JP7230909B2 - Method for manufacturing silicon carbide semiconductor device - Google Patents

Description

The present disclosure relates to a method for manufacturing a silicon carbide semiconductor device.

This application claims priority based on Japanese Patent Application No. 2018-103115 filed on May 30, 2018, and incorporates all the descriptions described in the Japanese Patent Application.

Silicon carbide has a wider bandgap than silicon, which has been widely used in semiconductor devices, and is therefore used in high-voltage semiconductor devices and the like. When manufacturing such a semiconductor device using silicon carbide, alignment is performed and processes such as ion implantation and etching are performed.

Japanese Patent Application Laid-Open No. 2015-2198

According to one aspect of the present embodiment, a silicon carbide epitaxial film is formed on a silicon carbide crystal substrate on which a concave first alignment mark is formed, thereby forming a silicon carbide epitaxial film on the first alignment mark. The method includes forming a concave second alignment mark on the surface of the film, and applying a first photoresist on the surface of the silicon carbide epitaxial film. removing the first photoresist in areas containing the second alignment marks to form first openings; aligning to form a second opening in the first photoresist.

FIG. 1 is an explanatory diagram (1) of alignment marks in a semiconductor device. FIG. 2 is an explanatory diagram (2) of alignment marks in a semiconductor device. FIG. 3 is an explanatory diagram (3) of alignment marks in a semiconductor device. FIG. 4 is an explanatory diagram (4) of alignment marks in a semiconductor device. FIG. 5 is an explanatory diagram (5) of alignment marks in a semiconductor device. FIG. 6A is an explanatory diagram (1) of the method for manufacturing a semiconductor device according to the first embodiment of the present disclosure; FIG. 6B is an explanatory diagram (2) of the method for manufacturing the semiconductor device according to the first embodiment of the present disclosure. FIG. 7A is an explanatory diagram (3) of the method for manufacturing the semiconductor device according to the first embodiment of the present disclosure; FIG. 7B is an explanatory diagram (4) of the method for manufacturing the semiconductor device according to the first embodiment of the present disclosure. FIG. 8A is an explanatory diagram (5) of the method for manufacturing the semiconductor device according to the first embodiment of the present disclosure. FIG. 8B is an explanatory diagram (6) of the method for manufacturing the semiconductor device according to the first embodiment of the present disclosure. FIG. 9A is an explanatory diagram (7) of the method for manufacturing the semiconductor device according to the first embodiment of the present disclosure. FIG. 9B is an explanatory diagram (8) of the method for manufacturing the semiconductor device according to the first embodiment of the present disclosure. FIG. 10A is an explanatory diagram (1) of the method for manufacturing a semiconductor device according to the second embodiment of the present disclosure. FIG. 10B is an explanatory diagram (2) of the method for manufacturing a semiconductor device according to the second embodiment of the present disclosure. FIG. 11A is an explanatory diagram (3) of the method for manufacturing a semiconductor device according to the second embodiment of the present disclosure. FIG. 11B is an explanatory diagram (4) of the method for manufacturing a semiconductor device according to the second embodiment of the present disclosure. FIG. 12A is an explanatory diagram (5) of the method for manufacturing a semiconductor device according to the second embodiment of the present disclosure. FIG. 12B is an explanatory diagram (6) of the method for manufacturing a semiconductor device according to the second embodiment of the present disclosure. FIG. 13A is an explanatory diagram (1) of the method for manufacturing a semiconductor device according to the third embodiment of the present disclosure; FIG. 13B is an explanatory diagram (2) of the method for manufacturing a semiconductor device according to the third embodiment of the present disclosure; 14A is an explanatory diagram (3) of the method for manufacturing a semiconductor device according to the third embodiment of the present disclosure; FIG. 14B is an explanatory diagram (4) of the method for manufacturing a semiconductor device according to the third embodiment of the present disclosure; FIG. FIG. 15A is an explanatory diagram (5) of the method for manufacturing a semiconductor device according to the third embodiment of the present disclosure. FIG. 15B is an explanatory diagram (6) of the method for manufacturing a semiconductor device according to the third embodiment of the present disclosure. FIG. 16A is an explanatory diagram (7) of the method for manufacturing a semiconductor device according to the third embodiment of the present disclosure; FIG. 16B is an explanatory diagram (8) of the method for manufacturing a semiconductor device according to the third embodiment of the present disclosure; FIG. 17A is an explanatory diagram (9) of the method for manufacturing a semiconductor device according to the third embodiment of the present disclosure; 17B is an explanatory diagram (10) of the method for manufacturing a semiconductor device according to the third embodiment of the present disclosure; FIG. FIG. 18A is an explanatory diagram (11) of the method for manufacturing a semiconductor device according to the third embodiment of the present disclosure. FIG. 18B is an explanatory diagram (12) of the method for manufacturing a semiconductor device according to the third embodiment of the present disclosure. FIG. 19A is an explanatory diagram (13) of the method for manufacturing a semiconductor device according to the third embodiment of the present disclosure. FIG. 19B is an explanatory diagram (14) of the method for manufacturing a semiconductor device according to the third embodiment of the present disclosure.

