MIL- STD-883F 2004 TEST METHOD STANDARD MICROCIRCUITS - 第606页
MIL-STD-883F METHOD 5004.11 18 June 2004 16 APPENDIX A 50.3 Any in- line or end- of-l ine sc reens shall be defined, i mplemented and doc umented when us ed in lieu of , or t o supplement inspec tions /tes ts f or k ille…
MIL-STD-883F
METHOD 5004.11
18 June 2004
15
APPENDIX A
50.2.1 The supplier shall define and implement inspection and test procedures at appropriate points to monitor killer and
critical defects (as identified in section 40).
50.2.2 The inspection and test procedures shall consist of sampling plans which recognize the sources of defects and
their variance (ie: random, variation from die to die within a wafer, variation from wafer to wafer within a lot, variation from lot
to lot, variation with date of manufacturer). Sample plans shall be consistent with statistical practices (distributional form
and alpha/beta risks). The population to be sampled must be homogeneous.
Examples of homogeneity considerations include:
Lots that have been split or otherwise altered for rework are not considered homogeneous, unless otherwise
demonstrated, and therefore require independent sampling of the non-homogeneous (reworked) population. If
different pieces of processing equipment are used at the same process step (mask level), for the same purpose (eg:
use of multiple wafer steppers on the same wafer lot), these tools must demonstrate the killer and critical defect
characteristics are statistically comparable, for a given wafer lot to be considered a homogeneous population.
50.2.3 Inspections and tests must consider, but are not limited to worst case locations (as identified in Section 40).
Examples Include: 1) At an LPCVD operation, the defect characterization might determine particles to be consistently
higher on wafers at, or near, the door end of the tube, sampling at LPCVD must comprehend inspection at this location.
While characterizing metal bridging, one location on the die might appear consistently more prone to bridging than other die
locations, sampling criteria should include inspections at this location.
50.2.4 Inspection and test procedures must make use of "look backs". A look back inspection examines the current
process step and one or more preceding process steps. This procedure allows for inspection/test of telescoping effects
(magnifies or enhances the defect) and/or defects decorated by subsequent processing. This technique allows for additional
opportunities to inspect/test for killer and critical defects in preceding layers.
Examples Include: 1) While inspecting field oxidation it is possible to look back at pattern definitions in previous
levels. 2) A defect is known to be more obvious after a subsequent LTO deposition (the defect size telescopes),
therefore an inspection at LTO could effectively look back at the previous operation which generate a defect.
50.2.5 Inspection and test procedures must define action limits and the appropriate data to be recorded. Data recording
shall recognize the need for wafer, lot, or product disposition and corrective action (eg: data may need to be classified by
machine number, tool, wafer lot, operator, etc.). These types of data and action limits are derived from the defect
characterization (as identified in section 40) and shall take into account relevant attributes of defects (ie: size, color, mass,
composition, density). Action limits shall comprehend safety margins (as specified in section 40).
50.2.6 As a result of defect characterization (see section 40), non-critical defects shall be monitored, unless the non-
critical defect has been proven not to have any influence on the finished product, regardless of incidence or defect density.
This is required to address situations when:
a. Non-critical defects may mask detection of killer and critical defects (eg: a change in color obscures visual
observation of a killer or critical defect).
b. A non-critical defect becomes critical as a result of increased defect density (eg: due to an increase of non-critical
defects, a chain is formed, creating a critical defect).
c. An inconsistency between the incidence of non-critical and critical defects, signaling a change in the process that
must be explained.
MIL-STD-883F
METHOD 5004.11
18 June 2004
16
APPENDIX A
50.3 Any in-line or end-of-line screens shall be defined, implemented and documented when used in lieu of, or to
supplement inspections/tests for killer and critical defects. The population to be screened must also be defined and
documented (eg: wafers, die, portions of wafers, wafer lots, etc.). These procedures shall only include those screens
proven to be effective, per requirements in section 40. Records of screening results must be maintained (accept/ reject
data).
50.4 The Analytical tools and product, process reliability and equipment monitors must have sufficient capability to
measure defect attributes as defined in section 40. This includes changes in critical defect density (eg: if defect
characterization indicates a 0.1 µm particle is a critical defect at a given mask level, the inspection procedure must be
capable of detecting and quantifying the incidence of particles this size and larger). See attachment #3: Analytical tools.
60. Excursion Containment for Material Exceeding Action Limits
:
60.1 The manufacturer shall confirm that the action limit has been exceeded. This may be accomplished by: record
review, reinspection, increased sampling, higher magnification visual, etc.
