CN118280824A - Method for thickening metal after SiC ohmic contact - Google Patents
Method for thickening metal after SiC ohmic contact Download PDFInfo
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- 239000002184 metal Substances 0.000 title claims abstract description 163
- 229910052751 metal Inorganic materials 0.000 title claims abstract description 163
- 238000000034 method Methods 0.000 title claims abstract description 51
- 230000008719 thickening Effects 0.000 title claims abstract description 25
- 239000010410 layer Substances 0.000 claims abstract description 182
- 239000011241 protective layer Substances 0.000 claims abstract description 89
- 238000004519 manufacturing process Methods 0.000 claims abstract description 30
- 238000000137 annealing Methods 0.000 claims abstract description 14
- 238000001312 dry etching Methods 0.000 claims abstract description 7
- 238000001039 wet etching Methods 0.000 claims abstract description 7
- 229910000990 Ni alloy Inorganic materials 0.000 claims description 20
- 238000000151 deposition Methods 0.000 claims description 20
- 230000008021 deposition Effects 0.000 claims description 19
- 238000004544 sputter deposition Methods 0.000 claims description 11
- 238000001704 evaporation Methods 0.000 claims description 10
- 230000001681 protective effect Effects 0.000 claims description 7
- 229910045601 alloy Inorganic materials 0.000 claims description 5
- 239000000956 alloy Substances 0.000 claims description 5
- 238000009713 electroplating Methods 0.000 claims description 4
- 230000000694 effects Effects 0.000 abstract description 9
- HBMJWWWQQXIZIP-UHFFFAOYSA-N silicon carbide Chemical compound [Si+]#[C-] HBMJWWWQQXIZIP-UHFFFAOYSA-N 0.000 description 68
- 229910010271 silicon carbide Inorganic materials 0.000 description 68
- 238000005520 cutting process Methods 0.000 description 8
- 238000005452 bending Methods 0.000 description 6
- 238000010586 diagram Methods 0.000 description 5
- 239000000463 material Substances 0.000 description 5
- 230000003064 anti-oxidating effect Effects 0.000 description 3
- 230000004048 modification Effects 0.000 description 3
- 238000012986 modification Methods 0.000 description 3
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 2
- PXHVJJICTQNCMI-UHFFFAOYSA-N Nickel Chemical compound [Ni] PXHVJJICTQNCMI-UHFFFAOYSA-N 0.000 description 2
- 238000004364 calculation method Methods 0.000 description 2
- 229910052799 carbon Inorganic materials 0.000 description 2
- 238000010438 heat treatment Methods 0.000 description 2
- 238000001556 precipitation Methods 0.000 description 2
- 239000004065 semiconductor Substances 0.000 description 2
- 229910001218 Gallium arsenide Inorganic materials 0.000 description 1
- 229910010038 TiAl Inorganic materials 0.000 description 1
- 238000004458 analytical method Methods 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 230000015556 catabolic process Effects 0.000 description 1
- 238000001816 cooling Methods 0.000 description 1
- 230000007797 corrosion Effects 0.000 description 1
- 238000005260 corrosion Methods 0.000 description 1
- 230000005684 electric field Effects 0.000 description 1
- 238000005530 etching Methods 0.000 description 1
- 229910052737 gold Inorganic materials 0.000 description 1
- 230000017525 heat dissipation Effects 0.000 description 1
- 150000002739 metals Chemical class 0.000 description 1
- 229910052759 nickel Inorganic materials 0.000 description 1
- 238000007254 oxidation reaction Methods 0.000 description 1
- 102220062245 rs1800369 Human genes 0.000 description 1
- 229910052710 silicon Inorganic materials 0.000 description 1
- 239000002344 surface layer Substances 0.000 description 1
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L21/00—Processes or apparatus adapted for the manufacture or treatment of semiconductor or solid state devices or of parts thereof
- H01L21/02—Manufacture or treatment of semiconductor devices or of parts thereof
- H01L21/04—Manufacture or treatment of semiconductor devices or of parts thereof the devices having potential barriers, e.g. a PN junction, depletion layer or carrier concentration layer
- H01L21/0445—Manufacture or treatment of semiconductor devices or of parts thereof the devices having potential barriers, e.g. a PN junction, depletion layer or carrier concentration layer the devices having semiconductor bodies comprising crystalline silicon carbide
- H01L21/048—Making electrodes
- H01L21/0485—Ohmic electrodes
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L21/00—Processes or apparatus adapted for the manufacture or treatment of semiconductor or solid state devices or of parts thereof
- H01L21/02—Manufacture or treatment of semiconductor devices or of parts thereof
- H01L21/04—Manufacture or treatment of semiconductor devices or of parts thereof the devices having potential barriers, e.g. a PN junction, depletion layer or carrier concentration layer
- H01L21/50—Assembly of semiconductor devices using processes or apparatus not provided for in a single one of the subgroups H01L21/06 - H01L21/326, e.g. sealing of a cap to a base of a container
- H01L21/56—Encapsulations, e.g. encapsulation layers, coatings
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Abstract
The invention discloses a method for thickening metal after SiC ohmic contact, which comprises the following steps: step S100: manufacturing a metal layer on the front surface or the back surface of the SiC wafer, and forming ohmic contact after annealing; step S200: manufacturing a protective layer on the metal layer; step S300: removing at least part of the protective layer to form a residual protective layer; step S400: and manufacturing a thickened metal layer on the residual protective layer. According to the invention, the protective layer is arranged outside the metal layer, so that the metal layer can be protected from other subsequent process in the subsequent process, and even if the protective layer is oxidized, the wet etching or dry etching can be used for removing the oxidized part of the protective layer, the removal process is strong in controllability and good in stability, the adhesion effect of the subsequent thickened metal layer is not influenced, and the damage to the electrical property of the SiC device is reduced.
