CN100466302C

CN100466302C - Tellurium-cadmium-mercury infrared double color focus plane detector array chip

Info

Publication number: CN100466302C
Application number: CNB2004100674871A
Authority: CN
Inventors: 叶振华; 胡晓宁; 丁瑞军; 何力
Original assignee: Shanghai Institute of Technical Physics of CAS
Current assignee: Shanghai Institute of Technical Physics of CAS
Priority date: 2004-10-26
Filing date: 2004-10-26
Publication date: 2009-03-04
Anticipated expiration: 2024-10-26
Also published as: CN1617357A

Abstract

This invention discloses a TeCdHg infrared double-color focal plane detector array chip in a mixed structure of an injection plane junction and a mesa heterojunction, which avoids the etch of difficult two-step micro-mesa and get the array chip with the performance approaching to the normal single band HgCdTe focal plane devices.

Description

Tellurium-cadmium-mercury infrared double color focus plane detector array chip

Technical field

The present invention relates to infrared photoelectric detector, specifically be meant a kind of array chip of mercury cadmium telluride (HgCdTe) infrared double color focus plane detector of while pattern.

Background technology

In order to satisfy the requirement of infrared system to focus planardetector, a kind of integrated double color focus plane detector of while pattern has obtained very fast development abroad.Compare with the single band focus planardetector, the pattern double color focus plane detector can be surveyed simultaneously at two wave bands simultaneously, and this can obtain how significant target information, more helps getting rid of spurious signal.

The array HgCdTe infrared double color focus plane detector chip of pattern has had many foreign patents and bibliographical information simultaneously, although there are some difference in they on detail, but all be based on the original position In and the As doping techniques of comparative maturity, by adopting the metal organic chemical vapor deposition technology multilayer p-n-N-N-P type heterojunction material of on tellurium zinc cadmium (CdZnTe) substrate, growing, or by adopting the molecular beam epitaxy technique multilayer n-p-P-P-N type heterojunction material of on tellurium zinc cadmium substrate, growing, then heterojunction material is formed the little table top of the photosensitive unit of array with dry etching method, again with the exposure of dry etching method to little table top bosom layer, form little table top of two step of array, see Fig. 2, thereby become the array double color focus plane detector chip that can respond two wave bands.As European patent EP 0747962-A3 and U.S. Pat 5457331.

In the forming process of the photosensitive unit of above-mentioned array little table top of two steps, must could obtain very two step micro-mesa array of high-aspect-ratio by dry method ion etching machine.These can obtain the dry method ion etching machine of two step micro-mesa array of high-aspect-ratio very, all are very expensive as RIE (the reactive ion etching) reactive ion etching machine of external ECR (electron cyclotron resonance) or ICP (inductively coupled plasma) enhancement mode.So as the key equipment of these schemes, they have limited the development of the integrated HgCdTe infrared double color focus plane detector of pattern simultaneously to a great extent.

Summary of the invention

The purpose of this invention is to provide a kind of expensive process equipment that do not need, the array HgCdTe infrared double color focus plane detector chip that utilizes ripe process conditions just can prepare.

To achieve these goals, the present invention adopts the mixed structure of a kind of injection plane knot and table top heterojunction, avoided the etching of highly difficult little table top of two steps, adopt wet etching and a series of chip array processing technology, just can obtain pattern n-p-P-P-N type array double color focus plane detector chip simultaneously.

Array HgCdTe infrared double color focus plane detector chip of the present invention comprises: GaAs substrate 1 with the CdTe transition zone 2 of GaAs substrate strong bonded, has the little table top 3 and the climbing public electrode 4 of one dimension or two-dimensional arrangements on the CdTe transition zone.

The N type HgCdTe layer 301 that said little table top is mixed by: In successively, doping content is 2.0-8.0 * 10 ¹⁷, thickness is 1.5-3.5 μ m; Hg room doped p type HgCdTe layer 302, doping content is 5.0-15.0 * 10 ¹⁵, thickness is 4.0-7.0 μ m; Doped p type HgCdTe potential barrier barrier layer, Hg room 303, doping content is 6.0-16.0 * 10 ¹⁵, thickness is 0.1-0.6 μ m; Hg room doped p type HgCdTe layer 304, doping content is 4.0-12.0 * 10 ¹⁵, thickness is 7.0-12.0 μ m; There is the B of passing through in surface portion zone at p type HgCdTe layer 304 ⁺The n that injects ⁺ Zone 305 is formed.

N type HgCdTe layer 301 that In mixes and Hg room doped p type HgCdTe layer 302 constitute the P-N table top heterojunction of the shorter infrared wavelength of response.

Hg room doped p type HgCdTe layer 304 and n ⁺Zone 305 constitutes the P-n of the longer infrared wavelength of response ⁺Planar junction.Shorter infrared wavelength here and longer infrared wavelength are just comparatively speaking.

