Mask plate Cr pattern etching method with high selection ratio
By depositing SiO2 or Si3N4 hard masks on photoresist and Cr layers, and combining wet and dry etching techniques, the problems of insufficient selectivity and etching non-uniformity in the Cr pattern etching process of the mask were solved, achieving high selectivity and uniform Cr pattern etching.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-12-24
- Publication Date
- 2026-04-07
AI Technical Summary
During the etching of Cr patterns on a photomask, existing techniques struggle to achieve high selectivity, leading to uneven etching and incomplete Cr patterns. This is especially true when the feature size is below 40nm, where the photoresist's etching selectivity is insufficient, and the thickness limitation of the hard mask results in an etching load effect that affects the uniformity of the target layer pattern.
A reverse deposition hard mask method is adopted, which involves depositing a SiO2 or Si3N4 hard mask on a photoresist and a Cr layer. Using wet and dry etching techniques, the photoresist is removed first, then the Cr layer is etched, and finally the hard mask is removed, thus achieving a high selectivity etching process.
This effectively avoids etching unevenness, ensures the integrity and uniformity of the Cr pattern, and results in complete Cr pattern grooves, intact lines, and no incision at the top, thus improving the uniformity of etching.
Smart Images
Figure CN121806363A_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the technical field of photomask manufacturing, specifically relating to a high selectivity photomask Cr pattern etching method. Background Technology
[0002] During the etching of the Cr pattern on the mask, such as Figure 1 As shown, photoresist (PR) is typically chosen as the masking layer. Due to limitations in photolithography conditions, especially during the exposure of photomasks with feature sizes below 40nm, the thickness of the photoresist as a masking layer cannot be too high, otherwise it will lead to pattern collapse. However, the etching gas for Cr patterns in photomasks contains Cl2 and O2, among which O2 also has a significant etching effect on the photoresist. This results in an insufficient selectivity ratio between Cr and photoresist, making it difficult to completely etch the Cr pattern.
[0003] Currently, hard mask technology is being introduced into mask processing, using photoresist as the mask. First, the hard mask is etched, and then a Cr layer is etched based on the hard mask. For example, ... Figure 2 As shown, a SiO2 film layer is added to the existing Cr-PR film structure. During the etching process, photoresist is first used as a masking layer, and the SiO2 film layer is etched using an F-based gas. Then, the photoresist is removed, and the SiO2 film layer is used as a masking layer again to etch the Cr layer using O- and Cl-containing gases. Finally, the SiO2 layer is removed using an F-based gas. Unlike photoresist, SiO2 has high resistance to etching by both Cl2 and O2, thus significantly improving the selectivity during Cr etching and enabling the etching of small feature sizes. However, a drawback of this technique is that the hard mask cannot be too thick; otherwise, the etching load effect can easily cause uneven hard mask patterns, which in turn affects the unevenness of the target layer pattern. Secondly, in actual industrial production, optimized etching conditions are commonly used to improve the selectivity. For example, the article "Photomask plasma etching: A review" mentions using alternative gases and adding reducing agents. However, this method has poor stability and is difficult to apply in industrial production. Summary of the Invention
[0004] The purpose of this invention is to provide a high selectivity mask Cr pattern etching method to solve the above-mentioned problems.
[0005] This invention is mainly achieved through the following technical solutions: A high-selectivity mask pattern etching method includes the following steps: Step S1: Coat a photoresist layer on top of the Cr layer, and then expose it. During the pattern exposure process, use a reverse pattern to process the pattern onto the Cr layer to obtain the Cr pattern layer. Step S2: Deposit a hard mask on the etched photoresist layer and Cr pattern layer using physical deposition. Step S3: Use wet cleaning to remove the hard mask deposited on the photoresist layer; Step S4: Remove the photoresist layer exposed in step S3 using dry etching; Step S5: Using a hard mask as a masking layer, dry etching is used to etch the exposed Cr layer; Step S6: Remove the hard masking layer on the surface of the Cr pattern layer using dry etching.
[0006] To better realize the present invention, the hard mask is further described as a silicon dioxide layer or a Si3N4 layer.
[0007] To better realize the present invention, further, in step S2, the physical deposition process parameters are as follows: working pressure is 0.5 Pa, argon flow rate is 40 sccm, oxygen flow rate is 10 sccm, sputtering power is 500 W, substrate temperature is 100°C, and deposition rate is 5 nm / min.
[0008] To better realize the present invention, in step S3, a wet cleaning with 1wt%~5wt% HF solution is used, and the process parameters are: rotation speed of 400 rpm and flow rate of 400 ml / min.
[0009] To better realize the present invention, further, in step S4, the process parameters of dry etching are: working pressure of 15mT, argon flow rate of 10 sccm, power of 400 W, and substrate temperature of 20°C.
[0010] To better realize the present invention, further, in step S5, the process parameters of dry etching are: working pressure of 5mT, oxygen flow rate of 40 sccm, chlorine flow rate of 160 sccm, power of 500 W, bias power of 10W, and substrate temperature of 20°C.
[0011] To better realize the present invention, further, in step S6, the dry etching process parameters are as follows: working pressure is 15mT, CHF3 flow rate is 20 sccm, CF4 flow rate is 80 sccm, power is 500 W, bias power is 10W, and substrate temperature is 20°C.