Description
Technical Field
The invention relates to the technical field of SiC ohmic contact metal thickening, in particular to a method for thickening metal after SiC ohmic contact.
Background
SiC (silicon carbide) is one of the wide bandgap semiconductor materials that has been rapidly developed over the last decade. Compared with widely applied semiconductor materials Si, ge and GaAs, the SiC material has the advantages of wide forbidden band, high breakdown electric field, high carrier saturation drift rate, high heat conductivity, high power density and the like, and is an ideal material for preparing high-temperature, high-power and high-frequency devices. Low specific contact resistance and high stability are two important factors that determine SiC device performance. Therefore, in order to fully exert the performance advantages of SiC devices, the fabrication process of the ohmic contacts and electrodes in the SiC device fabrication process has a very important position.
Currently, in SiC (silicon carbide) devices, ni (nickel) alloy is generally used as an ohmic contact metal, and after the Ni alloy is deposited on the surface of the SiC wafer, good ohmic contact is formed after high-temperature annealing at a temperature of up to 1000 ℃. However, the Ni alloy layer is easy to have bad appearance such as roughness and oxidization and is not easy to be removed due to the Ni alloy and other subsequent technological processes, the thickened metal layer is not firmly adhered in the subsequent metal thickening process, the thickened metal layer falls off, the ohmic contact layer deforms, the electrical performance of the SiC device is damaged, and potential reliability hazards are generated.
In view of these problems, a generally conventional solution is to wet etch the Ni alloy layer, mainly with two drawbacks: (1) The Ni alloy layer is loose and easy to oxidize, and the oxidized part of the Ni alloy layer cannot be well removed by wet corrosion; (2) The consistency of the oxidized part of the Ni alloy layer is poor, so that the removal process is difficult to control, the contact effect of ohmic contact or the adhesion effect or deformation of a subsequent thickened metal layer can be influenced by the instability of the removal process, the electrical performance of the SiC device is damaged, and potential reliability hazards are generated. Therefore, it is very important to develop a new SiC metal thickening process.
Disclosure of Invention
Based on the above, the present invention provides a method for thickening metal after ohmic contact of SiC, which aims to solve the above technical problems partially or completely, and the present invention is realized by the following technical solutions:
A method for thickening metal after SiC ohmic contact comprises the following steps:
Step S100: manufacturing a metal layer on the front surface or the back surface of the SiC wafer, and forming ohmic contact after annealing;
step S200: manufacturing a protective layer on the metal layer;
Step S300: removing at least part of the protective layer to form a residual protective layer;
Step S400: manufacturing a thickened metal layer on the residual protective layer;
wherein, the thickness relation of metal layer, surplus protective layer, thickening metal layer satisfies:
P=P1+P2，1.0≤P≤8.0；
P1=λ1（E1×D1)/(E×D4)+λ2（E2×D3)/(E×D4)；
P2=λ3（E1×D1)/(E2×D3)；
Wherein P is the total deformation, P1 is the first deformation, and P2 is the second deformation;
D1 is the thickness of the metal layer, E1 is the linear expansion coefficient of the metal layer, λ1 is a first deformation adjustment coefficient, and is related to the linear expansion coefficients of the metal layer and the thickened metal layer; d3 is the thickness of the residual protective layer, E2 is the linear expansion rate of the residual protective layer, λ2 is a second deformation adjustment coefficient, and is related to the linear expansion rates of the residual protective layer and the thickened metal layer; d4 is the thickness of the thickened metal layer; e is the linear expansion rate of the thickened metal layer, and lambda 3 is the third deformation adjustment coefficient, and is related to the linear expansion rates of the metal layer and the residual protection layer.
Optionally, in step S200, the thickness of the protective layer is D2, which satisfies the following requirements: a1 is less than or equal to D2/D1 is less than or equal to A2, A1 is less than or equal to 0.25 and less than or equal to 0.4, A2 is less than or equal to 0.5 and less than or equal to 5.0, D3/D2 is less than or equal to 0 and less than or equal to A3, D1+ D3 is less than or equal to D4, A3 is less than or equal to 0.5, and A1, A2 and A3 are all set constants.
