HgCdTe detectors

GaAs/AlGalnP visible lasers, orange LEDs HgCdTe detectors... 

Infrared spectra were taken with a Michelson-Genzel type FTIR instrument (IR/98, IBM Instruments, Inc.) equipped with a liquid nitrogen cooled HgCdTe detector. The optical attachment arrangement is shown in Fig. 2-14. The infrared radiation was p-polarized using ERS-5 wire grid polarizer. 

Practically, the intetferograms are substracted in order to avoid some phase correction problems. If one is working with a room temperature triglycine sulfate (TGS) detector, the four-measurement experiments are not necessary to correct the background 150), whereas with a liquid nitrogen cooled HgCdTe detector, the background correction is necessary. 

The photomultipliers equipped in the Jasco J-500A and Jasco 500C are Hamatsu R-376 and R-316, respectively. The latter is of S-l type. An InSb photovoltaic cell (Judson) is used as a detector for the wavelength region from 1000 to 2400 nm 283). The InSb detector is cooled with liquid nitrogen. An extension of the CD measurements to 11 p can be conducted by using HgCdTe detectors cooled at liquid He temperature 287). 

Group II-VI materials (e.g., CdTe, HgCdTe) Detectors Vertical Bridgman, horizontal Bridgman... 

Mattson Instruments, Madison,WI) equipped with a HgCdTe detector (1 x 1 mm) specially fabricated (Infrared Associates, Cranbury, NJ) for... 

All infrared spectra were recorded with an IR-PLAN microscope (IR-PLAN is a registered trade mark of Spectra Tech, Inc.) integrated to a Perkin-Elmer Model 1800 Fourier transform infrared (FT-IR) spectrophotometer. The spectrophotometer consisted of a proprietary heated wire source operated at 1050°C, a germanium overcoated potassium bromide beamsplitter, and a narrow-band mercury-cadmium-telluride (HgCdTe) detector. The detector was dedicated to the microscope and had an active area of 250 x 250 pm. The entire optical path of the system microscope was purged with dry nitrogen. 

Detector elements having three layer bonding pads are disclosed in JP-A-63148677. This structure allows bonding of the elements without damaging the HgCdTe detector material. 

The invention of US-A-4989067 relates to interconnections from an HgCdTe detector chip to a silicon read-out chip. A beam lead interconnect formed on a silicon chip is used to provide connections with a finer pitch than is achievable when wire-bonding is used. 

An imager having HgCdTe detectors made of different compositions to be responsive to two different infrared frequency windows, and having the detectors formed in the same focal plane is presented in US-A-4620209. 

A shield comprising apertures corresponding to detector elements are attached to an HgCdTe detector layer in JP-A-61147118 to determine the field of view of the detector elements. 

A SiOjtNy reflection preventive film is introduced on the imager presented in JP-A-63150976. This film is formed on a first side of a CdTe substrate with an HgCdTe detector layer formed on an opposite side. 

The problem of cross-talk, presented in JP-A-63170960 above, is solved in JP-A-63229751 where an infrared light absorbing layer is provided on a substrate, opposite the surface holding an HgCdTe detector layer. 

The problem of difference in thermal expansion coefficients between a silicon read-out substrate and an HgCdTe detector substrate is approached in US-A-4783594 by filling the space between the two substrates with a resilient electrically insulating polymeric material and thereafter separating the detector elements from each other by removing a layer of the HgCdTe detector substrate. 

In JP-A-2213174 cross-talk between adjacent photodiodes is reduced by providing a lattice of crystal defects on the surface of a CdTe substrate before an HgCdTe detector layer is grown thereon. 

An HgCdTe layer is epitaxially grown over the surface and individual HgCdTe detector elements 26 are formed in the recessed portions when the Si02 layer has been removed. The surface of the HgCdTe detector elements are then polished and etched before electrodes 27 are connected to connection pads 25. 

A cold shield layer which is formed on a silicon substrate is introduced in JP-A-62272564. The substrate is bonded by a flip-chip process to an HgCdTe detector substrate. 

In JP-A-55150279 the connection between an HgCdTe detector chip and a silicon read-out chip comprises bent buffers which absorb such mechanical stress and which prevent the fragile detector chip being damaged during the connection. 

To reduce the effect of difference in thermal expansion coefficients between a silicon readout substrate and an HgCdTe detector layer, which is bump bonded to the silicon substrate, it is proposed in JP-A-1061056 to affix a second silicon substrate to the HgCdTe detector layer with an intermediate layer of GaAs. 

In JP-A-616386S the mechanical stress of indium bumps connecting a silicon read-out substrate and an HgCdTe detector substrate is reduced by bonding the two substrates together at a temperature which is between the operational and the non-operational temperature of the detector. 

During the bonding process in JP-A-7111323 a silicon read-out substrate and an HgCdTe detector substrate are held at different temperatures. The amount of stress in the connector bumps will be reduced when the device is cooled from room temperature to an operating temperature of 77 K. 

In WO-A-9417557 an integrated circuit assembly is presented which includes a silicon thin film circuit bonded to a substrate of a material selected to provide the assembly with an effective thermal expansion characteristic that approximately matches that of an HgCdTe detector array. 

When the flip-chip technique is used to connect two chips of different materials having different thermal expansion coefficients, the connection will be subjected to mechanical stress to a degree dependent on the the thermal history of the array. In JP-A-55150279 (Fujitsu Ltd, Japan, 22.11.80) the connection between an HgCdTe detector chip and a silicon read-out chip comprises bent buffers which absorb such mechanical stress and which prevent the fragile detector chip being damaged during the connection. 

When a silicon read-out chip and an HgCdTe detector chip are bonded together by a flip-chip bonding process, the chips are exposed to a mechanical stress which may lead to damages, especially of the fragile detector chip. Photo-resist films are used in JP-A-61059771 (Fujitsu Ltd, Japan, 27.03.86) to form a spacer. The spacer reduces the mechancial stress of the semiconductor chips during the bonding process. 

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