CA1110421A - Cadmium mercury telluride sputtering targets - Google Patents
Cadmium mercury telluride sputtering targetsInfo
- Publication number
- CA1110421A CA1110421A CA316,105A CA316105A CA1110421A CA 1110421 A CA1110421 A CA 1110421A CA 316105 A CA316105 A CA 316105A CA 1110421 A CA1110421 A CA 1110421A
- Authority
- CA
- Canada
- Prior art keywords
- cadmium mercury
- mercury telluride
- finely divided
- die
- compact
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
- 229910000661 Mercury cadmium telluride Inorganic materials 0.000 title claims abstract description 44
- MCMSPRNYOJJPIZ-UHFFFAOYSA-N cadmium;mercury;tellurium Chemical compound [Cd]=[Te]=[Hg] MCMSPRNYOJJPIZ-UHFFFAOYSA-N 0.000 title claims abstract description 44
- 238000005477 sputtering target Methods 0.000 title claims abstract description 21
- 239000002245 particle Substances 0.000 claims abstract description 30
- 238000000034 method Methods 0.000 claims abstract description 21
- 239000000203 mixture Substances 0.000 claims abstract description 18
- 230000001427 coherent effect Effects 0.000 claims abstract description 13
- 238000009826 distribution Methods 0.000 claims description 6
- 238000002360 preparation method Methods 0.000 claims description 6
- 238000002156 mixing Methods 0.000 claims description 5
- 239000000463 material Substances 0.000 description 5
- 239000000758 substrate Substances 0.000 description 5
- XKRFYHLGVUSROY-UHFFFAOYSA-N Argon Chemical compound [Ar] XKRFYHLGVUSROY-UHFFFAOYSA-N 0.000 description 4
- 238000003491 array Methods 0.000 description 4
- 238000005549 size reduction Methods 0.000 description 4
- 238000004544 sputter deposition Methods 0.000 description 4
- 150000001875 compounds Chemical class 0.000 description 3
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 description 2
- 229910052786 argon Inorganic materials 0.000 description 2
- 238000005336 cracking Methods 0.000 description 2
- 239000013078 crystal Substances 0.000 description 2
- 238000004519 manufacturing process Methods 0.000 description 2
- 239000000843 powder Substances 0.000 description 2
- 238000003825 pressing Methods 0.000 description 2
- 229910052710 silicon Inorganic materials 0.000 description 2
- 239000010703 silicon Substances 0.000 description 2
- 229910004262 HgTe Inorganic materials 0.000 description 1
- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 description 1
- 150000001768 cations Chemical class 0.000 description 1
- 238000005056 compaction Methods 0.000 description 1
- 230000006835 compression Effects 0.000 description 1
- 238000007906 compression Methods 0.000 description 1
- 238000002425 crystallisation Methods 0.000 description 1
- 230000008025 crystallization Effects 0.000 description 1
- 238000011067 equilibration Methods 0.000 description 1
- 230000001747 exhibiting effect Effects 0.000 description 1
- 238000000227 grinding Methods 0.000 description 1
- 150000002500 ions Chemical class 0.000 description 1
- 239000000155 melt Substances 0.000 description 1
- 238000010587 phase diagram Methods 0.000 description 1
- 238000001953 recrystallisation Methods 0.000 description 1
- 230000035945 sensitivity Effects 0.000 description 1
- 238000005245 sintering Methods 0.000 description 1
- 238000001931 thermography Methods 0.000 description 1
- 239000010409 thin film Substances 0.000 description 1
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 1
Classifications
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
- C01B19/00—Selenium; Tellurium; Compounds thereof
- C01B19/007—Tellurides or selenides of metals
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
- B22F3/00—Manufacture of workpieces or articles from metallic powder characterised by the manner of compacting or sintering; Apparatus specially adapted therefor ; Presses and furnaces
- B22F3/02—Compacting only
-
- C—CHEMISTRY; METALLURGY
- C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
- C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
- C23C14/00—Coating by vacuum evaporation, by sputtering or by ion implantation of the coating forming material
- C23C14/22—Coating by vacuum evaporation, by sputtering or by ion implantation of the coating forming material characterised by the process of coating
- C23C14/34—Sputtering
- C23C14/3407—Cathode assembly for sputtering apparatus, e.g. Target
- C23C14/3414—Metallurgical or chemical aspects of target preparation, e.g. casting, powder metallurgy
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L31/00—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
- H01L31/0248—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof characterised by their semiconductor bodies
- H01L31/0256—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof characterised by their semiconductor bodies characterised by the material
- H01L31/0264—Inorganic materials
- H01L31/0296—Inorganic materials including, apart from doping material or other impurities, only AIIBVI compounds, e.g. CdS, ZnS, HgCdTe
- H01L31/02966—Inorganic materials including, apart from doping material or other impurities, only AIIBVI compounds, e.g. CdS, ZnS, HgCdTe including ternary compounds, e.g. HgCdTe
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
- C01P2004/00—Particle morphology
- C01P2004/60—Particles characterised by their size
- C01P2004/61—Micrometer sized, i.e. from 1-100 micrometer
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
- C01P2006/00—Physical properties of inorganic compounds
- C01P2006/10—Solid density
Landscapes
- Chemical & Material Sciences (AREA)
- Organic Chemistry (AREA)
- Engineering & Computer Science (AREA)
- Mechanical Engineering (AREA)
- Inorganic Chemistry (AREA)
- Condensed Matter Physics & Semiconductors (AREA)
- General Physics & Mathematics (AREA)
- Materials Engineering (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Physics & Mathematics (AREA)
- Manufacturing & Machinery (AREA)
- Electromagnetism (AREA)
- Metallurgy (AREA)
- Computer Hardware Design (AREA)
- Microelectronics & Electronic Packaging (AREA)
- Power Engineering (AREA)
- Physical Vapour Deposition (AREA)
- Crystals, And After-Treatments Of Crystals (AREA)
- Powder Metallurgy (AREA)
- Bipolar Transistors (AREA)
Abstract
ABSTRACT OF THE DISCLOSURE
Embodiments of a method are disclosed for producing large size cadmium mercury telluride (CMT) sputtering targets of a homogeneous composition. Sputter-ing targets of CMT having a general formula CdxHg1-xTe wherein x has values in the range of about 0.14 to 0.60 are prepared by compacting finely divided CMT of a particle size smaller than 150 µ in a die into a coherent compact having a density of at least 97% theoretical density. CMT
with an x value of about 0.14 to about 0.20 preferably is compacted at a die preheat temperature of about 100 to 300°C and at a compacting pressure of at least about 400 MPa. CMT having an x value of about 0.20 to about 0.60 preferably is compacted at a die preheat temperature of about 300°C and a compacting pressure of about 160 to 275 MPa.