Optionally, the protective layer includes a first film layer and a second film layer, where the thickness of the first film layer is D21, and the thickness of the second film layer is D22, and meets the following requirements: the sum of D21 and D22 is equal to D2, and the first film layer is connected with the metal layer and the second film layer, so that the following conditions are satisfied: d21 =d3, D22/D1 is equal to or less than A4,0.1 is equal to or less than A4 is equal to or less than 0.8, and A4 is a set constant.
Optionally, the thickness D1 of the metal layer has a value ranging from: and the numerical range of the thickness D2 of the protective layer is that: 10nm or more and 2000nm or less; the numerical range of the thickness D3 of the residual protective layer is as follows: more than 0 and less than or equal to 1000nm; the numerical range of the thickness D4 of the thickened metal layer is as follows: more than 50nm and less than or equal to 6000nm.
Optionally, in the step S100, a layer of Ni alloy is deposited on the back or front of the SiC wafer, and annealing is performed to form a Ni alloy layer with a thickness of D1, where the Ni alloy layer with a thickness of D1 is used as a metal layer to complete ohmic contact fabrication of SiC.
Optionally, in the step S100, the deposition temperature T1 is 25 degrees to 400 degrees, and the annealing time S1 is: 5min-15min, the deposition mode is as follows: evaporating or sputtering.
Optionally, in the step S200, the protective layer with a thickness D2 is deposited on the metal layer at a temperature T2 of 25-400 degrees by: evaporating or sputtering.
Optionally, in the step S200, the protective layer is a metal protective film, where the metal includes Al, ti, tiAl alloy.
Optionally, in the step S300, the remaining protection layer with a thickness D3 is formed by etching away at least part of the protection layer by wet etching or dry etching.
Optionally, in the step S400, the thickened metal layer with the thickness of D4 is deposited on the remaining protective layer at a temperature T3 of 25-400 degrees by: evaporating, sputtering and electroplating.
The beneficial technical effects of the invention are as follows:
(1) The thickness D1 of the metal layer, the thickness D2 of the protective layer, the thickness D3 of the residual protective layer and the thickness D4 of the thickened metal layer on the whole SiC device meet the following conditions ：A1≤D2/D1≤A2,0.25≤A1≤0.4,0.6≤A2≤5.0,0<D3/D2≤A3,D1+D3≤D4,0<A3≤0.5,D21=D3,D22/D1≤A4,0.1≤A4≤0.8,A1、A2、A3、A4 as set constants, so that the protective layer cannot be too thin to exert a protective effect, the deposition time can be prevented from being increased as much as possible, the time for removing the protective layer can be influenced by the too thick protective layer, the time for removing the protective layer can be reduced on the whole, the manufacture of the thickened metal layer is ensured, and the yield and the production efficiency of SiC ohmic contact and the manufacture of the thickened metal layer are improved.
(2) On the basis that the SiC device meets the conditions, the relation among the metal layer, the residual protection layer and the thickened metal layer of the SiC device on the whole also meets the following conditions: p=p1+p2, 1.0.ltoreq.p.ltoreq.8.0, p1=λ1 (e1×d1)/(e×d4) +λ2 (e2×d3)/(e×d4), and p2=λ3 (e1×d1)/(E2×d3), whereby the risk of deformation or deformation possibly occurring in the process of shrinkage or subsequent cutting and grooving of the SiC device can be reduced, the risk of deformation or deformation amount of deformation occurring in the entirety of the metal layer, the remaining protective layer, and the thickened metal layer of the SiC device can be reduced, and the heat conduction, electromagnetic shielding, and the overall mechanical strength of the SiC device can be ensured.
(3) The protective layer is arranged outside the metal layer, the metal layer can be protected from other subsequent process in the subsequent process, the protective layer can be etched away by wet etching or dry etching even if the protective layer is oxidized, the oxidized part of the protective layer is highly controlled in the removal process, the stability is good, the contact effect of the finished ohmic contact and the adhesion effect of the subsequent thickened metal layer can not be influenced by the removal process, and the damage to the electrical property of the SiC device is reduced.
Drawings
FIG. 1 is a schematic diagram of a structure of SiC ohmic contact in a method of metal thickening after SiC ohmic contact according to the present invention;
FIG. 2 is a schematic diagram of a structure of a protective layer fabricated after SiC ohmic contact in the method of metal thickening after SiC ohmic contact according to the present invention;
FIG. 3 is a schematic structural diagram of a residual protection layer formed by removing part of the protection layer after SiC ohmic contact in the method for thickening metal after SiC ohmic contact according to the present invention;
Fig. 4 is a schematic structural diagram of a thickened metal layer manufactured after removing part of a protective layer after SiC ohmic contact to form a residual protective layer in the method for thickening metal after SiC ohmic contact according to the present invention.
Fig. 5 is a schematic structural diagram of a protective layer in a method of metal thickening after SiC ohmic contact according to the present invention.
