Method for removing photoresist on wafer and semiconductor process equipment
By detecting the characteristic quantity of spectral intensity change during the photoresist removal process on the wafer, the problem of hardened layer cracking at high temperature was solved, realizing an efficient photoresist removal method and improving the photoresist removal efficiency.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- BEIJING NAURA MICROELECTRONICS EQUIP CO LTD
- Filing Date
- 2023-08-23
- Publication Date
- 2026-06-23
Smart Images
Figure CN119511654B_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of semiconductor manufacturing, and more specifically, to a method for removing photoresist from a wafer and semiconductor process equipment. Background Technology
[0002] In semiconductor manufacturing processes, extremely fine patterns need to be fabricated on wafers. Typically, photolithography is used to transfer the circuit pattern from a photomask onto a photoresist layer covering the wafer surface, followed by etching to transfer the photoresist pattern onto the wafer. To prevent the wafer from being affected by the photoresist in subsequent processes, residual photoresist needs to be removed. In conventional dry photoresist removal processes, the wafer is usually placed directly at a high temperature for removal. However, ion implantation of photoresist causes surface carbonization, resulting in a hardened layer (e.g., 110). Figure 1 As shown in the figure, there is an uncrosslinked layer (photoresist, abbreviated as PR) 120, and a hardened layer 110 covering the outside of the uncrosslinked layer 120. The hardened layer 110 is prone to popping at high temperatures. Summary of the Invention
[0003] The present invention aims to solve at least one of the technical problems existing in the prior art, and proposes a method for removing photoresist on a wafer and semiconductor process equipment.
[0004] To achieve the objective of this invention, a method for removing photoresist from a wafer is provided, comprising:
[0005] During the process of removing the photoresist after ion implantation, the spectral intensity of the emitted light generated by a specific element in the chamber at different sampling times is obtained;
[0006] Based on the spectral intensities corresponding to two adjacent sampling times, determine the change characteristic quantity of the spectral intensity at each sampling time;
[0007] When the change characteristic quantity corresponding to the current sampling time meets the preset conditions, it is determined that the hardening layer removal process is nearing its end and the wafer is controlled to descend from the current position toward the heating base according to the preset relationship to remove the hardening layer of the photoresist.
[0008] In the removal method described above, the change feature is the rate of decrease in spectral intensity between two adjacent sampling times, and the change feature satisfies the following relationship:
[0009] Q n =[S(t) n-1 )-S(t n )]÷S(t n-1 ); where Q nLet S(t) be the change feature quantity corresponding to the nth sampling time. n ) represents the spectral intensity at the nth sampling time, where n is a positive integer.
[0010] In the removal method described above, the preset condition includes that the change feature quantity corresponding to the current sampling time is greater than a preset value, wherein the preset value is a non-negative number.
[0011] In the removal method described above, the preset value is greater than or equal to 5% and less than or equal to 20%.
[0012] In the removal method described above, the preset condition further includes the time interval between the moment when the spectral intensity reaches its maximum value and the current sampling moment.
[0013] The removal method described above, wherein the delay duration is calculated according to the following formula;
[0014] T = k / Q max Where T is the delay duration; k > 0, and k is a constant; Q max The maximum value of the absolute value of the change characteristic quantity before the spectral intensity reaches its maximum value.
[0015] In the removal method described above, the preset relationship is that the descent displacement Δh of the wafer is equal to the product of the descent time Δt and a constant a, where a is greater than 0.
[0016] The removal method described above, before obtaining the spectral intensity of the emitted light generated by a specific element in the chamber at different sampling times, further includes:
[0017] The wafer is placed on the bearing surface of the heating base, and after the preheating time is reached, the wafer is controlled to rise to the initial high position.
[0018] The removal method described above, after controlling the wafer to descend from its current position toward the heating base according to a preset relationship to remove the hardened layer of the photoresist, further includes:
[0019] When the change characteristic quantity corresponding to the current sampling time meets the hardening layer removal termination condition, the wafer is controlled to descend to the bearing surface of the heating base to remove the uncrosslinked layer of the photoresist.
[0020] As another technical solution, the present invention also provides a semiconductor process apparatus, comprising: a chamber, a heating base, and a controller, wherein the heating base is disposed in the chamber and has a bearing surface for supporting a wafer; the controller includes at least one processor and at least one memory, wherein the memory stores a computer program, and the processor executes the computer program to perform the removal method according to any one of the present invention.
[0021] The present invention has the following beneficial effects:
[0022] The method and semiconductor process equipment for removing photoresist on wafers provided by the present invention obtain the spectral intensity of the emitted light generated by a specific element, and determine whether the hard layer removal process is close to the end based on whether the characteristic quantity of the change in spectral intensity meets the preset conditions. When the hard layer removal process is close to the end, the wafer is controlled to descend and the temperature is increased to avoid the hard layer from cracking at high temperature.
[0023] Furthermore, using the removal method of this invention, the wafer descends before the hardened layer removal process reaches its endpoint. This ensures that the hardened layer does not crack, and on the one hand, increases the rate of removing residual hardened layer, allowing any remaining small amount to be quickly removed during wafer descent. This enables the hardened layer removal process to reach its endpoint earlier, shortening the removal time and thus improving resist removal efficiency. On the other hand, before the hardened layer removal process reaches its endpoint, the distance between the wafer and the support surface gradually decreases, causing the wafer temperature to rise. This minimizes the time required for the wafer temperature to rise to the level needed to remove the uncrosslinked layer when the hardened layer removal process reaches its endpoint, further improving resist removal efficiency. Attached Figure Description
[0024] Figure 1 This is a schematic diagram of the photoresist after ion implantation.
