Etching apparatus and etching endpoint detection method
By detecting the thickness of the film to be etched in real time in the etching apparatus and generating an etching endpoint signal, the problem of accurately determining the etching endpoint in wet etching processes is solved, achieving high-precision etching results and uniformity.
Patent Information
- Application Number
- CN202610487222.3
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2026-04-13
- Publication Date
- 2026-07-17
Smart Images
Figure CN122421697A_ABST
Abstract
Description
Technical Field
[0001] This disclosure relates to the field of semiconductor technology, and in particular to an etching apparatus and a method for detecting the etching endpoint. Background Technology
[0002] Wet etching is a process that uses a specific etching solution to chemically react with the material being etched, thereby achieving isotropic removal of the material. It is widely used in the semiconductor manufacturing industry.
[0003] However, current methods for detecting the endpoint of wet etching are usually based on etching time, judging whether the preset etching endpoint has been reached according to empirical etching rates. However, fluctuations in parameters such as the etching solution's lifetime, temperature, and concentration have a significant impact on the etching rate. These parameter fluctuations often lead to significant differences between the etching results and the expected results, making wet etching difficult to apply to processes with higher processing precision requirements. Summary of the Invention
[0004] The embodiments of this disclosure provide an etching apparatus and an etching endpoint detection method, which aim to solve the problem of low precision in wet etching processes.
[0005] To achieve the above objectives, the embodiments of this disclosure adopt the following technical solutions: On one hand, an etching apparatus is provided. The etching apparatus includes: an acid tank, a fixing mechanism, a sensor, and a controller. The acid tank is used to contain an etching solution for etching a wafer to be etched. The fixing mechanism is used to fix the wafer to be etched, the wafer including an etchable region having an etchable film layer. The sensor is configured to detect the thickness of the etchable film layer on the wafer in the etchable region. The controller is electrically connected to the sensor; the controller is configured to acquire the thickness of the etchable film layer; generate an etching endpoint signal if the thickness of the etchable film layer is less than or equal to a target thickness; the controller is further configured to, in response to the etching endpoint signal, control the etching apparatus to stop etching the wafer.
[0006] The etching apparatus provided in the above embodiments of this disclosure detects the thickness of the film layer to be etched in the etchable area on the wafer to be etched by a sensor and compares it with the target thickness. When the thickness of the film layer to be etched is less than or equal to the target thickness, an etching endpoint signal is generated, so that the etching result is as close as possible to the expected etching result, thereby improving the accuracy of the wet etching process.
[0007] In some embodiments, the wafer to be etched includes a co-etching wafer, and the fixing mechanism is used to fix the co-etching wafer; the sensor is specifically configured to detect the thickness of the film layer to be etched on the co-etching wafer; the controller is specifically configured to generate an etching endpoint signal when the thickness of the film layer to be etched on the thickness of the co-etching wafer is less than or equal to the target thickness.
[0008] In some cases, the etching apparatus provided in the above embodiments of this disclosure requires the formation of a specific pattern in the area to be etched on the wafer to be etched, making the detection of the thickness of the film layer to be etched in the area to be etched quite cumbersome. In this case, the etching process uses a patternless co-etching wafer as the detection object, so that the etching condition of the co-etching wafer reflects the etching condition of the product wafer, which is convenient for detection.
[0009] In some embodiments, the wafer to be etched further includes a product wafer, and the etching apparatus includes a plurality of the fixing mechanisms, which are spaced apart. Each fixing mechanism includes a first positioning groove and a second positioning groove, wherein the first positioning groove is used to fix the product wafer and the second positioning groove is used to fix the co-etched wafer.
[0010] The etching apparatus provided in the above embodiments of this disclosure, when the acid tank capacity is large and the number of wafers to be etched in a single processing is large, results in differences in the actual etching parameters at different locations within the acid tank, leading to varying degrees of etching on the wafers at different locations. By setting the product wafer and the co-etching wafer in the same fixing mechanism, the etching status of the co-etching wafer can reflect the etching status of all product wafers fixed in the fixing mechanism.
[0011] In some embodiments, the wafer to be etched further includes a product wafer, and the etching apparatus includes a plurality of fixing mechanisms, including a plurality of first fixing mechanisms and a plurality of second fixing mechanisms. The plurality of first fixing mechanisms include a first positioning groove for fixing the product wafer; the plurality of second fixing mechanisms include a second positioning groove for fixing the co-etched wafer; along the thickness direction of the product wafer, the plurality of second fixing mechanisms are arranged opposite to the plurality of first fixing mechanisms one by one.
[0012] The etching apparatus provided in the above embodiments of this disclosure allows the co-etched wafer to be independently transferred out of the etching solution, and the detection of the thickness of the co-etched wafer will not affect the etching of the product wafer.
[0013] In some embodiments, the wafer to be etched further includes a product wafer, and the acid tank includes a main tank and a secondary tank. The main tank is used to etch the product wafer; the secondary tank is connected to the main tank; and the secondary tank is used to etch the co-etched wafer.
[0014] The etching apparatus provided in the above embodiments of this disclosure places the product wafer in the main tank and the co-etching wafer in the secondary tank, and the main tank and the secondary tank are connected. It can be designed specifically for the secondary tank, such as opening a detection window, to facilitate the detection of the thickness of the co-etching wafer.
[0015] In some embodiments, the wafer to be etched further includes a product wafer, and the etching apparatus includes a plurality of acid tanks, the plurality of acid tanks including a first acid tank and a second acid tank that are isolated from each other; the first acid tank is used to etch the product wafer, and the second acid tank is used to etch the co-etched wafer.
