A high-selectivity wet etching process for scandium-doped aluminum nitride

Abstract

The present invention relates to a high-selectivity wet etching process method for scandium-doped aluminum nitride. It includes: (1) preparing a substrate wafer, and sequentially depositing a seed layer, a scandium-doped aluminum nitride piezoelectric layer, and a dielectric layer on the substrate to form a multi-layer composite film structure; (2) using a wet process to etch the dielectric layer to achieve patterning and masking of the piezoelectric layer; (3) using a wet etching solution to etch the AlScN piezoelectric layer to obtain a residual etched surface containing scandium groups; (4) adopting a wet micro-etching process to correct the surface state of the etched AlScN to obtain an etched morphology that meets the requirements. The present invention provides a process method for wet etching AlScN, which can effectively reduce the serious side etching phenomenon and the residual problem of scandium groups in the existing process; by utilizing the high selectivity of the wet etching for materials, it avoids the over-etching phenomenon of the underlying materials in the existing dry etching process of AlScN; at the same time, this process method can effectively reduce the process cost, improve the production capacity and efficiency.

Description

Technical Field

[0001] The invention discloses a high-selectivity scandium-doped aluminum nitride wet etching process method, belonging to the technical field of semiconductor manufacturing. Background Art

[0002] AlScN, a piezoelectric material, boasts high acoustic velocity, high temperature resistance, stable performance, a high piezoelectric coefficient, and compatibility with MEMS processes. AlScN has been applied to the manufacture of MEMS and NEMS devices in areas such as 5G filters, sensors, resonators, and energy harvesters, and has secured a significant market share.

[0003] However, due to the film-forming properties of the material itself (crystalline phase deposition), the process patterning often requires the use of less selective and expensive physical etching methods, which leads to over-etching of the underlying metal or other materials, making it impossible to guarantee the overall performance of the device; and the conventional wet etching process method also has the problems of severe side etching and residual scandium-containing groups.

[0004] In view of this, it is necessary to seek a process method with simple control, low cost and strong selectivity to solve the above technical problems. Summary of the Invention

[0005] The present invention proposes a highly selective AlScN wet etching process method, which aims to solve the technical problems existing in the above-mentioned background technology.

[0006] The technical solution of the present invention is a highly selective scandium-doped aluminum nitride wet etching process, which is characterized by comprising the following steps:

[0007] (1) Prepare a substrate wafer, and sequentially deposit a seed layer 2, a scandium-doped aluminum nitride piezoelectric layer 3, and a dielectric layer 4 on the substrate 1 to form a multilayer composite film structure;

[0008] (2) etching the dielectric layer 4 using a wet process to achieve patterned masking of the scandium-doped aluminum nitride piezoelectric layer 3;

[0009] (3) etching the scandium-doped aluminum nitride piezoelectric layer 3 using a wet etching solution to obtain a residual etched surface containing scandium groups;

[0010] (4) Use wet process solution to modify the surface state of scandium-doped aluminum nitride after etching to obtain the etching morphology that meets the requirements.

[0011] The seed layer structure in step (1) is one of metals Mo, Pt, and Ti, and the seed layer thickness is 30nm-500nm; the dielectric layer is SiO2, and the thickness is 200nm-800nm.

[0012] In the step (2), the chemical solution used in the wet process is BOE solution.

[0013] In the step (3), the wet etching solution is NaOH or KOH, and an alcohol buffer is added; the content of the NaOH or KOH is 1-35 wt%, the temperature is 30-80 °C, and the content of the alcohol buffer is 0.1-0.5 wt%.

[0014] In the step (4), the etching solution used in the wet micro-etching process is a mutual solution of one of nitric acid, hydrochloric acid, and sulfuric acid and a complexing agent; the volume ratio of the acid (nitric acid, hydrochloric acid, or sulfuric acid) to water is 1:4 - 1:20, and the content of the complexing agent is 0.1-0.8 wt%.

