Wafer etching method
By increasing the chuck speed and adjusting the nozzle acceleration during the wafer etching process, combining nitrogen blow-drying and the second HF cleaning, the common defects after the wafer back etching are solved, and the electrical performance and shipment rate of the device are improved.
Patent Information
- Application Number
- CN202311567859.6
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2023-11-22
- Publication Date
- 2025-05-23
AI Technical Summary
In the prior art, after the wafer back etching and cleaning process, various defects often exist, resulting in a degradation in the electrical performance of the final device or a lower yield.
By setting the rotation speed of the chuck to be greater than a threshold rotation speed, the centrifugal force applied to the corrosive bubbles is increased, thereby removing the corrosive bubbles on the wafer surface. Meanwhile, the moving acceleration of the etching liquid nozzle is adjusted to a quadratic curve acceleration, and the wafer is blown dry by nitrogen and a second HF cleaning is performed in the first cleaning chamber to remove defects formed by acid mist corrosion.
Without affecting the etching rate and uniformity, bubble corrosion caused by the reaction process is minimized, the number of defects on the final wafer surface is reduced, and the electrical performance and shipment rate of the device are improved.
Smart Images
Figure CN120033075A_ABST
Abstract
Description
Technical Field
[0001] The invention belongs to the field of semiconductor integrated circuit design and manufacture, and in particular relates to a wafer etching method. Background Art
[0002] Some existing semiconductor products require polishing and mirroring of the back of the wafer, such as IGBT products. IGBT (Insulated Gate Bipolar Transistor) is a composite fully controlled voltage-driven power semiconductor device composed of BJT and MOSFET, which has the advantages of high input impedance of MOSFET and low on-state voltage drop of power transistor (GTR), i.e. bipolar junction transistor with high voltage and high current resistance. It is very suitable for use in converter systems with DC voltage of 600V and above, such as AC motors, inverters, switching power supplies, lighting circuits, traction drives and other fields.
[0003] The above-mentioned semiconductor products, such as IGBT products, have a mirror surface on the back side of the wafer after back etching and cleaning. If there are defects on the back side of the wafer, it will lead to poor electrical parameters, reduce shipment rate and increase cost.
[0004] However, in the prior art, after the wafer backside etching and cleaning process, various defects often exist on the backside of the wafer, resulting in a degradation of the electrical performance of the final device or a low yield.
[0005] It should be noted that the above introduction to the technical background is only for the convenience of providing a clear and complete description of the technical solutions of the present application and facilitating the understanding of those skilled in the art. It cannot be considered that the above technical solutions are well known to those skilled in the art simply because they are described in the background technology section of the present application. Summary of the invention
[0006] In view of the above-mentioned shortcomings of the prior art, an object of the present invention is to provide a wafer etching method for solving the problem that various defects often exist on the back side of the wafer after the wafer back side etching and cleaning process in the prior art.
[0007] To achieve the above-mentioned purpose and other related purposes, the present invention provides a wafer etching method, which includes: fixing a wafer on a chuck of an etching chamber; rotating the wafer through the chuck and inputting an acidic etching solution to the surface of the wafer, wherein the acidic etching solution reacts with the wafer to generate gas, and the gas causes the acidic etching solution to form corrosive bubbles on the surface of the wafer; setting the rotation speed of the chuck to be greater than a threshold rotation speed to remove the corrosive bubbles on the surface of the wafer, wherein the threshold rotation speed is the minimum rotation speed required for the bubbles on the surface of the wafer to move toward the edge of the wafer and detach from the wafer due to centrifugal force.
[0008] Optionally, the threshold speed is 700 rpm to 800 rpm.
[0009] Optionally, an acidic etching liquid is input into the wafer surface through a nozzle. In the acceleration area of the nozzle, the acceleration of the nozzle moving from the side of the wafer toward the center of the wafer is 2 to 4 mm / s2, and the acceleration of the nozzle moving from the center of the wafer toward the side of the wafer is -2 to -4 mm / s2. The distance between the side of the wafer and the center of the wafer is 0.45r to 0.55r, where r is the radius of the wafer.
