Buffer oxide etching solution

Abstract

The invention discloses a buffer oxide etching solution. The etching solution mainly comprises hydrofluoric acid, ammonium fluoride, sterically hindered alcohol, organic amine and ultrapure water. The etching solution is used for etching the silicon oxide film, and surface defects of the etched silicon oxide film can be reduced. The steric hindrance alcohol used in the invention has good dispersibility in a solution system, and can ensure good uniformity of the etched silicon oxide film, and the organic amine can change the surface potential of the etched silicon oxide film and reduce the surface particle adhesion of the silicon oxide film, so that the defects of the etched silicon oxide film are reduced, and the stability of the subsequent manufacturing process can be ensured.

Description

Technical Field

[0001] This invention belongs to the field of etching solution technology. The etching solution is used for etching silicon oxide thin films and can reduce surface defects after silicon oxide etching, ensure the stability of subsequent manufacturing processes, and improve product yield. Background Technology

[0002] Silicon oxide is commonly used in modern MOSFETs as an insulating dielectric layer (gate oxide) between the gate (metal or polysilicon) and the channel (silicon substrate). Silicon oxide is also frequently used for electrical isolation between devices (field oxide) to prevent unwanted current leakage between adjacent devices. After transistor fabrication, multiple layers of metal interconnects need to be built on top, and silicon oxide is widely used as an insulating layer between these metal layers. In special structures, silicon oxide films can be used as sacrificial layers. After the structural layers are deposited and patterned, the silicon oxide sacrificial layer is removed using a functional wet etching solution, thereby releasing the suspended structure.

[0003] For removing large areas of silicon oxide, such as field oxide layers and sacrificial layers, wet etching with buffered oxide etchant (BOE) is commonly used. The depressions / micro-voids created after etching the silicon oxide film can lead to poor metal filling, increasing resistance or the risk of open circuits. It can also cause direct contact between upper and lower metal layers, resulting in short circuits or high leakage current. This invention provides a buffered oxide etchant that produces a uniform silicon oxide film after etching, reduces surface defects after etching, ensures the stability of subsequent manufacturing processes, and improves product yield. Summary of the Invention

[0004] This invention provides a buffer oxide etching solution and its preparation method. The etching solution can reduce surface defects after silicon oxide etching, and the silicon oxide surface exhibits excellent uniformity after etching.

[0005] This invention relates to a buffered oxide etching solution, the composition of which includes: 2-6% hydrofluoric acid, 15-25% ammonium fluoride, 0.01-0.15% sterically hindered alcohol, 0.02-0.3% organic amine, and the remainder being ultrapure water.

[0006] Furthermore, the present invention relates to the above-mentioned etching solution, wherein the hydrofluoric acid is electronic grade and has a mass concentration of 48-50%.

[0007] Furthermore, the present invention relates to the above-mentioned etching solution, wherein the ammonium fluoride is electronic grade and has a mass concentration of 39-41.5%.

[0008] Furthermore, the present invention relates to the above-mentioned etching solution, wherein the resistivity of ultrapure water at 25°C is not less than 18 megohms.

[0009] Furthermore, the present invention relates to the above-mentioned etching solution, wherein the sterically hindered alcohol is at least one selected from 2-decyl-1-tetradecanool, 3-oxetanetanol, 2-phenyl-2-butanol, 2-benzylamino-2-methyl-1-propanol, and 1,3-bis(dimethylamino)-2-propanol.

[0010] Furthermore, the present invention relates to the above-mentioned etching solution, wherein the organic amine is at least one selected from 1-piperazine butylamine, 4-piperazinylaniline, 2-piperazine nicotinamide, 1-piperazine-1-isoquinoline, 4-piperazine piperidine, and 4-piperazine benzenesulfonamide.

[0011] Furthermore, the present invention relates to the above-mentioned etching solution, wherein the optimal mass ratio of sterically hindered alcohol to organic amine is 1:1 to 1:10.