In a manufacturing process of a silicon carbide semiconductor device, alignment is performed using alignment marks as a reference, and various manufacturing processes are performed. Such alignment marks are formed on the surface of the silicon carbide substrate by recesses and protrusions having a predetermined shape. However, when a silicon carbide film or the like is formed on the alignment marks, the shape of the alignment marks changes. and may not be able to perform accurate alignment.

Therefore, there is a need for a method of manufacturing a silicon carbide semiconductor device that can perform accurate alignment using alignment marks in the manufacturing process of the silicon carbide semiconductor device.

According to the present disclosure, it is possible to provide a method for manufacturing a silicon carbide semiconductor device that enables accurate alignment using alignment marks in the manufacturing process of the silicon carbide semiconductor device.

The form for carrying out is demonstrated below.

[Description of Embodiments of the Present Disclosure]
First, the embodiments of the present disclosure are listed and described. In the following description, the same or corresponding elements are given the same reference numerals and the same descriptions thereof are not repeated. In the crystallographic description of this specification, [ ] indicates an individual orientation, <> indicates an aggregate orientation, ( ) indicates an individual plane, and { } indicates an aggregate plane. Here, the fact that the crystallographic index is negative is usually expressed by attaching a "-" (bar) above the number, but in this specification, by attaching a negative sign in front of the number It represents the crystallographic negative exponent. Also, the epitaxial growth of the present disclosure is homoepitaxial growth.

[1] A semiconductor device according to an aspect of the present disclosure is provided by forming a silicon carbide epitaxial film on a silicon carbide crystal substrate in which a concave first alignment mark is formed, thereby forming a silicon carbide epitaxial film on the first alignment mark. forming a concave second alignment mark on the surface of the silicon carbide epitaxial film above; applying a first photoresist to the surface of the silicon carbide epitaxial film; and forming the second alignment mark. removing the first photoresist in a region to form a first opening; performing alignment using the second alignment mark exposed in the first opening; and forming a second opening in the first photoresist.

When manufacturing a silicon carbide semiconductor device, the inventor of the present application forms a silicon carbide epitaxial film on a silicon carbide crystal substrate having a concave alignment mark formed thereon, and further coats a photoresist, whereby the alignment mark is recognized. As a result, we learned that it would be difficult for Further, the alignment marks appearing on the surface of such a silicon carbide epitaxial film are easier to recognize when the photoresist is not applied than when the photoresist is applied.

The present application is based on the knowledge thus obtained by the inventor. Specifically, after applying a photoresist to the silicon carbide crystal substrate on which the concave alignment mark is formed, the first opening is formed by removing the photoresist in the region where the concave alignment mark is formed. forming and exposing the alignment marks. In subsequent exposure or the like, alignment is performed with reference to the first alignment mark exposed in the first opening. Thereby, the second opening of the photoresist can be formed at an accurate position. By forming a new alignment mark or processing the silicon carbide epitaxial film using the second opening thus formed, it is possible to manufacture silicon carbide semiconductor devices with a high yield.

