GB1571999A - Semiconductors - Google Patents

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GB1571999A
GB1571999A GB5166876A GB5166876A GB1571999A GB 1571999 A GB1571999 A GB 1571999A GB 5166876 A GB5166876 A GB 5166876A GB 5166876 A GB5166876 A GB 5166876A GB 1571999 A GB1571999 A GB 1571999A
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surface area
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semiconductor element
polymeric material
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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
    • H01L21/18—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 elements of Group IV of the Periodic Table or AIIIBV compounds with or without impurities, e.g. doping materials
    • H01L21/30—Treatment of semiconductor bodies using processes or apparatus not provided for in groups H01L21/20 - H01L21/26
    • H01L21/302—Treatment of semiconductor bodies using processes or apparatus not provided for in groups H01L21/20 - H01L21/26 to change their surface-physical characteristics or shape, e.g. etching, polishing, cutting
    • H01L21/306—Chemical or electrical treatment, e.g. electrolytic etching
    • 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
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L23/00—Details of semiconductor or other solid state devices
    • H01L23/28—Encapsulations, e.g. encapsulating layers, coatings, e.g. for protection
    • H01L23/31—Encapsulations, e.g. encapsulating layers, coatings, e.g. for protection characterised by the arrangement or shape
    • H01L23/3157—Partial encapsulation or coating
    • H01L23/3171—Partial encapsulation or coating the coating being directly applied to the semiconductor body, e.g. passivation layer
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L2924/00—Indexing scheme for arrangements or methods for connecting or disconnecting semiconductor or solid-state bodies as covered by H01L24/00
    • H01L2924/0001—Technical content checked by a classifier
    • H01L2924/0002—Not covered by any one of groups H01L24/00, H01L24/00 and H01L2224/00
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L2924/00—Indexing scheme for arrangements or methods for connecting or disconnecting semiconductor or solid-state bodies as covered by H01L24/00
    • H01L2924/10—Details of semiconductor or other solid state devices to be connected
    • H01L2924/11—Device type
    • H01L2924/12—Passive devices, e.g. 2 terminal devices
    • H01L2924/1204—Optical Diode
    • H01L2924/12044—OLED

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  • Engineering & Computer Science (AREA)
  • Physics & Mathematics (AREA)
  • Condensed Matter Physics & Semiconductors (AREA)
  • General Physics & Mathematics (AREA)
  • Computer Hardware Design (AREA)
  • Microelectronics & Electronic Packaging (AREA)
  • Power Engineering (AREA)
  • Manufacturing & Machinery (AREA)
  • Macromolecular Compounds Obtained By Forming Nitrogen-Containing Linkages In General (AREA)
  • Formation Of Insulating Films (AREA)
  • Structures Or Materials For Encapsulating Or Coating Semiconductor Devices Or Solid State Devices (AREA)

Description

(54) IMPROVEMENTS IN SEMICONDUCTORS (71) We, GENERAL ELECTRIC COMPANY, a corporation organized and existing under the laws of the State of New York, United States of America, of I River Road, Schenectady 12305, State of New York, United States of America, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particu!arly described in and by the following statement:- This invention relates to a method for controlling the surface states of semiconductor elements.
The passivation and protection of P-N junctions exposed at surfaces of semiconductor elements is of a continuing interest to industry. This is of particular interest in high voltage power semiconductor devices such, for example, as thyristors and diodes. In such devices control of the surface field and surface charge of the semiconductor element is extremely important since this usually determines the breakdown voltage of the device. This is due to the fact that such high voltage devices tend to be surface limited. That is to say, surface breakdown occurs before breakdown in the bulk or surface leakage becomes large enough to limit the utility of the device.
To avoid such limitations as described heretofore, it is customary to adjust the surface field in a favorable way, if possible, and/or reduce the electric field at the surface by selective contouring of the surfaces of the element. An example of the former method is the use of a proprietary glass material to passivate lightly doped N-type silicon in power devices. The large negative charge in the proprietary glass tends to deplete the surface of the element of majority carriers. This method of passivation extends the depletion layer near the surface lowers the electric field at the surface, and tends to suppress surface breakdown.
The larger depletion layer volume near the surface consequently provides more generation-recombination centers to increase surface leakage which is undesirable.
