TW201314810A - A method for monitoring etching process - Google Patents

Abstract

A method for monitoring etching process is used for wet etching by a chemical liquid with specific composition. The invention comprises a gas delivering step to carry an inert gas into the chemical liquid by a gas apparatus and get a first balance pressure value, a etching step to carry out a wafer etching process, a gas pressure monitor step to get a second balance pressure value after wafer etching process, and a calculating step to estimate a variation between gas balance pressure. The invention provides simple, immediate information to monitoring etching ability of the chemical liquid, and therefore reduces whole process cost.

Description

Method of monitoring etching process

The present invention relates to a method of monitoring process etching, and more particularly to a method of monitoring an etching process using batch etching of a chemical liquid.

The use of chemical liquids as wet etching and product cleaning in the technology industry, such as the semiconductor industry, solar energy industry, etc., has been widely used. Referring to Figures 1 and 2, the current method for monitoring the etching process includes a film thickness measuring step 111. An etching step 112, a cleaning measuring step 113, and a calculating step 114, and batch etching of the wafer blank 12 having the film body 121 formed thereon, so that the batch of the wafer blank 12 has a predetermined The film body 121 has a thickness or a film pattern, and can simultaneously monitor the etching ability of the chemical liquid in use.

First, the film thickness measuring step 111 is performed, and the thickness of the film body 121 of the batch of wafer semi-finished products 12 is measured by a measuring machine having a film thickness to obtain a film body 121 of the batch of wafer semi-finished products 12 before etching. Thickness value.

Then, the etching step 112 is performed, and the batch of wafer semi-finished products 12 is immersed in a chemical liquid 13 of a specific composition for etching, and etching is performed for a predetermined time according to the specification of a specific etching process corresponding to the chemical liquid 13.

Then, the cleaning measurement step 113 is performed to clean the wafer semi-finished product 12 through the etching step 112 to remove the chemical liquid 13 and impurities remaining on the batch of the wafer semi-finished product 12, and then measure the film thickness by the measurement. The machine again measures the thickness of the film body 121 of the batch of wafer semi-finished products 12 to obtain the thickness value of the etched film body 121.

After the thickness value of the film body 121 before and after the etching is obtained, the calculation step 114 is performed to calculate the difference between the thickness value of the film body 121 before etching and the thickness value of the film body 121 after etching.

When the difference is still in the range of the film thickness difference specified by the specification of the specific etching process of the chemical liquid 13, it means that the etched batch of the semi-finished wafer 12 meets the process specifications, and the next batch The wafer semi-finished product (not shown) can continue to repeat the etching process; and when the difference does not fall within the range of the etching film thickness defined by the etching process, the batch crystal is etched. The semi-finished product 12 does not meet the process specifications, needs to be scrapped or needs to be repaired, and the etching ability of the chemical liquid 13 is insufficient or the composition is abnormal, and the chemical liquid 13 needs to be updated before the next batch of wafers can be performed. The etching process of the semi-finished product 12.

Because the existing method of controlling the etching process finds that the difference in film thickness is abnormal, the wafer semi-finished product 12 of the batch has also completed the film etching, and must be scrapped or supplemented by an additional etching process as a remedy. Currently, the industry currently uses the same etching process to control the etching ability of the chemical liquid 13 before the batch etching, and then performs the etching of the official batch of the wafer semi-finished product 12 to reduce the scrapping of the online product. The rate and the overall process yield are improved, but this is equivalent to twice the process time to complete the etching of a single batch of wafer semi-finished products 12, which greatly increases the process cost and time. Therefore, how to efficiently monitor the chemical liquid 13 used to maintain the quality of the product, and to take into account the process cost and yield is a research direction.

Accordingly, it is an object of the present invention to provide a method of monitoring an etching process that is simple and readily understandable to the etching ability of a chemical liquid to improve process efficiency.

Thus, the method of the present invention for monitoring an etching process includes a pass gas step, an etching step, a gas pressure detecting step, and a calculation step.