[0012] Furthermore, the present invention relates to the above-mentioned etching solution, wherein hydrofluoric acid is used to etch the silicon oxide layer; ammonium fluoride is used to provide fluoride ions to stabilize the etching rate of the etching solution; sterically hindered alcohol can reduce interfacial energy and provide steric hindrance, which can prevent the etching solution from forming bubbles in the microstructure, hinder particle aggregation in space, and improve the uniformity of silicon oxide surface after etching; organic amine can change the surface potential of silicon oxide film after etching, reduce particle adhesion on silicon oxide surface, and reduce surface defects of silicon oxide film after etching.

[0013] Furthermore, the silicon oxide thin film used in this invention is Thermal Oxide, PECVD Oxide, BPSG, TEOS, PSG, or FSG.

[0014] Furthermore, the present invention relates to the above-mentioned etching solution, specifically to a silicon oxide etching solution that requires high uniformity and low surface defects. Attached Figure Description

[0015] Figure 1 This is a schematic diagram showing the absence of defects after silicon oxide etching in the embodiment.

[0016] Figure 2 This is a schematic diagram showing defects in silicon oxide after etching in a comparative example.

[0017] Figure 3 This is a schematic diagram showing the clarification of the etching solution's properties.

[0018] Figure 4 This is a schematic diagram showing the turbidity of the etching solution. Detailed Implementation

[0019] The present invention will be further illustrated by the following embodiments, but the present invention is not limited to the embodiments described.

[0020] First, prepare the etching solution according to its composition and stir for 60 minutes. Place the PFA bottle containing the etching solution in a low-temperature constant temperature bath (25℃) and keep it at that temperature for 2 hours. Then, place the silicon oxide thin film wafer into the etching solution and slowly stir to etch it. The thickness of the silicon oxide wafer before and after etching is measured using an ellipsometry. The corresponding etching rate is calculated based on the thickness difference before and after etching / etching time, and the U value is calculated. U = (max - min) / (2 * average). The surface of the silicon oxide after etching is photographed using a super depth-of-field microscope.

[0021] Example 1 The composition of Example 1 is: 5% hydrofluoric acid, 20% ammonium fluoride, 0.1% 2-decyl-1-tetradecaneol, 0.15% 1-piperazinebutamine, and the balance is water.

[0022] Example 2 The composition of Example 2 is: 3% hydrofluoric acid, 25% ammonium fluoride, 0.08% 3-oxetanebutanol, 0.08% 4-piperazine benzenesulfonamide, and the balance is water.

[0023] Example 3 The composition of Example 3 is: 4% hydrofluoric acid, 15% ammonium fluoride, 0.05% 1,3-bis(dimethylamino)-2-propanol, 0.1% 1-piperazine-1-isoquinoline, and the balance is water.

[0024] Example 4 The composition of Example 4 is: 2% hydrofluoric acid, 18% ammonium fluoride, 0.03% 2-phenyl-2-butanol, 0.2% 2-piperazine nicotinamide, and the balance is water.

[0025] Example 5 The composition of Example 5 is: 6% hydrofluoric acid, 23% ammonium fluoride, 0.06% 1,3-bis(dimethylamino)-2-propanol, 0.18% 4-piperazinpiperidine, and the balance is water.

[0026] Comparative Example 1 The composition of Comparative Example 1: 5% hydrofluoric acid, 20% ammonium fluoride, and the balance being water.

[0027] Comparative Example 2 The composition of Comparative Example 2 was: 5% hydrofluoric acid, 20% ammonium fluoride, 0.1% 2-decyl-1-tetradecanool, and the balance being water.

[0028] Comparative Example 3 The composition of Comparative Example 3 was: 5% hydrofluoric acid, 20% ammonium fluoride, 0.15% 1-piperazinebutamine, and the balance being water.

[0029] Comparative Example 4 The composition of Comparative Example 4 was: 5% hydrofluoric acid, 20% ammonium fluoride, 0.01% 2-decyl-1-tetradecanool, 0.01% 1-piperazinebutamine, and the balance being water.

[0030] Comparative Example 5 The composition of Comparative Example 5 was: 5% hydrofluoric acid, 20% ammonium fluoride, 0.3% 2-decyl-1-tetradecanool, 0.3% 1-piperazinebutamine, and the balance being water.

[0031] Comparative Example 6 The composition of Comparative Example 6 is: 5% hydrofluoric acid, 20% ammonium fluoride, 0.1% ethylene glycol, 0.15% pentylamine, and the balance being water.