The die may be evacuated to a pressure of less than about 133 Pa absolute prior to compacting.
Embodiments of a method are disclosed for producing large size cadmium mercury telluride (CMT) sputtering targets of a homogeneous composition. Sputter-ing targets of CMT having a general formula CdxHg1-xTe wherein x has values in the range of about 0.14 to 0.60 are prepared by compacting finely divided CMT of a particle size smaller than 150 µ in a die into a coherent compact having a density of at least 97% theoretical density. CMT
with an x value of about 0.14 to about 0.20 preferably is compacted at a die preheat temperature of about 100 to 300°C and at a compacting pressure of at least about 400 MPa. CMT having an x value of about 0.20 to about 0.60 preferably is compacted at a die preheat temperature of about 300°C and a compacting pressure of about 160 to 275 MPa.
The die may be evacuated to a pressure of less than about 133 Pa absolute prior to compacting.
Description
Q9~2~
This invention relates to a method for producing large size cadmium mercury telluride sputtering targets of a homogeneous composition.
Cadmium mercury telluride, referred to as CMT here-inafter, is a continuous series of ternary compounds having the general formula of CdxHgl xTe wherein x has values of between zero and one. Compounds exhibiting semi-conducting properties have values of x in the range of about 0.14 to about 1. Semi-conducting compounds of CMT find application in the solid-state electronics industry in, for example, infrared detectors.
Presently, the most advanced type of material avail-able for infrared detectors is linear array detector strips made rom bulk single crystal material and measuring about 20 mm by 1.5 mm or less. These monolithic arrays are made from bulk CMT and may contain up to 200 elements depending on the homogeneity and size of the bulk CMT available. The manu-facture of arrays with a higher number of elements is too complex to be handled by methods normally used ~or connecting the elements to the external electronics.
A simpler and potentially less expensive system could be obtained by switching from a linear array to a focal plane array which resembles, for instance, the solid-state, charge coupled device (CCD) television camera operating in the visible light range. The CCD approach makes use o~ a multi-plexing function, i.e. the data from the focal plane array are obtained in a multiplex form so that individual element leads are not required with the focal plane system, whereas they are required with linear arrays. A focal plane array, therefore, makes it possible to use, for example, 1,000 or more elements, resulting in much simpler scanning or no scanning at all while retaining the high resolution and extreme sensitivity that are required for sophisticated thermal imaging.
~o~
Although the feasihility of multiplexing CMT with a silicon CCD has been demonstrated, there is presently no practical method known whereby a focal plane array i~n CMT can be prepared which possesses the required extreme homog,eneiky of composition and the required electrical parameters. However, sputtering, one of the thin-film techniques whereby a thin layer of C~lT is deposited on a suitable substrate, such as for example silicon, may make it possible to make focal plane arrays with the required extreme homogeneity and a compatibility with multiplexing.
Sputtering is used to grow thin layers onto substrates epitaxially,i.e., the crystal orientation of the substrate is continued into the epitaxial layer, This is carried out in a chamber which i8 maintained under a partial vacuum and in which a sputtering target of the material to be deposite~ i~ mounted on a water or air-cooled holder or backing plate. ~ heam o ions, for example argon, from an RF generator or a glow-discharge gun, is directed onto the target and causes sputtering of surface material from the target. The liberated material deposits on one or more suitable substrates arranged at a distance about the sputtering target. The epitaxial layer deposited by sputtering on the substrate has essentially the same composition as that of the target. In the case of CMT it is essential that the targets possess extreme homogeneity in composition, Sputtering targets are used in a variety of siæes and shapes, but the sizes of sputtering targets made of CMT are limited because of the difficulty of preparing CMT which has the required homogeneity. The methods for preparing CMT with a homogeneous composition are usually processes involving crystalli-zation and these methods are limited by the constrictions imposed by the CdTe-HgTe phase diagram, viz., the large temperature difference between the solidus and liquidus lines and the high pressures involved at the higher values for x, the latter especi-ally requiring sophisticated and consequently expensive equipment~
This invention relates to a method for producing large size cadmium mercury telluride sputtering targets of a homogeneous composition.
