Method for improving wax mark abnormity after silicon wafer stripping

Abstract

The invention relates to the technical field of silicon wafer polishing, in particular to a method for improving wax mark abnormity after silicon wafer stripping. According to the method, the target temperature T1 of the ceramic disc entering the attaching station, the waxing amount V of a single silicon wafer and the waxing rotating speed S are cooperatively regulated and controlled, the T1 is set to be remarkably higher than the attaching wax softening temperature and the flowing starting temperature, and the V is reduced and the S is increased in a matched mode, so that a wax layer is in a state of sufficient melting and controllable flowing during attaching, and the attaching efficiency is improved. Therefore, uniform filling is realized between the silicon wafer and the ceramic plate, and a thickness-controlled wax film is formed. According to the method, the contradiction that in the continuous multi-wafer attaching process, due to the fact that the temperature of the ceramic plate drops, a wax layer is insufficient in melting and poor in attachment, and due to the fact that the temperature is increased purely, the wax layer excessively flows, and the flatness is damaged is solved, abnormal wax marks of the peeled ceramic plate can be synchronously eliminated, and the polishing flatness of silicon wafers is remarkably improved; and the quality consistency of continuous attachment is ensured, the production yield is improved, and the wax material consumption is reduced.

Description

Technical Field

[0001] This invention relates to the field of silicon wafer polishing technology, and in particular to a method for improving abnormal wax marks after silicon wafer peeling. Background Technology

[0002] During the fabrication of semiconductor silicon wafers, polishing is required to remove tiny bumps and damaged layers from the surface of the wafer, in order to ensure the uniformity of the wafer thickness and the smoothness of the surface, and to obtain good flatness.

[0003] Before polishing, the back of a semiconductor silicon wafer must be attached (also known as "bonded") to a rigid ceramic disk using a wax layer to provide stable support. The attachment process typically includes the following key steps: First, a solid wax is applied to the back of the silicon wafer; then, the waxed silicon wafer is aligned and pressed against the preheated ceramic disk, allowing the wax to melt and spread evenly between the two interfaces; after cooling and solidification, the wax layer forms a strong bond, facilitating subsequent polishing; after polishing, the silicon wafer is then peeled off the ceramic disk.

[0004] To achieve good adhesion results, existing technologies generally employ a graded heating method for the ceramic disc. For example... Figure 1 As shown, before entering the bonding station, the ceramic disc sequentially passes through a first heating section (110-130℃), a second heating section (120-140℃), and a third heating section (130-160℃) with progressively increasing temperatures. By controlling the temperature of the third heating section, the surface temperature of the ceramic disc is maintained within the target range of 110-130℃ when it enters the bonding section. This temperature setting aims to ensure that the wax layer reaches a fully molten state, thereby ensuring uniform flow and good adhesion to the surface of the ceramic disc.

[0005] However, in actual large-scale continuous production, the above process revealed significant technical problems. Since multiple silicon wafers (e.g., 5) typically need to be continuously mounted on a single ceramic disc, and the mounting of each wafer requires a certain amount of time, the temperature of the ceramic disc drops significantly from the initial target value due to continuous contact with the room temperature environment and the relatively low temperature of the wafers during subsequent wafer mounting. If the temperature drops to only slightly above or even below the softening temperature of the mounting wax used, the wax layer will not melt sufficiently, resulting in a deterioration in its fluidity, ductility, and filling capacity.

[0006] The consequences are as follows: (1) Due to the weakened adhesion between the insufficiently melted wax layer and the ceramic disk surface, a large amount of wax fails to detach with the silicon wafer after polishing and peeling, and instead remains abnormally on the ceramic disk surface, forming obvious wax marks. This not only increases the difficulty and cost of cleaning the ceramic disk, but the residual wax marks may also affect the flatness of subsequent bonding. (2) Uneven filling and poor adhesion of the wax layer during bonding directly lead to a decrease in the support stability of the silicon wafer during the polishing process. After polishing, defects such as excessive flatness or local shallow pits are prone to appear on the surface of the silicon wafer, which seriously affects the product yield.

[0007] To address the aforementioned issues, an optimization approach readily apparent to those skilled in the art is to increase the heating temperature of the ceramic disc. However, this approach introduces a new challenge: if the temperature is too high, especially during the application of the first few silicon wafers, the wax layer becomes excessively fluid due to overheating, resulting in decreased cohesion. This, in turn, leads to poor uniformity in the wax film thickness and may leave more residue on the silicon wafers rather than the ceramic disc during peeling, thus failing to resolve the flatness control problem.

[0008] Therefore, a comprehensive process solution is needed to systematically and coordinately resolve the contradiction between insufficient wax melting caused by the natural drop in temperature of the ceramic disc during continuous multi-piece application and excessive wax flow that may be caused by increasing the temperature. Summary of the Invention

[0009] In view of the shortcomings of the prior art described above, the present invention provides a method to improve the abnormal wax marks after silicon wafer peeling, so as to solve the technical problems of insufficient wax melting and poor adhesion caused by the natural drop in temperature of the ceramic disk during the continuous multi-wafer bonding process, and the problem that simply increasing the temperature will cause excessive wax flow and damage to the flatness.