Because of the presence of the large negatiye charge therein, the proprietary glass is not considered useful in lightly doped P-type silicon. Consequently, this approach to charge control for semiconductor elements employed in high voltage thyristors is not useful at all. In the case of high voltage thyristors, P-N junctions are formed between lightly doped N and P-type conductivity silicon. A high surface field condition which would tend to favor one side of the P-N junction could facilitate breakdown on the other side thereof. In this type of device, minimizing surface field is the best procedure.
The present invention provides a method for treating a selected surface area of a semiconductor element which method comprises: (a) applying a layer of a suitable polyimide-silicone copolymer material which is a variable permeability membrane material on a selected surface area of a semiconductor element; (b) curing the polymeric material in situ to form a film of material on the selected surface area which is substantially non-permeable to the operating ambient of the element at a first range of temperatures; (c) heating at least the film of polymeric material to a second, and an elevated, temperature range of 450"C + 25" to cause the polymeric material to become permeable to selected gases; (d) causing at least one of the selected gases to pass through the film of polymeric material to reach and/or react at the selected surface area of the semiconductor element; (e) adjusting the surface states at or near the selected surface area of the element by employing at least one of the selected gases; (f) removing at least some of the products of the adjusting process step and excess amounts of the at least one selected gas from the selected surface area through the film of polymeric material, and (g) re-establishing the substantially nonpermeable characteristic of the film of polymeric material.
The selected gases may be wet nitrogen, oxygen or hydrogen.
To re-establish the substantially non-permeable characteristic of the film of polymeric material the element and film is preferably cooled to a lower temperature range. Preferably, the polyimide-silicone material is one selected from the group of materials consisting of a reaction product of a silicon-free organic diamine, an organic tetracarboxylic acid dianhydride and a polysiloxane and having the recurring structural units of the formula:
with from 5 to 50 mol percent intercondensed structural units of the formula:
wherein R is a divalent hydrocarbon radical, R' is a monovalent hydrocarbon radical, R" is a tetravalent organic radical, Q is a divalent silicon-free organic radical which is the residue of an organic diamine, x is an integer having a value greater than zero, and m and n are integers greater than one and may be equal to each other.
A preferred material is the reaction product of methylene dianiline, benzophenone tetracarboxylic acid and bis(y-aminopropyl)tetramethyldisiloxane.
Excellent results are obtained when the molar ratio of methylene dianiline to bis(yaminopropyl)tetramethyldisiloxane lies in the range from 95:5 to 50:50 and preferably in the range from 75:25 to 65:35. A suitable ratio is 70:30.
The present invention will be further described by way of Example only with reference to the accompanying drawings in which: FIGURES 1 and 2 are each a side elevation view, partly in cross-section, of a semiconductor element made in accordance with the teachings of this invention.
With reference to FIGURE 1, there is shown a semiconductor element 10 comprised of a body 12 of semiconductor material. The body 12 is prepared by suitable means, such, for example, as by polishing and lapping to parallelism two opposed surfaces 14 and 16. The body 12 has two or more regions of opposite type conductivity and a P-N junction formed by the abutting surfaces of each pair of regions of opposite type conductivity. The end portion of at least one P-N junction is exposed in a surface of the body 12. The body 12 comprises a suitable semiconductor material such, for example, as silicon, silicon carbide, germanium, compounds of Group II and Group VI elements, and compounds of Group III and Group V elements.
In order to more fully describe the invention and for no other purpose, the body 12 will be described as being comprised of silicon semiconductor having five regions of conductivity and four P-N junctions. Such a configured element 10 may function as a thyristor. Therefore, the body 12 has regions 18 and 20 of P-type conductivity, a region 19 of P-type conductivity and regions 22, 24 and 26 of N-type conductivity. P-N junctions 28, 30, 32 and 34 are formed by the abutting surfaces of the respective pairs of regions 18 and 22, 22 and 20, 20 and 24, and 20 and 26 of opposite type conductivity.
One means of aiding in the control of surface field on such a controlled rectifier is to contour the side surface 36 after affixing the partially processed body 12 to a large area contact, or support electrode, 38 by a layer 40 of a suitable ohmic electrical solder. Electrical contacts 42 and 44 are affixed to the respective regions 24 and 26. As illustrated, the contouring of the surface 36 results in the well known "double bevel" surface.