[2] after the step of forming the second opening, removing part of the silicon carbide epitaxial film in the second opening to form a third alignment mark; and removing the photoresist.

[3] After the step of removing the first photoresist, applying a second photoresist to the surface of the silicon carbide epitaxial film; and forming a third opening in the second photoresist.

[4] A step of forming a silicon carbide epitaxial film on a silicon carbide crystal substrate on which concave first alignment marks are formed, and a step of applying a first photoresist to the surface of the silicon carbide epitaxial film. removing the first photoresist in a region including a second alignment mark formed on the surface of the silicon carbide epitaxial film above the first alignment mark to form a first opening; performing alignment using the second alignment mark exposed in the first opening to form a second opening in the first photoresist; The method includes processing the silicon carbide epitaxial film and removing the first photoresist.

[5] The processing is etching of the silicon carbide epitaxial film.

[6] The processing is ion implantation into the silicon carbide epitaxial film.

[7] The first photoresist is positive type.

[8] The first opening and the second opening are formed by exposing the first photoresist and developing the exposed first photoresist.

[9] By forming a silicon carbide epitaxial film on a silicon carbide crystal substrate on which concave first alignment marks are formed, the surface of the silicon carbide epitaxial film above the first alignment marks is concave. forming a second alignment mark; applying a first photoresist to the surface of the silicon carbide epitaxial film; and removing the first photoresist in a region including the second alignment mark. forming a first opening; and performing alignment using the second alignment mark exposed in the first opening to form a second opening in the first photoresist. and, after the step of forming the second opening, removing a portion of the silicon carbide epitaxial film in the second opening to form a third alignment mark. and removing the first photoresist, after the step of removing the first photoresist, applying a second photoresist to the surface of the silicon carbide epitaxial film; aligning using the third alignment mark to form a third opening in the second photoresist, wherein the first photoresist is positive, The first opening and the second opening are formed by exposing the first photoresist and developing the exposed first photoresist.

[10] A step of forming a silicon carbide epitaxial film on a silicon carbide crystal substrate on which concave first alignment marks are formed, and a step of applying a first photoresist to the surface of the silicon carbide epitaxial film. removing the first photoresist in a region including a second alignment mark formed on the surface of the silicon carbide epitaxial film above the first alignment mark to form a first opening; performing alignment using the second alignment mark exposed in the first opening to form a second opening in the first photoresist; processing the silicon carbide epitaxial film; and removing the first photoresist, wherein the first photoresist is a positive type, and the first opening and the first 2 openings are formed by exposing the first photoresist and developing the exposed first photoresist.

[Details of the embodiment of the present disclosure]
An embodiment of the present disclosure (hereinafter referred to as "the present embodiment") will be described in detail below, but the present embodiment is not limited thereto.

First, an alignment mark formed in a manufacturing process of a silicon carbide semiconductor device will be described. Alignment marks for manufacturing a semiconductor device include convex alignment mark 11 projecting from main surface 10a of silicon carbide single crystal substrate 10 shown in FIG. 1 and silicon carbide single crystal substrate shown in FIG. There is a concave alignment mark 12 which is concave with respect to the main surface 10a of 10 .

When manufacturing a silicon carbide semiconductor device, a silicon carbide epitaxial film or the like may be formed by epitaxial growth on main surface 10a of silicon carbide single-crystal substrate 10. In this case, the shape of the alignment mark may change. There is Specifically, silicon carbide epitaxial film 20 is formed on main surface 10a of silicon carbide single crystal substrate 10 on which convex alignment mark 11 having a rectangular cross section as shown in FIG. 1 is formed. In this case, as shown in FIG. 3, on surface 20a of silicon carbide epitaxial film 20, alignment mark 21 appears in the region where convex alignment mark 11 was formed. The alignment mark 21 has a mountain-shaped cross section with an inclined surface 21a, and is different in shape from the alignment mark 11 shown in FIG.