[0025] Figure 2 This is a schematic diagram showing the relationship between the temperature of the wafer and the distance between the wafer and the support surface.
[0026] Figure 3 This is a schematic diagram of the structure of a semiconductor process equipment provided in an embodiment of this application;
[0027] Figure 4 This application provides a schematic diagram of a hardware module for a semiconductor process apparatus.
[0028] Figure 5 A schematic flowchart illustrating a method for removing photoresist from a wafer, provided in an embodiment of this application;
[0029] Figure 6 This is a schematic diagram showing the relationship between wafer temperature and resist removal rate.
[0030] Figure 7A graph showing the relationship between spectral intensity and sampling time during the resist removal process, which controls wafer descent when the hardened layer removal process reaches its endpoint.
[0031] Figure 8 for Figure 7 The curve showing the relationship between the height of the wafer relative to the carrier surface and the sampling time during the corresponding resist removal process;
[0032] Figure 9 This is a graph showing the relationship between spectral intensity and sampling time during the adhesive removal process of a removal method provided in this application embodiment;
[0033] Figure 10 for Figure 9 The curve showing the relationship between the height of the wafer relative to the carrier surface and the sampling time during the corresponding resist removal process;
[0034] Figure 11 This is a graph showing the relationship between spectral intensity and sampling time during the degumming process of another removal method provided in this application embodiment;
[0035] Figure 12 for Figure 11 The curve showing the relationship between the height of the wafer relative to the carrier surface and the sampling time during the corresponding resist removal process;
[0036] Figure 13 This is a schematic flowchart of another method for removing photoresist on a wafer, provided in an embodiment of this application. Detailed Implementation
[0037] Before introducing the embodiments of this application, the relevant technologies will be described first.
[0038] Since the hardened layer 110 is prone to cracking at high temperatures, the following steps can be used in the post-ion implantation resist removal process to avoid popping. Step 1: Hardened layer 110 removal process. The wafer temperature is adjusted to a lower value, and a mixture of O2, N2, and H2 gases is injected. O2 removes elements such as C, H, N, and S from the hardened layer 110, while the N2 and H2 mixture allows non-volatile substances (oxides such as P2O5 and As2O3) to react with H to form volatile products. Step 2: Uncrosslinked layer 120 removal process. The wafer temperature is adjusted to a higher value, and O2 is injected. O2 reacts with the uncrosslinked layer 120 to form volatile products.
[0039] When removing resist from a wafer using semiconductor processing equipment, the wafer can be placed on the support surface of a heating base. The heating base supports the wafer, and the wafer can also be moved upwards relative to the heating base to a certain distance from the support surface. The heating base is equipped with a heater, which is energized to heat the heating base, causing it to heat up. The heat from the heating base is conducted to the wafer, thus regulating the wafer's temperature. The wafer's temperature is related to its distance from the support surface; the relationship between the two can be found in [reference needed]. Figure 2 As shown. Specifically, in the vertical direction, the smaller the distance between the wafer and the support surface, the higher the wafer temperature; in the vertical direction, the larger the distance between the wafer and the support surface, the lower the wafer temperature.
[0040] Therefore, it is necessary to reasonably adjust the distance between the wafer and the carrier surface to control the semiconductor process equipment to perform the hardened layer removal process first, and then perform the uncrosslinked layer removal process after the hardened layer is removed.
[0041] In related technologies, the distance between the wafer and the support surface and the process time in the hardened layer removal process are set as empirical values, as are the distance between the wafer and the support surface and the process time in the uncrosslinked layer removal process, thereby forming specific process formulations. When using the same process formulation for resist removal, the wafer lifting and lowering process is identical.
[0042] However, the inventors of this application have discovered that due to the different ion implantation amounts of different types of wafers, the thickness of the hardened layer varies. Therefore, when using a specific process formulation to remove resist from different types of wafers, the following problems easily occur: First, before the process time of the hardened layer removal step reaches the set empirical value, the hardened layer is completely removed, but the distance between the wafer and the substrate is still large. Failure to switch from step 1 to step 2 in time results in a long removal process, low efficiency, and low throughput. Second, when the process time of the hardened layer removal step reaches the set empirical value, the hardened layer is not completely removed, and the distance between the wafer and the substrate decreases. Prematurely switching from step 1 to step 2 causes the hardened layer to crack at higher temperatures. Therefore, using a specific process formulation for resist removal is not suitable for different types of wafers.
[0043] The root cause of these problems lies in the fact that the thickness of the hardened layer varies among different types of wafers. Therefore, when using a specific process formula for resist removal, the process is considered to have reached its endpoint when the process time of the hardened layer removal step reaches the set empirical value. This can easily lead to the termination of the hardened layer removal process.