[0010] Optionally, the acceleration of the nozzle decreases as the distance between the nozzle and the center of the wafer decreases, and / or the movement acceleration of the nozzle is a quadratic curve acceleration.
[0011] Optionally, the nozzle changes to constant speed motion when it is a specific distance from the center of the wafer, and the distance of the specific distance from the center of the wafer is less than 0.35r, where r is the radius of the wafer.
[0012] Optionally, the acidic etching solution comprises H 2 SO 4 , HNO 3 , HF and H 3 PO 4 , where H 2 SO 4 The volume content of HNO is 8% to 12%. 3 The volume content of HF is 35-45%, the volume content of H 3 PO 4 The volume content is 15-25%.
[0013] Optionally, the reaction between the acidic etching solution and the wafer includes an oxidation reaction and a dissolution reaction, wherein the oxidation reaction includes one or more of the following reactions: Si+4HNO 3 →SiO 2 +4NO 2 +2H 2 O; 3Si+4HNO 3 →3SiO 2 +4NO+2H 2 O; the dissolution reaction includes one or more of the following reactions: SiO 2 +6HF→H 2 SiF 6 +2H 2 O; SiO 2 +4HF→SiF 4 ↑+2H 2 O;SiF 4 +2HF→H 2 [SiF 6]; The gases generated by the reaction between the acidic etching solution and the wafer include NO 2 and NO.
[0014] Optionally, after etching the wafer with the acid etching solution, the method further includes the steps of: cleaning the wafer with HF in the first cleaning chamber; and cleaning the wafer with deionized water in the second cleaning chamber.
[0015] Optionally, the first cleaning chamber is disposed below the etching chamber, and the second cleaning chamber is disposed above the etching chamber.
[0016] Optionally, after the wafer is cleaned with deionized water, the steps further include: blowing the wafer dry with nitrogen; and cleaning the wafer a second time with HF in the first cleaning chamber to remove defects caused by acid mist that falls from the etching chamber to the first cleaning chamber and corrodes the wafer.
[0017] As described above, the wafer etching method of the present invention has the following beneficial effects:
[0018] The present invention sets the rotation speed of the chuck to be greater than a threshold rotation speed. Without affecting the etching rate and etching uniformity, the rotation speed is increased to increase the centrifugal force on the corrosive bubbles, thereby removing the corrosive bubbles on the surface of the wafer and minimizing bubble corrosion caused by the corrosive bubbles generated during the reaction process.
[0019] The present invention also adjusts the moving acceleration of the etching liquid nozzle, and changes the moving acceleration of the nozzle into a quadratic curve acceleration, which can better reduce the impact of the etching liquid touching the wafer and the etching liquid film layer formed previously, thereby reducing the etching liquid turbulence and corrosive bubbles generated by the impact.
[0020] The present invention also dries the wafer with nitrogen and cleans the wafer for a second time with HF in the first cleaning chamber to remove defects formed by acid mist corroding the wafer from the etching chamber to the first cleaning chamber, thereby greatly reducing the number of defects on the final wafer surface. BRIEF DESCRIPTION OF THE DRAWINGS
[0021] The included drawings are used to provide a further understanding of the embodiments of the present application, which constitute a part of the specification, are used to illustrate the implementation of the present application, and together with the text description, explain the principles of the present application. Obviously, the drawings described below are only some embodiments of the present application.
[0022] Figure 1 Schematic diagram showing the principle of corrosive bubbles corroding the wafer surface.
[0023] Figure 2 to Figure 10 Shown is a schematic structural diagram of each step of a wafer etching method according to an embodiment of the present invention.