Annotate people n ⁺On the zone 305 In ball 5 is arranged, not injecting in the P type HgCdTe district has In ball 6, on the climbing public electrode 4 In ball 7 is arranged.

The device course of work of the present invention is: when infrared radiation incides on the double-color detector chip from substrate back, after passing transparent GaAs substrate, infrared radiation than short-wave band is absorbed earlier in the uptake zone of table top knot P-N knot, and photo-generated carrier is by the internal electric field of table top knot P-N knot separately, generation than the short-wave band photo-signal by reading interconnection In

ball

6 and 7 outputs; Infrared radiation than long-wave band moves on, and is absorbed behind the arrival long-wave band absorbed layer, and photo-generated carrier is by P-n ⁺The internal electric field of planar junction separately, generation than the long-wave band photo-signal by reading interconnection In

ball

5 and 7 outputs, thereby constitute the focus plane device chip of a detectable double-colored wave band.

Advantage of the present invention is:

1. owing to adopted the technical scheme of annotating people's planar junction and the mixing of table top heterojunction, this makes the shaping of the growth of material, the little table top of photosensitive first array and some key technologies such as deposit of electrode metal film be easy to realize.

2. the substrate that extension HgCdTe material of the present invention uses is commercial GaAs material, want cheap than the ZnCdTe material, and material diameter is big, but extension larger area HgCdTe material.

Description of drawings

Fig. 1 is the structural representation of the array infrared double color focus plane detector chip of prior art;

Fig. 2 is the structural representation of array infrared double color focus plane detector chip of the present invention;

Fig. 3 is the B of chip ⁺Inject n ⁺Regional distribution chart;

Fig. 4 is the scanning electron microscope diagram of array chip;

Fig. 5 is the spectral response curve of two photodetectors of the present invention.

Embodiment

Below in conjunction with accompanying drawing, be 70 * 70 μ m with the little footprint of photosensitive unit ², pattern n in the time of 32 * 32 yuan ⁺The heterogeneous example of becoming of-p-P-P-N type HgCdTe elaborates to the specific embodiment of the present invention:

1. at first, growth table top knot P-N heterojunction on the GaAs substrate, it is the photodiode of response shorter wavelength infrared radiation.As shown in Figure 2, adopt the molecular beam epitaxy technique CdTe transition zone 2 of on GaAs substrate 1, growing successively; The In doping content is 5.0 * 10 ¹⁷, thickness is that 2 μ m, component are 0.45 N layer HgCdTe layer 301, this layer is also in order to make the layer of drawing of public electrode; The concentration of mixing in the Hg room is 1.20 * 10 ¹⁶, thickness is that 6 μ m, component are 0.435p type HgCdTe layer 302.

Then, regrowth doping content is 1.30 * 10 ¹⁶, thickness is that 0.4 μ m, component are the P type potential barrier barrier layer 303 in 0.5 Hg room, to reduce by two spectrum cross-talks between the band of light current signal.

At last, grow doping concentration is 1.10 * 10 ¹⁶, thickness is that 8 μ m, component are the p type HgCdTe layer 304 in 0.285 Hg room.

2. the p-P-P-N type HgCdTe material that obtains by above-mentioned molecular beam epitaxy technique, carry out scribing, cleaning and photoetching after, again 3/4 area is selected by each the photosensitive unit on the p type HgCdTe layer 304, shape is carried out B as the zone of " L " shape ⁺Inject, see Fig. 3, the Plane n of the longer infrared radiation that meets with a response ⁺-p p n junction photodiode array.B ⁺Inject the injection condition that adopts conventional single band focus planardetector, ion energy is 200KeV, and dosage is 5.0 * 10 ¹⁴Cm ^-2, implant angle is 15 degree.

3. adopt a kind of wet etch processor (ZL02261149.5) that sample is rotated automatically to prepare the little table top of the photosensitive unit of array.This device can be eliminated the monolateral peak that conventional wet etching can occur, the phenomenon at bilateral peak, and the etched mesa high homogeneity is at 4mm ²Scope Nei Keda 3%.Corrosive liquid adopts 7.5 ‰ Br ₂/ HBr mixed solution, corrosion temperature is controlled at freezing point, and corrosion rate is 0.1 μ m/sec, and is directly carried out the measurement of little table surface height by the step instrument.Present embodiment has corroded 142 seconds, and the average height of photosensitive first micro-mesa array is 14.4 μ m, and the array high homogeneity is 2.5%.

4. adopt the method for thermal evaporation plated film, next life long side surface and plane ZnS passivation layer 8.The cavity base vacuum of thermal evaporation is higher than 1 * 10 ^-4Pa, layer-growth rate are 0.3nm/sec, and the thickness of growth is 400nm.