[0044] To address the aforementioned problems in related technologies, the inventors of this application propose a method for removing photoresist from a wafer. This method determines whether the hardening layer removal process has reached its endpoint based on the spectral intensity of the emitted light from a specific element in the chamber. When the hardening layer removal process reaches its endpoint, the wafer is lowered onto a heating pedestal, causing the wafer to heat up to remove the uncrosslinked layer. Thus, by determining the endpoint of the hardening layer removal process based on changes in spectral intensity signals, automatic detection of the endpoint is achieved. Furthermore, during the hardening layer removal process, the spectral intensity of a specific element changes with the amount of process gas or reactant gas containing that specific element. Therefore, even if wafers manufactured using the same process have different thicknesses of hardened photoresist layers, this method can accurately monitor the progress of the photoresist removal process, resulting in high accuracy in determining the endpoint of the hardening layer removal process.
[0045] However, in practical applications, the wafer is heated by the heat radiation from the heating base, and the wafer heating process takes a certain amount of time. Therefore, the wafer is only controlled to descend when the hardened layer removal process reaches its end point. The wafer cannot be heated quickly to the higher temperature value required to remove the uncrosslinked layer, resulting in low removal efficiency of both the hardened and uncrosslinked layers.
[0046] To improve the efficiency of photoresist removal, this application provides a method for removing photoresist from wafers and semiconductor process equipment.
[0047] Figure 3 This is a schematic diagram of a semiconductor process apparatus provided in an embodiment of this application. Please refer to [link / reference]. Figure 3 The semiconductor process equipment includes a chamber 200 and a heating base 400, the heating base 400 being located within the chamber 200 and having a support surface for supporting a wafer 300. The chamber 200 can perform a photoresist removal process to remove ordinary photoresist or ion-implanted photoresist from the surface of the wafer 300.
[0048] The heating base 400 is equipped with a heater 410. The heater 410 is connected to a power supply 500 located outside the chamber 200. When the heater 410 is powered on, the heating base 400 is heated.
[0049] In some embodiments, the semiconductor process equipment further includes a lifting assembly (not shown) and three lifting pins 210. The heating base 400 has three through holes corresponding to the three lifting pins 210. The three lifting pins 210 abut against the back surface of the wafer 300. The lifting assembly drives the three lifting pins 210 to move up and down along the corresponding through holes, changing the distance between the wafer 300 and the bearing surface of the heating base 400, thereby altering the heat radiated from the heating base 400 to the wafer 300 and thus regulating the temperature of the wafer 300. It is understood that the number of lifting pins 210 is not limited to three; the specific number can be designed based on experience and actual operating conditions.
[0050] Figure 4 This is a schematic diagram of a hardware module for a semiconductor process apparatus provided in an embodiment of this application. Please refer to... Figure 3 and Figure 4 The semiconductor process equipment also includes a spectral intensity detection device 800 and a controller 700.
[0051] For example, controller 700 includes at least one processor 710 and at least one memory 720. The memory 720 can be used to store program code. The memory 720 can be configured as any type of memory. For example, the memory 720 can be implemented as flash memory, read-only memory (ROM), random access memory (RAM), removable memory, other types of storage elements, or any combination of such storage devices.
[0052] The processor 710 can be used to execute the aforementioned application code and call relevant modules to implement the functions of the semiconductor process equipment in this embodiment. The processor 710 may include one or more processing units, such as an application processor (AP), a modem processor, a graphics processing unit (GPU), an image signal processor (ISP), a video codec, a digital signal processor (DSP), a baseband processor, and / or a neural network processing unit (NPU). Different processing units can be independent devices or integrated into one or more processors 710.
[0053] The spectral intensity detection device 800 is used to detect the spectral intensity of the emitted light produced by a specific element. The spectral intensity detection device 800 is electrically connected to the controller 700 to send the detected spectral intensity to the controller 700. Specifically, the spectral intensity detection device 800 can be implemented using a spectral sensor. The spectral intensity detection device 800 can detect the spectral intensity in real time or collect spectral intensity at preset time intervals.
[0054] In some embodiments, the semiconductor process apparatus disclosed herein may further include a first timer 910 and a second timer 920, both of which are connected to the controller 700 and are used for timing.
[0055] The controller 700 described above is also communicatively connected to the lifting assembly via a communication module 930, enabling it to control the lifting assembly. The communication module 930 can be implemented as one or more of any conventional communication interfaces.
[0056] It is understood that the structures illustrated in the embodiments of the present invention do not constitute a specific limitation on semiconductor process equipment. In other embodiments of the present invention, the semiconductor process equipment may include more or fewer components than illustrated, or combine certain components, or split certain components, or have different component arrangements. The illustrated components may be implemented in hardware, software, or a combination of software and hardware.
[0057] Figure 5 This is a schematic flowchart illustrating a method for removing photoresist from a wafer, provided in an embodiment of this application. The above-described semiconductor process equipment can be used to perform this method for removing photoresist from a wafer; the specific process of this removal method can be found in [link to relevant documentation]. Figure 5 ,include:
[0058] S101, during the process of removing the photoresist after ion implantation, obtain the spectral intensity of the emitted light generated by a specific element in the chamber at different sampling times.
[0059] The specific element can refer to the element implanted by the ion, such as P, As, B, etc.
[0060] Specifically, this step involves acquiring the spectral intensity by receiving the spectral intensity detected by the spectral intensity detection device 800.
[0061] There is a one-to-one correspondence between each sampling moment and the spectral intensity at that sampling moment. Similarly, the time between each sampling moment and the first sampling moment is the sampling duration, and there is also a one-to-one correspondence between the sampling duration and the corresponding spectral intensity.
