JP2021019004A - Manufacturing method of semiconductor device - Google Patents

Abstract

To provide a manufacturing method of a semiconductor device, capable of forming an ion implantation mask without receiving damages or the like on a front surface of a semiconductor substrate.SOLUTION: A manufacturing method of a semiconductor device, includes: a step of forming a heat-resistant organic film onto a main surface 10a of a semiconductor substrate 10; a step of forming an insulation film 122 onto a heat-resistant organic film 121; a step of forming a resist pattern 30 having an open part 30a onto the insulation film 122; a step of forming an open part 122b on the insulation film 122 by removing the insulation film 122 in the open part 30a of the resist pattern 30; a step of forming an ion implantation mask 121M formed by the heat-resistant organic film 121 by removing the heat-resistant organic film 121 in the open part 122b of the insulation film 122 with an etching by using a plasma containing oxygen; and a step of heating the semiconductor substrate 10 and ion-implanting an impurity element to the semiconductor substrate 10 by using the ion implantation mask 121M.SELECTED DRAWING: Figure 12

Description

The present invention relates to a method for manufacturing a semiconductor device.

The process of manufacturing a semiconductor device includes an ion implantation step of implanting ions from the surface into a predetermined region of a semiconductor substrate such as Si or SiC. In the ion implantation step, for example, a silicon oxide film or the like is formed on the surface of the semiconductor substrate, a resist pattern is formed in the region where the mask is formed, and the silicon oxide film or the like in the region where the resist pattern is not formed is removed. An opening is formed to form an ion implantation mask. After that, ions of the impurity element are ion-implanted on the surface of the semiconductor substrate exposed at the opening using the formed ion implantation mask.

Japanese Unexamined Patent Publication No. 2008-251579 Japanese Unexamined Patent Publication No. 2012-178494

However, the ion implantation mask is formed by removing the silicon oxide film or the like in the ion-implanted region, and at this time, a part of the surface of the semiconductor substrate may be removed or damaged. .. Therefore, in the method of manufacturing a semiconductor device, there is a demand for a method capable of forming an ion implantation mask without damaging the surface of the semiconductor substrate.

According to one aspect of the present embodiment, the method for manufacturing a semiconductor device includes a step of preparing a semiconductor substrate, a step of forming a heat-resistant organic film on the main surface of the semiconductor substrate, and an insulating film on the heat-resistant organic film. It has a step of forming a resist pattern having an opening on the insulating film, and a step of removing the insulating film at the opening of the resist pattern and forming an opening in the insulating film. Further, a step of forming an ion implantation mask made of the heat-resistant organic film by removing the heat-resistant organic film at the opening of the insulating film by etching using plasma containing oxygen, and a step of heating the semiconductor substrate to perform the ion implantation mask. It has a step of ion-implanting an impurity element into a semiconductor substrate using the above.

According to the method for manufacturing a semiconductor device of the present disclosure, an ion implantation mask can be formed without being damaged on the surface of the semiconductor substrate.

FIG. 1 is a process diagram (1) of a method for manufacturing a semiconductor device. FIG. 2 is a process diagram (2) of a method for manufacturing a semiconductor device. FIG. 3 is a process diagram (3) of a method for manufacturing a semiconductor device. FIG. 4 is a process diagram (4) of a method for manufacturing a semiconductor device. FIG. 5 is a process diagram (1) of another manufacturing method of the semiconductor device. FIG. 6 is a process diagram (2) of another manufacturing method of the semiconductor device. FIG. 7 is a process diagram (3) of another manufacturing method of the semiconductor device. FIG. 8 is a process diagram (4) of another manufacturing method of the semiconductor device. FIG. 9 is a process diagram (1) of the method for manufacturing the semiconductor device of the present embodiment of the present disclosure. FIG. 10 is a process diagram (2) of the method for manufacturing the semiconductor device of the present embodiment of the present disclosure. FIG. 11 is a process diagram (3) of the method for manufacturing the semiconductor device of the present embodiment of the present disclosure. FIG. 12 is a process diagram (4) of the method for manufacturing the semiconductor device of the present embodiment of the present disclosure. FIG. 13 is a process diagram (5) of the method for manufacturing the semiconductor device of the present embodiment of the present disclosure. FIG. 14 is a process diagram (6) of the method for manufacturing the semiconductor device of the present embodiment of the present disclosure. FIG. 15 is a process diagram (7) of the method for manufacturing the semiconductor device of the present embodiment of the present disclosure. FIG. 16 is a process diagram (1) of a method for manufacturing a Schottky barrier diode according to the present embodiment of the present disclosure. FIG. 17 is a process diagram (2) of a method for manufacturing a Schottky barrier diode according to the present embodiment of the present disclosure. FIG. 18 is a process diagram (3) of a method for manufacturing a Schottky barrier diode according to the present embodiment of the present disclosure. FIG. 19 is a process diagram (4) of a method for manufacturing a Schottky barrier diode according to the present embodiment of the present disclosure.

