Process for producing a semiconductor device having an insulating layer of silicon dioxide covered by a film of silicon oxynitride

Claim 2

A process for producing a semiconductor device having an insulating film by forming a product having an exposed film of silicon dioxide over a silicon substrate and then nitriding the product, characterised in that the insulating film is formed by converting the exposed surface of the silicon dioxide film to a silicon oxynitride by reaction of the silicon dioxide on the surface with a nitriding atmosphere containing nitrogen atoms in a plasma state at 800 to 1300°C.

Claim 3

A process according to claim 1 characterised in that the nitriding atmosphere is formed by plasma activation of an atmosphere of nitrogen gas, ammonia, nitrogen and hydrogen, nitrogen and hydrochloride or nitrogen and chlorine.

Claim 4

A process according to claim 1 characterised in that the oxynitride insulating film is formed to a thickness of 3 to 19 nm.

Claim 5

A process according to any preceding claim characterised in that the exposed film of silicon dioxide is formed to be 3 to 2000 nm thick.

Claim 6

A process according to any preceding claim characterised in that the silicon dioxide film is formed by thermal oxidation of a silicon surface layer of a silicon substrate.

Claim 7

A process according to any of claims 1 to 4 characterised in that the silicon dioxide film is made by the preliminary step of forming a silicon nitride surface film by thermal nitridation of a silicon surface layer of a silicon substrate and converting the exposed surface of the silicon nitride film to silicon dioxide by oxidation.

Claim 8

A process according to claim 6 characterised in that the silicon nitride surface film is formed by heating the silicon substrate to a temperature of 900 to 1300°C in a nitrogen containing atmosphere with an oxidant impurity in an amount of less than 100 ppm and the oxidation of the exposed surface of the silicon nitride film to silicon dioxide is effected by heating the silicon nitride in an oxidising atmosphere at a temperature of 500 to 1300°C.

Claim 9

A process of forming a semiconductor device including an insulating film by forming a silicon dioxide film on a semiconductor silicon substrate and nitriding the film characterised in that the silicon dioxide film is formed on at least a portion of the silicon substrate by thermal oxidation and the resultant silicon dioxide film is heated in a nitridating atmosphere to form silicon oxynitride.

Claim 10

A process of forming a semiconductor device including an insulating film by forming a silicon dioxide film on a semiconductor silicon substrate and nitriding the film characterised in that the silicon dioxide film is formed on at least a portion of the silicon substrate by thermal oxidation and the resultant silicon dioxide film is heated in a nitridating atmosphere to form silicon oxynitride.

Claim 11

A process according to claim 8 characterised in that the exposed film of silicon dioxide is formed to be from 3 to 2000 nm thick.

Claim 12

A process according to claim 8 or claim 9 for producing a semiconductor device including an insulating film characterised in that it comprises the further steps of providing the silicon dioxide film and the silicon oxynitride layer with a pattern of a mask for selective diffusion and diffusing impurities into the silicon substrate in such manner that the impurities do not completely diffuse into the silicon substrate below the selective diffusion mask.

Claim 13

A process according to claim 8 or claim -9 for producing a device including at least one Misfet characterised in that it comprises the additional steps of depositing a polycrystalline silicon film on the silicon oxynitride insulating film, selectively removing the polycrystalline silicon film and thereby providing the remaining polycrystalline silicon film with a pattern of a gate electrode of the at least one Misfet element, exposing a portion of the silicon oxynitride surface film and heating the substrate in an oxidation atmosphere, thereby forming a silicon dioxide film on the polycrystalline silicon film and converting substantially the silicon oxynitride to silicon dioxide and removing the exposed insulating film, thereby exposing a portion or portions of the semiconductor silicon substrate, while the silicon dioxide film on the polycrystalline silicon film is removed by an amount corresponding to the thickness of the silicon oxynitride insulating film.

Claim 14

A process according to claim 8 or claim 9 for producing a semiconductor device including at least one RAM element characterised in that it comprises the additional steps of depositing a polycrystalline film containing silicon on the silicon oxynitride insulating film, selectively removing the polycrystalline film and thereby providing the remaining polycrystalline film with an electrode pattern of a capacitor element for storing electric charges of the at least one RAM element and further thereby exposing a portion of the insulating film, heating the substrate in an oxidising atmosphere thereby forming a silicon dioxide film on the polycrystalline film having the electrode pattern of the capacitor element and forming a conductive film having a gate electrode pattern of a transistor of the at least one RAM element on both the silicon dioxide film and a portion of the exposed surface of the silicon oxynitride insulating film.

Claim 15

A process according to claim 11 characterised in that it comprises the further step of doping impurities into the separate exposed portions of the semiconductor silicon substrate thereby forming in these portions the source and drain regions of each of the at least one Misfet, each of these regions having a width in the range of 1 to 4 microns.

Claim 16

A process according to claim 12 characterised in that the silicon dioxide film which is formed on the polycrystalline film having the electrode pattern of the capacitor element has a thickness in the range 50 to 2000 nm and the insulating film has a thickness in the range 3 to 500 nm.

Claim 17

A process for producing a semiconductor device including an insulating film of silicon oxynitride characterised by forming a film consisting essentially of a silicon nitride on a silicon substrate by subjecting the substrate to direct thermal nitridation, oxydising at least a portion of the silicon nitride film and subsequently heating the silicon substrate in a nitridating atmosphere to subject at least a portion of the oxidised surface of the silicon substrate to direct nitridation.

Claim 18

A process for producing a semiconductor device including an insulating film of silicon oxynitride characterised by forming a film consisting essentially of a silicon nitride on a silicon substrate by subjecting the substrate to direct thermal nitridation, oxydising at least a portion of the silicon nitride film and subsequently heating the silicon substrate in a nitridating atmosphere to subject at least a portion of the oxidised surface of the silicon substrate to direct nitridation.

Claim 19

A process according to claim 15 characterised in that the film consisting essentially of silicon nitride is made by heating the silicon substrate to a temperature within the range of 900 to 1300°C in a nitrogen containing atmosphere with an oxidant impurity in an amount of less than 100 ppm and wherein the oxidising step comprises heating the silicon oxynitride film in an oxidising atmosphere at a temperature within the range 500 to 1300°C.

Claim 20

A semiconductor device including a silicon substrate and an insulating film characterised in that the insulating film has been formed by nitridating at least a surface portion of a silicon dioxide film.

Claim 21

A semiconductor device including a silicon substrate and an insulating film characterised in that the insulating film has been formed by nitridating at least a surface portion of a silicon dioxide film.

Claim 22

A device according to claim 17 characterised in that the insulating film has been formed by oxidising at least a portion of a silicon nitride film which has been formed by direct thermal nitridation of the silicon substrate surface, and subsequently subjecting at least a portion of the oxidised surface to the nitridation.

Claim 23

A semiconductor device according to claim 17 or claim 18 characterised in that at least an upper surface of the insulating film comprises silicon oxynitride and the nitrogen content of the oxynitride decreases gradually from the surface towards the interior of the insulating film.

Claim 25

A device according to claim 20 characterised in that the insulating film has a thickness in the range of 3 to 19 nm and the film of silicon oxynitride has a thickness in the range 2 to 10 nm.