[0062] S102, based on the spectral intensities corresponding to two adjacent sampling times, determine the characteristic quantity of the change in spectral intensity at each sampling time.
[0063] S103, when the change characteristic quantity corresponding to the current sampling time meets the preset conditions, determine that the hardening layer removal process is close to the end point and control the wafer to descend from the current position toward the heating base according to the preset relationship to remove the hardening layer of photoresist.
[0064] It should be noted that reasonable design preset conditions should ensure that the change characteristic quantity corresponding to the current sampling time meets the preset conditions before the hardened layer removal termination condition is met. The fact that the change characteristic quantity corresponding to the current sampling time meets the preset conditions should be able to indicate that most of the hardened layer has been removed, the hardened layer has not been completely removed, a small amount of hardened layer remains, and the hardened layer removal process is nearing its end.
[0065] The characteristic quantity of spectral intensity change should reflect the progress of the adhesive removal process, so as to accurately determine that the hardened layer removal process is nearing its end based on the characteristic quantity of change. Therefore, specific elements also need to meet the characteristic that the spectral intensity change trend during the removal of the hardened layer is different from the spectral intensity change trend during the removal of the uncrosslinked layer.
[0066] As described above, at the start of the process to remove the hardened layer, the wafer should be in an initial high position. At this time, the distance between the wafer and the support surface is H1, ensuring that the wafer temperature is below or equal to 200°C to prevent popping. The general process of the removal method in this embodiment is as follows: if the change characteristic quantity corresponding to the current sampling time meets the preset conditions, the wafer is controlled to descend from the initial high position to approach the heating base, causing the wafer to heat up and simultaneously removing the small amount of residual hardened layer; during the descent, the spectral intensity of the emitted light generated by specific elements is continuously acquired. If the change characteristic quantity corresponding to the current sampling time still meets the preset conditions, the wafer is controlled to descend from the current position to continue cleaning the small amount of residual hardened layer until the hardened layer is completely removed.
[0067] As disclosed in this paper, the wafer can be controlled to descend from its current position toward the heating base in the removal method as follows. For example, a signal is sent to the lifting assembly, causing the lifting assembly to drive the lifting pin downwards, thereby lowering the wafer.
[0068] The removal method in this embodiment obtains the spectral intensity of the emitted light from a specific element and determines whether the hardening layer removal process is nearing its end based on whether the change in spectral intensity meets preset conditions. When the hardening layer removal process is nearing its end, the wafer is lowered and the temperature is increased. In other words, before the wafer descends, the distance between the wafer and the heating base is relatively large, and the wafer temperature is relatively low to prevent the hardening layer from cracking at high temperatures. It is worth noting that since only a small amount of hardening layer remains when the hardening layer removal process is nearing its end, even if the wafer descends and the temperature increases, the remaining small amount of hardening layer will not crack. Therefore, the removal method in this embodiment can effectively solve the problem of hardening layer cracking at high temperatures.
[0069] It is understandable that during the resist stripping process, when only wafer temperature is a variable in the process conditions, the resist stripping rate is positively correlated with wafer temperature. For details, please refer to [reference needed]. Figure 6 As shown, the higher the wafer temperature, the faster the resist removal rate. Based on this, in the removal method of this embodiment, the wafer descends before the hardened layer removal process reaches its endpoint. Thus, when using this removal method, since part of the hardened layer has already been removed, its thickness becomes thinner. By controlling the wafer to descend according to a preset relationship, "popping" can be avoided. On the one hand, the wafer temperature can be increased, allowing the remaining hardened layer to be removed at a higher temperature, increasing the hardened layer removal rate. This allows any remaining small amount of hardened layer to be quickly removed during the wafer's descent, enabling the hardened layer removal process to reach its endpoint earlier, shortening the hardened layer removal time, and thus improving resist removal efficiency. On the other hand, before the hardened layer removal process reaches its endpoint, the distance between the wafer and the carrier surface gradually decreases, and the wafer temperature rises. This allows the wafer to quickly heat up to the process temperature corresponding to the uncrosslinked layer removal process after the hardened layer removal process reaches its endpoint, enabling a rapid switch to the uncrosslinked layer removal process. This minimizes the heating time required to switch from the hardened layer removal process to the uncrosslinked layer removal process, thereby improving resist removal efficiency.
[0070] The removal method disclosed herein may also perform S104 after S103.
[0071] S104: When the change characteristic quantity corresponding to the current sampling time meets the hardening layer removal termination condition, control the wafer to descend to the bearing surface of the heating base to remove the uncrosslinked layer of photoresist.
[0072] If the change characteristic quantity corresponding to the current sampling time meets the hardening layer removal termination condition, it means that the hardening layer has been completely removed and the hardening layer removal process has reached its end.
[0073] The general process of the removal method in this embodiment is as follows: when the change feature quantity corresponding to the current sampling time meets the preset conditions, the wafer is controlled to descend from the current position to continue removing the small amount of residual hardened layer; then the spectral intensity of the emitted light generated by the specific element is obtained. If the change feature quantity corresponding to the current sampling time meets the hardened layer removal termination condition, the wafer is controlled to continue descending to the bearing surface of the heating base, and the temperature of the wafer is raised to 250°C to 300°C to remove the uncrosslinked layer.
