A method for improving etching rate of wet etching

Abstract

The invention discloses a method for improving the etching rate of wet etching, comprising an etching reaction chamber for etching operation, wherein the etching reaction chamber is connected to an etching liquid feeding mechanism, the etching liquid feeding mechanism is connected to a purified water feeding mechanism, and the purified water feeding mechanism injects purified water into the etching liquid feeding mechanism according to the pH value variation range of the etching liquid in the etching liquid feeding mechanism, so as to ensure that the hydrogen ion concentration and the fluorine ion concentration of the etching liquid in the etching liquid feeding mechanism are stable, thereby ensuring that the hydrogen ion concentration and the fluorine ion concentration of the etching liquid entering the etching reaction chamber are stable, ensuring the etching rate stability of the etching liquid, and improving the problem of increased etching rate of the etching liquid.

Description

Technical Field

[0001] The invention belongs to the technical field of wet etching, and in particular relates to a method for improving the etching rate of wet etching. Background Art

[0002] Buffered Oxide Etchant (BOE), also known as HF buffer or BHF buffer, is a wet etchant used for micro-machining and is widely used in the semiconductor industry for cleaning and etching oxides. BOE is generally made of hydrogen fluoride (HF) and ammonium fluoride (NH4F) mixed with water and surfactants in different proportions. It is mainly used to etch dielectric films in the grooves on the wafer, such as silicon dioxide (SiO2) film or silicon nitride (Si3N4) film; HF is the main etching solution, used to etch dielectric films such as oxides; NH4F is used as a buffer to buffer and control the etching amount. NH4F is used to adjust the concentration of hydrogen ions and fluoride ions in the etching solution to keep a certain etching rate; surfactants increase surface tension and enhance wettability. Taking SiO2 oxide film as an example, the reaction mechanism of BOE and SiO2 oxide film is as follows:

[0003] SiO2+4HF+H2O+→SiF4+3H2O

[0004] SiF4+2HF→H2SiF6

[0005] SiF4+2NH4F→(NH4)2SiF6.

[0006] Compared with hydrogen fluoride etching solution (DHF) composed of hydrogen fluoride and water, BOE has the following advantages:

[0007] (1) More fluoride ions, more stable etching rate;

[0008] (2) Fewer hydrogen ions, weak alkalinity, and less damage to photoresist (PR).

[0009] In the process of wet etching, BOE is generally placed in the etching liquid feeding mechanism before etching begins, and BOE is transported to the etching reaction chamber through the etching liquid feeding mechanism; in order to reduce costs, the BOE reaction liquid after etching the wafer in the etching reaction chamber is generally collected and refluxed to the etching liquid feeding mechanism for recycling. With the increase of the wafer processing volume in the etching reaction chamber, the BOE reaction liquid recycled in the etching liquid feeding mechanism will also increase. In actual use, although the recycling of BOE reaction liquid can reduce costs to a certain extent, with the increase of the wafer processing volume in the etching reaction chamber, the etching rate will become higher and higher. If BOE is not replaced in time, there will often be a technical problem that the etching rate gradually increases with the increase of the wafer processing volume, and the etching rate cannot be accurately controlled. In the prior art, in order to control the etching rate, it is necessary to replace new BOE regularly, and the chemical consumption is large; generally, it needs to be replaced once a day, which will cause frequent shutdowns and reduce production efficiency. Summary of the invention

[0010] The object of the present invention is to provide a method for improving the etching rate of wet etching in view of the above problems.

[0011] The present invention studies the problem that the etching rate increases rapidly with the increase of the wafer processing volume in the etching reaction chamber due to the continuous recycling of BOE reaction solution during wet etching, and finds that: since NH4F in the etching reaction chamber of BOE is easily decomposed into ammonia (NH3) and generates HF when heated, NH3 will immediately dissolve in water to generate OH by electrolysis reaction. - , the Si in the wafer will be OH - Corrosion produces H2, which gathers on the wafer surface to hinder etching and form point defects. - The corrosion of Si is increased. At the same time, the electrolysis reaction of NH3 dissolved in water and the oxidation of Si by OH - Water (H2O) is consumed during the etching process. Due to the two factors that NH4F is continuously ionized to generate hydrogen ions and fluoride ions during the etching reaction, and water is continuously consumed during the etching reaction, the concentration of hydrogen ions and fluoride ions in the BOE reaction solution becomes higher and higher. The recycling of the BOE reaction solution leads to higher and higher concentrations of hydrogen ions and fluoride ions in the etching solution in the etching solution feeding mechanism, which increases the etching rate and the rising speed is too fast. As the wafer processing volume increases and the reaction time is prolonged, the concentration of hydrogen ions and fluoride ions in the etching solution becomes higher and higher, and the etching rate rises faster and faster, and the etching rate will become higher and higher. Based on this discovery, the present invention uses the pH value of the etching solution to monitor the concentration of hydrogen ions and fluoride ions in the etching solution, and provides a method for improving the etching rate of wet etching.

