Method for monitoring SiO2 wet etching end point

Abstract

The invention belongs to the field of semiconductor manufacturing, and relates to a method for monitoring a SiO2 wet etching end point, which comprises the following steps of: producing a SiO2 film with a silica-to-oxygen ratio of X and obvious color, namely an accompanying film 1; obtaining a SiO2 diaphragm of a formal product, and enabling the SiO2 diaphragm and the accompanying diaphragm 1 to participate in etching at the same time to obtain an etching rate ratio A; a formal product and the SiO2 film thickness d of the formal product are obtained, a SiO2 film with the silica-to-oxygen ratio being X and the film thickness being d * A is plated on the formal product, and then an accompanying film 2 is obtained; the formal product and the accompanying wafer 2 participate in etching at the same time, and when the obvious color of the accompanying wafer 2 falls off completely, the current time is recorded as the etching end point time T0; the final etching time T1 is calculated according to T0, and when the etching time of the formal product reaches T1, etching of the formal product is completed; the method comprises the following steps: coating a formal product with a SiO2 film with the thickness of d * Anm, namely an accompanying film 2; and the actual etching end point of the formal product is confirmed by judging whether the accompanying wafer 2 reaches the etching end point or not, so that the accuracy of the etching time is improved.

Description

Technical Field

[0001] The invention belongs to the manufacturing field of semiconductors, panels and the like, and relates to a method for monitoring the end point of SiO2 wet etching. Background Art

[0002] Currently, hydrofluoric acid solution or etching solution containing hydrofluoric acid is mainly used to wet-etch SiO2, and the etching time is mainly calculated based on the coating film thickness and the wet etching rate.

[0003] Since the etching time is calculated in advance based on the film thickness and etching rate, and the etching rate has a certain volatility and the actual value cannot be known in real time, the calculated etching time is not the actual etching endpoint time. Summary of the invention

[0004] In order to solve the above-mentioned prior art problems, the present invention adopts a method for monitoring the endpoint of SiO2 wet etching, comprising:

[0005] S1, producing a SiO2 film with obvious color by adjusting the silicon-oxygen ratio, namely, accompanying film 1; the silicon-oxygen ratio of accompanying film 1 is X;

[0006] S2, obtaining the SiO2 film of the formal product, etching the companion film 1 and the SiO2 film of the formal product at the same time, and obtaining an etching rate ratio A of the companion film 1 and the SiO2 film of the formal product;

[0007] S3, obtain the formal product and its SiO2 film thickness d, and produce a SiO2 film with a silicon-oxygen ratio of X and a film thickness of d×Anm, i.e., companion film 2;

[0008] S4, etching the formal product and the accompanying film 2 at the same time, when the obvious color of the accompanying film 2 falls off, the current time is recorded as the etching end time T0;

[0009] S5. Calculate the final etching time T1 according to the etching endpoint time T0. When the etching time of the formal product reaches the final etching time T1, the etching of the formal product is completed.

[0010] Preferably, the silicon-oxygen ratio X is 1:1.6.

[0011] The final etching time is calculated according to the etching endpoint time T0 as follows: T1 = (1 + α)·T0; wherein α is the ratio of the over-etching amount.

[0012] Preferably, the ratio α of the over-etching amount is 10%.

[0013] Beneficial effects:

[0014] 1. Before etching the formal product, a SiO2 film with a thickness of d×A nm, namely, the companion film 2, is plated on the formal product; and by judging whether the companion film 2 has reached the etching end point, the actual etching end point of the formal product is confirmed. The etching time of the present invention has a higher accuracy than that calculated by the rate and the film thickness, and reduces the corrosiveness of the etching solution to the lower film layer structure; 2. The present invention improves the uniformity between batches in the wet etching process. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 A flow chart of a method for monitoring SiO2 wet etching endpoint provided by an embodiment of the present invention;

[0016] Figure 2 A schematic diagram of parameters of the SiO2 diaphragm and companion wafer during the etching process of the formal product provided by the embodiment of the present invention. DETAILED DESCRIPTION

