DE3033457A1 - Infrared radiation detector mfr. - involves diffusing mercury into mercury cadmium telluride body to form N-type layer at operating temp. - Google Patents

Abstract

The method comprises the steps of diffusing mercury into at least one surface of a body of mercury cadmium telluride At the operating temp. the body has the characteristics of p-type material. The surface then has an adjoining layer with an excess of mercury. A mask is then laid over the surface and the unmasked portion is subjected to a conversion treatment to produce a localised surface layer which comprises mercury derived from the surface adjoining layer. The mask is then removed and the body heated to out-diffuse mercury from the previously mashed portions of the surface. simultaneously, a quantity of mercury is introduced into the surface adjoining portion below the localised surface layer to maintain an excess of mercury. This layer then has the characteristics of n-type materials and several p-n junctions are obtained.

Description

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Gate assembly The invention relates to methods of manufacture of infrared radiation detector assemblies, in particular, but not exclusively photovoltaic detectors with photosensitive pn junctions.

In British Patent (GB-PS) 1 568 958 there is a method for the production of an infrared radiation detector arrangement described in which at least part of a surface of a body of mercury cadmium telluride undergoing a conversion treatment is subjected to create a surface layer on the body, after which a heating step is performed. In the mentioned GB-PS 1 568 958 Detector arrangements described -is surface layer by electrolytic Anodization of the mercury cadmium telluride is produced and used to a protective and passivating layer on the surface of the body of the assembly to attach, which increases the detection capability of the arrangement. The heating step is any heat treatment for the detector array at one temperature in the range of 6000 - 700C, which can be used to change the properties of the arrangement to improve, e.g. by adding the mercury cadmium telluride material of the detector assembly is glowing from. This anodic, passive surface layer is in particular but not exclusively generated on photoconductive detectors, namely on detectors, in which the effect on the intrinsic photoconductivity of mercury cadmium telluride based. In GB-PS 1 568 958 it is also mentioned that such an anodic passive layer on the surface of a body of a photovoltaic detector arrangement can be generated. In this case, a pn junction is initially on an already known way in the mercury cadmium telluride body formed, after which the passivating surface layer by electrolytic anodization at least part of the main surface of the detector element is formed over the incident radiation to be detected flows to the pn junction. The effect a photovoltaic detector is based on the generation of a photo voltage through the photosensitive pn junction and thus the quality for this junction essential for maintaining favorable detector properties. the The invention of an anodizing treatment described in GB-PS 1 568 958 relates does not affect the formation of a photosensitive pn junction and indeed not even on any type of pn junction.

Since, in certain respects, photovoltaic detectors are potentially considered to be The photoconductive detectors are considered to be superior to, for example, their larger ones Response speed, their lower power dissipation and the possibility of their Effect without an external source of bias is ascribed, has sidelong a longer period of time there has been a need to manufacture photovoltaic detectors, wherein the or each element of the detector is comprised of cadmium mercury telluride. this requires the creation of high quality pn junctions in the material and the formation of contacts with the areas on opposite sides of the pn junctions. pn junctions high Q are also particularly well suited for isolation purposes in photoconductive Detectors.

There have been several different methods of forming pn junctions proposed in mercury cadmium telluride. It was wound that electric Properties of the material can be influenced by having a stoichiometric Imbalance of the constituents of the material is brought about or a doping takes place with a foreign element. In the former case, n-type properties by interstitial cadmium or mercury atoms and can be p-conductive properties caused by mercury and cadmium vacancies or interstitial tellurium atoms will.

When determining the conductivity properties of mercury cadmium telluride the temperature at which the properties mentioned must be taken into account perceived or used because such properties are temperature-dependent #, in the sense that for material of a particular composition a temperature exists, in which a reversal of the line properties can take place. So wise e.g. certain material compositions that form the elements of detectors can be used for operation at 77 °, n-conductive properties at ambient temperature on, while they, on the other hand, have p-type properties at the operating temperature. In addition, it is for certain material compositions, in which the conduction properties a particular area in the body due to an excess or a deficit be brought about on one of the constituents, possible that the presence of pn junction properties at a certain temperature, e.g. at the ambient temperature, is imperceptible, but that such pn junction properties occur naturally another temperature, namely the intended operating temperature, e.g. 770K can be, can be perceived and used. Also is the expression "Properties of a certain type of conduction at a certain temperature" by far Meaning to be understood in such a way that these properties in a temperature range beforehand can ash, within which the said bit temperature lies.