[0074] It should be noted that the above-mentioned change characteristics can be interpreted broadly, as long as they can characterize the changing trend of the photoresist removal process.
[0075] In the first implementation, the variation characteristic can be the change in the spectral intensity of the emitted light from a specific element between two adjacent sampling times. The variation characteristic can be determined according to the following equation (I), where S(t) n ) represents the spectral intensity at the nth sampling time, where n is a positive integer, and ΔS n Let be the change characteristic quantity at the nth sampling time.
[0076] ΔS n =S(t) n )-S(t n-1 Formula (1)
[0077] In the second implementation, the variation characteristic can be the rate of change of the spectral intensity of the emitted light from a specific element between two adjacent sampling times. The variation characteristic can be determined according to the following equation (ii), where S n ′ represents the change characteristic at the nth sampling time.
[0078] S n ′=[S(t n )-S(t n-1 )] / (t n -t n-1 Formula (II)
[0079] In the third implementation, the change characteristic can be the rate of decrease in spectral intensity between two adjacent sampling times. The change characteristic can be determined according to the following equation (iii), where Q n Let be the change feature quantity corresponding to the nth sampling time.
[0080] Q n =[S(t) n-1 )-S(t n )]÷S(t n-1 Formula (III)
[0081] As the hardening layer removal process nears completion in its later stages, the spectral intensity continues to decrease. Therefore, using the rate of decrease to characterize the change in the characteristic quantity provides a more convenient way to determine whether the change in the characteristic quantity meets the preset conditions. The change in the characteristic quantity is denoted as Q below. n Using an example, those skilled in the art will clearly understand after reading the following text that the changing characteristic quantity is ΔS n or S n The technical solution of ′.
[0082] The termination condition for hardening layer removal described in this article can be that the change characteristic quantity is 0 or close to 0, indicating that the spectral intensity of a specific element has not changed, which means that the amount of process gas or reaction gas containing the specific element tends to be stable, and the hardening layer removal process reaches its end point.
[0083] As disclosed in this paper, the preset condition can be set to include the change feature quantity corresponding to the current sampling time being greater than a preset value, where the preset value is a non-negative number. In other words, the preset condition satisfies the change feature quantity Q. n >0. As can be seen from the above, if the change characteristic quantity corresponding to the current sampling time is a positive number, that is, the spectral intensity decrease rate of the emitted light generated by a specific element is greater than 0, it means that the spectral intensity is on the falling edge, which indicates that the hardened layer removal process is nearing its end. At this time, the wafer can be controlled to descend to remove the residual hardened layer.
[0084] The preset value can be greater than or equal to 5% and less than or equal to 20%. Taking a preset value of 5% as an example, when the rate of decrease in spectral intensity between two adjacent sampling times is equal to 5%, the wafer descent is controlled. Here, the preset value is an empirical value obtained through a large number of process tests and simulation experiments. At this time, when using the method of this embodiment to remove the photoresist after ion implantation, the photoresist removal efficiency is high. Of course, the preset value is not limited to 5% to 20% and can be designed according to actual working conditions.
[0085] The resist removal process that controls wafer descent when the hardened layer removal process reaches its end point is compared with the resist removal process using the removal method of this embodiment.
[0086] Figure 7 This is a graph showing the relationship between spectral intensity and sampling time during the resist removal process, which controls wafer descent when the hardened layer removal process reaches its endpoint. Figure 8 for Figure 7 The graph showing the relationship between the height of the wafer relative to the carrier surface and the sampling time during the corresponding resist removal process. Figure 7 and Figure 8In the example shown, the resist removal process is as follows: First, the wafer is raised to an initial high position, with the height of the wafer relative to the support surface being H1, to remove the hardened layer; the height of the wafer relative to the support surface is maintained at H1; when the sampling time is 105s, the spectral intensity is detected to reach its maximum value; until the sampling time is 129.95s, the characteristic quantity Q of the change in spectral intensity at the current sampling moment is determined. n When the value is 0%, the hardened layer removal termination condition is met, and the wafer is controlled to descend to the bearing surface to remove the uncrosslinked layer.
[0087] Figure 9 This is a graph showing the relationship between spectral intensity and sampling time during the adhesive removal process using a method provided in this application. Figure 10 for Figure 9 The graph showing the relationship between the height of the wafer relative to the carrier surface and the sampling time during the corresponding resist removal process. Figure 9 and Figure 10 In the example shown, the resist removal process is as follows: First, the wafer is raised to its initial high position, with the height of the wafer relative to the carrier surface being H1, to remove the hardened layer; the height of the wafer relative to the carrier surface is maintained at H1; the spectral intensity reaches its maximum value when the sampling time is 105s; until the sampling time is 115s, the characteristic quantity Q of the change in spectral intensity at the current sampling moment is determined. n If the value is greater than the preset value C, the preset conditions are met, and the wafer is controlled to descend according to the preset relationship to continue cleaning the residual hardened layer. During the descent, the spectral intensity is continuously monitored until the sampling time is 119.03s, at which point the characteristic quantity Q of the change in spectral intensity at the current sampling moment is determined. n When the value is 0%, the hardened layer removal termination condition is met, and the wafer is controlled to descend to the bearing surface to remove the uncrosslinked layer.