A silicon carbide epitaxial film 20 is formed on main surface 10a of silicon carbide single crystal substrate 10 on which concave alignment mark 12 having a rectangular cross section as shown in FIG. 2 is formed. In this case, as shown in FIG. 4, on surface 20a of silicon carbide epitaxial film 20, alignment mark 22 appears in the region where concave alignment mark 12 was formed. The alignment mark 22 has a cross-sectional shape with inclined surfaces 22a and 22b that are not perpendicular to the main surface 10a, and is different in shape from the alignment mark 12 shown in FIG.

As a result of examination, it is possible to recognize the alignment mark 22 even if the alignment mark 21 cannot be recognized by an exposure apparatus such as a stepper. Therefore, the alignment marks 22 are easier to recognize than the alignment marks 21 . Therefore, alignment marks formed on main surface 10a of silicon carbide single-crystal substrate 10 are concave alignment marks 12 as shown in FIG. 2 rather than convex alignment marks 11 as shown in FIG. preferable.

By the way, in such an alignment mark 22, when a photoresist 30 or the like is applied to the surface 20a of the silicon carbide epitaxial film 20 as shown in FIG. 5, the alignment mark 22 may not be recognized. If alignment mark 22 is not recognized in this manner, alignment cannot be performed, and a silicon carbide semiconductor device cannot be manufactured. When the photoresist 30 is applied in this manner, the alignment marks 22 are not recognized because the alignment light interferes with the surface of the photoresist 30 and the gently inclined portions such as the inclined surfaces 22a and 22b. It is speculated that This is because interference between the surface of the photoresist 30 and the gently inclined portions such as the inclined surfaces 22a and 22b causes the light amount of the alignment light to change gradually and continuously over a wide range.

Alignment using alignment marks by an exposure apparatus such as a stepper includes a rough alignment function for performing rough alignment and a fine alignment function for performing accurate alignment. In the rough alignment, only rough alignment can be performed, but even if the alignment conditions are loose and the photoresist 30 or the like is applied to the surface 20a of the silicon carbide epitaxial film 20 as shown in FIG. 5, the alignment marks cannot be recognized. Alignment is possible. On the other hand, in fine alignment, alignment conditions are strict for accurate alignment. cannot match.

In an actual manufacturing process of a silicon carbide semiconductor device, rough alignment is performed and rough alignment is performed, then fine adjustment is performed by fine alignment, accurate alignment is performed, and exposure is performed. Therefore, in general, when a silicon carbide semiconductor device is manufactured, fine alignment is performed. Therefore, in the present application, simply describing alignment may mean fine alignment.

Therefore, even if the silicon carbide epitaxial film 20 is formed on the silicon carbide single crystal substrate 10 having the concave alignment mark 12 formed thereon and the photoresist is applied, the silicon carbide semiconductor device can be positioned by alignment. A manufacturing method is needed.

[First Embodiment]
Next, a method for manufacturing the silicon carbide semiconductor device according to the first embodiment will be described with reference to FIGS. 6A to 9B.

First, as shown in FIG. 6A , concave first alignment mark 111 is formed on main surface 110 a of silicon carbide single crystal substrate 110 . Specifically, a photoresist is applied to main surface 110a of silicon carbide single-crystal substrate 110, and exposure and development are performed by an exposure apparatus, thereby forming openings in regions where concave first alignment marks 111 are formed. A resist pattern (not shown) is formed. After that, silicon carbide single crystal substrate 110 is removed from a region where the resist pattern is not formed by dry etching such as RIE (Reactive Ion Etching) to form concave first alignment mark 111 . After that, the resist pattern (not shown) is removed. The concave first alignment mark 111 formed in this manner has a depth d to the bottom of about 1 μm.

When the silicon carbide single crystal substrate 110 is removed by dry etching, SF ₆ +O ₂ is used as an etching gas, applied power is 800 W, bias power is 40 W, and the pressure in the chamber of the dry etching apparatus is 1 Pa. . When removing the resist pattern, after removing the resist pattern by oxygen ashing, SPM cleaning and RCA cleaning are performed.