To a part of a body bordering on the surface Material that has p-conductive properties at the operating temperature of the detector has to transform into material with n-conductive properties at this temperature, As is known, mercury can thereby diffuse into such a p-conductive body be that the body and a lot of mercury in one sealed Capsule to be heated. Using this process it is pretty much possible to produce flat pn junctions and a detector element from such a body by creating a mesa structure, but that remains the pn junction unprotected on the side surfaces of the element. This is undesirable unless special measures are taken to protect the side surfaces protection. In addition, if one consists of a number of detector elements Detector should be formed, generating the elements in a common body Regulated etching techniques while making contacts with the individual mesa elements Problems arise, at least if it is not very possible, with a printed contact pattern to use with the areas on the upper surfaces of the individual detector elements.

For the production of so-called "planar" detector elements, it has been proposed that localized in an initially homogeneous body of a certain conductivity type To generate areas of the opposite conductivity type by the fact that a foreign element, e.g. aluminum, selectively in the crystal lattice by diffusion or ion implantation is introduced, with a layer on-the surface selectively against such Eijl1 '# 1rung of an impurity masked. The creation of suitable masking layers and the practice of impurity introduction techniques have proven to be useful time-consuming and, as far as the latter techniques are concerned, proven to be complex.

Other methods have been proposed to cut pn junctions in mercury cadmium telluride to build.

These include the application of layers of different conduction types by vapor phase epitaxy, using the implantation of mercury a photoresist mask, the sputtering of gold or aluminum in by sputtering Deposited mercury cadmium telluride, as well as the diffusion of gold from a deposited th gold-bearing layer.

According to the invention a method for producing an infrared radiation detector arrangement is at least part of a surface of a body of mercury cadmium telluride is subjected to a conversion treatment to form a surface layer on the To produce bodies, after which a heating step is carried out, characterized in that that the surface produced by said conversion treatment is anyway contains a sufficient amount of an element withdrawn from this body to allow afterwards as a source for reintroducing said element into said body to serve, this element being part of said body and such is that when there is an excess concentration in the material of the said Body is present, the properties of n-type material at the operating temperature of the detector arrangement, and that said surface layer heated to a temperature above 10,000 during said heating step is to move an amount of said element from the surface layer to an underlying one Area of the body so that a pn junction is formed in the body.

This method is based on the surprising discovery that it is possible to produce a pn junction of sufficiently high quality in a reproducible manner for a detector (e.g. for use as the photosensitive transition of a photovoltaic detector array) by the simple method for removal of the body material itself (e.g. through an electrolytic anodizing treatment) a source of a constituent element of said body for obtaining n-type Properties and by subsequent heating to a temperature above 10,000, to reintroduce the said constituent element into the underlying area and to form said pn junction. Also, this source can easily be accessed localized on a body surface den so that even planar Detector elements can be formed in this simple way.

Thus, in an important embodiment of the method, there is of the invention locally said surface layer during the heating step on part of a major surface of the body while using the underlying area n-type properties produced by said introduction of the element is only locally adjacent to the aforementioned main surface, so that the formed pn junction extends up to the main surface, such that it is at least partially ends at said main surface. Advantages of such a planar structure, e.g. in relation to the attachment of contacts, have already been described earlier, but as will be described below, this embodiment of the method according to the invention for the production of many different detector arrangements, including monolithic configurations.

Preferably, the surface layer containing the element source is used on mercury cadmium telluride generated at the specified operating temperature the arrangement has the properties of p-conductive material, so that said The heating step causes the said underlying area to have the properties n-conductive material at the specified operating temperature of the arrangement, while the closest part of said body is said 1> -conductive Maintains properties to form said pn junction in the body. This The process is particularly simple.

However, a more complex operation can be used where the called surface layer is generated on mercury cadmium telluride, which at the said operating temperature of the arrangement, the properties of n-conductive material has, and in which the aforementioned heating step causes the underlying Territory the mentioned n-t-eit # nden 1Digensciiaf # (-II as a result of the mentioned introduction of the element of said surface layer retains while the closest Part of said body converted into material by said heating step becomes, the p-type properties at the mentioned operating temperature of the arrangement has, whereby said pn junction is formed in the body.

