CN113991009A

CN113991009A - High-selectivity scandium-doped aluminum nitride wet etching process method

Info

Publication number: CN113991009A
Application number: CN202111116133.1A
Authority: CN
Inventors: 李�杰; 姜理利; 王雷; 陈聪; 黄旼; 郁元卫
Original assignee: CETC 55 Research Institute
Current assignee: CETC 55 Research Institute
Priority date: 2021-09-23
Filing date: 2021-09-23
Publication date: 2022-01-28

Abstract

The invention relates to a wet etching process method of high-selectivity scandium-doped aluminum nitride. 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 multilayer composite film structure; (2) etching the dielectric layer by adopting a wet process to realize the graphical masking of the piezoelectric layer; (3) corroding the AlScN piezoelectric layer by using a wet etching solution to obtain a residual etching surface containing scandium groups; (4) and (3) correcting the surface state of the etched AlScN by adopting a wet microetching process to obtain the etching morphology meeting the requirement. The invention provides a process method for wet etching AlScN, which can effectively reduce the serious side etching phenomenon and the residue problem of scandium-containing groups in the prior art; the characteristic of high selectivity of wet etching on materials is utilized, so that the phenomenon of over-etching on the lower-layer materials by the existing dry etching AlScN process is avoided; meanwhile, the process method can effectively reduce the process cost and improve the productivity and efficiency.

Description

High-selectivity scandium-doped aluminum nitride wet etching process method

Technical Field

The invention discloses a high-selectivity scandium-doped aluminum nitride wet etching process method, and belongs to the technical field of semiconductor manufacturing.

Background

The AlScN serving as a piezoelectric material has the characteristics of high sound velocity, high temperature resistance, stable performance, high piezoelectric coefficient, compatibility with an MEMS (micro-electromechanical systems) process and the like. AlScN has been applied to the manufacture of MEMS and NEMS devices in the fields of 5G filters, sensors, resonators, energy collectors and the like, and has a certain market share.

However, due to the film forming property (crystalline phase deposition) of the material, a physical etching method with poor selectivity and high price is often adopted for the process in the process of process patterning, so that the overall performance of the device cannot be guaranteed due to the fact that the bottom layer metal or other materials are over-etched; the conventionally adopted wet etching process method also has the problems of serious side etching and scandium-containing group residue.

In view of the above, there is a need to find a process method with simple control, low cost and strong selectivity, so as to solve the above technical problems.

Disclosure of Invention

The invention provides a high-selectivity AlScN wet etching process method, which aims to solve the technical problems in the background technology.

The technical solution of the invention is as follows: a wet etching process method of high-selectivity scandium-doped aluminum nitride is characterized by comprising the following steps:

(1) preparing a substrate wafer, and sequentially depositing a seed layer 2, a scandium-doped aluminum nitride piezoelectric layer 3 and a dielectric layer 4 on a substrate 1 to form a multilayer composite film structure;

(2) etching the dielectric layer 4 by adopting a wet process to realize the graphical masking of the scandium-doped aluminum nitride piezoelectric layer 3;

(3) corroding the scandium-doped aluminum nitride piezoelectric layer 3 by using a wet-process corrosion solution to obtain a residual etching surface containing scandium groups;

(4) and correcting the surface state of the scandium-doped aluminum nitride after etching by adopting a wet microetching process to obtain the etching morphology meeting the requirement.

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

In the step (2), the liquid medicine used in the wet process is BOE liquid medicine.

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

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

Compared with the prior art, the invention has the following remarkable advantages:

1. the invention provides a high-selectivity AlScN wet etching process method, which is different from the traditional etching process in that the wet etching process is adopted in the whole etching process, so that a single multi-chip process can be carried out, while the dry etching process is adopted in the traditional A1ScN process, so that only a single-chip process can be adopted, and the method is characterized in that the cost is reduced, and the working efficiency is improved;

2. the etching method adopted by the invention is a high-selectivity process method, has material pertinence, and can avoid over-etching and damage of the AlScN lower-layer material, and the traditional dry etching process usually belongs to a process over-etching state, so that the lower-layer material is damaged, and the performance of the whole device is deviated;

3. the etching method adopted by the invention is a high-selectivity process method, and the side etching inhibitor is added into the liquid medicine, so that the defect of the side etching process of wet etching is greatly avoided, the etching damage of the A1ScN side is reduced, and the performance of the device is ensured;

4. the invention adds a wet compensation process method, solves the problem of residue of scandium-containing genes in the existing wet process corrosion (the problem is the main reason that A1ScN is not selected in the traditional wet etching process), and is beneficial to improving the performance of the device.

Drawings

FIG. 1 is a flow chart of a high-selectivity AlScN wet etching process method.

Figure 2 is a side view of the layered structure after etching.

Fig. 3 is a graph showing the etching results of example 3.

In the figure, 1 is a substrate material, 2 is a seed layer, 3 is an AlScN layer, and 4 is a dielectric layer.