[0016] The etching apparatus provided in the above embodiments of this disclosure places a product wafer in a first acid tank for etching and a co-etching wafer in a second acid tank for etching, with the first and second acid tanks isolated from each other. An etching solution with parameters different from those in the first acid tank can be configured in the second acid tank, and the etching status of the product wafer can be inferred by the mapping relationship between the reaction rate of the co-etching wafer with the etching solution in the second acid tank and the reaction rate of the product wafer with the etching solution in the first acid tank.
[0017] In some embodiments, the controller is specifically configured to, in response to the etching endpoint signal, cause the etching apparatus to stop etching the wafer to be etched after a first preset time; or, in response to the etching endpoint signal, cause the etching apparatus to immediately stop etching the wafer to be etched.
[0018] The etching apparatus provided in the above embodiments of this disclosure can, on the one hand, provide necessary over-etching compensation after the etching endpoint is reached, effectively overcoming the problem of process non-uniformity caused by differences in wafer surface morphology, uneven film thickness, or local fluctuations in etching rate; on the other hand, it can compensate for the defect that the sensor only detects a part of the wafer to be etched and cannot fully reflect the overall etching state of the wafer, thereby realizing the control of the overall film thickness and improving etching uniformity.
[0019] In some embodiments, the controller is further configured to re-acquire the thickness of the etchable film layer in the etchable region on the wafer to be etched if the etching time is less than a second preset time.
[0020] The etching apparatus provided in the above embodiments of this disclosure can effectively filter out false etching endpoint signals caused by signal fluctuations or unstable detection, and avoid the etching process from being terminated prematurely due to false alarms; at the same time, it ensures that the etching process has the necessary minimum process time (second preset time), and guarantees the basic achievement of etching depth.
[0021] In some embodiments, the etching apparatus further includes a transfer mechanism. The transfer mechanism is connected to the fixing mechanism; the transfer mechanism is configured to move between a first position and a second position, in which the fixing mechanism is located inside the acid tank and in the second position, the fixing mechanism is located outside the acid tank.
[0022] The etching apparatus provided in the above embodiments of this disclosure has a transfer mechanism that can, on the one hand, remove the wafer to be etched from the acid bath to cooperate with the sensor for thickness detection; on the other hand, it can respond to the instruction signal of the controller to remove the wafer to be etched from the acid bath in a timely manner to terminate the etching process.
[0023] On the other hand, an etching endpoint detection method is provided, including steps one, two, and three. Step one: Obtain the thickness of the film to be etched in the etchable region of the wafer to be etched. Step two: If the thickness of the film to be etched in the etchable region of the wafer to be etched is less than or equal to a target thickness, generate an etching endpoint signal. Step three: In response to the etching endpoint signal, stop etching the wafer to be etched.
[0024] In some embodiments, the wafer to be etched includes a co-etching wafer; step one specifically includes: obtaining the thickness of the film layer to be etched on the co-etching wafer; step two specifically includes: generating an etching endpoint signal when the thickness of the film layer to be etched on the co-etching wafer is less than or equal to the target thickness.
[0025] In some embodiments, step three specifically includes: in response to the etching endpoint signal, stopping the etching of the wafer to be etched after a first preset time; or, in response to the etching endpoint signal, immediately stopping the etching of the wafer to be etched.
[0026] In some embodiments, between step two and step three, the etching endpoint detection method further includes: if the etching time is less than a second preset time, re-acquiring the thickness of the film layer to be etched in the area to be etched on the wafer to be etched.
[0027] It is understood that the beneficial effects of the etching endpoint detection method provided in the above embodiments of this disclosure can be referred to the beneficial effects of the etching apparatus described above, and will not be repeated here. Attached Figure Description
[0028] To more clearly illustrate the technical solutions in this disclosure, the accompanying drawings used in some embodiments of this disclosure will be briefly described below.
[0029] Figure 1 This is a schematic diagram of the etching apparatus according to some embodiments; Figure 2 This is a schematic diagram of the structure of a wafer to be etched according to some embodiments; Figure 3 This is a schematic diagram of the structure of a product wafer according to some embodiments; Figure 4 This is a schematic diagram of the structure of a co-etched wafer according to some embodiments; Figure 5 This is a schematic diagram of the etching apparatus according to some other embodiments; Figure 6 This is a schematic diagram of the etching apparatus according to some other embodiments; Figure 7 This is a schematic diagram of the etching apparatus according to some other embodiments; Figure 8 This is a schematic diagram of the etching apparatus according to some other embodiments; Figure 9 This is a flowchart of an etching endpoint detection method according to some embodiments. Detailed Implementation
[0030] The technical solutions in some embodiments of this disclosure will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this disclosure, and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments provided in this disclosure are within the scope of protection of this disclosure.
[0031] In the description of this disclosure, it should be understood that the terms “center,” “upper,” “lower,” “front,” “rear,” “left,” “right,” “vertical,” “horizontal,” “top,” “bottom,” “inner,” and “outer,” etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing this disclosure and simplifying the description, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this disclosure.
[0032] Unless the context otherwise requires, throughout the specification and claims, the term "comprising" is interpreted as open-ended and encompassing, meaning "including, but not limited to." In the description of the specification, terms such as "one embodiment," "some embodiments," "exemplary embodiment," "exemplary," or "some examples," etc., are intended to indicate that a particular feature, structure, material, or characteristic associated with that embodiment or example is included in at least one embodiment or example of this disclosure. The illustrative representations of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics mentioned may be included in any suitable manner in any one or more embodiments or examples.
[0033] Hereinafter, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of embodiments of this disclosure, unless otherwise stated, "a plurality of" means two or more.
[0034] In describing some embodiments, the terms "coupled" and "connected," and their derivative expressions, may be used. For example, the term "connected" may be used in describing some embodiments to indicate that two or more components have direct physical or electrical contact with each other. Similarly, the term "coupled" may be used in describing some embodiments to indicate that two or more components have direct physical or electrical contact. However, the term "coupled" may also refer to two or more components that do not have direct contact with each other but still cooperate or interact with each other. The embodiments disclosed herein are not necessarily limited to the content of this document.