[0017] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0018] like Figure 1 As shown, the present invention adopts a method for monitoring the endpoint of SiO2 wet etching, which specifically includes:

[0019] S1, producing a SiO2 film with obvious color by adjusting the silicon-oxygen ratio, namely, accompanying film 1; the silicon-oxygen ratio of accompanying film 1 is X;

[0020] S2, obtaining the SiO2 film of the formal product, etching the companion film 1 and the SiO2 film of the formal product at the same time, and obtaining an etching rate ratio A of the companion film 1 and the SiO2 film of the formal product;

[0021] S3, obtain the formal product and its SiO2 film thickness d, and produce a SiO2 film with a silicon-oxygen ratio of X and a film thickness of d×Anm, i.e., companion film 2;

[0022] S4, the formal product and the companion film 2 are etched at the same time. When the obvious color (i.e., the companion film 2) falls off, it can be considered that the companion film 2 has reached the etching end point. Since the companion film 2 and the formal product are etched together, the rate ratio is fixed at A. It can be easily known through calculation that the formal product has also reached the etching end point at this time, and the current time is recorded as the etching end point time T0;

[0023] S5. To ensure that SiO2 is completely etched, the final etching time T1=(1+α)·T0 is calculated based on the etching endpoint time T0. When the etching time of the formal product reaches the final etching time T1, the etching of the formal product is completed; wherein α is the proportion of the over-etching amount.

[0024] Preferably, the over-etching amount ratio α is 10%.

[0025] In one embodiment, a brownish-yellow SiO2 film, i.e., companion film 1, is produced by using a silicon-oxygen ratio of 1:1.6. Figure 2 As shown, the SiO2 film of the companion wafer 1 and the formal product are etched at the same time, and the etching rate of the companion wafer 1 is 3.13nm / min, and the etching rate of the SiO2 product wafer is 12.72nm / min, with a ratio of 1:0.25; therefore, for the formal product with a SiO2 film thickness of 40nm, a SiO2 film with a silicon-oxygen ratio of 1:1.6 and a film thickness of 10nm, namely, the companion wafer 2, is etched for the formal product and the companion wafer 2, and the final etching time T1 is calculated. When the etching time of the formal product reaches the final etching time T1, the etching of the formal product is completed.

[0026] When the etching rate of the SiO2 film of the official product is 10-15nm / min and the film thickness is 40nm, the uniformity of the method of calculating the etching time by the etching rate and film thickness is theoretically 50%, while the uniformity of the method of the present invention is 5%.

[0027] The above embodiments further illustrate the purpose, technical solutions and advantages of the present invention in detail. It should be understood that the above embodiments are only preferred implementation modes of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made to the present invention within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for monitoring the endpoint of SiO2 wet etching, characterized in that: include: S1, producing a SiO2 film with obvious color by adjusting the silicon-oxygen ratio, namely, accompanying film 1; the silicon-oxygen ratio of accompanying film 1 is X; S2, obtaining the SiO2 film of the formal product, etching the companion film 1 and the SiO2 film of the formal product at the same time, and obtaining an etching rate ratio A of the companion film 1 and the SiO2 film of the formal product; S3, obtain the formal product and its SiO2 film thickness d, and produce a SiO2 film with a silicon-oxygen ratio of X and a film thickness of d×Anm, i.e., companion film 2; S4, etching the official product and the accompanying film 2 at the same time, when the obvious color of the accompanying film 2 falls off, the current time is recorded as the etching end time T0; S5. Calculate the final etching time T1 according to the etching endpoint time T0. When the etching time of the formal product reaches the final etching time T1, the etching of the formal product is completed.

2. The method for monitoring the endpoint of SiO2 wet etching according to claim 1, characterized in that: The silicon-oxygen ratio X is 1:1.

6.

3. The method for monitoring the endpoint of SiO2 wet etching according to claim 1, characterized in that: The final etching time is calculated according to the etching endpoint time T0 as follows: T1 = (1 + α)·T0; wherein α is the ratio of the over-etching amount.

4. The method for monitoring the endpoint of SiO2 wet etching according to claim 1, characterized in that: The ratio α of the overetching amount is 10%.

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