Referring now to FIGURE 2, there is shown a semiconductor element 50 embodying a double positive bevel configuration for controlling surface field. All items denoted by the same reference numbers as those in element 10 of FIGURE 1 are the same, and function in the same manner, as the corresponding item in element 10. The element 50 functions as a thyristor for the configuration illustrated.
Regardless of the method employed to control the surface field, selected end portions of at least some of the P-N junctions are exposed at surface areas of the body 12. It is necessary therefore to apply a suitable material to protect the exposed end portions of the P-N junctions.
A layer 46 of a protective coating material is disposed on at least the surface 36 and the exposed end portion of at least the P-N junctions 28 and 30. It is desirable that the material of the layer 46 adhere to the surface 36 as well as to the material of the layer 44 and the contact, or support electrode 38. The material of the layer 46 must act as a variable permeability material so as to be capable of withstanding an elevated temperature for extended periods of time necessary to treat selected surface areas of the element 10 with a particular gas. Additionally, the material of the layer must be permeable at the elevated temperature of gas treatment, that is, it must act as a membrane and permit the passage of selected gases through the layer 46 to the surfaces of the element 10 and to pass through the layer 46 from the surface. Additionally, the material of the layer 46 must be sufficiently porous at the elevated temperature to permit other gaseous products to pass through the layer 46 to the ambient. Upon cooling to room temperature, the material of the layer 46 must be substantially impermeable to the ambient thereby forming a substantially hermetic seal for the coated surface upon which it is disposed. That is to say, the operating ambient will have no deleterious effect on the surface charge of the coated surface.
A protective coating material of polyimide-silicone copolymer has been found to be such a desirable material when disposed on at least the surface 36 and the exposed end portion of at least the P-N junctions 28 and 30.
The protective coating material may be disposed on the surface 36 as a precursor polymer dissolved in a suitable solvent. Upon heating, or by evaporation at room temperature, the protective coating material of the layer 46 is polymerized in situ on the surfaces 36 and the end portion of at least one P-N junction.
Preferably, the material of the layer 46 is applied to the preselected surface area of the surface 36 of the body 12 as a solution of a polymeric intermediate. Application of the material to at least the surface 36 of the body 12 is by such suitable means as, for example, spraying, spinning and brushing. The body 12 with the applied protective coating material is then heated to convert the resinous soluble polymer intermediate to a cured, solid, and selectively insoluble material.
The protective coating material of the layer 46 is preferably one which when cured exhibits a good adhesion property relative to the surface 36. Additionally, the material should exhibit good abrasion resistance and resistance to the chemical reagents utilized in finishing the fabrication of the element 10. Further, the material should exhibit good heat resistance properties as it will be subjected to elevated temperatures to adjust and to control the surface states and charge of the element 10. Further, the material of the layer 46 should preferably have the inherent property of exhibiting no outgassing during the heat treatment process.
A suitable material for comprising the layer 46 and meeting the aforesaid requirements is the reaction product of a silicon-free organic diamine, an organic tetracarboxylic acid dianhydride and a polysiloxane diamine, which is a polymer precursor soluble in a suitable organic solvent. On curing, it yields a copolymer having recurring structural units of the formula:
with from 5 to 50 mol percent intercondensed structural units of the formula:
wherein R is a divalent hydrocarbon radical, R' is a monovalent hydrocarbon radical, R" is a tetravalent organic radical, Q is a divalent silicon-free organic radical which is the residue of an organic diamine, x is an integer having a value of 1 to 1,000 or more, m and n are the same or different integers greater than 1, and preferably from 10 to 10,000 or more.
The above-mentioned block copolymers can be prepared by effecting reaction, in the proper molar proportions, of a mixture of ingredients comprising a diaminosiloxane of the general formula:
a silicon-free diamino compound of the formula: IV. NH2-Q-NH2 and a tetracarboyxlic acid dianhydride having the formula:
wherein R, R', R", Q and x have the meanings given above.
It will be recognized that the ultimate polyimide siloxape composition used in the practice of this invention will consist essentially of the imido structure found in Formulas I and II. However, the actual precursor materials resulting from the reaction of the diaminosiloxane, the silicon-free organic diamine and the tetracarboxylic acid dianhydride will initially be in the form of a polyamic acid structure composed of structural units of the formulas:
where R, R', R", Q, x, m and n have the meanings given above.
