MIL- STD-883F 2004 TEST METHOD STANDARD MICROCIRCUITS.pdf - 第317页

MIL-STD-883F METHOD 2018.4 18 June 2004 5 3.1.2 Sampl ing Destr ucti ve Physic al Analys is ( DPA) eval uation . Fi nished pr oduct , wafers , or die may be subjec ted to t he test condit ions and c rit eria def ined wit…

MIL-STD-883F

METHOD 2018.4

18 June 2004

TABLE I. Wafer sampling procedures for various metallization chamber configurations.

Metallization chamber

configuration

/ 2/

Number of

wafer lots

in chamber

Required number of

samples per wafer lot

Sampling plans

per wafer lot

Evaporation Sputtering

Projected plane view of the

Wafer-holder is a circle.

Wafer-holder is stationary

or "wobbulates"

5 2 Four from near the

periphery of the wafer-

holder and 90° apart.

One from the center of

holder. See figure 4.

2 3, 4, or 5 2 See figure 4.

3 3 or 4 2 See figure 4.

4 3 2 See figure 4.

Wafer-holder is symmetrical

(i.e., circular, square, etc.).

Deposition source(s) is above or below

the wafer-holder. Wafer-holder

rotates about its center during

deposition.

1, 2, 3,

or 4

2 2 For each wafer lot, one

from the periphery of the

wafer-holder, and one

from close proximity to

the center of rotation.

See figure 4. 5

Planetary system. One or more

symmetrical wafer-holders (planets)

rotate about their own axes while

simultaneously revolving about the

center of the chamber. Deposition

source(s) is above or below

the wafer-holders.

1, 2, 3,

or 4 per

planet

2 2 For each wafer lot, one

from near the periphery

of a planet and one from

near the center of the

same planet. See

figure 4. 6

Continuous feed. Wafers are

continuously inserted into deposition

chamber through a separate pump down

of an airlock (25 wafer nominal load)

2 2 Two randomly selected

wafers from each wafer

lot.

/ In this case, a wafer lot shall be defined as a batch of wafers which have received together those common processes

which determine the slope and thickness of the passivation steps on these wafers.

/ If a wafer-holder has only one circular row, or if only one row is used on a multi-rowed wafer-holder; the total number

of specified sample wafers shall be taken from that row.

/ If there is more than one wafer lot in a metallization chamber, each wafer lot shall be grouped approximately in a

separate sector within the wafer-holder. A sector is an area of the circular wafer-holder bounded by two radii and the

subtended arc; quadrants and semicircles are used as examples on figure 4.

/ If the wafer lot size exceeds the loading capacity of the metallization system each processed sub-lot will be sampled

as if it was a unique lot.

/ When evaluation data shows that there is no relationship between SEM results and the physical location of the

wafers during the metallization process. It shall be permissible to substitute two randomly selected wafers from each

wafer lot. This analysis shall be repeated after each major equipment repair.

/ Sample wafers need be selected from only one planet if all wafer lots contained in the chamber are included in that

planet. Otherwise, sample wafers of the wafer lot(s) not included in that planet, shall be selected from another

planet(s).

MIL-STD-883F

METHOD 2018.4

18 June 2004

3.1.2 Sampling Destructive Physical Analysis (DPA) evaluation. Finished product, wafers, or die may be subjected to the

test conditions and criteria defined within this test method for the purpose of a DPA evaluation.

3.2 Lot control during SEM examination

. After dice selection for SEM examination, the manufacturer may elect either of

two options:

3.2.1 Option 1

. The manufacturer may continue normal processing of the lot with the risk of later recall and rejection of

product if SEM inspection, when performed, shows defective metallization. If this option is elected, positive control and

recall of processed material shall be demonstrated by the manufacturer by having adequate traceability documentation.

3.2.2 Option 2

. Prior to any further processing, the manufacturer may store the dice or wafers in a suitable environment

until SEM examination has been completed and approval for further processing has been granted.

3.3 Specimen preparation

. When applicable, glassivation shall be removed from the dice using an etching process that

does not damage the underlying metallization to be inspected (e.g., chemical or plasma etch). Specimens shall be mounted

for examination in a manner appropriate to the apparatus used for examination. Suitable caution shall be exercised so as

not to obscure features to be examined.