[0012] In order to achieve the above object, the present invention adopts the following technical solutions:

[0013] A method for improving the etching rate of wet etching includes an etching reaction chamber for etching operation, wherein the etching reaction chamber is connected to an etching liquid feeding mechanism, wherein the etching liquid feeding mechanism is connected to a purified water feeding mechanism, wherein the purified water feeding mechanism injects purified water into the etching liquid feeding mechanism according to the pH value variation range of the etching liquid in the etching liquid feeding mechanism, thereby ensuring that the concentration of hydrogen ions and the concentration of fluorine ions in the etching liquid in the etching liquid feeding mechanism are stable. Thus, the pH of the etching liquid in the etching liquid feeding mechanism and the etching liquid entering the etching reaction chamber is ensured to be stable within a controllable range, and the concentration of hydrogen ions and the concentration of fluorine ions in the etching liquid in the etching reaction chamber are reduced, and the etching rate is controlled within a controllable range, thereby improving the technical problem that the etching rate gradually increases with the increase in the wafer processing volume.

[0014] The etching liquid feeding mechanism delivers the etching liquid to the etching reaction chamber, and the etching reaction liquid in the etching reaction chamber flows back to the etching liquid feeding mechanism through a reflux pipe after the reaction is completed.

[0015] Furthermore, the purified water supply mechanism injects purified water into the etching solution supply mechanism according to the decrease value of the pH value of the etching solution in the etching solution supply mechanism.

[0016] Furthermore, when the pH value of the etching solution in the etching solution feeding mechanism drops by more than 0.5, the purified water feeding mechanism injects purified water into the etching solution feeding mechanism, and when the pH value of the etching solution in the etching solution feeding mechanism drops by less than 0.5, the purified water feeding mechanism stops injecting purified water into the etching solution feeding mechanism. The hydrogen ion concentration and fluoride ion concentration of the etching solution in the etching solution feeding mechanism are ensured to be stable, thereby ensuring the stability of the hydrogen ion concentration and fluoride ion concentration of the etching solution entering the etching reaction chamber, ensuring the stability of the etching rate of the etching solution, and improving the problem of increased etching rate of the etching solution.

[0017] Furthermore, the etching liquid feeding mechanism includes an etching liquid storage chamber, and the purified water feeding mechanism includes a solenoid valve and a pH meter connected to the etching liquid storage chamber, the solenoid valve and the pH meter are respectively connected to a controller, and the controller is used to control the opening and closing of the solenoid valve. When the solenoid valve is opened, purified water is injected into the etching liquid storage chamber.

[0018] Furthermore, the pH meter is located on a pipeline for the etching solution storage chamber to supply the etching solution to the etching reaction chamber.

[0019] Furthermore, the pH value of the etching solution detected by the pH meter is input to the controller, and the controller compares the pH value of the etching solution detected by the pH meter with the initial pH value of the etching solution; when the comparison result is that the pH value of the etching solution drops by more than 0.5, the controller controls the solenoid valve to open, and purified water is injected into the etching solution storage chamber to dilute the hydrogen ion concentration and fluoride ion concentration in the etching solution storage chamber; when the comparison result is that the pH value of the etching solution drops by less than 0.5, the controller controls the solenoid valve to close, and the purified water feeding mechanism stops injecting purified water into the etching solution storage chamber. The initial pH value of the etching solution is the pH value of the etching solution stored in the etching solution feeding mechanism / etching solution storage chamber before etching begins, that is, before the etching reaction chamber starts etching the wafer.

[0020] Furthermore, the illumination light source in the etching reaction chamber is long-wave light. The commonly used short-wave light energy will accelerate the decomposition of NH4F. Changing to long-wave light and reducing the illumination energy can partially inhibit the decomposition of NH4F and prevent ionization from generating excessive hydrogen ions and fluorine ions.