The embodiment for carrying out will be described below.

[Explanation of Embodiments of the present disclosure]
First, embodiments of the present disclosure will be listed and described. In the following description, the same or corresponding elements are designated by the same reference numerals, and the same description is not repeated for them.

[1] The method for manufacturing a semiconductor device according to one aspect of the present disclosure includes a step of preparing a semiconductor substrate, a step of forming a heat-resistant organic film on the main surface of the semiconductor substrate, and a step of forming a heat-resistant organic film on the heat-resistant organic film. A step of forming an insulating film, a step of forming a resist pattern having an opening on the insulating film, and a step of removing the insulating film at the opening of the resist pattern to form an opening in the insulating film. A step of forming an ion injection mask made of the heat-resistant organic film by removing the heat-resistant organic film at the opening of the insulating film by etching using a plasma containing oxygen, and heating the semiconductor substrate. Then, the semiconductor substrate is provided with a step of ion-injecting an impurity element into the semiconductor substrate using the ion-injection mask.

As a result, the ion implantation mask can be formed without being damaged on the surface of the semiconductor substrate, and the yield of the semiconductor device can be improved.

[2] The heat-resistant organic film is made of polyimide.

Since polyimide has high heat resistance, it is preferable as a heat-resistant organic film in the present invention.

[3] The insulating film is a film containing silicon oxide or silicon nitride.

Silicon oxide or silicon nitride is difficult to remove by etching with plasma containing oxygen.

[4] The semiconductor substrate is a silicon carbide substrate.

The present invention is particularly useful because the silicon carbide substrate is heated when ions are implanted into the silicon carbide substrate.

[5] The insulating film is removed by dry etching.

Dry etching is suitable for forming a fine shape, and an opening having a desired shape can be formed in the insulating film.

[Details of Embodiments of the present disclosure]
Hereinafter, one embodiment of the present disclosure will be described in detail, but the present embodiment is not limited thereto.

First, a process of forming an ion implantation mask in the manufacturing process of a semiconductor device will be described.

Specifically, as shown in FIG. 1, an oxide film 20 for forming an ion implantation mask is formed on the main surface 10a of the SiC (silicon carbide) substrate 10 which is a semiconductor substrate. The oxide film 20 is a silicon oxide film, which is formed by film formation by CVD (chemical vapor deposition), and the film thickness of the oxide film 20 formed is, for example, about 2 μm.

Next, as shown in FIG. 2, a resist pattern 30 having an opening 30a is formed on the surface 20a of the oxide film 20. The resist pattern 30 is formed by applying a photoresist to the surface 20a of the oxide film 20 and performing exposure and development with an exposure apparatus. The resist pattern 30 formed has, for example, a thickness of about 2 μm and a width of the opening 30a of about 0.5 μm.

Next, as shown in FIG. 3, the oxide film 20 in the opening 30a of the resist pattern 30 is removed by dry etching such as RIE (Reactive Ion Etching) to form the opening 20b. As a result, the main surface 10a of the SiC substrate 10 is exposed. In this dry etching, since a fluorine-based gas such as CF ₄ or C ₂ F ₆ is used as the etching gas, a part of the main surface 10a of the SiC substrate 10 may be removed by overetching or damaged by plasma. is there. After that, by removing the resist pattern 30 by ashing or the like, the ion implantation mask 20M is formed by the oxide film 20 having the opening 20b.

Next, as shown in FIG. 4, the SiC substrate 10 is heated to about 400 ° C., and ion implantation of an impurity element is performed on the SiC substrate 10 using an ion implantation mask 20M to form an ion implantation region 11. ..

A semiconductor device manufactured by the above-mentioned manufacturing process is desirable because a part of the main surface 10a of the SiC substrate 10 is removed by overetching or damaged by plasma when the ion implantation mask 20M is formed. It may not be possible to obtain the characteristics of. The ion implantation mask 20M is formed of silicon oxide because it is necessary to heat the SiC substrate 10 to about 400 ° C. when ion-implanting an impurity element into the SiC substrate 10. When the ion implantation mask is formed by a photoresist, the ion implantation mask is deformed or deteriorated when heated to about 400 ° C.

Further, as a method for preventing a part of the main surface 10a of the SiC substrate 10 from being removed by overetching or being damaged by plasma, the methods shown in FIGS. 5 to 8 can be considered.