[0035] The use of “applies to” or “configured to” in this article implies an open and inclusive language that does not preclude applicability to or configuration to devices that perform additional tasks or steps.
[0036] In addition, the use of “based on” implies openness and inclusivity, because processes, steps, calculations or other actions “based on” one or more of the stated conditions or values may in practice be based on additional conditions or values beyond those stated.
[0037] As used herein, “about,” “approximately,” or “approximately” includes the stated value and the average value within an acceptable range of deviation from the given value, wherein the acceptable range of deviation is determined by a person skilled in the art taking into account the measurement under discussion and the error associated with the measurement of the given quantity (i.e., the limitations of the measurement system).
[0038] In this disclosure, the meanings of “on,” “above,” and “above” should be interpreted in the broadest possible sense, such that “on” means not only “directly on” something, but also includes “on” something with intermediate features or layers in between, and “above” or “above” means not only “above” or “above” something, but also “above” or “above” something without intermediate features or layers in between (i.e., directly on something).
[0039] This document describes exemplary embodiments with reference to cross-sectional views and / or plan views, which are idealized exemplary drawings. In the drawings, the thickness of layers and regions is enlarged for clarity. Therefore, variations in shape relative to the drawings are contemplated due to, for example, manufacturing techniques and / or tolerances. Thus, exemplary embodiments should not be construed as limited to the shapes of the regions shown herein, but rather include shape deviations due to, for example, manufacturing processes. For example, etched regions shown as rectangular would typically have curved features. Therefore, the regions shown in the drawings are schematic in nature, and their shapes are not intended to show the actual shapes of the regions of the device, nor are they intended to limit the scope of the exemplary embodiments.
[0040] Wet etching is a process that uses a specific chemical solution to react with the material being etched, achieving pattern transfer. Wet etching is generally exothermic and is isotropic, making it widely used in semiconductor processing. Currently, the endpoint of wet etching is mostly determined by etching time. This is calculated by dividing the preset etching thickness of the material by the etching rate in the etching solution. When the actual etching time equals the expected etching time, the etching endpoint is considered reached.
[0041] However, as the etching process progresses, changes in parameters such as the concentration of effective components in the etching solution and temperature can lead to fluctuations in the etching rate. This makes it difficult to determine the etching endpoint, resulting in differences between the etched product and the expected product, and poor consistency between different batches. Therefore, this disclosure provides an etching apparatus and an etching endpoint detection method to improve the accuracy of wet etching endpoint detection, thereby improving the processing precision of the wet etching process.
[0042] This disclosure provides an etching apparatus 1 for etching a wafer 2 to be etched. Figure 1 As shown, the etching apparatus 1 includes an acid tank 11, a fixing mechanism 12, a sensor 13, and a controller 14. The acid tank 11 is used to contain the etching solution for etching the wafer 2 to be etched. The fixing mechanism 12 is used to fix the wafer 2 to be etched, such as... Figure 2As shown, the wafer 2 to be etched includes an etchable region 21, which has an etchable film layer 210. Sensor 13 is configured to detect the thickness of the etchable film layer 210 in the etchable region 21 of the wafer 2. Controller 14 is electrically connected to sensor 13; controller 14 is configured to acquire the thickness of the etchable film layer 210 in the etchable region 21 of the wafer 2; generate an etching endpoint signal if the thickness of the etchable film layer 210 in the etchable region 21 of the wafer 2 is less than or equal to a target thickness; controller 14 is also configured to, in response to the etching endpoint signal, control etching apparatus 1 to stop etching the wafer 2.
[0043] The etching apparatus 1 described above uses a sensor 13 to detect the thickness of the etchable film layer 210 in the etchable area 21 on the wafer 2 to be etched. When the thickness of the etchable film layer 210 in the etchable area 21 on the wafer 2 to be etched is less than or equal to the target thickness, an etching endpoint signal is generated. This eliminates the problem in traditional wet etching processes where the etching endpoint is determined based on etching time, and the etching rate is affected by fluctuations in parameters such as etching solution life, temperature, and concentration, leading to inaccurate determination of the etching endpoint. This improves the accuracy of etching endpoint detection in wet etching processes, thereby improving the precision of the wet etching process.
[0044] In some embodiments, the sensor 13 detects the thickness of the etchable film layer 210 in the etchable region 21 on the wafer 2 to be etched. This can be achieved by the sensor 13 continuously detecting the thickness of the etchable region 21 on the wafer 2 to be etched in real time; alternatively, the sensor 13 can periodically detect the thickness of the etchable region 21 at preset time intervals. The preset time interval can be adjusted according to the etching rate of the etching process, the accuracy requirements of the target thickness, etc., and this embodiment does not specifically limit this.
[0045] As an example, sensor 13 continuously monitors the thickness of the region 21 to be etched in real time; when the thickness of the region 21 to be etched is detected to be equal to the target thickness, an etching endpoint signal is generated.
[0046] As an example, sensor 13 periodically detects the thickness of the film layer 210 to be etched in the etchable region 21 at preset time intervals, and sends the thickness information of the film layer 210 to be etched in the etchable region 21 to controller 14. Controller 14 compares the thickness of the film layer 210 to be etched in the etchable region 21 with the target thickness. When the thickness of the etchable region 21 equals the target thickness, an etching endpoint signal is generated. Alternatively, when approaching the etching endpoint, there may be a situation where the thickness of the film layer 210 to be etched in the etchable region 21 was greater than the target thickness in the previous detection, but less than the target thickness in the subsequent detection. At this time, although the thickness of the film layer 210 to be etched in the region 21 to be etched is not equal to the target thickness, the node where the thickness of the film layer 210 to be etched in the region 21 to be etched is equal to the target thickness is located between two detections. When the thickness of the film layer 210 to be etched in the region 21 to be etched is less than the target thickness, a signal indicating that the etching endpoint has been reached is generated.