[0088] Combination Figures 7 to 10 As can be seen, the removal method in this embodiment, by controlling the wafer descent to increase the wafer temperature when the changing feature quantity meets the preset conditions and the hardened layer removal process is nearing its end but has not yet reached its end, shortens the sampling time corresponding to the end of the hardened layer removal process from 129.95s to 119.03s, and advances the termination time of the hardened layer removal process by 10.92s. This verifies that the removal method of this embodiment can effectively shorten the time for removing the hardened layer, thereby greatly improving the adhesive removal efficiency.
[0089] In the removal method disclosed in this paper, the preset relationship is that the wafer's descent displacement Δh is equal to the product of the descent duration Δt and the constant a, where a > 0. Here, the constant a can be considered as the wafer's descent speed. The descent duration Δt refers to the time interval from the start of the descent to the current time, and the start of the descent refers to the sampling time corresponding to the change in the characteristic quantity meeting the preset conditions.
[0090] Taking a preset value of 5% and preset conditions including a change in characteristic quantity greater than 5% at the current sampling time as an example, if the sampling duration corresponding to the sampling time when the change in characteristic quantity is greater than 5% is t1, then when the sampling duration reaches t2, the wafer's descent displacement Δh = a*Δt = a*(t2-t1). At this time, the height corresponding to the current position of the wafer is H' = H1 - Δh = H1 - a*(t2-t1). In this implementation scheme, when the change in characteristic quantity corresponding to the current sampling time meets the preset conditions, the wafer is controlled to descend at a uniform speed, so that the wafer heats up at a uniform speed, thereby reducing the risk of the residual hardened layer cracking during the wafer's descent.
[0091] In addition to the preset conditions that the change in characteristic quantity corresponding to the current sampling time is greater than a preset value, the preset conditions further include a time interval T between the time when the spectral intensity reaches its maximum value and the current sampling time. That is, after the spectral intensity reaches its maximum value, at a time interval T and when the change in characteristic quantity is greater than the preset value, the wafer is controlled to descend according to a preset relationship to remove the hardened layer.
[0092] As disclosed in this paper, when the spectral intensity reaches its maximum value, a first timer is used to start timing. When the timing reaches the delay duration T and the change in characteristic quantity is greater than a preset value, the wafer is controlled to descend. Alternatively, in some alternative embodiments, when the spectral intensity reaches its maximum value, the moment corresponding to the maximum spectral intensity is obtained, and this moment is added to the delay duration T to obtain the corresponding descent time point. When the descent time point is reached at the current moment and the change in characteristic quantity is greater than a preset value, the wafer is controlled to descend.
[0093] Therefore, in the removal method of this embodiment, by designing preset conditions including that the change characteristic quantity corresponding to the current sampling time is greater than a preset value, and that the time interval between the current sampling time and the time when the spectral intensity reaches its maximum value is delayed by a time T, it is ensured that the spectral intensity is at the falling edge. When the hardening layer removal process is nearing its end, the wafer is controlled to descend to increase the wafer temperature. In this way, while avoiding the popping phenomenon, the hardening layer removal rate can be increased in the later stage of the hardening layer removal process to shorten the hardening layer removal time, thereby improving the resist removal efficiency.
[0094] Figure 11 This is a graph showing the relationship between spectral intensity and sampling time during the adhesive removal process using another removal method provided in this application embodiment. Figure 12 for Figure 11 The graph showing the relationship between the height of the wafer relative to the carrier surface and the sampling time during the corresponding resist removal process. Figure 11 and Figure 12In the example shown, the resist removal process is as follows: First, the wafer is raised to its initial high position, with the height of the wafer relative to the carrier surface being H1, to remove the hardened layer; the height of the wafer relative to the carrier surface is maintained at H1; when the sampling duration is 105s, the spectral intensity reaches its maximum value, and the first timer starts timing; when the sampling duration is 115s, the timing time of the first timer reaches T, and the characteristic quantity Q of the change in spectral intensity at the current sampling moment is determined. n If the value is greater than the preset value C, the preset condition is met, and the wafer is controlled to descend according to the preset relationship to continue cleaning the residual hardened layer. During the descent, the spectral intensity is continuously monitored until the sampling time is 119.03s, at which point the characteristic quantity Q of the change in spectral intensity at the current sampling time is determined. n When the value is 0%, the hardened layer removal termination condition is met, and the wafer is controlled to descend to the bearing surface to remove the uncrosslinked layer.
[0095] Please refer to this as well. Figure 7 , Figure 8 , Figure 11 and Figure 12 As can be seen, the removal method in this embodiment removes the spectral intensity by delaying for a time T after the spectral intensity reaches its maximum value and then changing the characteristic quantity Q. n The temperature of the wafer is increased by controlling its descent to raise its temperature, thus shortening the sampling time corresponding to the end of the hardened layer removal process from 129.95s to 119.03s, and advancing the termination time of the hardened layer removal process by 10.92s. This verifies that the removal method of this embodiment can effectively increase the hardened layer removal rate, thereby greatly improving the adhesive removal efficiency.
[0096] It should be understood that in an implementation scheme where the preset conditions also include a delay time T between the moment when the spectral intensity reaches its maximum value and the current sampling time, if the sampling time corresponding to the moment when the spectral intensity reaches its maximum value is t', and the change in characteristic quantity is greater than the preset value at the delay time T, and the sampling time corresponding to when the wafer begins to descend is t”, then the descent time Δt satisfies: Δt = t” - t' - T. The descent displacement of the wafer is Δh = a*(t” - t' - T). At this time, the height corresponding to the current position of the wafer is H' = H1 - Δh = H1 - a*(t” - t' - T).