Silicon carbide single-crystal substrate 110 has main surface 110a inclined by off angle θ from a predetermined crystal plane. The predetermined crystal plane is preferably the (0001) plane or the (000-1) plane. The polytype of silicon carbide in silicon carbide single crystal substrate 110 is 4H. This is because 4H polytype silicon carbide is superior to other polytypes in terms of electron mobility, dielectric breakdown field strength, and the like. Silicon carbide single crystal substrate 110 has a diameter of 150 mm or more (for example, 6 inches or more). This is because the larger the diameter, the more advantageous it is for reducing the manufacturing cost of the semiconductor device. Silicon carbide single crystal substrate 110 has main surface 110a inclined in the <11-20> orientation at an off angle θ of 4° with respect to the {0001} plane. Incidentally, in the present embodiment, the off angle θ may exceed 0° and may be 6° or less.

Next, as shown in FIG. 6B, silicon carbide epitaxial film 120 is formed on main surface 110a of silicon carbide single crystal substrate 110 by epitaxial growth. The film thickness of silicon carbide epitaxial film 120 to be formed is 1 μm to 3 μm. As a result, on surface 120a of silicon carbide epitaxial film 120, second alignment mark 121 appears in the region where concave first alignment mark 111 was formed. The second alignment mark 121 has a cross-sectional shape with an inclined surface that is inclined with respect to the surface 120a.

Next, as shown in FIG. 7A, first photoresist 130 is applied to surface 120a of silicon carbide epitaxial film 120 . The first photoresist 130 is applied by a spin coater or the like so as to have a film thickness of about 2 μm. Thereby, second alignment marks 121 appearing on surface 120a of silicon carbide epitaxial film 120 are embedded in first photoresist 130, and the surface of first photoresist 130 is flattened. In addition, baking etc. are performed as needed. In the present application, a positive photoresist is used for the first photoresist 130 .

Next, as shown in FIG. 7B, a first opening 131 of first photoresist 130 is formed in a region including the entirety of second alignment mark 121 on surface 120a of silicon carbide epitaxial film 120. Next, as shown in FIG. Specifically, the first opening 131 of the first photoresist 130 is formed by performing exposure and development using an exposure device. A stepper with a wavelength of 365 nm (i-line) is used as the exposure device, and an alkaline solution such as TMAH (tetramethylammonium hydroxide) is used as the developer. The first opening 131 is wider than the outline of the second alignment mark 121 by about 10 μm. Therefore, by forming first opening 131 , second alignment mark 121 on surface 120 a of silicon carbide epitaxial film 120 is exposed in first opening 131 . It should be noted that, when forming the first opening 131, it is necessary to perform alignment, and this alignment is performed by rough alignment of a stepper, visual inspection, or the like.

Next, as shown in FIG. 8A, a second opening 132 is formed in the first photoresist 130 in a region where a concave third alignment mark 122 to be described later is to be formed. Specifically, alignment is performed using the second alignment marks 121 exposed in the first openings 131 of the first photoresist 130, and exposure and development are performed by an exposure device. Thereby, a second opening 132 of the first photoresist 130 is formed at a predetermined position. A stepper with a wavelength of 365 nm is used as the exposure device, and an alkaline solution such as TMAH is used as the developer. In this step, since the second alignment marks 121 exposed in the first openings 131 of the first photoresist 130 can be used, accurate alignment can be performed by fine alignment. Thereby, the second opening 132 can be accurately formed in the desired position of the first photoresist 130 .

Next, as shown in FIG. 8B, a concave third alignment mark 122 is formed by removing a portion of the silicon carbide epitaxial film 120 exposed in the second opening 132 of the first photoresist 130 . to form Specifically, the silicon carbide epitaxial film 120 exposed in the second opening 132 of the first photoresist 130 is removed by dry etching such as RIE, thereby forming the concave third alignment mark 122 . Form. The depth to the bottom of the concave third alignment mark 122 formed in this manner is about 0.5 μm to 1.0 μm. Such concave third alignment mark 122 may be formed in a region that will be a scribe line cut by a dicing saw when manufacturing a silicon carbide semiconductor device. When removing the silicon carbide epitaxial film 120, SF ₆ +O ₂ is used as an etching gas, applied power: 800 W, bias power: 40 W, pressure in the chamber of the dry etching apparatus: 1 Pa. At this time, silicon carbide epitaxial film 120 in the region where second alignment mark 121 is formed and exposed in first opening 131 of first photoresist 130 is also partially removed at the same time. This does not interfere with the manufacture of semiconductor devices.