The gas passing step introduces a gas which does not chemically react with a chemical liquid of a specific composition into a chemical liquid of the specific composition in a gas line device, and obtains a first equilibrium pressure corresponding to the chemical liquid.

The etching step immerses at least one wafer semi-finished product to be etched into the chemical liquid for etching, and takes out the wafer semi-finished product after the etching to perform subsequent processes.

The gas pressure detecting step records a gas pressure value that is introduced into the chemical liquid through the gas line device to obtain a second equilibrium pressure corresponding to a change in composition of the chemical liquid after the etching step.

The calculating step is to calculate the difference between the first and second equilibrium pressures and to derive the composition change of the chemical liquid after etching, thereby knowing the etching ability of the chemical liquid.

In addition, the present invention also provides a method of controlling a etch chemistry, comprising a pass gas step, an etch step, a gas pressure detecting step, and a calculating step.

The gas passing step is to pass a gas which does not chemically react with a specific composition of the chemical liquid into the chemical liquid which is accommodated in a chemical tank and is not etched by a gas pipeline device, and reaches a corresponding one. The chemical liquid constitutes a stable first equilibrium pressure.

In the etching step, a predetermined number of wafer semi-finished products are immersed in the chemical liquid for etching, and the wafer semi-finished product is taken out after etching to perform a subsequent process.

The gas pressure detecting step is to measure a gas pressure value that is introduced into the chemical liquid through the gas line device to obtain a second equilibrium pressure corresponding to a composition change of the chemical liquid after the etching step.

The calculating step is to calculate a difference between the first and second equilibrium pressures and compare with a specific gas pressure difference threshold corresponding to the chemical liquid, and when the difference between the first and second equilibrium pressures reaches the critical value, the determination stops. Etching is performed using the chemical liquid.

The invention has the effect of monitoring the change of the equilibrium pressure of the gas while etching, and monitoring the etching ability of the chemical liquid instantaneously and simply by using the equilibrium pressure change of the gas which is introduced into the chemical liquid by the gas pipeline device. To avoid the production problems caused by etching abnormalities, thereby improving the stability and efficiency of the overall process.

The above and other technical contents, features and advantages of the present invention will be apparent from the following detailed description of the preferred embodiments of the invention.

Referring to FIG. 3, a preferred embodiment of the method for monitoring an etching process of the present invention includes a pass gas step 211, an etching step 212, a gas pressure detecting step 213, a calculating step 214, and a replacement etching liquid step 215. The etching ability of the chemical liquid for etching can be accurately monitored while etching, to stably etch the wafer.

Referring to FIG. 4, the gas passing step 211 is first performed to provide a gas line device 5 connected to a chemical tank 3 for etching process, wherein the chemical bath 3 contains a specific composition for the etching process. The liquid 4 is continuously passed through the gas line device 5 to the chemical liquid 4 in the chemical tank 3 to pass a gas 51 which does not chemically react with the chemical liquid 4, for example, the chemical liquid 4 is an acid liquid, and the light is removed. The liquid barrier 51, etc., is a nitrogen gas (Nitrogen), or other inert gas such as an inert gas.

The gas line device 5 includes a gas pressure detecting device 52, and a gas passage 53 connected to the gas pressure detecting device 52 and extending into the chemical tank 3, and the gas line device 5 passes through the gas passage tube 53. When the chemical liquid 4 stored in the chemical tank 3 is introduced into the gas 51 and the pressure is balanced, a first equilibrium pressure can be measured by the gas pressure detector 52, since the structure of the gas pipeline device 5 is not The technical focus of the present invention is, and the device structure is also very diverse and well known in the related art, so the device will not be described again.

The etching step 212 is continued, at least one wafer semi-finished product 6 is immersed in the chemical tank 3, and the wafer semi-finished product 6 is chemically etched by the chemical liquid 4 to take out the wafer semi-finished product 6.

