MIL- STD-883F 2004 TEST METHOD STANDARD MICROCIRCUITS - 第321页

MIL-STD-883F METHOD 2018.4 18 June 2004 9 NOTE: Alt ernate methods of im age stor age (e.g. , video dis k or video tape) s hall be ac cept able with t he prior approval of the qualif ying act ivity. 3.8.1 Requi red infor…

MIL-STD-883F

METHOD 2018.4

18 June 2004

3.7.2.1.1 Condition 1. It is determined that the directional edge profile from which metal is absent does not occur in the

major current-carrying directional edge. Such determination shall be made either by scanning all passivation steps of this

type on the remainder of the die, or by the examination of a topographical map supplied by the manufacturer which shows

the metal interconnect pattern.

3.7.2.1.2 Condition 2

. Acceptance shall be on a single wafer basis only.

3.7.2.2 Nonrejectable, noncovered directional edge

. For passivation steps to be acceptable, all directional edges shall be

covered with metallization and be acceptable to the requirements of 3.7.2.1, unless by design. In the event that a directional

edge profile of a particular type of passivation step is not covered with metallization, this shall not be cause for rejection if

the following two conditions occur:

3.7.2.2.1 Condition 1

. It is determined that the directional edge profile from which metal is absent does not occur in the

major current-carrying directional edge. Such determination shall be made either by scanning all passivation steps of this

type on the remainder of the die, or by the examination of a topographical map supplied by the manufacturer which shows

the metal interconnect pattern.

3.7.2.2.2 Condition 2

. None of the other specimens from the sampled wafers representing the lot exhibit a directional

edge profile from which metal is absent in the major current-carrying directional edge.

NOTE: If both 3.7.2.2.1 and 3.7.2.2.2 are satisfied, a wafer lot acceptance basis shall be used. However, if only 3.7.2.2.1 is

satisfied, a single wafer acceptance basis shall be used.

3.7.3 Verification of potential rejects

. At the option of the manufacturer, it shall be permissible to subject the specimen, or

an adjacent sample that exhibits the same reject mode, to a verification test. Given below are some examples of suitable

verification tests:

3.7.3.1 Cross-sectioning

. A passivated sample shall be cleaved or lapped down to bisect the area of concern. The

sample may then be subjected to an etchant that will remove the interconnecting metallization at the inspection surface (i.e.,

approximately perpendicular to the die surface). Specimens may be examined without any special surface coating if surface

charging is not a significant problem and adequate resolution and signal-to-noise levels are obtained. If the specimens are

coated, they shall be coated with a thin vapor-deposited or sputtered film of a suitable conductive material (i.e., 100Å gold).

The coating deposition processes shall be controlled such that no artifacts are introduced by the coating. The sample shall

be prepared (see 3.3) and examined in the SEM for interconnect metallization thickness or percentage coverage at the

passivation step, or any other relevant parameter. Note: This cross-sectioning technique is not conclusive for hairline

microcracks as they are not adequately filled by the passivation material.

3.7.3.1.1 Dimensional errors

. Care must be taken to ensure that the cross-section is close to the center of a contact in

order to avoid dimensional errors due to the rounding of the contact corners.

3.7.3.2 Surface etchback

. The unpassivated sample surface is subjected to a chemical etch which removes the

interconnection metallization from the surface of the die at a known controlled rate. The etching is stopped when the

required metal thickness has been removed. The sample is then prepared (see 3.3) and examined within the SEM for

residual metal at the passivation step/contact window interface. Photographic evidence shall then be taken of the sample(s)

to support the acceptance or rejection of the material.

3.7.3.3 Topographical integration

. A graphical representation of the worst case cross-sectional area is drawn to scale on

appropriate graph paper from comprehensive photographs taken eucentrically about the directional edge. The

cross-sectional area is then graphically integrated. This technique is useful for evaluating metallization with irregular surface

topography.

3.8 Specimen documentation requirements

. A minimum of three photographs for each layer of each level of metallization

inspected per lot shall be taken and retained for a minimum of five years after performance of the inspection. Two

photographs shall be of worst case passivation steps and the third photograph of worst case general metallization. If any

photograph shows an apparent defect within the field of view, another photograph shall be taken to certify the extent of the

apparent defect (see table II).

MIL-STD-883F

METHOD 2018.4

18 June 2004

NOTE: Alternate methods of image storage (e.g., video disk or video tape) shall be acceptable with the prior approval of the

qualifying activity.