5. adopt the Sn/Au metallic diaphragm 9 of ion beam coating film method long Ohm contact electrode in next life and climbing electrode.Before the growing metal rete, utilize the photo etched mask technology to leave electrode hole, again at the freezing point temperature pure hydrochloric acid, come about 5 seconds of ZnS of corroding electrode hole site, to expose the HgCdTe material of electrode hole position.Sample is installed on the double-ion beam coating machine, during plated film, the base vacuum of cavity is higher than 1 * 10 again ^-4Pa.The speed of plating Sn is 0.25nm/sec, and thickness is 30nm; The speed of plating Au is 0.35nm/sec, and thickness is 90nm.At last, behind the Sn/Au metallic diaphragm of waiting to have grown, sample was placed acetone flux about 15 minutes, remove the metallic diaphragm of other position with the dissolving photoresist.

6. the method for employing thermal evaporation prepares the interconnection In post of photosensitive first array, is melt into In

ball

5,6,7 next time in formic acid atmosphere again.Before evaporation In post, the In post growth hole that utilizes the photo etched mask technology to leave to read interconnection, its position just in time is positioned on the Sn/Au metallic diaphragm.When the In colonnade battle array of interconnection was read in preparation, the base vacuum of evaporation cavity was higher than 8 * 10 ^-4Pa, the In purity of evaporation source is higher than 99.99, and the rate controlled of evaporation growth is at 0.2 μ m/min, and the In thickness of metal film is about 12 μ m.Behind the In metal film of having grown, sample was placed acetone flux about 15 minutes, remove the In metallic diaphragm of other position with the dissolving photoresist, obtain In colonnade battle array.At last, sample is placed the melt back furnace apparatus, under the effect of formic acid atmosphere, be heated to 160 ℃ after, In colonnade battle array melt back becomes In ball array.Fig. 4 is the SEM pattern after the balling-up of In post melt back, and there are two In balls in every single photosensitive unit, reads the photo-signal of dual-band infrared radiation respectively.

At last the foregoing description is carried out the response spectrum and the I-V test of two wave bands, as shown in Figure 4, the photodiode of 2 wave bands is respectively 3.04 μ m and 5.74 μ m by wavelength.And the initial response wave length of the cut-off wavelength of shorter wavelength photodiode and longer wavelength photodiode is equal substantially, is about 3.05 μ m, shows that the shorter wavelength photodiode can allow the longer wavelength radiation pass through, and can absorb shorter wavelength radiation again fully.And calculate by Fig. 4, the spectrum cross-talk of longer wavelength is 0.46%, the spectrum cross-talk of shorter wavelength is 6.34%.The spectrum cross-talk of longer wavelength photodiode only has 0.46%, mainly is because when material is grown, and has formed the potential barrier barrier layer of very thin P type minority carrier.Also obtain the average R of shorter wavelength and longer wavelength photodiode by the I-V test ₀The A value is respectively 3.852 * 10 ⁵Ω cm ²With 3.015 * 10 ²Ω cm ², the peak detection rate is respectively 1.57 * 10 ¹¹CmHz ^1/2/ W and 5.63 * 10 ¹⁰CmHz ^1/2/ W, and uniformity all is higher than 12%.

The double-colored array chip performance parameter of the mixed structure that finally obtains almost approaches conventional single band HgCdTe focal plane device performance.It is rational, feasible that the technical scheme of the integrated double-colored chip array of mixed structure is adopted in this explanation.

Claims

1. tellurium-cadmium-mercury infrared double color focus plane detector array chip, comprise: GaAs substrate (1), CdTe transition zone (2) with GaAs substrate strong bonded, little table top (3) and climbing public electrode (4) that one dimension or two-dimensional arrangements are arranged on the CdTe transition zone, little table top (3) is gone up In ball (5) and (6), on the climbing public electrode (4) In ball (7) is arranged, it is characterized in that:

The N type HgCdTe layer 301 that said little table top is mixed by: In successively, thickness is 1.5-3.5 μ m; Hg room doped p type HgCdTe layer 302, thickness is 4.0-7.0 μ m; Doped p type HgCdTe potential barrier barrier layer, Hg room 303, thickness is 0.1-0.6 μ m; Hg room doped p type HgCdTe layer 304, thickness is 7.0-12.0 μ m; There is the B of passing through in surface portion zone at p type HgCdTe layer 304 ⁺The n that injects ⁺Zone 305 is formed;

N type HgCdTe layer (301) that In mixes and Hg room doped p type HgCdTe layer (302) constitute the P-N table top heterojunction of the shorter infrared wavelength of response;

Hg room doped p type HgCdTe layer (304) and n ⁺Zone (305) constitutes the P-n of the longer infrared wavelength of response ⁺Planar junction.