Detailed Description
In order to make the objects, technical solutions and advantages of the embodiments of the present disclosure more apparent, the embodiments of the present disclosure will be further described in detail below with reference to the accompanying drawings and embodiments; it should be understood that the specific embodiments described herein are merely illustrative of the disclosed embodiments and are not intended to limit the disclosed embodiments;
The structures, proportions, sizes, etc. shown in the drawings are for the purpose of understanding and reading by those skilled in the art, and are not intended to limit the applicable scope of the invention, so that any structural modifications, proportional changes, or dimensional adjustments should not be construed as essential to the invention, but should not affect the efficacy or achievement of the invention; also, the terms "and," "or" and the like recited in the present specification are for convenience of description only and are not intended to limit the scope of the invention, which is defined by the terms "and," "or" and the like, but rather are to be construed as being within the scope of the invention without any substantial modification to the technical content thereof; in addition, the embodiments of the present application are not independent of each other, but can be combined;
The terms "first," "second," and "third" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance or implicitly indicating the number of technical features indicated; thus, a feature defining "a first", "a second", "a third" may include one or more such features, either explicitly or implicitly; in the description of the present application, unless otherwise indicated, the meaning of "a plurality" is two or more;
As shown in fig. 1-5, the present application provides a method for thickening metal after SiC ohmic contact, comprising the following steps:
Step S100: manufacturing a metal layer 20 on the front surface or the back surface of the SiC wafer 10, and forming ohmic contact after annealing;
In some embodiments, a layer of Ni alloy is deposited on the back or front side of the SiC wafer and annealed to form a layer of Ni alloy with a thickness D1, the layer of Ni alloy with a thickness D1 being used as the metal layer 20 to complete ohmic contact fabrication of SiC;
specifically, the deposition temperature T1 is 25-400 degrees, and the annealing time S1 is: 5min-15min, the deposition mode is as follows: evaporating or sputtering, the numerical range of the thickness D1 is as follows: 50nm or more and 600nm or less.
The deposition temperature T1 may be 25 degrees, 30 degrees, 40 degrees, 50 degrees, 60 degrees, 70 degrees, 80 degrees, 90 degrees, 100 degrees, 150 degrees, 200 degrees, 250 degrees, 300 degrees, 350 degrees, 400 degrees, or may be a range between two values, which may be set by a skilled person according to the actual situation, and the present application is not limited to this.
The annealing time S1 can be 5min-15min, which can be 5min, 6min, 7min, 8min, 9min, 10min, 11min, 12min, 13min, 14min and 15min, or can be a numerical range between every two of the above values, and the technical personnel can set the values according to the actual situation, which is not set by the application.
The thickness D1 may be 50nm, 60nm, 70nm, 80nm, 90nm, 100nm, 150nm, 200nm, 250nm, 300nm, 350m, 400nm, 450nm, 500nm, 550nm, 600nm, or may be in a range between two values, which the skilled person can set according to the actual situation, and the present application is not limited to.
Thus, the Ni alloy layer with the thickness D1 and the temperature T1 of the deposition and the time S1 of the annealing can be arranged, so that ohmic contact manufacture of SiC can be well completed, and good ohmic contact can be formed.
Preferably, the deposition temperature T1 is 400 ℃, the annealing time is 8min-10min, and in the 1000 ℃ rapid annealing of the Ni alloy with the thickness of 100nm-120nm, the Ni alloy does not react with SiC entirely, the Ni alloy with the surface layer not reacting with SiC is also relatively dense, and carbon precipitation can be prevented, and at this time, blackening carbon precipitation on the back or front of the SiC wafer 10 cannot be observed or detected.
Step S200: manufacturing a protective layer 30 on the metal layer 20;
In some embodiments, a protective layer 30 of thickness D2 is deposited on the metal layer 20.
Specifically, the deposition temperature T2 is 25-400 degrees, and the deposition method is as follows: evaporating or sputtering, the numerical range of the thickness D2 is: 10nm or more and 2000nm or less.
The deposition temperature T2 may be 25 degrees, 50 degrees, 75 degrees, 100 degrees, 125 degrees, 150 degrees, 175 degrees, 200 degrees, 250 degrees, 300 degrees, 350 degrees, 400 degrees, or may be a range between two values, which the skilled person can set according to the actual situation, and the present application is not limited to.
The value of the thickness D2 may be 10nm、20nm、30nm、40nm、50nm、60nm、70nm、80nm、90nm、100nm、150nm、200nm、250nm、300nm、400nm、500nm、600nm、700nm、800nm、900nm、1000nm、1100nm、1200nm、1300nm、1400nm、1500nm、1600nm、1700nm、1800nm、1900nm、2000nm, or may be a range between two values, which the skilled person can set according to the actual situation, which the present application does not set.