[0010] The first aspect of this invention provides a method for improving abnormal wax marks after silicon wafer peeling, comprising the following steps:

[0011] (1) The ceramic disc carrying the wax layer is heated so that it reaches the target temperature T1 when it enters the application station; the target temperature T1 is higher than the softening temperature and flow start temperature of the application wax used.

[0012] (2) The wax is applied to the back of the silicon wafer; the amount of wax applied to a single silicon wafer, V, and the waxing speed, S are matched so that at the target temperature T1, the wax layer can be uniformly filled between the silicon wafer and the ceramic disk and form a wax film with controlled thickness.

[0013] (3) At the bonding station, the back of the silicon wafer coated with wax in step (2) is pressed onto the wax layer of the heated ceramic disk.

[0014] In some embodiments of the present invention, the target temperature T1 is 125~135℃.

[0015] In some embodiments of the present invention, the wax coating amount V is 0.7~0.9 mL / piece.

[0016] In some embodiments of the present invention, the waxing rotation speed S is 1300~1700 rpm.

[0017] In some embodiments of the present invention, the softening temperature of the adhesive wax is 60~80°C and the flow start temperature is 70~90°C.

[0018] In some embodiments of the present invention, the ambient temperature of the application station is maintained at T2, and the difference between T2 and T1 is within ±10°C.

[0019] In some embodiments of the present invention, T2 is 125~135℃.

[0020] In some embodiments of the present invention, the heating process of the ceramic disc includes passing it sequentially through a first heating zone, a second heating zone, and a third heating zone with increasing temperatures, wherein the target temperature T1 is achieved by controlling the temperature of the third heating zone.

[0021] In some embodiments of the present invention, the set temperature of the third heating zone is 135~160°C.

[0022] In some embodiments of the present invention, the method is used to continuously attach 4 to 6 silicon wafers, preferably 5, to the same ceramic disk.

[0023] In some embodiments of the present invention, the temperature control method of the third heating zone includes: monitoring the real-time temperature of the ceramic disc in the third heating zone; when the real-time temperature reaches a set upper limit, lifting the ceramic disc away from the heating zone to stop heating; and when the real-time temperature drops to a set lower limit, placing the ceramic disc back into the heating zone to resume heating.

[0024] In some embodiments of the present invention, the waxing rotation speed S is the rotational speed of the waxing head, or the rotational speed of the rotary table carrying the silicon wafer.

[0025] Compared with the prior art, the present invention has the following advantages:

[0026] 1. This invention, by synergistically increasing the ceramic disc temperature T1 and adapting and optimizing the waxing process (reducing the wax amount V and increasing the waxing speed S), ensures that the wax layer is in an ideal state of full melting and controllable flow throughout the entire application process. This fundamentally overcomes the contradiction between "insufficient temperature leading to poor adhesion" and "excessive temperature leading to uncontrolled casting," thereby eliminating abnormal wax marks on the ceramic disc after peeling and significantly improving the surface flatness of the silicon wafer after polishing.

[0027] 2. By increasing and controlling the ambient temperature T2 at the bonding station, this invention effectively slows down the temperature drop of the ceramic disc during continuous operation. Combined with an optimized heating control strategy, it ensures that stable and uniform thermal conditions are provided for multiple silicon wafers (especially the last few) bonded to the same ceramic disc, achieving a high degree of consistency in the overall product quality and greatly improving the reliability and yield of mass production.

[0028] 3. This invention significantly improves the appearance (eliminating defects such as shallow pits) and internal quality (improving flatness) of products while saving production materials by reducing the wax consumption (V) per silicon wafer and increasing coating efficiency. Furthermore, the reduction in wax marks on ceramic discs directly lowers cleaning and maintenance costs and frequency, resulting in considerable economic benefits. Attached Figure Description

[0029] Figure 1 This is a schematic diagram of the structure of a silicon wafer bonding device according to an embodiment of the present invention.

[0030] Figure 2 The images show the surface wax marks on the ceramic disc after peeling and the surface morphology of the silicon wafer after polishing in Embodiment 1 of the present invention; the left image shows the surface state of the ceramic disc after peeling in Embodiment 1; and the right image shows the surface morphology of the silicon wafer after polishing in Embodiment 1.

[0031] Figure 3 The images show the surface wax marks after the ceramic disk was peeled off and the surface morphology of the silicon wafer after polishing, as shown in Embodiment 2 of the present invention. The left image shows the surface state of the ceramic disk after peeling off in Embodiment 2, and the right image shows the surface morphology of the silicon wafer after polishing in Embodiment 2.

[0032] Figure 4 The images show the surface wax marks after the ceramic disk was peeled off and the surface morphology of the silicon wafer after polishing in Embodiment 3 of the present invention; the left image shows the surface state of the ceramic disk after peeling off in Embodiment 3; and the right image shows the surface morphology of the silicon wafer after polishing in Embodiment 3.