[0021] Furthermore, the illumination light source in the etching reaction chamber is yellow light with a wavelength of 570nm-590nm.

[0022] Furthermore, the etching solution is a buffered oxide etching solution (BOE), which is composed of water, ammonium fluoride, hydrogen fluoride and a surfactant.

[0023] Furthermore, the weight percentage of ammonium fluoride in the etching solution is 19.7%-20.3%, and the weight percentage of hydrogen fluoride is 3.8%-4.2%.

[0024] The type and amount of the surfactant are not particularly limited in the present invention, and the type and amount of surfactant commonly used in the art are adopted.

[0025] Compared with the prior art, the advantages of the present invention are:

[0026] 1. Add a purified water feeding mechanism and a pH meter, use the pH meter to detect the pH of the etching solution components in the etching solution feeding mechanism, and inject purified water into the etching solution feeding mechanism according to the pH value variation range of the etching solution in the etching solution feeding mechanism through the purified water feeding mechanism, so as to ensure that the hydrogen ion concentration and the fluorine ion concentration of the etching solution in the etching solution feeding mechanism are stable, thereby ensuring that the hydrogen ion concentration and the fluorine ion concentration in the etching solution entering the etching reaction chamber are stable, controlling the etching rate, and improving the problem of increased etching rate.

[0027] 2. The lighting system inside the etching reaction chamber is changed to long-wave light (preferably yellow light) to reduce the light energy, partially inhibit the decomposition of NH4F, prevent the ionization of excessive hydrogen ions and fluorine ions, and further reduce the OH in the etching solution in the etching solution feeding mechanism.- The formation thereby avoids corrosion of Si during wet etching, thereby consuming too much water, causing the etching solution in the etching solution feeding mechanism to increase in hydrogen ion concentration and fluorine ion concentration as the wafer processing volume increases, affecting the etching rate.

[0028] Other advantages, objectives and features of the present invention will be embodied in part through the following description, and in part will be understood by those skilled in the art through study and practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 It is a structural schematic diagram of a device used in the wet etching etching rate improvement method of the present invention.

[0030] Figure 2 It is another structural schematic diagram of the device used in the wet etching etching rate improvement method of the present invention.

[0031] Figure 3 It is a flow chart of the wet etching etching rate improvement method of the present invention.

[0032] Figure 4 This is a graph showing the relationship between the wet etching rate and wafer processing volume before improvement.

[0033] Figure 5 It is a relationship diagram between the etching rate of the wet etching improved by the present invention and the wafer processing amount.

[0034] Figure 6 This is a graph showing the relationship between light of different wavelengths and etching rate.

[0035] Figure 7 This is a graph showing the change in ion concentration over time in the wet etching solution (wafer processing volume is 30) before improvement.

[0036] Figure 8 This is a graph showing the pH value of the etching solution changing with time during wet etching (wafer processing volume is 30) before improvement.

[0037] In the figure: etching reaction chamber 100, etching liquid feeding mechanism 2, purified water feeding mechanism 3, etching liquid storage chamber 4, solenoid valve 5, controller 6, pH meter 7;

[0038] Wafer count (pcs) indicates the number of wafers, and Etched Amount (nm) indicates the etched amount (nanometers).

[0039] Weight percentage indicates weight percentage, Time (hr) indicates time (hours); Other amineion indicates other forms of ammonium ions (relative to NH4 + not easy to decompose). DETAILED DESCRIPTION

[0040] In order to enable those skilled in the art to better understand the solutions of the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings in the embodiments of the present invention.