[0097] The aforementioned delay duration T can be designed based on past experience and requirements. For example, the delay duration T can be 5s or 10s. This embodiment does not impose specific limitations on this.
[0098] In some embodiments of this application, the delay duration T can also be determined by calculation when the spectral intensity reaches its maximum value. Specifically, the delay duration T is calculated according to the following formula (iv). Wherein, T is the delay duration; k > 0, and k is a constant; Q maxIt represents the maximum absolute value of the characteristic quantity of change before the spectral intensity reaches its maximum value.
[0099] T = k / Q max Formula (IV)
[0100] Among them, the change characteristic quantity refers to the rate of decrease in spectral intensity between two adjacent sampling times. In the early stage of the hardening layer removal process, the spectral intensity continues to increase, that is, the spectral intensity is on the rising edge, and the change characteristic quantity Q n If it is less than 0, then the characteristic quantity of change Q n The absolute value of represents the rate of increase in spectral intensity, and the characteristic quantity of change is Q. n The maximum absolute value can be understood as the maximum rate of change of spectral intensity.
[0101] Therefore, it can be understood that the delay duration T and Q max There is a negative correlation, meaning the delay time T is negatively correlated with the rate of increase in spectral intensity. Specifically, in the early stages of the hardened layer removal process, the faster the spectral intensity increases, the greater the rate of increase in spectral intensity, and Q... max The larger the value of Q, the smaller the delay time T; conversely, in the early stage of the hardened layer removal process, the slower the increase in spectral intensity and the smaller the rate of increase in spectral intensity. max The smaller the value, the larger the delay time T.
[0102] Thus, when using the method of this embodiment to remove photoresist, the faster the spectral intensity increases, that is, the greater the rate of chemical reaction in the hardening layer removal process, the faster the wafer temperature is increased after the change in characteristic quantity meets the preset conditions, further ensuring that the wafer temperature is increased before the end of the hardening layer removal process is reached.
[0103] Moreover, compared to directly setting the delay time T as a constant, this embodiment determines the delay time T by calculation, which helps to ensure that the delay time T can be adapted to the rate of increase of spectral intensity during the hardening layer removal process for different types of wafers, so as to ensure that when the time is extended to T from the moment when the spectral intensity reaches its maximum value, the hardening layer removal process has not yet reached its end.
[0104] In addition, in an implementation scheme where the preset conditions also include the time interval T between the moment when the spectral intensity reaches its maximum value and the current sampling moment, step S102 can be implemented using the following steps.
[0105] S1021, when the spectral intensity reaches its maximum value, determine the characteristic quantity of the change in spectral intensity corresponding to all sampling times based on the spectral intensity corresponding to two adjacent sampling times.
[0106] S1022, When the absolute value of a characteristic quantity of spectral intensity change is greater than a set threshold, execute S103.
[0107] The threshold value is set to a positive number, and can be reasonably designed based on practical experience and working conditions. In this embodiment, an additional condition is set for executing step S103: the absolute value of the change in spectral intensity is greater than the set threshold. That is, before the spectral intensity reaches its maximum value, in the early stage of the hardening layer removal process, if the growth rate of the spectral intensity is greater than the set threshold (i.e., the spectral intensity increases too rapidly), a delay of time T is applied after the spectral intensity reaches its maximum value, and the change in spectral intensity Q is... n If the value exceeds the preset value, control the wafer descent.
[0108] Thus, the method of controlling the wafer's descent after a time interval T following the spectral intensity reaching its maximum value is suitable for situations where the spectral intensity rises or falls rapidly.
[0109] In any of the above embodiments, preferably, the sampling duration between any two adjacent sampling times is equal, that is, the spectral intensity of the emitted light generated by a specific element is collected every sampling duration Φ, t n -t n-1 =Φ, where Φ is a positive constant. Indicatively, Φ can be set to 0.1s, 0.5s, 1s, etc. This allows for uniform acquisition of spectral intensity, especially in areas with varying characteristic quantities (S). n At this time, it is also beneficial to simplify the computation of changing characteristic quantities.
[0110] In some embodiments, prior to step S101 described above, the removal method of this embodiment may further include the following steps:
[0111] S201, place the wafer on the bearing surface of the heating base, and after the preheating time is reached, control the wafer to rise to the initial high position.
[0112] Here, the initial height of the wafer relative to the bearing surface is H1. Please refer to... Figures 9 to 12 H1 can specifically be 10mm. Of course, H1 is not limited to 10mm; in other embodiments of this application, it can also be 12mm, 15mm, etc.
[0113] In some embodiments of this application, the specific implementation process of step S201 above may include the following steps.
[0114] Step S2011: At the start of the process of removing the photoresist after ion implantation, control the wafer to be placed on the support surface of the heating base and start timing.
[0115] Specifically, this step can be achieved by sending a signal to a second timer to keep track of the time.
[0116] Step S2012: When the timing reaches the preheating time, control the wafer to rise from the support surface to the initial high position.
[0117] The preheating time d can also be designed based on experience and actual working conditions, for example, in Figure 10 and Figure 12 In the example shown, the preheating time d can be specifically designed as 78s.
