Al etching solution capable of removing Si residues

Abstract

The invention discloses an Al etching solution capable of removing Si residues, which is mainly applied to the processes of etching AlSi and AlSiCu metal connecting lines in the semiconductor production process and etching away Al, can also remove the Si residues generated in the etching process without damaging SiO2 of a substrate layer, and comprises 35-65% of phosphoric acid, 5-10% of sodium hydroxide, 5-10% of sodium hydroxide, 5-10% of sodium hydroxide, 5-10% of sodium hydroxide and the balance of water. 0.1%-10% of nitric acid; 5%-30% of a pH buffer agent; 0.01%-3% of a fluorine-containing additive and the balance of water. According to the method, the etching rate of the SiO2 on the substrate can be controlled, and the SiO2 on the bottom layer cannot be excessively etched.

Description

Technical Field

[0001] This invention belongs to the field of chemical multi-component mixed acid component detection technology, specifically relating to an Al etching solution that can remove Si residue. Background Technology

[0002] In integrated circuit manufacturing processes, aluminum-silicon (AlSi) or aluminum-silicon-copper (AlSiCu) alloys are commonly used for metal interconnect layers, with the silicon content typically controlled between 0.5% and 1%. This ratio effectively suppresses interdiffusion between aluminum and silicon substrates, preventing structural damage to the semiconductor junction region caused by the aluminum-silicon alloying reaction. However, this material system can introduce specific process defects during patterning. For example, when forming metal wires using dry etching (plasma etching) or wet etching (chemical solution etching), the silicon content in the etched area is difficult to completely remove, ultimately resulting in residual Si slag. These residual silicon slags appear as dot-like black defects on the wafer surface. Although they do not change core electrical parameters such as the current-voltage characteristics of the device, they are considered significant process anomalies due to their substantial impact on product appearance quality.

[0003] Commonly used Al etching solutions typically consist of phosphoric acid, nitric acid, and acetic acid (PNA), as described in patent CN 119592954 A. While these solutions can etch away metallic Al lines, they generate the aforementioned Si slag, causing process abnormalities. Patents JP6813548B2, JP2020013991A, CN111019659A, and CN102597162A, among others, use inorganic acids such as nitric acid, acetic acid, hydrochloric acid, and nitrous acid combined with hydrofluoric acid to effectively etch away the Si coating. However, these solutions cannot control the etching of Al and can severely etch away the SiO2 substrate. Currently, no existing patents clearly define an Al etching solution that can simultaneously etch away Al lines, remove residual Si slag, and prevent damage to the SiO2 substrate. Summary of the Invention

[0004] To solve the above-mentioned technical problems, the present invention adopts the following technical solution: An Al etching solution capable of removing Si residue, comprising, by weight: 35%-65% phosphoric acid; 0.1%-10% nitric acid; 5%-30% pH buffer; 0.01%-3% fluorine-containing additive; and the remainder being water.

[0005] Furthermore, it also includes 0.1%-5% of an etching rate modifier, wherein the etching rate modifier is an aminoorganosiloxane.

[0006] Furthermore, the water has a mass fraction of not less than 15%.

[0007] Furthermore, the etching rate modifier is represented by the following general formula: ; Where n is an integer from 2 to 12, and R1, R2, and R3 are independent functional groups.

[0008] Furthermore, R1 and R2 are alkyl groups with 0-15 carbon atoms, alkenes with 2-8 carbon atoms, alkynes with 2-8 carbon atoms, hydroxyalkyl groups with 1-20 carbon atoms, aminoalkyl groups with 1-20 carbon atoms, alkyl groups with phosphate esters with 1-20 carbon atoms, carboxyl groups, or acetoxy groups; R3 is methyl, ethyl, propyl, butyl, methoxy, ethoxy, aminopropyl, glycidyl, or mercapto.

[0009] Furthermore, the pH buffer is one or more combinations of ammonium citrate, citric acid, ammonium maleate, ammonium malonate, ammonium oxalate, ammonium succinate, gallic acid, ammonium acetate, acetic acid, tartaric acid, ascorbic acid, glycolic acid, hydroxyethylidene diphosphonic acid, ethylenediaminetetramethylenephosphonic acid, aminotrimethylenephosphonic acid, ethylenediaminetetraacetic acid, ammonium phosphate, ammonium carbonate, ammonium nitrate, ammonium chloride, ammonium dihydrogen phosphate, and ammonium bicarbonate.