[0047] In some possible implementations, the etching apparatus 1 further includes a transfer mechanism 15 connected to the fixing mechanism 12. The transfer mechanism 15 is configured to move the fixing mechanism 12 between a first position and a second position, wherein the first position is located inside the acid bath 11 and the second position is located outside the acid bath 11. On one hand, the transfer mechanism 15 can periodically remove the wafer 2 to be etched from the etching solution at preset time intervals to cooperate with the sensor 13 in detecting the thickness of the area 21 to be etched. On the other hand, the transfer mechanism 15 can remove the wafer 2 to be etched from the etching solution in response to a signal from the controller 14 to stop etching the wafer 2, thereby terminating the etching process. The connection between the transfer mechanism 15 and the fixing mechanism 12 can be a fixed connection or a detachable connection. When a detachable connection is used, a fixing mechanism 12 adapted to different sizes and specifications of the wafer 2 to be etched can be selected, improving the versatility of the etching apparatus 1. Meanwhile, in response to the highly corrosive environment of wet etching, the fixing mechanism 12 is prone to corrosion and wear and reduced positioning accuracy due to long-term contact with the etching solution. The adoption of a detachable connection allows for the individual disassembly and replacement of the fixing mechanism 12, reducing the maintenance cost of the etching device 1.
[0048] As an example, sensor 13 can be located outside the acid bath 11. Sensor 13 can be a clamp-on thickness gauge or a top-mounted thickness gauge. In the etching process, the transfer mechanism 15 removes the wafer 2 to be etched from the etching solution at preset time intervals, and performs contact detection on the thickness of the area 21 to be etched. By calculating the difference between the initial thickness of the area 21 to be etched on the wafer 2 and the thickness detected in this step, the thickness information of the film layer 210 to be etched is obtained. Sensor 13 can also be a spectral ellipsometer, which emits polarized light onto the surface of the wafer 2 to be etched, and calculates the thickness of the film layer 210 in the area 21 to be etched by detecting the change in the polarization state of the light reflected from the area 21 to be etched. Sensor 13 can also be a laser triangulation sensor, which calculates the thickness of the film layer 210 in the area 21 to be etched by detecting the displacement or optical path difference of the laser reflected from the area 21 to be etched. Sensor 13 can also be a high color depth, high dynamic range image sensor, used in conjunction with a broadband white light source, to acquire the grayscale or colorimetric changes of the white light interference color in the area to be etched 21, and obtain the thickness data of the film layer 210 to be etched in the area to be etched 21 by comparing with the calibration curve. Sensor 13 can also be an ultrasonic transducer, emitting high-frequency ultrasonic waves to the wafer 2 to be etched, and calculating the thickness of the film layer 210 to be etched in the area to be etched 21 by measuring the time difference and sound velocity of the ultrasonic echo on the surface of the film layer 210 to be etched near sensor 13 and the surface away from sensor 13.
[0049] For example, the transfer mechanism 15 repeatedly places and lifts the fixing mechanism 12, which carries the wafer 2 to be etched, into and out of the etching solution in the acid tank 11 at 5-second intervals. When the transfer mechanism 15 lifts the fixing mechanism 12 out of the etching solution, the sensor 13 (e.g., a reflective white light film thickness gauge) is activated and the thickness of the film layer 210 to be etched in the area 21 to be etched on the wafer 2 is detected by the probe to confirm the etching status of the wafer 2.
[0050] As an example, sensor 13 can also be disposed inside acid tank 11. Sensor 13 can be a sonar, which emits sound waves and receives the echo reflected by the area to be etched 21, and uses the propagation time of the sound waves in the etching solution to monitor the thickness change of the film layer 210 to be etched in the area to be etched 21.
[0051] In some possible cases, when the sensor 13 is located outside the acid tank 11, considering the environmental and process conditions in wet etching processes, such as etching solution splashing, acid mist corrosion, and etching solution vapor erosion, which can adversely affect the detection accuracy, operational stability, and service life of the sensor 13, the sensor 13 can be equipped with a suitable protective device to isolate the core detection unit of the sensor 13 from corrosive media and splashing droplets in the etching environment, while ensuring stable transmission of the detection signal and avoiding interference from the protective structure to the film thickness detection accuracy. The protective device includes, but is not limited to, a closed protective cover, an optical splash-proof window, a corrosion-resistant sealing sleeve, and an acid mist isolation curtain. For example, the optical film thickness detection sensor 13 can adopt a closed protective cover with a splash-proof window made of quartz or sapphire material with high light transmittance and etching solution corrosion resistance. This isolates splashing droplets and acid mist while ensuring distortion-free transmission of the optical detection path. The sensor 13 can also be equipped with an openable and closable protective window, which can be closed during non-detection periods for full protection and opened during detection periods to ensure detection accuracy.
[0052] When the sensor 13 is placed inside the acid tank 11, the sensor 13 can be equipped with a high-pressure resistant and corrosion-resistant sealing and protection structure to avoid corrosion damage to the sensor 13 by the etching solution, thereby improving the environmental adaptability and long-term operational reliability of the sensor 13 under complex wet etching conditions.
[0053] In some possible implementations, the wafer to be etched 2 includes a product wafer 20A and a co-etching wafer 20B, and the fixing mechanism 12 is used to fix the product wafer 20A and the co-etching wafer 20B. The sensor 13 is specifically configured to detect the thickness of the film layer 210 to be etched on the co-etching wafer 20B; the controller 14 is configured to generate an etching endpoint signal when the thickness of the film layer 210 to be etched on the co-etching wafer 20B is less than or equal to the target thickness.