[0012] The beneficial effects of this invention are as follows: This invention uses reverse deposition + etching in the processing of hard mask patterns, which can effectively avoid the etching inhomogeneity in the hard mask processing process, more completely preserve the photoresist pattern, further improve the uniformity of the target Cr layer, and the grooves of the Cr image of the etched mask are completely etched, the lines are complete, and there is no incision at the top. Attached Figure Description
[0013] Figure 1 A flowchart for traditional mask Cr pattern etching; Figure 2 A flowchart of a forward hard mask etching method for a Cr pattern as a template; Figure 3 This is a flowchart of the reverse hard mask etching method for the Cr pattern of the mask template in Example 1.
[0014] Figure 4 Electron micrograph of the Cr pattern of the mask template for conventional etching; Figure 5 Electron micrograph of the Cr pattern of the mask etched by forward hard mask etching; Figure 6 This is an electron microscope image of the Cr pattern etched in Example 1. Detailed Implementation
[0015] Example 1: A high selectivity mask Cr pattern etching method, such as Figure 3 As shown, it includes the following steps: Step 1: Coat a photoresist layer on top of the Cr layer, and then expose and develop it; during the pattern exposure process, use a reverse pattern to process the pattern onto the Cr layer.
[0016] Step 2: As shown in Table 1, a hard mask (such as SiO2, Si3N4, etc.) is deposited using physical deposition methods (including sputtering, evaporation, ion beam sputtering, etc.). Step 3: As shown in Table 2, use wet cleaning (1%~5% HF solution) to remove the hard mask on the photoresist; Step 4: As shown in Table 3, the exposed photoresist is removed using dry etching. Step 5: As shown in Table 4, a hard mask is used as a masking layer, and the target Cr layer is etched using dry etching; among which, O-containing and Cl-containing gases are used to etch the Cr layer. Step 6: As shown in Table 5, the hard masking layer on the surface is removed by dry etching, wherein the SiO2 layer is removed by F-based gas.
[0017] like Figure 4As shown, due to insufficient selectivity between photoresist and Cr etching, the patterned trenches were not thoroughly etched; the photoresist was exhausted, and the Cr lines were still not completely etched. Figure 5 As shown, due to the insufficient thickness of the top hard mask, the plasma etches laterally during the etching process, resulting in a noticeable inward cut at the top of the etched lines. Figure 6 As shown, the trenches are completely etched, the lines are intact, and there is no incision at the top. This invention uses a reverse deposition + etching method in the processing of hard mask patterns, which can effectively avoid etching inhomogeneities during hard mask processing, more completely preserve the photoresist pattern, and further improve the uniformity of the target layer.
[0018] Table 1 Hard Mask Deposition Process Parameters
[0019] Table 2 Hard Mask Removal Process Parameters
[0020] Table 3. Process parameters for removing photoresist
[0021] Table 4. Cr etching process parameters
[0022] Table 5 Process parameters for hard masking layer removal
[0023] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Any simple modifications or equivalent changes made to the above embodiments based on the technical essence of the present invention shall fall within the protection scope of the present invention.
Claims
1. A high-selectivity mask Cr pattern etching method, characterized in that, Includes the following steps: Step S1: Coat a photoresist layer on top of the Cr layer, and then expose it. During the pattern exposure process, use a reverse pattern to process the pattern onto the Cr layer to obtain the Cr pattern layer. Step S2: Deposit a hard mask on the etched photoresist layer and Cr pattern layer using physical deposition. Step S3: Use wet cleaning to remove the hard mask deposited on the photoresist layer; Step S4: Remove the photoresist layer exposed in step S3 using dry etching; Step S5: Using a hard mask as a masking layer, dry etching is used to etch the exposed Cr layer; Step S6: Remove the hard masking layer on the surface of the Cr pattern layer using dry etching.
2. The high selectivity mask Cr pattern etching method according to claim 1, characterized in that, The hard mask is a silicon dioxide layer or a Si3N4 layer.
3. A high selectivity mask Cr pattern etching method according to claim 1 or 2, characterized in that, In step S2, the physical deposition process parameters are as follows: working pressure is 0.5 Pa, argon flow rate is 40 sccm, oxygen flow rate is 10 sccm, sputtering power is 500 W, substrate temperature is 100°C, and deposition rate is 5 nm / min.
4. A high selectivity mask Cr pattern etching method according to claim 1 or 2, characterized in that, In step S3, a wet cleaning process using a 1wt%~5wt% HF solution is employed, with the following process parameters: rotation speed of 400 rpm and flow rate of 400 ml / min.
5. A high selectivity mask Cr pattern etching method according to claim 1 or 2, characterized in that, In step S4, the dry etching process parameters are: working pressure of 15 mT, argon flow rate of 10 sccm, power of 400 W, and substrate temperature of 20°C.
6. A high selectivity mask Cr pattern etching method according to claim 1 or 2, characterized in that, In step S5, the dry etching process parameters are as follows: working pressure is 5 mT, oxygen flow rate is 40 sccm, chlorine flow rate is 160 sccm, power is 500 W, bias power is 10 W, and substrate temperature is 20°C.
7. A high selectivity mask Cr pattern etching method according to claim 1 or 2, characterized in that, In step S6, the dry etching process parameters are as follows: working pressure is 15mT, CHF3 flow rate is 20 sccm, CF4 flow rate is 80 sccm, power is 500 W, bias power is 10W, and substrate temperature is 20°C.