AF06-212
TITLE: Indium Antimonide Substrate Growth for Affordable Large-Format MidInfrared (IR) Imagers
TECHNOLOGY AREAS: Materials/Processes, Sensors, Electronics
STATEMENT OF INTENT: This topic holds the greatest potential for meeting the technical needs of our
warfighters supported by PEOs and Centers.
OBJECTIVE: Develop a manufacturing technology to produce low-cost, high-quality 6-inch-diameter
indium antimonide (InSb) substrates.
DESCRIPTION: A specific fighter program is the Department of Defense's (DoD) focal point for defining
affordable next-generation strike aircraft weapon systems for the Navy, Air Force, Marines, and our allies.
The focus of the program is affordability−reducing the development cost, production cost, and cost
of ownership of the family of aircraft. The specific goal of this program is to reduce the cost of megapixel
IR detector assemblies used for fighter aircraft support and protection. Many other government programs
require compact InSb focal plane arrays (FPAs) which operate in extreme environments while providing
high-definition IR images.
InSb is an important semiconductor for IR detector applications in the 3- to 5-micron atmospheric window,
and there has been significant interest in large-area InSb focal plane arrays. The demand for larger
diameter InSb is following the same trends as other semiconductor materials wafers such as silicon, GaAs,
InP, etc. Critical driving factors for increased wafer diameter include the ever accelerating need for larger
focal plane array size and the reduction in processing cost by fabricating more die per wafer.
Chip processing is largely performed at the wafer level, so a logical way to keep costs down and realize
economies of scale is to build more chips on a larger wafer. To meet this need, this solicitation focuses on
the development of undoped 6-inch-diameter InSb, rather than the more established 2- and 3-inch-diameter
single-crystal boules.
InSb Focal plane array are over 10 times greater in area than required 5 years ago. Array sizes have
increased from 250 by 250 to 1K by 1K and customers are now designing 2K by 2K formats. This larger
(2K by 2 K) format corresponds to one array per 100-mm (4-inch) or 75-mm (3-inch) wafer. A 150-mm
(6-inch) InSb substrate will allow four 2K by 2K arrays on one wafer.
Thus, an increase from 100 mm (4 inch) to 150 mm (6 inch) in diameter will create a 2.25 times increase in
surface area that translates into a fourfold increase in yield for 2K by 2 K FPAs. This is based on the
number of arrays that will fit in the largest square aperture of each wafer. The increase in die yield is
anticipated to reduce manufacturing costs on the detector side of the processing.
This solicitation is intended to provide the technology advantage for advanced FPAs and IR systems that
will benefit from the timely availability for large-diameter InSb substrates for military and commercial
high-precision circuitry.
To achieve larger 150-mm-diameter InSb substrates, specific issues need to be resolved for achieving and
maintaining superior electrical results with the wafers. The Phase I program seeks to identify and
implement crystal growth requirements, including equipment scaling, pull rates, temperature gradient
consideration, final wafer thickness, inherent resistivity distribution with associated material characteristics,
and polishing considerations. The ultimate goal of the solicitation is to decrease the cost of 2048 by 2048,
or larger format, mid-IR imagers for DoD applications. Modify conventional cutting and polishing methods
to minimize breakage of very fragile 6-inch-diameter InSb wafers. Identify the requirements, provide
required modifications, and implement prototype 150-mm (6-inch)-diameter InSb substrates for use in
electrical testing. Basic device fabrication as an end task for Phase I is encouraged.
PHASE I: Develop new technology for manufacturing InSb wafers that are 6 inches in diameter, double the
current standard size, which would enable up to 6 times as many FPAs to be produced.
PHASE II: Implement larger diameter substrate process control guidelines and InSb lot specifications.
Manufacturability and verification of large-diameter processing ability in this phase will be demonstrated
by lot-to-lot statistical process control (SPC) implementation and advanced FPA fabrication.
DUAL USE COMMERCIALIZATION: The InSb wafer market worldwide has a market cap of
approximately 3 million dollars. Demand for this material will grow at approximately 15 percent annually
over the next 5 years. The military subcontractor community has maintained a keen interest in larger
diameter wafers since it would provide a significant cost savings at the customer level. The homeland
defense and security has also heightened the demand for IR materials.
REFERENCES: 1. Tevke, Ahmet ; Besikci, Cengiz ; Van Hoof, Chris ; and Borghs, G., “InSb infrared p–i–
n photodetectors grown on GaAs coated Si substrates by molecular beam epitaxy,” Solid-State Electronics,
Volume 42, Issue 6, June, 1998, pp. 1039-1044.
2. Rogalski, Antoni, “Infrared detectors: status and trends,” Progress in Quantum Electronics, Volume 27,
Issue 2-3, 2003, pp. 59-210.
KEYWORDS: infrared, focal plane array, substrates, InSb