Preparation method of inclined plane photoresist mask suitable for semiconductor technology

Abstract

The invention relates to a preparation method of a slope photoresist mask applicable to a semiconductor process. The preparation method comprises the following steps: S1, forming a first layer of photoresist; s2, sequentially carrying out first-time pre-baking, first inclined plane patterning processing and first-time post-baking on the first layer of photoresist to obtain a first layer of photoresist with a patterned inclined plane; s3, coating a second layer of photoresist on the first layer of photoresist with the patterned inclined plane; and S4, carrying out second-time pre-baking, second inclined plane patterning processing and second-time post-baking on the second layer of photoresist in sequence, and fusing the first layer of photoresist and the second layer of photoresist to form an inclined plane photoresist mask with a preset angle. Due to the fact that the first-time post-baking can enable the first layer of photoresist to have better dominance resistance, the first layer of photoresist and the second layer of photoresist have different development selection ratios, a larger inclined plane angle range of inclined plane photoresist is achieved, the side wall inclination angle adjusting range of the dielectric layer is further widened, and the angle requirement of the inclined side wall structure is met.

Description

Technical Field

[0001] The invention belongs to the technical field of semiconductor manufacturing process, and in particular relates to a method for preparing a bevel photoresist mask suitable for semiconductor process. Background Art

[0002] In the structures of power devices such as mesa diodes and trench junction barrier Schottky diodes (TJBS), it is necessary to prepare etched mesas or trench implant structures with inclined sidewall morphology.

[0003] These inclined sidewall structures usually require the preparation of a dielectric layer with corresponding inclined sidewalls as an etching barrier or an injection barrier, and then the entire process structure is completed by a simple pattern transfer method. The preparation of the dielectric layer with corresponding inclined sidewalls is achieved by using a bevel photoresist with a specific angle, and the sidewall inclination angle of the dielectric layer depends on the bevel angle of the bevel photoresist.

[0004] However, due to the limitations of existing photolithography processes, the bevel angle range of the bevel photoresist is limited, resulting in a limited adjustment range of the sidewall inclination angle of the dielectric layer, which cannot meet the angle requirements of the inclined sidewall structure. Summary of the invention

[0005] In order to solve the above problems existing in the prior art, the present invention provides a method for preparing a bevel photoresist mask suitable for semiconductor processes. The technical problem to be solved by the present invention is achieved through the following technical solutions:

[0006] The present invention provides a method for preparing a bevel photoresist mask suitable for semiconductor technology, comprising the following steps:

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

[0008] S2: performing a first pre-bake, a first bevel patterning process and a first post-bake on the first layer of photoresist in sequence to obtain a first layer of photoresist with bevel patterning;

[0009] S3: coating a second layer of photoresist on the first layer of photoresist with the bevel patterning;

[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 bevel patterned first layer of photoresist.

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

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

[0013] In one achievable manner, before step S1, the method further includes:

[0014] A semiconductor wafer is obtained, and a dielectric layer is grown on the surface of the semiconductor wafer.

[0015] In one achievable manner, the material of the dielectric layer includes: one of silicon oxide, silicon nitride and polysilicon.

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

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

[0018] In one achievable 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 achievable manner, the temperature of the second post-bake is higher than the temperature of the first post-bake.

[0021] In an achievable manner, the bevel angle of the bevel patterned first layer of photoresist is greater than 80°; and the preset angle is 45° to 80°.

[0022] In one achievable manner, the first layer of photoresist and the second layer of photoresist are made of the same material.

[0023] Compared with the prior art, the present invention has the following beneficial effects:

[0024] The present invention provides a method for preparing a bevel photoresist mask suitable for semiconductor technology, which realizes a bevel photoresist with a smaller bevel angle by preparing two layers of photoresist and performing photolithography twice. Since the first post-baking can make the first layer of photoresist have better resistance to the developer, the first layer of photoresist and the second layer of photoresist have different development selection ratios, thereby realizing the preparation of a bevel photoresist with a smaller bevel angle, thereby increasing the adjustment range of the side wall inclination angle of the dielectric layer, and meeting the angle requirements of the inclined side wall structure. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 It is a flow chart of steps of a method for preparing a bevel photoresist mask suitable for semiconductor process provided by an embodiment of the present invention;

[0026] Figure 2a to Figure 2eIt is a step structure diagram of a method for preparing a bevel photoresist mask suitable for semiconductor process provided by an embodiment of the present invention.

