TWI685879B - Method of renewing working solution - Google Patents

Abstract

A method of renewing a working solution including the following steps. A first process is performed on a first batch of wafers is by using a working solution. A first concentration of a specific component in the working solution after the first process is obtained. An estimated concentration increase value of the specific component after performing a second process on a second batch of wafers by using the working solution is estimated. A concentration adjustment value is calculated by subtracting a target concentration of the specific component from the sum of the first concentration and the estimated concentration increase value. An amount of renewing the working solution for the second batch of wafers is determined based on the concentration adjustment value.

Description

Method for updating working solution

The invention relates to a semiconductor manufacturing process, and in particular to a method for updating a working solution.

In the semiconductor factory, based on cost considerations, when the working solution is used to process the wafer, the working solution will not be replaced until a certain number of pieces are processed. However, when the concentration of the specific component in the working solution is too high, defects often occur on the wafer (eg, the specific component precipitates particles formed on the wafer).

Therefore, most of the current semiconductor devices reduce the concentration of specific components in the working solution by shortening the frequency of changing the working solution or updating part of the working solution, so as to avoid defects on the wafer.

However, for different products, the replacement conditions of the working solution will also be different, so the process must be grouped according to product differences. As a result, the number of machines must be increased, resulting in increased process costs.

The invention provides a method for updating a working solution, which can dynamically control the amount of updating of the working solution and can effectively reduce the process cost.

The invention provides a method for updating a working solution, which includes the following steps. The first process is performed on the first batch of wafers using the working solution. The first concentration of the specific component in the working solution after the first process is obtained. Estimate the estimated concentration increase of the specific composition after the second process of the second batch of wafers using the working solution. The concentration adjustment value is calculated by subtracting the target concentration of the specific component from the sum of the first concentration and the estimated concentration increase value. The amount of working solution used for the second batch of wafers is determined according to the concentration adjustment value.

According to an embodiment of the invention, in the above method for updating the working solution, the first process is, for example, a first wet etching process on the first silicon nitride film of the first batch of wafers. The second process is, for example, a second wet etching process on the second silicon nitride film of the second batch of wafers.

According to an embodiment of the invention, in the above method for updating a working solution, the working solution is, for example, phosphoric acid. The specific component is, for example, silicon.

According to an embodiment of the invention, in the above method for updating the working solution, the thickness of the first silicon nitride film removed by the first wet etching process and the photomask corresponding to the first wet etching process can be used The pattern density and the shot area map are used to calculate the concentration increase value of the specific component after the first process. In addition, the thickness of the second silicon nitride film removed by the second wet etching process, the pattern density of the photomask corresponding to the second wet etching process and the exposure area map can be used to calculate the specific after the second process The increase in the estimated concentration of the ingredient.

According to an embodiment of the invention, in the above method for updating the working solution, when the first batch of wafers is the initial batch of wafers, it may further include providing a new working solution.

According to an embodiment of the present invention, in the above method for updating a working solution, it may further include adjusting specific components in the new working solution to an initial concentration.

According to an embodiment of the present invention, in the above method for updating a working solution, a method for adjusting specific components in a new working solution to an initial concentration is, for example, a dummy wet etch process.

According to an embodiment of the present invention, in the above method for updating a working solution, it may further include obtaining an initial concentration of a specific component in the working solution before performing the first process. The first concentration may be the sum of the initial concentration and the concentration increase value of the specific component after the first process.

According to an embodiment of the invention, in the above method for updating a working solution, after the second process is performed, the second concentration of the specific component in the working solution may be equal to the target concentration of the specific component.

According to an embodiment of the invention, in the above method for updating a working solution, the amount of working solution can be controlled by an advanced process control (APC) system.

Based on the above, in the method for updating the working solution proposed by the present invention, the first concentration after the first process is obtained, the estimated concentration increase value after the second process is estimated and the preset value Target density, calculate the density adjustment value. In addition, the amount of working solution used for the second batch of wafers is determined according to the concentration adjustment value. Therefore, the amount of working solution renewal can be dynamically controlled according to the situation of the second batch of wafers. In this way, even in the case of product diversification, there is no need to group the manufacturing process according to product differences in the traditional way, so the number of machines can be reduced and the manufacturing cost can be reduced.

In order to make the above-mentioned features and advantages of the present invention more obvious and understandable, the embodiments are specifically described below in conjunction with the accompanying drawings for detailed description as follows.

FIG. 1 is a flowchart of updating a working solution according to an embodiment of the invention.

Referring to FIG. 1, step S100 may be performed to provide a new working solution. The working solution may be a solution used in various semiconductor manufacturing processes. For example, the working solution may be an etching solution used in a wet etching process. In this embodiment, the working solution is described by taking phosphoric acid as an example, but the invention is not limited thereto.

Then, step S102 may be performed to adjust the specific component in the new working solution to the initial concentration. The method of adjusting specific components in the new working solution to the initial concentration is, for example, a virtual wet etching process.

式(1) For example, the reaction formula of a wet etching process using a phosphoric acid solution (working solution) on the silicon nitride film of the wafer is as shown in the following formula (1).