The diamino siloxanes of Formula III which may be used in the practice of the present invention include compounds having the following formulas:
The diamines of Formula IV above are described in the prior art and are to a large extent commercially available materials. Typical of such diamines from which the prepolymer may be prepared are the following: m-phenylenediamine; p-phenylenediamine; 4,4'-diaminodiphenylpropane; 4,4'-diaminodiphenylmethane; benzidine; 4,4'-diaminodiphenyl sulfide; 4,4'-diaminodiphenyl sulfone; 4,4'-diaminodiphenyl ether; 1 ,5-diaminophthalene; 3,3'-dimethylbenzidine; 3,3'-dimethoxybenzidine; 2,4-bis( -amino-t-butyl)toluene; bis(p-,B-amino-t-butylphenyl)ether; bis(p-,B-methyl-o-aminopentyl)benzene; 1 ,3-diamino-4-isopropylbenzene; 1 ,2-bis(3-aminopropoxy)ethane; m-xylylenediamine; p-xylylenediamine; bis(4-aminocyclohexyl)methane; decamethylenediamine; 3-methylheptamethylenediamine; 4,4-dimethylheptamethylenediamine; 2,11-dodecanediamine; 2,2-dimethylpropylenediamine; octamethylenediamine; 3-methoxyhexamethylenediamine; 2,5-dimethylhexamethylenediamine; 2,5-dimethylheptamethylenediamine; 3-methylheptamethylenediamine; 5-methylnonamethylenediamine; 1 ,4-cyclohexanediamine; I,12-octadecanediamine bis(3-aminopropyl)sulfide; N-methyl-bis(3-aminopropyl)amine; hexamethylenediamine; methylene dianiline; heptamethylenediamine; nopamethylenediamine; and mixtures thereof. It should be noted that these diamines are given merely for the purpose of illustration and are not considered to be all inclusive. Other diamines not mentioned will readily be apparent to those skilled in the art.
The tetracarboxylic acid dianhydrides of Formula V may further be defined in that the R" is a tetravalent radical, e.g. a radical derived from or containing an aromatic group containing at least 6 carbon atoms characterized by benzenoid unsaturation, wherein each of the 4 carbonyl groups of the dianhydride are attached to a separate carbon atom in the tetravalent radical, the carbonyl groups being in pairs in which the groups in each pair are attached to adjacent carbon atoms of the R radical or to carbon atoms in the R radical at most one carbon atoms removed, to provide a 5-membered or 6-membered ring as follows:
Illustrations of dianhydrides suitable for use in the present invention (with their reference designation in parenthesis) include: pyromellitic dianhydride (PMDA); 2,3,6,7-napthalene tetracarboxylic dianhydride; 3,3',4,4'-diphenyl tetracarboxylic dianhydride; 1,2,5,6-napthalene tetracarboxylic dianhydride; 2,2',3,3'-diphenl tetracarboxylic dianhydride; 2,2-bis(3,4-dicarboxyphenyl)propanedianhydride; bis(3,4-dicarboxyphenyl)sulfone dianhydride; 2,2-bis[4-3,4-dicarboxyphenoxy)phenyl] propane dianhydride (BPA dianhydride); 2,2-bis[4-(2,3-dicarboxyphenoxy)phenyl]propane dianhydride; benzophenone tetracarboxylic acid dianhydride (BPDA); perylene-l,2,~7.8-tetracarboxylic acid dianhydride; bis(3,4-dicarboxyphenyl)ether dianhydride, and bis(3,4-dicarboxyphenyl)methane dianhydride; and aliphatic anhydrides such as cyclopentane tetracarboxylic dianhydride, cyclohexane tetracarboxylic dianhydride, butane tetracarboxylic dianhydride, etc.
The incorporation of other anhydrides, such as trimellitic anhydride, to make amide-imide-siloxane polymers is not precluded.
Application of the block copolymers or blends of polymers in a suitable solvent (including, for example, N-methylpyrrolidone, N,N-dimethylacetamine, N,N-dimethylformamide, etc.) alone or combined with non-solvents, to the substrate material may be by conventional means such as dipping, spraying, painting, spinning, etc. The block copolymers or blends of polymers may be dried in an initial heating step at temperatures of about 75 to 1500C for a sufficient time frequently under vacuum to remove the solvent. The polyamic acid is then converted to the corresponding polyimide-siloxane by heating at temperatures of about 1500C-3000C for a sufficient time to effect the desired conversion to the polyimide structure and final cure.