[0032] Comparative Example 7 The composition of Comparative Example 7 is: 5% hydrofluoric acid, 20% ammonium fluoride, 0.1% n-undecyl alcohol, 0.15% n-heptylamine, and the balance is water.

[0033] Comparative Example 8 The composition of Comparative Example 8 was: 5% hydrofluoric acid, 20% ammonium fluoride, 0.1% 3,7-dimethyl-7-octenol, 0.15% cycloheptaneamine, and the balance being water.

[0034] Comparative Example 9 The composition of Comparative Example 9 was: 5% hydrofluoric acid, 20% ammonium fluoride, 0.1% 3-butene-1,2-diol, 0.15% 2-methyl-2-butamine, and the balance being water.

[0035] Table 1. Etching rate, U-value, surface condition after etching, and properties of etching solution

[0036] As can be seen from the table, the etching solutions in Examples 1-5 were all in a clear state (e.g., Figure 3 No circular defects (such as) appeared on the surface after etching with thermal oxide by the etching solution. Figure 1 Furthermore, the uniformity after thermal oxidation was excellent (U value < 0.2). Comparative Example 1, which did not contain hindered alcohols or organic amines, showed circular defects on the surface after thermal oxidation (e.g., ...). Figure 2 Comparative Example 2, containing hindered alcohol, exhibited excellent uniformity after etching, but circular defects appeared on the surface. Comparative Example 3, containing organic amine, did not show circular defects on the surface after etching, but had poor uniformity. Comparative Example 4, containing a small amount of hindered alcohol and organic amine, showed better uniformity than Comparative Example 1 after etching, but circular defects appeared on the surface. Comparative Example 5, containing an excess of hindered alcohol and organic amine, did not show circular defects on the surface after etching, but the solution was turbid (e.g., ...). Figure 4The uniformity was poor. In Comparative Examples 6-9, when the sterically hindered alcohol and organic amine were replaced, circular spot defects appeared on the surface after etching, and the uniformity after etching was poor.

[0037] Obviously, the above embodiments and comparative examples are for illustrative purposes only and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description, and it is neither necessary nor possible to exhaustively list all possible implementations. Therefore, any obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. A buffered oxide etching solution, characterized in that, The etching solution consists of 2-6% hydrofluoric acid, 15-25% ammonium fluoride, 0.01-0.15% sterically hindered alcohol, 0.02-0.3% organic amine, and the remainder is ultrapure water.

2. The buffered oxide etching solution according to claim 1, characterized in that, The hydrofluoric acid in the etching solution is electronic grade, with a mass concentration of 48-50%.

3. The buffered oxide etching solution according to claim 1, characterized in that, The ammonium fluoride in the etching solution is electronic grade, with a mass concentration of 39-41.5%.

4. The buffered oxide etching solution as described in claim 1, characterized in that, The resistivity of the ultrapure water at 25°C is not less than 18 megohms.

5. The buffered oxide etching solution as described in claim 1, characterized in that, The sterically hindered alcohol is selected from at least one of 2-decyl-1-tetradecanool, 3-oxetanebutanol, 2-phenyl-2-butanol, 2-benzylamino-2-methyl-1-propanol, and 1,3-bis(dimethylamino)-2-propanol.

6. The buffered oxide etching solution as described in claim 1, characterized in that, The organic amine is selected from at least one of 1-piperazine butylamine, 4-piperazinylaniline, 2-piperazine nicotinamide, 1-piperazine-1-isoquinoline, 4-piperazine piperidine, and 4-piperazine benzenesulfonamide.

7. The buffered oxide etching solution as described in claim 1, characterized in that, The optimal mass ratio of the sterically hindered alcohol to the organic amine is 1:1 to 1:

10.

8. The application of a buffered oxide etchant as described in any one of claims 1-7 in the etching of silicon oxide thin films.

9. The application according to claim 8, characterized in that, Silica films include any one of Thermal Oxide, PECVDOxide, BPSG, TEOS, PSG, and FSG.

10. The application according to claim 8, characterized in that, No circular defects appeared on the surface of the silicon oxide film after etching by the etching solution, and the uniformity U value after thermal oxide etching was <0.2.

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