon

by the Method of Photoconductive Decay" (IEEE Standard 225), Proa.

IRE, 49„ 1292-1299 (1961).

3. Supported by U. S. Air Force Materials Laboratory under Delivery

Order F 33615-67-M-5007

.

4. R. L. Mattis, W. E. Phillips, and W. M. Bullis , "Measurement and

Interpretation of Carrier Lifetime in Silicon and Germanium,"

AFML-TR-68-81, July 1968.

5. W. M. Bullis, "Measurement of Carrier Lifetime in Semiconductors

An Annotated Bibliography Covering the Period 1949-1967," NBS

Tech. Note 465, June 1968.
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

.

Background: Variations in the resistivity- of a silicon wafer can cause significant variations in device characteristics. This problem is

aggravated in large scale integrated circuits and large area power devices where the resulting nonuniform current distributions can be unno- ticed until they cause device failure during operation. Although it is

possible to measure resistivity variations by means of a point-to-point

measurement with conventional four-probe or spreading resistance techniques, a scanning technique is more suitable in a large number of applications because it does not require the placement of probes on the re- gion of interest. Hence a photovoltaic method for measuring resistivity

variations which was introduced by Oroshnik and Many [l] was selected

for detailed study.

In the first phase of this project [2] which was begun in November

1966 it was demonstrated that it was feasible to use this method to obtain not only precise measurements of resistivity profiles along germanium and silicon bar-shaped specimens but also qualitative profiles on curcular wafers [3]. As another part of this phase of the project a comprehensive bibliography on methods for the measurement of resistivity

variations and other inhomogeneities in semiconductors was assembled and

published [4]. The present phase of the project is directed toward further refinement in the procedures for making the photovoltaic measurement, extension of the method to include quantitive measurements on circular wafers , and improvement in the means of recording experimental

data and computing the resistivity profile.

Accomplishments during reporting period : The causes for occasional

nonreproducibility observed in earlier photovoltaic resistivity measurements on rectangular bars of germanium and silicon were investigated in

detail. It was found necessary to: (l) replace the tungsten lamp

used as the light source for the light probe prior to the time when

significant but sporadic variations in the light output occur; (2) improve the light and air shields to reduce exposure of the specimen to

scattered light and air currents; (3) use a thermal shunt across the

specimen to minimize thermal gradients while, at the same time, keep the

electrical capacitance in parallel with the specimen small so the time

required for measurement is not increased; and (4) make measurements on specimens with non-specular surfaces. Tests were also made to insure

that the light probe did not introduce any significant thermal gradients

within the specimen and that the range of light intensities used in the

experiment injected a density of carriers which was much less than the

equilibrium concentration of majority carriers in the specimen. The

latter condition must be met if small-signal theory is to be used in the

analysis of the measurements. (H. A. Schafft and D. L. Blackburn)
Plans for next quarter : Further improvements of the measurement

techniques will be investigated* The information obtained will be

applied in measurements on p-type germanium and n- and p-type silicon bar

specimens. In preparation for quantitative measurements on circular

wafers , preliminary measurements will be started on rectangular-shaped

specimens where the light probe will not extend completely across the

width of the specimen.

1. J. Oroshnik and A. Many, "Quantitative Photovoltaic Evaluation

of the Resistivity Homogeneity of Germanium Single Crystals,"

Solid-State Electronics, 1, 46-53, (1960).

2. Supported by Rome Air Development Center under Contract F 30602-

67-C-0105.

3. H. A. Schafft, "Photovoltaic Method for the Measurement of Resistivity [Profiles] in Germanium and Silicon," RADC-TR-68-64 , June

1968.

4. H. A. Schafft and S. G. Needham, "A Bibliography on Methods for

the Measurement of Inhomogeneities in Semiconductors (1953-1967),"

NBS Tech. Note 445, May 1968.

10
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 germanium and silicon.

Background: An increase in the conductivity of a specimen occurs when radiation incident on the specimen is of sufficient energy to ionize impurity atoms with energy states located in the forbidden gap.

From measurements of impurity photoconductivity as a function of wavelength in the appropriate region it is possible to identify energy levels

associated with the impurities in the specimen. This project was established this quarter in order to determine whether the photo-ionization

of impurities at densities as low as 10 13 atoms/cm 3 can be detected and

whether the density of impurity atoms can be determined.

Accomplishments this reporting period: A monochrometer system

which covers the wavelength range between 2 and 6.4 ym by means of interchangeable gratings was set up. The lock-in amplifier and x-y recorder

which will be used to detect and record the signal were also set up.

(W. R. Thurber)

Plans for next quarter: A liquid helium cryostat will be designed

and fabricated. In addition the wavelength drive of the monochrometer

will be modified so that it also drives the x axis of the x-y recorder.

Additional gratings to extend the wavelength range to 40 ym will be

obtained. Preliminary measurements on germanium specimens will be

initiated when the equipment is assembled.

11
6. HALL EFFECT

Objective : To establish a facility for making measurements of Hall

coefficient as a function of temperature in the range between M-.2 and

350 K and to improve methods for collecting and interpreting Hall effect

data with automatic data acquisition systems.

Background : Measurements of the Hall effect are widely used in the

the study of semiconducting materials. During the past year, a cooperative program carried out with the NBS Computer Center demonstrated the

feasibility of using a time-shared computer system in conjunction with

the Hall effect experiment [1]. Recently a new commercial data acquisition system was purchased and is being installed.

Assistance has been given to ASTM Committee F-l in the formulation

of a standard method for making Hall effect measurements on semiconductor

crystals [2], Additional assistance is being given the committee in

conjunction with the interpretation of Hall effect measurements.

Accomplishments during reporting period: Circuitry to reverse and

turn on and off both the magnetic field and the specimen current at the

required time during the data-taking cycle was developed for the new Hall effect data acquisition system. A test run with a previously

measured specimen confirmed that the circuits functioned properly. Programs were developed to process the punched card output on the NBS com- puter. A circuit with 48 potentiometers and a 48-position stepping

switch was designed to permit automatic control of specimen temperature

by this system.