At this time, the gas pressure detecting step 213 is performed synchronously, because during the etching process, the chemical liquid 4 chemically reacts with the material to be etched on the wafer blank 6 to perform a predetermined etching process, thereby making the chemical liquid 4 The composition of the chemical liquid 4 changes, such as the specific gravity of the chemical liquid 4 or the gas solvency, and the equilibrium pressure of the gas 51 introduced by the gas line device 5 is varied. Therefore, the gas pressure detecting step 213 is The pressure detecting unit 52 is used to monitor the pressure value of the gas 51 introduced into the chemical liquid 4 during the etching process and record it as the second equilibrium pressure.

After the first equilibrium pressure and the second equilibrium pressure are obtained, the calculating step 214 can be performed, and the difference between the first equilibrium pressure and the second equilibrium pressure is calculated to obtain a pressure difference value, which can be further estimated by the pressure difference value. The composition of the chemical liquid 4 in the chemical tank 3 is changed to judge whether the chemical liquid 4 can still be etched in the next batch of the wafer semi-finished product 6, or the replacement etching liquid step 215 of the replacement chemical liquid 4 must be performed. It is ensured that the etching result of the next batch of wafer semi-finished products 6 is effective and stable.

Referring to FIG. 5, in more detail, in order to more quickly and accurately determine the relationship between the composition change of the chemical liquid 4 and the pressure value to know whether the chemical etching ability of the chemical liquid 4 is sufficient for the next etching, The basic data establishing step 210 is performed by sequentially immersing a plurality of wafer semi-finished products 6 having formed a specific film body into the chemical liquid 4 in a batch process, and then taking out the film body, and each time Before and after the film etching, the physical properties and chemical properties (such as weight, volume, specific gravity, composition percentage, etc.) of the chemical liquid 4 are recorded, and the gas 51 observed by the gas pressure detecting device 52 is separately recorded. The pressure value of the inlet, the thickness of the film on the semi-finished product 6 of the wafer, and the like, establishes a basic data database corresponding to the etching process using the chemical liquid 4.

By constructing the basic data database, the equilibrium pressure value read by the gas detecting step 213 can be quickly compared with the composition of the chemical liquid 4 represented by the gas detecting step 213, even by pressure. The amount of change is known as whether the chemical liquid 4 has an abnormal phenomenon or the like, and the etching liquid replacement step 215 is performed after the etching ability is weakened, and the new chemical liquid is replaced to ensure the yield of the etching process to achieve perfect etching quality control. .

Referring to FIG. 6, in addition, a preferred embodiment of the method for controlling a etch chemistry of the present invention includes a pass gas step 711, an etch step 712, a gas pressure detecting step 713, a calculating step 714, and a replacement etch. In liquid step 715, the etching ability of the chemical liquid used for etching can be accurately monitored while etching is performed.

Referring to FIG. 4, the gas passing step 711 is a gas 51 which does not chemically react with the etching chemical liquid 4, and the gas passage 53 of the gas piping device 5 is introduced into the chemical tank. 3, and without etching, a new chemical liquid 4, and a first equilibrium pressure is measured by the gas pressure detecting meter 52 connected to the gas passage 53 when the balance is reached.

The etching step 712 is continued, at least one wafer semi-finished product 6 is immersed in the chemical tank 3, and the wafer semi-finished product 6 is batch-etched by the chemical liquid 4, and the wafer semi-finished product is taken out after the predetermined etching time is completed. .

At this time, the gas pressure detecting step 713 is simultaneously performed by the gas pressure detecting meter 52 to monitor the etching at any time, and/or after the etching, in this example, the pressure of the gas 51 that is introduced into the chemical liquid 4 after the etching is completed. A second equilibrium pressure is obtained for the value.

The calculating step 714 is: after the second equilibrium pressure is measured, the difference between the first equilibrium pressure and the second equilibrium pressure is calculated, and the threshold value of a specific gas pressure difference corresponding to the chemical liquid 4 is calculated. For comparison, when the difference between the first and second equilibrium pressures does not reach the defined threshold, the etching step 712, the gas pressure detecting step 713, and the calculating step 714 are repeated to perform another batch. Etching of the wafer semi-finished product 6; when the difference between the first and second equilibrium pressures reaches a defined critical value, the replacement etching liquid step 715 is performed, and the new, unetched chemical liquid 4 is replaced, and then Another batch of wafer semi-finished product 6 is etched.