Detailed Description

The technical scheme of the invention is further explained by combining the attached drawings

As shown in fig. 1-2, a high selectivity AlScN wet etching process method comprises the following steps:

step 1, providing a silicon substrate material 1, and depositing or growing a seed layer 2, an AlScN layer 3 and a dielectric layer 4 on the substrate in sequence;

step 2, etching the dielectric layer by wet etching through protecting the photoetching patterned mask to form a required pattern;

step 3, taking the etched dielectric layer as an AlScN protective layer, and etching the AlScN by adopting a wet etching method to form the required shape and size;

and 4, because the influence of the internal atomic reaction degree is different, the etched AlScN needs to be further processed by adopting wet chemical liquid after etching, and the completely etched shape of the etched area is obtained.

The present invention will be described in further detail with reference to examples.

A high-selectivity AlScN wet etching process method comprises the following steps:

example 1

Step 1, providing a silicon substrate material 1, wherein the silicon substrate material is (100) type silicon, and depositing a 30nm titanium (Ti) seed layer, a 600nm AlScN layer (containing 8% of Sc) and a 300nm silicon dioxide (SiO) on the substrate in sequence₂) A dielectric layer;

step 2, etching the dielectric layer by adopting BOE mixed liquor with the concentration of 3:1 for 3min through protecting the photoetching patterned mask to form a required mask pattern;

step 3, etching the SiO₂As an AlScN protective layer, adopting 32% KOH (containing 0.25% of alcohol additives) with the temperature of 35 ℃ to etch AlScN for 30s to form the required shape and size;

and 4, retreating the etched AlScN by adopting a mixed solution of 1:6 dilute hydrochloric acid (hydrochloric acid: water) and 0.2% complexing agent for 20s, and removing the residue containing scandium groups on the surface to form a final complete etching form.

Example 2

Step 1, providing a silicon substrate material 1, wherein the silicon substrate material is (100) type silicon, and depositing a 40nm molybdenum (Mo) seed layer, a 500nm AlScN layer (containing 8% of Sc) and 500nm silicon dioxide (SiO) on the substrate in sequence₂) A dielectric layer;

step 2, etching the dielectric layer by adopting BOE mixed liquor with the concentration of 5:1 for 4min through protecting the photoetching patterned mask to form a required mask pattern;

step 3, etching the SiO₂As an AlScN protective layer, adopting 25% KOH (containing 0.45% of alcohol additives) with the temperature of 30 ℃ to etch AlScN, and corroding for 1min to 20s to form the required shape and size;

Example 3

Step 1, providing a silicon substrate material 1, wherein the silicon substrate material is (100) type silicon, and depositing a molybdenum (Mo) seed layer of 30nm, an AlScN layer of 600nm (containing 8% of Sc) and silicon dioxide (Si) of 600nm on the substrate in sequence₃N₄) A dielectric layer;

step 2, etching the dielectric layer by adopting BOE mixed liquor with the concentration of 4:1 for 2min through protecting the photoetching patterned mask to form a required mask pattern;

step 3, etching the SiO₂As the AlScN protective layer, the concentration of30 percent of KOH (containing 0.45 percent of alcohol additive) at 80 ℃ is used for etching the AlScN for 20s to form the required shape and size

And 4, retreating the etched AlScN by adopting a mixed solution of 1:3 dilute nitric acid (nitric acid: water) and 0.3% complexing agent for 20s, and removing the residue of scandium-containing groups on the surface to form a final complete etching shape, which is shown in figure 3.

Claims

1. A wet etching process method of high-selectivity scandium-doped aluminum nitride is characterized by comprising the following steps:

(1) preparing a substrate wafer, and sequentially depositing a seed layer (2), a scandium-doped aluminum nitride piezoelectric layer (3) and a dielectric layer (4) on a substrate (1) to form a multilayer composite film structure;

(2) etching the dielectric layer (4) by adopting a wet process to realize the graphical masking of the scandium-doped aluminum nitride piezoelectric layer (3);

(3) corroding the scandium-doped aluminum nitride piezoelectric layer (3) by using a wet-process corrosion solution to obtain a residual etching surface containing scandium groups;

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

3. The method according to claim 1, wherein the dielectric layer in step (1) is SiO₂And the thickness is 200nm-800 nm.

4. The method as claimed in claim 1, wherein in step (2), the chemical solution used in the wet etching process is BOE chemical solution.

5. The method as claimed in claim 1, wherein in step (3), the wet etching solution is NaOH or KOH, and an alcohol buffer is added.

6. The method as claimed in claim 5, wherein the NaOH or KOH content is 1-35 wt%, the temperature is 30-80 ℃, and the alcohol buffer content is 0.1-0.5 wt%.

7. The method as claimed in claim 1, wherein in step (4), the etchant used in the wet microetching process is a miscible solution of one of nitric acid, hydrochloric acid, and sulfuric acid and a complexing agent.

8. The process of claim 7, wherein the ratio of nitric acid, hydrochloric acid or sulfuric acid: the water volume ratio is bright 1:4-1:20, and the content of the complexing agent is 0.1-0.8 wt%.