Information concerning the relationship between Hall coefficient

and carrier concentration in extrinsic semiconductors is being assembled

for publication in conjunction with the activities of the Optoelectronics

Task Force of ASTM Committee F-l. The materials of interest are germanium, silicon, gallium arsenide, and indium antimonide,

(W. R. Thurber, J. L. Scales, and W. M. Bullis)

Plans for Quarter : The temperature control system for the Hall

effect experiment will be built and tested. Programs will be written

to enable the data to be plotted by computer. Work on the relationship

between Hall coefficient and carrier concentration will be continued with

emphasis on gallium arsenide. The report describing the coupling between

the Hall experiment and the time-shared computer system will be written

in cooperation with Computer Center personnel.

W. M. Bullis, A. L. Koenig, T. N. Pyke^ Jr., W. R. Thurber, and

F. H. Ulmer, "Use of a Time-Shared Computer System to Control a Hall Effect Experiment," NBS Tech. Note (in preparation).

"Method for Measuring Hall Mobility in Extrinsic Semiconductor

Single Crystals" (ASTM Designation: F76-68), 1968 Book of ASTM

Standards3 Part 8, November 1968.

12
Fig. 2. Computer- controlled System for Hall Measurements in the Temperature Range Between 4.2 and 350 K.

13
7. DEEP-LEVEL STUDIES

Objective: To attempt to determine the origin of the deep-lying

impurity centers in high-resistivity indium antimonide.

Background : A number of investigators have found that high resistivity indium antimonide contains approximately 10 li+ unidentified deeplying impurity centers per cubic centimeter. Several models have been

proposed to explain the properties of high-resistivity indium antimonide

and hence considerable confusion exists in the literature concerning the

nature of these centers . Prior to this quarter a number of models had

been analyzed, some new Hall effect data had been taken, and initial

lifetime measurements had been made.

Progress during reporting period: Experiments were undertaken to

determine the interaction of lithium with the deep-lying impurity centers. Lithium was vacuum-deposited on the wafer surface after which the

wafer was sealed in an argon- filled ampoule and heated for 5 hours at

250°C, in order to diffuse the lithium in the wafer. Preliminary re- sults have shown that p-type wafers convert to n-type immediately after

"the lithium diffusion. However precipitation occurs and continues for

several days at room temperature so eventually the wafers recover their

p-type character. Hall measurements indicate that the wafer was more ptype after precipitation than it was initially. Hence the lithium seemed

to act in two ways: in large quantities it was a simple donor impurity

(probably an interstitial) but in small quantities it neutralized re- sidual donors that were already present in the material. This neutralization made the diffused material more p-type than the original material.

(J. L. Scales)

Plans for next quarter : Lithium will be diffused into other p-type

wafers . Photomagnetoelectric effect measurements will be resumed on com- pletion of the modifications of the cryostat (see Section 3) so that

additional lifetime data can be obtained. Further work will be done on the analysis of various models. In addition, various phases of the

investigation will be written up.

14
8. HIGH FIELD EFFECTS

Objective: To study the physical characteristics of hot-carrier

semiconductor structures and relate these to performance of devices.

Background: Anisotropic tracking effects have been observed in

silicon structures under high field and high current conditions as part

of a general investigation into the hot minority carrier transport problem. In addition oscillations have been observed during portions of the

current and voltage pulses

.

Progress during reporting period : The high voltage pulser and cryostat mounts were significantly improved to clean up the pulse shapes so that the current and voltage waveforms could be observed unambiguously.

Conductivity data were taken on 8 specimens at 300 and 77 K. Conduction

anisotropy was exhibited clearly by a very low carrier transport in junction specimens having an orientation of 20° from a <100> direction on a {lOO} surface.

Oscillations were observed in the current pulse at 77 K in samples

with the current direction oriented 20 to 25° from a <100> direction on

a {lOO} surface. These oscillations reached a maximum on 22° specimens

(approximately 10 per cent efficiency) with a frequency of about 2 MHz.

Specimens oriented 20 and 25° from a <100> direction also oscillate but

with higher frequency (up to 30 MHz) and lower efficiency (1 to 2 per

cent). A magnetic flux density of about 15 mT (150 gauss) lowers the

current threshold for oscillation. The reasons for this are not yet

understood. (G. G. Harman and K. 0. Leedy)

Plans for next quarter: Investigations will be made on additional

silicon specimens with various orientations, length, and conductivity

type.

15
9. 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

.

Background : For a number of years , uncontrolled variations in the

quality of germanium intended for fabrication into gamma-ray detectors

have occurred for reasons which, even now, are not understood. Crystals

are presently selected on the basis of room temperature resistivity,

photoconductive decay lifetime, and etch-pit density. Use of these

parameters does not always enable one to discriminate between crystals

suitable for detector fabrication and crystals which are not. This project, which was begun early in 1967, involves material evaluation, device

fabrication, and device characterization utilizing "good" and "bad" crystals [1]. To protect the sources of bad crystals, a code number has

been assigned to each crystal used in the study.

Progress during reporting period : Values of lithium mobility were obtained for samples NBS-13, -617, and -83 at 23.8, 36.2, and 46.2°C.

Additional samples of NBS-13 were also run at 61.2°C. The mobility

values obtained for these samples were consistently higher than predicted

by the extrapolation of the curve of diffusion constant against reciprocal absolute temperature derived by Fuller and Severiens [2], A description of this aspect of the mobility results is being prepared for publication in the immediate future.

A preliminary effort was made to observe the effect of surface con- dition of the drifting diode on the capacitance against time measurements

used in determining lithium drift mobility. An apparatus was assembled

which permitted enveloping the drifting diode in various gaseous mixtures, e.g., nitrogen and water vapor, nitrogen and alcohol vapor, etc.

Preliminary analysis of results indicated that such treatment does affect

the capacitance measurement; however, the surface effects noted were not

identical to the effects observed in diodes after long lithium drift

times

.

Additionally, the method of Pell [3] for determining lithium mobility in silicon at very short drift times (<2 hours) from the slope of the

1/C 3 (where C is the capacitance) against time curve was studied for

use on germanium. Preliminary results indicate that this method is in

agreement with the method which uses the slope of the 1/C^ against time

curve for long drift times on certain types of samples. It also appears

to be easier to obtain a unique value of mobility from the slope of 1/C 3 against time curves than from the slope of 1/C plots

.