This more complex process can be more difficult in a reproducible manner carried out and controlled, especially if by an n-type body is assumed and a high temperature in the heating step for conversion the line type is required. In a modified embodiment, this more complex process, which, however, requires more procedural steps, is handled by a Body made of mercury cadmium telluride assumed that at the specified operating temperature the arrangement has the properties of p-conductive material, with prior to production of said surface layer mercury in at least one surface of said Body is diffused to a part of the said surface bordering on the surface To form body, the properties at the specified operating temperature of the arrangement comprises n-type material; thereafter the said surface layer is applied said surface adjacent portion is generated during said heating step has the effect that n-conducting Epnschaften retained in the-mentioned underlying area and outdiffusion of mercury from an exposed part of said the part bordering the surface takes place in order to convert said part into material to convert the said at the said operating temperature of the arrangement Has p-type properties.

In a particularly preferred embodiment of the method according to of the invention comprises said treatment for creating the surface layer the electrolytic anodization of mercury cadminm telluride.

s WllrdO gEfllNdell, plus it through electrolytic anodization and subsequent heating to a temperature above 100 0C more disc-shaped Body made of mercury cadmium telluride (H # (1 # x) Cd Te) among other things is possible, (a) pn transitions x desired quality and with photosensitive properties at the ambient temperature to form in material that has a value of x in the range 0.30 - 0.35, said material and the transitions thus formed e.g. for the application in photovoltaic detectors that are suitable for operation in the wavelength range of 3 - 5 μm are determined at ambient temperature, and (b) pn junctions are more desirable Goodness and form with photosensitive properties at 770K in material; the has a value of x in the full range 0.15-0.35, said Material and the transitions formed in this way, depending on the value of x, e.g. for the application in photovoltaic detectors designed to operate in the wavelength range from 8-14 µm at 77 ° K, and for use in photovoltaic detectors that are suitable for operation in the wavelength range of 3 - 5 / µm at 770K are determined. The exact physical mechanism by which the conversion of the Line type is obtained cannot be fully explained, but it is assumed that in the special case of electrolytic anodization of mercury cadmium telluride a surface layer is created which is rich in mercury, this being Mercury may be incorporated in the form of mercury dioxide. The subsequently The heating step carried out to a temperature above 100 ° C. may result free mercury that diffuses into the underlying body material.

At the same time, the anodically generated surface layer serves as an outdiffusion mask of free quartz silver from the underlying material. on this way, mercury is likely to be incorporated into the crystal lattice, thereby causing n-type properties can be obtained in the underlying area.

It should be noted that this effect cannot be achieved by performing the method of operation Le eriial eii becomes that in of the aforementioned pre-published GB-PS 1,568,958 in the name of the applicant. In the photoconductive detectors according to GB-PS 1 568 958, such an introduction of mercury into the n-type would have Detector area increases the surface doping concentration to n +, whereby the surface recombination speed increases and the passivating effect the anodic surface layer would be degraded.

This contradicts the requirements.

Such an introduction of mercury into the photovoltaic would also have Detectors according to GB-PS 1 568 958 the obtained properties of the photosensitive pn junction previously formed in the detector body impaired and could even e.g. lead to the destruction or short circuit of the named pn junction. Since the anodically generated surface layer does not form an infinite source of mercury, the properties of the underlying material obtained, especially the Properties and the depth of the pn junction formed, to a large extent from the Heating conditions, namely time and temperature, and from the initial one Be dependent on the thickness of the anodically generated surface layer.

Those from the electrolytic anodization of mercury cadmium telluride existing treatment can be carried out such that a surface layer with a thickness of 100 - 3000 i, e.g. a thickness of almost 2000 a, is produced. With a layer with a thickness in the range mentioned, it is possible to have pn junctions in material in a wide range of compositions.

Heating can be done at a temperature in the range of 1250C - 270au and take place during a period ranging from 100 seconds to 40 hours.

In general, the higher the temperature, the shorter the period, which is necessary to effect a suitable conversion of the conductivity type. In addition, the heating time depends to a large extent on the thickness of the anodic generated surface layer, while the perimeter of the source of the conductivity type reversal is not infinite and depends on the thickness of the layer. It can also be for certain Applications, e.g. for photovoltaic infrared detector arrangements, are desirable, to form the pn junction in close proximity to the surface; therefore can be unnecessary long heating times an undesirable diffusion of said material in the Bring about body, which can lead to a deep pn junction, the bad one Has properties. Under certain conditions it may be necessary to use material remove from the surface after the heating step to create a shallow transition to obtain.

As far as the localization of the surface layer is concerned, can such an anodically generated surface layer, which is locally on a Part of a large area extends, are formed in that either the The said part of the surface is locally anodized or the entire surface is anodized and then part of the surface layer thus formed is removed.

