High-selectivity etching solution for radio frequency chip material

Abstract

The application discloses a high-selectivity etching solution for radio frequency chip material, which comprises 15-20% of alkaline substance by mass content; 0.1-0.25% of oxidizing agent by mass content; 0.1-0.2% of corrosion inhibitor by mass content; 0.01-0.05% of stabilizer by mass content; and the rest is deionized water. The high-selectivity etching solution for radio frequency chip material can realize high-selectivity etching of scandium-doped aluminum nitride and tungsten in the chip material, can ensure complete etching of the scandium-doped aluminum nitride while avoiding etching of the tungsten to the maximum extent, and can greatly reduce the damage number of the tungsten layer caused by the etching solution by adding the stabilizer.

Description

Technical Field

[0001] This invention belongs to the field of electronic chemicals, and specifically relates to a highly selective etching solution for radio frequency chip materials. Background Technology

[0002] The development of modern military electronic equipment and civilian communication systems has placed demands on miniaturization, multifunctionality, and reconfigurability in radio frequency (RF) systems, leading to increasingly complex RF system functions. Currently, the various performance indicators of RF chips are constantly being optimized, with frequency coverage reaching the microwave and terahertz bands. 5G communication technology requires a large number of mid-to-high frequency devices, mainly including filters, power amplifiers, low-noise amplifiers, and RF switches. Compound semiconductor materials are the core materials for fabricating these devices. Scandium-doped aluminum nitride (ScAlN), as a piezoelectric film material, has significant advantages such as high sound velocity, good thermal stability, wide bandgap, and especially compatibility with CMOS processes. It can also overcome the shortcomings of aluminum nitride (AlN) piezoelectric films, such as low piezoelectric coefficient and low electromechanical coupling coefficient. The performance of ScAlN films largely determines the quality of RF chips. Furthermore, combining ScAlN with different metals to form RF chip materials will improve their performance to varying degrees. After combining with different film layers, further etching is required to obtain the specific patterns needed for the process. Summary of the Invention

[0003] The present invention aims to provide a highly selective etchant for radio frequency chip materials, which reduces the damage to the tungsten layer while maintaining a high selectivity ratio for etching scandium-doped aluminum nitride layers.

[0004] This invention relates to a highly selective etching solution for radio frequency chip materials. The etching solution comprises an alkaline substance, an oxidant, a corrosion inhibitor, a stabilizer, and deionized water. The alkaline substance has a mass content of 15%. 20%; oxidant content is 0.1% by mass. 0.25%; corrosion inhibitor content is 0.1%. 0.2%; stabilizer content is 0.01%. 0.05%; the remainder is deionized water.

[0005] In the etching solution of the present invention, the main alkaline substance is one or a combination of several of potassium hydroxide, sodium hydroxide, ammonia, tetramethylammonium hydroxide, and tetraethylammonium hydroxide.

[0006] In the etching solution of the present invention, the oxidant includes one or a combination of several of the following: ammonium persulfate, potassium persulfate, sodium hypochlorite, potassium iodide, and catechol.

[0007] The main function of the oxidant is to increase the etching rate of scandium-doped aluminum nitride, thereby improving the etching selectivity ratio between scandium-doped aluminum nitride and tungsten layers.

[0008] Adding oxidants to alkaline formulations can accelerate the etching rate of the ScAlN layer. However, when a certain amount of oxidant is present in the system, the etching rate of the tungsten layer also increases significantly, causing varying degrees of damage to the tungsten layer. Therefore, it is necessary to add corrosion inhibitors to reduce the etching rate of the etchant on the tungsten. On the other hand, the damage is closely related to the etching uniformity of the etchant. Good stabilizers can increase the etching uniformity of the system, thereby reducing the amount of damage to the tungsten layer.

[0009] In the etching solution of the present invention, the etching inhibitor includes one or a combination of several of the following: imidazole, 2-propylimidazolium, 2-undecylimidazolium, 3-mercapto-1,2,4-triazole, benzotriazole, methylbenzotriazole, 1,2,3-triazole, polyethyleneimine, quinoline-4-amine, and 4-quinoline methanol.

[0010] Tungsten corrosion inhibitors selectively bind to the surface of metallic tungsten, specifically reducing the etching rate of the tungsten layer and achieving high selectivity etching.

[0011] In the etching solution of the present invention, the stabilizer comprises one or a combination of several of the following: 4-(methylamino)butylcarbamate, 2-(methylamino)propylcarbamate, tert-butyl carbamate, 8-aminooctanoate, morpholine-3-methylcarbamate, (2-amino-tert-butyl)carbamate, trimethylsilyl valeramide, 5-tert-butyl-acetyl-2-one, 2-amino-δ-valeramide, and (S)-3-amino-2-caprolactam.