(R. D. Clayton, W.'J. Keery, and A.' H. Sher)

16
JO

TEMPERATURE (°c)

61 46 36 24

107 (K-1 )

Fig. 3 Diffusion Constant of Lithium in Germanium Derived from Measurements of Lithium Mobility. (Dashed curve is taken from Reference 2).

17
A study was undertaken to determine the possibility of using a copper staining technique on germanium to develop "coring" patterns as had

been observed when copper was electroplated on silicon. The germanium

crystal was immersed in a specially constructed ice bath and staining

with copper sulfate solutions of various concentrations containing various amounts of hydrofluoric acid. Infrared illumination was used (with

and without extra filters of etched germanium slices) at varying times of

exposure. However, no reproducible results regarding the copper stain

patterns on a lapped germanium slice were noted. This project has been

temporarily suspended. (H. E. Dyson and A. H. Sher)

Lithium precipitation measurements have been completed for samples

NBS-01, -11, -61, -64, -65, -66, -610, -612, and -91. Oxygen concentrations of 9.5 x 10 11+ and 8 x 10 11+ atoms/cm3 were determined in samples

NBS-01 and -91, respectively. The data on the other samples are being

evaluated.

An improved procedure for evaporating lithium metal was developed.

The main innovation was in the use of a thermocouple to monitor the source boat to yield a more precise indication of the beginning and end

of the evaporation. Thicker, more uniform, and more reproducible deposits of lithium have resulted from this improvement. (W. K. Croll)

Electron drift mobility measurements were made on samples NBS-01,

-13, and -63 at room temperature and 77 K. Samples NBS-01 which contains

approximately 1.5 x 10 15 oxygen atoms /cm 3 as determined by infrared absorption and lithium precipitation showed a normal electron drift mobility at 77 K but low lithium drift mobility.

Absorption of infrared radiation in the 11.7 um region was measured

on sample NBS-91 and an oxygen concentration of 9.9 x 10 14 atoms/cm3 was determined. Lithium precipitation and lithium mobility measurements on this sample yielded oxygen concentrations of 8 x 10 ^ and 9 x 10^

atoms / cm 3

, respectively. (W. R. Thurber)

A 1.4 cm 3 Ge(Li) detector was fabricated from a test slice of crystal NBS-83. The characteristics of this detector at 77 K were determined and the results were compared with test criteria selected previously (see Table 9.1). The measured characteristics of this detector will

serve as a reference against which the performance of detectors fabricated from other material under evaluation may be measured.

The analysis of gamma-ray peak shapes from Ge(Li) detectors to obtain information on carrier trapping has begun. The approach taken is to

treat the non-gaussian peak shapes, those which indicate trapping, as complex peaks. Initially, this treatment was applied to gamma-ray peak

shapes obtained from the total irradiation of a Ge(Li) detector. Eventually, spectra obtained from collimated-beam irradiation will be treated. (A. H. Sher and W. J. Keery)

18
Table 9.1 Detector Characteristics at 77 K

Parameter

Breakdown voltage

Leakage current at breakdown

Gamma-ray resolution

Total system, @ 122 keV

Detector, @ 1333 keV

Peak shape:

(FW.1M/FWHM) system

Capacitance vs Voltage:

dc

Criterion

>_ 500 V

<_ 5nA

<_ 3 keV FWHM

< 3 keV FWHM

< 2.12

(b)

NBS-83

> 1000 V

<_ 3nA @ 1000 V

2.7 keV FWHM

1.8 keV FWHM

2.0 @ 122 keV

2.1 @ 1333 keV

(a)

dV

for V > 100 V < 5%

(a)

(b)

Actual breakdown voltage not measured

(FW.1M/FWHM) for a gaussian peak + 16%

19
Plans for next quarter: Hall effect measurements, infrared absorption studies, impurity photoconductivity measurements, 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. It is also anticipated that a report on the use of lithium mobility, lithium precipitation, and infrared absorption for measuring oxygen

concentration in germanium will be prepared for publication.

Supported by the Division of Biology and Medicine, Atomic Energy

Commission. (NBS Project 4259425)

W. M. Bullis and J. A. Coleman, "Characterization of Ge and Si

for Nuclear Radiation Detectors," Euc'leon'ios 'in Aerospaces P.

Polishuk, Ed. (Plenum Press, New York, 1968) pp. 166-175.

C. S. Fuller and J. C. Severiens , "Mobility of Impurity Ions in

Germanium and Silicon," Phys. Rev. 96, 21-24 (1954).

E. M. Pell, Jr., "Study of Li-0 InteFaction in Si by Ion Drift,"

J. Appl. Phys. 32, 1048-1051 (1961).

20
10. PROCESSING FACILITY

Objective : To establish a microelectronics fabrication laboratory

consisting of oxidation, diffusion, photomasking, and contacting facilities capable of producing specialized silicon devices for use in re- search on measurement methods.

Progress during reporting period : All major steps in the installation of the diffusion furnaces were completed and the initial evaluation

of boron diffusions from a gas-phase source using an open-tube technique

was begun. An open-tube silicon oxidation system has been placed into

operation. Oxides in the range of 5,000 to 6,000 & have been grown on silicon wafers . The thicknesses were confirmed by infrared spectrophotometry absorption measurements.

A metallograph, a Watson-type interferometer for thin film measurement, and associated photographic accessories have been assembled into

a single microscopy area. (T. F. Leedy)

Facilities have been established for the deposition of metallic and

non-metallic thin films by vacuum evaporation and by sputtering. The vacuum evaporation facility has the capability of evaporating two source materials simultaneously. Film thickness is measured by a quartz crystal

deposition monitor. The sputtering facility has the capability of

employing rf, dc, or a combination of these techniques. Conditions for

the rf sputtering of silicon dioxide are now being established. Cathodes

for depositing silicon dioxide, gold, aluminum, silver, titanium, and

tantalum are available.

Other facilities include those for the production of distilled and

deionized water, preparation and examination of metallographic cross- sections, alloying at temperatures up to 1000°C in clean, dry hydrogen

or inert gas atmospheres for chip bonding or contacts , and evaporation

of lithium or other high vapor-pressure evaporants . A vertical furnace

capable of heat treating quartz ampoules at temperatures up to 1000°C

is also available. (W. K. Croll)

Plans for next quarter : Detailed evaluation of the oxidation process will begin. This will include the establishment of a firm procedure, the measurement of oxide thickness by interferometric and infrared absorption techniques , and the measurement of index of refraction by

ellipsometry . In addition, the second diffusion furnace will be put into

operation.