[0027] Reference numerals:

[0028] 1: semiconductor wafer; 2: dielectric layer; 3: first photoresist layer; 4: second photoresist layer; 5: second exposure window; 6: bevel photoresist mask. DETAILED DESCRIPTION

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

[0030] Embodiment 1

[0031] See also Figure 1 and Figure 2a to Figure 2e , Figure 1 1 is a flowchart of a method for preparing a bevel photoresist mask suitable for semiconductor process provided by an embodiment of the present invention. Figure 2a to Figure 2e It is a step structure diagram of a method for preparing a bevel photoresist mask suitable for semiconductor process provided by an embodiment of the present invention.

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

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

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

[0035] Step 2: forming a first layer of photoresist 3.

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

[0037] Step three: performing a first pre-bake, a first bevel patterning process and a first post-bake on the first layer of photoresist 3 in sequence to obtain a first layer of photoresist 3 with bevel patterning.

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

[0039] Specifically, Figure 2bAs shown, the first layer of photoresist 3 is pre-baked for the first time, and after the pre-baking, the first exposure is performed on the first layer of photoresist 3 to form a first exposure window, and the first layer of photoresist 3 is developed for the first time to remove the photoresist in the first exposure window to form a first bevel window. The first layer of photoresist 3 after development is post-baked for the first time to obtain the first layer of photoresist 3 with bevel patterning. In this step, the bevel angle θ1 of the first layer of photoresist 3 with bevel patterning is greater than 80°. The bevel angle in this embodiment is the angle between the bevel and the plane of the dielectric layer 2.

[0040] In an achievable method, the model of the first layer of photoresist 3 is AZ4330, the thickness of the first layer of photoresist 3 is 1 to 2 um, the temperature of the first pre-bake is 100 to 110°C, the time of the first pre-bake is 60 to 90 s, the energy of the first exposure is 100 to 120 mJ, the length of the first exposure window formed by the first exposure is 1 to 2 um, the developer for the first development is AZ300MIF, the time of the first development is 100 to 120 s, the temperature of the first post-bake is 110 to 120°C, the time of the first post-bake is 90 to 120 s, and the bevel angle θ1 of the first layer of photoresist 3 with bevel patterning formed is 80 to 90°.

[0041] Step 4: coating a second layer of photoresist 4 on the first layer of photoresist 3 with bevel patterning.

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

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

[0044] In this embodiment, the materials of the first layer of photoresist 3 and the second layer of photoresist 4 are the same. The second bevel patterning process includes: a second exposure and a second development. The energy of the second exposure is greater than the energy of the first exposure. The temperature of the second post-bake is higher than the temperature of the first post-bake. 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, Figure 2dAs shown, the second exposure window 5 formed by the second exposure is located on the first exposure window, and the length of the second exposure window 5 is greater than that of the first exposure window. Since the thickness of the second layer of photoresist 4 in the second exposure window 5 is relatively thick, the energy of the second exposure is greater than that of the first exposure, which can ensure that the second layer of photoresist 4 in the second exposure window 5 is fully exposed. In addition, since the second exposure has a larger diffraction light energy, the actual exposure width of the surface of the second layer of photoresist 4 is greater than the width of the bottom. However, the first layer of photoresist 3 is not affected by the second exposure because the first post-baking is completed. During the second development, since the first layer of photoresist 3 has better resistance to the developer after the first post-baking treatment, the first layer of photoresist 3 and the second layer of photoresist 4 have different development selectivity ratios, so the development consumption of the first layer of photoresist 3 is much less than the developer consumption of the second layer of photoresist 4. A second bevel window with a smaller bevel angle than the first bevel window can be formed in the second exposure window 5.