[0024] Component number description
[0025] 101, 201 Wafer
[0026] 102, 203 Corrosive bubbles
[0027] 103 Ring defect
[0028] 202 Oxide layer
[0029] 204 Nozzle
[0030] 205 Turbulence
[0031] 1. The first cavity structure
[0032] 2 Second cavity structure
[0033] 301 Etching Chamber
[0034] 302 First cleaning chamber
[0035] 303 Second cleaning chamber DETAILED DESCRIPTION
[0036] The following describes the embodiments of the present invention through specific examples, and those skilled in the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and the details in this specification can also be modified or changed in various ways based on different viewpoints and applications without departing from the spirit of the present invention.
[0037] It should be emphasized that the term “include / comprises” when used herein refers to the presence of features, integers, steps or components, but does not exclude the presence or addition of one or more other features, integers, steps or components.
[0038] Features described and / or illustrated with respect to one embodiment may be used in the same or similar manner in one or more other embodiments, combined with features in other embodiments, or substituted for features in other embodiments.
[0039] For example, when describing the embodiments of the present invention in detail, for the sake of convenience, the cross-sectional view showing the device structure will not be partially enlarged according to the general scale, and the schematic view is only an example, which should not limit the scope of protection of the present invention. In addition, in actual production, the three-dimensional space dimensions of length, width and depth should be included.
[0040] For ease of description, spatially relative terms such as "under", "below", "below", "below", "above", "on", etc. may be used herein to describe the relationship of one element or feature shown in the drawings to other elements or features. It will be understood that these spatially relative terms are intended to encompass other orientations of the device in use or operation in addition to the orientation depicted in the drawings. In addition, when a layer is referred to as being "between" two layers, it can be the only layer between the two layers, or one or more intervening layers may also be present.
[0041] In the context of the present application, a structure in which a first feature is described as being "above" a second feature may include embodiments in which the first and second features are formed in direct contact, and may also include embodiments in which additional features are formed between the first and second features, such that the first and second features may not be in direct contact.
[0042] It should be noted that the illustrations provided in this embodiment are only used to illustrate the basic concept of the present invention in a schematic manner, and therefore the illustrations only show components related to the present invention rather than being drawn according to the number, shape and size of components in actual implementation. In actual implementation, the type, quantity and proportion of each component may be changed arbitrarily, and the component layout may also be more complicated.
[0043] like Figure 1 As shown, the SPIN-D process is mainly used for thinning and mirroring the back side of the wafer 101, removing the surface stress damage layer after mechanical grinding, and generating reaction gas during the reaction process. When the gas is between the etching solution and the wafer 101, corrosive bubbles 102 are formed, resulting in defects on the back side of the wafer. The present invention has found that the defects of the wafer 101 formed by the corrosive bubbles 102 are usually annular depressions 103, and the thickness inside and outside the annular ring is the same, and no corrosion actually occurs, which confirms that these annular defects 103 of the wafer are actually corrosion defects caused by the corrosive bubbles staying on the wafer.
[0044] Based on the above problems, Figure 2 to Figure 10 As shown, this embodiment provides a wafer etching method, and the wafer etching method includes the following steps:
[0045] like Figure 2 As shown, firstly, step 1) is performed to fix the wafer 201 on the chuck of the etching chamber 301 .
[0046] The wafer 201 may be doped or undoped, and the material of the wafer 201 may be, for example, silicon, silicon germanium, silicon carbide, etc., but is not limited to the examples listed here.
[0047] The wafer 201 has a first surface and a second surface relative to each other. The first surface of the wafer 201 may be pre-formed with a device structure, such as PMOS, NMOS, CMOS integrated circuit, IGBT, VDMOS, etc., and is not limited to the examples listed above. In one implementation, an IGBT device is formed on the first surface of the wafer 201, and the collector of the IGBT device needs to be led out on the second surface of the wafer 201. After the IGBT device is formed on the first surface of the wafer 201, the second surface of the wafer 201 is thinned, such as by using a chemical mechanical polishing process to thin the second surface of the wafer 201. Since there may be a damaged layer on the back of the wafer 201 after thinning, the second surface of the wafer 201 is etched and cleaned in this embodiment to form a mirror surface, which is conducive to the formation of subsequent structures such as electrodes. In this embodiment, the wafer 201 can be fixed on the chuck of the etching chamber 301 by means of a pin, etc. At this time, the back of the wafer 201 is placed upward, and the front of the wafer 201 can be protected by a protective layer to avoid damage to the device structure on the front.