[0054] In some embodiments, such as Figure 3 As shown, the area to be etched 21 needs to form a specific pattern, which may be small in area and difficult to be accurately detected by the sensor 13; or, the position of the area to be etched 21 changes with the positioning of the product wafer 20A, and since the wafer 2 to be etched is clamped by the fixing mechanism and immersed in the etching solution, it is difficult to ensure the precise positioning of each wafer 2 to be etched, resulting in the sensor 3's measurement point not falling accurately within the area to be etched 21 each time, thus making it difficult to achieve accurate measurement of the thickness of the area to be etched 21. In this case, a method can be adopted to simultaneously perform the etching process on the unpatterned co-etching wafer 20B and the product wafer 20A, such as... Figure 4As shown, the entire surface of the co-etching wafer 20B can be considered as the etching area 21. Without the need for precise positioning of the product wafer 20A, the thickness of the etchable film layer 210 on the co-etching wafer 20B can be detected. If the thickness of the etchable film layer 210 on the co-etching wafer 20B is less than or equal to the target thickness, an etching endpoint signal is generated. Therefore, the etching degree of the etchable film layer 210 in the etching area 21 on the product wafer 20A can be reflected by the relatively easily detectable thickness of the etchable film layer 210 on the co-etching wafer 20B, reducing the difficulty of thickness detection.
[0055] In some embodiments, the thickness of the etchable film layer 210 on the co-etch wafer 20B is greater than the thickness of the etchable film layer 210 in the etchable region 21 of the product wafer 20A, so as to achieve effective thickness detection of the etchable film layer 210 on the co-etch wafer 20B. A single co-etch wafer 20B can be used in one or more etching processes. For example, when the target etching thickness of a single wet etching process of the product wafer 20A is 300nm, a co-etch wafer 20B with a total thickness of 1μm for the etchable monitoring film layer can be configured. This co-etch wafer 20B can continuously complete the endpoint monitoring of the product etching process twice, retaining sufficient safety margin after a cumulative etching thickness of 600nm, avoiding detection failure caused by the monitoring film layer being etched through. When the target etching thickness of a single etching process of the product wafer 20A is 800nm, the same co-etch wafer 20B with a 1μm thick film can complete the etching endpoint monitoring of the process once.
[0056] In some embodiments, the size of the co-etched wafer 20B may be the same as or different from the size of the product wafer 20A, and this disclosure does not specifically limit this aspect.
[0057] Some possible implementations, such as Figure 5 As shown, the etching apparatus 1 includes multiple fixing mechanisms 12, which are spaced apart. Each fixing mechanism 12 includes a first positioning groove 121 and a second positioning groove 122. The first positioning groove 121 is used to fix the product wafer 20A, and the second positioning groove 122 is used to fix the co-etching wafer 20B.
[0058] In some embodiments, the acid tank 11 has a large capacity, and the number of wafers 2 to be etched in a single process is large. The parameters of the etching solution at different positions in the acid tank 11 may differ, resulting in different etching degrees for the wafers 2 to be etched at different positions within the acid tank 11. However, wafers 2 to be etched fixed by the same fixing mechanism 12 are close together, and their surrounding environment can be considered approximately the same, thus their etching conditions can be considered approximately the same. In this case, a first positioning groove 121 and a second positioning groove 122 are provided within the same fixing mechanism 12. By detecting the thickness of the film layer 210 to be etched on the co-etched wafer 20B fixed by the second positioning groove 122, the etching condition of the product wafer 20A fixed by the first positioning groove 121 within the fixing mechanism 12 can be reflected, thereby achieving the detection of the etching endpoint of wafers 2 to be etched at different positions within the acid tank 11.
[0059] Furthermore, the co-etching wafer 20B, located in the same fixed mechanism 12, enters the etching environment synchronously with the product wafer 20A, so that the co-etching wafer 20B and the product wafer 20A are in the same etching condition. The thickness information of the film layer 210 to be etched on the co-etching wafer 20B detected by the sensor 13 can be equivalent to the actual etching progress of the product wafer 20A, thereby improving the accuracy of etching endpoint detection.
[0060] Some possible implementations, such as Figure 6 As shown, the etching apparatus 1 includes multiple fixing mechanisms 12, including a first fixing mechanism 12A and a second fixing mechanism 12B. The first fixing mechanism 12A includes a first positioning groove 121 for fixing the product wafer 20A; the second fixing mechanism 12B includes a second positioning groove 122 for fixing the co-etching wafer 20B. Along the thickness direction Y of the product wafer 20A, the multiple second fixing mechanisms 12B are arranged opposite to the multiple first fixing mechanisms 12A.
[0061] In some embodiments, such as Figure 6 As shown, the etching apparatus 1 includes a plurality of fixing mechanisms 12 arranged at intervals along a first direction X. The plurality of fixing mechanisms 12 include a first fixing mechanism 12A and a second fixing mechanism 12B. The first fixing mechanism 12A includes a first positioning groove 121 for fixing the product wafer 20A; the second fixing mechanism 12B includes a second positioning groove 122 for fixing the co-etching wafer 20B. Thus, the first fixing mechanism 12A and its fixed product wafer 20A, and the second fixing mechanism 12B and its fixed co-etching wafer 20B, can all be individually removed from the etching solution. When it is necessary to detect the thickness of the film layer 210 to be etched on the co-etching wafer 20B, the second fixing mechanism 12B and its fixed co-etching wafer 20B can be individually removed from the etching solution for thickness detection without interrupting the etching process of the product wafer 20A.
[0062] In some possible implementations, the etching apparatus 1 can be flexibly configured with appropriate detection schemes according to the process accuracy requirements, tank structure, and detection scenario of wet etching, so as to further improve the accuracy, stability and process adaptability of film thickness detection.
