MIL-PRF-38535K
APPENDIX C
C.3.4.1.2 Wafer fabrication. As part of certification, the manufacturer shall identify a specific technology or technologies for
the wafer fabrication (see H.3.2.1.2).
a. Statistical process control (SPC) and in-process monitoring program for RHA. SPC is especially critical for maintaining
a technology’s RHACL. This occurs since relatively minor changes in a process flow can drastically effect device
radiation performance. The manufacturer shall identify and document all critical process nodes associated with RHA.
See H.3.2.1.3 for a general list of critical process steps, any deviation from this list shall receive qualifying activity
approval.
b. Technology characterization vehicle (TCV) program. The TCV program is an integral part of a technology’s RHA and
shall be carefully configured to ensure the accurate characterization of a technologies radiation capability. The TCV
program shall be designed to support RHA activities, parametric extraction, model development and validation, SPC
and failure mode analysis. (see H.3.2.2.2.1) The TCV structures shall be used to determine a technology’s RHACL
and in addition determine failure modes and mechanisms by irradiation to 2x RHACL or failure, whichever comes first.
Failure can be either functional or parametric.
c. TCV certification. When radiation hardness is a requirement of the technology, special structures shall be
incorporated into the TCV program to characterize the technology's capability for producing devices with assured
radiation hardness to the RHACL. To determine that the RHACL is appropriate for the technology, the vendor shall
irradiate the TCV to 2x the RHACL or until failure to determine failure mode and mechanism(s). Also, the bounds of
the radiation response shall be determined by testing the appropriate TCV test structures for worst case bias
conditions, annealing conditions, and temperature.
d. Standard evaluation circuit (SEC). The SEC shall utilize all relevant radiation hardness assurance design rules and
shall be used to demonstrate the specified level of performance at the RHACL. When radiation hardness assurance is
a requirement of the technology, the SEC shall be used to certify and monitor the RHACL of a specific fabrication
technology in a specific fabrication facility. The SEC shall be designed so it can be used to assess and monitor the
radiation hardness of the fabrication process and design rules
(see H.3.4.3). The SEC reliability data, including
failure analysis results, shall be available for review by the qualifying activity. For RHA environments, the manufacturer
shall irradiate SEC to 2x the requested RHACL or to failure (whichever occurs first) under worst case bias, annealing
and temperature conditions as a demonstration of the technology’s capability to meet the RHACL. A different SEC
may be required whenever the design rules, the materials, the basic processes, or the basic functionality of the
technology differ.
e. Process monitor (PM). The process monitor is an integral part of a technology’s RHA SPC program for in-line process
monitoring. The structures shall be carefully designed and configured to ensure the accurate characterization of a
technology’s radiation performance and capability. The PM shall support wafer acceptance testing and TCI (see
H.3.2.1.3.2). Any deviation from this guidance shall be justified to the qualifying activity.
When RHA is a requirement of the QML line, as a minimum, process monitors for RHA qualified technologies shall
include test structures to support the following:
(1) Metal oxide semiconductor (MOS) RHA parameters:
(a) Gate oxide thickness; Structures shall be included to ensure gate oxide thickness since this is a critical
parameter affecting radiation performance.
(b) The following parameters shall be measured as a function of total ionizing dose:
(i)
Threshold voltage (VT); The linear VT for each transistor in a cell.
(ii) Linear transconductance (gm); The linear gm for a set of transistors.
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ACTEL [ Actel Corporation ]