Due to the possibility of planar pn junctions according to the invention easy to form, several different types of detector arrays can be formed which end one or more of a major surface of the body of the assembly have pn junctions.

Thus, during the heating step, the perimeter of the main surface generated surface layer be such that most of the formed pn-TY junction extends almost parallel to the aforementioned main surface and the pho1-osenslicllen pn-Tber # ang of a photovoltaic pocket Tnfraro tdetektorelement 5 of the detector arrangement forms. In this case, the aforesaid surface layer may take the form of a configuration separate parts on the named main surface, so that a configuration island-shaped areas, which at the operating temperature of the arrangement the properties have n-conductive material, in a common body part forms having the properties of p-type material, followed by the heating step each n-type area with a conductive connection and the p-type body part is provided with at least one common conductive connection. In this way can easily be a monolithic configuration, e.g. a linear configuration or a matrix of photovoltaic detector elements is formed in a common body will.

A method according to the invention can also be used to form a configuration Island-shaped areas bordering the surface with the properties of n-conducting Materials in a common body with the properties of p-conducting material can be used, each n-type region having after the heating step at some distance from each other first and second conductive terminals is provided to form a photoconductive infrared detection element of the assembly. In this way it is possible to have a monolithic configuration (e.g. a linear Configuration or a matrix of photoconductive detector elements, in one common Body, assuming of course that a suitable one Insulation can be placed between the elements and a photosensitive Effect in relation to the photovoltaic effect can be predominant, being free Charge carriers are separated from each other by fields that lead to the pn junctions belong. This can be compared to known configurations with a number of Mercury cadmium telluride bodies, which are individually attached to a carrier substrate can be beneficial. The formation of the elements in a common body considerably facilitates the attachment of contacts with the elements and enables in addition, precise regulation of the distance between adjacent elements.

In a method in which the surface layer with the element source localized on a major surface of the body may after the heating step at least an edge portion of the surface layer extending in the vicinity of the location at which the said pn junction ends at the surface, can be removed.

This can be particularly beneficial if the surface layer is through electrolytic anodization is obtained because of the presence of an anodic Surface layer on the end part of the pn junction shows the characteristics of the junction possibly due to a build-up under the anodized layer can.

After the heating step, the surface layer can be removed and an etching treatment may be performed to remove material from one surface remove while further electrolytic anodizing of at least a part the main surface, that of the end part of the pn junction in said surface is limited, can be carried out in order to passivate said surface.

Some embodiments of the invention will now be exemplified described. First some examples of the formation of pn junctions in bodies from mercury telluride of several different compositions together with Details relating to the characteristics of the transitions obtained are described, according to which some embodiments in which infrared detector elements are manufactured, can be described on the basis of the accompanying drawings. They show: Figures 1 and 2 the measured voltage-current characteristics of two different pn junctions, the in a mercury cadmium telluride body by decay after the LI'rfilidulIg be formed; Figures 3 to 8 several 5 holes in the production of a a configuration of ten elements photovoltaic infrared detector array by a method according to the invention, FIGS. 3, 4, 6 and 7 being semantic Top views ind and each of the element body consisting of mercury-cadmium metal (1, r arrangement represents part of a carrier substrate place, on which said body is attached, while Figures 5 and 8 are schematic Cross-sections through part of said body in two different stages of manufacture and FIG. 9 is a schematic plan view of part of an oil configuration of ten elements consisting of photoconductive infrared detector array, which by a method according to the invention is made.

It should be noted that FIGS. 3 to 9 are not drawn to scale are. The relative dimensions and proportions of some parts of these figures (especially in cross-section) are enlarged or reduced for the sake of clarity and simplicity shown.

Now, on the whole, some experimental details of the manufacture are presented of pn junctions in mercury cadmium telluride by a method according to the invention given. Samples of polished wafers with a thickness of almost 200 μm, consisting of several Mercury cadmium telluride blocks in the composition range of x between 0.15 and 0.35 were formed by first defining surface areas in a solution of sodium bicarbonate using a drawing of a Photoresist have been anodized. The anodized disks were then down to 18,000 during heated for one hour either in vacuo or in a nitrogen atmosphere. To The disks were heated for 10 minutes in a 5 ole solution of bromine Etched in ethylene glycol and were anodized by sputtering onto the gold contacts as well as the non-anodized areas via a suitable photoresist mask. The I-V characteristics were then measured.

Fig. 1 shows the measured current-voltage characteristics of such a pn junctions formed by the experiment mentioned. This transition was under an anodized surface area with a circular shape with a diameter of 280 µm. The characteristic curves were with a complete ambient lighting under a solid angle of 2ilj #.