Specifically, as shown in FIG. 5, the polysilicon film 21 and the oxide film 22 are formed in this order on the main surface 10a of the SiC substrate 10. The polysilicon film 21 is formed by film formation by CVD, and the film thickness of the polysilicon film 21 formed is, for example, about 0.2 μm. The oxide film 22 is a silicon oxide film, which is formed by film formation by CVD, and the film thickness of the oxide film 20 formed is, for example, about 1.8 μm.

Next, as shown in FIG. 6, a resist pattern 30 having an opening 30a is formed on the surface 22a of the oxide film 22. The resist pattern 30 is formed by applying a photoresist to the surface 20a of the oxide film 22 and exposing and developing it with an exposure apparatus.

Next, as shown in FIG. 7, the oxide film 22 and the polysilicon film 21 in the opening 30a of the resist pattern 30 are removed by dry etching such as RIE to form the opening 22b. In order to prevent a part of the main surface 10a of the SiC substrate 10 from being removed by overetching or being damaged by plasma, a part of the polysilicon film 21 remains in the opening 30a of the resist pattern 30. Stop etching. After that, by removing the resist pattern 30 by ashing or the like, the ion implantation mask 22M is formed by the oxide film 22 and the polysilicon film 21 having the opening 22b.

Next, as shown in FIG. 8, the SiC substrate 10 is heated to about 400 ° C., and ions are implanted into the SiC substrate 10 using the ion implantation mask 22M to form the ion implantation region 12. In the ion implantation mask 22M, a part of the polysilicon film 21 remains at the bottom surface of the opening 22b, so that the ions to be implanted pass through the remaining polysilicon film 21 and are implanted into the SiC substrate 10. Therefore, it is necessary to increase the implantation energy at the time of ion implantation. Further, if the thickness of the polysilicon film 21 remaining in the opening 22b varies, the depth at which ions are injected also varies. For this reason, the characteristics of the manufactured semiconductor device vary and the yield is lowered.

Therefore, it is possible to manufacture a semiconductor device as uniform as possible, and there is a demand for a method for manufacturing a semiconductor device in which a part of the surface of the semiconductor substrate is not removed or damaged when the ion implantation mask is formed. ing.

(Manufacturing method of semiconductor device)
Next, a method of manufacturing the semiconductor device in this embodiment will be described. Ion implantation in the method for manufacturing a semiconductor device in this embodiment is performed by the following steps.

First, as shown in FIG. 9, the heat-resistant organic film 121 and the insulating film 122 are formed in this order on the main surface 10a of the SiC substrate 10. The heat-resistant organic film 121 is polyimide and is formed on the main surface 10a of the SiC substrate 10 by spin coating. The film thickness of the heat-resistant organic film 121 formed is, for example, about 2 μm. The insulating film 122 is made of silicon oxide, silicon nitride, or the like. In the present embodiment, the insulating film 122 is SOG (spin on glass) and is formed by spin coating on the heat-resistant organic film 121. The film thickness of the insulating film 122 to be formed is, for example, about 0.2 μm.

Next, as shown in FIG. 10, a resist pattern 30 having an opening 30a is formed on the surface 122a of the insulating film 122. The resist pattern 30 is formed by applying a photoresist to the surface 122a of the insulating film 122 and exposing and developing it with an exposure apparatus.

Next, as shown in FIG. 11, the insulating film 122 in the opening 30a of the resist pattern 30 is removed by dry etching such as RIE until the surface 121a of the heat-resistant organic film 121 is exposed to form the opening 122b. .. In this dry etching, a fluorine-based gas such as CF ₄ or C ₂ F ₆ is used as the etching gas.

Next, as shown in FIG. 12, plasma is generated using oxygen gas as the etching gas, and the heat-resistant organic film 121 in the opening 122b of the insulating film 122 is removed by RIE to form the opening 121b. , The main surface 10a of the SiC substrate 10 is exposed. At this time, the resist pattern 30 on the insulating film 122 is also removed at the same time. In RIE using oxygen plasma, the heat-resistant organic film 121 is etched, but the SiC substrate 10 is hardly etched, so that a part of the main surface 10a of the SiC substrate 10 is removed by overetching or is damaged by plasma. There is no such thing.

Next, as shown in FIG. 13, the insulating film 122 is removed by wet etching with hydrofluoric acid. As a result, the ion implantation mask 121M is formed by the heat-resistant organic film 121 having the opening 121b.

