CN115181569B

CN115181569B - Silicon oxide selective etching solution

Info

Publication number: CN115181569B
Application number: CN202210794775.5A
Authority: CN
Inventors: 张庭; 贺兆波; 李金航; 叶瑞; 李鑫; 武昊冉; 徐子豪
Original assignee: Hubei Xingfu Electronic Materials Co ltd
Current assignee: Hubei Xingfu Electronic Materials Co ltd
Priority date: 2022-07-07
Filing date: 2022-07-07
Publication date: 2023-05-09
Anticipated expiration: 2042-07-07
Also published as: CN115181569A

Abstract

The invention provides a selective etching solution for silicon oxide, which comprises hydrofluoric acid, ammonium fluoride, an inhibitor, an additive and ultrapure water. The silicon oxide film layer and the metal film layer are selectively etched, a stable protective film is formed on the surface of the metal through the synergistic effect of carbonyl, amino and hydroxyl groups of the inhibitor and the additive, the silicon oxide is selectively etched, the etching selectivity ratio is more than 15, and the surface roughness of the etched metal layer is less than 4 nm; meanwhile, the etching liquid can be quickly wetted into the deep hole structure, and the silicon oxide layer around the deep hole structure is completely etched.

Description

Silicon oxide selective etching solution

Technical Field

The invention belongs to the field of etching solutions, and particularly relates to a selective etching solution for silicon oxide.

Background

In the back-end process flow of semiconductor manufacture, a deep hole structure needs to be etched on a silicon oxide film layer by dry etching, then the silicon oxide layer around the deep hole is removed by wet etching until a metal layer is etched, and the etching liquid is required to damage the metal layer little in the wet etching treatment process so as not to influence the electrical performance of the chip.

The silicon oxide layer is etched and removed by using a buffer oxide etching solution (HF+NH) ₄ F+DIW), but buffered oxide etchantOver-etching of the metal layer may result. Meanwhile, the buffer oxide etching liquid cannot effectively wet the silicon oxide layer in the deep hole structure, so that the silicon oxide layer is incompletely etched.

Disclosure of Invention

The invention provides a selective etching solution for silicon oxide, which can be quickly wetted into a deep hole structure after dry etching, completely etch a silicon oxide layer around the deep hole structure and protect a metal layer from being etched in a small amount.

The technical scheme of the invention is that the silicon oxide selective etching solution comprises 0.1-5wt% of hydrofluoric acid, 10-30wt% of ammonium fluoride, 0.01-0.2wt% of amide inhibitor, 0.005-0.1wt% of amino alcohol additive and the balance of ultrapure water.

Further, the hydrofluoric acid content in the etching liquid is 2-4wt%.

Further, the content of ammonium fluoride in the etching solution is 15-25wt%.

Further, the amide inhibitor is one or more of 2-aminopropionamide, 2-aminobutanamide, 2-amino-2, 3-dimethylbutyramide, 3-aminopropionamide, 3- (methylamino) propionamide and 3- (propylamino) propionamide.

Further, the additive is one or more of 2-amino n-butanol, 4-amino-2-butanol, 2-amino-3-methyl-1-butanol, 4-amino-1-butanol, 3-diethylamino-1-propanol, 5-amino-2, 2-dimethyl amyl alcohol and D-aminopropanol.

Further, the selective etching is selective etching of the silicon oxide layer and the metal layer by the etching solution.

The invention also relates to application of the silicon oxide selective etching solution in deep hole structure silicon oxide etching.

The invention has the following beneficial effects:

1. in the invention, the inhibitor contains carbonyl groups and amino groups, the additive contains amino groups and hydroxyl groups, the carbonyl has negative effect, the amino groups and the hydroxyl groups have stronger electrostatic effect, the effects have the action of electron couples, in the amino chemical absorption action, the protective performance is enhanced due to the action of free electron couples and the nucleophilic action of the amino groups, meanwhile, the hydroxyl groups have synergistic action, a stable protective film can be formed on the surface of the metal, the metal is protected from being etched by a small amount, and the surface roughness of the metal layer before and after etching is unchanged; the electrical performance of the chip is not affected.

2. The etching liquid can be quickly wetted into the deep hole structure, and the silicon oxide layer around the deep hole structure is completely etched. The etching selectivity ratio of the silicon oxide layer to the metal layer is more than 15, and the surface roughness of the metal layer before and after etching is consistent.

Drawings

Fig. 1 is a deep hole structure diagram before etching.

Fig. 2 is a structural diagram of BPSG complete etching.

Fig. 3 is a structural diagram of BPSG incompletely etched.

Detailed Description

Embodiments of the present invention will be described in detail below with reference to examples, but it will be understood by those skilled in the art that the following examples are only for illustrating the present invention and should not be construed as limiting the scope of the present invention.

In order to facilitate verification of the etching selectivity effect of the etching solution, BPSG single-layer wafer and AlCu single-layer wafer are used for collecting etching rate data, the etching rate is calculated by measuring the thickness before and after etching through an ellipsometry, AFM is used for detecting roughness before and after etching of AlCu wafer, and SEM is used for observing the etching condition of a BPSG layer in a deep hole structure after dry etching of a structural sheet.