A substrate heater for the vacuum evaporation facility will be designed and installed. Sputtering techniques for available cathodes will

be developed. A system for distributing distilled-deionized water to

a number of chemical hoods will be designed and installed.

21
Fig. 4 Interference Pattern of a 0.54 ym Oxide Step on a Silicon Wafer,

22
11. WIRE BOND EVALUATION

Objective : To improve existing methods or develop new methods for

evaluating the characteristics of wire bond contacts to semiconductor

devices in order to detect more reliably those bonds which eventually

will fail.

Background : A significant fraction of device failures under both

radiation and non-radiation environments can be traced to failure of

wire bonds. Since most wire bonds made are of good quality and do not

fail, the problem is the early identification of these which will even- tually fail in the field. In this project, which was established during

the last quarter of fiscal year 1968, efforts are being made to define

the problems more completely both through searches of the literature and

through visits to orgainzations concerned with wire bonds from a variety

of aspects. In addition facilities are being set up so that additional

experimental work may be begun.

Progress during reporting period : Ten different organizations

(government installations, universities, semiconductor device manufacturers, and bonding machine manufacturers) were visited to discuss the

wire bonding problem. Particular emphasis was placed on bond strength

tests employed and the bonding parameters and material characteristics

which were considered important. Many important contacts were made

during these visits. As was expected, the visits revealed numerous

problems, questions, and a number of contradictory opinions. The results

of these visits are still being studied and evaluated.

Compilation of a bibliography on wire bonding and related subjects

was begun and more than 170 reports and papers have been collected.

(H. A. Schafft and K. 0. Leedy)

A number of experimental approaches are actively being considered.

A systematic study of the conditions that will produce poor bonds has

been initiated. Equipment is being assembled to study, under various

conditions of vibration and shock, the optimum curvature and slack to be

specified for an attached wire bond. Methods for incorporating a 100 per

cent wire pull test directly in a bonding machine are being considered.

Two experimental bonders have been set up to facilitate this investigation. (G. G. Harman and H. K. Kessler)

Plans for next quarter : Evaluation of the information gained on the

visits already made will be continued and new visits will be scheduled

during the next two quarters. Work will continue on assembly and review

of material for the bibliography. Additional facilities for making wire

bonds will be established and detailed experiments will be begun in the areas described above. Other methods for testing wire bonds will be

considered.

23
12. 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.

Background: The line certification program which is now being con- sidered by NASA required for its implementation standard forms of a large

variety of test methods at all phases in the fabrication of microcircuits. Preliminary forms of typical test methods used in microcircuit

fabrication have been compiled by NASA [1]. A project was begun earlier

this year to assist in the review and improvement of these test methods.

In some cases, ASTM standard tests were available to make the measurements suggested. In other cases ASTM task forces are actively working on the measurement methods proposed. These standards were identified and

listed during the first phase of this project. A revised summary of

ASTM activity appears as Appendix F of this quarterly report.

Progress during reporting period : The comparison of the NASA methods with ASTM standards was updated to include recent ASTM work. A

questionnaire has been mailed by the chairman of ASTM Committee F-l in

order to poll committee members on the use of the various tests and on the applicability and use of the ASTM equivalents in production environments. The results of this poll will assist in the determination of

priorities for future work. (W. E. Phillips)

Plans for next quarter: Some test methods, probably those not under

active consideration by ASTM Committee F-l at the present time, will be

selected for editorial revision into a standard format based on ASTM

style.

1. "Test Standards for Microcircuits ," Draft of NASA-STD-XX-3, January

16, 1968.

24
13. 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.

Background : This project is a low-level continuation of a study of

second breakdown which began about 1960. The study led to the development of a new type of specification for maximum operating conditions free

from second breakdown which was based on the concept of a triggering

energy for second breakdown dependent on the operating condition of a transistor [1]. In addition a series of review articles on the field

was published [2] and a comprehensive bibliography of work in the field

of second breakdown was compiled [3], At the present time no experimental work is under way in this project.

Progress during reporting period : Three manuscripts dealing with

second breakdown and thermal runaway in semiconductor devices were re- viewed at the request of journal editors. An invited paper on second

breakdown in transistors was prepared for delivery at the Second Symposium on Reliability in Electronics which will be held in Budapest in

October. (H. A. Schafft)

Plans for next quarter : The invited paper will be presented and a round table discussion will be chaired at the Second Symposium on Reliability in Electronics in Budapest in October.

1. H. A. Schafft and J. C. French, "Second Breakdown in Transistors,"

' IRE Trans. Electron devices3 ED-9, 129-136 (1962)

2. The most recent of these is H. A. Schafft, "Second Breakdown—

A

Comprehensive Review," Proc. IEEE, 55_, 1272-1288 (1967)

3. H. A. Schafft, "Second Breakdwon in Semiconductor Devices—A Bibliography," NBS Tech. Note 431, October 1967.

25
14. THERMAL PROPERTIES OF DEVICES

Objective : To evaluate and, if necessary, improve the measurement

techniques for determining the thermal limitations of semiconductor devices .

Background : The thermal impedance rating of a semiconductor device

is one of the most important ratings specified by a device manufacturer.

It is measured electrically or, in some cases, calculated from heat

transfer considerations by the device manufacturer to determine the maximum allowable power dissipation of a device family. The electrical

measurement of thermal impedance is also used as a screening tool by

some manufacturers to cull out defects such as poor solder wetting due

to faulty processing. Designers use thermal impedance as a tool to determine the junction temperature of a semiconductor device under pulse

as well as d-c operating conditions.

Present practices for measuring thermal impedance yield results of

questionable accuracy and poor reproducibility. It is anticipated that

detailed study of the measurement of thermal impedance will show that

many of the problems involved with this reputed inaccuracy and poor re- producibility are due in part to inherent current distribution non-uniformities and their dependence on electrical operating conditions.

These current distribution non-uniformities will cause localized variations in the junction temperature*.