[0012] The advantages of this invention are as follows: Compared with the prior art, this invention provides a highly selective etching solution for radio frequency chip materials. The etching selectivity ratio of scandium-doped aluminum nitride to tungsten in the chip material can reach more than 900, and through structural surface analysis, the number of tungsten layer damages is significantly reduced.

[0013] (1) The etching solution of the present invention significantly improves the etching rate of scandium-doped aluminum nitride in the presence of an oxidant.

[0014] (2) The etching solution of the present invention achieves high selectivity etching of scandium-doped aluminum nitride and tungsten by adding corrosion inhibitors to the system. The selectivity can reach more than 900 and the tungsten etching rate is less than 10.7 Å / min.

[0015] (3) The stabilizer in the etching solution of the present invention prevents some of the etching solution from etching too quickly in the longitudinal direction, penetrating the scandium-doped aluminum nitride layer and reaching the tungsten layer to cause damage to the tungsten layer, with the damage rate being less than 1%. Attached Figure Description

[0016] Figure 1Ultra-depth-of-field microscope images of scandium-doped aluminum nitride and tungsten structure sheets etched in Comparative Example 1; Figure 2 For comparison, ultra-depth-of-field microscope images of etched scandium-doped aluminum nitride and tungsten structure sheets in Example 2; Figure 3 This is a super depth-of-field microscope image of the etched scandium-doped aluminum nitride and tungsten structure sheet in Example 3; Figure 4 This is a super depth-of-field microscope image of the etched scandium-doped aluminum nitride and tungsten structure sheet in Example 7. Detailed Implementation

[0017] The technical solutions of the present invention will be clearly and completely described below with reference to specific embodiments. These embodiments are merely some, not all, of the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the protection scope of the present invention.

[0018] Example 1 Example 1 involves adding 0.15% by mass of imidazole as a tungsten etching inhibitor and 0.01% by mass of tert-butyl 4-(methylamino)butylcarbamate as a stabilizer, as detailed below: The composition includes 20% potassium hydroxide, 0.2% ammonium persulfate, 0.15% imidazole, 0.01% tert-butyl 4-(methylamino)butylcarbamate, and the remainder is water.

[0019] The etching solution prepared according to the above proportions was used to etch scandium-doped aluminum nitride (ANU) wafers on a silicon substrate at 55°C (ANU wafers were cut into regular cubes of 2*2 cm). To avoid inaccurate measurements due to hydrolysis of ANU in air, the ANU wafers were first cleaned in a low-concentration alkaline solution (2% ammonia) for 10 seconds to remove the hydrolyzed oxide layer on the surface. The ANU wafers were then measured using an ellipsometer, and the initial thickness of the ANU was calculated through model fitting. The average value of four measurements was taken for each wafer. The ANU wafers were then immersed in the etching solution for 10 seconds, cleaned, and dried with nitrogen. The ANU spectrum was measured using an ellipsometer (keeping the test points consistent with those before etching). The thickness of the ANU was calculated by fitting and averaging the values. The etching rate of the ANU wafers could then be calculated. The etching rate of scandium aluminum nitride wafers prepared with the above ratio can reach 15.96 nm / s.

[0020] The etching solution prepared according to the above proportions was used to etch tungsten metal onto a silicon substrate at 55°C (the tungsten sheet was cut into regular cubes of 2*2 cm). To avoid inaccurate measurements due to oxidation of the tungsten sheet in the natural environment, the tungsten sheet was first cleaned in a low-concentration acid solution (2% HF) for 10 s to remove the oxide layer. Then, the resistance of the tungsten sheet was measured using a four-probe resistance meter, and the initial thickness was calculated. The average value of four measurements was taken for each sheet. The tungsten sheet was then immersed in the etching solution for 600 s, cleaned, and dried with nitrogen. The resistance of the tungsten sheet was measured again using a four-probe resistance meter (the measurement points remained consistent before and after etching) to obtain the tungsten sheet thickness. The etching rate of the tungsten sheet was calculated. The etching rate of the tungsten sheet using the etching solution prepared according to the above proportions reached 10.32 Å / min.

[0021] Simultaneously, a 2*2 cm scandium-doped aluminum nitride and tungsten structural sheet was etched using 50 g of etching solution. The number of damages in the tungsten layer was detected, and the number of damages was statistically analyzed using a super depth-of-field microscope. In this embodiment, the number of etching damages was 4 / 607, accounting for less than 1% of the tungsten layer damage.

[0022] Therefore, the above formulation has an etching selectivity of 927.91 for scandium-doped aluminum nitride and metallic tungsten, an etching damage number of 4 / 607, and a damage rate of less than 1% to the tungsten layer.

[0023] The etching rate, number of damages, and damage percentage of subsequent embodiments and comparative examples are shown in Table 1.