Cadmium mercury telluride, referred to as CMT here-inafter, is a continuous series of ternary compounds having the general formula of CdxHgl xTe wherein x has values of between zero and one. Compounds exhibiting semi-conducting properties have values of x in the range of about 0.14 to about 1. Semi-conducting compounds of CMT find application in the solid-state electronics industry in, for example, infrared detectors.
Presently, the most advanced type of material avail-able for infrared detectors is linear array detector strips made rom bulk single crystal material and measuring about 20 mm by 1.5 mm or less. These monolithic arrays are made from bulk CMT and may contain up to 200 elements depending on the homogeneity and size of the bulk CMT available. The manu-facture of arrays with a higher number of elements is too complex to be handled by methods normally used ~or connecting the elements to the external electronics.
A simpler and potentially less expensive system could be obtained by switching from a linear array to a focal plane array which resembles, for instance, the solid-state, charge coupled device (CCD) television camera operating in the visible light range. The CCD approach makes use o~ a multi-plexing function, i.e. the data from the focal plane array are obtained in a multiplex form so that individual element leads are not required with the focal plane system, whereas they are required with linear arrays. A focal plane array, therefore, makes it possible to use, for example, 1,000 or more elements, resulting in much simpler scanning or no scanning at all while retaining the high resolution and extreme sensitivity that are required for sophisticated thermal imaging.
~o~
Although the feasihility of multiplexing CMT with a silicon CCD has been demonstrated, there is presently no practical method known whereby a focal plane array i~n CMT can be prepared which possesses the required extreme homog,eneiky of composition and the required electrical parameters. However, sputtering, one of the thin-film techniques whereby a thin layer of C~lT is deposited on a suitable substrate, such as for example silicon, may make it possible to make focal plane arrays with the required extreme homogeneity and a compatibility with multiplexing.
Sputtering is used to grow thin layers onto substrates epitaxially,i.e., the crystal orientation of the substrate is continued into the epitaxial layer, This is carried out in a chamber which i8 maintained under a partial vacuum and in which a sputtering target of the material to be deposite~ i~ mounted on a water or air-cooled holder or backing plate. ~ heam o ions, for example argon, from an RF generator or a glow-discharge gun, is directed onto the target and causes sputtering of surface material from the target. The liberated material deposits on one or more suitable substrates arranged at a distance about the sputtering target. The epitaxial layer deposited by sputtering on the substrate has essentially the same composition as that of the target. In the case of CMT it is essential that the targets possess extreme homogeneity in composition, Sputtering targets are used in a variety of siæes and shapes, but the sizes of sputtering targets made of CMT are limited because of the difficulty of preparing CMT which has the required homogeneity. The methods for preparing CMT with a homogeneous composition are usually processes involving crystalli-zation and these methods are limited by the constrictions imposed by the CdTe-HgTe phase diagram, viz., the large temperature difference between the solidus and liquidus lines and the high pressures involved at the higher values for x, the latter especi-ally requiring sophisticated and consequently expensive equipment~
- 2 -For example, preparation of in~ots of CMT by the melt re-crystal- -lization process involves temperatures of 700 and 800C at a pressure of about 4000 KPa for CdxHgl xTe wherein x - 0.2 and of 800 and 950~C at 8000 KPa for CdxHgl xTe wherein x = 0.5. Conse-quently, ingots so prepared have a diameter usually not larger than about 15 mm and only portions of the ingots are of sufficiently homogeneous composition to allow preparation of sputtering targets such as are obtained by slicing CMT ingots perpendicular to the axis of the ingot or by slicing strips of C~IT from the ingot along the isocomposition lines. ~ence, the present limitation of the size of linear array aetector strips of about 20 mm by 1.5 mm or less~ unless mosaic patterns with complex lap-joint~ are used.
~ le have now found that CMT sputterin~ targ~3ts of rela~
tiv~ly large s~æ~, i.e., 9.~Ze~ larger than heretoEore possible, can be made by size reduction o~ C~T to obtain finely divided C.~IT
and compression of the finely divided CMT into compacts of desired large dimensions. Thus, C~IT sputtering targets of a desired composition of crlT are prepared hy compacting finely divided C~lT
of similar composition and contained in a die under the application of a compacting pressure suitable to produce a coherent compact of CMT.
~ ccordin~ly, there is provided a method for the prepara-tion of sputtering targets of cadmium mercury telluride of the general formula CdxHgl xTe wherein x has values in the range of about 0.14 to 0.60 which comprises the steps of preparing finely divided cadmium mercury telluride of desired composition, said finely divided cadmium mercury telluride having particle sizes all less than 150 ~, mixing the particles of the finely clivided cadmium mercury telluride to obtain a substantially even particle size distribution, adding a predetermined amount of the mixed 42~
particles to a die of desired dimensions~ applying a compactiny pressure to said amount to compact the finely divided cadmium mercury telluride into a coherent compact having a density of at least 97% of theoretical density~ releasing the pressure and removing the compact having predetermined dimensions rom the die, said predetermined amount of mixed particles being sufficient to form said compact of predetermined dimensions.
According to a second embodiment of the invention,there ; 10 is provided a method si.milar to that of the first embodiment but the values of x are restricted to the range of from about 0O14 up to about 0.20~the die is preheated to a temperature in the rangé of about 100 to 300C and the compacting pressure is at least about 400 MPa, ~ccording to a third embodiment of the invention~ there is provided a method ~im~lar to that of the first embodiment, but the values of x are restricted to the range of from about 0.20 to about 0.60, the die is preheated to a temperature of about 300C and the compacting pr~ssure is in the range of about 160 to 275 ~IPa.