Temperature sensitive parameters customarily used to determine the

junction temperature may not indicate the highest and therefore most

critical local temperature [l]. Rather, a lower average temperature may

be indicated which will result in calculating a value for thermal impedance which will be too low, leading to inadequate protection of the device. The calculated thermal impedance generally depends on the electrical operating conditions of the device during the measurement. Thus,

without careful specification and control of operating conditions during

measurement, the value of thermal impedance obtained may apparently show

poor reproducibility. Because of the dependence on these operating con- ditions, a single value for the thermal impedance appears to be inadequate for characterizing device performance in general. It should also

be recognized that other problems in the measurement of thermal impedance exist because of difficulties in defining and obtaining suitable

test fixtures and measuring equipment.

JEDEC Committee JS-9 (Industrial Signal Transistors) and EIA Committee MED-32 (Active Digital Circuits) have shown an increasing interest in the thermal measurements problem. Both committees are in the

process of establishing task groups concerned with thermal measurements.

Accomplishments during reporting period : Approximately one hundred

reports and articles on the subject of thermal impedance measurements

and heat flow analysis of semiconductor devices have been indexed and

are being reviewed.

26
An existing system for measuring thermal resistance of low and

medium power transistors by the I pn , VFR » an^ V

p R methods was reconditioned and modified, and is now nearing operational status. Further

modifications to incorporate circuitry to measure current gain (hpp ) were considered because h _ is sensitive to current density and therefore

should be sensitive to the device hot-spot temperature insofar as current

density is sensitive to junction temperature [2].

(F. F. Oettinger and S. Rubin)

Plans for the next quarter : The literature search and review of the

methods of measurement of thermal impedance of semiconductor devices will

continue. Modification of the existing thermal impedance measurement

system will be completed and device measurements initiated. Thermal

mapping of the devices by means of thermographic techniques is planned

and equipment for this work will be assembled. Thermal mapping is necessary to confirm the junction temperature measurements made using the

temperature sensitive electrical parameters of the device and to relate

hot spot temperature to thermal impedance . Application of thermal meas- urements to the problem of evaluating the uniformity and quality of die

attachment will be considered.

1. M. R. P. Young and D. A. Peterman, "Reliability Engineering ,"

Microelectronics and Reliability3 7_, 91-103, (1968).

2. J. T. Nelson and J. E. Iwerson, "Measurement of Internal Temperature

Rise of Transistors," Proc. IKE3 46, 1207-1208, (1958).

27
15. MICROWAVE DIODE MEASUREMENTS

Objective : To determine if NBS can be of service to industry in

defining and resolving some of the problems associated with the measurement of the characteristics of microwave mixer diodes.

Background : Mixer diodes are used to heterodyne weak microwave signals with a strong local oscillator signal to produce an intermediate

frequency. Among the critical parameters of mixer diodes are the con- version loss, output noise ratio, and i-f impedance. These largely determine the noise figure of the receiver in which the diode is used.

In the past, because of the lack of microwave noise standards traceable to NBS, diode manufacturers relied on standard diodes as references

to calibrate test equipment, diode holders, test procedures, measurements, etc. Originally, these standard diodes were calibrated by .one of

several government laboratories, but more recently with the termination

of this service by these laboratories, a round-robin testing program

among the manufacturers on the qualified products list has been used.

While differences in noise figure of 0.1 dB can be resolved by this

method, the accuracy is no better than 1.5 dB.

Since 1964, military specifications for semiconductor devices have

contained the requirement that "guard bands" be used in establishing

working limits so that the true values of the measured parameters are within the absolute values specified in the limits [1]. In addition,

MIL-S-19500D requires that the standard mixer diodes and standard mixer

holders used in the qualification testing of UHF and microwave mixer

diodes shall be calibrated at least once in each successive 12-month period at a laboratory acceptable to the government [2].

In the discussions between the Defense Electronics Supply Center

and the manufacturers, represented by JEDEC Committee JS-3 (UHF and

Microwave Diodes) which followed the adoption of these standards, it became evident that there were no military laboratories which were equipped to calibrate mixer diodes , and that the commercial laboratories

contacted were not interested in furnishing calibration services.

Furthermore, the poor accuracy of the round-robin method of establishing

reference diodes necessitated guard bands that were larger than the

difference in overall (average) noise figure between consecutive mixer

diodes in the same family, e.g. between the 1N21F and 1N21G.

(G. J. Rogers)

Plans for the next quarter : Representatives of NBS , both Washington and Boulder, the military services, and industry (through JEDEC

Committee JS-3) will meet to resolve these questions and to plan future

work.

From the information available it appears that the Boulder Labs can provide calibration of microwave noise sources at the frequencies presently required, 3. 06. and 9.375 GHz. Other problems still to be

28
resolved include:

1. Improvement of the accuracy of the primary standard.

2. Improvements in secondary standards used by industry and in the

field to obtain the desired accuracy and stability.

3. Refinement of the test procedure for the measurement of mixer

output noise ratio and overall (average) noise figure.

4. Simplification of procedures for the application of the standards and the test methods for noise measurements to facilitate their

use by industrial and military personnel.

"Test Methods for Semiconductor Devices," MIL-STD-750A, May 1964,

ammended by Notice 1, August 1965, and Notice 2, September 1966,

par. 4.2.3; "Semiconductor Device, Diode, Silicon, Mixer, Types

1N21WG, 1N21WGM, and 1N21WGMR," MIL-S-19500/321A, 20 March 1967, par.

4.5.2; "Semiconductor Device, Diode, Silicon, Mixer, Types 1N23WG,

1N23WGM, and 1N23WGMR," MIL-S-19500/322a, 20 March 1967, par. 4.5.2;

"Semiconductor Device, Diode, Silicon, Mixer, Types 1N3747W,

1N3747WM, and 1N3747WMR," MIL-S-19500/281A , 6 July 1967, par. 4.5.2.

"General Specification for Semiconductor Devices," MIL-S-19500D,

May 1964, par. 4.4.3.

29
16. SILICON NUCLEAR RADIATION DETECTORSt

Objective : To establish the necessary facilities and undertake a continuing 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 consultation and specialized device fabrication services to the sponsor.

Progress during reporting period : Because of the poor quality of

most large-diameter silicon crystals, detectors with areas greater than

10 cm2 are not available from commercial sources at the present time.

