A method for preparing a bevel photoresist mask suitable for semiconductor processes

Abstract

This invention relates to a method for fabricating a beveled photoresist mask suitable for semiconductor processes, comprising the following steps: S1: forming a first layer of photoresist; S2: sequentially performing a first pre-bake, a first beveled patterning process, and a first post-bake on the first layer of photoresist to obtain a beveled patterned first layer of photoresist; S3: coating a second layer of photoresist onto the beveled patterned first layer of photoresist; S4: sequentially performing a second pre-bake, a second beveled patterning process, and a second post-bake on the second layer of photoresist, fusing the first and second layers of photoresist to form a beveled photoresist mask with a preset angle. Because the first post-bake enables the first layer of photoresist to have better development resistance, the first and second layers of photoresist have different development selectivity ratios, thereby achieving a wider range of bevel angles for the beveled photoresist, and further improving the adjustment range of the sidewall tilt angle of the dielectric layer to meet the angle requirements of the beveled sidewall structure.

Description

Technical Field

[0001] This invention belongs to the field of semiconductor manufacturing process technology, and specifically relates to a method for preparing a slanted photoresist mask suitable for semiconductor processes. Background Technology

[0002] In the structure of power devices such as mesa diodes and trench junction barrier Schottky diodes (TJBS), it is necessary to fabricate etched mesa or trench injection structures with tilted sidewall morphology features.

[0003] These tilted sidewall structures typically require the prior fabrication of a dielectric layer with corresponding tilted sidewalls as an etch barrier or implantation barrier, followed by a simple pattern transfer process to complete the entire structure. The dielectric layer with corresponding tilted sidewalls is fabricated using a slanted photoresist with a specific angle; the tilt angle of the dielectric layer's sidewalls depends on the angle of the slanted photoresist.

[0004] However, due to limitations in existing photolithography processes, the bevel angle range of the beveled photoresist is limited, which restricts the adjustment range of the sidewall tilt angle of the dielectric layer and fails to meet the angle requirements of the beveled sidewall structure. Summary of the Invention

[0005] To address the aforementioned problems in the prior art, this invention provides a method for fabricating a slanted photoresist mask suitable for semiconductor processes. The technical problem to be solved by this invention is achieved through the following technical solution:

[0006] This invention provides a method for preparing a slanted photoresist mask suitable for semiconductor processes, comprising the following steps:

[0007] S1: Forming the first layer of photoresist;

[0008] S2: The first layer of photoresist is sequentially subjected to a first pre-baking, a first inclined surface patterning process, and a first post-baking to obtain the first layer of photoresist with an inclined surface pattern.

[0009] S3: Apply a second layer of photoresist onto the first layer of photoresist patterned on the inclined surface;

[0010] S4: The second layer of photoresist is sequentially subjected to a second pre-bake, a second bevel patterning process, and a second post-bake. The first layer of photoresist and the second layer of photoresist are fused to form a bevel photoresist mask with a preset angle. The position of the second bevel patterning process is the same as the center of the first bevel patterning process. The preset angle is smaller than the bevel angle of the first layer of photoresist with the bevel pattern.

[0011] In one feasible manner, step S1 includes:

[0012] The first layer of photoresist is formed on the dielectric layer.

[0013] In one feasible approach, step S1 is preceded by:

[0014] Obtain a semiconductor wafer and grow a dielectric layer on the surface of the semiconductor wafer.

[0015] In one feasible embodiment, the material of the dielectric layer includes one of silicon oxide, silicon nitride, and polycrystalline silicon.

[0016] In one feasible approach, the first slope patterning process includes: a first exposure and a first development.

[0017] In one feasible manner, the second slope patterning process includes a second exposure and a second development.

[0018] In one feasible manner, the energy of the second exposure is greater than the energy of the first exposure;

[0019] The length of the second exposure window formed by the second exposure is greater than the length of the first exposure window formed by the first exposure.

[0020] In one feasible manner, the temperature of the second post-baking is higher than the temperature of the first post-baking.

[0021] In one feasible approach, the bevel angle of the first layer of photoresist patterned with bevels is greater than 80°; the preset angle is 45° to 80°.

[0022] In one feasible approach, the first and second photoresist layers are made of the same material.

[0023] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0024] This invention provides a method for fabricating a beveled photoresist mask suitable for semiconductor processes. By preparing two layers of photoresist and performing two photolithography steps, a smaller bevel angle can be achieved. Because the first post-baking process improves the development resistance of the first photoresist layer to the developer, the first and second photoresist layers have different development selectivity ratios. This allows for the fabrication of a smaller bevel angle photoresist, thereby increasing the adjustment range of the sidewall tilt angle of the dielectric layer and meeting the angle requirements of the beveled sidewall structure. Attached Figure Description

[0025] Figure 1 This is a flowchart illustrating the steps of a method for preparing a slanted photoresist mask suitable for semiconductor processes, as provided in an embodiment of the present invention.