According to other embodiments there are provided Sputtering targets of coherent compacts of cadmium mercury tellu-ride prepared according to the f~rst, second and third embodiment.
Finely divided CMT may be single or poly-crystalline and may be prepared by size reduction of ingots or portions thereof, of slices, or of other forms of CMT. Preferably, the CMT has a composition wherein x has values in the range of about 0,14 to 0.60. The sources of the finely divided CMT should be of homogeneous composition, but slight variations in composition may be allowable as such variations tend to disappear, i.e.
average out! in the final composition of the compact. The particle 4;2~
sizes of the finely divided CMT should extend over a range of sizes so that maximum density for the compacted CMT is obtained.
~article sizes of the finely divided CMT all less than 150 ~
(micron) are generally fine enough to ensure the required density of the compact. The preferred range of palrticle sizes is from 150 to 44 ~. The size reduction is achieved by known methods such as by grinding or crushing. If desired, the size reduction -is performed under an inert or reducing at:mosphere, such as, for example, an atmosphere of argon or hydrogen gas.
The finely divided CMT is thoroughly mixed to obtain a substantially even particle size distribution. A predetermined amount of the mixed CMT is added to a die of such form that a compact with the desired dimensions will be o~tained. The CMT
i8 pre~erably ~dded at room temperature to avoid dcterioration o~ the CMT. Th~ die is subjectecl to pressure usincJ a ~ui~able, commercially available press. The die may be at room temperature or may have been preheated before applying pressure. ~lso, the die containing the C~T may be evacuated to a suitably low pressure before applying compacting pressure. Preferahly, preheated, evacuated dies are used. It :is to he understood that multi-cavity dies can be used.
Although ~ood qu~lity compacts have been obtainecl with dies at room temperature, as well as with dies that have not been evacuated, the best results have been obtained by preheating the die to a temperature of up to about 3noocr adding the pre-determined amount of mixed, finely divided crlT at room temperature to the preheated die, and evacuating the die with the contained CMT to pressures of less than about 133 ~a absolute. The com-pacting pressures applied to the die, i.e., to compact the mixed, finely divided CMT~ should be sufficient to provide a coherent compact of high density and sufficient physical strength. ~hen using dies at room temperature (about 20C), compacting pressures of at least about 4Q0 ~IPa are required to ~produce compacts which have a density of at least 97% of theoretical density. Preferably, compacting pressures are in the range of about 400 to 1100 MPa (about 30 to 80 tons per square inch). However, compacts so produced show some cracking. We have found that, for CMT compo-sitions wherein x is in the range of from about 0.14 up to about 0,20, when dies are preheated to a temperature in the range of about 100 to 300C and evacuated to pressures of less than about 133 Pa absolute, compacting pressures in the preferred range produce compacts which are substantially free of cracks and have a density which i8 u5Ually higher th~n 98~ o theoretical densitys the hl~her the temperatllre o the preheated die ancl ~he hlgher the compacting pressure, the higher the density o the compact.
We have also found that, when finely divided CMT with a compo-sition wherein x equals 0.20 or higher, i.e~ x = 0.20 to x = 0.~0, is added at room temperature to preheated dies and the die is evacuated prior to applying compacting pressure, the compacting pressures are limited.
In the range of compositions wherein x has values in the range of from about 0.20 to about 0.60, the die must be preheated to a relatively high temperature in order to obtain strong coherent compacts. The density of the compact increases with increasing temperature, the best results being obtained with dies preheated to about 300C, and with increasing compacting pressure, the best results being obtained with compacting pressures in the ranye of about 160 to 275 MPa (about 12 to 20 tons per square inch). The compacts thus produced are substantially free of cracks. At compacting pressures above ~bout 275 MPa small cracks are present in the compacts when they are removed Q4Z~L
from the die and the cracking becomes progressively severe with increasing pressure, i.e., cracks first develop laterally in planes perpendicular to the axis of the compact and then radially and finally the compact becomes incoherent.
In all cases, compacting pressures should be applied for a period of time of not less than about one minute to produce strong, coherent compacts. When CMT at room temperature is added to a preheated die, a temperature equilibration period of about one to three minutes should be allowed. The steps of equilibra-ting, evacuating and applying pressure may be executed in succes-sion or almost simultaneously. After the application o pressure for the desired length of time, the pressure is released and the compact is removed from the die Sintering of the compacts is not necessary because the compacts have a density which i5 at least 97% of theoretical density and in most cases higher than 98~, and possess the necessary physical strength. The compact, as removed from the die, can be used as such for a sputtering target, or if desired, may be cut, lapped and polished prior to use as a sputtering target.
The invention will now be illustrated by the following non-limitative examples.
Example 1 45 g of high purity, poly-crystalline Cdxrlgl xTe (x = O.lS) powder at room temperature and having particle sizes all less than 150 ~u were added to a 38 mm diameter die, which had been preheated to a temperature of 2Q0C. The die was closed, evacuated to a pressure of less than 133 Pa and subjected to a compacting pressure of 690 MPa ~50 tons per square inch). ~fter three minutes the pressure was released and the resulting disc removed from the die. The compacted disc, measuring 38 mm in diameter and 5 mm thick, was free of cracks, had smooth surfaces and had a density of 99~ of theoretical density.
Exam~le 2 The test described in Example 1 was repeated but the die was preheated to 100C. A compacted disc of the same dimensions, free of cracks and having a density of 99% of theoretical density, was obtained.