Two silicon crystals with diameters greater than 60 mm, resistivity ^50

fl-cm, and carrier lifetime ^50 ys have recently been received. Crystals

which are used for detectors customarily have carrier lifetime ^1000 ys.

As a result of the low lifetime value in the large-diameter crystals , it

is unlikely that Si (Li) detectors made from these crystals will have desirable low-noise characteristics. A thorough study of these crystals

is planned.

The equipment and plans for a study of electron damage effects in

silicon surface-barrier detectors are nearly completed.

(B. H. Audet and J. A. Coleman)

Plans for next quarter : Silicon intended for use in large-area Si-

(Li) detectors will be characterized. Properties to be measured include

resistivity profile, carrier lifetime, oxygen density by infrared absorption, lithium mobility, and detector characteristics. Electron damage

studies will begin. Irradiations will be made with electrons of the

following energies: 50, 100, 400, 600, and 800 keV. In addition, lifetesting apparatus for silicon detectors will be assembled for use by the

sponsor.

Supported by Goddard Space Flight Center, National Aeronautics and

Space Administration. (NBS Project 4254429)

30
Appendix A

JOINT PROGRAM STAFF

Coordinator: J. C. French

Semiconductor Characterization

Section

Dr. W. M. Bullis, Chief

A. J. Baroody, Jr.

D. L. Blackburn

F. H. Brewer

M. Cosman

Dr. J. R. Ehrstein

R. L. Gladhill

G

.

G . Harman

F. R. Kelly»

H. K. Kessler

Mrs. K. 0. Leedy

R. L. Mattis

Dr. W. E. Phillips

Miss D. E. Sanders §

J. L. Scalest

H. A. Schafft

A. W. Stallings

Dr. L. J. Swart zendruber

W. R. Thurber

Secretaries

:

Miss T. A. Poole

Miss P. K. Smith

Miss R. E. Young

" Summer Student

§ YOC Program

t Guest Worker

Semiconductor Processing Section

Dr. J. A. Coleman, Chief

B. H. Audet

H. A. Briscoe

R. D. Clayton"

W. K. Croll

H. E. Dyson§

W. J. Keery

E. I. Klein

J. Krawczyk

T. F. Leedy

Dr. A. H. Sher

L. M. Smith

G . P . Spurlock

Secretary:

Mrs. S. W. Davis

Electron Devices Section

J. C. French, Chief

Mrs. J. K. Moffitt

F. F. Oettinger

M. Phillips

G. J. Rogers

S. Rubin

M. Sigman

L. R. Williams

Secretaries

:

Mrs. C. F. Bolton (P. T.)

R. S. Brown"

Miss B. Hope

31
Appendix B

COMMITTEE ACTIVITIES

ASTM Committee F-l:

F. H. Brewer, Task Force on Resistivityt

* 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, Epitaxial

Thickness, etc.

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

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

Thin and Thick Films, etc.

A. H. Sher, Task Force on Germaniumt

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

L. J. Swartzendruber , Task Force on Resistivity

" W. R. Thurber, Task Forces on Conductivity Typet, Impurities in

Semi conductors t, Optoelectronic Materials, etc.

Note : " Attended Fall Meeting, September 1968 in Denver

t Participated in Round-Robin Experiments this Quarter

Electronic Industries Association:

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

Resistance Test Methods

Joint Electron Device Engineering Council (EIA-NEMA):

JS-3, UHF and Microwave Diodes: J. C. French, Correspondence on Microwave Diode Specification Problems

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

Breakdown Specifications

JS-9, Industrial Signal Transistors: F. F. Oettinger, Panel Discussion on Thermal Time Constants

JS-1M-, Thyristors: F. F. Oettinger, Thermal Resistance of SCR's

IEEE:

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

Radiation Instruments and

Detectors Committee

Magnetics Group, S. Rubin: Galvanomagnetic Standards Subcommittee

IEC:TC47:

S. Rubin, Galvanomagnetic Devices

NAS-NRC Semiconductor Detector Panel:

J. A. Coleman

32
Appendix C

SOLID-STATE TECHNOLOGY £ FABRICATION SERVICES

Technology services in areas of competence are provided to other

NBS activities and other government agencies as they are requested.

Usually these are short-term services that cannot be obtained through

normal commercial channels. Services provided during the last quarter

are listed below. These indicate the kinds of technology available to

the program.

1. Solid-state technology - (W. K. Croll)

a. A silicon internal reflection element was prepared for the

Vacuum Measurements Section.

b. A zirconium anode was soldered for the Atomic Physics Section.

2. Ultrasonic fabrication - (J. Krawczyk)

Several piezoelectric devices for turbulence studies were

made for the Naval Ship Research and Development Center."

3. Germanium detectors - (A. H. Sher)

a. A 5 cm 3 Ge (Li) gamma-ray detector was made and tested for

the Nuclear Spectroscopy Section.

b. A Ge (Li) gamma-ray detector was reprocessed for the Radiochemical Analysis Section.

4. Quartz fabrication - (E. I. Klein)

a. A synchrotron injector was repaired twice for the Linac

Operations Section.

b. A calorimeter window was prepared for the Solid State

Physics Section.

c. Glass components were made for a micrometer system for the

Vacuum Measurements Section.

d. A liquid nitrogen dewar flask was repaired for the Radiation

Thermometry Section.

5. Gunn devices - (G. G. Harman, K. 0. Leedy, and H. K. Kessler)

In this continuing project for the Harry Diamond Laboratories , attempts were made to fabricate Gunn diodes from three

gallium arsenide epitaxial wafers. For different reasons,

none of the wafers yielded satisfactory diodes.

t

NBS Project 4254431

NBS Project 4251424

33
Appendix D

ELECTRON DEVICES DATA SERVICE

t

The Electron Devices Section of the National Bureau of Standards

Electronic Technology Division maintains an Electron Devices Data Service. This service was originally established in order to provide technical information relative to electron tubes. It was later expanded and now includes data on semiconductor devices and integrated circuits in its

information file on approximately sixty thousand devices of foreign and

domestic origin. Assistance is available, without charge, to individuals

in government and industry who may be interested in obtaining information

regarding the technical specifications, availability, manufacturers, or other pertinent data relative to specific devices.

