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SEMI G78-0699 © SE MI 1999 1 SEMI G78-0699 TEST METHOD FOR COMPARING AUTOMATED WAFER PROBE SYSTEMS UTILIZING PROCE SS-SPECIFIC MEA SUREM ENTS This te st method w as technica lly approved by the Globa l Autom ated Test Eq…

SEMI G77-0699 © SEMI 1999 8

Symbol Value Specified Datum Measured From Feature Measured To

z41 1 mm

minimum

horizontal datum plane bottom of frame cassette

z43 1 + 0 -1 mm horizontal datum plane bottom rails

z47‡ 210 ± 1 mm

13-frame frame cassette

330 ± 1 mm

25-frame frame cassette

horizontal datum plane bottom of robotic handling flange

z48‡ 15 mm

minimum

bottom of robotic handling flange encroachment of frame cassette top

underneath robotic handling flange

z49‡ 8 mm

maximum

bottom of robotic handling flange top of robotic handling flange

† These dimensions match those of SEMI E1.9 with the same symbol.

‡ These dimensions match those of SEMI E47.1 with the same symbol.

NOTICE: These standards do not purport to address

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other relevant literature respecting any materials

mentioned herein. These standards are subject to

change without notice.

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SEMI G78-0699 © SEMI 19991

SEMI G78-0699

TEST METHOD FOR COMPARING AUTOMATED WAFER PROBE

SYSTEMS UTILIZING PROCESS-SPECIFIC MEASUREMENTS

This test method was technically approved by the Global Automated Test Equipment Committee and is

the direct responsibility of the North American Automated Test Equipment Committee. Current edition

approved by the North American Regional Standards Committee on December 18, 1998. Initially

available at www.semi.org April 1999; to be published June 1999.

1 Purpose

1.1 To define the terms and provide a means of

comparative, or relative measurement for the automated

wafer prober functions: Accuracy, Repeatability and

Throughput.

2 Scope

2.1 This method may be used to evaluate the

performance of a single automated wafer prober, or as a

means to compare many probers. The probers that this

document addresses are defined as fully automated; that

is, having automatic material handling, alignment and

probing capabilities.

3 Limitations

3.1 This test and comparison meth od is not intended to

represent a statistically complete methodology for

measuring the performance of an automated wafer

prober. Its correct use is a practical means to compare

the stepping capabilities of wafer probers within a

specific end user’s environment.

3.2 The definitions of the terms “Repeatability” and

“Accuracy” as used in this document are not in

accordance with those of the National Conference of

Standards Laboratories (NCSL) nor are they intended to

be. They are to be used solely for the purpose of this

document and have no other intended uses.

3.3 It is difficult to characterize an d eliminate high

temperature contributions to positional error such as

probe needle ‘float’. Therefore, it is strongly

recommended that the same probe card be used to

evaluate all of the probers being considered.

3.4 It is recommended that the pro be card is verified to

be in the same condition (i.e. evaluated for positional

accuracy and overall functional condition) both before

and after the conclusion of each test.

3.5 Bump placement on a semiconductor device is

generally located ± 0.001" with respect to their nominal

location. Vertical probe cards used to probe bumps

have an inherent amount of needle drift. Therefore care

must be exercised in using vertical probe cards on

bump devices as a means of prober accuracy

measurement.

4 Referenced Documents

NOTE: As listed or revised, all documents cited shall be the

latest publications of adopted standards.

4.1 SEMI Documents

SEMI E10 — Standard for Definition and Measurement

of Equipment Reliability, Availability and

Maintainability (RAM)

SEMI S2 — Safety Guidelines for Semiconductor

Manufacturing Equipment

5 Terminology

5.1 3

limit — a statistically deriv ed measurement of

process variation. A process that allows a ± 3σ

deviation will allow 2.7 parts per thousand to be outside

the established bounds.

5.2 accuracy — the ability of an a utomatic wafer

prober to index its chuck, and attached wafer, from an

initial position to a subsequent position and make

contact with a static probe tip at a nominal location on

the wafer. In the context of this method, accuracy is

defined as average die offset.