[0026] Figures 2a-2eThis is a structural diagram illustrating the steps of a method for fabricating a slanted photoresist mask suitable for semiconductor processes, provided by an embodiment of the present invention.

[0027] Figure label:

[0028] 1: Semiconductor wafer; 2: Dielectric layer; 3: First photoresist layer; 4: Second photoresist layer; 5: Second exposure window; 6: Slanted photoresist mask. Detailed Implementation

[0029] The present invention will be further described in detail below with reference to specific embodiments, but the implementation of the present invention is not limited thereto.

[0030] Example 1

[0031] Please see Figure 1 and Figures 2a-2e , Figure 1 This is a flowchart illustrating the steps of a method for fabricating a slanted photoresist mask suitable for semiconductor processes, as provided in an embodiment of the present invention. Figures 2a-2e This is a structural diagram illustrating the steps of a method for fabricating a slanted photoresist mask suitable for semiconductor processes, provided by an embodiment of the present invention.

[0032] This embodiment provides a method for preparing a slanted photoresist mask suitable for semiconductor processes, comprising the following steps:

[0033] Step 1: Obtain semiconductor wafer 1 and grow dielectric layer 2 on the surface of semiconductor wafer 1.

[0034] like Figure 2a As shown, one of Si, SiC, and GaN is obtained as semiconductor wafer 1. A dielectric layer 2 is grown on the surface of semiconductor wafer 1. In this embodiment, the material of dielectric layer 2 includes one of silicon oxide, silicon nitride, and polycrystalline silicon.

[0035] Step 2: Form the first layer of photoresist 3.

[0036] In this embodiment, the dielectric layer 2 is the dielectric layer to be etched, and a first layer of photoresist 3 is formed on the dielectric layer 2.

[0037] Step 3: Perform the first pre-baking, the first bevel patterning, and the first post-baking on the first layer of photoresist 3 in sequence to obtain the bevel patterned first layer of photoresist 3.

[0038] In this embodiment, the first slope patterning process includes: a first exposure and a first development.

[0039] Specifically, such as Figure 2bAs shown, the first layer of photoresist 3 undergoes a first pre-baking process. After pre-baking, the first layer of photoresist 3 is exposed for the first time to form a first exposure window. The first layer of photoresist 3 then undergoes a first development process to remove the photoresist from the first exposure window, forming a first beveled window. After development, the first layer of photoresist 3 undergoes a first post-baking process to obtain a beveled patterned first layer of photoresist 3. In this step, the bevel angle θ1 of the beveled patterned first layer of photoresist 3 is greater than 80°. In this embodiment, the bevel angle is the angle between the bevel and the plane of the dielectric layer 2.

[0040] In one feasible embodiment, the first photoresist layer 3 is of type AZ4330, the thickness of the first photoresist layer 3 is 1-2 μm, the temperature of the first pre-baking is 100-110°C, the time of the first pre-baking is 60-90 s, the energy of the first exposure is 100-120 mJ, the length of the first exposure window formed by the first exposure is 1-2 μm, the developer for the first development is AZ300MIF, the time of the first development is 100-120 s, the temperature of the first post-baking is 110-120°C, the time of the first post-baking is 90-120 s, and the slope angle θ1 of the first photoresist layer 3 with the formed slope pattern is 80-90°.

[0041] Step 4: Apply a second layer of photoresist 4 onto the first layer of photoresist 3 patterned on the bevel.

[0042] Specifically, such as Figure 2c As shown, due to the presence of the first inclined window in the first layer of photoresist 3, the second layer of photoresist 4 fills the first inclined window, and the thickness of the second layer of photoresist 4 at the first inclined window is thicker than that in other areas.

[0043] S4: The second layer of photoresist 4 is sequentially subjected to a second pre-bake, a second inclined patterning process, and a second post-bake. The first layer of photoresist 3 and the second layer of photoresist 4 are fused to form an inclined photoresist mask 6 with a preset angle. The position of the second inclined patterning process is the same as the position of the first inclined patterning process. The preset angle is smaller than the inclined angle of the first layer of photoresist 3 with the inclined pattern.

[0044] In this embodiment, the first photoresist layer 3 and the second photoresist layer 4 are made of the same material. The second bevel patterning process includes a second exposure and a second development. The energy of the second exposure is greater than that of the first exposure. The temperature of the second post-baking is higher than that of the first post-baking. The position of the second bevel patterning process is aligned with the center of the first bevel patterning process, that is, the center of the second bevel patterning is aligned with the center of the first bevel patterning.

[0045] Specifically, such as Figure 2dAs shown, the second exposure window 5 formed by the second exposure is located on top of the first exposure window, and the length of the second exposure window 5 is greater than the length of the first exposure window. Because the second layer of photoresist 4 in the second exposure window 5 is thicker, the energy of the second exposure is greater than that of the first exposure, ensuring that the second layer of photoresist 4 in the second exposure window 5 is fully exposed. Furthermore, due to the greater diffraction energy of the second exposure, the actual exposure width of the surface layer of the second layer of photoresist 4 is greater than the width of the bottom layer. The first layer of photoresist 3, having undergone the first post-baking process, is unaffected by the second exposure. During the second development, because the first layer of photoresist 3 has undergone the first post-baking treatment, it has better resistance to development by the developer. The first layer of photoresist 3 and the second layer of photoresist 4 have different development selectivity ratios; therefore, the development consumption of the first layer of photoresist 3 is much less than the development consumption of the second layer of photoresist 4. A second beveled window with a smaller bevel angle than the first beveled window can be formed in the second exposure window 5.