[0048] like Figures 3 to 10 As shown, step 2 is then performed, wherein the wafer 201 is rotated by the chuck, and an acidic etching solution is inputted to the surface of the wafer 201. The acidic etching solution reacts with the wafer 201 to generate gas, and the gas causes the acidic etching solution to form corrosive bubbles 203 on the surface of the wafer 201; the rotation speed of the chuck is set to be greater than a threshold rotation speed to remove the corrosive bubbles 203 on the surface of the wafer 201, wherein the threshold rotation speed is the minimum rotation speed required to make the bubbles on the surface of the wafer 201 move toward the edge of the wafer 201 due to centrifugal force and detach from the wafer 201.
[0049] In one embodiment, the acidic etching solution comprises H 2 SO 4 , HNO 3 , HF and H 3 PO 4 , where H 2 SO 4 The volume content of HNO is 8% to 12%. 3 The volume content of HF is 35-45%, the volume content of H 3 PO 4 The volume content is 15-25%.
[0050] In one embodiment, the reaction between the acidic etching solution and the wafer 201 includes an oxidation reaction to form an oxide layer 202 (eg, Figure 3 ) and dissolution reaction to remove the oxide layer 202 (as shown Figure 4 As shown), wherein: the oxidation reaction includes one or more of the following reactions:
[0051] Si+4HNO3 →SiO 2 +4NO 2 +2H 2 O;
[0052] 3Si+4HNO 3 →3SiO 2 +4NO+2H 2 O;
[0053] Dissolution reactions include one or more of the following reactions:
[0054] SiO 2 +6HF→H 2 SiF 6 +2H 2 O;
[0055] SiO 2 +4HF→SiF 4 ↑+2H 2 O;
[0056] SiF 4 +2HF→H 2 [SiF 6 ];
[0057] In the above reaction, the gases generated by the reaction between the acidic etching solution and the wafer 201 include NO 2 When the above gases are located between the acidic etching solution and the wafer 201, corrosive bubbles 203 are formed. Figure 5 shown.
[0058] In one embodiment, when the acidic etching solution is input to the surface of the wafer 201 through the nozzle 204, if the acceleration of the nozzle 204 is too large (the speed curve of the nozzle 204 is as shown in FIG. Figure 7 As shown in FIG. 2 , the impact between the etching liquid touching the wafer 201 and the previously formed etching liquid film layer is too large to form turbulence 205 on the surface of the wafer 201, such as Figure 8 As shown, the impact of the turbulence 205 will also form corrosive bubbles 203 on the surface of the wafer 201. Therefore, in this embodiment, when the acid etching solution is input to the surface of the wafer 201 through the nozzle 204, the acceleration of the nozzle 204 is set to decrease as the distance between the nozzle 204 and the center of the wafer 201 decreases, and / or the movement acceleration of the nozzle 204 can be changed to a quadratic curve acceleration. Specifically, the movement acceleration of the nozzle 204 can be changed to a quadratic curve acceleration or a quadratic curve acceleration close to the acceleration of the quadratic curve by adding multiple buffer points in the acceleration curve, such as Fig. 9As shown, the impact of the etching liquid touching the wafer 201 and the previously formed etching liquid film layer can be better reduced, thereby reducing the etching liquid turbulence 205 and the corrosive bubbles 203 generated by the impact. In a specific example, in the acceleration area of the nozzle, the acceleration of the nozzle 204 moving from the side of the wafer 201 to the center of the wafer 201 is 2 to 4 mm / s2, the acceleration of the nozzle 204 moving from the center of the wafer 201 to the side of the wafer 201 is -2 to -4 mm / s2, and the distance between the side of the wafer 201 and the center of the wafer 201 is 0.45r to 0.55r, where r is the radius of the wafer 201.