Formula 1)

Please refer to formula (1), the mechanism of removing silicon nitride film is to use phosphoric acid (H ₃ PO ₄ ) as a catalyst to catalyze silicon nitride (Si ₃ N ₄ ) into silicon oxide (SiO ₂ ) and ammonia (NH ₃ ), where the gaseous ammonia is removed, and the solid silicon oxide is dissolved in phosphoric acid. In this embodiment, the specific component in the phosphoric acid solution (working solution) is, for example, silicon, but the invention is not limited to this.

In the subsequent wet etching process for the initial batch of wafers, when the concentration of silicon (specific composition) in the phosphoric acid solution (working solution) is too low, the phosphoric acid solution has a higher etching rate, so in addition to removing nitrogen In addition to the siliconized film, the silicon oxide film under the silicon nitride film will be removed in large quantities, resulting in excessive wear of the silicon oxide film. In addition, in the subsequent wet etching process for the initial batch of wafers, when the concentration of silicon (specific component) in the phosphoric acid solution (working solution) is too high, the supersaturated silicon concentration will cause silicon oxide on the wafer surface Precipitate and form particles, which will cause adverse effects on the product. Therefore, through the above step S102, the initial concentration of the specific component in the working solution can be controlled in a preferred concentration range to prevent the above-mentioned problems.

Then, step S104 may be performed to obtain the initial concentration of the specific component in the working solution before the first process. In some embodiments, if it is not necessary to adjust the specific components in the new working solution to the initial concentration, step S102 can also be omitted. That is, after step S100 is performed, step S104 may be directly performed.

Next, step S106 is performed to perform the first process on the first batch of wafers using the working solution. In this embodiment, the first process is described by taking the first wet etching process on the first silicon nitride film of the first batch of wafers as an example, but the invention is not limited thereto. In the case where the first batch of wafers is the initial batch of wafers, the method for updating the working solution may include the above step S100 (providing a new working solution), and may optionally include the above step S102 (combining the new working solution Adjust the specific ingredients in the initial concentration). In some embodiments, when the first batch of wafers is the wafer in the batch after the initial batch of wafers, the working solution used in the first batch of wafers may be the previous batch of the first batch of wafers The working solution obtained after the working solution used in the wafer is partially updated.

In addition, step S108 is performed to obtain the first concentration of the specific component in the working solution after the first process. The first concentration may be the sum of the initial concentration and the concentration increase value of the specific component after the first process is performed, as shown in the following formula (2). C1 = C0+ΔC1 (2) In equation (2), C1 represents the first concentration; C0 represents the initial concentration; and ΔC1 represents the concentration increase value.

In addition, the thickness of the first silicon nitride film removed by the first wet etching process, the pattern density of the photomask corresponding to the first wet etching process and the exposure area map can be used to calculate the specific after the first process The increase in the concentration of the ingredient.

For example, the concentration increase value of the specific component after the first process can be calculated by the following formula (3), but the invention is not limited thereto. ΔC1 = N1×P1×S1×SD×R÷(V×HD) Equation (3) In equation (3), ΔC1 represents the concentration increase value; N represents the amount of silicon nitride removal per unit area of the first process; P1 represents the number of wafers in the first batch; S1 represents the number of wafers in the first batch Wafer surface area; SD represents the density of silicon nitride; R represents the silicon content ratio in silicon nitride; V represents the volume of the working solution; HD represents the density of the working solution. N1 can be calculated by using the thickness of the first silicon nitride film removed by the first wet etching process, the pattern density of the photomask corresponding to the first wet etching process, and the exposure area map.

On the other hand, in step S110, the estimated concentration increase value of the specific composition after the second process of the second batch of wafers using the working solution is estimated. The second batch of wafers may be the next batch of wafers of the first batch of wafers. In this embodiment, the second process is described by taking the second wet etching process on the second silicon nitride film of the second batch of wafers as an example, but the invention is not limited thereto. In addition, the first batch of wafers and the second batch of wafers may have the same or different number of wafers. In addition, the first silicon nitride film of the first batch of wafers and the second silicon nitride film of the second batch of wafers may have the same or different thicknesses. In this embodiment, the first silicon nitride film and the second silicon nitride film have different thicknesses as an example for description.

In addition, the thickness of the second silicon nitride film removed by the second wet etching process, the pattern density of the photomask corresponding to the second wet etching process and the exposure area map can be used to calculate the specific after the second process The increase in the estimated concentration of the ingredient.

For example, the estimated concentration increase value of the specific component after the second process can be calculated by the following formula (4), but the invention is not limited thereto. ΔEC2 = N2×P2×S2×SD×R÷(V×HD) (4) In equation (4), ΔEC2 represents the estimated concentration increase; N2 represents the estimated silicon nitride removal per unit area of the second process; P2 represents the number of wafers in the second batch; S2 represents the second batch Wafer surface area in the wafer; SD represents the density of silicon nitride; R represents the silicon content ratio in silicon nitride; V represents the volume of the working solution; HD represents the density of the working solution. N2 can be calculated by using the thickness of the second silicon nitride film removed by the second wet etching process, the pattern density of the photomask corresponding to the second wet etching process, and the exposure area map.