60.2 If the condition is confirmed, the manufacturer shall identify and act upon affected material (ie: single wafer, multiple
wafers, whole lot, batches of lots, whole line).
60.3 The manufacturer shall perform analysis on affected material and establish a disposition strategy (ie: root cause
analysis, scrap, screen, rework, etc.).
60.4 The manufacturer shall implement appropriate short term/long term corrective action (ie: screens, process change,
equipment change, design rule change, etc.)
70. Yield analysis
:
70.1 The manufacturer shall establish a yield analysis system as a monitor point to confirm effectiveness of inspections
and tests. Particular attention should be given to those lots that exhibit abnormal variation from expected yields, as defined
by the manufacturer.
70.2 Yield analysis should include root cause analysis to determine and drive process improvements.
70.3 The manufacturer shall coordinate the yield analysis system with a formal material review board (MRB), or other
approved disposition authority, to drive corrective action for "excursion" material (killer or critical defect escapes).
80. System for unexpected failure
:
80.1 The manufacturer shall establish a system to analyze field returns. Determine root cause of failure and drive action
for: identification, containment, disposition, notification and corrective action.
80.2 The manufacturer shall implement a system to capture and contain killer or critical defect escapes originating in
wafer fabrication but found elsewhere in the factory (ie: sort, assembly, test, etc.) and implement corrective action.
80.3 The manufacturer shall review unexpected failures through a formal material review board (MRB), or other approved
disposition authority, that brings together the expertise to identify and contain the discrepant product (killer or critical
defects), to notify internal and external customers, as needed and to implement corrective action. The circumstances for
convening an MRB must be defined.
MIL-STD-883F
METHOD 5004.11
18 June 2004
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APPENDIX A
90. Documentation and data requirements
:
90.1 The results of defect characterization, assessment of effectiveness of screening methods, sampling and inspection
methodologies, procedures and systems for controlling changes shall be made available to the qualifying activity, upon
request.
90.2 Inspection and screening procedures must be placed under formal document and change control. Data records
must be maintained and made available to the qualifying activity, upon request. Data retention must be maintained in
accordance with the procurement specifications.
90.3 Excursion containment procedures must be documented and placed under document control. When appropriate,
records of root cause analysis, containment, disposition and corrective action (via an MRB or other approved disposition
authority) must be maintained and made available to the qualifying activity, upon request. Varying degrees of formality are
essential to any manufacturer's line; therefore, disposition authority may range from the responsible individual to a formal
MRB and documentation may range from initialing a lot traveler to a formal MRB report. The manufacturer shall have
prescribed guidelines for the various methods allowable for disposition action and documentation (eg: if product deviation is
within certain spec or action limits, the line engineer may have disposition authority; if these limits are exceeded, some
higher disposition authority may be required). Records must be retained in accordance with the procurement specifications.
100. Definitions:
(Note: The definitions herein are applicable to this procedure only)
Action limits
-Numerical limits for defect densities, counts, or other metrics used to trigger a response. This response may
involve: investigation, root cause analysis, disposition and corrective action.
Alignment
- Also known as "overlay" or "registration". The proper placement of one photolithography layer atop a
preceding layer.
Blown contact
- A phenomena most often associated with the wet etching of contacts. The etch proceeds laterally at a
rate much greater than is expected or desirable. Typically, the lateral etching is non-uniform with respect to the desired
contact profile.
Cornerholes
- A process phenomena associated with narrow gaps between lines of topography. In particular, where
those lines form an angle of approximately 90 degrees (form a "corner"). A cornerhole is formed when photoresist cannot
cover the severe topography generated by structures like these, allowing a subsequent etch to remove film in the gap
between the lines.
Critical Defects
- Defects known or suspected to cause premature failure but only under certain conditions that have a
small probability of occurrence or any defect that cannot be proven as non-critical.
Defect escapes
- Lots, wafers or die which contain defects that unintentionally get through a manufacturer's inspection
and test system.
DI (DI water)
- De-ionized water. Used for wafer cleaning.
Discrepant material
- any material determined to be unsuitable for its destined form, fit or function, as specified by the
MRB or other disposition authority.
Elements of the process
- Any fundamental piece (building block) of the wafer fab process or process step (eg: thermal
ramp rates, etch rates, recipe' steps, incoming raw materials, etc.). This includes quantifiable/ measurable chemical and
physical phenomena of the wafer fab process.
End-of-line
- The steps after wafer fabrication and initial testing (electrical test, wafer sort). This includes most of what is
commonly referred to as "assembly/test".