[0059] In addition, in one embodiment, the nozzle 204 changes to uniform motion when it is a specific distance from the center of the wafer 201. The speed of the uniform motion may be in the range of 30 mm / s to 50 mm / s, and in a preferred example, 40 mm / s. The specific distance may be less than 0.35r from the center of the wafer 201, where r is the radius of the wafer 201. The speed curve of the nozzle in this embodiment is as follows: Fig. 9 shown.
[0060] In one embodiment, the rotation speed of the chuck is set to be greater than a threshold rotation speed, and the threshold rotation speed is preferably 700 rpm to 800 rpm. In this rotation speed range, the centrifugal force exerted on the corrosive bubbles 203 is increased by increasing the rotation speed without affecting the etching rate and etching uniformity, thereby removing the corrosive bubbles 203 on the surface of the wafer 201 and minimizing the bubble corrosion caused by the corrosive bubbles 203 generated during the reaction process. The path of bubble removal is as follows: Figure 5-6 shown.
[0061] In one embodiment, after etching the wafer 201 with an acidic etching solution, the steps further include: cleaning the wafer 201 with HF in the first cleaning chamber 302; and cleaning the wafer 201 with deionized water in the second cleaning chamber 303. In one embodiment, the cleaning device includes a first chamber structure 1 and a second chamber structure 2, wherein the first cleaning chamber 302 of the first chamber structure 1 is disposed above the etching chamber 301, and the second cleaning chamber 303 is disposed above the first cleaning chamber 302, and the first cleaning chamber 302 of the second chamber structure 2 is disposed below the etching chamber 301, and the second cleaning chamber 303 is disposed above the etching chamber 301. Fig.10As shown. For the second cavity structure 2 having the above-mentioned structure, the acid mist easily falls from the etching cavity 301 to the first cleaning cavity 302, thereby corroding the wafer 201 and forming defects. Therefore, in this embodiment, after the wafer 201 is cleaned with deionized water, the steps are also included: drying the wafer 201 with nitrogen; cleaning the wafer 201 for the second time with HF in the first cleaning cavity 302 to remove the defects formed by the acid mist that falls from the etching cavity 301 to the first cleaning cavity 302 and corroding the wafer 201. In this embodiment, the wafer 201 is dried with nitrogen and the wafer 201 is cleaned for the second time with HF in the first cleaning cavity 302 to remove the defects formed by the acid mist that falls from the etching cavity 301 to the first cleaning cavity 302 and corrodes the wafer 201, thereby greatly reducing the number of defects on the surface of the final wafer 201. At the same time, drying the wafer 201 with nitrogen first can ensure the concentration accuracy of HF on the surface of the wafer 201, thereby improving the cleaning quality of the second cleaning of the wafer 201 with HF.
[0062] As described above, the wafer etching method of the present invention has the following beneficial effects:
[0063] The present invention sets the rotation speed of the chuck to be greater than a threshold rotation speed. Without affecting the etching rate and etching uniformity, the rotation speed is increased to increase the centrifugal force on the corrosive bubbles 203, thereby removing the corrosive bubbles 203 on the surface of the wafer and minimizing bubble corrosion caused by the corrosive bubbles 203 generated during the reaction process.
[0064] The present invention also adjusts the moving acceleration of the etching liquid nozzle 204, and changes the moving acceleration of the nozzle 204 into a quadratic curve acceleration, which can better reduce the impact of the etching liquid touching the wafer and the etching liquid film layer formed previously, thereby reducing the etching liquid turbulence 205 and the corrosive bubbles 203 generated by the impact.
[0065] The present invention also dries the wafer with nitrogen and cleans the wafer a second time with HF in the first cleaning chamber 302 to remove defects caused by acid mist corroding the wafer from the etching chamber 301 to the first cleaning chamber 302, thereby greatly reducing the number of defects on the final wafer surface.
[0066] Therefore, the present invention effectively overcomes various shortcomings in the prior art and has high industrial utilization value.