Furthermore, step S112 is performed, the target concentration of the specific component is subtracted from the sum of the first concentration and the estimated concentration increase value, and the concentration adjustment value is calculated as shown in the following formula (5). CM = C1+ΔEC2-CT (5) In equation (5), CM represents the concentration adjustment value; C1 represents the first concentration; ΔEC2 represents the estimated concentration increase value; CT represents the target concentration.

In addition, the target concentration may be set to a concentration that does not generate process defects after the second process is performed on the second batch of wafers using the working solution. For example, the target concentration can be set as follows: after the second wet etching process is performed on the second silicon nitride film of the second batch of wafers, it will not cause excessive wear of the silicon oxide film and will not cause the silicon concentration due to oversaturation The concentration of precipitated particles.

Next, step S114 is performed to determine the amount of refreshing of the working solution for the second batch of wafers based on the concentration adjustment value. The amount of working solution renewal refers to the amount of replacing the old working solution in the working tank with a new working solution. In this way, the logic of the feedforward control (step S108) and the feedback control (step S110) can be used to calculate the optimal process parameters of the second batch of wafers (ie, the amount of working solution update for the second batch of wafers) ). In this way, after the second process is performed, the second concentration of the specific component in the working solution may be approximately equal to the target concentration of the specific component. In addition, the amount of working solution renewal can be controlled by an advanced process control (APC) system.

Based on the above embodiment, it can be known that in the above method for updating the working solution, the obtained first concentration after performing the first process, the estimated increase in estimated concentration after performing the second process, and the preset target Concentration, calculate the concentration adjustment value. In addition, the amount of working solution used for the second batch of wafers is determined according to the concentration adjustment value. Therefore, the amount of working solution renewal can be dynamically controlled according to the situation of the second batch of wafers. In this way, even in the case of product diversification (for example, the first silicon nitride film of the first batch of wafers and the second silicon nitride film of the second batch of wafers have different thicknesses), there is no need to Traditional methods group processes according to product differences, so the number of machines can be reduced and process costs can be reduced.

In summary, the working solution updating method of the above embodiment can use the logic of feedforward control and feedback control to calculate the optimal process parameters of the next batch of wafers, so the amount of working solution update can be dynamically controlled and can be effective To reduce process costs.

Although the present invention has been disclosed as above with examples, it is not intended to limit the present invention. Any person with ordinary knowledge in the technical field can make some changes and modifications without departing from the spirit and scope of the present invention. The scope of protection of the present invention shall be subject to the scope defined in the appended patent application.

S100, S102, S104, S106, S108, S110, S112, S114

FIG. 1 is a flowchart of updating a working solution according to an embodiment of the invention.

S100, S102, S104, S106, S108, S110, S112, S114

Claims (10)

A method for updating working solution, including: Use the working solution to perform the first process on the first batch of wafers; Obtaining a first concentration of a specific component in the working solution after performing the first process; Estimate the estimated concentration increase value of the specific component after the second process of the second batch of wafers using the working solution; Calculating the concentration adjustment value by subtracting the target concentration of the specific component from the sum of the first concentration and the estimated concentration increase value; and The refreshing amount of the working solution for the second batch of wafers is determined according to the concentration adjustment value. The method for updating a working solution as described in item 1 of the patent application scope, wherein the first process includes performing a first wet etching process on the first silicon nitride film of the first batch of wafers, and the second The process includes performing a second wet etching process on the second silicon nitride film of the second batch of wafers. The method for updating a working solution as described in item 2 of the patent application scope, wherein the working solution includes phosphoric acid, and the specific component includes silicon. The method for updating the working solution as described in item 2 of the patent application scope, in which Using the thickness of the first silicon nitride film removed by the first wet etching process, the pattern density of the photomask corresponding to the first wet etching process and the exposure area map, calculate An increase in the concentration of the specific ingredient after a process, and Using the thickness of the second silicon nitride film removed by the second wet etching process, the pattern density of the photomask corresponding to the second wet etching process and the exposure area map, calculate The estimated concentration increase value of the specific component after the second process. The method for updating the working solution as described in item 2 of the patent application scope, in the case where the first batch of wafers is the initial batch of wafers, further includes: Provide the new working solution. The method for updating the working solution as described in item 5 of the patent application scope further includes: Adjust the specific component in the new working solution to the initial concentration. The method for updating a working solution as described in item 6 of the patent application scope, wherein the method for adjusting the specific component in the new working solution to the initial concentration includes performing a virtual wet etching process. The method for updating the working solution as described in item 1 of the patent application scope further includes: Obtaining an initial concentration of the specific component in the working solution before performing the first process, wherein the first concentration is an increase in the initial concentration and the concentration of the specific component after performing the first process The sum of the values. The method for updating a working solution as described in item 1 of the patent application scope, wherein after performing the second process, the second concentration of the specific component in the working solution is equal to the target concentration of the specific component . The method for updating a working solution as described in item 1 of the patent application range, wherein the amount of the working solution is updated by an advanced process control system.

Images