[0063] As an example, the detection can employ a collaborative detection mode combining multiple film thickness detection methods, or a single film thickness detection method combined with multiple acquisition timing sequences and multiple sets of detection parameters in a single-method, multi-mode detection mode. Multiple sensors 13 can be deployed simultaneously to complete film thickness detection at different points and in different areas within the acid bath 11. Alternatively, a single sensor 13 can move between preset detection positions according to process requirements to complete time-sharing film thickness detection in multiple areas. A single integrated multi-purpose sensor 13 can also be used to achieve parallel detection of one or more film thickness detection methods, balancing detection efficiency and accuracy. These flexible and configurable detection schemes are adaptable to various wet etching process scenarios with different sizes of wafers 2 to be etched, different batch sizes, and different accuracy requirements. They can effectively filter out random errors from single detection methods, further improving the reliability of etching endpoint determination and the versatility of the etching apparatus 1.
[0064] Some possible implementations, such as Figure 7 As shown, the acid tank 11 includes a main tank 111 and a secondary tank 112. The main tank 111 is used to etch the product wafer 20A, and the secondary tank 112 is connected to the main tank 111 and is used to etch the co-etch wafer 20B. Placing the co-etch wafer 20B in a separate secondary tank 112 ensures that the thickness detection operation of the film layer 210 to be etched on the co-etch wafer 20B will not interfere with the continuous etching process of the product wafer 20A in the main tank 111. This reduces the impact of the thickness detection operation on the flow field and stability of the etching solution in the main tank 111, and reduces the risk of collision and contamination between the wafers 2 to be etched during the detection process. At the same time, the setting of the secondary tank 112 does not occupy the loading space of the product wafer 20A in the main tank 111, and does not sacrifice the processing capacity of the etching apparatus 1.
[0065] Some possible implementations, such as Figure 8 As shown, the etching apparatus 1 includes a plurality of acid tanks 11, and the plurality of acid tanks 11 include a first acid tank 11A and a second acid tank 11B that are isolated from each other; the first acid tank 11A is used to etch the product wafer 20A, and the second acid tank 11B is used to etch the co-etched wafer 20B.
[0066] In some embodiments, the first acid tank 11A and the second acid tank 11B are filled with etching solutions of identical composition and concentration. The material of the film layer 210 to be etched on the co-etched wafer 20B is completely identical to the material of the film layer 210 to be etched in the etchable area 21 of the product wafer 20A. The etching rates of the two are perfectly matched, and the thickness detection data of the film layer 210 to be etched on the co-etched wafer 20B can directly and equivalently characterize the actual etching progress of the product wafer 20A. The first acid tank 11A and the second acid tank 11B are isolated from each other, which can avoid the interference of the etching solution flow field changes caused by the co-etched wafer 20B moving into or out of the second acid tank 11B or the exchange of etching solution between the acid tanks 11 during the detection of the co-etched wafer 20B, thus ensuring the stability of the etching of the product wafer 20A.
[0067] In other embodiments, the first acid tank 11A and the second acid tank 11B are filled with etching solutions of different compositions and concentrations. The material of the film layer 210 to be etched on the co-etched wafer 20B can be the same as or different from the material of the film layer 210 to be etched in the area to be etched on the product wafer 20A. The controller is pre-calibrated with two sets of etching rate difference parameters of the etching solutions under corresponding process conditions, as well as etching selectivity parameters of different film layer materials. Based on the real-time thickness detection data of the film layer 210 to be etched on the co-etched wafer 20B, the actual thickness and etching progress of the film layer 210 to be etched in the area 21 to be etched on the product wafer 20A can be accurately calculated, thereby achieving accurate determination of the etching endpoint.
[0068] For example, when product wafer 20A needs to etch an ultra-thin SiN film, the thickness change of the ultra-thin film in a single etching is extremely small, making direct detection difficult and inaccurate. In this case, an etching solution with a faster etching rate for SiO2 film can be selected in the second acid tank 11B. The co-etched wafer 20B uses a wafer with SiO2 film 210 to be etched. By utilizing the characteristics of fast etching rate and easy detection of film thickness change of SiO2 film, the tiny film thickness change of product wafer 20A can be amplified into a significant film thickness change of co-etched wafer 20B by using a pre-calibrated etching selectivity ratio of SiO2 and SiN film, thereby greatly improving the accuracy of determining the end point of ultra-thin film etching.
[0069] For example, when the film layer 210 to be etched on the product wafer 20A is a special functional film layer with a complex growth process and high preparation cost, the co-etching wafer 20B can be a substitute film layer 210 with a simple growth process and low cost. With the etching solution in the second acid tank 11B that matches the substitute film layer 210, the etching progress of the product wafer 20A can be monitored through a pre-calibrated etching rate correspondence. Alternatively, a dilute etching solution with a lower concentration can be filled in the second acid tank 11B to slow down the etching consumption of the film layer 210 on the co-etching wafer 20B, realize more reuse of the co-etching wafer 20B, and significantly reduce the usage cost of the co-etching wafer 20B.
[0070] In some possible implementations, the etching process can be divided into two stages: a rapid etching stage and a precise etching stage. The rapid etching stage aims to quickly complete most of the etching, with a fast etching rate, and does not require precise monitoring of the thickness of the film layer 210 in the etched area 21. The precise etching stage aims to precisely control the thickness of the film layer 210 within the etched area 21, with a gradual and controllable etching rate, requiring continuous and precise monitoring of the film layer thickness in the etched area 21. Based on this, electrochemical monitoring sensors can be used as the main detection method during the rapid etching stage to continuously monitor the etching intensity, process, and changes in etching product concentration within the acid bath 11 to track the etching process. This eliminates the need for frequent monitoring of the wafer 2 to be etched, which would reduce etching efficiency. During the precision etching stage, due to the slower etching rate, the monitoring accuracy of electrochemical monitoring sensors is insufficient to reflect minute changes in film thickness on the wafer 2 to be etched. In this case, a co-etching wafer 20B can be introduced into the acid bath 11 and etched simultaneously with the product wafer 20A. The thickness change of the film 210 to be etched on the co-etching wafer 20B can be detected to reflect the thickness of the film 210 to be etched in the etched area 21 on the product wafer 20A, thus accurately determining whether the etching endpoint has been reached.