[0046] Furthermore, because the temperature of the second post-drying is higher than that of the first post-drying, such as Figure 2e As shown, during the second post-bake, the second layer of photoresist 4 flows, and the first layer of photoresist 3 and the second layer of photoresist 4 fuse into one layer, forming a photolithographic window with a preset angle at the second beveled window. The preset angle θ2 formed in this step is 45° to 80°. When the dielectric layer 2 is etched using the beveled photoresist mask 6 provided in this embodiment, an etched structure with a sidewall tilt angle of 45° to 80° can be formed.

[0047] In one feasible embodiment, the second photoresist layer 4 is of type AZ4330, with a thickness of 1–2 μm. The second pre-baking temperature is 100–110°C, the second pre-baking time is 1–2 μm, the second exposure energy is 110–130 mJ, the length of the second exposure window formed in the second exposure is 1–2 μm, the second development solution is AZ300MIF, the second development time is 110–120 s, the second post-baking temperature is 120–130°C, the second post-baking time is 90–120 s, and the formed preset angle θ2 is 45°–80°. Furthermore, when the second post-baking temperature is 120–130°C, the formed preset angle θ2 is 45°.

[0048] This embodiment provides a method for fabricating a beveled photoresist mask suitable for semiconductor processes. By preparing two layers of photoresist and performing two photolithography steps, a smaller bevel angle can be achieved. Because the first post-baking process improves the development resistance of the first photoresist layer to the developer, the first and second photoresist layers have different development selectivity ratios, thus enabling the fabrication of a smaller bevel angle photoresist. This, in turn, increases the adjustment range of the sidewall tilt angle of the dielectric layer, meeting the angle requirements of the beveled sidewall structure. The fabrication method provided in this embodiment requires only one type of photoresist to achieve a wider bevel angle range in photolithography, avoiding the mixing of photoresists with different photosensitivity and viscosity, reducing the types and costs of consumables. It also avoids the multi-path, multi-parameter problems associated with spin coating equipment to accommodate different photoresists, reducing equipment costs and improving the process window.

[0049] The above description, in conjunction with specific preferred embodiments, provides a further detailed explanation of the present invention. It should not be construed that the specific implementation of the present invention is limited to these descriptions. For those skilled in the art, various simple deductions or substitutions can be made without departing from the concept of the present invention, and all such modifications and substitutions should be considered within the scope of protection of the present invention.

Claims

1. A method for fabricating a slanted photoresist mask suitable for semiconductor processes, characterized in that, Includes the following steps: S1: Formation of the first layer of photoresist; S2: The first layer of photoresist is sequentially subjected to a first pre-baking, a first inclined surface patterning process, and a first post-baking to obtain the first layer of photoresist with an inclined surface pattern. The first slope patterning process includes the first exposure and the first development; S3: Apply a second layer of photoresist onto the first layer of photoresist patterned on the inclined surface; S4: The second layer of photoresist is sequentially subjected to a second pre-baking, a second inclined patterning process, and a second post-baking. The first layer of photoresist and the second layer of photoresist are fused to form an inclined photoresist mask with a preset angle. The second inclined patterning process includes a second exposure and a second development. The first and second photoresist layers are made of the same material; the energy of the second exposure is greater than the energy of the first exposure, and the temperature of the second post-baking is higher than the temperature of the first post-baking. The position of the second bevel patterning is the same as the center of the first bevel patterning; the preset angle is smaller than the bevel angle of the first layer of photoresist in the bevel patterning.

2. The method for preparing a slanted photoresist mask suitable for semiconductor processes according to claim 1, characterized in that, Step S1 includes: The first layer of photoresist is formed on the dielectric layer.

3. The method for preparing a slanted photoresist mask suitable for semiconductor processes according to claim 2, characterized in that, Step S1 is preceded by: Obtain a semiconductor wafer and grow a dielectric layer on the surface of the semiconductor wafer.

4. The method for preparing a slanted photoresist mask suitable for semiconductor processes according to claim 2, characterized in that, The material of the dielectric layer includes one of silicon oxide, silicon nitride, and polycrystalline silicon.

5. The method for preparing a slanted photoresist mask suitable for semiconductor processes according to claim 1, characterized in that, The length of the second exposure window formed by the second exposure is greater than the length of the first exposure window formed by the first exposure.

6. The method for preparing a slanted photoresist mask suitable for semiconductor processes according to claim 1, characterized in that, The first layer of photoresist with the beveled pattern has a bevel angle greater than 80°; the preset angle is 45° to 80°.

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