In some embodiments, any protective layer may be contemplated. Illustratively, the protective layer 30 is a metal protective film, and the metal includes Al, ti, tiAl alloy, and the like, and is an Al film, a Ti film, a TiAl alloy film, and the like, so that the influence of a post-process on the metal protective film can be avoided, and the stability of the metal protective film is ensured. Of course, other metals are also possible, and the skilled person can set this according to the actual situation, and the application does not set this.
In some embodiments, as shown in fig. 4, the thickness D2 of the protective layer 30, the thickness D1 of the metal layer, satisfy: a1 is less than or equal to D2/D1 is less than or equal to A2 and is less than or equal to 0.25 and less than or equal to A1 is less than or equal to 0.4,0.5 is less than or equal to A2 and less than or equal to 5.0, A1 and A2 are set constants, specifically, the set constants A1 can be 0.25, 0.3 and 0.4, the set constants A2 can be 0.5, 0.6, 0.7, 0.8, 0.9, 1.0, 1.5, 2.0, 2.5, 3.0, 3.5 and 4.0, and a technician can set the set constants A1 and the set constants A2 according to actual conditions, and the application is not limited to the set constants.
The thickness D2 of the protective layer and the thickness D1 of the metal layer are set in a relation, so that the protective layer 30 cannot be too thin to exert a protective effect, the deposition time can be increased due to the fact that the protective layer 30 is too thick, the time for removing the protective layer to form the residual protective layer 40 can be prevented from being influenced, and the yield and the production efficiency of SiC ohmic contact and thickened metal layer manufacture are integrally influenced.
In some embodiments, as shown in fig. 5, the protective layer 30 includes a first film 31 and a second film 32, where the first film has a thickness D21 and the second film has a thickness D22, so as to satisfy the following conditions: the sum of D21 and D22 is equal to D2, and the first film 31 connects the metal layer 31 and the second film 32.
In some embodiments, the first film 31 is deposited at a temperature of 25 degrees to 400 degrees by: evaporating or sputtering, wherein the thickness of the deposited first film 31 is D21; likewise, the second film 32 is deposited at a temperature of 25 degrees to 400 degrees by: evaporated or sputtered, the second film 32 is deposited to a thickness D22.
In some embodiments, the following are satisfied: d21 By setting the constant of 0.1 to 0.8 and 0.1 to 0.4, the method can avoid the first film 31 being too thin to ensure that the first film 31 can play the role of anti-oxidation protection, and can avoid the second film 32 being too thick, can properly reduce the time for removing at least part of the protection layer and ensure the manufacture of the thickened metal layer 50, can simultaneously satisfy the requirements of anti-oxidation protection and removal of at least part of the protection layer, namely, the first film 31 with the thickness of D21 plays the role of anti-oxidation protection (can correspond to the time of D21 to be equal to D3), can correspondingly remove the second film 32 with the thickness of D22 when at least part of the protection layer is removed, can reduce the time for removing the protection layer partially, can more conveniently ensure the manufacture of the thickened metal layer 50, and can properly improve the production efficiency of SiC ohmic contact and the manufacture of the thickened metal layer
Step S300: removing at least a portion of the protective layer to form a remaining protective layer 40;
In some embodiments, wet etching or dry etching may be used to etch away at least a portion of the protective layer.
In some embodiments, removing at least a portion of the protective layer forms a remaining protective layer 40 having a thickness D3, the thickness D3 ranging in value from: 0 to 1000nm. Specifically, the value of the thickness D3 may be 0nm, 100nm, 200nm, 300nm, 400nm, 500nm, 600nm, 700nm, 800nm, 900nm, 1000nm, or may be a range between two values, which the skilled person can set according to the actual situation, and the present application does not set. Thus, at least part of the protective layer is arranged in the wet etching or dry etching process, and the protective layer can be used for manufacturing a thickened metal layer later so as to ensure the overall size requirement of the whole SiC device.
Step S400: a thickened metal layer 50 is formed over the remaining protective layer 40.
In some embodiments, thickened metal layer 50, formed of a thickened metal, may be used to protect the metal layer, may also be used to protect the remaining protective layer, may also be used to increase the thermal conductivity (e.g., heat dissipation) and electromagnetic shielding properties of the SiC device, and may also be used to provide additional or integral structural support to the SiC device, increasing the overall (e.g., mechanical) structural strength of the SiC device.
In some embodiments, any thickening process, thickening the metal layer, may be considered. Illustratively, the thickened metal layer may be thickened by deposition, sputtering, electroplating, or the like. The thickened metal layer comprises Au, ag and NiAu, niAg, tiNiAu, tiNiAg, which can be reasonably set by a technician according to actual conditions, and the thickened metal layer is not set in the embodiment of the application.
In some embodiments, the deposition temperature T3 is 25-400 degrees, and the deposition is performed by: evaporating, sputtering and electroplating, wherein the numerical range of the thickness D4 is as follows: more than 50nm and less than or equal to 6000nm.