Next, as shown in FIG. 9A, the first photoresist 130 is removed. When removing the first photoresist 130, after removing the first photoresist 130 by oxygen ashing, SPM cleaning and RCA cleaning are performed. In subsequent manufacturing steps of the silicon carbide semiconductor device, alignment is performed using the formed concave third alignment marks 122, whereby accurate alignment can be performed, and the desired silicon carbide semiconductor device can be obtained. can be manufactured with high yield.

Specifically, the concave third alignment mark 122 is a rectangular concave alignment mark, and then, as shown in FIG. 9B, even if the second photoresist 140 is applied, Alignment by fine alignment by an exposure apparatus is possible. Therefore, by performing alignment using concave third alignment mark 122 and performing exposure, silicon carbide semiconductor devices can be manufactured with a high yield.

[Second embodiment]
Next, a method for manufacturing a silicon carbide semiconductor device according to the second embodiment will be described with reference to FIGS. 10A to 12B.

First, as shown in FIG. 10A , concave first alignment mark 111 is formed on main surface 110 a of silicon carbide single crystal substrate 110 .

Next, as shown in FIG. 10B, silicon carbide epitaxial film 120 is formed on main surface 110a of silicon carbide single crystal substrate 110 by epitaxial growth.

Next, as shown in FIG. 11A , first photoresist 130 is applied to surface 120a of silicon carbide epitaxial film 120 .

Next, as shown in FIG. 11B , first opening 131 of first photoresist 130 is formed in surface 120 a of silicon carbide epitaxial film 120 in a region including second alignment mark 121 entirely.

Next, as shown in FIG. 12A, a second opening 232 is formed in first photoresist 130 in a region where n ⁺ region 221 of silicon carbide epitaxial film 120 to be described later is to be formed. Specifically, alignment is performed using the second alignment marks 121 exposed in the first openings 131 of the first photoresist 130, and exposure and development are performed by an exposure device. Thereby, a second opening 232 of the first photoresist 130 is formed at a predetermined position. In this step, since the second alignment marks 121 exposed in the first openings 131 of the first photoresist 130 can be used, accurate alignment can be performed by fine alignment. Thereby, the second opening 232 can be accurately formed in the desired position of the first photoresist 130 .

Next, as shown in FIG. 12B, an n-type impurity element is ion-implanted into the silicon carbide epitaxial film 120 exposed in the second opening 232 of the first photoresist 130 to obtain an n ⁺ A region 221 is formed. P is used as an n-type impurity element, and ion implantation is performed under the conditions of acceleration energy of 10 keV to 900 keV and dose of 1×10 ¹¹ cm ⁻² to 1×10 ¹⁶ cm ⁻² . Incidentally, when forming a p ⁺ region instead of the n ⁺ region 221 in the silicon carbide epitaxial film 120, the impurity element to be ion-implanted is Al. After that, the first photoresist 130 is removed.

In the method for manufacturing a silicon carbide semiconductor device in the present embodiment, second opening 232 of first photoresist 130 is formed in a so-called element region. Further, in the present embodiment, trenches and the like are formed by removing by etching the silicon carbide epitaxial film 120 in the region where the second opening 232 of the first photoresist 130 is formed. good.

Contents other than the above are the same as in the first embodiment.

[Third Embodiment]
Next, a method for manufacturing a silicon carbide semiconductor device according to the third embodiment will be described with reference to FIGS. 13A to 19B.

First, as shown in FIG. 13A , concave first alignment mark 111 is formed on main surface 110 a of silicon carbide single crystal substrate 110 .

Next, as shown in FIG. 13B, silicon carbide epitaxial film 120 is formed on main surface 110a of silicon carbide single crystal substrate 110 by epitaxial growth.

Next, as shown in FIG. 14A , first photoresist 130 is applied to surface 120a of silicon carbide epitaxial film 120 .