[0015] Compared with the prior art, the remarkable advantages of the present invention are as follows:

[0016] 1. The present invention provides a high-selectivity wet etching process method for AlScN. Different from the traditional etching process, the whole process of the etching process adopts a wet etching process, and a single multi-wafer process can be carried out, while the traditional A1ScN process adopts a dry etching process and can only be a single-wafer process. Its characteristics are that the cost is reduced and the working efficiency is improved;

[0017] 2. The etching method adopted by the present invention is a high-selectivity process method, which has material pertinence and can avoid over-etching and damage to the underlying material of AlScN. However, the traditional dry etching process often belongs to the state of over-etching in the process, resulting in damage to the underlying material and further causing performance deviation of the overall device;

[0018] 3. The etching method adopted by the present invention is a high-selectivity process method. A side etching inhibitor is added to the chemical solution, which greatly avoids the disadvantages of the side etching process in wet etching, reduces the side etching damage of A1ScN, and ensures the device performance;

[0019] 4. The present invention adds a wet compensation process method, which solves the problem of residue of scandium-containing genes in the existing wet process corrosion (the existence of this problem is the main reason why traditional wet etching of A1ScN is not selected), and helps to improve the device performance. Description of the Drawings

[0020] Attached Figure 1 is a flow chart of the high-selectivity wet etching process method for AlScN.

[0021] Attached Figure 2 is a side view of the layered structure after etching.

[0022] Attached Figure 3 is a schematic diagram of the etching result of Example 3.

[0023] In the figure, 1 is the substrate material, 2 is the seed layer, 3 is the AlScN layer, and 4 is the dielectric layer. Detailed implementation mode

[0024] The technical solution of the present invention will be further described below with reference to the accompanying drawings.

[0025] As shown in the attached Figure 1-2 figure, a high-selectivity AlScN wet etching process method includes the following steps:

[0026] Step 1, provide a silicon substrate material 1, and sequentially deposit or grow a seed layer 2, a scandium-doped aluminum nitride piezoelectric layer 3, and a dielectric layer 4 on the substrate;

[0027] Step 2, through the protection of the lithographic patterning mask, use wet etching to etch the dielectric layer to form the required pattern;

[0028] Step 3, use the etched dielectric layer as a protective layer for the scandium-doped aluminum nitride piezoelectric layer, and use the wet etching method to etch the scandium-doped aluminum nitride piezoelectric layer to form the required morphological size;

[0029] Step 4, due to the different degrees of influence of its internal atomic reaction, the etched scandium-doped aluminum nitride piezoelectric layer needs to be further processed with a wet chemical solution after etching to obtain a fully etched morphology in the etched area.

[0030] The present invention will be further described in detail below with reference to the embodiments.

[0031] A high-selectivity AlScN wet etching process method includes the following steps: Embodiment

[0032] Step 1, provide a silicon substrate material 1, the silicon substrate material is (100)-type silicon, and sequentially deposit a 30-nm titanium (Ti) seed layer, a 600-nm AlScN layer (with a Sc content of 8%), and a 300-nm silicon dioxide (SiO2) dielectric layer on the substrate;

[0033] Step 2, through the protection of the lithographic patterning mask, use a 3:1 concentration BOE mixture to etch the dielectric layer, with an etching time of 3 minutes, to form the required mask pattern;

[0034] Step 3, use the etched SiO2 as an AlScN protective layer, and use 32% 35°C KOH (with an alcohol additive content of 0.25%) to etch AlScN, with an etching time of 30 seconds, to form the required morphological size;

[0035] Step 4, the etched AlScN is reprocessed with a mixed solution of 1:6 dilute hydrochloric acid (hydrochloric acid: water) and 0.2% complexing agent for 20 s to remove the residue of surface scandium-containing groups, forming the final completely etched morphology. Example

[0036] Step 1, provide a silicon substrate material 1, which is (100)-type silicon. A 40-nm molybdenum (Mo) seed layer, a 500-nm AlScN layer (with 8% Sc content), and a 500-nm silicon dioxide (SiO2) dielectric layer are sequentially deposited on the substrate.