According to the description of the above two embodiments, the method for monitoring the etching process and the method for controlling the etching of the chemical liquid can not only know the composition change of the chemical liquid at any time during the implementation of the etching step, but also can be reduced. In the prior art, the time and process cost of the etching process and measurement additionally implemented by the control piece enable the monitoring of the chemical liquid to accurately know the etching ability of the chemical liquid while maintaining the chemical liquid in a fast and simple operation. Produce a wafer of semi-finished products of a certain quality.

Through the following experimental examples, an etching process for removing photoresist by a photoresist is described as a more detailed and clear understanding of the present invention.

<Experimental example>

A chemical bath having an inner diameter, a width, a height and a height of 25 cm, 25 cm, and 35 cm, respectively, accommodates an unused photoresist, and the liquid height of the photoresist in the tank is 30 cm. After the gas line device is cleaned, a six-pass wafer semi-finished product coated with a film body having a thickness of 3 μm is applied.

The gas pipe extends into the photoresist and continuously supplies nitrogen gas, so that the liquid level in the gas pipe is kept lower than the liquid level of the photoresist in the chemical tank by 25 centimeters and reaches the pressure balance. The barometric pressure meter knows that the first equilibrium pressure introduced is 2655.8 Pa.

According to the basic data establishing step, the ability of the photoresist in the chemical bath to remove the photoresist after the pressure change reaches 4.2 Pa, the subsequent wafer semi-finished products may have photoresist residue, resulting in wafer yield. Decrease, therefore, the gas pressure difference threshold for this etching process is set to 4.2 Pa.

Then, an etching step is started, and a plurality of photoresist-coated wafer semi-finished products are sequentially placed in a photoresist solution for etching (ie, photoresist removal), and the nitrogen pressure reading value in the gas detector is monitored at any time. And recorded as the second equilibrium pressure.

Referring to FIG. 7, it is known from the experimental data that as the number of etched chips of the batch wafer semi-finished product proceeds, the second equilibrium pressure reading of the nitrogen gas in the gas detector starts to change, and the second equilibrium pressure and the first equilibrium pressure The difference increases with the number of etchings. When the difference between the first and second equilibrium pressures exceeds 4.2 Pa, it is found that the photoresist of the finished batch of semi-finished products will have residual photoresist, which means the etching ability of the photoresist. Not enough, need to replace the new photoresist.

In other words, for different chemical liquid etching processes, as long as the critical value of the gas pressure difference is defined, the nitrogen pressure reading value in the gas detector can be directly determined whether the etching can be continued.

In summary, the method for monitoring the etching process of the present invention provides a quick and easy air pressure monitoring method to ensure that the etching ability of the etching chemical liquid is sufficient and in good condition at any time, thereby improving the stability of the overall etching process and Efficiency, reducing the scrap rate and the number of times of re-production and shortening the process time, and achieving the effect of reducing costs, it is indeed possible to achieve the object of the present invention.

The above is only the preferred embodiment of the present invention, and the scope of the invention is not limited thereto, that is, the simple equivalent changes and modifications made by the scope of the invention and the description of the invention are All remain within the scope of the invention patent.

210. . . Basic data creation steps

211. . . Gas step

212. . . Etching step

213. . . Gas pressure detection step

214. . . calculation steps

215. . . Replace etchant step

3. . . Chemical tank

4. . . Chemical fluid

5. . . Gas pipeline device

51. . . gas

53. . . Air pressure detector

53. . . Gas pipe

6. . . Wafer semi-finished product

711. . . Gas step

712. . . Etching step

713. . . Gas pressure detection step

714. . . calculation steps

715. . . Replace etchant step

1 is a conventional flow chart illustrating a conventional method of controlling an etching process;

2 is a schematic view showing a film thickness measuring step, an etching step, and a cleaning measuring step in the method of controlling the etching process;

3 is a flow chart illustrating a preferred embodiment of the method of monitoring an etching process of the present invention;

4 is a schematic cross-sectional view showing an embodiment of a method for monitoring an etching process of the present invention;

Figure 5 is a flow chart illustrating a basic data establishing step;

Figure 6 is a flow chart illustrating the method of controlling the etching of a chemical liquid of the present invention;

Figure 7 is a biaxial line graph illustrating experimental data of an experimental example.