Next, as shown in FIG. 14B, a first opening 131 of first photoresist 130 is formed in a region including the entirety of second alignment mark 121 on surface 120a of silicon carbide epitaxial film 120. Next, as shown in FIG.

Next, as shown in FIG. 15A, a second opening 132 is formed in the first photoresist 130 in a region where a concave third alignment mark 122 to be described later is to be formed.

Next, as shown in FIG. 15B, the silicon carbide epitaxial film 120 exposed in the second opening 132 of the first photoresist 130 is removed to form a concave third alignment mark 122. .

Next, as shown in FIG. 16A, the first photoresist 130 is removed.

Next, as shown in FIG. 16B, a silicon oxide film 350 having a thickness of about 2 μm is formed on the surface 120a of the silicon carbide epitaxial film 120. Next, as shown in FIG.

Next, as shown in FIG. 17A, a photoresist 360 is applied on the silicon oxide film 350 . The thickness of the applied photoresist 360 is approximately 2.5 μm.

Next, as shown in FIG. 17B, a third opening 361 of photoresist 360 is formed in a region of silicon carbide epitaxial film 120 where n ⁺ region 321 is to be formed. Specifically, alignment is performed using concave third alignment marks 122 formed in silicon carbide epitaxial film 120 , and exposure and development are performed by an exposure device to form a third opening in photoresist 360 . A portion 361 is formed. In this step, concave third alignment mark 122 having a side surface substantially perpendicular to surface 120a of silicon carbide epitaxial film 120 can be used. Therefore, even if the silicon oxide film 350 is formed on the concave third alignment mark 122, the concave third alignment mark 122 can be recognized by the exposure apparatus. Therefore, accurate alignment can be performed by fine alignment using the concave third alignment mark 122 . Thereby, the third opening 361 can be accurately formed in the desired position of the photoresist 360 .

Next, as shown in FIG. 18A, an opening 351 is formed by removing the silicon oxide film 350 in the third opening 361 of the photoresist 360 by dry etching such as RIE. As a result, the remaining silicon oxide film 350 forms an ion implantation mask. When removing the silicon oxide film 350, a mixed gas of CF ₄ , CHF ₃ and Ar was used as an etching gas, applied power: 500 W, bias power: 50 W, pressure in the chamber of the dry etching apparatus: 1 Pa. do in As a result, silicon oxide film 350 in third opening 361 of photoresist 360 is removed until surface 120a of silicon carbide epitaxial film 120 is exposed, opening 351 is formed in silicon oxide film 350, and an ion implantation mask is used. Form.

Next, as shown in FIG. 18B, the photoresist 360 is removed. When removing the photoresist 360, after removing the photoresist 360 by oxygen ashing, SPM cleaning and RCA cleaning are performed.

Next, as shown in FIG. 19A, using the silicon oxide film 350 having the opening 351 as an ion implantation mask, an n-type impurity element is implanted into the silicon carbide epitaxial film 120 in the region to form an n ⁺ region. 321 is formed. P is used as an n-type impurity element, and ion implantation is performed under the conditions of acceleration energy of 10 keV to 900 keV and dose of 1×10 ¹¹ cm ⁻² to 1×10 ¹⁶ cm ⁻² . Incidentally, when forming a p ⁺ region instead of the n ⁺ region 321 in the silicon carbide epitaxial film 120, ions are implanted instead of P as an impurity element to Al.

Next, as shown in FIG. 19B, the silicon oxide film 350 is removed by wet etching. When removing the silicon oxide film 350, HF (hydrofluoric acid) or BHF (buffered hydrofluoric acid) is used as an etchant.

Contents other than the above are the same as in the first embodiment.

Although the embodiment has been described in detail above, it is not limited to a specific embodiment, and various modifications and changes are possible within the scope described in the claims.