Next, as shown in FIG. 14, the SiC substrate 10 is heated to about 400 ° C., and an ion implantation region 111 is formed by ion-implanting an impurity element into the SiC substrate 10 using an ion implantation mask 121M. To do. When forming an n-type ion-implanted region, P (phosphorus) is used as the impurity element to be ion-implanted, and when forming a p-type ion-implanted region, the impurities to be ion-implanted. Al (aluminum) is used as the element. Since the ion implantation mask 121M is made of polyimide, which is a heat-resistant organic film 121, it does not deform or deteriorate even when heated to about 400 ° C. Further, in the ion implantation mask 121M, since the main surface 10a of the SiC substrate 10 is exposed, it is not necessary to particularly increase the implantation energy at the time of ion implantation. Further, since the depth of the formed ion implantation region 111 does not vary, it is possible to prevent variations in the characteristics of the manufactured semiconductor device and reduction in yield.

Next, as shown in FIG. 15, the ion implantation mask 121M is removed using an organic solvent. The ion implantation mask 121M may be removed by ashing or the like.

(Semiconductor device)
Next, as an example of the method for manufacturing a semiconductor device in the present embodiment including the above-mentioned ion implantation, a case where the manufactured semiconductor device is a Schottky barrier diode will be described. The semiconductor device manufactured by the method for manufacturing the semiconductor device in the present embodiment may be a transistor or the like.

First, as shown in FIG. 16, the SiC substrate 10 is formed by epitaxially growing an n-type drift layer 101 on the main surface 100a of the silicon carbide single crystal substrate 100 doped with an n-type impurity element at a high concentration. To form.

Next, as shown in FIG. 17, by using the ion implantation mask in the present embodiment described above to ion-implant Al as an impurity element into the drift layer 101 from the main surface 10a side of the SiC substrate 10, ions are implanted. The implantation region 112 is formed. After ion-implanting Al, heat treatment is performed in an argon atmosphere to activate the injected Al ions.

Next, in the step shown in FIG. 18, a Schottky electrode 130 is formed on the surface of the drift layer 101 which is the main surface 10a of the SiC substrate 10 by, for example, Ti, and further, on the Schottky electrode 130, for example, Al. The wiring 131 is formed by The Schottky electrode 130 is formed so as to partially cover the surface of the ion implantation region 112. Further, the protective film 140 is formed of polyimide so as to cover the end of the wiring 131, the end of the Schottky electrode 130, and the surface of the ion implantation region 112.

Next, as shown in FIG. 19, the main surface 10b on the side opposite to the main surface 10a of the SiC substrate 10 is polished to reduce the thickness of the SiC substrate 10, and then the ohmic electrode 150 is formed on the main surface 10b. .. Polishing is performed until the thickness of the SiC substrate 10 is about 150 μm. After that, a metal film of Ni, Ti, Mo, W, Ta or the like is formed on the polished main surface 10b and heated to silicide the metal film to form an ohmic electrode 150. The film thickness of the metal film to be formed is, for example, 100 nm. In FIG. 19, the appearance of the SiC substrate 10 being thinned by polishing is omitted for convenience.

Through the above steps, a Schottky barrier diode can be manufactured by the method for manufacturing a semiconductor device according to the present embodiment.

Although the embodiments have been described in detail above, the embodiments are not limited to the specific embodiments, and various modifications and changes can be made within the scope of the claims.

10 SiC substrate 10a, 10b Main surface 11, 12 Ion implantation region 20 Oxidation film 20a Surface 20b Opening 20M, 22M Ion implantation mask 21 Polysilicon film 22 Oxidation film 22a Surface 22b Opening 30 Resist pattern 30a Opening 100 Silicon carbide single Crystal substrate 100
100a Main surface 101 Drift layer 111, 112 Ion implantation region 121 Heat resistant organic film 121a Surface 121b Opening 121M Ion implantation mask 122 Insulating film 122a Surface 122b Opening 130 Schottky electrode 131 Wiring 140 Protective film 150 Ohmic electrode

Claims (5)

The process of preparing the semiconductor substrate and
A step of forming a heat-resistant organic film on the main surface of the semiconductor substrate, and
The step of forming an insulating film on the heat-resistant organic film and
A step of forming a resist pattern having an opening on the insulating film and
A step of removing the insulating film at the opening of the resist pattern and forming an opening in the insulating film.
A step of forming an ion implantation mask made of the heat-resistant organic film by removing the heat-resistant organic film at the opening of the insulating film by etching using plasma containing oxygen.
A step of heating the semiconductor substrate and ion-implanting an impurity element into the semiconductor substrate using the ion implantation mask.
A method for manufacturing a semiconductor device having. The method for manufacturing a semiconductor device according to claim 1, wherein the heat-resistant organic film is made of polyimide. The method for manufacturing a semiconductor device according to claim 1 or 2, wherein the insulating film is a film containing silicon oxide or silicon nitride. The method for manufacturing a semiconductor device according to any one of claims 1 to 3, wherein the semiconductor substrate is a silicon carbide substrate. The method for manufacturing a semiconductor device according to any one of claims 1 to 4, wherein the insulating film is removed by dry etching.

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