[0041] The present invention studies the problem that the etching rate increases rapidly with the increase of the wafer processing amount in the etching reaction chamber 100 due to the continuous recycling of BOE reaction solution during the wet etching process. It is found that: since BOE in the etching reaction chamber 100 is easily decomposed into ammonia (NH3) and generates HF when NH4F is heated, NH3 will immediately dissolve in water to generate OH - , the Si in the wafer will be OH - Corrosion produces H2, which gathers on the wafer surface to hinder etching and form point defects. - The corrosion of Si is increased. At the same time, the electrolysis reaction of NH3 dissolved in water and the oxidation of Si by OH - Water (H2O) is consumed in the process of corrosion. Due to the continuous ionization of NH4F to generate hydrogen ions and fluoride ions during the etching reaction and the continuous consumption of water during the etching reaction, the concentration of hydrogen ions and fluoride ions in the BOE reaction solution becomes higher and higher. The recycling of the BOE reaction solution leads to the increasing concentration of hydrogen ions and fluoride ions in the etching solution in the etching solution feeding mechanism 2, which increases the etching rate and the rising speed is too fast. As the wafer processing volume increases and the reaction time is prolonged, the concentration of hydrogen ions and fluoride ions in the etching solution becomes higher and higher, and the etching rate rises faster and faster. The etching rate will become higher and higher, which will lead to the thickness of the oxide film etched in the same time. More and more, affecting the product yield. Taking SiO2 oxide film as an example, the etching rate of SiO2 will increase with the increase of the weight percentage of HF in the etching solution; the etching rate of SiO2 will also increase with the increase of the weight ratio of NH4F to HF in BOE and the increase of temperature. Based on this discovery, the present invention controls the concentration of hydrogen ions and fluorine ions in the etching solution by monitoring the pH value of the etching solution, thereby providing a method for improving the etching rate of wet etching.

[0042] In the embodiment of the present invention, the etching solution adopts BOE, which is composed of water, ammonium fluoride, hydrogen fluoride and surfactant, and commercially available products can be selected. Optionally, the weight percentage of ammonium fluoride in the etching solution is 19.7%-20.3%, and the weight percentage of ammonium fluoride is 3.8%-4.2%. The type and amount of surfactant are not particularly limited in the present invention, and the type and amount of surfactant commonly used in BOE in the field are adopted. Optionally, the surfactant is a non-ionic surfactant or anionic surfactant, such as one or more of alkyl sulfonic acid surfactants, fluoroalkyl carboxylic acid surfactants, fluorinated carboxylic acids or their salts; further, one or more of C4F9O(CF3)COONH4, sodium dodecyl alcohol ether sulfate (AES sodium salt), α-olefin sulfonic acid sodium salt (AOS sodium salt), 6501 surfactant, etc. can be selected. Specifically, the surfactant is 28wt% of AES sodium salt, 30wt% of AOS sodium salt, or 30wt% of 6501, and the amount of the surfactant in the etching solution accounts for 0.8wt%-1.2wt%, and the balance is water. All commercially available products can be used.

[0043] The reaction equation for the thermal decomposition of NH4F in BOE is as follows:

[0044] ①NH4F→NH3+HF

[0045] ②NH3+H2O→NH4 + +OH -

[0046] ③Si+2OH - +H2O→SiO3 2- +2H2

[0047] The applicant found that the factors that affect the decomposition of NH4F include: temperature, light wavelength and reaction time. Among them, the higher the temperature, the easier it is to decompose. The short-wave light energy used in the prior art accelerates the decomposition of NH4F. The larger the wafer processing volume and the longer the reaction time, the more NH3 is decomposed, and the more hydrogen ions and fluoride ions are ionized. In addition, water is consumed during the etching reaction, resulting in higher and higher concentrations of hydrogen ions and fluoride ions, which leads to a faster increase in the etching rate. In the prior art, in order to control the etching rate, it is necessary to replace new BOE regularly. Taking the wafer processing volume of less than 30 per day as an example, the BOE generally needs to be replaced once a day (24 hours). Not only is the chemical consumption large, which increases costs, but it also causes frequent downtime and reduces production efficiency.

[0048] Using the existing technology: wet etching before improvement, during the wet etching process, the BOE reaction liquid continuously flows back to the etching liquid feeding mechanism 2. The BOE reaction liquid includes the product of NH4F decomposition when heated, which will cause the concentration of hydrogen ions and fluorine ions in the etching liquid in the etching liquid feeding mechanism 2 to increase, and the pH value to decrease. Taking the wafer processing capacity of 30 pieces / day as an example, the relationship between the change of the ammonium ion content and other ions in the wet etching solution before improvement with time is analyzed by ion chromatography and metrology. The results are shown in Figure 7 , the pH value of the wet etching solution before improvement was tested with a pH meter at different processing times (the wafer processing volume increased with time), and the results are shown in Figure 8 . Figure 7 and Figure 8 It shows that the pH value of the wet etching solution before improvement decreases with the increase of treatment time, and the weight percentage of ammonium ions decreases significantly with the increase of treatment time. After 24 hours of treatment, the pH value of the etching solution has dropped by more than 0.5, and the weight percentage of ammonium ions is only 50% of the initial value, indicating that the NH4F in BOE decomposes rapidly in the etching reaction chamber, resulting in higher and higher concentrations of hydrogen ions and fluorine ions in the BOE reaction solution, and the pH value decreases; the recycling of the BOE reaction solution leads to higher and higher concentrations of hydrogen ions and fluorine ions in the etching solution in the etching solution feeding mechanism 2, and the pH value decreases. Further increase the wafer processing amount, analyze the relationship between the etching amount and the wafer processing amount, and the results are shown in Figure 4 ; Figure 4 It is shown that the etching amount in the wet etching before improvement (when purified water is not injected into the etching solution feeding mechanism 2 according to the pH value variation range of the etching solution) increases with the increase of the wafer processing amount. When the wafer processing amount exceeds 20, the etching amount increases rapidly with the increase of the wafer processing amount, and the etching rate is linear (R 2 =0.9933, close to 1) and the rising speed is fast. In order to control the etching rate, it is necessary to replace the new BOE in time.