10 silicon carbide single crystal substrate 10a main surface 11 convex alignment mark 12 concave alignment mark 20 silicon carbide epitaxial film 20a surface 21 alignment mark 21a inclined surface 22 alignment marks 22a, 22b inclined surface 30 photoresist 110 silicon carbide single crystal substrate 110a Main surface 111 First alignment mark 120 Silicon carbide epitaxial film 120a Surface 121 Second alignment mark 122 Third alignment mark 130 First photoresist 131 First opening 132 Second opening 140 Second opening Photoresist 221 n ⁺ region 232 Second opening 321 n ⁺ region 350 Silicon oxide film 351 Opening 360 Photo resist 361 Third opening

Claims (10)

By forming a silicon carbide epitaxial film on a silicon carbide crystal substrate on which concave first alignment marks are formed, concave second alignment marks are formed on the surface of the silicon carbide epitaxial film above the first alignment marks. a step of forming an alignment mark of
applying a first photoresist to the surface of the silicon carbide epitaxial film;
removing the first photoresist in a region containing the second alignment mark to form a first opening;
aligning using the second alignment mark exposed in the first opening to form a second opening in the first photoresist;
A method for manufacturing a silicon carbide semiconductor device having After the step of forming the second opening,
removing a portion of the silicon carbide epitaxial film in the second opening to form a third alignment mark;
removing the first photoresist;
The method for manufacturing a silicon carbide semiconductor device according to claim 1, having After removing the first photoresist,
applying a second photoresist to the surface of the silicon carbide epitaxial film;
aligning using the third alignment mark to form a third opening in the second photoresist;
3. The method for manufacturing a silicon carbide semiconductor device according to claim 2, comprising: forming a silicon carbide epitaxial film on a silicon carbide crystal substrate on which concave first alignment marks are formed;
applying a first photoresist to the surface of the silicon carbide epitaxial film;
removing the first photoresist in a region including a second alignment mark formed on the surface of the silicon carbide epitaxial film above the first alignment mark to form a first opening;
aligning using the second alignment mark exposed in the first opening to form a second opening in the first photoresist;
processing the silicon carbide epitaxial film in the second opening;
removing the first photoresist;
A method for manufacturing a silicon carbide semiconductor device having 5. The method of manufacturing a silicon carbide semiconductor device according to claim 4, wherein said processing is etching of said silicon carbide epitaxial film. 5. The method of manufacturing a silicon carbide semiconductor device according to claim 4, wherein said processing is ion implantation into said silicon carbide epitaxial film. 7. The method of manufacturing a silicon carbide semiconductor device according to claim 1, wherein said first photoresist is positive type. The first opening and the second opening are
exposing the first photoresist;
developing the exposed first photoresist;
The method for manufacturing a silicon carbide semiconductor device according to any one of claims 1 to 7, formed by: By forming a silicon carbide epitaxial film on a silicon carbide crystal substrate on which concave first alignment marks are formed, concave second alignment marks are formed on the surface of the silicon carbide epitaxial film above the first alignment marks. a step of forming an alignment mark of
applying a first photoresist to the surface of the silicon carbide epitaxial film;
removing the first photoresist in a region containing the second alignment mark to form a first opening;
aligning using the second alignment mark exposed in the first opening to form a second opening in the first photoresist;
has
After the step of forming the second opening,
removing a portion of the silicon carbide epitaxial film in the second opening to form a third alignment mark;
removing the first photoresist;
has
After removing the first photoresist,
applying a second photoresist to the surface of the silicon carbide epitaxial film;
aligning using the third alignment mark to form a third opening in the second photoresist;
has
The first photoresist is positive type,
The first opening and the second opening are
exposing the first photoresist;
developing the exposed first photoresist;
A method for manufacturing a silicon carbide semiconductor device formed by forming a silicon carbide epitaxial film on a silicon carbide crystal substrate on which concave first alignment marks are formed;
applying a first photoresist to the surface of the silicon carbide epitaxial film;
removing the first photoresist in a region including a second alignment mark formed on the surface of the silicon carbide epitaxial film above the first alignment mark to form a first opening;
aligning using the second alignment mark exposed in the first opening to form a second opening in the first photoresist;
processing the silicon carbide epitaxial film in the second opening;
removing the first photoresist;
has
The first photoresist is positive type,
The first opening and the second opening are
exposing the first photoresist;
developing the exposed first photoresist;
A method for manufacturing a silicon carbide semiconductor device formed by

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