[0118] In this embodiment, at the start of the hardened layer removal process, the wafer is placed in the bearing surface of the heating base during the preheating time d to preheat the wafer. This allows the wafer to quickly reach the process temperature for the hardened layer removal process when it moves to the initial high position, thus enabling the hardened layer removal process to be carried out as soon as possible and improving the adhesive removal efficiency.
[0119] Figure 13 This is a schematic flowchart illustrating another method for removing photoresist from a wafer, provided as an embodiment of this application. Please refer to... Figure 13 In a specific example, the removal methods include:
[0120] Step S301: At the start of the process of removing the photoresist after ion implantation, place the wafer on the support surface of the heating base and start timing.
[0121] Step S302: When the timing time reaches the preheating duration d, control the lifting component to drive the lifting pin to rise, so that the wafer rises from the support surface to the initial high position.
[0122] Step S303: During the process of removing the photoresist after ion implantation, obtain the spectral intensity of the emitted light generated by a specific element in the chamber at different sampling times.
[0123] Step S303: Determine the characteristic quantity Q of the change in spectral intensity at each sampling time based on the spectral intensities corresponding to two adjacent sampling times. n .
[0124] Step S304: When the spectral intensity reaches its maximum value, calculate the delay time T according to the above formula (iv).
[0125] Step S305: Determine the change feature quantity Q at the current sampling time. n Check if it is greater than or equal to 5%, and determine if there is a time interval T between the current sampling time and the time when the spectral intensity reaches its maximum value; if yes, proceed to step S306; if no, return to step S303.
[0126] Step S306: Control the lifting assembly to drive the lifting pin to move the wafer down from the initial high position toward the heating base according to the preset relationship to remove the hardened layer.
[0127] Step S307: Determine the change feature quantity Q at the current sampling time. nIs it equal to 0%? If yes, determine that the hardened layer removal process has reached its end point and proceed to step S308; otherwise, return to step S305.
[0128] Step S308: Control the lifting assembly to drive the lifting pin to lower the wafer to the bearing surface of the heating base to remove the uncrosslinked layer.
[0129] It is understood that the above embodiments are merely exemplary implementations used to illustrate the principles of the present invention, and the present invention is not limited thereto. For those skilled in the art, various modifications and improvements can be made without departing from the spirit and essence of the present invention, and these modifications and improvements are also considered to be within the scope of protection of the present invention.
Claims
1. A method for removing photoresist from a wafer, characterized in that, The removal method includes: During the process of removing the photoresist after ion implantation, the spectral intensity of the emitted light generated by a specific element in the chamber is obtained at different sampling times, wherein the specific element is the element ion implanted during the ion implantation process on the wafer; Based on the spectral intensities corresponding to two adjacent sampling times, determine the change characteristic quantity of the spectral intensity at each sampling time; When the change characteristic quantity corresponding to the current sampling time meets the preset conditions, it is determined that the hardening layer removal process is close to the end point. Before the hardening layer removal process reaches the end point, the wafer is controlled to descend from the current position toward the heating base according to the preset relationship, so as to remove the remaining hardening layer of the photoresist at a higher temperature.
2. The removal method according to claim 1, characterized in that, The change feature is the rate of decrease in spectral intensity between two adjacent sampling times, and the change feature satisfies the following relationship: Q n =[S(t n-1 )- S(t n )]÷S(t n-1 ); where Q n Let S(t) be the change feature quantity corresponding to the nth sampling time. n ) represents the spectral intensity at the nth sampling time, where n is a positive integer.
3. The removal method according to claim 2, characterized in that, The preset condition includes that the change feature quantity corresponding to the current sampling time is greater than a preset value, and the preset value is a non-negative number.
4. The removal method according to claim 3, characterized in that, The preset value is greater than or equal to 5% and less than or equal to 20%.
5. The removal method according to claim 3, characterized in that, The preset conditions also include the time interval between the moment when the spectral intensity reaches its maximum value and the current sampling moment.
6. The removal method according to claim 5, characterized in that, The delay duration is calculated according to the following formula; T=k / Q max Where T is the delay duration; k > 0, and k is a constant; Q max The maximum value of the absolute value of the change characteristic quantity before the spectral intensity reaches its maximum value.
7. The removal method according to any one of claims 1 to 6, characterized in that, The preset relationship is that the descent displacement Δh of the wafer is equal to the product of the descent time Δt and the constant a, where a is greater than 0.
8. The removal method according to any one of claims 1 to 6, characterized in that, Before obtaining the spectral intensity of the emitted light generated by a specific element in the chamber at different sampling times, the removal method further includes: The wafer is placed on the bearing surface of the heating base, and after the preheating time is reached, the wafer is controlled to rise to the initial high position.
9. The removal method according to any one of claims 1 to 6, characterized in that, After controlling the wafer to descend from its current position toward the heating base according to a preset relationship to remove the hardened layer of the photoresist, the process further includes: When the change characteristic quantity corresponding to the current sampling time meets the hardening layer removal termination condition, the wafer is controlled to descend to the bearing surface of the heating base to remove the uncrosslinked layer of the photoresist.
10. A semiconductor process apparatus, characterized in that, include: chamber; A heating base, disposed within the cavity, has a support surface for supporting the wafer; The controller includes at least one processor and at least one memory, the memory storing a computer program, the processor executing the computer program to perform the removal method according to any one of claims 1 to 9.