The etching temperature used in the embodiment of the invention is 23 ℃, the etching time is 2min, and the etching mode is stirring etching.

The components and contents of the examples are shown in Table 1.

TABLE 1

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The experimental results are shown in Table 2.

TABLE 2

As can be seen from Table 2, the etching selectivity of the BPSG and AlCu layers in examples 1-15 is > 15; the difference of roughness of the AlCu layer before and after etching is small, and the etching solution of the embodiment has small influence on the surface roughness of the AlCu layer after etching; the etching solution of the embodiment can be quickly wetted to the deep hole structure, and the BPSG layer around the deep hole structure is completely etched.

The comparative example 1 contains no inhibitor and additive, and has a fast etching rate of the AlCu layer, a large roughness after etching, and poor wettability of the etching solution, resulting in incomplete etching of the BPSG layer around the deep hole structure. In the comparative example 2, the inhibitor only contains carbonyl groups and amino groups, so that a certain protection effect is achieved on the AlCu layer, the etching rate of the AlCu layer is reduced, but the etching selectivity of the BPSG layer and the AlCu layer is only improved to 9; meanwhile, the roughness difference between the etched AlCu layer and the etched AlCu layer is large, and the BPSG layer around the deep hole structure is not completely etched. In the comparative example 3, only the additive is contained, the additive contains amino groups and hydroxyl groups, and no carbonyl groups and no electron coupling function are contained, so that the additive has no protection effect on the AlCu layer, the etching rate of the AlCu layer is consistent with that in the comparative example 1, and the etching selectivity of the BPSG layer and the AlCu layer is not improved. The comparative example 4 contains an inhibitor and an additive, the inhibitor content is less than 0.01wt%, the etching rate of the AlCu layer is lower than that of the comparative example 1, but the etching selectivity of the BPSG and AlCu layers is increased only to 5. The comparative example 5 contains an inhibitor and an additive, the inhibitor content is higher than 0.2wt%, the etching selectivity of the BPSG and AlCu layers is identical to that of the examples, the etching selectivity is not further improved, and the optimum selectivity can be achieved in the range of 0.01-0.2wt% in view of the cost. The comparative example 6 contains an inhibitor and an additive, the content of the additive is lower than 0.005wt%, the synergistic effect of hydroxyl groups in the additive is weak, a certain protection effect is provided for AlCu layers, but the etching selectivity of BPSG and AlCu layers is only improved to 10; due to the low content of the additive, the roughness of the AlCu layer after etching is high, and the BPSG layer around the deep hole structure is not completely etched. The comparative example 7 contains an inhibitor and an additive in an amount of more than 0.1wt%, and the etching selectivity of the BPSG and AlCu layers is identical to that of the examples, and the etching selectivity is not further improved, and the optimum selectivity can be achieved in the range of 0.005 to 0.1wt% in consideration of the cost.

The inhibitor in comparative example 8 is coconut oil fatty acid diethanolamide, and the chemical adsorption of amino groups is weakened because the coconut oil fatty acid diethanolamide does not contain amino groups, so that the inhibitor has a certain inhibiting effect on etching of AlCu layers, but the effect is not obvious.

It is apparent that the above examples and comparative examples are only examples made for clarity of illustration and are not limiting of the embodiments. Other variations or modifications of the various aspects will be apparent to those of skill in the art upon review of the foregoing description, and it is not necessary nor intended to be exhaustive of all embodiments. And thus obvious variations or modifications to the disclosure are within the scope of the invention.

The foregoing embodiments are merely preferred embodiments of the present invention, and should not be construed as limiting the present invention, and the embodiments and features of the embodiments in the present application may be arbitrarily combined with each other without collision. The protection scope of the present invention is defined by the claims, and the protection scope includes equivalent alternatives to the technical features of the claims. I.e., equivalent replacement modifications within the scope of this invention are also within the scope of the invention.

Claims

1. A selective etching solution for silicon oxide, which is characterized in that: the etching solution comprises 0.1-5wt% of hydrofluoric acid, 10-30wt% of ammonium fluoride, 0.01-0.2wt% of amide inhibitor, 0.005-0.1wt% of amino alcohol additive and the balance of ultrapure water; the amide inhibitor is one or more of 2-aminopropionamide, 2-aminobutanamide, 2-amino-2, 3-dimethylbutyramide, 3-aminopropionamide, 3- (methylamino) propionamide and 3- (propylamino) propionamide; the amino alcohol additive is one or more of 2-amino n-butanol, 4-amino-2-butanol, 2-amino-3-methyl-1-butanol, 4-amino-1-butanol, 3-diethylamino-1-propanol, 5-amino-2, 2-dimethyl amyl alcohol and D-amino propanol.

2. The selective etching solution for silicon oxide according to claim 1, wherein: the hydrofluoric acid content in the etching solution is 2-4wt%.

3. The selective etching solution for silicon oxide according to claim 2, wherein: the ammonium fluoride content in the etching solution is 15-25wt%.

4. The selective etching solution for silicon oxide according to claim 1, wherein: the selective etching is the selective etching of the silicon oxide layer and the metal layer by the etching solution.

5. The use of the selective etching solution for silicon oxide according to any one of claims 1 to 4 in deep hole structure silicon oxide etching.