[0071] As an example, a special wafer with an integrated electrochemical sensing unit can be used as a detection device for the rapid etching stage. The special wafer and the wafer 20B are simultaneously deployed in the acid tank 11. During the first half of the etching process, the controller 14 controls the product wafer 20A and the wafer 20B to be fully immersed in the etching solution, with the signal from the special wafer as the core monitoring basis. When the signal from the special wafer reaches the preset trigger condition, the controller 14 determines that the etching has entered the precise etching stage, and then controls the transfer mechanism 15 to transfer the wafer 2 to be etched out of the etching solution according to the preset time interval. At the same time, the thickness of the film layer 210 to be etched on the wafer 20B is detected. If the thickness of the film layer 210 to be etched on the wafer 20B is less than or equal to the target thickness, an etching endpoint signal is generated.
[0072] In some possible implementations, the controller 14 is specifically configured to, in response to an etching endpoint signal, stop etching the wafer 2 to be etched after a first preset time; or, in response to an etching endpoint signal, immediately stop etching the wafer 2 to be etched.
[0073] In some embodiments, the product has stringent requirements for the critical dimension control of the film layer 210 to be etched in the etchable area 21 and extremely low over-etching redundancy. The controller 14 responds to the etching endpoint signal and causes the etching device 1 to immediately stop etching the wafer 2 to be etched, so as to ensure that the etching accuracy meets the product requirements.
[0074] In other embodiments, for products with high aspect ratio trench or via structures, large pattern density differences, and uneven etching rates within the acid tank 11 during large-size wafer batch processing, where it is necessary to ensure sufficient etching across the entire etchable area 21, the controller 14 responds to the etching endpoint signal and stops the etching device 1 after a first preset time. By using controlled over-etching based on the actual detected etching endpoint as the trigger, the risk of product failure due to insufficient local etching is completely eliminated. At the same time, it avoids the inherent accuracy defects of traditional timed etching, which blindly sets the over-etching time in advance and cannot adapt to fluctuations in etching solution parameters.
[0075] In some embodiments, the first preset duration is calculated by multiplying the actual completed etching time from the start of the etching process to the controller 14 receiving the etching endpoint signal by a pre-calibrated fixed scaling factor. This scaling factor is determined comprehensively based on the etching uniformity, structural characteristics, and over-etching requirements of the process. For example, the scaling factor is 5% to 10% for conventional uniform etching and simple pattern structures, and 10% to 30% for high aspect ratio structures and batch multi-wafer processing. Simultaneously, the maximum value of the scaling factor must meet the safety constraints of the etching system selection ratio to ensure that the etching loss of the substrate or barrier layer during over-etching does not exceed the critical damage thickness allowed by the process.
[0076] In some possible implementations, after issuing a signal indicating that the etching endpoint has been reached, the etching apparatus 1 can continuously monitor and control the etching-related process parameters. The process parameters after the etching endpoint signal is issued can be set to be different from the process parameters before the etching endpoint signal is issued, so as to ensure the sufficiency of etching of the wafer 2 to be etched and to smoothly and controllably complete the etching process. Among them, the adjustable process parameters after the etching endpoint signal is issued include: the interval at which the wafer 2 to be etched is transferred out of the etching solution, the height at which it leaves the etching solution surface, the oscillation frequency, the oscillation distance, the acid flow rate, the acid circulation speed, the etching solution temperature, and the concentration of each component of the mixed etching solution, etc., which can be adjusted according to specific process requirements. This embodiment of the present disclosure does not specifically limit these parameters.
[0077] In some possible implementations, the controller 14 is further configured to re-acquire the thickness of the etchable film layer 210 in the etchable region 21 on the wafer 2 to be etched if the etching time is less than a second preset time. By setting a second preset time, invalid endpoint trigger signals in the early stages of the etching process are filtered out, avoiding the controller 14 from erroneously triggering a shutdown when the etching is far from reaching the target requirements due to abnormal factors such as the initial oxide layer or particulate impurities on the surface of the wafer 2 to be etched, transient reaction fluctuations of the etching solution, and sensor detection noise. This ensures the integrity of the etching operation and the stability of the process. The second preset time can be set, for example, by calculating the theoretical total etching time as the ratio of the target total etching thickness to the steady-state etching rate, and taking 50% to 80% of the theoretical total etching time as the second preset time. This ensures that it is always earlier than the theoretical etching endpoint arrival time, which can fully cover the risk window of erroneous triggering in the first half of the etching process without interfering with the determination of the normal etching endpoint.
[0078] Another aspect of this disclosure provides a method for detecting the etching endpoint, such as... Figure 9 As shown, the etching endpoint detection method includes the following steps: S1. Obtain the thickness of the film layer 210 to be etched in the etchable region 21 on the wafer 2 to be etched.
[0079] In the above steps, the sensor 13 can detect the thickness of the etchable film layer 210 in the etchable area 21 on the wafer 2 to be etched, and then send the information containing the thickness of the etchable film layer 210 to the controller 14. The controller 14 receives the information and parses it to obtain the thickness of the etchable film layer 210 in the etchable area 21 on the wafer 2 to be etched.
[0080] S2. When the thickness of the film layer 210 to be etched in the etchable region 21 on the wafer 2 to be etched is less than or equal to the target thickness, an etching endpoint signal is generated. In the above steps, after receiving the thickness information of the film layer 210 to be etched and obtaining the thickness of the film layer 210 in the etchable region 21 on the wafer 2 to be etched, the controller 14 can compare the thickness of the film layer 210 in the etchable region 21 on the wafer 2 to be etched with the target thickness. If the thickness of the film layer 210 in the etchable region 21 on the wafer 2 to be etched is less than or equal to the target thickness, an etching endpoint signal can be generated.