[0033] Figure 5 The images show the surface wax marks on the ceramic disc after peeling and the surface morphology of the silicon wafer after polishing in Comparative Example 1 of the present invention; wherein, the left image is the surface state of the ceramic disc after peeling in Comparative Example 1; and the right image is the surface morphology of the silicon wafer after polishing in Comparative Example 1.

[0034] Figure 6 The images show the surface wax marks on the ceramic disk after peeling and the surface morphology of the silicon wafer after polishing in Comparative Example 2 of the present invention; the left image shows the surface state of the ceramic disk after peeling in Comparative Example 2; and the right image shows the surface morphology of the silicon wafer after polishing in Comparative Example 2. Detailed Implementation

[0035] The following specific embodiments further illustrate a method for improving abnormal wax marks after silicon wafer peeling according to the present invention.

[0036] The first aspect of this invention provides a method for improving abnormal wax marks after silicon wafer peeling, with reference to... Figure 1 This includes the following steps:

[0037] (1) The ceramic disc carrying the wax layer is heated so that it reaches the target temperature T1 when it enters the application station; the target temperature T1 is higher than the softening temperature and flow start temperature of the application wax used.

[0038] (2) The wax is applied to the back of the silicon wafer; the amount of wax applied to a single silicon wafer, V, and the waxing speed, S are matched so that at the target temperature T1, the wax layer can be uniformly filled between the silicon wafer and the ceramic disk and form a wax film with controlled thickness.

[0039] (3) At the bonding station, the back of the silicon wafer coated with wax in step (2) is pressed onto the wax layer of the heated ceramic disk.

[0040] The principle of this invention lies in controlling the physical state of the wax layer during the application process to an optimal state that balances good fluidity and moderate cohesion by synergistically regulating three core parameters: the target temperature T1 of the ceramic disc, the amount of wax applied (V), and the waxing rotation speed (S). Specifically, increasing T1 to significantly higher than the softening and flow initiation temperature of the wax ensures that the wax layer is fully melted, achieving uniform filling and firm adhesion at the interface, thereby solving the problem of wax residue. At the same time, decreasing V to reduce the total amount of wax and increasing S to optimize the initial distribution of wax work together to limit the excessive spreading and thickness of the molten wax layer. This allows for the formation of a uniform and controlled wax film even under high-temperature application conditions, ensuring the flatness of the silicon wafer and overcoming the challenges of poor adhesion and flatness degradation.

[0041] The softening temperature and flow initiation temperature of the adhesive wax are its basic physical parameters, which can usually be obtained from the supplier's Technical Specifications (TDS) or determined by conventional thermal analysis methods (such as Differential Scanning Calorimetry (DSC) or Thermomechanical Analysis (TMA). The target temperature T1 can be adjusted accordingly based on the specific parameters of the selected wax, making it higher than the wax's softening temperature and flow initiation temperature.

[0042] In some embodiments of the present invention, the target temperature T1 is 125~135℃, which can be 125~126℃, 126~127℃, 127~128℃, 128~129℃, 129~130℃, 130~131℃, 131~132℃, 132~133℃, 133~134℃, or 134~135℃, preferably 125~130℃.

[0043] In some embodiments of the present invention, the wax coating amount V is 0.7~0.9 mL / piece, which can be 0.7~0.75 mL / piece, 0.75~0.8 mL / piece, 0.8~0.85 mL / piece, or 0.85~0.9 mL / piece, preferably 0.75~0.85 mL / piece, and more preferably 0.8 mL / piece.

[0044] In some embodiments of the present invention, the waxing speed S is 1300~1700 rpm, which can be 1300~1400 rpm, 1400~1500 rpm, 1500~1600 rpm, or 1600~1700 rpm, preferably 1400~1600 rpm, and more preferably 1500 rpm.

[0045] In some embodiments of the present invention, the softening temperature of the adhesive wax is 60~80°C, which can be 60~65°C, 65~70°C, 70~75°C, or 75~80°C, and the flow start temperature is 70~90°C, which can be 70~75°C, 75~80°C, 80~85°C, or 85~90°C.

[0046] In some embodiments of the present invention, the ambient temperature of the application station is maintained at T2, and the difference between T2 and T1 is within ±10℃, which can be 0℃ (i.e., T2 equals T1), ±2℃, ±4℃, ±6℃, ±8℃, or ±10℃.

[0047] In some embodiments of the present invention, T2 is 125~135℃, and can be 125~126℃, 126~127℃, 127~128℃, 128~129℃, 129~130℃, 130~131℃, 131~132℃, 132~133℃, 133~134℃, or 134~135℃.