Fig. 2 shows the characteristics of another sample, in this In the case of the pn junction formed under the same conditions, a rectangular surface of 125 µm x 185 µm. The characteristics were created with a field of view of 60% obtained and show a lower offset voltage than the sample, its characteristics are shown in FIG.

An embodiment of the method according to the invention will now be described, in which a linear configuration of photovoltaic infrared detector elements in a common body is formed, the configuration in a photovoltaic Infrared detector array is used, designed for operation in the range of 8-14 around at 77 ° K is suitable.

It is made from a disc of mercury cadmium telluride with a Diameter of 11 mm and a thickness of 450 / µm with the composition Hg0.8Cd0.2Te went out. It has the properties of n-conductive material at ambient temperature and the properties of p-type material at 77 E. The acceptor carrier concentration at 770K is typically 21017 cm; the agility is 102 2 -1 -1 1.5. 102 cm2 V- 1 sec- 1 and the specific resistance is 0.2 Ohm.cm. To simplify the Explanation, this material is hereinafter referred to as p-type material. The disc is placed on a ceramic polishing block with a layer of wax. The polishing of the surface of the disc is done with the help of a lathe Use of a basic lapping agent and emery paste. The polishing is a process consisting of several steps, with gradually less Damage in the crystal structure occurs when the thickness is reduced to 400 µm what is achieved through the application of gradually finer abrasive particles and base lapping agents is obtained. When the thickness has been reduced to 400μ, which is due to circumferential lugs is detected on the polishing block, a Etching treatment on the exposed surface of the disc that is still on the polishing block carried out.

This removes another 50 μm from the surface.

The disc is now removed from the polishing block and is over the treated main surface attached to another polishing block. : The polishing gradually becomes finer in application under the same conditions Emery particles and base lapping agent carried out until the thickness reduced to 250 µm is. Then an etching treatment is carried out to another 50 / µm from the exposed one Surface to be removed.

While the disk with a thickness of almost 200 µm is still Attached to the polishing block via a layer of wax is a layer of photoresist attached to the upper surface. A photo masking and developing process is used then performed to make a number of nearly parallel strip-shaped openings in to define the photoresist layer, an etching treatment is then carried out in order to form a first number of almost parallel channels in the disc, on the polishing block a number of almost parallel stripes Define parts of mercury cadmium telluride. In the process of education either single element detectors or linear configuration of existing detectors, the width of the strip-shaped parts is typically 1 / µm. The remaining photoresist layer is removed and a further etching treatment is carried out in such a way that the upper edges of the strip-shaped parts are rounded will.

The next stage in manufacture is the application of a photoresist layer on the upper surfaces of the strip-shaped parts. Using a common The photomasking and developing processes become a number of more or less parallel processes Strips that are almost perpendicular to the longitudinal direction of the strip-shaped parts extend away from the photoresist layer. The mutual distance of these Strip is required by the Similar shape of the detector element certainly. For detectors consisting of a single element, the distance can typically be close to 1 mm, so that elements of 1 mm x 1 mm are obtained. For linear configurations corresponds to the spacing of the length of the elements and in the present Example is the distance 3 mm. Using the defined photoresist layer As an etching mask, an etching treatment is carried out, in that completely through the Disc is etched through to obtain a number of parallel channels and thus a configuration of almost rectangular elements on the polishing block: to define body parts, in the present example of 3 mm x 1 mm each, in which the longitudinal edges are slightly rounded on two opposite sides.

Depending on the particular shape of the detector desired, in particular with respect to the desired method of assembling the element body part and for making electrical contacts with the individual detector elements, from at this stage can be proceeded in different ways. In some embodiments, in particular to form detectors consisting of a single element at least some of the treatment that is required to get the pn junctions in to form a number of element body parts, performed while said Body parts are still present on the polishing block. For example, a layer of photoresist attached and can divide the sensitive areas defined in the element body before electrolytic anodizing treatment on the exposed Areas is carried out, which in relation to their size, the desired sensitive Areas correspond to ought. In such an embodiment, the element body parts removed from the polishing block after the electrolytic anodizing treatment has taken place. A subsequent heat treatment to form the pn junctions under the anodically generated surface layer t; can then be performed on the bodies that are either exposed or already on a suitable one Substrate are mounted.

In the present example, however, the element body parts of 3 mm x 1 mm on the polishing block after they have been defined, removed separately and attached separately to a ceramic substrate, which is on a surface has a printed feedthrough contact pattern.

