N212-124 TITLE: Low-cost Mid-wave Infrared Focal-Plane Arrays through Direct-on-Read Out Integrated Circuit Detector Fabrication

RT&L FOCUS AREA(S): Autonomy;Microelectronics

TECHNOLOGY AREA(S): Materials / Processes;Sensors

The technology within this topic is restricted under the International Traffic in Arms Regulation (ITAR), 22 CFR Parts 120-130, which controls the export and import of defense-related material and services, including export of sensitive technical data, or the Export Administration Regulation (EAR), 15 CFR Parts 730-774, which controls dual use items. Offerors must disclose any proposed use of foreign nationals (FNs), their country(ies) of origin, the type of visa or work permit possessed, and the statement of work (SOW) tasks intended for accomplishment by the FN(s) in accordance with section 3.5 of the Announcement. Offerors are advised foreign nationals proposed to perform on this topic may be restricted due to the technical data under US Export Control Laws.

OBJECTIVE: Develop new detectors, bonding methods, or fabrication techniques for mid-wave infrared (MWIR) focal plane arrays that enable lower cost infrared imaging for navigation, object detection, collision avoidance, and force protection.

DESCRIPTION: Electro-Optic and Infrared (EO/IR) sensors are used in a wide variety of applications and missions such as long-range detection and identification of objects, seeing at night, and wide area surveillance. Although infrared offers superior imaging in most scenarios, visible sensors are more proliferated than IR due to the dramatically lower cost and higher pixel resolution available. IR sensors have higher costs compared to visible because of many system factors; this SBIR topic proposes to solve one of those factors: the focal plane array (FPA). The MWIR imaging band of 2.8 um to 5 um is used across the Naval forces for imaging targets in a wide range of atmospheric conditions. The goal is to develop novel MWIR FPA materials or processes to achieve > 20x cost reduction over existing MWIR FPAs.

In order to get an image out of the IR FPA, die-to-die bonding of the FPA to a read out integrated circuit (ROIC) is performed creating a sensor chip assembly (SCA). Multiple infrared imaging technologies are used today for the FPA [Ref 1] and most are now available at higher operating temperatures (HOT) (e.g., above 110 K). All of the highest performing FPAs are made from either group III-V or II-VI semiconductors [Ref 1, 2]. The IR-absorbing material chosen sets the limit on overall FPA size, pixel size, and cost. Some of these factors are directly related to the substrate (e.g., size and cost), while others are material and processing specific (e.g., pixel size). No matter what FPA material is chosen, the ROIC is always made in (Silicon (Si) due to the low-cost manufacturing and superior electronics properties.

To accomplish the goal of a low-cost MWIR FPA, various strategies might be explored. One such method might be the use of IR-absorbing semiconductors that are compatible with Si-complementary metal oxide semiconductor (CMOS) processes. In this approach the absorber would be directly deposited (i.e., grown) on the Si wafer containing the ROIC-enabling large-scale batch processing directly on 200 mm or 300 mm Si CMOS wafers. Multiple material systems within this direct growth area have been explored previously that could be applied to this topic. Possible research directions include, but are not limited to, Group IV materials [Ref 3], III-V direct growth [Ref 4], and quantum dots [Ref 5]. Another such method outside of direct growth on Si is novel direct bonding methods of an FPA wafer to the Si ROIC. In this approach, the FPA active absorber material is grown on III-V or II-VI substrates, then subsequently bonded to the Si ROIC. All solutions should address yield and the ability to scale down to smaller pixels to meet future large format sensing requirements.

The solution should be a drop-in replacement to existing MWIR SCAs and thus should not require significant deviation in design to existing MWIR optics. If the solution requires cooling, then industry standard integrated dewar cooler assemblies (IDCA) or thermoelectric coolers should be used to maximize backwards compatibility.

End of program deliverable design characteristics:

• Specific detectivity (D*) of individual detectors/pixels within the 3 um to 5 um band: above 10^11 Jones [normalized to 2*pi field of view (FOV) and 300 K background]
• Noise equivalent temperature difference (NETD) for imaging array below 25 mK
• Quantum efficiency (QE) within the 3 um to 5 um band: shall be no less than 20% of the peak QE
• Peak QE: shall be between 3 um and 5 um
• Detector cooling: >= 110 K
• Pixel size: <= 10 um
• Frame rate: >= 30 fps
• Dynamic range: >=14 bits

PHASE I: Develop a concept for new detectors, bonding methods, or fabrication techniques for MWIR FPAs that demonstrates the approach, while providing for design scalability for MWIR operation. This demonstration can be for a single-element detector or detector array, along with performance metrics, or demonstration of a direct bonding method.

• Identify major hurdles and physical limits of the approach that might include: dark current, 1/f noise, threading dislocations, thermal stress of dissimilar materials, etc.
• Reports and findings on the fabrication, growth, and tunability of the recipes to create a hardware prototype.
• Investigate, document, and select best-of-breed approaches to a low cost MWIR FPA.
• Test the prototype in a laboratory environment with a minimum of electrical read-out of the dark current and could include quantum efficiency.

PHASE II: Build, develop, demonstrate, validate, and mature the hardware.

• Improve detector level performance metrics such quantum efficiency, detectivity, dark current I-V, and spectral noise.
• Build a test chip carrier suitable for proof-of-concept demonstrations.
• Fabricate a small format FPA suitable for an imaging demonstration. Test chip can either be directly with a ROIC or read out element wise to show detector functionality.
• Test the prototype in a laboratory simulated operational environment and identify metrics to validate the system�s advantages over state-of-the-art in MWIR imagers.
• Work with the Government to identify and develop a representative set of transition opportunities for early deployment of the developed concepts.
• Develop a transition plan for the Program of Record (PoR) and for commercial industries via a Phase III commercialization plan.

PHASE III DUAL USE APPLICATIONS: Apply the knowledge gained in Phase II toward the manufacture of a full frame imaging SCA at 640 x 480 or larger format.

• Build an imaging sensor and characterize its performance using imaging array level performance metrics such as modulation transfer function (MTF), QE, and noise equivalent temperature difference (NETD).
• Identify packaging and yield for transition to a PoR.
• Work with the Navy and applicable industry partners to demonstrate that the SCA can be readily, non-disruptively adapted to an existing EO/IR platforms and optics. Test the sensor in a representative environment (e.g., on a Navy-owned range) with conventional MWIR optics to measure performance comparable to existing state-of-the-art in MWIR cameras.
• Market research and analysis shall identify the most promising users across the Navy and/or commercial markets. Develop and document a methodology for smoothly integrating the capability onto identified platforms.

REFERENCES:

1. Rogalski, A. "Recent progress in infrared detector technologies." Infrared Physics & Technology, 54(3), 2011, pp. 136-154.
2. Martyniuk, P. and Rogalski, A. "HOT infrared photodetectors." Opto-Electronics Review, 21(2), 2013, pp. 239-257.
3. Soref, R. "Group IV photonics for the mid infrared." Proceeding SPIE 8629, Silicon Photonics VIII 862902, 14 March 2013.
4. Tanabe, K. et al. "III-V/Si hybrid photonic devices by direct fusion bonding." Scientific Reports 2(1), Article: 349, April 2, 2012.
5. Rogalski, A. et al. "Comparison of performance limits of HOT HgCdTe photodiodes and colloidal quantum dot infrared detectors." SPIE Defense + Commercial Sensing, SPIE Vol 11407, April 23, 2020.

KEYWORDS: Focal plane array; FPA; infrared imaging; IR; semiconductor processing; read out integrated circuit; ROIC; sensor chip assembly; SCA; mid-wave infrared; MWIR; semiconductor materials