The deposition temperature T3 may be 25 degrees, 30 degrees, 40 degrees, 50 degrees, 60 degrees, 70 degrees, 80 degrees, 90 degrees, 100 degrees, 150 degrees, 200 degrees, 250 degrees, 300 degrees, 350 degrees, 400 degrees, or may be a range between two values, which may be set by a skilled person according to the actual situation, and the present application is not limited thereto.
The thickness D4 may be 51nm, 60nm, 80nm, 100nm, 1000nm, 1500nm, 2000nm, 2500nm, 3000nm, 3500nm, 4000nm, 4500nm, 5000nm, 5500nm, 6000nm, or may be in a range between two values, which the skilled person can set according to the actual situation, and the present application is not limited to.
In some embodiments, as shown in fig. 4, the thickness D2 of the protective layer, the thickness D1 of the metal layer, the thickness D3 of the remaining protective layer 40, the thickness of the thickened metal layer satisfy: 0< D3/D2 is less than or equal to A3, D1+D3 is less than or equal to D4,0< A3 is less than or equal to 0.5, and obviously when D3 is not equal to 0, the time for removing at least part of the protective layer can be shortened, the manufacture of the thickened metal layer 50 is ensured, the excessive thickness of the protective layer 30 can be avoided, the deposition time is increased, and the yield and the production efficiency of SiC ohmic contact and the manufacture of the thickened metal layer are further influenced as a whole.
However, on the basis of forming the residual protection layer 40, in the subsequent actual thickening process of the thickened metal layer 50, the metal layer 20 is located on the upper side of the residual protection layer 40, the thickened metal layer 50 is located on the lower side of the residual protection layer 40, in the thickening process of the thickened metal layer 50, the deposition temperature (which may mean heating to a high temperature) is cooled, and even when the subsequent SiC wafer is subjected to the processing such as cutting wheel cutting or laser grooving, cutting, the material, thickness, area and expansion system of the metal layer 20 are different from those of the thickened metal layer 50, and the thickness, area and expansion coefficient, which may cause the risk of deformation or deformation of the SiC device, for example, a part of gaps exist between at least two of the metal layer 20, the residual protection layer 40 and the thickened metal layer 50 or the whole of the SiC device may have cracks, so that the electromagnetic shielding and the whole mechanical strength of the SiC device may be reduced, and the thickness, the area and the like of the thickened metal layer 50 need to be reasonably set correspondingly to reduce or avoid the risk of deformation or deformation of the SiC device.
In some embodiments, if the thickness D1 of the metal layer 20 is too large in the SiC device, when the SiC device is subjected to post-heating cooling, cutting by a cutter wheel or laser grooving, cutting, and other processing, the thermal expansion of the metal layer 20 is increased, and if the thickness D1 of the metal layer 20 is greater than the thickness D4 of the thickened metal layer 50, the thermal expansion of the metal layer 20 is greatly affected, so that deformation is generated, which may cause cracks or fissures in the remaining protection layer 30, and affect the ohmic contact effect of the SiC device. Accordingly, the thickness D4 of the thickened metal layer 50 needs to be equal to or greater than the sum of the thickness D1 of the metal layer 20 and the thickness D3 of the residual protection layer 40, so that the difference of the expansion stress between the front and the back of the thickened metal layer 50 becomes a factor of main deformation along the vertical direction from the thickened metal layer 50 to the metal layer 20, and further, possible deformation risks of the metal layer 20 and the residual protection layer 40 or the influence of the deformation on the metal layer 20 or the thickened metal layer 50 can be reduced.
In some embodiments, in metal layer 20, remaining protective layer 40, and thickened metal layer 50 of the SiC device, the thickness D1 of metal layer 20 ranges: and forming a thickness D4 of the thickened metal layer 50 to be greater than the sum of the thicknesses D1 and D3 while forming a numerical range of the thickness D4 to be greater than or equal to 50nm and less than or equal to 600 nm: in the range of greater than 50nm and less than or equal to 6000 nm. Further, considering the risk of deformation and the influence of deformation, the total deformation amount P is set correspondingly, and the total deformation amount P can be used to adjust the relationship between the metal layer 20, the residual protection layer 40 and the thickened metal layer 50, and make the relationship between the metal layer 20, the residual protection layer 40 and the thickened metal layer 50 satisfy:
P1=λ1（E1×D1)/(E×D4)+λ2（E2×D3)/(E×D4)
P2=λ3（E1×D1)/(E2×D3)
P=P1+P2，1.0≤P≤8.0；
Wherein P is the total deformation, P1 is the first deformation, and P2 is the second deformation;
wherein E1 is the linear expansion coefficient of the metal layer, λ1 is a first deformation adjustment coefficient, and is related to the linear expansion coefficients of the metal layer and the thickened metal layer; e2 is the linear expansion rate of the residual protective layer, λ2 is a second deformation adjustment coefficient, and is related to the linear expansion rates of the residual protective layer and the thickened metal layer; e is the linear expansion rate of the thickened metal layer, and lambda 3 is the third deformation adjustment coefficient, and is related to the linear expansion rates of the metal layer and the residual protection layer.