[0048] In some embodiments of the present invention, the heating process of the ceramic disk includes passing it sequentially through a first heating zone, a second heating zone, and a third heating zone with progressively increasing temperatures. The target temperature T1 is achieved by controlling the temperature of the third heating zone. This gradual heating method precisely and stably heats the ceramic disk to the target temperature T1, minimizing internal thermal stress and temperature unevenness. The first heating zone, serving as a preheating stage, has a relatively mild starting temperature (e.g., 110-130°C). Its main function is not to directly melt the wax layer, but to allow the overall temperature of the ceramic disk, entering from room temperature, to rise gradually, avoiding localized thermal shock or deformation caused by sudden heating, thus preparing for subsequent rapid heating. Subsequently, the ceramic disk enters the second heating zone, where the temperature is further increased (e.g., 120-140°C), and the heating rate accelerates. This stage is a crucial transition period where the main body temperature of the ceramic disk rapidly rises to near the target temperature T1, ensuring that heat is fully and evenly conducted to the interior of the ceramic disk, reducing the temperature difference between its surface and core, and laying the foundation for precise final temperature control in the next stage. Finally, the ceramic disc reaches the third heating zone, which is the core temperature control stage of the entire heating process. The control temperature in this zone is set to be significantly higher than the target temperature T1 (e.g., 135~160℃) to overcome the thermal inertia of the ceramic disc. Through a closed-loop feedback control mechanism (e.g., a cycle of monitoring-lifting-cooling-returning), the ceramic disc is finely temperature-adjusted. This mechanism dynamically compensates for heat loss, ensuring that the surface temperature of the ceramic disc is precisely and stably maintained at the target temperature T1 the instant it leaves the third heating zone and enters the bonding station. It is by controlling the operating parameters of the third heating zone that the ceramic disc can reliably enter the bonding stage in a state higher than the wax softening point and flow initiation point with minimal fluctuations, which is the fundamental prerequisite for ensuring the consistency of subsequent bonding quality.

[0049] In some embodiments of the present invention, the set temperature of the third heating zone is 135~160℃, or it can be 135~140℃, 140~145℃, 145~150℃, 150~155℃, or 155~160℃.

[0050] In some embodiments of the present invention, the method is used to continuously attach 4 to 6 silicon wafers, preferably 5, to the same ceramic disk.

[0051] In some embodiments of the present invention, the temperature control method of the third heating zone includes: monitoring the real-time temperature of the ceramic disc in the third heating zone; when the real-time temperature reaches a set upper limit, lifting the ceramic disc away from the heating zone to stop heating; and when the real-time temperature drops to a set lower limit, placing the ceramic disc back into the heating zone to resume heating. By directly intervening in heat exchange through physical displacement, the lag and overshoot problems in traditional power control are avoided. The instantaneous temperature fluctuation when the ceramic disc leaves (i.e., T1 upon entering the attachment section) can be controlled within a very small range (e.g., ±1~2℃). Regardless of environmental fluctuations or minor changes in heater performance, the system can automatically compensate through feedback loops to ensure long-term consistency of the output temperature.

[0052] In some embodiments of the present invention, the wax coating rotation speed S is the rotational speed of the wax coating head, or the rotational speed of the rotary table supporting the silicon wafer. In some specific embodiments of the present invention, S is defined as the rotational speed of the wax coating head itself. In this configuration, the wax coating head is usually a hollow shaft with a wax outlet at its end. In the rotating state, the molten wax is evenly thrown out from the wax outlet under the action of centrifugal force, forming a fine wax mist or wax droplets, which are then deposited on the back of the stationary or slowly moving silicon wafer. At this time, the rotational speed S directly determines the particle size, initial velocity, and spatial distribution density of the wax droplets, and is a key factor affecting the coating uniformity and initial film thickness. In some other specific embodiments of the present invention, S is defined as the rotational speed of the rotary table that carries and fixes the silicon wafer. In this configuration, the waxing head is usually stationary or only makes simple lateral movements to drop a fixed amount of wax onto the center of the back of the silicon wafer. Subsequently, the high-speed rotating silicon wafer spreads the wax in the center evenly to the outer periphery under the action of strong centrifugal force to form a thin film. At this time, the rotational speed S directly determines the magnitude of the centrifugal force acting on the wax, and thus dominates the final thickness, uniformity and whether splashing occurs in the wax film.

[0053] Before further describing specific embodiments of the present invention, it should be understood that the scope of protection of the present invention is not limited to the specific embodiments described below; it should also be understood that the terminology used in the embodiments of the present invention is for describing specific embodiments and not for limiting the scope of protection of the present invention.

[0054] Unless otherwise defined, all technical and scientific terms used in this invention have the same meaning as commonly understood by one of ordinary skill in the art. In addition to the specific methods, apparatus, and materials used in the embodiments, this invention can be implemented using any prior art methods, apparatus, and materials similar to or equivalent to those described in the embodiments of this invention, based on the knowledge of the prior art possessed by one of ordinary skill in the art and the description of this invention.

[0055] Unless otherwise stated, the experimental methods, detection methods, and preparation methods disclosed in this invention all employ conventional techniques in analytical chemistry and related fields. Unless otherwise stated, all materials and equipment used in this invention are commercially available.

[0056] In the following examples and comparative examples, the softening temperature of the adhesive wax used was 60~80°C and the flow start temperature was 70~90°C.