[0024] Example 2 Example 2 involves adding 0.15% by mass of imidazole as a tungsten etching inhibitor and 0.01% by mass of tert-butyl 4-(methylamino)butylcarbamate as a stabilizer, as detailed below: The composition includes 20% potassium hydroxide, 0.2% ammonium persulfate, 0.15% imidazole, 0.01% tert-butyl 4-(methylamino)butylcarbamate, and the remainder is water.

[0025] Example 3 Example 3 involves adding 0.15% by mass of 2-propylimidazolium as a tungsten etching inhibitor and 0.01% by mass of tert-butyl 4-(methylamino)butylcarbamate as a stabilizer, as detailed below: The composition includes 20% potassium hydroxide, 0.2% ammonium persulfate, 0.15% 2-propylimidazolium, 0.01% tert-butyl 4-(methylamino)butylcarbamate, and the remainder is water.

[0026] Example 4 Example 4 involves adding 0.15% by mass of 1,2,3-triazole as a tungsten etching inhibitor and 0.01% by mass of tert-butyl 4-(methylamino)butylcarbamate as a stabilizer, as detailed below: The composition includes 20% potassium hydroxide, 0.2% ammonium persulfate, 0.15% 1,2,3-triazole, 0.01% tert-butyl 4-(methylamino)butylcarbamate, and the remainder is water.

[0027] Example 5 Example 5 involves adding 0.15% benzotriazole as a tungsten etching inhibitor and 0.01% tert-butyl 4-(methylamino)butylcarbamate as a stabilizer, as detailed below: The composition includes 20% potassium hydroxide, 0.2% ammonium persulfate, 0.15% benzotriazole, 0.01% tert-butyl 4-(methylamino)butylcarbamate, and the remainder is water.

[0028] Example 6 Example 6 involves adding 0.15% by mass of quinoline-4-amine as a tungsten etching inhibitor and 0.01% by mass of tert-butyl 4-(methylamino)butylcarbamate as a stabilizer, as detailed below: The composition includes 20% potassium hydroxide, 0.2% ammonium persulfate, 0.15% quinoline-4-amine, 0.01% tert-butyl 4-(methylamino)butylcarbamate, and the remainder is water.

[0029] Example 7 Example 7 involves adding 0.15% polyethyleneimine as a tungsten etching inhibitor and 0.01% tert-butyl 4-(methylamino)butylcarbamate as a stabilizer, as detailed below: The composition includes 20% potassium hydroxide, 0.2% ammonium persulfate, 0.15% polyethyleneimine, 0.01% tert-butyl 4-(methylamino)butylcarbamate, and the remainder is water.

[0030] Example 8 Example 8 involves adding 0.15% by mass of 2-propylimidazolium as a tungsten etching inhibitor and 0.01% by mass of tert-butyl carbamate as a stabilizer, as detailed below: The composition includes 20% potassium hydroxide, 0.2% ammonium persulfate, 0.15% 2-propylimidazolium, 0.01% tert-butyl carbamate, and the remainder is water.

[0031] Example 9 Example 9 involves adding 0.15% by mass of 2-propylimidazolium as a tungsten etching inhibitor and 0.01% by mass of tert-butyl carbamate as a stabilizer, as detailed below: The composition includes 20% potassium hydroxide, 0.2% ammonium persulfate, 0.15% 2-propylimidazolium, 0.01% tert-butyl (2-amino-tert-butyl)carbamate, and the remainder is water.

[0032] Example 10 Example 10 involves adding 0.15% by mass of 2-propylimidazolium as a tungsten etching inhibitor and 0.01% by mass of trimethylsilyl valerolamide as a stabilizer, as detailed below: The composition includes 20% potassium hydroxide, 0.2% ammonium persulfate, 0.15% 2-propylimidazolium, 0.01% trimethylsilyl valerate, and the remainder is water.

[0033] Example 11 Example 11 involves adding 0.15% by mass of 2-propylimidazolium as a tungsten etching inhibitor and 0.01% by mass of 5-tert-butylacetylheptane-2-one as a stabilizer, as detailed below: The composition includes 20% potassium hydroxide, 0.2% ammonium persulfate, 0.15% 2-propylimidazolium, 0.01% 5-tert-butylacetyl-2-one, and the remainder is water.

[0034] Example 12 Example 12 involves adding 0.15% by mass of 2-propylimidazolium as a tungsten etching inhibitor and 0.01% by mass of (S)-3-amino-2-caprolactam as a stabilizer, as detailed below: The composition includes 20% potassium hydroxide, 0.2% ammonium persulfate, 0.15% 2-propylimidazolium, 0.01% (S)-3-amino-2-caprolactam, and the remainder is water.

[0035] Comparative Example 1 Based on Example 1, the difference is that Comparative Example 1 is an etching solution without the addition of tungsten etching inhibitors and stabilizers, as detailed below: The potassium hydroxide content is 20%, the ammonium persulfate content is 0.2%, and the remainder is deionized water.