This quarter, the Data Service has published a revised version of

its tabulation of the characteristics of U.S.S.R. devices extracted from

available foreign publications [1]. In this tabulation, which has been

prepared as a quick reference source on these devices , information is

presented on receiving, power, microwave, cathode ray, and miscellaneous

tubes as well as on semiconductor devices. J. K. Moffitt)

t Supported by NBS. (Project 4252121)

1. J. K. Moffitt, "Tabulation of Published Data on Soviet Electron

Devices," NBS Tech. Note 441, July 1968.

34
Appendix E

JOINT PROGRAM PUBLICATIONS

W. M. Bullis , F. H. Brewer, C. D. Kolstad, and L. J. Swartzendruber

,

"Temperature Coefficient of Resistivity of Silicon and Germanium near

Room Temperature," Solid-State Electronics, 11, 639-646 (1968).

* ' . t t

J. A. Coleman, D. P. Love, J. H. Trainor , and D. J. Williams, "Effect

of Damage by 0.8 MeV - 5.0 MeV Protons in Silicon Surface-Barrier

Detectors," IEEE Trans. Nuc. Sci. 3 NS-15 , 363-372 (1968).

L. J. Swartzendruber, F. H. Ulmer, and J. A. Coleman, "Direct Reading

Instrument for Silicon and Germanium Resistivity Measurements," accepted

by Rev. Sci. Inst.

H. A. Schafft, "Second Breakdown in Transistors," accepted by Second

Symposium on Reliability in Electronics, Budapest, October 1968.

W. M. Bullis, "Measurement Problems in Microcircuit Processing,"

accepted by Government Microcircuits Applications Conference, Gaithersburg , October 1968.

* Vitro Services, Greenbelt, Md. 20771

t NASA-GSFC, Greenbelt, Md. 20771

35
Appendix F

ASTM STANDARDS RELEVANT TO INTEGRATED CIRCUIT PROCESSING

Committee F-l on Materials for Electron Devices and Microelectronics

of the American Society for Testing and Materials is continuing the development of Recommended Practices, Specifications, and Methods of Test

related to the electron device and microelectronics industry. Documents

generated by this committee are published in Part 8 of the ASTM Book of

Standards. This volume appears in November of each year. A few other

relevant documents developed by other ASTM Committees appear in other

parts of the Book of Standards.

At all times , many documents are in various stages of the process

which leads to completed standards . Published and unpublished documents

pertinent to silicon and silicon processing are listed below.

Titles of published documents which have been accepted by the ASTM

as standards or tentatives are preceded by the ASTM serial designation.

This designation consists of a letter and number which identify the

document followed by the last two digits of the year of adoption and,

for tentatives only, a T. Proposed documents published for the first

time in 1968 will not have serial designations assigned until they are approved as either Tentatives or Standards.

The unpublished draft documents listed are now being actively con- sidered by Committee F-l. Although most of these will eventually appear

as published standards, it should be recognized that some will be dropped

before final action is taken.

I. Semiconductor Crystals

A. Resistivity:

F4-3-67T Tentative Method of Test for Resistivity of

Semiconductor Materials [Two-probe method now being revised;

see F84 for improved four-probe method]

F81-67T Tentative Methods of Test for Bulk Semiconductor

Radial Resistivity Variation

F84-68T Tentative Method of Test for Resistivity of Silicon Slices Using Four Pointed Probes

Draft Method of Test for Silicon Epitaxial Layer Resistivity by the Three-Probe Voltage Breakdown Technique

Draft Method of Test for Resistivity of Semiconductor Materials by the Two-Probe Method

36
Draft Method for Determination of Resistivity

and Impurity Profiles in Epitaxial Silicon Layers by the Diode

Capacitance-Voltage Technique

Draft Method of Test for Silicon Epitaxial Lay- er Resistivity by the Spreading Resistance Technique

Draft Method of Test for Silicon Epitaxial Layer Resistivity by the Pour-Probe Method [For use on p/n or n/p

wafers .

]

B. Conductivity Type:

F42-68T Tentative Methods of Test for Conductivity Type

of Extrinsic Semiconducting Materials [Includes hot thermoelectric probe, cold thermoelectric probe, and rectification

methods.

]

C. Crystal Perfection:

F47-68 Standard Method of Test for Crystallographic

Perfection of Silicon by Preferential Etch Techniques

F80-67T Tentative Method of Test for Crystallographic

Perfection of Epitaxial Deposits of Silicon by Etching Technique

Draft Method of Test for Stacking Fault Density

in Silicon Epitaxial Layers by Interference Contrast Microscopy

Draft Method of Test for Crystallographic Perfection of Silicon by X-Ray Topography

D. Carrier Lifetime:

F28-66 Standard Method for Measuring the MinorityCarrier Lifetime in Bulk Germanium and Silicon [Photoconductive

decay method, see also Proc. IRE ^2_, 1292 (1961).]

E. Orientation:

F26-66 Standard Methods for Determining the Orientation

of a Semiconductive Single Crystal [Includes both X-ray and optical methods .

]

F. Hall Mobility:

F76-68 Standard Method for Measuring Hall Mobility in

Extrinsic Semiconductor Single Crystals

37
G. Impurity Content :

F45-64T Tentative Method of Test for Oxygen Content of

Silicon [Now being revised to include a new calibration curve

and a differential method to increase the sensitivity of the

test.]