[0049] The method for improving the etching rate of wet etching disclosed by the present invention is combined with Figure 1 As shown, it includes an etching reaction chamber 100 for etching operation, the etching reaction chamber 100 is connected to an etching liquid feeding mechanism 2, the etching liquid feeding mechanism 2 is connected to a purified water feeding mechanism 3, and the purified water feeding mechanism 3 injects purified water into the etching liquid feeding mechanism 2 according to the pH value variation range of the etching liquid in the etching liquid feeding mechanism 2. It is ensured that the concentration of hydrogen ions and the concentration of fluorine ions in the etching liquid in the etching liquid feeding mechanism 2 are stable. Thus, it is ensured that the pH of the etching liquid in the etching liquid feeding mechanism 2 and the etching liquid entering the etching reaction chamber 100 is stable within a controllable range, and the concentration of hydrogen ions and the concentration of fluorine ions of the etching liquid in the etching reaction chamber 100 are reduced, and the etching rate is controlled within a controllable range, thereby improving the technical problem that the etching rate of wet etching gradually increases with the increase of wafer processing volume.

[0050] The etching liquid supply mechanism 2 supplies etching liquid to the etching reaction chamber 100 . After the reaction is completed, the etching reaction liquid in the etching reaction chamber 100 flows back to the etching liquid supply mechanism 2 through the reflux pipe.

[0051] Further, the purified water feeding mechanism 3 injects purified water into the etching solution feeding mechanism 2 according to the pH value drop of the etching solution in the etching solution feeding mechanism 2. Specifically, when the pH value drop of the etching solution in the etching solution feeding mechanism 2 exceeds 0.5, the purified water feeding mechanism 3 injects purified water into the etching solution feeding mechanism 2, and when the pH value drop of the etching solution in the etching solution feeding mechanism 2 is lower than 0.5, the purified water feeding mechanism 3 stops injecting purified water into the etching solution feeding mechanism 2.

[0052] Specifically, in this embodiment, the etching liquid feeding mechanism 2 includes an etching liquid storage chamber 4, and the purified water feeding mechanism 3 includes a solenoid valve 5 and a pH meter 7 connected to the etching liquid storage chamber 4. The solenoid valve 5 and the pH meter 7 are respectively connected to a controller 6, and the controller 6 is used to control the opening and closing of the solenoid valve 5. When the solenoid valve 5 is opened, purified water is injected into the etching liquid storage chamber 4. The pH meter 7 is located on the pipeline of the etching liquid storage chamber 4 to provide the etching liquid to the etching reaction chamber 100.

[0053] like Figure 2 As shown, the purified water supply mechanism 3 includes a purified water tank 3b, which is connected to the etching liquid storage chamber 4 via an electromagnetic valve 5, and the electromagnetic valve 5 is connected to a pH meter 7 via a controller 6. The pH value detected by the pH meter 7 can represent the typical pH value in the etching liquid storage chamber 4.

[0054] Those skilled in the art should understand that the purified water tank 3b can be a high-level tank, so that when the solenoid valve 5 is opened, water can be directly added to the etching liquid storage chamber 4, or the purified water tank 3b can be connected to the solenoid valve 5 through a circulation pump 3a, and the circulation pump 3a provides power for water addition. Figure 2 As shown, the circulation pump 3a is connected to the purified water tank 3b, and the outlet of the circulation pump 3a forms two paths, one path is connected to the solenoid valve 5, and the other path is connected to the top of the purified water tank 3b. The circulation pump 3a is always working. When the solenoid valve 5 is opened, the purified water enters the etching liquid storage chamber 4. When the solenoid valve 5 is closed, the circulation pump 3a provides internal circulation for the purified water.