A suitable material is prepared as a solution of a polymer precursor in the form of a polyamic acid dissolved in N-methyl-2-pyrrolidone containing 25% solids by weight. This solution is disposed on the surface of the body in which end portions of P-N junctions are disposed by any suitable means such for example as by painting or spinning.
A particular polymer precursor solution is formed by reacting benzophenone tetracarboxylic acid dianhydride with methylene dianiline and bis(y-aminopropyl)tetramethyldisiloxane, the latter two diamine materials being present in the molar ratio of 70:30. The reaction is carried out at a temperature of less than 50"C and using suitably purified and dried materials to favor a large molecular weight polymer.
A preferred curing cycle for materials of the above general formula is as follows: (a) from 15 to 30 minutes at from 1350C to 1500C in dry N2.
(b) from 15 to 60 minutes at about 185"C + 10 C in dry N2.
(c) from 1 to 3 hours at about 225"C in vacuum.
Alternately, it has been found that one may be able to cure the coating material in other atmospheres such, for example, as air for ease of commercial application of this invention.
Sufficient material is applied to the surface 36 to provide a layer 46 the thickness of which is from 1 micron to 100 microns. The minimum thickness is determined by the requirement that the cured material not break down electrically at the maximum electric field present under forward or reverse blocking conditions.
The coated element 10 is then exposed to a wet reducing or an inert ambient to reduce surface state densities on surface areas of the processed body 12. The coated element 10 is heated to a temperature of approximately 450"C + 25"C for about 30 minutes in ambient such, for example, as nitrogen, oxygen, argon, methane, hydrogen. The ambient may or may not contain water vapor. Preferably, nitrogen containing from about 1 to 3 percent water vapor by volume is employed for adjusting the member of active surface states.
It has been discovered that the material of the layer 46 forms substantially a hermetic seal for the element 10 in the operating ambient therefor. However, when heated to the elevated temperature of about 450"C it has been found that the material now is permeable to the gases employed for adjusting surface state densities on selected surface areas of the element 10. The gas of the ambient, including water vapor when required, is able to freely move from the outside ambient through the material of the layer 46 to the surface of the body 12. After acting on the surface of the body 12, reaction products of the gas and the materials presented at the surface of the body 12 are able to travel from the surface, through the cured polyimide-silicone polymer to the surrounding ambient. Some of the products escaping from the surface under treatment are those products produced during previous processing of the body 12. The material of the layer 46 tends to act as a variable permeability membrane with permeability controlled by temperature.
Upon completion of the heat treatment, the coated element is cooled to room temperature. The material of the layer 46 assumes its original cured condition of forming a substantially hermetic seal of the surface to which it is applied. The material is no longer permeable and the surface charge states are preserved.
It is believed that this treatment is effective because the surface charge present on the element 10 has a large fraction which is probably present as interface states.
A proportionally smaller fraction of the surface states is a fixed charge. Therefore, the material of the layer 46 forms an excellent passivation coating for semiconductor elements as well as an excellent means for controlling the surface states thereof. The material and process is particularly suitable for high power semiconductor devices with high voltage -- low reverse leakage requirements.
Additionally, the material and work process is also suitable for transistor and integrated circuit manufacturing operations.
WHAT WE CLAIM IS: 1. A method for treating a selected surface area of a semiconductor element which method comprises: (a) applying a layer of a suitable polyimide-silicone copolymer material which is a variable permeability membrane material on a selected surface area of a semiconductor element; (b) curing the polymeric material in situ to form a film of material on the selected surface area which is substantially non-permeable to the operating ambient of the element at a first range of temperatures; (c) heating at least the film of polymeric material to a second, and an elevated, temperature range of 450"C + 25"C to cause the polymeric material to become permeable to selected gases; (d) causing at least one of the selected gases to pass through the film of polymeric material to reach and/or react at the selected surface area of the semiconductor element; (e) adjusting the surface states at or near the selected surface area of the element by employing at least one of the selected gases; (f) removing at least some of the products of the adjusting process step and excess amounts of the at least one selected gas from the selected surface area through the film of polymeric material, and (g) re-establishing the substantially nonpermeable characteristic of the film of polymeric material.