Draft Recommended Practices for Infrared Absorption Analysis of Impurities in Semiconductor Crystals

Draft Method of Test for Substitutional

Carbon in Silicon

Draft Method of Test for Boron, Phosphorus,

and Arsenic in Silicon

H. Thickness:

F95-68T Tentative Method of Test for Thickness of

Epitaxial Layers of Silicon on Substrates of the Same Type by

Infrared Reflectance [Suitable for n/n4" and p/p+ epitaxial layers . ]

Draft Method of Test for Thickness of Epitaxial

and Diffused Layers by the Angle Lap and Stain Technique

Draft Method of Test for Thickness of Epitaxial

Layers by Stacking Fault Edge Measurement

I. Test Ingots:

F40-68 Standard Method for Preparing Monocrystalline

Test Ingots of Silicon by the Vertical Pulling (Czochralski)

Technique

F41-68 Standard Method for Preparing Silicon Single

Crystals by the Floating-zone Technique

J. Surface Condition:

F21-65 Standard Method of Test for Hydrophobic Surface

Films by the Atomizer Test

F22-65 Standard Method of Test for Hydrophobic Surface

Films by the Water-Break Test

F24- 65 Standard Method for Measuring and Counting

Particulate Contaminants on Surfaces

38
F59-68T Standard Method for Identification of Metal

Particulate Contaminants Found in Electronic and Microelectronic

Components and Systems Using the Ring Oven Technique with Spot

Tests

Draft Method of Test for Bowing of Silicon Wafers

Draft Methods for the Examination and Characterization of Defect Structures and Contaminants as Seen on Specular Silicon Surfaces

II. Photomasking:

F66-66T Tentative Methods of Testing Physical Properties

of Photoresists Used in Microelectronic Fabrication

F93-68T Tentative Recommended Practice for Preparation

of Specifications for the Procurement of Photomasks

Proposed Definitions of Terms Relating to Photomasking Technology for Microelectronics

Draft Method for Dimensional Inspection of Photomasks

Draft Method for the Visual Inspection

of Emulsion Photomasks

Draft Method of Test for Photomask Flatness

Draft Recommended Practice for Determining

Multiple Photomask Registration

III. Water:

D1069-66 Standard Methods of Test for Particulate and

Dissolved Matter in Industrial Waste Water

D1125-64 Standard Methods of Test for Electrical Conductivity of Industrial Water and Industrial Waste Water

D1129-68 Definitions of Terms Relating to Industrial

Water and Industrial Waste Water

D1193-66 Standard Specifications for Reagent Water

D1688-68 Standard Method of Test for Copper in Industrial

Water and Industrial Waste Water

D1888-67 Standard Methods of Test for Particulate and

Dissolved Matter in Industrial Water

39
F57-68 Standard Method of Concentrating and Measuring

Trace Quantities of Copper in High-Purity Water Used in the

Electronics Industry

F60-68 Standard Methods for Detection and Enumeration

of Microbiological Contaminants in Water Used for Processing

Electron and Microelectronic Devices

IV. Other Processing Materials:

F52-65T Tentative Method of Test for Silting Index of

Fluids for Processing Electron and Microelectronic Devices

F58-68 Standard Method of Measuring Specific Resistivity of Electronic Grade Solvents

F61-68 Standard Method of Test for Phosphate in

Electronic Grade Hydrogen-Peroxide Solutions

F62-68 Standard Method of Test for Tin in Electronic

Grade Hydrogen-Peroxide Solutions

F94-68T Tentative Method of Test for Aluminum in

Electronic Grade Hydrogen-Peroxide Solutions

Draft Method of Test for Impurities in Nitric Acid

Draft Method of Test for

Purity of Boron Tribromide

Draft Method of Test for Purity

of Silicon Tetrachloride

V. Cleaning Procedures

Draft Recommended Practice for the

Cleaning of Silicon Slices

Draft Method of Test for the Cleanness

of an Epitaxial Layer Deposition Apparatus

> Draft Recommended Practice for

Ultrasonic Cleaning

VI. Packaging and Associated Parts

F18-64 Standard Specification and Method for Evaluation of Glass-to-Metal Headers Used in Electron Devices

40
F72-66T Tentative Specification for Gold Wire for Semiconductor Lead Bonding

F78-67T Tentative Method for Calibration of Helium Leak

Detectors by Use of Secondary Standards

F97-68T Tentative Method of Test for Hermeticity of

Electronic Devices by Dye Penetration

F98-68T Tentative Method of Test for Hermeticity of

Electronic Devices by a Bubble Test

F100-68T Tentative Method of Test for Shrinkage Stresses

in Plastic Embedment Materials Using a Photoelastic Technique

(for Electronic and Similar Applications)

F218-68 Standard Method for Analyzing Stress in Cylindrical Metal-to-Glass Seals

Proposed Method of Test for Embedment Stress

Caused by Casting Compounds on Glass Encased Electronic

Components

Draft Specification for Lead-Frame Strips for

Integrated Circuit Packages

Draft Recommended Practice for Testing the

Effect of Encapsulation Systems on Microelectronics

Draft Method of Measurement for Completeness of

Cure-State of Crosslinked Resin Polymers for Electronic Devices

by Means of Hot Indentation

Draft Method of Test for the Effect of Moisture

on Electrical Insulation Varnishes for Plastics

Draft Method of Test for Hermeticity of Electron

Devices by a Helium Mass Spectrometer Test

Draft Method of Test for Hermeticity of Electron

Devices by a Radioisotope Test

Draft Method of Test for Reversion Characteristics of Elastomeric Encapsulation Systems

VII. Clean Rooms

F25-68 Standard Method for Sizing and Counting Airborne Particulate Contamination in Clean Rooms and Other DustControlled Areas Designed for Electronic and Similar Applications

41
F50-65T Tentative Method for Continuous Counting and

Sizing of Airborne Particles in Dust-Controlled Areas by the

Light-Scattering Principle ( for Electronic and Similar Applications )

F51-68 Standard Method for Sizing and Counting Particulate Contaminants in and on Clean Room Garments

F71-68 Standard Method of Test Using Morphological Key

for the Rapid Identification of Fibers for Contamination Control

in Electron Devices and Microelectronics

F91-68T Tentative Recommended Practice for Testing for

Leaks in Filters Associated with Laminar Flow Clean Rooms and

Clean Work Stations by Use of a Condensation Nuclei Detector.

VIII. Hybrid Microcircuits

Draft Method of Test for the Sheet Resistance

of Metallic Thin Films by the Four-Probe Technique

Draft Method for Determining the Adhesion of

Metal Films to Hard Translucent Substrates by the Scratch Test

Draft Method of Test for the Thickness of Thin

Films by the Stylus Method

Draft Definitions of Terms in Thin and

Thick Film Technology

Draft Method of Test for Adhesion of Microcircuit Thick Films to Ceramic Substrates

Draft Method of Test for Sheet Resistance of

Resistor Compositions for Thick-Film Circuitry

Draft Method of Test for Noise in

Thin-Film Conductors

Draft Method of Test for Resistivity

of Insulating Materials

42
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