Example 3 The test described in ~xample 1 was repeated but the die ~Jas preheated to a temperature of 50C. A compacted disc of the same dimensions and having a density of 99% of theoretical density was obtained. The compact showed a number of small cracks, which did not affect the coherence of the compact.
Example 4 The test described in Example 1 was repeated but a 19 mm diameter die preheated to 100C was used, the die was not evacuated pxior to appl~cation of pressure and the pressure during compaction was 940 MPa (68 tons per square inch). A compacted cylinder measuring 19 mm in diameter and 20 mm thick, free of cracks and having a density of 99% of theoretical density was obtained.
Example 5 The test described in Example 1 was repeated but with Cdxl~g 1 ~e powder wherein x had a value of 0.55; the die was not pre-heated.
A disc of the same dimensions and a density of 98.5~ was obtained.
The disc showed some cracks.
It can be seen from Examples 1, 2 and 4, using dies preheated to a temperature of at least 100C, that substantially crack-free compacts of large diameter and thickness and having a density of 99% of theoretical density can be made from finely divided CMT wherein x is about 0.15. Examples 3 and 5 show that, when x has a value above 0.20 or the dies is at a tempera-ture below 100C, large compacts of high denisty can be obtained but the compacts are not free of cracks.
Example 645 g portions at room temperatuxe of finely divided, high purity poly-crystalline CMT where x had a value in the range of 0 a 20 to 0.60 were compacted at varying compacting pressures in a die having a diameter of 38 mm which was preheated to a temperature Of 300C and evacuated to less than 133 Pa absolute. The compact-ing pressure was applied for a period of three minutes immediately after closing and while evacuating the die, After removal from the die~ the compacts, measuring 38 mm diameter and 5 mm thick, were inspected and their density determined. The results are given in Table I.
TADLE I
Value Compacting Den~ity as ~ Result o of x vressure in MPa of theoretical X
.. _ 0.20 165 97 free of cracks 0.20 207 98.0 free of cracks 0.20 234 98.5 free of cracks 0.20 276 99.3 free of cracks 20 0.20 345 - some lateral cracks 0.20 386 - some radial cracks 0.32 234 98.5 free of cxacks 0.32 276 99.5 some small cracks 0.40 276 99.5 some small cracks 0.60 207 98.2 free of cracks 0.60 276 99.2 some small cracks ~ s can be seen from the results of ~xample 6,compacts free of cracks and having densities of at least 97~ of theore-tical density can be made by compressing finely divided CMT
with x values in the range of 0.20 to 0.60 into forms of large diameter and thickness using compacting pressures in ~he range of 160 to 275 MPa and dies preheated to 300C.
11~(19L2~
It will be understood of course that modificationscan be made in the embodiment of the invention illustrated and described herein without departing from the scope and purview of the invention as defined by the appended claims.
~ le have now found that CMT sputterin~ targ~3ts of rela~
tiv~ly large s~æ~, i.e., 9.~Ze~ larger than heretoEore possible, can be made by size reduction o~ C~T to obtain finely divided C.~IT
and compression of the finely divided CMT into compacts of desired large dimensions. Thus, C~IT sputtering targets of a desired composition of crlT are prepared hy compacting finely divided C~lT
of similar composition and contained in a die under the application of a compacting pressure suitable to produce a coherent compact of CMT.
~ ccordin~ly, there is provided a method for the prepara-tion of sputtering targets of cadmium mercury telluride of the general formula CdxHgl xTe wherein x has values in the range of about 0.14 to 0.60 which comprises the steps of preparing finely divided cadmium mercury telluride of desired composition, said finely divided cadmium mercury telluride having particle sizes all less than 150 ~, mixing the particles of the finely clivided cadmium mercury telluride to obtain a substantially even particle size distribution, adding a predetermined amount of the mixed 42~
particles to a die of desired dimensions~ applying a compactiny pressure to said amount to compact the finely divided cadmium mercury telluride into a coherent compact having a density of at least 97% of theoretical density~ releasing the pressure and removing the compact having predetermined dimensions rom the die, said predetermined amount of mixed particles being sufficient to form said compact of predetermined dimensions.
According to a second embodiment of the invention,there ; 10 is provided a method si.milar to that of the first embodiment but the values of x are restricted to the range of from about 0O14 up to about 0.20~the die is preheated to a temperature in the rangé of about 100 to 300C and the compacting pressure is at least about 400 MPa, ~ccording to a third embodiment of the invention~ there is provided a method ~im~lar to that of the first embodiment, but the values of x are restricted to the range of from about 0.20 to about 0.60, the die is preheated to a temperature of about 300C and the compacting pr~ssure is in the range of about 160 to 275 ~IPa.
According to other embodiments there are provided Sputtering targets of coherent compacts of cadmium mercury tellu-ride prepared according to the f~rst, second and third embodiment.
Finely divided CMT may be single or poly-crystalline and may be prepared by size reduction of ingots or portions thereof, of slices, or of other forms of CMT. Preferably, the CMT has a composition wherein x has values in the range of about 0,14 to 0.60. The sources of the finely divided CMT should be of homogeneous composition, but slight variations in composition may be allowable as such variations tend to disappear, i.e.
average out! in the final composition of the compact. The particle 4;2~
sizes of the finely divided CMT should extend over a range of sizes so that maximum density for the compacted CMT is obtained.