Specimens may be examined without any surface coating if adequate resolution and signal-to-noise levels are obtained. If

the specimens need to be coated, they shall be coated with no more than 100Å of a thin vapor-deposited or sputtered film of

a suitable conductive material (e.g., Au). The coating deposition process shall be controlled such that no artifacts are

introduced by the coating.

3.4 Specimen examination, general requirements

. The general requirements for SEM examination of general

metallization and passivation step coverage are specified below in terms of directional edge, magnification, viewing angle,

and viewing direction.

3.4.1 Directional edge

. All four directional edges of every type of passivation step (contact window or other type of

passivation step) shall be examined on each specimen (see table II).

3.4.2 Magnification

. The magnification used for examination of general metallization and passivation steps shall be within

the range defined by table II.

3.4.3 Viewing angle

. Specimens shall be viewed at whatever angle is appropriate to accurately assess the quality of the

metallization. Contact windows, metal thickness, lack of adhesion, and etching defects are typically viewed at the angles of

0° to 85° (see figure 2018-3).

3.4.4 Viewing direction

. Specimens shall be viewed in an appropriate direction to accurately assess the quality of the

metallization. This inspection shall include examination of metallization at the edges of contact windows and other types of

passivation steps (see 3.4) in any direction that provides clear views of each edge and that best displays any defects at the

passivation step. This may mean that the viewing angle is perpendicular to an edge, or in parallel with an edge, or at some

oblique angle to an edge, whichever best resolves any question of defects at the passivation step (see figure 2018-5).

3.5 Specimen examination detail requirements

. Examination shall be as specified herein and summarized in table II. The

specimen examination shall be documented in accordance with 3.8.

3.5.1 General metallization

. At low magnification, inspect at least 25 percent or 10,000 square mils, whichever is less, of

the general metallization on each die for defects such as lifting, peeling, blistering, and voiding. Inspection shall be

performed for each layer of each level of metallization.

3.5.1.1 Multi-layer and multi-level metal interconnection systems

. Each layer of each metallization level that is deposited

shall be examined. The current- carrying layer(s) shall be examined with the SEM after removal of the glassivation layer (if

applicable) with a suitable etchant (see 3.3).

MIL-STD-883F

METHOD 2018.4

18 June 2004

3.5.1.2 Barrier/adhesion layers. The examination of barrier/adhesion layers designed to conduct less than 10% of the

total current is not required as this is considered a non-conduction layer.

3.5.1.2.1 Barrier/adhesion layer as a conductor

. The barrier/adhesion layer shall be considered as a conductor

(considering the layer thickness and relative conductivity) provided that the following conditions are satisfied: At least ten

percent of the current is designed to be carried by this layer; and this layer is used in the current density calculations. When

this occurs the barrier/ adhesion layer and/or the principal conducting layer shall satisfy all of the step coverage

requirements collectively as baselined by the manufacturer. Specimen examination shall be in accordance with 3.5 and the

accept/reject criteria as defined in 3.7.1. The barrier/adhesion layer(s) shall be examined using either the SEM or optical

microscope. The following methods may be used to examine these barrier/adhesion layers:

3.5.1.2.1.1 The Etchback procedure

. This involves the stripping of each successive unique layer of metal by selective

etching, with suitable etchants, layer by layer, to enable the examination of each layer. Typically, each successive layer of

metal will be stripped in sequence to expose the next underlying layer for examination. Successive layer removal on a

single die area may be impractical. In this case the wafer area or additional die (dice) immediately adjacent on the slice to

the original die area shall be stripped to meet the requirement that all unique layers shall be exposed and examined.

3.5.1.2.1.2 In-line procedure

. The wafer(s) shall be inspected for the defined accept/reject criteria immediately after

being processed through each unique deposition and corresponding etching operation.

3.5.2 Passivation steps

. Inspect the metallization at all types of passivation steps in accordance with the requirements of

3.5.1.1 and table II.

TABLE II. Examination procedure for specimens

Device type

Area of

examination

Examination Minimum-maximum

magnification

Photographic

documentation 1

Integrated

circuit devices

Passivation steps

(contact windows and

other types of

passivation steps) 2

At least one of

each type of

passivation

step present

5,000X to 50,000X Two of the worst

case passivation

steps

General

metallization 2

25 percent 1,000X to 6,000X Worst case general

metallization

/ See 3.8 (an additional photograph may be required).

/ See 3.7 for accept/reject criteria.