[0010] Furthermore, the raw materials used are composed of phosphoric acid with a concentration of ≥85%, pH buffer with a concentration of ≥99%, nitric acid with a concentration of 70%, fluoride with a concentration of ≥10%, and silicon-containing additives.

[0011] Furthermore, the fluorinated additive includes one or more combinations of hydrofluoric acid, ammonium fluoride, ammonium hydrogen fluoride, fluoroboric acid, and fluorosilicic acid.

[0012] The beneficial effects of this invention are: This invention can rapidly etch aluminum wires and aluminum alloys doped with a small amount of silicon commonly used in semiconductor manufacturing. When processing aluminum alloys doped with silicon, it removes the aluminum wires and the silicon remaining after etching the aluminum. At the same time, it adds an etching rate regulator to control the etching rate of the substrate SiO2 and prevents excessive etching of the underlying SiO2.

[0013] The above description is merely an overview of the technical solution of the present invention. In order to better understand the technical means of the present invention and to implement it in accordance with the contents of the specification, the preferred embodiments of the present invention are described in detail below with reference to the accompanying drawings. Attached Figure Description

[0014] Figure 1 This is a picture showing silicon residue after etching in Comparative Example 1; Figure 2 This is a picture of Comparative Example 5 showing no silicon residue after etching; Figure 3 This is an EDS test of silicon residue after etching in Comparative Example 1. Detailed Implementation

[0015] The preferred embodiments of the present invention will now be described in detail with reference to the accompanying drawings, so that the advantages and features of the present invention can be more easily understood by those skilled in the art, thereby providing a clearer and more explicit definition of the scope of protection of the present invention. Specific implementation examples: like Figures 1 to 2 The Al etching solution shown is capable of removing Si residue and comprises, by weight, 35%-65% phosphoric acid; 0.1%-10% nitric acid; 5%-30% pH buffer, preferably 5%-10%; 0.01%-3% fluorine-containing additive, with the remainder being water.

[0017] Preferably, it also includes 0.1%-5% of an etching rate modifier, wherein the etching rate modifier is an amino organosiloxane, and specifically, the water mass fraction is not less than 15%.

[0018] Furthermore, the etching rate modifier is represented by the following general formula: ; Where n is an integer from 2 to 12, and R1, R2, and R3 are independent functional groups.

[0019] Furthermore, R1 and R2 are alkyl groups with 0-15 carbon atoms, olefins with 2-8 carbon atoms, alkynes with 2-8 carbon atoms, hydroxyalkyl groups with 1-20 carbon atoms, aminoalkyl groups with 1-20 carbon atoms, alkyl groups with phosphate esters with 1-20 carbon atoms, carboxyl groups, or acetoxy groups; R3 is methyl, ethyl, propyl, butyl, methoxy, ethoxy, aminopropyl, glycidyl, or mercapto. Preferably, it is an amino organosiloxane containing two alkoxy groups. The two alkoxy groups can control its hydrolysis rate. When it is adsorbed on the SiO2 surface, it can inhibit the etching of Si and SiO2 to a certain extent, thereby controlling its etching rate. The amino group on the SiO2 surface can inhibit the corrosion of SiO2 by fluorine-containing additives and improve its surface hydrophilicity. R3 is an independent functional group, including methyl, ethyl, propyl, butyl, methoxy, ethoxy, aminopropyl, glycidyl, and mercapto groups. Its important function is to modify the steric hindrance and improve the solubility and stability of the etching rate regulator in solution. The selected etching rate regulator does not react with fluorine-containing additives and is not oxidized by nitric acid.

[0020] In this embodiment, several possible references are given:

[0021] Formula 1

[0022] Formula 2

[0023] Formula 3

[0024] Formula 4 Furthermore, the pH buffer is generally a weak organic / inorganic acid, such as ammonium citrate, citric acid, ammonium maleate, ammonium malonate, ammonium oxalate, ammonium succinate, gallic acid, ammonium acetate, acetic acid, tartaric acid, ascorbic acid, glycolic acid, hydroxyethylidene diphosphonic acid, ethylenediaminetetramethylidene phosphonic acid, aminotrimethylidene phosphonic acid, ethylenediaminetetraacetic acid, ammonium phosphate, ammonium carbonate, ammonium nitrate, ammonium chloride, ammonium dihydrogen phosphate, and ammonium bicarbonate, or a combination thereof. The fluorinated additive includes one or more combinations of hydrofluoric acid, ammonium fluoride, ammonium bifluoride, fluoroboric acid, and fluorosilicic acid. Of course, all of the above fluorinated additives are electronic grade. In this embodiment, ammonium acetate and ammonium citrate pH buffers are preferred. The pH buffer can control the reaction rate and improve the etching solution life in solution. In this embodiment, the fluorine-containing additive is preferably 1% hydrofluoric acid, or a mixture of 0.5% hydrofluoric acid and 1% ammonium bifluoride, etc. The addition of the fluorine-containing additive can rapidly corrode the Al-Si alloy without causing Si residue.

[0025] Furthermore, the raw materials used are composed of phosphoric acid with a concentration of ≥85%, pH buffer with a concentration of ≥99%, nitric acid with a concentration of 70%, fluoride with a concentration of ≥10%, and silicon-containing additives. Of course, all of the above raw materials are electronic grade.

[0026] The following is a comparison of the effects of the present invention with experimental results: Experiment 1: In this experiment, phosphoric acid and nitric acid were used as the main components of the etching solution, acetic acid was used as the pH buffer, and hydrofluoric acid was used as the fluorine-containing compound. This example tested the dosage of each of the above components and included four comparative experiments, with the commonly used commercial aluminum etching solution formulation PNA as the comparison ratio. See Table 1 for details. All percentages in Table 1 are mass percentages, representing the percentage of the component by weight of the total etching solution; the balance is deionized water.

[0027] Table 1

[0028] Test method: The etching solutions were prepared according to the dosages in Table 1, and used to etch AlSiCu blanket wafers, AlSiC / SiO2 / Si wafers, and SiO2CVD blanket wafers (silicon dioxide surface fully covered deposition wafers). Specifically, the AlSiCu / SiO2 / Si wafer was prepared by first CVD growing a 2000Å layer of SiO2 on the Si wafer, followed by PVD sputtering of a 45000Å AlSiCu layer. The AlSiCu blanket wafer was prepared by PVD sputtering a 45000Å AlSiCu layer directly onto the Si substrate. The SiO2CVD blanket wafer was prepared by CVD depositing a 2000Å layer of SiO2 on the Si wafer. The etching effect testing procedure is as follows: First, AlSiCu blanket wafers, AlSiC / SiO2 / Si wafers and SiO2CVD blanket wafers are cut into 2cm×2cm pieces. Then, the various etchant solutions are used to etch the wafers at 65℃. The Si residue effect after etching AlSiC / SiO2 / Si wafers is evaluated by FE-SEM test. The etching rate of AlSiCu is tested with a four-probe tester, and the etching rate of SiO2 is tested with an ellipsometry.

[0029] Si residual effects were assessed at 10% OE, 20% OE, and 40% OE times. The OE calculation method is as follows: OE=(t*ER-Film THK) / film THK Define the test result markers: × for no effect; ▷ for average; ○ for relatively clean; ◎ for very clean.

[0030] The results are as follows: Table 2 shows that the unit of ER is A / min.

[0031] The results are shown in Table 2: (1) In Comparative Examples 1, 2 and 3, the higher the nitric acid content and the lower the pH buffer content, the faster the corrosion rate of AlSiCu. A faster corrosion rate can effectively improve the efficiency of the process and reduce costs and increase efficiency. However, an excessively fast AlSiCu etching rate can lead to instability in the corrosion process. Therefore, the etching rate of AlSiCu can be effectively controlled.

[0032] (2) Comparing Examples 1-4 with Comparative Examples 1-3, only the formulation containing F compound has the effect of cleaning silicon slag. This is because under acidic conditions, F ions will react with Si to generate tetrafluorosilicic acid, which can dissolve in the solution. However, the addition of F ions will affect the etching of Al on the one hand, and will severely corrode SiO2 on the substrate on the other hand. Therefore, its ratio needs to be strictly controlled.

[0033] To address substrate corrosion issues, an etching rate modifier can be added to the formulation. This effectively inhibits SiO2 corrosion on the substrate without affecting the removal of silicon slag.

[0034] Experiment 2: This experiment tested the dosage of the above components and set up four comparative experiments, with the comparative example being the commercial aluminum etching solution formulation PNA containing component F. See Table 3 for details. All percentages in Table 3 are mass percentages, representing the percentage of the component by weight of the total etching solution; the balance is deionized water.