~article sizes of the finely divided CMT all less than 150 ~
(micron) are generally fine enough to ensure the required density of the compact. The preferred range of palrticle sizes is from 150 to 44 ~. The size reduction is achieved by known methods such as by grinding or crushing. If desired, the size reduction -is performed under an inert or reducing at:mosphere, such as, for example, an atmosphere of argon or hydrogen gas.
The finely divided CMT is thoroughly mixed to obtain a substantially even particle size distribution. A predetermined amount of the mixed CMT is added to a die of such form that a compact with the desired dimensions will be o~tained. The CMT
i8 pre~erably ~dded at room temperature to avoid dcterioration o~ the CMT. Th~ die is subjectecl to pressure usincJ a ~ui~able, commercially available press. The die may be at room temperature or may have been preheated before applying pressure. ~lso, the die containing the C~T may be evacuated to a suitably low pressure before applying compacting pressure. Preferahly, preheated, evacuated dies are used. It :is to he understood that multi-cavity dies can be used.
Although ~ood qu~lity compacts have been obtainecl with dies at room temperature, as well as with dies that have not been evacuated, the best results have been obtained by preheating the die to a temperature of up to about 3noocr adding the pre-determined amount of mixed, finely divided crlT at room temperature to the preheated die, and evacuating the die with the contained CMT to pressures of less than about 133 ~a absolute. The com-pacting pressures applied to the die, i.e., to compact the mixed, finely divided CMT~ should be sufficient to provide a coherent compact of high density and sufficient physical strength. ~hen using dies at room temperature (about 20C), compacting pressures of at least about 4Q0 ~IPa are required to ~produce compacts which have a density of at least 97% of theoretical density. Preferably, compacting pressures are in the range of about 400 to 1100 MPa (about 30 to 80 tons per square inch). However, compacts so produced show some cracking. We have found that, for CMT compo-sitions wherein x is in the range of from about 0.14 up to about 0,20, when dies are preheated to a temperature in the range of about 100 to 300C and evacuated to pressures of less than about 133 Pa absolute, compacting pressures in the preferred range produce compacts which are substantially free of cracks and have a density which i8 u5Ually higher th~n 98~ o theoretical densitys the hl~her the temperatllre o the preheated die ancl ~he hlgher the compacting pressure, the higher the density o the compact.
We have also found that, when finely divided CMT with a compo-sition wherein x equals 0.20 or higher, i.e~ x = 0.20 to x = 0.~0, is added at room temperature to preheated dies and the die is evacuated prior to applying compacting pressure, the compacting pressures are limited.
In the range of compositions wherein x has values in the range of from about 0.20 to about 0.60, the die must be preheated to a relatively high temperature in order to obtain strong coherent compacts. The density of the compact increases with increasing temperature, the best results being obtained with dies preheated to about 300C, and with increasing compacting pressure, the best results being obtained with compacting pressures in the ranye of about 160 to 275 MPa (about 12 to 20 tons per square inch). The compacts thus produced are substantially free of cracks. At compacting pressures above ~bout 275 MPa small cracks are present in the compacts when they are removed Q4Z~L
from the die and the cracking becomes progressively severe with increasing pressure, i.e., cracks first develop laterally in planes perpendicular to the axis of the compact and then radially and finally the compact becomes incoherent.
In all cases, compacting pressures should be applied for a period of time of not less than about one minute to produce strong, coherent compacts. When CMT at room temperature is added to a preheated die, a temperature equilibration period of about one to three minutes should be allowed. The steps of equilibra-ting, evacuating and applying pressure may be executed in succes-sion or almost simultaneously. After the application o pressure for the desired length of time, the pressure is released and the compact is removed from the die Sintering of the compacts is not necessary because the compacts have a density which i5 at least 97% of theoretical density and in most cases higher than 98~, and possess the necessary physical strength. The compact, as removed from the die, can be used as such for a sputtering target, or if desired, may be cut, lapped and polished prior to use as a sputtering target.
The invention will now be illustrated by the following non-limitative examples.
Example 1 45 g of high purity, poly-crystalline Cdxrlgl xTe (x = O.lS) powder at room temperature and having particle sizes all less than 150 ~u were added to a 38 mm diameter die, which had been preheated to a temperature of 2Q0C. The die was closed, evacuated to a pressure of less than 133 Pa and subjected to a compacting pressure of 690 MPa ~50 tons per square inch). ~fter three minutes the pressure was released and the resulting disc removed from the die. The compacted disc, measuring 38 mm in diameter and 5 mm thick, was free of cracks, had smooth surfaces and had a density of 99~ of theoretical density.
Exam~le 2 The test described in Example 1 was repeated but the die was preheated to 100C. A compacted disc of the same dimensions, free of cracks and having a density of 99% of theoretical density, was obtained.
Example 3 The test described in ~xample 1 was repeated but the die ~Jas preheated to a temperature of 50C. A compacted disc of the same dimensions and having a density of 99% of theoretical density was obtained. The compact showed a number of small cracks, which did not affect the coherence of the compact.
Example 4 The test described in Example 1 was repeated but a 19 mm diameter die preheated to 100C was used, the die was not evacuated pxior to appl~cation of pressure and the pressure during compaction was 940 MPa (68 tons per square inch). A compacted cylinder measuring 19 mm in diameter and 20 mm thick, free of cracks and having a density of 99% of theoretical density was obtained.
Example 5 The test described in Example 1 was repeated but with Cdxl~g 1 ~e powder wherein x had a value of 0.55; the die was not pre-heated.
A disc of the same dimensions and a density of 98.5~ was obtained.
The disc showed some cracks.