[0055] The etching liquid storage chamber 4 is connected to the etching reaction chamber 100 through the etching liquid delivery pump 4a, and the etching reaction chamber 100 is connected to the etching liquid storage chamber 4 through the reflux pump 100a. In this way, the etching reaction liquid after the etching reaction chamber 100 etches the wafer will flow back to the etching liquid storage chamber 4 after passing through the reflux pump 100a, forming a cycle.

[0056] Combination Figure 3As shown, the present invention detects the pH value of the etching solution in the etching solution feeding mechanism 2 in real time during the wet etching process; compares the real-time detected pH value of the etching solution in the etching solution feeding mechanism 2 with the initial pH value of the etching solution in the etching solution feeding mechanism 2; when the comparison result shows that the pH value of the etching solution decreases by more than 0.5, the purified water feeding mechanism 3 injects purified water into the etching solution feeding mechanism 2; when the comparison result shows that the pH value of the etching solution decreases by less than 0.5, the purified water feeding mechanism 3 stops injecting purified water into the etching solution feeding mechanism 2.

[0057] Specifically, the pH value of the etching solution detected by the pH meter 7 in real time online is input to the controller 6, and the controller 6 compares the pH value of the etching solution detected by the pH meter 7 with the initial pH value of the etching solution. When the comparison result shows that the pH value of the etching solution decreases by more than 0.5, the controller 6 controls the solenoid valve 5 to open, and the purified water is injected into the etching solution storage chamber 4 to dilute the concentration of hydrogen ions and fluoride ions in the etching solution storage chamber 4. The pH meter 7 continues to detect the pH value of the etching solution in real time online and inputs it to the controller 6. The controller 6 compares the pH value of the etching solution detected by the pH meter 7 with the initial pH value of the etching solution. When the comparison result shows that the pH value of the etching solution decreases by more than 0.5, the controller 6 controls the solenoid valve 5 to open, and the purified water is injected into the etching solution storage chamber 4 to dilute the concentration of hydrogen ions and fluoride ions in the etching solution storage chamber 4. The pH meter 7 continues to detect the pH value of the etching solution in real time online and inputs it to the controller 6. The pH value of the etching solution is compared with the initial pH value of the etching solution. When the comparison result shows that the pH value of the etching solution decreases by less than 0.5, the controller 6 controls the solenoid valve 5 to close, and the purified water feeding mechanism 3 stops injecting purified water into the etching solution storage chamber 4. At this time, the concentrations of hydrogen ions and fluorine ions in the etching solution storage chamber 4 tend to be stable, and the pH of the etching solution in the etching solution storage chamber 4 and the etching solution entering the etching reaction chamber 100 are stable within a controllable range, thereby ensuring that the etching rate is within a controllable range and improving the technical problem that the etching rate gradually increases with the increase in wafer processing volume.

[0058] like Figure 5 As shown, after the purified water is injected into the etching solution supply mechanism 2 according to the pH value variation range of the etching solution, the etching rate decreases and remains in a relatively stable range.

[0059] The improved wet etching method of the present invention is used to gradually increase the wafer processing amount, and the relationship between the etching amount and the wafer processing amount is analyzed. The results show that Figure 5 ; Figure 5 It is shown that the etching amount in the improved wet etching method of the present invention (selecting whether to inject purified water into the etching solution feeding mechanism 2 according to the pH value variation range of the etching solution) does not change much with the increase of the wafer processing amount, and is maintained in the controllable range of 39.56nm-39.88nm. Figure 5 The dashed line after data fitting in the solid line (R 2 =0.0979) shows that there is no linear relationship between the etching amount and the wafer processing amount. The improved wet etching method of the present invention can control the etching rate, does not need to replace the new BOE in a short time, significantly reduces the consumption of chemicals, reduces production costs, avoids frequent shutdowns, and improves industrial production efficiency.