[0057] In the following embodiments and comparative examples, the key performance indicators involved were evaluated in the following ways:

[0058] (1) Wax mark anomaly rate: After the silicon wafer is peeled from the ceramic disk, the surface of the ceramic disk is inspected visually or with an optical microscope (e.g., 20x magnification). Any area with visible, continuous or dotted wax residue is judged as "wax mark anomaly". The percentage of ceramic disks with wax mark anomalies out of the total number of ceramic disks tested is the wax mark anomaly rate.

[0059] (2) Flatness defect rate: After the silicon wafers are polished, their total thickness variation (TTV) or local flatness (SFQR) is measured using a commercial silicon wafer flatness tester. Silicon wafers whose measured values ​​exceed the product specifications are judged as "flatness defective". The percentage of silicon wafers with flatness defects out of the total number of silicon wafers tested is the flatness defect rate.

[0060] Example 1

[0061] This embodiment of the method for improving abnormal wax marks after silicon wafer peeling includes the following steps:

[0062] (1) Ceramic disc preheating and temperature control: The ceramic disc is loaded onto the conveying mechanism and passes through the three zones of the heating unit in sequence: heating zone 1, heating zone 2, and heating zone 3. Heating zone 1: The temperature of this zone is set at 120℃. Heating zone 2: The temperature of this zone is set at 130℃. Heating zone 3: The temperature of this zone is set at 145℃; this zone adopts closed-loop temperature control: the surface temperature of the ceramic disc is monitored in real time. When it reaches 126℃, the robot lifts it away from the heat source to stop heating. When the temperature drops to 124℃, it is put back into the heat source to resume heating; through cyclic control, the surface temperature of the ceramic disc when it leaves this zone and enters the bonding station is accurately T1=125℃.

[0063] (2) Waxing on the back of silicon wafer: Take a 200mm semiconductor silicon wafer and perform waxing operation at an independent waxing station: Place the silicon wafer with the back facing up on a high-speed rotating table and fix it with vacuum adsorption; set the waxing process parameters: the wax amount V of a single silicon wafer is 0.8 mL; the waxing speed S of the rotating table carrying the silicon wafer is 1500 rpm; start the rotating table, and after the speed stabilizes at 1500 rpm, drip 0.8 mL of molten adhesive wax onto the center of the back of the silicon wafer through the dispensing valve; at a speed of 1500 rpm, the centrifugal force causes the wax liquid to spread evenly to the entire back of the silicon wafer within 1-2 seconds, forming an initial wax film with uniform thickness, submicron level and in-plane deviation of less than 5%.

[0064] (3) Single silicon wafer bonding and pressing: The ceramic disk heated to T1=125℃ in step (1) is transferred to the bonding station, where the ambient temperature T2 is maintained at 125℃; then, the reverse suction head vacuum adsorbs the front side of the silicon wafer that has been coated with wax in step (2); the suction head carries the silicon wafer up, completes a 180° flip and then descends, so that the wax layer on the back of the silicon wafer is aligned with the heated ceramic disk; the suction head presses the back of the silicon wafer onto the surface of the ceramic disk with controllable pressure, maintains the pressure for about 5 seconds, releases the vacuum, removes the suction head, and allows the wax layer to slowly solidify in the heat-preserving environment, thus completing the bonding of a single silicon wafer.

[0065] (4) Repeat steps (2) and (3) to continuously attach a total of 5 silicon wafers onto the same ceramic disk. Due to the good heat preservation of the attachment station (T2=125℃), the surface temperature of the ceramic disk can still be maintained above 122℃ when attaching the 5th silicon wafer, which is higher than the wax flow start temperature, ensuring that the wax layer can still melt well when the last silicon wafer is attached. After the entire disk of silicon wafers is attached and cooled, peeling and polishing are performed.

[0066] The process effect of this embodiment is as follows: Figure 2 As shown in the image, the left image shows the surface condition of the ceramic disk after peeling, which is smooth and has no obvious wax residue; the right image shows the surface morphology of the silicon wafer after polishing, which shows a uniform surface and the shallow pit defects at the edges have basically disappeared.

[0067] Peeling effect: 20 trays (100 silicon wafers in total) were continuously applied and tested. After all silicon wafers were peeled off, the surface of the ceramic tray was smooth and there were no visible wax residues. The wax residue abnormality rate was 2.0%.

[0068] Polishing effect: The silicon wafers after stripping were subjected to standard polishing process. After polishing, the surface morphology of the silicon wafers was inspected and it was found that defects such as shallow pits at the edges had basically disappeared, the overall flatness (TTV) was significantly improved, and the flatness defect rate was reduced to 1.5% (based on the test results of the above 100 silicon wafers).