In some embodiments, the second deformation amount P2 is smaller than the first deformation amount P1, and the first deformation amount P1 is larger, and accordingly, the total deformation amount P may be set equal to P1. Of course, the actual deformation amounts of P1 and P2 may be compared and analyzed, and other methods may be used to calculate, for example, the total deformation ratio Q, for example, q= (p1+p2)/(P1-P2), and 1.0< q.ltoreq.5.0. Meanwhile, it should be noted that the λ1, λ2, and λ3 may be theoretical calculation analysis parameters or empirical parameters, for example, the value range of λ1 is 0.3 to 3.0, the value range of λ2 is 0.3 to 3.0, and the value range of λ3 is 0.1 to 5.0, which may be reasonably set according to practical situations, and the application is not limited thereto.
In other embodiments, the foregoing calculation method may be appropriately adjusted in consideration of the fact that the subsequent SiC device will typically be subjected to the processing such as cutting by a cutter wheel or laser grooving, cutting, etc., where E1 is the bending strength of the metal layer 20, and λ1 is the first deformation adjustment coefficient, which is related to the bending strength of the metal layer 20 and the thickened metal layer 50; e2 is the bending strength of the residual protective layer 40, λ2 is a second deformation adjustment coefficient, and is related to the bending strength of the residual protective layer 40 and the thickened metal layer 50, E is the bending strength of the thickened metal layer 50, λ3 is a third deformation adjustment coefficient, and is related to the bending strength of the metal layer 20 and the residual protective layer 40, and the corresponding total deformation amount P may be 1.0.ltoreq.P.ltoreq.8.0.
In some embodiments, the total deformation P may be 1.0, 2.0, 3.0, 4.0, 5.0, 6.0, 6.5, 7.0, 7.5, 8.0, and the total deformation ratio Q may be 1.0, 2.0, 3.0, 4.0, 5.0, preferably 1.0+.p+.5.0, or may be a range between two values, and the skilled person may set the magnitude or range of P, Q according to the actual situation, which is not set by the present application.
In the application, when the SiC wafer is heated and cooled, and the cutter wheel is cut or grooved and cut by laser, the total deformation P is set, so that the relative deformation among the metal layer 20, the residual protection layer 40 and the thickened metal layer 50 can be adjusted, the risk of deformation or deformation of the whole of the metal layer, the residual protection layer and the thickened metal layer of the SiC device can be reduced or reduced, and the heat conduction, the electromagnetic shielding and the whole mechanical strength of the SiC device are ensured.
Meanwhile, the protective layer is arranged outside the metal layer, so that the metal layer can be protected from other subsequent process in the subsequent process, the protective layer can be etched away by wet etching or dry etching even if the protective layer is oxidized, the oxidized part of the protective layer is high in controllability and good in stability, the contact effect of the finished ohmic contact and the adhesion effect of the subsequent thickened metal layer cannot be influenced by the removing process, the risk of deformation or the deformation amount of deformation of the metal layer, the residual protective layer and the thickened metal layer of the SiC device are reduced or reduced, the heat conduction, the electromagnetic shielding and the overall mechanical strength of the SiC device are ensured, and the damage to the electrical performance of the SiC device is reduced.
The technical features of the above embodiments may be arbitrarily combined, and for brevity, all of the possible combinations of the technical features of the above embodiments are not described, however, as long as there is no contradiction between the combinations of the technical features, they should be considered as the scope of the description of the present specification;
it will be appreciated by those of skill in the art that the various operations, methods, steps, means, or arrangements of steps that have been discussed in the present application may be alternated, altered, combined, or deleted; further, other steps, measures, schemes in various operations, methods, flows that have been discussed in this application can also be alternated, altered, rearranged, split, combined, or deleted; further, steps, measures, schemes in the prior art with various operations, methods, flows disclosed in the present application may also be alternated, altered, rearranged, decomposed, combined, or deleted;
the above examples merely represent a few implementations of the disclosed embodiments, which are described in more detail and are not to be construed as limiting the scope of the disclosed embodiments; it should be noted that, for those skilled in the art, several variations and modifications can be made without departing from the concept of the embodiments of the present disclosure, which fall within the scope of the embodiments of the present disclosure; accordingly, the scope of the disclosed embodiments should be determined from the following claims.