[0060] The illumination light source in the etching reaction chamber 100 is long-wave light. Specifically, the illumination light source in the etching reaction chamber 100 is yellow light with a wavelength of 570nm-590nm. The yellow light can be a commercially available yellow light source, or the light source can be filtered through a yellow filter. Figure 6 As shown in the figure, the relationship between the etching rate and the wavelength of the light source is shown. According to the test, when the middle of the wafer uses short-wave light as the illumination light source, and the periphery of the wafer uses long-wave light as the illumination light source, the thickness of the film etched in the middle of the wafer is greater than the thickness of the film etched around the wafer. Figure 6 The etching amount in the middle of the wafer is 40.2nm-40.4nm, and the etching amount around the wafer is 39.1nm-39.7nm, indicating that the shorter the wavelength of the light source used in the etching process, the higher the etching rate. It can be seen that short-wave light energy can accelerate the decomposition of NH4F. Changing the illumination light source in the etching reaction chamber 100 to long-wave light and reducing the illumination energy can partially inhibit the decomposition of NH4F; in addition, it can further reduce the OH in the etching solution in the etching solution feeding mechanism 2. - The formation avoids corrosion of Si during wet etching, reduces water consumption, improves the problem of increasing hydrogen ion concentration and fluorine ion concentration of the etching solution in the etching solution feeding mechanism 2 as the wafer processing volume increases, and ensures the stability of the etching rate of wet etching.

[0061] The specific embodiments described herein are merely examples of the spirit of the present invention. Those skilled in the art may make various modifications or additions to the specific embodiments described or replace them in similar ways without departing from the spirit of the present invention.

Claims

1. A method for improving the etching rate of wet etching, comprising an etching reaction chamber for etching operation, wherein the etching reaction chamber is connected to an etching liquid feeding mechanism, characterized in that: The etching liquid feeding mechanism is connected to a purified water feeding mechanism, and the purified water feeding mechanism injects purified water into the etching liquid feeding mechanism according to the pH value variation range of the etching liquid in the etching liquid feeding mechanism, so as to ensure that the hydrogen ion concentration and the fluorine ion concentration of the etching liquid in the etching liquid feeding mechanism are stable; The illumination light source in the etching reaction chamber is long-wave light; The illumination light source in the etching reaction chamber is yellow light with a wavelength of 570nm-590nm.

2. The method for improving the wet etching rate according to claim 1, characterized in that: The purified water supply mechanism injects purified water into the etching solution supply mechanism according to the decrease value of the pH value of the etching solution in the etching solution supply mechanism.

3. The wet etching rate improvement method according to claim 2, characterized in that: When the pH value of the etching solution in the etching solution feeding mechanism drops by more than 0.5, the purified water feeding mechanism injects purified water into the etching solution feeding mechanism; when the pH value of the etching solution in the etching solution feeding mechanism drops by less than 0.5, the purified water feeding mechanism stops injecting purified water into the etching solution feeding mechanism.

4. The wet etching rate improvement method according to claim 3, characterized in that: The etching liquid feeding mechanism includes an etching liquid storage chamber, and the purified water feeding mechanism includes a solenoid valve and a pH meter connected to the etching liquid storage chamber. The solenoid valve and the pH meter are respectively connected to a controller, and the controller is used to control the opening and closing of the solenoid valve. When the solenoid valve is opened, purified water is injected into the etching liquid storage chamber.

5. The method for improving the wet etching rate according to claim 4, characterized in that: The pH meter is located on a pipeline for the etching solution storage chamber to supply the etching solution to the etching reaction chamber.

6. The method for improving the wet etching rate according to claim 4, characterized in that: The pH value of the etching solution detected by the pH meter is input to the controller, and the controller compares the pH value of the etching solution detected by the pH meter with the initial pH value of the etching solution; when the comparison result is that the pH value of the etching solution decreases by more than 0.5, the controller controls the solenoid valve to open, and purified water is injected into the etching solution storage chamber to dilute the concentration of hydrogen ions and fluoride ions in the etching solution storage chamber; when the comparison result is that the pH value of the etching solution decreases by less than 0.5, the controller controls the solenoid valve to close, and the purified water feeding mechanism stops injecting purified water into the etching solution storage chamber.

7. The method for improving the wet etching rate according to claim 1, characterized in that: The etching solution consists of water, ammonium fluoride, hydrogen fluoride and a surfactant.

8. The method for improving the wet etching rate according to claim 7, characterized in that: The weight percentage of ammonium fluoride in the etching solution is 19.7%-20.3%, and the weight percentage of hydrogen fluoride is 3.8%-4.2%.

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