Fig. 3 shows a plan view of part of such a substrate, on one of the element body parts made of p-conductive (at 77 ° K) mercury cadmium telluride of 3 mm x 1 mm is mounted and is obtained by the method described, only a part of said element body parts is shown in the figure. The substrate 1 consists of high-density aluminum oxide with a thickness of 0.5 mm. On the top surface is a printed gold-plated leadthrough contact pattern Nichrome with a thickness of 0.5 µm. The contact pattern contains a common one Feed-through ladder 2 with a width of 1.9 mm and ten additional feed-through conductors 3 each with a width of 100 / µm and a pitch of 200 / µm. The element body part 4 made of p-conductive material is applied to the substrate 1 by means of an epoxy resin layer attached. The distance between the facing end faces of the conductors 2 and 3 is 1.4 mm.

A layer of photoresist is now on the top surface of the structure from the ceramic substrate 1 and the p-type body 4 mounted thereon.

A photo masking and developing process is performed to in the photoresist layer ten areas of 150 / µm x 100 / µm each with a mutual Define a distance of 100 / um. Fig. 4 shows a plan view of the element 4, with the photoresist layer 5 thereon with ten openings 6 therein.

Electrolytic anodizing treatment is now carried out. This takes place in that the structure from the element body 4 and the carrier substrate immersed in a bath with a sodium bicarbonate solution. The electrical connection of the body 4 with the positive terminal of the supply source is over a tungsten wire is made and a gold electrode present in the solution connected to the negative terminal of the supply source. The anodization takes place with a constant applied voltage of 15 V with an initial current of 7.5 mA for a total of 1 minute.

This treatment can be repeated several times, with each Step the anodically generated surface layer is removed. This anodic Treatment or, if repeated treatment is carried out, such Final stage generated on each of the areas not using during this treatment Photoresist are covered, a surface layer nearly 2000 thick Although it was not possible to determine the exact composition of this layer several experimental tests and processes show that which are carried out on the same surface layers as on other mercury cadmium telluride bodies generated using the same and different electrolytes in the anodizing bath that one component of the layer is mercury dioxide.

The next step in the process is to remove the remaining one Part of the photoresist layer 5. Then the structure undergoes a heat treatment either in vacuum or in nitrogen at atmospheric pressure in a diffusion furnace a temperature of 180 ° C. for a period of 1 hour. the Heat treatment leads to the transformation of an area bordering the surface of the body. The conversion is such that at the desired operating temperature (77 ° K) said area has the properties of n-type material, while a pn junction between said area and the remaining part of the body is present, which has p-conductive properties at the temperature mentioned. For the sake of clarity of the drawing, this area is longitudinal in the section of FIG that of the line V-V in Eig. 4 corresponding Lijiie as an n-type area 9 Darges (e3lL and forms a pn junction 10 with the p-conducting body 4. The According to the figure, the pn transition turns on the surface just outside the circumference the anodically produced surface layer 7. The pn junction extends for the most part nearly parallel to the upper surface of the body and on an animal of the same of nearly 6 / µm.

The anodically generated surface layer 7 is then etched removed and another etching treatment is performed to nearly 0.5 / µm from the surface of the mercury cadmium telluride body.

Another layer of photoresist is now all over the surface of the mercury cadmium telluride body attached and partially with the help of a mask exposed and then partially removed, leaving a longitudinal stripe with a width of 375 µm which extends over one side of the element. Of the uncovered part of the body contains a small portion of each anodized area of the element parts. A dielectric layer such as an epoxy resin layer is used now attached in such a way that it covers the exposed surface part, wherein the resin is adapted to have a layer 3 to 4 µm thick.

Fig. 6 shows a top view of the body after the attachment of the Epoxy resin strip 12 and detaching the photore-sist strip.

Another layer of photoresist is then put over the whole surface the body 4 and the substrate 1, including the printed feedthrough contact pattern, appropriate. The photoresist layer is exposed using a mask and when the exposed part is then loosened, this creates openings in the Photoresist layer formed. These openings contain holes of 40 / µm x 25 / µm, extending over the p-type regions 9, and strips with a width of 40 / urn extending from these areas over the epoxy resin layer and over the ladders 3 extend. Close to the other Longitudinal edge of the Element 4 is a strip-shaped opening with a width of 1 mm in the photoresist layer present and also extends over the adjacent edge of the common lead-through conductor 2 over 0.55mm.

A gold layer with a thickness of 0.5 / µm is now produced by sputtering deposited over the whole surface.