2. A method as claimed in claim 1 wherein the semiconductor element comprises a body of silicon semiconductor material.
3. A method as claimed in claim 1 wherein the polymeric material is derived from benzophenone tetracarboxylic acid dianhydride reacted with methylene dianiline and bis (y-aminopropyl) tetramethyldisiloxane.
4. A method as claimed in claim 3 wherein the molar ratio of methylene dianiline to bis (y-aminopropyl) tetramethyldisiloxane is from 95:5 to 50:50.
5. A method as claimed in claim 4 wherein the molar ratio is from 75:25 to 65:35.
6. A method as claimed in claim 4 wherein the molar ratio is about 70:30.
7. A method as claimed in any one of the preceding claims wherein the at least one selected gas is wet nitrogen, oxygen or hydrogen.
8. A method as claimed in any one of the preceding claims wherein the at least one selected gas contains from 1 to 3 percent by volume water vapor.
9. A method as claimed in any one of the preceding claims wherein adjusting of the surface states on the selected surface area is practiced for about 30 minutes.
10. A method as claimed in claim 1 wherein the polymeric variable permeability membrane material is a reaction product of a silicon-free organic diamine, an organic tetracarboxylic acid dianhydride and a polysiloxane and having the recurring structural units of the formula:
**WARNING** end of DESC field may overlap start of CLMS **.

Claims (15)

**WARNING** start of CLMS field may overlap end of DESC **. ambient through the material of the layer 46 to the surface of the body 12. After acting on the surface of the body 12, reaction products of the gas and the materials presented at the surface of the body 12 are able to travel from the surface, through the cured polyimide-silicone polymer to the surrounding ambient. Some of the products escaping from the surface under treatment are those products produced during previous processing of the body 12. The material of the layer 46 tends to act as a variable permeability membrane with permeability controlled by temperature. Upon completion of the heat treatment, the coated element is cooled to room temperature. The material of the layer 46 assumes its original cured condition of forming a substantially hermetic seal of the surface to which it is applied. The material is no longer permeable and the surface charge states are preserved. It is believed that this treatment is effective because the surface charge present on the element 10 has a large fraction which is probably present as interface states. A proportionally smaller fraction of the surface states is a fixed charge. Therefore, the material of the layer 46 forms an excellent passivation coating for semiconductor elements as well as an excellent means for controlling the surface states thereof. The material and process is particularly suitable for high power semiconductor devices with high voltage -- low reverse leakage requirements. Additionally, the material and work process is also suitable for transistor and integrated circuit manufacturing operations. WHAT WE CLAIM IS:
1. A method for treating a selected surface area of a semiconductor element which method comprises: (a) applying a layer of a suitable polyimide-silicone copolymer material which is a variable permeability membrane material on a selected surface area of a semiconductor element; (b) curing the polymeric material in situ to form a film of material on the selected surface area which is substantially non-permeable to the operating ambient of the element at a first range of temperatures; (c) heating at least the film of polymeric material to a second, and an elevated, temperature range of 450"C + 25"C to cause the polymeric material to become permeable to selected gases; (d) causing at least one of the selected gases to pass through the film of polymeric material to reach and/or react at the selected surface area of the semiconductor element; (e) adjusting the surface states at or near the selected surface area of the element by employing at least one of the selected gases; (f) removing at least some of the products of the adjusting process step and excess amounts of the at least one selected gas from the selected surface area through the film of polymeric material, and (g) re-establishing the substantially nonpermeable characteristic of the film of polymeric material.
2. A method as claimed in claim 1 wherein the semiconductor element comprises a body of silicon semiconductor material.
3. A method as claimed in claim 1 wherein the polymeric material is derived from benzophenone tetracarboxylic acid dianhydride reacted with methylene dianiline and bis (y-aminopropyl) tetramethyldisiloxane.
4. A method as claimed in claim 3 wherein the molar ratio of methylene dianiline to bis (y-aminopropyl) tetramethyldisiloxane is from 95:5 to 50:50.