[0036] Comparative Example 2 Based on Example 1, the difference is that Comparative Example 2 did not contain a stabilizer, as detailed below: The composition is as follows: potassium hydroxide content is 20%, ammonium persulfate content is 0.2%, imidazole content is 0.15%, and the remainder is water.

[0037] Comparative Example 3 Based on Example 1, the difference is that Comparative Example 3 did not add a corrosion inhibitor, as detailed below: The composition of the mixture is as follows: potassium hydroxide (20%), ammonium persulfate (0.2%), tert-butyl 4-(methylamino)butylcarbamate (0.01%), and the remainder is deionized water. Comparative Example 4 Based on Example 1, the difference is that Comparative Example 4 added other types of corrosion inhibitors, as detailed below: The composition of the mixture is as follows: potassium hydroxide 20%, ammonium persulfate 0.2%, ethylenediaminetetramethylenephosphonic acid 0.15%, tert-butyl 4-(methylamino)butylcarbamate 0.01%, and the remainder is deionized water. Comparing the data in Table 1 with Comparative Example 1 and Comparative Example 2, it is evident that the corrosion inhibitor has a significant corrosion inhibition effect on the tungsten layer, reducing the tungsten etching rate from 375 Å / min to 9.53 Å / min. Figure 2 and Figure 3 It can be observed that the number of tungsten layer damages is significantly reduced after the addition of stabilizers. The experimental results of Example 1 and Comparative Example 3 show that adding stabilizers alone neither improves the selectivity nor reduces the number of tungsten layer damages. The experimental results of Comparative Example 4 show that combining other types of corrosion inhibitors (phosphonic acids) with stabilizers does not reduce the number of tungsten layer damages. Comparing Examples 1-6 reveals that corrosion inhibitors with different structures have varying effects on tungsten layer corrosion inhibition, but the combined effect of stabilizers and corrosion inhibitors significantly reduces the number of tungsten layer damages. Under the same conditions, Example 3 exhibits the best tungsten layer corrosion inhibition effect, achieving a selectivity of 1346.48 and a damage count of 5 / 612, representing a damage percentage of 0.82%, which is a significant improvement compared to Comparative Examples 1-4. Examples 7-12 mainly compared the improvement effects of different stabilizers on the number of tungsten layer damages. Example 7 achieved both high selective etching of scandium-doped aluminum nitride and tungsten (selectivity ratio greater than 1303) and protection of the tungsten layer, reducing the number of tungsten layer damages to 2 / 623, with a damage ratio of 0.32%.

[0038] Table 1. Data and selection ratios from etching experiments conducted in the examples and comparative examples.

[0039] The technical solutions of the present invention have been explained through the above embodiments, but the present invention is not limited to the above embodiments, that is, it does not mean that the present invention must rely on the above specific embodiments to be implemented. Any improvements made by those skilled in the art based on the present invention, or equivalent substitutions for the materials selected in the present invention, fall within the scope of patent protection.

Claims

1. A highly selective etching solution for radio frequency chip materials, characterized in that: The highly selective etching solution for the radio frequency chip material comprises the following raw material components: 15 Alkaline substances with a mass content of 20%; 0.1 Oxidizing agent with a mass content of 0.25%; 0.1 0.2% by mass corrosion inhibitor; 0.01 Stabilizer content: 0.05% by mass; The remainder is deionized water; Stabilizers include one or a combination of several of the following: 4-(methylamino)butylcarbamate, 2-(methylamino)propylcarbamate, tert-butyl carbamate, 8-aminooctanoate, morpholine-3-methylcarbamate, (2-amino-tert-butyl)carbamate, trimethylsilyl valeramide, 5-tert-butyl-acetyl-2-one, 2-amino-δ-valeramide, and (S)-3-amino-2-caprolactam. Alkaline substances include one or more of the main alkaline substances such as potassium hydroxide, sodium hydroxide, ammonia, tetramethylammonium hydroxide, and tetraethylammonium hydroxide; Oxidizing agents include one or a combination of several of the following: ammonium persulfate, potassium persulfate, sodium hypochlorite, potassium iodide, and catechol; Corrosion inhibitors include one or a combination of several of the following: imidazole, 2-propylimidazolium, 2-undecylimidazolium, 3-mercapto-1,2,4-triazole, benzotriazole, methylbenzotriazole, 1,2,3-triazole, polyethyleneimine, quinoline-4-amine, and 4-quinoline methanol.

2. The highly selective etching solution for radio frequency chip materials according to claim 1, characterized in that: The etching selectivity ratio of scandium-doped aluminum nitride and metallic tungsten in the chip material is greater than 900, the tungsten etching rate is less than 10.7 Å / min, there is no residual scandium-doped aluminum nitride, and the tungsten layer damage rate is less than 1%.

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