NBS SPECIAL PUBLICATION 400-68

U.S. DEPARTMENT OF COMMERCE / National Bureau of Standards

Semiconductor Measurement Technology:

A Manual Wafer Probe Station

for an Integrated Circuit

Test System

100

.U57

NO. ^00-63

1981
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ATIOlfAL BUKEAtI or VTANDAilUS

LIUIAKT

Semiconductor Measurement Technology: JUL 2 0 1981

A Manual Wafer Probe Station for

an Inflated Circuit Test System

G. P. Carver and W. A. Cullins

Electron Devices Division

Center for Electronics and Electrical Engineering

National Engineering Laboratory

National Bureau of Standards

Washington, DC 20234

U.S. DEPARTMENT OF COMMERCE, Malcolm Baldrige, Secretary

NATIONAL BUREAU OF STANDARDS, Ernest Ambler, Director

Issued May 1981
Library of Congress Catalog Card Number: 81-600033

National Bureau of Standards Special Publication 400-68

Nat. Bur, Stand. (U.S.). Spec. Publ. 400-68. 19 pages(May 1981) CODEN: XNBSAV

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WASHINGTON: 1981

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Table of Contents

Page

Abstract 1

1 . Introduction 1

2. Description 1

3. Parts Specifications 2

Acknowledgments 3

References 3

List of Figures

Page

1. Right-side view of the wafer probe station 5

2. Center view of the wafer probe station 5

3. Left-side view of the wafer probe station 7

4. Right-side view of the probe station enclosure with the lid

closed 8

5. Left-side view of the probe station enclosure with the lid

closed 9

6. Outline drawing of the side view of the wafer probe station with

each part identified numerically or by manufacturer or model

number 10

7. Mechanical drawings for the support parts for the wafer probe

station 11

8. Mechanical drawings for the probe assembly for the wafer probe

station 12

9. Mechanical drawings for assorted parts for the wafer probe

station 13

10. Mechanical drawings for the wafer chuck for the wafer probe

station 14

iii
Disclaimer

Certain commercially available materials or instruments are identified in

this publication for the purpose of providing a complete description of the

work performed. The use of these materials or instruments does not

constitute an evaluation of the performance characteristics of the products

so identified. In no case does such identification imply recommendation or endorsement by the National Bureau of Standards nor does it imply that the

items identified are necessarily the best available for the purpose.

iv
Semioonduotor Measurement Technology:

A Manual Wafer Probe Station for an Integrated

Circuit Test System

by

G. P. Carver and W. A. Cullins

Electron Devices Division

National Bureau of Standards

Washington, DC 20234

This report describes the design of a manual wafer probe station

for wafer-level testing of integrated circuits, test structures,

and test patterns. The station includes a translatable vacuum

chuck, a probe assembly which can be used for probe cards or individual micropositioner-mounted probes, and a microscope holder.

Except for a few components which are commercially available,

construction details are provided for all parts.

Key Wovds: integrated circuit test methods; microelectronic test

structure; probe station; semiconductor process control; test

pattern; test structure; wafer chuck; wafer probe station.

1 . Introduction

Wafer-level testing can be a critical ingredient in a comprehensive test

program to assure integrated circuit functionality in microelectronic devices

and materials research and development. In production facilities wafer testing is usually automated. However, manual probing is frequently required to

supplement automated testing, especially in research and development environments .

On the wafer, measurements can be made using specially designed microelectronic test structures [1,2] or using the product circuit itself. The devices are electrically addressed by probes which are brought into contact

with metallized areas, called probe pads, on the wafer. The mechanism which

includes devices to hold and position the wafer and to bring the probes into

contact with the probe pads on the wafer is usually referred to as a wafer

probe station. Since certain electrical tests must be performed in darkness,

and sometimes in an inert atmosphere, it is frequently desirable that the

wafer probe station is mounted in a suitable enclosure.

The manual wafer probe station and associated enclosure described in this

paper are both versatile and convenient to use. They can be constructed from

inexpensive, readily available materials. Specifications and mechanical

drawings are provided for each of the probe station parts.

2. Description

The manual wafer probe station, including the light-tight enclosure, is shown

in figures 1 through 5. An outline drawing of the mechanism is shown in

figure 6. This drawing also shows the location of the parts which are iden1
tified by number in table 1. In the following description, the various parts

are referred to by their part number.

Wafers are held in place on a vacuum chuck (17) which can be moved forward

rapidly by a lever (22) for accessibility for mounting a wafer on the chuck.