[0037] Step 2, through the protection of a photolithographically patterned mask, the dielectric layer is etched with a 5:1 concentration of BOE mixed solution for 4 min to form the required mask pattern.

[0038] Step 3, using the etched SiO2 as the AlScN protection layer, AlScN is etched with 25% 30 °C KOH (with 0.45% alcohol additive content) for 1 min 20 s to form the required morphology size.

[0039] Step 4, the etched AlScN is reprocessed with a mixed solution of 1:6 dilute hydrochloric acid (hydrochloric acid: water) and 0.2% complexing agent for 20 s to remove the residue of surface scandium-containing groups, forming the final completely etched morphology. Example

[0040] Step 1, provide a silicon substrate material 1, which is (100)-type silicon. A 30-nm molybdenum (Mo) seed layer, a 600-nm AlScN layer (with 8% Sc content), and a 600-nm silicon dioxide (SiO2) dielectric layer are sequentially deposited on the substrate.

[0041] Step 2, through the protection of a photolithographically patterned mask, the dielectric layer is etched with a 4:1 concentration of BOE mixed solution for 2 min to form the required mask pattern.

[0042] Step 3, using the etched SiO2 as the AlScN protection layer, AlScN is etched with 30% 80 °C KOH (with 0.45% alcohol additive content) for 20 s to form the required morphology size. 7]

[0043] Step 4, the etched AlScN is reprocessed with a mixed solution of 1:3 dilute nitric acid (nitric acid: water) and 0.3% complexing agent for 20 s to remove the residue of surface scandium-containing groups, forming the final completely etched morphology, see Figure 3 .

Claims

1. A high-selectivity wet etching process method for scandium-doped aluminum nitride, characterized in that It includes the following steps: S1. Prepare a substrate wafer, and sequentially deposit a seed layer (2), a scandium-doped aluminum nitride piezoelectric layer (3), and a dielectric layer (4) on the substrate (1) to form a multi-layer composite film structure; S2. Use a wet process to etch the dielectric layer (4) to achieve patterning masking of the scandium-doped aluminum nitride piezoelectric layer (3); S3. Use a wet etching solution to etch the scandium-doped aluminum nitride piezoelectric layer (3) to obtain a residual etched surface containing scandium groups; S4. Use a wet chemical solution to correct the surface state of the etched scandium-doped aluminum nitride piezoelectric layer (3) to obtain an etched morphology that meets the requirements; In the step S2, the chemical solution used in the wet process is BOE solution; In the step S3, the wet etching solution is NaOH or KOH, with an alcohol buffer added; In the step S4, the etching solution used in the wet chemical solution is a mutual solution of one of nitric acid, hydrochloric acid, and sulfuric acid and a complexing agent.

2. The high-selectivity scandium-doped aluminum nitride wet etching process method according to claim 1, characterized in that The seed layer structure in the step S1 is one of metals Mo, Pt, and Ti, and the thickness of the seed layer is 30 nm - 500 nm.

3. The high-selectivity scandium-doped aluminum nitride wet etching process method according to claim 1, characterized in that The dielectric layer in the step S1 is SiO2, and the thickness is 200 nm - 800 nm.

4. The high-selectivity scandium-doped aluminum nitride wet etching process method according to claim 1, characterized in that The content of the NaOH or KOH is 1 - 35 wt%, the temperature is 30 - 80 °C, and the content of the alcohol buffer is 0.1 - 0.5 wt%.

5. The high-selectivity scandium-doped aluminum nitride wet etching process method according to claim 4, characterized in that The volume ratio of the acid (nitric acid, hydrochloric acid, or sulfuric acid) to water is 1:4 - 1:20, and the content of the complexing agent is 0.1 - 0.8 wt%.

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