It can be seen from Examples 1, 2 and 4, using dies preheated to a temperature of at least 100C, that substantially crack-free compacts of large diameter and thickness and having a density of 99% of theoretical density can be made from finely divided CMT wherein x is about 0.15. Examples 3 and 5 show that, when x has a value above 0.20 or the dies is at a tempera-ture below 100C, large compacts of high denisty can be obtained but the compacts are not free of cracks.
Example 645 g portions at room temperatuxe of finely divided, high purity poly-crystalline CMT where x had a value in the range of 0 a 20 to 0.60 were compacted at varying compacting pressures in a die having a diameter of 38 mm which was preheated to a temperature Of 300C and evacuated to less than 133 Pa absolute. The compact-ing pressure was applied for a period of three minutes immediately after closing and while evacuating the die, After removal from the die~ the compacts, measuring 38 mm diameter and 5 mm thick, were inspected and their density determined. The results are given in Table I.
TADLE I
Value Compacting Den~ity as ~ Result o of x vressure in MPa of theoretical X
.. _ 0.20 165 97 free of cracks 0.20 207 98.0 free of cracks 0.20 234 98.5 free of cracks 0.20 276 99.3 free of cracks 20 0.20 345 - some lateral cracks 0.20 386 - some radial cracks 0.32 234 98.5 free of cxacks 0.32 276 99.5 some small cracks 0.40 276 99.5 some small cracks 0.60 207 98.2 free of cracks 0.60 276 99.2 some small cracks ~ s can be seen from the results of ~xample 6,compacts free of cracks and having densities of at least 97~ of theore-tical density can be made by compressing finely divided CMT
with x values in the range of 0.20 to 0.60 into forms of large diameter and thickness using compacting pressures in ~he range of 160 to 275 MPa and dies preheated to 300C.
11~(19L2~
It will be understood of course that modificationscan be made in the embodiment of the invention illustrated and described herein without departing from the scope and purview of the invention as defined by the appended claims.
Claims (9)
1. A method for the preparation of substantially crack-free sputtering targets of cadmium mercury telluride of the general formula CdxHg1-xTe wherein x has values in the range of about 0.14 to 0.60 which comprises the steps of preparing finely divided cadmium mercury telluride of desired composition, said finely divided cadmium mercury telluride having particle sizes all less than 150 µ, mixing the particles of the finely divided cadmium mercury telluride to obtain a substantially even particle size distribution, preheating a die of desired dimensions to a temperature in the range of about 100 to 300°C, adding a predetermined amount of mixed particles to said die, evacuating the die to a pressure of less than about 133 Pa absolute, applying a compacting pressure to said amount for a period of time not less than about one minute to compact the finely divided cadmium mercury telluride into a coherent compact having a density of at least 97% of theoretical density, releasing the pressure and removing the compact having predetermined dimensions from the die, said predetermined amount of mixed particles being sufficient to form said compact of predeter-mined dimensions.
2. A method for the preparation of sputtering targets as claimed in Claim 1, in which the cadmium mercury telluride has a general formula CdxHg1-xTe wherein x has values in the range of from about 0.14 up to about 0.20, applying a compacting pressure to said amount of at least about 400 MPa to compact the finely divided cadmium mercury telluride into a coherent compact substantially free of cracks.
3. A method for the preparation of sputtering targets as claimed in Claim 1, in which the cadmium mercury telluride has a general formula CdxHg1-xTe wherein x has values in the range of from about 0.20 to about 0.60, preheating the die of desired dimensions to a temperature of about 300°C, and applying compacting pressures to said amount in the range of 160 to 275 MPa to compact the finely divided cadmium mercury telluride into a coherent compact substantially free of cracks.
4. A method as claimed in Claim 1, 2 or 3, wherein the particle sizes of the finely divided cadmium mercury telluride are in the range of about 150 to 44 µ.
5. A method as claimed in Claim 1 or 2, wherein the compacting pressure is in the range of about 400 to 1100 MPa.
6. Sputtering targets consisting of compacts of cadmium mercury telluride prepared according to the method of Claim 1, 2 or 3.
7. Sputtering targets of coherent compacts of cadmium mercury telluride having a density of at least 97% of theoretical density and substantially free of cracks prepared according to the method comprising the steps of preparing finely divided cadmium mercury telluride of the general formula CdxHg1-xTe wherein x has a value in the range of about 0.14 to 0.60, said finely divided cadmium mercury telluride having particle sizes all less than 150 µ, mixing the particles of the finely divided cadmium mercury telluride to obtain a substantially even particle size distribution, adding a predetermined amount of mixed particles of the finely divided cadmium mercury telluride to a die of desired dimensions preheated to a temperature in the range of about 100 to 300°C, evacuating said die to a pressure of less than about 133 Pa absolute, applying a compacting pressure for a period of time of not less than one minute to compact the finely divided cadmium mercury telluride, releasing the pressure and removing the compact having predetermined dimensions from the die, said predetermined amount of mixed particles being sufficient to form said compact of predetermined dimensions.