The vacuum chuck is positioned in two directions by an x-y movement translation stage. The probes are brought into contact with the wafer by lowering

the probe-mounting plate (5) with a handle (13) and adjusting screw (9). The

probes can be on a probe card or they can be individual micropositionermounted probes. The parts required to hold a probe card are shown in fig- ure 6. However, the probe-card plate (8) can be replaced with other plates

suitable for a variety of micropositioners . One type of probe plate (7) is

shown in the detailed mechanical drawings; however, it is easy to design

other probe plates for different types of probes. If the probe station is to

be used with both probe cards and micropositioners, it is advisable to fabricate additional mounting plates (6) so that the probes can be changed simply

by replacing the entire probe assembly using the mounting plate screw (14).

3. Parts Specifications

All of the parts identified by number are specified in the detailed mechanical drawings shown in figures 7 through 10.

In addition to the numbered parts, there are other components which must be

obtained. They include the microscope pod, microscope mounting bracket,

probe card holder, translation stages, micrometer heads for the translation

stages, cables and connectors for the probe-pad holder, probe cards or probes, a "V" ways and roller set, and an enclosure.

The microscope shown in figures 1 through 3 is a Bausch and Lomb Stereo Zoom

7 power pod with coaxial illuminator.* The microscope fits into a mounting

bracket called an E arm by the manufacturer. It is necessary to modify the E arm to make room for the motion of the probe assembly. The modification

involves separating the ring that supports the microscope pod from the rack

and pinion gear, cutting off the protrusion at the bottom of the ring where

it adjoins the rack, rotating the bracket containing the gears so that it is

upside down and protrudes upward, and remounting the ring at the bottom of

the rack. In figure 6, the E ring is at top left. The concentric circles

represent the knob which is used to adjust the height of the microscope. The

extension above the knob is the bracket which contains the gears. The ring

support, extending to the left, can be moved downward without interfering

with the probe assembly.

The probe card holder, shown in the pictures and identified in figure 6, can accommodate probe cards with up to 48 pins. Cables are soldered to the

terminals at the end of the holder. The miniature coaxial cables and BNCtype connectors can be seen in figure 2.

* The inicroscope is identified because the modifications to the mounting

bracket are specific to the microscope used. The use of another microscope

would require different mechanical modifications.

2
The wafer chuck translation stages are visible in figures 1 through 3. The

dimensions of parts 17 through 21 were chosen to accommodate the specific

translation stages specified in figure 6. While these units are not unique,

substitution of other manufacturer's stages may require adjustment of certain

dimensions of parts for the wafer chuck. The lower stage is mounted as re- ceived. The upper stage is modified by moving the micrometer head to the

opposite side of the stage. This permits both stages to be operated with the

least amount of hand movement. The micrometer heads for the translation

stages are adjustable from 0 to 50 mm. Since they are not actually used for

measurement in this application, the specific type of micrometer head is

unimportant

The "V" ways and roller set precisely controls the vertical travel. The

adjusting screw (9) and lock screw (10) are used to set the height to which

the probe assembly is lowered by the handle (13).

Fine angular adjustment of the wafer is accomplished by rotating the vacuum

chuck (17) with the adjusting lever (21). By operating levers (21) and (22)

in conjunction, the wafer may be aligned quickly with the probe array.

The aluminum enclosure also shown in the pictures was designed and built for

the probe station. It has the feature that when the lid is closed, a pushbutton switch turns off the microscope illuminator. The box containing the

switch can be seen at the top left in figure 3. By examining the photographs

of the enclosure, the input/output feedthrough connector layout, the lid

handle and the safety catch arrangement should be clear. The purpose of the

double lip which is visible on the edge of the lower portion of the enclosure

(figs. 1 to 3) is to prevent light leaks when the box is closed. The lid

also has a double lip; because lights are usually above the probe station, if

only one edge has a double lip, it should be the edge of the lid. Not visible in the photographs is the vacuum line feedthrough which is at the rear. The vacuum line valves and the vacuum release valve are visible on the left

side of the enclosure.

Acknowledgments

The authors gratefully acknowledge the contributions of others who have provided insights and suggestions during the evolution of the design of the

manual wafer prober. In particular, useful improvements were due to Leonard

Smith, Martin Buehler, Mel Doggett, and Rich Koyama.

References

1. Carver, G. P., Linholm, L. W. , and Russell, T. J., Use of Microelectronic

Test Structures to Characterize IC Materials, Processes, and Processing

Equipment, Solid State Technology 23 (9), 85-92 (September 1980).

2. Buehler, M. G., Comprehensive Test Patterns with Modular Test Structures:

The 2 by N Probe-Pad Array Approach, Solid State Technology 22 (10),

89-94 (October 1979).

3
Table 1. Manual Wafer Prober Station Part Numbers.

1 Column 13 Handle

2 Base 14 Mounting plate screw

3 Spacer 15 Sliding base

4 Roller set holder 16 Track

5 Face plate 17 Vacuum chuck

6 Mounting plate 18 Cam plate

7 Probe plate 19 Lock ring

8 Probe card plate 20 Chuck base

9 Adjusting screw 21 Adjusting lever

10 Lock screw 22 Lever

11 Adjusting screw block 23 Link

12 Stop 24 Sector

4
Figure 1. Right-side view of the wafer probe station. The electrical feedthrough

connectors are visible on the right side of the lower part of the aluminum enclosure.