[0069] Example 2

[0070] This embodiment of the method for improving abnormal wax marks after silicon wafer peeling includes the following steps:

[0071] (1) Ceramic disc preheating and temperature control: The ceramic disc is loaded onto the conveying mechanism and passes through the three zones of the heating unit in sequence: heating zone 1, heating zone 2, and heating zone 3. Heating zone 1: The temperature of this zone is set at 125℃. Heating zone 2: The temperature of this zone is set at 135℃. Heating zone 3: The temperature of this zone is set at 150℃; this zone adopts closed-loop temperature control: the surface temperature of the ceramic disc is monitored in real time. When it reaches 129℃, the robot lifts it away from the heat source to stop heating. When the temperature drops to 127℃, it is put back into the heat source to resume heating; through cyclic control, the surface temperature of the ceramic disc when it leaves this zone and enters the bonding station is accurately T1=128℃.

[0072] (2) Waxing on the back of silicon wafer: Take a 200mm semiconductor silicon wafer and perform waxing operation at an independent waxing station: Place the silicon wafer with the back facing up on a high-speed rotating table and fix it with vacuum adsorption; set the waxing process parameters: the wax amount V of a single silicon wafer is 0.75 mL; the waxing speed S of the rotating table carrying the silicon wafer is 1600 rpm; start the rotating table, and after the speed stabilizes at 1600 rpm, drip 0.75 mL of molten adhesive wax onto the center of the back of the silicon wafer through the dispensing valve; at a speed of 1600 rpm, the centrifugal force causes the wax liquid to spread evenly to the entire back of the silicon wafer in about 1 second, forming an ultra-thin and uniform initial wax film.

[0073] (3) Single silicon wafer bonding and pressing: The ceramic disk heated to T1=128℃ in step (1) is transferred to the bonding station, where the ambient temperature T2 is maintained at 128℃; then, the reverse suction head vacuum adsorbs the front side of the silicon wafer that has been coated with wax in step (2); the suction head carries the silicon wafer up, completes a 180° flip and then descends, so that the wax layer on the back of the silicon wafer is aligned with the heated ceramic disk; the suction head presses the back of the silicon wafer onto the surface of the ceramic disk with controllable pressure, maintains the pressure for about 5 seconds, releases the vacuum, removes the suction head, and allows the wax layer to slowly solidify in the heat-preserving environment, thus completing the bonding of a single silicon wafer.

[0074] (4) Repeat steps (2) and (3) to continuously attach a total of 5 silicon wafers onto the same ceramic disk. Due to the good heat preservation of the attachment station (T2=128℃), the surface temperature of the ceramic disk can still be maintained above 125℃ when attaching the 5th silicon wafer, which is higher than the wax flow start temperature, ensuring that the wax layer can still melt well when the last silicon wafer is attached. After the entire disk of silicon wafers is attached and cooled, peeling and polishing are performed.

[0075] The process effect of this embodiment is as follows: Figure 3 As shown. The left image shows the surface condition of the ceramic disc after peeling, and its surface smoothness is better than... Figure 2The left image shows almost no visible wax residue. The right image shows the surface morphology of the corresponding silicon wafer after polishing, indicating a smooth, uniform surface with low micro-roughness.

[0076] Peeling effect: After continuous application and testing of 20 trays (a total of 100 silicon wafers), the surface of the ceramic trays was extremely smooth after all silicon wafers were peeled off, with virtually no visible wax residue and a wax residue abnormality rate of close to 0%.

[0077] Polishing effect: After polishing, the surface morphology of the silicon wafers was tested and it was found that defects such as shallow pits at the edges completely disappeared, the overall flatness (TTV) was excellent, and the flatness defect rate was reduced to 1.0% (based on the test results of the above 100 silicon wafers).

[0078] Example 3

[0079] This embodiment of the method for improving abnormal wax marks after silicon wafer peeling includes the following steps:

[0080] (1) Ceramic disc preheating and temperature control: The ceramic disc is loaded onto the conveying mechanism and passes through the three zones of the heating unit in sequence: heating zone 1, heating zone 2, and heating zone 3. Heating zone 1: The temperature of this zone is set at 122℃. Heating zone 2: The temperature of this zone is set at 132℃. Heating zone 3: The temperature of this zone is set at 150℃; this zone adopts closed-loop temperature control: the surface temperature of the ceramic disc is monitored in real time. When it reaches 128℃, the robot lifts it away from the heat source to stop heating. When the temperature drops to 126℃, it is put back into the heat source to resume heating; through cyclic control, the surface temperature of the ceramic disc when it leaves this zone and enters the bonding station is accurately T1=127℃.

[0081] (2) Waxing on the back of silicon wafer: Take a 200mm semiconductor silicon wafer and perform waxing operation at an independent waxing station: Place the silicon wafer with the back facing up on a high-speed rotating table and fix it with vacuum adsorption; set the waxing process parameters: the wax amount V of a single silicon wafer is 0.72 mL; the waxing speed S of the rotating table carrying the silicon wafer is 1550 rpm; start the rotating table, and after the speed stabilizes at 1550 rpm, drip 0.72 mL of molten adhesive wax onto the center of the back of the silicon wafer through the dispensing valve; at a speed of 1550 rpm, the centrifugal force causes the wax liquid to spread rapidly and evenly to the entire back of the silicon wafer, forming an ultra-thin and uniform initial wax film.