8. Sputtering targets of coherent compacts of cadmium mercury telluride having a density of at least 97%
of theoretical density and substantially free of cracks prepared according to the method comprising the steps of preparing finely divided cadmium mercury telluride of the general formula CdxHg1-xTe wherein x has a value in the range of from about 0.14 to about 0.20, said finely divided cadmium mercury telluride having particle sizes all less than 150 µ, mixing the particles of the finely divided cadmium mercury telluride to obtain a substantially even particle size distribution, preheating a die of desired dimensions to a temperature in the range of about 100 to 300°C, adding a predetermined amount of mixed particles of the finely divided cadmium mercury telluride to the preheated die, evacuating said die to a pressure of less than about 133 Pa absolute, applying a compacting pressure in the range of about 400 to 1100 MPa for a period of time not less than one minute to compact the finely divided cadmium mercury telluride, releasing the pressure and removing the compact having predetermined dimensions from the die, said predetermined amount of mixed particles being sufficient to form said compact of predetermined dimensions.
of theoretical density and substantially free of cracks prepared according to the method comprising the steps of preparing finely divided cadmium mercury telluride of the general formula CdxHg1-xTe wherein x has a value in the range of from about 0.14 to about 0.20, said finely divided cadmium mercury telluride having particle sizes all less than 150 µ, mixing the particles of the finely divided cadmium mercury telluride to obtain a substantially even particle size distribution, preheating a die of desired dimensions to a temperature in the range of about 100 to 300°C, adding a predetermined amount of mixed particles of the finely divided cadmium mercury telluride to the preheated die, evacuating said die to a pressure of less than about 133 Pa absolute, applying a compacting pressure in the range of about 400 to 1100 MPa for a period of time not less than one minute to compact the finely divided cadmium mercury telluride, releasing the pressure and removing the compact having predetermined dimensions from the die, said predetermined amount of mixed particles being sufficient to form said compact of predetermined dimensions.
9. Sputtering targets of coherent compacts of cadmium mercury telluride having a density of at least 97% of theo-retical density and substantially free of cracks prepared according to the method comprising the steps of preparing finely divided cadmium mercury telluride of the general formula CdxHg1-xTe wherein x has a value in the range of from about 0.20 to about 0.60, said finely divided cadmium mercury telluride having particle sizes all less than 150 µ, mixing the particles of the finely divided cadmium mercury telluride to obtain a substantially even particle size distribution, preheating a die of desired dimensions to a temperature of about 300°C, adding a predetermined amount of mixed particles of the finely divided cadmium mercury telluride to the preheated die, evacuating said die to a pressure of less than about 133 Pa absolute, applying a compacting pressure in the range of about 160 to 275 MPa for a period of time of not less than one minute to compact the finely divided cadmium mercury telluride, releasing the pressure and removing the compact having predetermined dimensions from the die, said predetermined amount of mixed particles being sufficient to form said compact of predetermined dimensions.
Priority Applications (5)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA316,105A CA1110421A (en) | 1978-11-09 | 1978-11-09 | Cadmium mercury telluride sputtering targets |
| GB7936723A GB2037264B (en) | 1978-11-09 | 1979-10-23 | Cadmium mercury telluride sputtering targets |
| DE19792944482 DE2944482A1 (en) | 1978-11-09 | 1979-11-03 | STACKABLE TARGET AND METHOD FOR THE PRODUCTION THEREOF |
| JP14343979A JPS5565338A (en) | 1978-11-09 | 1979-11-07 | Sputtering target of telluric mercury cadmium and its manufacture |
| FR7927738A FR2441582A1 (en) | 1978-11-09 | 1979-11-09 | PROCESS FOR PREPARING LARGE-SIZED CATHODE VAPORIZATION TARGETS AND HOMOGENEOUS COMPOSITION IN MERCURY AND CADMIUM TELLURIDE |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA316,105A CA1110421A (en) | 1978-11-09 | 1978-11-09 | Cadmium mercury telluride sputtering targets |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1110421A true CA1110421A (en) | 1981-10-13 |
Family
ID=4112934
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA316,105A Expired CA1110421A (en) | 1978-11-09 | 1978-11-09 | Cadmium mercury telluride sputtering targets |
Country Status (5)
| Country | Link |
|---|---|
| JP (1) | JPS5565338A (en) |
| CA (1) | CA1110421A (en) |
| DE (1) | DE2944482A1 (en) |
| FR (1) | FR2441582A1 (en) |
| GB (1) | GB2037264B (en) |
Families Citing this family (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| IL60734A (en) * | 1979-08-30 | 1984-03-30 | Santa Barbara Res Center | Production of single crystal mercury cadmium telluride |
| DE3300525A1 (en) * | 1983-01-10 | 1984-07-12 | Merck Patent Gmbh, 6100 Darmstadt | TARGETS FOR CATHOD SPRAYING |
| DE3627775A1 (en) * | 1986-08-16 | 1988-02-18 | Demetron | METHOD FOR PRODUCING TARGETS |
Family Cites Families (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| FR2265872B1 (en) * | 1974-03-27 | 1977-10-14 | Anvar |
-
1978
- 1978-11-09 CA CA316,105A patent/CA1110421A/en not_active Expired
-
1979
- 1979-10-23 GB GB7936723A patent/GB2037264B/en not_active Expired
- 1979-11-03 DE DE19792944482 patent/DE2944482A1/en active Granted
- 1979-11-07 JP JP14343979A patent/JPS5565338A/en active Pending
- 1979-11-09 FR FR7927738A patent/FR2441582A1/en active Granted
Also Published As
| Publication number | Publication date |
|---|---|
| JPS5565338A (en) | 1980-05-16 |
| DE2944482C2 (en) | 1988-09-08 |
| FR2441582B1 (en) | 1985-04-19 |
| FR2441582A1 (en) | 1980-06-13 |
| DE2944482A1 (en) | 1980-05-29 |
| GB2037264A (en) | 1980-07-09 |
| GB2037264B (en) | 1982-09-29 |
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