A probe card is in place in the probe card holder.

5
Figure 2. Center view of the wafer probe station. The vacuum line valves, electrical

connection to the microscope illuminator, and additional electrical feedthroughs are visible on the left side of the enclosure. The pointer and block at left bottom are used to indicate the number of the chip under test.

6
Figure 3. Left-side view of the wafer probe station. The small box at upper left

houses the pushbutton switch which turns off the microscope illuminator when the en- closure lid is closed.

7
Figure 4. Right-side view of the probe station enclosure with the lid closed. The

mechanism at upper right holds the lid open.

8
Figure 5. Left-side view of the probe station enclosure with the lid closed.

9
Figure 6. Outline drawing of the side view of the wafer probe station with each part

identified numerically or by manufacturer or model number. See table 1 for the number

key to the parts.

10
Figure 7. Mechanical drawings for the support parts for the wafer probe station. The

column (part No. 1), base (2), and spacers (3) provide structural support for the

probe assembly and microscope mounting bracket. The height of the spacers can be

increased or decreased from the specified values to accommodate increased or decreased

clearance required for probe card holders or x-y translators other than tne particular

ones identified in figure 6.

11
Figure 8. Mechanical drawings for the probe assembly for the wafer probe station.

The roller set holder (4) and the face plate (5) may require modification to fit "V" ways and roller sets different from the one identified in figure 6. The probe card

plate (8) may also need to be slightly redesigned to adapt to a probe card holder

other than the one identified in figure 6. The probe plate (7), which is interchangeable with the probe card plate (8), is designed for types of manual micropositionermounted probes which fit into the slots around the outside of the arms. For use with

micropositioners having a magnetic base, a circular steel plate can be mounted on the

probe card holder ( 8 )

12
Figure 9. Mechanical drawings for assorted parts for the wafer probe station. The

four holes in the sliding base (15) should be located appropriately to match holes in

the x-y translator.

13
(O in 1 ro ro

\'

3.50-

20

THD

UNDERCUT

T'

SUIT

*

3.7

't,350

MAKE ONE EACH - BRASS

f

t

MAKE ONE- BRASS

1.25- MAKE ONE - ALUM.

-3.25

Figure 10. Mechanical drawings for the wafer chuck for the wafer probe station. The

wafer chuck is attached to the x-y translator by screws which are inserted into countersunk holes drilled in the chuck base (20). A thin, electrically insulating disc

should be mounted beneath the chuck base and the mounting screws should be insulated

by nonconducting sleeves and washers. If holes large enough for the mounting screw

heads are drilled in the cam plate (18), the wafer chuck can be removed from the

translator without being disassembled.

14
NBS-114A iREv. 2-sc) U.S. DEPT. OF COMM. 1. PUBLICATION OR 2. Performing Organ. Report No. 3. Publication Date BIBLIOGRAPHIC DATA REPORT NO. May 1981 SHEET (See instructions) NBS SF 400-68

4. TITLE AND SUBTITLE

Sem-iconduotor Measurement Technology : A Manual Wafer Probe Station for an Integrated

Circuit Test System

5. AUTHOR(S)

G. P. Carver and W. A, Cullins

6. PERFORMING ORGANIZATION (\\ joint or other than NBS, see in struct/on sj

NATIONAL BUREAU OF STANDARDS

DEPARTMENT OF COMMERCE

WASHINGTON, D.C. 20234

7. Contract/Grant No.

8. Type of Report & Period Covered Final

9. SPONSORING ORGANIZATION NAME AND COMPLETE ADDRESS (Street. City. State. ZIP)

Same as item b.

10. SUPPLEMENTARY NOTES

Library of Congress Catalog Card Number: 81-600033

Document describes a computer program; SF-185, FlPS Software Summary, is attached.

11. ABSTRACT (A 200-word or less factual summary of most significant information. If document includes a significant

bi bl iography or I iterature survey, mention it here) This report describes the design of a manual wafer probe station for wafer-level

testing of integrated circuits, test structures, and test patterns. The station

includes a translatable vacuum chuck, a probe assembly which can be used for probe

cards or individual micropositioner-mounted probes, and a microscope holder. Except

for a few components which are commercially available, construction details are provided for all parts.

12. KEY WORDS (Six to twelve entries; alphabetical order; capitalize only proper names; and separate key words by semicolons)

Integrated circuit test merhods; microelectronic test structure; probe station;

semiconductor process control; test pattern; test structure; wafer chuck; wafer

probe station.

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