5. A method as claimed in claim 4 wherein the molar ratio is from 75:25 to 65:35.
6. A method as claimed in claim 4 wherein the molar ratio is about 70:30.
7. A method as claimed in any one of the preceding claims wherein the at least one selected gas is wet nitrogen, oxygen or hydrogen.
8. A method as claimed in any one of the preceding claims wherein the at least one selected gas contains from 1 to 3 percent by volume water vapor.
9. A method as claimed in any one of the preceding claims wherein adjusting of the surface states on the selected surface area is practiced for about 30 minutes.
10. A method as claimed in claim 1 wherein the polymeric variable permeability membrane material is a reaction product of a silicon-free organic diamine, an organic tetracarboxylic acid dianhydride and a polysiloxane and having the recurring structural units of the formula:
with from 5 to 50 mol percent intercondensed structural units of the formula:
wherein R is a divalent hydrocarbon radical, R' is a monovalent hydrocarbon radical, R" is a tetravalent organic radical, Q is a divalent silicon-free organic radical which is the residue of an organic diamine, x is an integer having a value of 1 to 1000 or more, m and n are same or different integers greater than 1.
11. A method as claimed in claim 10 wherein the silicon-free-organic diamine is methylene dianiline; the organic dianhydride is benzophenone tetracarboxylic acid, and the polysiloxane is bis (y-amino propyl) tetramethyldisiloxane.
12. A method as claimed in claim 11 wherein the molar ratio of methylene dianiline to bis (y-aminopropyl)- tetramethyldisiloxane is 70:30.
13. A method for treating a selected surface area of a semiconductor element as claimed in claim 1 substantially as hereinbefore described.
14. A method for treating a selected surface area of a semiconductor element as claimed in claim 1 substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.
15. A semiconductor element when treated by a method as claimed in any one of the preceding claims.
GB5166876A 1975-12-11 1976-12-10 Semiconductors Expired GB1571999A (en)

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GB2558147B (en) * 2015-11-05 2020-11-11 Abb Schweiz Ag Power semiconductor device and method for producing a power semiconductor device

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SE418433B (en) * 1975-12-11 1981-05-25 Gen Electric SEMICONDUCTOR ELEMENT WITH A LAYER OF A POLYMERIC SILOXAN-CONTAINING MEMBRANE MEMBRANE MATERIAL WITH VARIABLE PERMEABILITY APPLIED ON SELECTED SURFACE OF THE ELEMENT
GB1585477A (en) * 1976-01-26 1981-03-04 Gen Electric Semiconductors
CH661933A5 (en) * 1978-09-18 1987-08-31 Gen Electric Process for the preparation of a coating composition for the surface of a semiconductor component, this composition, and the use thereof for preventing surface breakdown
CH661932A5 (en) * 1978-09-18 1987-08-31 Gen Electric Process for the preparation of a coating composition for semiconductor components, this composition, and the use thereof
JPH0395021U (en) * 1990-01-16 1991-09-27
DE19500235A1 (en) * 1995-01-05 1996-07-11 Roth Technik Gmbh Cover layer for electrical conductors or semiconductors

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DE1464602B2 (en) * 1962-11-30 1970-11-26 Fuji Denki Seizo K.K., Tokio Process for the surface treatment of semiconductor devices
US3615913A (en) * 1968-11-08 1971-10-26 Westinghouse Electric Corp Polyimide and polyamide-polyimide as a semiconductor surface passivator and protectant coating
US3553282A (en) * 1969-09-08 1971-01-05 Gen Electric Siloxane containing polyamide acid blends
US3598784A (en) * 1970-03-11 1971-08-10 Gen Electric Polysiloxane amides
US3740305A (en) * 1971-10-01 1973-06-19 Gen Electric Composite materials bonded with siloxane containing polyimides
JPS5421073B2 (en) * 1974-04-15 1979-07-27

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB2558147B (en) * 2015-11-05 2020-11-11 Abb Schweiz Ag Power semiconductor device and method for producing a power semiconductor device

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DE2655803C2 (en) 1986-04-17
JPS5272578A (en) 1977-06-17
FR2335042B1 (en) 1982-10-29
SE418432B (en) 1981-05-25
DE2655803A1 (en) 1977-06-16
FR2335042A1 (en) 1977-07-08
SE7613875L (en) 1977-06-12
JPS597213B2 (en) 1984-02-17

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