Claims (10)
1. The method for thickening the metal after SiC ohmic contact is characterized by comprising the following steps of:
Step S100: manufacturing a metal layer on the front surface or the back surface of the SiC wafer, and forming ohmic contact after annealing;
step S200: manufacturing a protective layer on the metal layer;
Step S300: removing at least part of the protective layer to form a residual protective layer;
Step S400: manufacturing a thickened metal layer on the residual protective layer;
wherein, the thickness relation of metal layer, surplus protective layer, thickening metal layer satisfies:
P=P1+P2，1.0≤P≤8.0；
P1=λ1（E1×D1)/(E×D4)+λ2（E2×D3)/(E×D4)；
P2=λ3（E1×D1)/(E2×D3)；
Wherein P is the total deformation, P1 is the first deformation, and P2 is the second deformation;
D1 is the thickness of the metal layer, E1 is the linear expansion coefficient of the metal layer, λ1 is a first deformation adjustment coefficient, and is related to the linear expansion coefficients of the metal layer and the thickened metal layer; d3 is the thickness of the residual protective layer, E2 is the linear expansion rate of the residual protective layer, λ2 is a second deformation adjustment coefficient, and is related to the linear expansion rates of the residual protective layer and the thickened metal layer; d4 is the thickness of the thickened metal layer; e is the linear expansion rate of the thickened metal layer, and lambda 3 is the third deformation adjustment coefficient, and is related to the linear expansion rates of the metal layer and the residual protection layer.
2. The method of claim 1, wherein in step S200, the thickness of the protective layer is D2, which satisfies the following conditions: a1 is less than or equal to D2/D1 is less than or equal to A2, A1 is less than or equal to 0.25 and less than or equal to 0.4, A2 is less than or equal to 0.5 and less than or equal to 5.0, D3/D2 is less than or equal to 0 and less than or equal to A3, D1+ D3 is less than or equal to D4, A3 is less than or equal to 0.5, and A1, A2 and A3 are all set constants.
3. The method of post-SiC ohmic contact metal thickening according to claim 2, wherein the protective layer comprises a first film layer having a thickness D21 and a second film layer having a thickness D22, the method being as follows: the sum of D21 and D22 is equal to D2, and the first film layer is connected with the metal layer and the second film layer, so that the following conditions are satisfied: d21 =d3, D22/D1 is equal to or less than A4,0.1 is equal to or less than A4 is equal to or less than 0.8, and A4 is a set constant.
4. The method of post-SiC ohmic contact metal thickening of claim 1, wherein the metal layer thickness D1 has a value ranging from: and the numerical range of the thickness D2 of the protective layer is that: 10nm or more and 2000nm or less; the numerical range of the thickness D3 of the residual protective layer is as follows: more than 0 and less than or equal to 1000nm; the numerical range of the thickness D4 of the thickened metal layer is as follows: more than 50nm and less than or equal to 6000nm.
5. The method according to claim 4, wherein in the step S100, a layer of Ni alloy is deposited on the back or front of the SiC wafer, and annealing is performed to form a Ni alloy layer with a thickness of D1, and the Ni alloy layer with a thickness of D1 is used as a metal layer to complete the ohmic contact fabrication of SiC.
6. The method of post-SiC ohmic contact metal thickening according to claim 5, wherein in said step S100, the deposition temperature T1 is 25-400 degrees, and the annealing time S1 is: 5min-15min, the deposition mode is as follows: evaporating or sputtering.
7. The method of claim 6, wherein in step S200, the protective layer with thickness D2 is deposited on the metal layer at a temperature T2 of 25-400 degrees by: evaporating or sputtering.
8. The method of claim 7, wherein in step S200, the protective layer is a metal protective film, and the metal comprises Al, ti, tiAl alloy.
9. The method of claim 8, wherein in step S300, the remaining protective layer is formed to a thickness D3 by wet etching away or dry etching away at least a portion of the protective layer.
10. The method of claim 9, wherein in step S400, the thickened metal layer having a thickness D4 is deposited on the remaining protective layer at a temperature T3 of 25-400 degrees by: evaporating, sputtering and electroplating.
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| JP2002016013A (en) * | 2000-06-27 | 2002-01-18 | Nissan Motor Co Ltd | Method of manufacturing silicon carbide semiconductor device |
| CN104037075A (en) * | 2014-06-12 | 2014-09-10 | 中国电子科技集团公司第五十五研究所 | Thermal-resistance-processed silicon carbide back metal thickening method |
| CN107331606A (en) * | 2017-05-09 | 2017-11-07 | 中国电子科技集团公司第五十五研究所 | The preparation method of SiC device back metal system |
| CN109087850A (en) * | 2018-06-20 | 2018-12-25 | 中国电子科技集团公司第五十五研究所 | Surface of SiC Ohmic contact optimization method |
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| JP2002016013A (en) * | 2000-06-27 | 2002-01-18 | Nissan Motor Co Ltd | Method of manufacturing silicon carbide semiconductor device |
| CN104037075A (en) * | 2014-06-12 | 2014-09-10 | 中国电子科技集团公司第五十五研究所 | Thermal-resistance-processed silicon carbide back metal thickening method |
| CN107331606A (en) * | 2017-05-09 | 2017-11-07 | 中国电子科技集团公司第五十五研究所 | The preparation method of SiC device back metal system |
| CN109087850A (en) * | 2018-06-20 | 2018-12-25 | 中国电子科技集团公司第五十五研究所 | Surface of SiC Ohmic contact optimization method |
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