3.8.1 Required information

. The following information shall be traceable to each photograph:

a. Date of SEM photograph.

b. Device or circuit identification (type or part number).

c. Area of photographic documentation.

d. Electron beam accelerating voltage.

e. Magnification.

f. Manufacturer.

g. Manufacturer's lot identification number.

h. Record of calculated/measured percentage step coverage.

i. SEM operator or inspector's identification.

j. Viewing angle.

3.9 Disposition of inspected specimens

. SEM samples and contiguous die shall not be shipped as functional devices

unless nondestructive SEM conditions and requirements are met (see 3.10). In order to be considered nondestructive,

suitable life-test data (see 3.11) shall be submitted for approval to the qualifying activity to substantiate the nondestructive

aspects of the test (e.g., radiation hardness degradation-RHD). Additionally, all of the conditions in 3.10 and 3.11 must be

satisfied.

3.10 Nondestructive SEM conditions

. For nondestructive SEM, the following conditions shall apply:

3.10.1 Equipment conditions

a. The accelerating voltage shall be within the 0.5 kV to 2.0 kV range.

b. The absorbed specimen current (as measured with a Faraday cup) shall be less than 500 pA.

c. Total scan time for each test site on the wafer shall not exceed ten minutes.

d. Resolution for metal inspection shall be in accordance with 2 above at the accelerating voltage of 3.10.1a. When

used for other in-line nondestructive SEM evaluations (e.g., photoresist, critical dimension (cd) inspection, etc.) the

resolution shall be sufficient to clearly verify the measurement.

3.10.2 Wafer conditions

a. The wafer lot shall satisfy the thermal stability criteria defined within MIL-STD-883, method 5007, table I.

b. Weekly monitoring of particle counts shall be conducted in the SEM inspection area. The particle count limits shall

be less than or equivalent to the specified wafer fab limits.

c. The wafer shall be clean and free of any surface coating.

MIL-STD-883F

METHOD 2018.4

18 June 2004

3.11 Required data for nondestructive SEM validation

. Data demonstrating that the method is nondestructive as defined

in A.4.3.2.2 of Appendix A of MIL-PRF-38535 shall be submitted to the qualifying activity following the procedure detailed in

3.11.1 through 3.11.3.

3.11.1 Sample conditioning

. Expose a sufficient number of devices to the following conditions to yield a quantity of life

test samples that meet a quantity (accept number) of 45(0) for each validation sample:

a. Sample A: Expose at the worst case SEM operating conditions (i.e., accelerating voltage, absorbed specimen

current and tilt) and normal SEM metallization inspection procedure for a duration of 10 ± 1 minutes.

b. Sample B: Expose at the worst case SEM operating conditions and normal SEM metallization inspection

procedure for an increased duration of 30 ± 3 minutes.

c. Sample C: (Optional at the discretion of the manufacturer.) Control group without any SEM exposure.

3.11.2 Procedure

. Process test groups through all normal screening steps to complete post burn-in electricals, serialize

test samples, and complete 3.11.2a through 3.11.2d.

a. Data log variables on all 25°C dc parameters and record attributes data for all other group A electrical test

parameters, conditions and limits specified in the device specification or drawing (i.e., complete group A, not only

specified life test endpoints).

b. Place test samples, including the control group if applicable, on life test in accordance with method 1005 at 125°C

minimum for 1630 hours or equivalent (130°C for 1,135 hours, 135°C for 800 hours, 140°C for 565 hours, 145°C for

405 hours, 150°C for 295 hours, 155°C for 215 hours, 160°C for 155 hours, 165°C for 115 hours, 170°C for 85

hours, 175°C for 65 hours) with cooldown under bias using test condition C.

c. Repeat 3.11.2a for post life test endpoints.

d. Provide qualifying activity with one set of test results for each sample in terms of variables and attributes data on

pre and post life test endpoints plus analysis of mean and standard deviation of variables data and indication of any

devices which failed any group A test parameters.

3.11.3 Criteria for validating SEM as nondestructive

. If sample A passes single duration and sample B passes triple

duration SEM exposure and life test without failing any device specification or drawing parameters, conditions and limits (or

delta parameter requirements when they are specified), the SEM procedure shall be validated as nondestructive for the

process flow represented by the sample devices and for other devices from the same process flow. With the approval of the

qualifying activity, this SEM nondestructive qualification may be performed on appropriate process monitor structures or

standard evaluation circuits (SEC's) which represent the process flow.

4. SUMMARY

. The following details may be specified in the applicable acquisition document:

4.1 Detail 1

. Single wafer acceptance basis when required by the acquiring activity.

4.2 Detail 2

. Requirements for photographic documentation (number and kind) if other than as specified in 3.8.