The deposited gold extends into the openings in the photoresist layer in contact with the different exposed areas and layers. That Gold deposited on the photoresist is removed by a removal technique ("lift-off") removed by dissolving the remaining photoresist. Fig. Figure 7 shows a top view of the structure after the excess gold has been removed. Ten gold bands 15 each extend at one end in contact with an n-type conductor Surface area 9 and at the other end in contact with a feed-through conductor 3. A single gold band 16 extends into contact with the top surface of the p-conductive body 4 and in contact with the common lead-through conductor 2.- The bands 15 are each against an underlying part of the p-type body part insulated by the presence of the epoxy resin layer 12.

In this way, a linear configuration becomes VOll in a simple manner ten elements existing pjiotovoltaic detector formed. As a power amplifier in the iters te ilunt :; before encapsulating the configuration, it may be desirable to the whole structure easy to etch to the properties after removal of a thin Layer of some i-units from the surface of the assembly to improve.

It is evident that there are many variations in the way of editing, particularly with regard to the method of contacting after the formation of the pn transitions, are possible, so with such a modification according to tier formation of the tTbergaiig and the removal of the anodiscilen () surface clicllt hurried new ones anodic surface layer locally on every sensitive area appropriate, which, however, lies within the limit of each pn junction where the junction mentioned ends on the surface. In this way a protective layer is formed which, it has been found that the properties of the detector are at least improved to that extent the possible deterioration of the properties when the arrangement temperatures is subjected to 70 0C, is not perceived. When using this modification The further contacting of the n-conductive areas takes place via the last one attached anodic layer formed openings.

A further modification will now be described with reference to FIG. 9, in which the previously described embodiment is modified such that a linear configuration of photoconductive detector elements in a common body is formed. The arrangement includes a ceramic substrate 21 with a corresponding arranged pattern of printed feedthrough contacts 22, 23.

The element has the same external dimensions as the n-conducting Areas 29 of 200 µm x 100 µm. Each n-type region 29 is on opposite one another Sides contacted by strips 35 and 36, each extending over the p-type body part extend and are isolated from this part by an epoxy layer 32. the Strips 35 extend into contact with feed conductor 23 and the stripes 36 contact the joint implementation manager 22.

It is evident that many other modifications can be made within the scope of the invention possible are. For example, if the surface layer with the conduction type reversing Agents produced by anodizing, other solutions, e.g. sodium carbonate, as well as the carbonates and bicarbonates of lithium and potassium can be used. Instead of To produce the said layer by anodizing can be a kind of natural oxide are generated with an excess of the doping material by chemical conversion, for example, an oxidizing solution such as hydrogen peroxide is used. It was found that at treatment of mercury cadmium telluride bodies formed with such a solution and subsequent heating pn junctions extending under the generated surface oxide layer.

In the described embodiments, the conversion of the Conduction type in an area bordering the surface. Within the scope of the invention but the method can be used to create buried areas, their Conduction type is opposite to that of the surrounding material.

A further development of the method is now based on another Embodiment described which is a modification of the on the basis of FIGS is the procedure described. In this embodiment, the starting material is composition and the wafer production exactly the same up to and including the polishing and Etching step to produce a wafer 200 µm thick. The procedure This disc then differs in that it is then in a sealed capsule is heated, which further contains an excess of mercury. The heating takes place at 250 ° C for one hour. This is due to the diffusion of mercury a surface layer with a depth of 10 μm with n-type properties generated at 77 ° K. The n-type layer is completely covered by one main surface Polishing removed while nearly 2 µm by etching from the opposite one Surface is removed. The body in the form of a p-type (770K) disc with an n-type surface layer (77 K) is then added to that in the preceding Embodiment described way treated to make element body parts more desired Sizes, e.g. 3 mm x 1 mm, as in the embodiment described above, to be generated, but each has an n-conductive surface layer with a thickness of almost 8 μm contain. The process is also completely the same as long as the electrolytic anodizing treatment carried out in the same way and in areas greater than the final desired sensitive areas are to leave room for the formation of a later applied insulating layer, e.g.

an epoxy resin layer over one side of the transition to be formed and also to get a contact area.