[0046] Furthermore, since the temperature of the second post-bake is higher than that of the first post-bake, Figure 2e As shown, during the second post-bake, the second photoresist layer 4 flows, the first photoresist layer 3 and the second photoresist layer 4 merge into one layer, and a photolithography window with a bevel angle of a preset angle is formed at the second bevel window. The preset angle θ2 formed in this step is 45° to 80°. When the dielectric layer 2 is etched by the bevel photoresist mask 6 provided in this embodiment, an etching structure with a sidewall inclination angle of 45° to 80° can be formed.

[0047] In an achievable manner, the model of the second photoresist layer 4 is AZ4330, the thickness of the second photoresist layer 4 is 1-2um, the temperature of the second pre-bake is 100-110°C, the time of the second pre-bake is 1-2um, the energy of the second exposure is 110-130mJ, the length of the second exposure window formed by the second exposure is 1-2um, the developer of the second development is AZ300MIF, the time of the second development is 110-120s, the temperature of the second post-bake is 120-130°C, the time of the second post-bake is 90-120s, and the preset angle θ2 formed is 45°-80°. Furthermore, when the temperature of the second post-bake is 120-130°C, the preset angle θ2 formed is 45°.

[0048] The present embodiment provides a method for preparing a bevel photoresist mask suitable for semiconductor processes, and prepares a bevel photoresist with a smaller bevel angle by preparing two layers of photoresist and performing two photolithography. Since the first post-bake can make the first layer of photoresist have better resistance to the developer, the first layer of photoresist and the second layer of photoresist have different development selectivity ratios, thereby achieving the preparation of a bevel photoresist with a smaller bevel angle, thereby increasing the adjustment range of the side wall inclination angle of the dielectric layer to meet the angle requirements of the inclined side wall structure. The preparation method provided by the present embodiment only requires one photoresist to meet the requirements of achieving a larger bevel angle range in the yellow light process, avoiding the mixed use of photoresists with different photosensitivity and different viscosities, reducing the types and costs of consumables; avoiding the problems of multiple glue paths and multiple parameters in the glue leveling equipment to meet the mixed use of different photoresists, reducing equipment costs, and increasing the process window.

[0049] The above contents are further detailed descriptions of the present invention in combination with specific preferred embodiments, and it cannot be determined that the specific implementation of the present invention is limited to these descriptions. For ordinary technicians in the technical field to which the present invention belongs, several simple deductions or substitutions can be made without departing from the concept of the present invention, which should be regarded as falling within the protection scope of the present invention.

Claims

1. A method for preparing a bevel photoresist mask suitable for semiconductor technology, characterized in that: The following steps are involved: S1: forming the first layer of photoresist; S2: performing a first pre-bake, a first bevel patterning process and a first post-bake on the first layer of photoresist in sequence to obtain a first layer of photoresist with bevel patterning; S3: coating a second layer of photoresist on the first layer of photoresist with the bevel patterning; 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 bevel patterned first layer of photoresist.

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

3. The method for preparing a bevel photoresist mask suitable for semiconductor technology according to claim 2, characterized in that: Before step S1, the method further includes: A semiconductor wafer is obtained, and a dielectric layer is grown on the surface of the semiconductor wafer.

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

5. The method for preparing a bevel photoresist mask suitable for semiconductor technology according to claim 1, characterized in that: The first slope patterning process includes: a first exposure and a first development.

6. The method for preparing a bevel photoresist mask suitable for semiconductor technology according to claim 5, characterized in that: The second slope patterning process includes: a second exposure and a second development.

7. The method for preparing a bevel photoresist mask suitable for semiconductor technology according to claim 6, characterized in that: The energy of the second exposure is greater than the energy of the first exposure; 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.

8. The method for preparing a bevel photoresist mask suitable for semiconductor technology according to claim 1, characterized in that: The temperature of the second post-bake is higher than the temperature of the first post-bake.

9. The method for preparing a bevel photoresist mask suitable for semiconductor technology according to claim 1, characterized in that: The bevel angle of the bevel patterned first layer of photoresist is greater than 80°; the preset angle is 45° to 80°.

10. The method for preparing a bevel photoresist mask suitable for semiconductor technology according to claim 1, characterized in that: The first layer of photoresist and the second layer of photoresist are made of the same material.

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