semi合集-English.pdf - 第6469页

SEMI G78-0699 © SE MI 1999 2 pads or int erconnect bum ps on a semiconductor device to a set of test needles attached to a probe card. 5.4 bonding p ad — exposed m etal l i c contact area on a semicondu ctor device that …

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.

SEMI G78-0699 © SEMI 19993

5.17 scrub mark — mark left by the probe in the

bonding pad or bump after the probe card has touched

down on the wafer.

5.18 temperature testing — testing of devices at a

controlled temperature level other than ambient.

5.19 test — one complete run-throu gh of the data

collection portion of this document on one automated

wafer prober.

5.20 tester — specialized computer controlled system

designed to test integrated circuits.

5.21 prober communications protocol (see Section

9.6) — means of transmitting data between the tester

and the prober. Common methods are:

• TTL

• RS-232c

• GPIB

5.22 test head — package of electronics (part of the

Tester) which interacts both electrically and

mechanically with the probe card, typically through the

Prober Tester Interface (PTI).

5.23 throughput — rate at which die can be cycled, by

the automatic wafer prober, for the purpose of being

tested. It is inherent in the functionality of an automatic

wafer prober (or any other motorized positioning

device) that accuracy, repeatability and throughput are

intimately and inseparably related.

5.24 touch down — contact between the probe card

and the wafer. This user may choose to define this as

either first electrical or first mechanical contact.

5.25 wafer — semiconductor substrate upon which

multiple die are fabricated.

5.26 wafer boat or wafer cassette — carrier for

multiple wafers.

5.27 wafer chuck — platform withi n an automatic

wafer prober that supports and transports the wafer.

The chuck may contain the means for controlled

temperature testing.

5.28 x, y, z and

— motions relativ e to the center of

the Probe Card when standing in front of the Prober:

• Motion to the right is motion in the positive X-

direction.

• Motion towards the back of the prober is motion in

the positive Y-direction.

• Motion away from the floor is the positive Z-

direction.

• Motion revolving around a Z-axis passing through

the center of the probe card is θ-motion. Motion in

the counter-clockwise direction when facing down

from above the prober is motion in the positive θ-

direction.

5.29 z-clearance — distance between the user defined

initial contact point and the top surface of the wafer

during that portion of the wafer prober’s cycle when the

wafer chuck is moving the wafer between DUTs.

6 Summary of Method

6.1 Objective – A SEMI Probe Sta ndards Task Force

has defined this method. That task force consisted of

members from semiconductor wafer probe system users

and wafer probe system suppliers. This method, in part

a guide to collection of data, is aimed at a specific set of

wafer probe system parameters: accuracy, repeatability

and throughput. This method is a tool that creates

comparative data. That data will act as a criterion by

which multiple wafer probe systems can be judged

competitively.

6.2 Probe System Accuracy and Throughput – A wafer

probe system will have needle placement error due to

the probe system electromechanical systems, and

additional needle placement error due to the probe card

physical alignment of the needles. The degree of

accuracy to which the probe system can place the

chuck, the effectiveness of the probe system's bond pad

to needle alignment, the physical alignment of the

probe card needles in their X and Y plane, and the

probe system's vision resolution and accuracy (x

microns of distance per pixel) will be the factors that

influence a probe system's overall placement

performance.

6.2.1 Probe system comparative acc uracy and

repeatability are established in this method using probe

mark data acquired manually with a vision system or, if

available, through use of an automated probe mark data

analysis system. Acquired data is analyzed with the

Probe Mark Data Analysis algorithm contained in this

method.

6.2.1.1 The intention of this data colle ction exercise is

not to make a deterministic conclusion establishing a

probe system’s accuracy. Data analysis results are only

meaningful in the context of a comparative analysis of

multiple probe systems.

6.2.2 Probe system throughput is be st determined

using time measurements made using a stopwatch.

Other approaches can be applied, such as:

• the time stamp and log file (if available) on the

probe system under evaluation.

• time tracking within the device test program

employed for testing the prober.

6.2.3 Any of these approaches is via ble for measuring

time intervals during probe system operation. That data