[0082] (3) Single silicon wafer bonding and pressing: The ceramic disk heated to T1=127°C in step (1) is transferred to the bonding station, where the ambient temperature T2 is maintained at 126°C; then, the reverse suction head vacuum adsorbs the front side of the silicon wafer that has been coated with wax in step (2); the suction head carries the silicon wafer up, completes a 180° flip and then descends, so that the wax layer on the back of the silicon wafer is aligned with the heated ceramic disk; the suction head presses the back of the silicon wafer onto the surface of the ceramic disk with controllable pressure, maintains the pressure for about 5 seconds, releases the vacuum, removes the suction head, and allows the wax layer to slowly solidify in the heat-preserving environment, thus completing the bonding of a single silicon wafer.

[0083] (4) Repeat steps (2) and (3) to continuously attach a total of 6 silicon wafers onto the same ceramic disk. Due to the good heat preservation of the attachment station (T2=126℃) and the initial T1 setting, the surface temperature of the ceramic disk can still be maintained above 123℃ when attaching the 6th silicon wafer, which is higher than the wax flow start temperature, ensuring that the wax layer can still melt well when the last silicon wafer is attached. After the entire disk of silicon wafers is attached and cooled, peeling and polishing are performed.

[0084] The process effect of this embodiment is as follows: Figure 4 As shown in the image, the left image shows the surface condition of the ceramic disk after peeling off; most of the disk surface is smooth, with only a few minor traces in a few locations. The right image shows the surface morphology of the corresponding silicon wafer after polishing, indicating that the polished surface of the silicon wafer has good overall uniformity and very few defects.

[0085] Peeling effect: 15 trays (90 silicon wafers in total) were continuously applied and tested. After all silicon wafers were peeled off, the surface of the ceramic tray was smooth. Only a very few places had slight wax residue. The wax residue abnormality rate was 2.0%.

[0086] Polishing effect: After polishing, the surface morphology of the silicon wafers was tested and found to have very few defects such as shallow pits at the edges. The overall flatness (TTV) was good, and the flatness defect rate was 1.2% (based on the test results of the above 90 silicon wafers).

[0087] Comparative Example 1

[0088] This comparative example includes the following steps:

[0089] (1) Ceramic disc preheating and temperature control: The ceramic disc is loaded onto the conveying mechanism and passes through the three zones of the heating unit in sequence. The heating regime is exactly the same as in Example 1, specifically: the first heating zone is 120°C, the second heating zone is 130°C, and the third heating zone is controlled at 145°C. The surface temperature T1 of the ceramic disc when it enters the bonding station is also 125°C through closed-loop control. The ambient temperature T2 of the bonding station is also maintained at 125°C.

[0090] (2) Waxing the back of the silicon wafer: Take a 200mm semiconductor silicon wafer and perform waxing operation at the waxing station. The waxing parameters are the same as the original settings before the improvement: the wax amount V of a single silicon wafer is 1.0 mL; the waxing speed S of the rotating table supporting the silicon wafer is 1000 rpm. The waxing operation method is the same as in Example 1.

[0091] (3) Adhesion and pressing: The subsequent adhesion operation steps and parameters (including pressure, holding time, etc.) are the same as in Example 1.

[0092] (4) Continuous application: After applying 5 silicon wafers continuously on the same ceramic disk, peeling and polishing are performed.

[0093] Process observation: When attaching the first few silicon wafers, due to the high temperature of the ceramic disk (T1=125℃), the large amount of wax applied and the low rotation speed, the molten wax layer flowed excessively, and the wax film was obviously uneven after attachment.

[0094] The process effect of this comparative example is as follows: Figure 5 As shown in the image, the left image shows the surface condition of the ceramic disc after peeling. The wax residue on the ceramic disc is sparse and irregular, indicating that the wax layer failed to adhere well to the disc surface due to excessive flow. The right image shows the surface morphology of the corresponding silicon wafer after polishing, revealing obvious, uneven mottled textures or localized depressions, indicating instability and poor flatness caused by uneven wax film.

[0095] Peeling effect: After continuous application and testing of 10 trays (50 silicon wafers in total), after all silicon wafers were peeled off, there were few and irregular wax marks on the ceramic trays, but a large amount of wax abnormally remained on the back of the silicon wafers, with a wax mark abnormality rate as high as 40%.

[0096] Polishing effect: Due to uneven wax film thickness, the support is uneven, and the surface of the silicon wafer shows significant flatness problems after polishing. The flatness defect rate is 22% (based on the test results of the above 50 silicon wafers).

[0097] Comparative Example 2

[0098] This comparative example includes the following steps:

[0099] (1) Preheating and temperature control of ceramic discs: A relatively low heating regime is adopted. The first heating zone is 110℃, the second heating zone is 120℃, and the third heating zone is controlled at 135℃. Through simple on / off control, the surface temperature T1 of the ceramic disc when it enters the bonding station is 120℃ (only slightly higher than the softening point of the wax). The bonding station is not specially insulated, and the ambient temperature T2 is 110℃.