211. . . Gas step

212. . . Etching step

213. . . Gas pressure detection step

214. . . calculation steps

215. . . Replace etchant step

Claims (11)

A method for monitoring an etching process, comprising: a gas passing step of introducing a gas that does not chemically react with a chemical liquid of a specific composition into the chemical liquid by a gas line device, and obtaining a corresponding chemical liquid a first equilibrium pressure of the composition; an etching step of immersing at least one wafer semi-finished product in the chemical liquid for etching, and removing the semi-finished product of the wafer after etching to perform a subsequent process; a gas pressure detecting step, measuring the The gas line device passes the gas pressure value in the chemical liquid to obtain a second equilibrium pressure corresponding to the change of the composition of the chemical liquid after etching; and a calculating step of calculating the difference between the first and second equilibrium pressures The amount of change in composition of the chemical liquid after etching is obtained. According to the method for monitoring the etching process described in claim 1, the basic data establishing step comprises sequentially immersing a plurality of wafer semi-finished products in the chemical liquid of the specific composition for etching, and etching each time. The change of the gas pressure and the composition change of the chemical liquid are separately recorded before and after, and a basic data database having a gas pressure corresponding to the chemical liquid composition of the etching batch is obtained. The method for monitoring an etching process according to claim 2, wherein the basic data establishing step further measures the thickness of the pre-etched film of the semi-finished wafers before and after each etching, thereby making the basis The data library also has a film body thickness etched by the chemical liquid and a corresponding relationship between the chemical liquid composition and the gas equilibrium pressure. The method for monitoring an etching process according to claim 3, further comprising a step of replacing an etching liquid, wherein the chemical liquid component obtained in the basic data database established by the basic data establishing step is compared to the chemical liquid component obtained in the calculating step Change to determine whether it is necessary to replace the chemical liquid after the etching step that has been performed at least once. A method of monitoring an etching process according to claim 4, wherein the chemical liquid is an acid solution. A method of monitoring an etching process according to claim 4, wherein the chemical liquid is a photoresist, and the film body is composed of a photoresist. A method of monitoring an etching process according to claim 6 wherein the gas to be introduced is selected from the group consisting of an inert gas, nitrogen, and a combination of the foregoing. The method of monitoring an etching process according to claim 7, wherein the gas line device in the gas passing step comprises a gas pressure detecting device, and a gas pressure detecting device is connected to the chemical liquid and extends into the chemical liquid. The gas pipe. A method for controlling etching of a chemical liquid, comprising: a gas passing step of introducing a gas which does not chemically react with a specific composition of chemical liquid into a chemical liquid accommodated in a chemical tank by a gas pipeline device; And obtaining a first equilibrium pressure corresponding to the composition of the chemical liquid; an etching step of immersing at least one wafer semi-finished product in the chemical liquid for etching, and removing the semi-finished product of the wafer after etching to perform a subsequent process; a pressure detecting step of measuring a gas pressure value that is introduced into the chemical liquid through the gas line device to obtain a second equilibrium pressure corresponding to a change in composition of the chemical liquid after etching; and a calculating step of calculating The difference between the first and second equilibrium pressures, when the difference reaches a specific gas pressure difference corresponding to the chemical liquid, stops using the chemical liquid for etching. The method for controlling the etching of the chemical liquid according to claim 9 of the patent application further comprises the step of replacing the etching liquid, and after the chemical liquid stops etching due to reaching the corresponding specific gas pressure difference, the chemical tank is replaced. The etched chemical is a new, unetched chemical. The method of controlling a etch chemistry according to claim 10, wherein the gas line device in the pass gas step comprises a gas pressure detector, and a gas pressure detector is connected to the chemistry The gas in the liquid passes through the tube.