[0067] The above embodiments are merely illustrative of the principles and effects of the present invention, and are not intended to limit the present invention. Anyone familiar with the art may modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by a person of ordinary skill in the art without departing from the spirit and technical concept disclosed by the present invention shall still be covered by the claims of the present invention.
Claims
1. A wafer etching method, It is characterized in that The etching method comprises: Fixing the wafer on a chuck of the etching chamber; The wafer is rotated by the chuck, and an acidic etching liquid is inputted to the surface of the wafer. The acidic etching liquid reacts with the wafer to generate gas, and the gas causes the acidic etching liquid to form corrosive bubbles on the surface of the wafer. The rotation speed of the chuck is set to be greater than a threshold rotation speed to remove the corrosive bubbles on the surface of the wafer, wherein the threshold rotation speed is the minimum rotation speed required to make the bubbles on the surface of the wafer move toward the edge of the wafer and detach from the wafer due to centrifugal force.
2. The wafer etching method according to claim 1, Features: The threshold speed is 700 rpm to 800 rpm.
3. The wafer etching method according to claim 1, Features: An acidic etching liquid is input into the surface of the wafer through a nozzle. In the acceleration area of the nozzle, the acceleration of the nozzle moving from the side of the wafer toward the center of the wafer is 2 to 4 mm / s2, the acceleration of the nozzle moving from the center of the wafer toward the side of the wafer is -2 to -4 mm / s2, and the distance between the side of the wafer and the center of the wafer is 0.45r to 0.55r, where r is the radius of the wafer.
4. The wafer etching method according to claim 1, Features: The acceleration of the nozzle decreases as the distance between the nozzle and the center of the wafer decreases, and / or the movement acceleration of the nozzle is a quadratic curve acceleration.
5. The wafer etching method according to claim 3, Features: The nozzle changes to constant speed motion when it is a specific distance away from the center of the wafer, and the distance of the specific distance from the center of the wafer is less than 0.35r, where r is the radius of the wafer.
6. The wafer etching method according to claim 1, Features: The acidic etching solution comprises H 2 SO 4 , HNO 3 , HF and H 3 PO 4 , wherein the H in the acidic etching solution 2 SO 4 The volume content of HNO is 8% to 12%. 3 The volume content of HF is 35-45%, the volume content of H 3 PO 4 The volume content is 15-25%.
7. The wafer etching method according to claim 1, Features: The reaction between the acidic etching solution and the wafer includes an oxidation reaction and a dissolution reaction, wherein: Oxidation reactions include one or more of the following reactions: Si+4HNO 3 →SiO 2 +4NO 2 +2H 2 Oh; <h2 style=";text-align:left;direction:ltr">3Si+4HNO<h2 style=";text-align:left;direction:ltr"> 3 <h2 style=";text-align:left;direction:ltr"> →3SiO<h2 style=";text-align:left;direction:ltr"> 2 <h2 style=";text-align:left;direction:ltr"> +4NO+2H<h2 style=";text-align:left;direction:ltr"> 2 <h2 style=";text-align:left;direction:ltr"> O; Dissolution reactions include one or more of the following reactions: SiO 2 +6HF→H 2 SiF 6 +2H 2 O; SiO 2 +4HF→SiF 4 ↑+2H 2 O; SiF 4 +2HF→H 2 [SiF 6 ]; The gas generated by the reaction between the acidic etching solution and the wafer includes NO 2 and NO.
8. The wafer etching method according to claim 1, Features: After etching the wafer with an acidic etching solution, the method further comprises the steps of: Cleaning the wafer by HF in a first cleaning chamber; The wafer is cleaned with deionized water in the second cleaning chamber.
9. The wafer etching method according to claim 8, Features: The first cleaning chamber is disposed below the etching chamber, and the second cleaning chamber is disposed above the etching chamber.
10. The wafer etching method according to claim 9, Features: After the wafer is cleaned with deionized water, the following steps are also included: Blow drying the wafer by nitrogen gas; The wafer is cleaned for the second time in the first cleaning chamber by HF to remove defects formed by acid mist that falls from the etching chamber to the first cleaning chamber and corrodes the wafer.