After the electrolytic anodization, the during the anodization used photoresist mask is removed and is heated at 18000 during 1 hour. This has the consequence that the uncovered part of the n-leading Surface is converted back into material with p-conductive properties. Before Mercury diffused in these areas becomes in this heating step diffused out. However, if the parts of the n-type surface layer under the anodically generated surface layer 7 remain n-conductive and their depth is almost remains, it turns out that the surface layer 7 firstly as a Outdiffusion mask against mercury outdiffusion and further as a local source of mercury serves for the further diffusion of mercury. The latter property is based on the assumption that without such an additional localized source of mercury the previously diffused mercury concentration in the body when heated at such a temperature, namely 1800C, are dispersed for one hour would.

Claims (11)

PATENT CLAIMS: Method for producing an infrared radiation detector arrangement, at least part of a surface of a body of mercury cadmium telluride is subjected to a conversion treatment to form a surface layer on the To produce bodies, after which a heating step is carried out, characterized in that, that the surface layer produced by said conversion treatment is a Contains sufficient amounts of an element withdrawn from this body to be used as a Source to serve for reintroduction of said element into said body, this element being part of said body and such that, when there is an excess concentration in the material of said body is present, the properties at the operating temperature of the detector arrangement n-type material can be obtained, and that said surface layer heated to a temperature above 100 ° C. during said heating step is to incorporate an amount of said element from the surface layer to introduce the underlying area of the body, thereby creating a pn junction in the body is formed. 2. The method according to claim 1, characterized in that the surface layer on mercury cadmium telluride, which is produced at the operating temperature of the Arrangement has the properties of p-type material, and that the heating step causes the underlying area to have the properties of n-type material the operating temperature of the arrangement elvhs during the adjacent part of the said Body maintains the p-type properties to the pn junction in the body to build. 3. The method according to claim 1, characterized in that the surface layer on mercury cadmium telluride, which is produced at the operating temperature of the Arrangement has the properties of n-type material, and that the heating step causes the underlying area to retain the n-type properties, in that said element is introduced from said surface layer becomes, while the adjacent part of the body by the heating step in material with converted p-type properties at the operating temperature of the arrangement whereby the pn junction is formed in the body. 4. The method according to claim 3, characterized in that, before the surface layer is generated, mercury in at least one surface of the Body made of mercury cadmium telluride is diffused at the operating temperature the arrangement has the properties of p-conductive material, whereby a to the Surface bordering part of the body is formed, which is at the operating temperature the arrangement has the properties of n-conductive material; that the surface layer is generated on the part adjacent to the surface, and that the heating step a diffusion of mercury from an exposed part of the to the surface bordering part causes the part in material with the p-type properties convert at the operating temperature of the arrangement. 5. The method according to any one of the preceding claims, characterized in, that during the heating step the surface layer locally on a part One main surface of the body is present and the underlying area with n-type conductors Properties brought about by the aforementioned introduction of the element, only locally adjoins the main surface, so that the pn junction formed extends up to extends to the main surface such that it is at least partially on the main surface ends. 6 forfeiture according to one of the preceding claims, through this characterized in that during the heating step the periphery of the surface layer on a major surface of the body is such that at least most of the formed pn junction extends almost parallel to the main surface and the photosensitive pn junction of a photovoltaic infrared detection element the detector arrangement forms. 7. The method according to claims 5 and 6, characterized in that during the heating step, the surface layer has the shape of a configuration has separate parts on said main surface, so that a configuration island-shaped areas with the properties of n-type material in a common Body part with the properties of p-type material is formed while after after the heating step, each n-type region is provided with a conductive connection and the p-type body part having at least one common conductive terminal is provided. 8. The method according to claim 5, characterized in that during of the heating step, the surface layer takes the shape of a configuration more separately Has parts on the main surface, so that a configuration to the surface bordering island-shaped n-type areas in a common p-type body part is formed, while after the heating step, each n-type region with in some distance from each other first and second conductive terminals is provided to a photoconductive infrared detector element of the detector assembly to build. 9. The method according to any one of claims 5, 7 and 8, or according to claim 6, if dependent on claim 5, characterized in that after the heating step at least an edge part of the surface layer which is in the vicinity of the site extends, at which the pn-Ubergallz ends at the main surface, is removed. 10. Verfailren according to claim 9, characterized gelicnllzeicllnet that after the surface layer after the heating step is removed, a Etching treatment is performed to remove material from the major surface, and at least a part of the main surface that extends from the end part of the pn junction to the Area is limited, is electrolytically anodized. 11. The method according to any one of the preceding claims, characterized in, that the conversion treatment for creating the surface layer with the element consists of the electrolytic anodization of the mercury cadmium telluride, after which the body at a temperature in the range of 125 C - 2700C for a period is heated in the range from 100 seconds up to 40 hours in order to achieve the pn junction form.