5.2.1 Average die offset is the perpe ndicular distance

measured from the centerline of the die pad to a parallel

line that statistically represents the scrub mark data

point distribution center (see Figure 1). Each data point

shown in this figure represents only the center value of

accumulated scrub marks produced by operation of this

method.

5.2.2 It should be noted that accuracy established by

this method is characteristic of the system, which in

total represents both the automated prober as well as its

probe card. Finally, this method establishes two

accuracy values, a value for pads along the X and Y

axes of the die. These axis directions are arbitrary.

5.2.3 It should be noted that if fully automated prober

set-up modes are not used for probe-needle-to-pad

alignment during testing, the possibility of operator

error should be considered as a variable when

evaluating system accuracy.

5.3 automatic wafer prober — device that

automatically and repeatedly aligns the die bonding

SEMI G78-0699 © SEMI 1999 2

pads or interconnect bumps on a semiconductor device

to a set of test needles attached to a probe card.

5.4 bonding pad — exposed metal lic contact area on a

semiconductor device that is surrounded by dielectric

passivation. This is the point at which a temporary

interconnect is made for wafer level test, and permanent

interconnect for packaging.

5.5 bumps — metallic elevated co ntact area on a

semiconductor device that is used in place of a bonding

pad. A die that is designed to use this type of

connection is commonly called a ‘flip chip’ or direct

chip attach.

5.6 die — individual semiconduct or device. For the

purposes of this method, the dice have not been

singulated, and are still in the form of a wafer. Used

interchangeably (in the context of wafer sort) with the

acronym DUT (Device Under Test).

5.7 overdrive — distance in Z whi ch the wafer is

driven beyond a user defined initial contact point,

typically ‘first electrical contact’.

5.8 overhead test — semiconducto r test method where

the test head is mounted directly over the prober, with

the goal of shortening the distance between the pin

electronics and the probe card. The connection

between the test head and the prober is generally

through a device called a Prober Tester Interface (PTI)

5.9 pin electronics — tester hardware that creates the

test signals used to challenge the DUT.

5.10 probe card — printed wiring b oard or ceramic

substrate with permanently attached needles or contacts

that are aligned at the time of manufacture to match the

contact pattern on a Die. Common types of probe cards

are:

• Blade

• Peripheral / Cantilever (AKA Epoxy Ring)

• Vertical (AKA Area Array or Cobra™)

5.11 probe card planarity and alignment — a user-

specified position of the probe tips in ‘x’, ‘y’ and ‘z’.

5.12 probe needles — the contact p oints between the

probe card and the bonding pads. These are typically

manufactured from one of the following materials:

• Beryllium copper

• Tungsten

• Tungsten-rhenium alloy

• Paliney

5.13 prober tester interface (PTI) — signal-

transmitting electro-mechanical device that connects

the pin cards in the tester to the probe card.

5.14 repeatability — Figure 1 is em pirical data and

represents a statistically significant sample of scrub

marks. This data reveals that probe needles may not

make contact consistently to the same point die to die.

Recall that accuracy is defined in this method as

average die offset. Thus, repeatability simply represents

the three-sigma distribution value for average die offset.

Repeatability will represent 99.7% or a three-sigma

distribution value for the accumulated offset data points

obtained through use of this method.

-20

-15

-10

-5

-20 -15 -10 -5 0 5 10 15 20

microns

Repeatability

ccuracy

Average

approximation of

data points

Raw X-data

Direction of the

probe needle

Figure 1

Raw X-Data

5.14.1 The X-Y plotted centroids of these scrub marks

will be found to form a “cloud” of points, densest in the

center, and thinning out towards the edges.

5.14.2 Repeatability is the radius of th at cloud or

“cluster” of probe marks, as defined by the 3 σ or other

user defined limit of that cloud. The error in the

placement of the center of that cloud, relative to its

nominal target, is defined as the automatic wafer

prober’s “Accuracy”. (See Figure 1)

5.15 set point — the value to which a control system’s

input device has been set, as opposed to the actual value

to which the control system has driven the controlled

variable. For example, the input setting to the wafer

chuck temperature controller, as opposed to the actual,

independently measured temperature of the wafer

chuck.

5.16 soak time — time between a piece of equipment’s

reaching the set point temperature and use of that piece

of equipment.