RU128397U1 - MATRIX RECEIVER - Google Patents

Abstract

An array photodetector consisting of a large integrated circuit (LSI) for reading and processing photosignals and a matrix of photosensitive elements (MFCE) - photodiodes with a common base region with a thickness of at least (2 ÷ 3) inverse intrinsic absorption coefficients and no more than diffusion length of minority carriers, characterized in that, in order to increase the quantum yield and significantly reduce carrier recombination, an antireflection coating is applied on the back side ZnS with preliminary RF cathodic etching by argon ions of the surface of indium antimonide in one process.

Description

The inventive utility model relates to semiconductor devices that are sensitive to infrared (IR) radiation, and can be used in the manufacture of matrix photodetectors (FP) in the spectral region of 3-5 μm based on indium antimonide.

In most modern matrix infrared phase transitions, the photosensitive element matrix (MFCF) is made on the basis of narrow-gap semiconductors (for example, InSb, MCT, etc.), which effectively convert the infrared radiation of the corresponding wavelength range into an electrical signal. Processing (accumulation, amplification and transmission of the signal to consumers) is carried out using a silicon large integrated circuit (LSI), the receiving part of which also has a matrix structure (corresponding to a matrix of photosensitive elements) and is combined with a matrix of photosensitive elements through indium microcontacts.

Known matrix photodetectors in the range of 3-5 μm, in which the fine structure of indium antimonide is docked by means of indium micro columns with silicon readout LSI.

This matrix photodetector, as the closest to the proposed one, is adopted as a prototype [see Proceedings of SPIE Vol. 4086 (2000), pp. 155-157, Fig. 1].

The fabrication of a matrix photodetector (MFP) from bulk material requires thinning the base region to a thickness of 8 ÷ 12 μm thin base region. The thinning process involves defect-free chemical-mechanical polishing to a thickness of the base region of 100 ÷ 80 μm and chemical-dynamic processing to a final thickness. The surface non-flatness with an MFP size of about 10 mm was no worse than ± 2 μm.

In the manufacture of matrix photodetectors (MFPs) that interface with silicon LSI multiplexers using indium columns, illumination falls from the base region of the matrix PSE based on InSb.

Until now, the technology for the production of MFCE from three main autonomous stages has been used:

- manufacture of silicon LSI multiplexer with indium columns;

- fabrication of an array of photodiodes with indium columns on a thick InSb base region, thinning it on a technological precision substrate using chemical-mechanical polishing and chemical-dynamic polishing to a thickness of 10–20 μm, followed by re-sticking the thin InSb structure onto an “enlightened” silicon substrate using an optical glue;

- docking of silicon LSI and the fine structure of InSb on a Si substrate.

The disadvantage of this technology is the loss of the useful signal during the passage of infrared radiation in the Si substrate and optical glue. In addition, in some cases, signal distortion due to interference in the adhesive layer is observed.

Due to the small step size (up to 15 μm), in order to reduce the photoelectric interconnection, it is necessary to thin the InSb base region to 7–10 μm, which becomes problematic in the manufacture of MFCE using the previously developed technology, since difficulties arise when re-bonding the “thin” InSb structure.

The foundations of a technology that eliminates these disadvantages are developed. It consists in thinning the base region with a thickness of 500 μm InCh SEC, pre-hybridized with silicon readout LSI.

The development of a new technological route allows to reduce losses and distortion of the useful signal by eliminating the interfering thin adhesive layer along the path of infrared radiation, to reduce the photoelectric relationship due to the possibility of thinning the photosensitive InSb layer to 7 ÷ 10 μm, as well as by eliminating the re-sticking operations of “thin »InSb structures to reduce the complexity of the production of MFCEs and, consequently, increase the percentage of yield of MFCECs.

In addition, a drawback of conventional technology is the dynamic interconnection in MFPs based on InSb photodiodes, which consists in the fact that after exposure to any group of matrix pixels with high-intensity infrared radiation (for example, blackbody with temperature ≥500 K) from each of the illuminated pixels for For a long time (up to tens of minutes), a residual signal is recorded several times higher than noise (memory effect, latent image effect).

The magnitude of the effect is up to 100 units of noise MFPU when exposed to a soldering iron with a temperature of 230 ° C, or up to 90 dB from the level of powerful infrared radiation. This effect may degrade the performance characteristics of equipment based on the MFP.

To improve the photoelectric characteristics of MFPs, a technology was developed for applying a ZnS antireflection coating with a thickness of ~ 5000 A with preliminary RF cathodic etching with argon ions of the surface of indium antimonide in one process with a minimum reflection at a wavelength of ~ 4 μm.

The inventive utility model is illustrated by the drawing of figure 1, which schematically shows the proposed matrix photodetector in section.

The matrix of photosensitive elements based on indium antimonide 2 with an antireflective coating (ZnS) 1 deposited by means of preliminary RF cathode etching with argon ions of the surface of indium antimonide in one process is combined with silicon LSI readout 4 via indium microcontacts 3.

The inventive matrix photodetector based on indium antimonide operates on the principle of the internal photoelectric effect. The detected radiation enters the matrix of photosensitive elements through bleaching, which is transparent in the working region of the spectrum, by its intrinsic absorption in the base region of indium antimonide and the subsequent diffusion of minority carriers into the region of pn junctions. The signals from the photosensitive elements of the matrix through indium microcontacts get into the readout LSI, where they are processed and output to the recording equipment.

Prototypes of matrix photodetectors of the format 320 × 256 elements with a step of 30 μm were manufactured and tested using the proposed design (see photo of the matrix photodetector in figure 2).

Studies of the obtained samples showed that the sensitivity of structures with ZnS sputtering is 1.5--2 times higher than conventional structures with anodic oxide, and the quantum yield reaches 90%, which indicates a reduced surface recombination rate in the case of preliminary RF cathodic etching with argon ions of indium antimonide surface. In addition, the carrier recombination rate on the back side of the MFCE turned out to be an order of magnitude lower in structures treated with argon ions before ZnS deposition, the main reason for which is the presence of slow states at the anode oxide - indium antimonide interface on the reverse side.

Claims (1)

An array photodetector consisting of a large integrated circuit (LSI) for reading and processing photosignals and a matrix of photosensitive elements (MFCE) - photodiodes with a common base region with a thickness of at least (2 ÷ 3) inverse intrinsic absorption coefficients and no more than diffusion length of minority carriers, characterized in that, in order to increase the quantum yield and significantly reduce carrier recombination, an antireflection coating is applied on the back side ZnS with preliminary RF cathodic etching by argon ions of the surface of indium antimonide in one process.

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