[0035] Table 3

[0036] The testing method is the same as above, and will not be described in detail.

[0037] The results are as follows: Table 4:

[0038] As shown in Table 4: (1) Comparative Examples 1-3 show that the PNA solution with added F ions will rapidly corrode the underlying SiO2. While cleaning away silicon residue, it will severely corrode the substrate. In Examples 1-13, an etching rate regulator (aminosiloxane) was added. Therefore, aminosilane coupling agent was selected as the etching rate regulator, which can effectively hinder the etching rate of SiO2. (2) In Examples 2-7, the addition of aminopropylmethyldiethoxysilane, aminopropyltriethoxysilane, and aminopropyltrimethoxysilane can effectively inhibit the etching rate of SiO2. However, compared with Example 2, which can be cleaned very well with 10% OE, the effect in Examples 4-7 is significantly worse than that in Comparative Example 2. This indicates that although this additive can effectively inhibit the corrosion of the substrate SiO2, it can also slightly inhibit the removal of silicon slag. Extending the time can also effectively remove silicon slag. Meanwhile, in Example 13, the addition of (nitro-aminoethylaminopropyl)triethoxysilane under 40% OE conditions also resulted in a relatively poor cleaning effect on Si slag. (3) In Examples 7-11, the etching solution of Formula (2) is added, which has the best effect on inhibiting the etching of SiO2. When the HBF4 content is 2%, the etching rate is the lowest at 5.5A / min. At this time, under 20% OE time, it can completely remove the Si residue on the surface of the silicon wafer.

[0039] The above description is merely an embodiment of the present invention and does not limit the patent scope of the present invention. Any equivalent structural transformations made based on the content of the present invention specification and drawings, or direct or indirect applications in other related technical fields, are similarly included within the patent protection scope of the present invention.

Claims

1. An Al etching solution capable of removing Si residue, characterized in that: By mass component, including: 35%-65% of phosphoric acid; 0.1%-10% of nitric acid; 5%-30% of PH buffer; 0.01%-3% of fluorine-containing additive, the rest is water.

2. The Al etching solution capable of removing Si residue according to claim 1, wherein: Also including 0.1%-5% of etching rate regulator, the etching rate regulator is amino organosiloxane.

3. The Si residue removable Al etching liquid according to claim 1 or 2, characterized in that: The mass fraction of the water is not less than 15%.

4. The Al etching solution capable of removing Si residue according to claim 2, wherein: The etching rate regulator is represented by the following general formula: ； Wherein n is an integer of 2-12, R1, R2, R3 are independent groups.

5. The Al etching solution capable of removing Si residue according to claim 4, wherein: The R1 and R2 are alkyl with 0-15 C atoms, olefin with 2-8 C atoms, alkyne with 2-8 C atoms, 1-20 hydroxyalkyl, 1-20 aminoalkane, 1-20 alkyl with phosphate group, 1-20 alkyl with sulfate group, carboxyl or acetoxy; R3 is methyl, ethyl, propyl, butyl, methoxy, ethoxy, aminopropyl, epoxypropyl or mercapto.

6. The Al etching solution capable of removing Si residue according to claim 1, wherein: The PH buffer is one or more combinations of ammonium citrate, citric acid, ammonium maleate, ammonium malonate, ammonium oxalate, ammonium succinate, gallic acid, ammonium acetate, acetic acid, tartaric acid, ascorbic acid, glycolic acid, hydroxyethylidene diphosphonic acid, ethylenediaminetetramethylene phosphonic acid, aminotrimethylene phosphonic acid, ethylenediaminetetraacetic acid, ammonium phosphate, ammonium carbonate, ammonium nitrate, ammonium chloride, ammonium dihydrogen phosphate and ammonium bicarbonate.

7. The Al-etchant liquid capable of removing Si residue according to claim 1, wherein: The concentration of the raw materials used is that the content of phosphoric acid is ≥85%, the content of PH buffer is ≥99%, the content of nitric acid is 70%, the content of fluoride and silicon-containing additive is ≥10%.

8. The Al-etchant liquid capable of removing Si residue according to claim 1, wherein: The fluorine-containing additive includes one or more combinations of hydrofluoric acid, ammonium fluoride, ammonium bifluoride, fluoroboric acid, fluorosilicic acid.

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