DRS uses LPE-grown SWIR, MWIR and LWIR HgCdTe material to fabricate High-Density Vertically Integrated
Photodiode (HDVIP) architecture detectors. 2.5 μm, 5.3 μm and 10.5 μm cutoff detectors have been fabricated into
linear arrays as technology demonstrations targeting remote sensing programs. This paper presents 320 x 6 array
configuration technology demonstrations' performance of HDVIP HgCdTe detectors and single detector noise data. The
single detector data are acquired from within the 320 x 6 array. Within the arrays, the detector size is 40 μm x 50 μm.
The MWIR detector array has a mean quantum efficiency of 89.2% with a standard deviation to mean ratio, σ/μ = 1.51%. The integration time for the focal plane array (FPA) measurements is 1.76 ms with a frame rate of 557.7 Hz.
Operability values exceeding 99.5% have been obtained. The LWIR arrays measured at 60 K had high operability with
only ~ 3% of the detectors having out of family response. Using the best detector select (BDS) feature in the read out
integrated circuit (ROIC), a feature that picks out the best detector in every row of six detectors, a 320 x 1 array with
100% operability is obtained. For the 320 x 1 array constituted using the BDS feature, a 100% operable LWIR array
with average NEI value of 1.94 x 1011 ph/cm 2/s at a flux of 7.0 x 1014 ph/cm2/s has been demonstrated.
Noise was measured at 60 K and 50 mV reverse bias on a column of 320 diodes from a 320 x 6 LWIR array.
Integration time for the measurement was 1.76 ms. Output voltage for the detectors was sampled every 100th frame.
32,768 frames of time series data were collected for a total record length of 98 minutes. The frame average for a
number of detectors was subtracted from each detector to correct for temperature drift and any common-mode noise.
The corrected time series data was Fourier transformed to obtain the noise spectral density as a function of frequency.
Since the total time for collecting the 32,768 time data series points is 98.0 minutes, the minimum frequency is 170 μHz.
A least squares fit of the form (A/f + B) is made to the noise spectral density data to extract coefficients A and B that
relate to the 1/f and white noise of the detector respectively. In addition noise measurements were also acquired on
columns of SWIR detectors. Measurements were made under illuminated conditions at 4 mV and 50 mV reverse bias
and under dark conditions at 50 mV reverse bias. The total collection time for the SWIR detectors was 47.7 minutes.
The detectors are white noise limited down to ~10 mHz under dark conditions and down to ~ 100 mHz under
Remote sensing programs require detectors with a variety of wavelengths. One example of remote sensing applications is the GOES-ABI program that requires linear arrays of detectors with cutoff wavelengths ranging from the visible to the VLWIR (λc ~ 15 μm). In order to target the variety of remote sensing applications, an internal task was conducted to develop detectors and linear arrays operating under nominal remote sensing applications. SWIR [λc(295 K) ~ 2.5 μm] test detectors have been measured as a function of temperature between 170 K and 295 K. At 200 K the RoA values are in the 106 ohm-cm2 range. MWIR [λc(60 K) = 5.3 μm] and LWIR [λc(60 K) = 10.5 μm] HgCdTe detectors in a 320 x 6 array format have also been measured at 60 K. Within the arrays, the detector size is 40 μm x 50 μm. The MWIR detector array has a mean quantum efficiency of 89.2 % with a standard deviation to mean ratio, σ/μ = 1.51 %. The integration time for the focal plane array (FPA) measurements is 1.76 ms with a frame rate of 557.7 Hz. Operability values exceeding 99.5 % have been obtained. In addition, test diodes at the edge of the array that did not go through a read out integrated circuit (ROIC) were also measured and had quantum efficiency ~ 86 % that agreed well with the ~ 87 % quantum efficiency measured for detectors in the array that were located near the test detectors. The LWIR arrays, measured at 60K also had high operability with only ~ 3 % of the detectors having out of family response. Using best detector select (BDS) feature in the read out integrated circuit (ROIC), a feature that picks out the best detector in every row of six detectors, a 320 x 1 array with 100 % operability is obtained. For the 320 x1 array constituted using the BDS feature, a 100 % operable LWIR array with average NEI value of 1.94x1011 ph/cm2/s at a flux of 7.0x1014 ph/cm2/s has been demonstrated.
An overview of the DRS HDVIP architecture for realization of large-area infrared focal plane arrays (IRFPAs) is given. Improvements needed to meet more stringent application requirements are discussed and modeled. Both theoretical and experimental data are presented.
An overview on DRS' approaches towards realization of HgCdTe photonic infrared detectors based on DRS's proven HDVIP technology is given. The first approach involves the use of a silicon microlens array attached to the detector array, and the second reduction of dark currents in each detector itself. Recent progress is presented.
To improve its capacity to meet customer needs, DRS Infrared Technologies began technology transfer of the VOx uncooled FPA process from its Anaheim facility to its Dallas facility in the Fall of 2002. The new facility delivered its first U3000 arrays (320x240, 51μm pitch) three months after the VOx deposition system was installed, and produced over 300 units of U3000 per month just twelve months after beginning the transfer. Process enhancements and tool upgrades have enabled excellent control of the microbolometer process. Today, this line selectively fabricates arrays with NETD varying from 30mK to 80mK in 15mK bins with less than 30 ms time constant. The same arrays also have low defect density of less than 2% dead pixels and no more than one row and one column out. The arrays are packaged in imager or radiometer (F/1.4) packages. DRS also transferred small and large format arrays with 25μm pitch under the PEO-Soldier Sensor Producibility to the Dallas facility. Production of the 25μm pitch devices is currently more that 100 units per month and is ramping up to meet customer demand. This paper reports on production progress on the U3000s and the status of U3500 and U6000 25μm pitch array.
Vertically integrated photodiode, VIPTM, technology is now being used to produce second generation infrared focal plane arrays with high yields and performance. The VIPTM process employs planar, ion implanted, n on p diodes in HgCdTe which is epoxy hybridized directly to the read out integrated circuits on 100 mm Si wafers. The process parameters that are critical for high performance and yield include: HgCdTe dislocation density and thickness, backside passivation, frontside passivation, and junction formation. Producibility of infrared focal plane arrays (IRFPAs) is also significantly enhanced by read out integrated circuits (ROICs) which have the ability to deselect defective pixels. Cold probe screening before lab dewar assembly reduces costs and improves cycle times. The 240 X 1 and 240 X 2 scanning array formats are used to demonstrate the effect of process optimization, deselect, and cold probe screening on yield and cycle time. The versatility of the VIPTM technology and its extension to large area arrays is demonstrated using 240/288 X 4 and 480 X 5 TDI formats. Finally, the high performance of VIPTM IRFPAs is demonstrated by comparing data from a 480 X 5 to the SADA-II specification.