[0100] (2) Waxing on the back of silicon wafers: Conventional waxing parameters were used. The wax amount V for a single silicon wafer was 1.0 mL; the waxing speed S was 1000 rpm.

[0101] (3) Adhesion and pressing: The subsequent operation steps are the same as in Example 1.

[0102] (4) Continuous application: After applying 5 silicon wafers continuously on the same ceramic disk, peeling and polishing are performed.

[0103] Process observation: The wax layer melted reasonably well when the first and second silicon wafers were attached. However, when attaching the third and subsequent silicon wafers, the wax layer melted insufficiently and had poor fluidity because the temperature of the ceramic disk had dropped to near or below the wax's flow initiation temperature.

[0104] The process effect of this comparative example is as follows: Figure 6 As shown in the image, the left image shows the surface state of the ceramic disc after peeling off, with a large number of clearly visible cloud-like or blocky wax residues remaining on the surface. The right image shows the surface morphology of the corresponding silicon wafer after polishing, revealing obvious local defects such as shallow pits at the edges. The analysis suggests that these defects are due to flatness issues caused by insufficient melting and poor filling and adhesion of the wax layer.

[0105] Peeling effect: After continuous application and testing of 20 trays (100 silicon wafers in total), a large number of obvious wax marks remained on the surface of the ceramic trays after all silicon wafers were peeled off, with an abnormality rate of approximately 38%.

[0106] Polishing effect: Due to poor wax layer filling and adhesion, the silicon wafer is unstable during the polishing process, and defects such as shallow pits at the edges are prone to appear on the surface after polishing. The flatness defect rate is about 18% (based on the test results of the above 100 silicon wafers).

[0107] The above embodiments are merely illustrative of the principles and effects of the present invention and are not intended to limit the invention. Any person skilled in the art can 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 those skilled in the art without departing from the spirit and technical concept disclosed in the present invention should still be covered by the claims of the present invention.

Claims

1. A method for improving abnormal wax marks after silicon wafer peeling, characterized in that, Includes the following steps: (1) The ceramic disc carrying the wax layer is heated so that it reaches the target temperature T1 when it enters the application station; the target temperature T1 is higher than the softening temperature and flow start temperature of the application wax used. (2) The wax is applied to the back of the silicon wafer; the amount of wax applied to a single silicon wafer, V, and the waxing speed, S are matched so that at the target temperature T1, the wax layer can be uniformly filled between the silicon wafer and the ceramic disk and form a wax film with controlled thickness. (3) At the bonding station, the back of the silicon wafer coated with wax in step (2) is pressed onto the wax layer of the heated ceramic disk.

2. The method for improving abnormal wax marks after silicon wafer peeling as described in claim 1, characterized in that, Includes one or more of the following characteristics: (a) The target temperature T1 is 125~135℃; (b) The amount of wax applied, V, is 0.7~0.9 mL / piece; (c) The waxing rotation speed S is 1300~1700 rpm; (d) The softening temperature of the adhesive wax is 60~80℃ and the flow start temperature is 70~90℃.

3. The method for improving abnormal wax marks after silicon wafer peeling as described in claim 2, characterized in that, Includes one or more of the following characteristics: (a1) The target temperature T1 is 125~130℃; (b1) The amount of wax applied, V, is 0.75~0.85 mL / piece; (c1) The waxing speed S is 1400~1600 rpm.

4. The method for improving abnormal wax marks after silicon wafer peeling as described in any one of claims 1 to 3, characterized in that, The ambient temperature at the application station is maintained at T2, and the difference between T2 and T1 is within ±10℃.

5. The method for improving abnormal wax marks after silicon wafer peeling as described in claim 4, characterized in that, The T2 is 125~135℃.

6. The method for improving abnormal wax marks after silicon wafer peeling as described in any one of claims 1 to 3, characterized in that, The heating process of the ceramic disc includes passing it sequentially through a first heating zone, a second heating zone, and a third heating zone with increasing temperatures. The target temperature T1 is achieved by controlling the temperature of the third heating zone.

7. The method for improving abnormal wax marks after silicon wafer peeling as described in claim 6, characterized in that, The set temperature of the third heating zone is 135~160℃.

8. The method for improving abnormal wax marks after silicon wafer peeling as described in any one of claims 1 to 3, characterized in that, The method is used to continuously attach 4 to 6 silicon wafers on the same ceramic disk, preferably 5 wafers.

9. The method for improving abnormal wax marks after silicon wafer peeling as described in claim 6, characterized in that, The temperature control method of the third heating zone includes: monitoring the real-time temperature of the ceramic plate in the third heating zone; when the real-time temperature reaches the set upper limit, lifting the ceramic plate away from the heating zone to stop heating; and when the real-time temperature drops to the set lower limit, placing the ceramic plate back into the heating zone to resume heating.

10. The method for improving abnormal wax marks after silicon wafer peeling as described in any one of claims 1 to 3, characterized in that, The waxing rotation speed S is the rotational speed of the waxing head, or the rotational speed of the rotary table that carries the silicon wafer.

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