[0081] S3. In response to the etching endpoint signal, stop etching the wafer 2 to be etched.
[0082] In the above steps, the controller 14 responds to the etching endpoint signal and controls the etching device 1 to stop etching the wafer 2 to be etched.
[0083] In some possible implementations, the wafer to be etched 2 includes a product wafer 20A and a co-etching wafer 20B. S1 specifically includes: obtaining the thickness of the film layer 210 to be etched on the co-etching wafer 20B. For example, sensor 13 can detect the thickness of the film layer 210 to be etched on the co-etching wafer 20B and send the thickness information to controller 14. Controller 14 receives the thickness information and obtains the thickness of the film layer 210 to be etched on the co-etching wafer 20B. S2 specifically includes: generating an etching endpoint signal if the thickness of the film layer 210 to be etched on the co-etching wafer 20B is less than or equal to a target thickness. For example, after receiving the thickness information and obtaining the thickness of the film layer 210 to be etched on the co-etching wafer 20B, controller 14 compares the thickness of the film layer 210 to be etched on the co-etching wafer 20B with the target thickness. If the thickness of the film layer 210 to be etched on the co-etching wafer 20B is less than or equal to the target thickness, an etching endpoint signal is generated.
[0084] In some possible implementations, S3 specifically includes: in response to the etching endpoint signal, stopping the etching of the wafer 2 to be etched after a first preset time; or, in response to the etching endpoint signal, immediately stopping the etching of the wafer 2 to be etched. For example, in response to the etching endpoint signal, the controller 14 controls the etching apparatus 1 to stop etching the wafer 2 to be etched after a first preset time; or, in response to the etching endpoint signal, the controller 14 controls the etching apparatus 1 to immediately stop etching the wafer 2 to be etched.
[0085] In some possible implementations, between S2 and S3, the thickness of the film layer 210 to be etched in the etchable region 21 on the wafer 2 to be etched is re-acquired if the etching time is less than the second preset time. For example, the controller 14 may also record the etching time, and if the etching time is less than the second preset time, it may not respond to the etching endpoint signal generated in S2 and re-acquire the thickness of the film layer 210 in the etchable region 21 on the wafer 2 to be etched.
[0086] The etching endpoint detection method provided in the above embodiments of this disclosure can achieve the same beneficial effects as the etching apparatus 1 described above, and will not be repeated here.
[0087] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.
Claims
1. An etching apparatus, characterized in that, include: Acid tanks are used to hold etching solution for etching the wafers to be etched. A fixing mechanism is used to fix the wafer to be etched, the wafer to be etched includes an area to be etched, and the area to be etched has a film layer to be etched; A sensor is configured to detect the thickness of the film layer to be etched in the etched region on the wafer to be etched; The controller is electrically connected to the sensor; The controller is configured to acquire the thickness of the film layer to be etched; generate an etching endpoint signal when the thickness of the film layer to be etched is less than or equal to a target thickness; the controller is further configured to control the etching apparatus to stop etching the wafer to be etched in response to the etching endpoint signal.
2. The etching apparatus according to claim 1, characterized in that, The wafer to be etched includes a co-etched wafer, and the fixing mechanism is also used to fix the co-etched wafer; The sensor is specifically configured to detect the thickness of the film layer to be etched on the co-etched wafer; The sensor or controller is specifically configured to generate an etching endpoint signal when the thickness of the film to be etched on the co-etched wafer is less than or equal to the target thickness.
3. The etching apparatus according to claim 2, characterized in that, The wafer to be etched also includes a product wafer. The etching apparatus includes a plurality of fixing mechanisms, which are spaced apart. Each fixing mechanism includes a first positioning groove and a second positioning groove. The first positioning groove is used to fix the product wafer, and the second positioning groove is used to fix the co-etched wafer.
4. The etching apparatus according to claim 2, characterized in that, The wafer to be etched further includes a product wafer, and the etching apparatus includes a plurality of the fixing mechanisms, the plurality of fixing mechanisms including: Multiple first fixing mechanisms, including a first positioning groove, the first positioning groove being used to fix the product wafer; Multiple second fixing structures include a second positioning groove for fixing the co-etched wafer; along the thickness direction of the product wafer, multiple second fixing mechanisms are arranged opposite to multiple first fixing mechanisms.
5. The etching apparatus according to claim 2, characterized in that, The wafer to be etched also includes a product wafer, and the acid tank includes: The main groove is used for etching the product wafer; The secondary groove is connected to the main groove; the secondary groove is used to etch the co-etched wafer.
6. The etching apparatus according to claim 2, characterized in that, The wafer to be etched also includes a product wafer, which includes a plurality of acid tanks, the plurality of acid tanks including a first acid tank and a second acid tank that are isolated from each other; the first acid tank is used to etch the product wafer, and the second acid tank is used to etch the co-etched wafer.
7. The etching apparatus according to claim 1, characterized in that, The controller is specifically configured to, in response to the etching endpoint signal, after a first preset time period, cause the etching device to stop etching the wafer to be etched; or, in response to the etching endpoint signal, immediately cause the etching device to stop etching the wafer to be etched.
8. The etching apparatus according to claim 1, characterized in that, The controller is also configured to re-acquire the thickness of the film layer to be etched in the etchable region on the wafer to be etched if the etching time is less than a second preset time.
9. The etching apparatus according to claim 1, characterized in that, Also includes: A transfer mechanism is connected to the fixing mechanism; the transfer mechanism is configured to move between a first position and a second position, in which the fixing mechanism is located inside the acid tank and in the second position, the fixing mechanism is located outside the acid tank.
10. A method for detecting the end point of etching, characterized in that, An etching apparatus used in any one of claims 1 to 9, comprising: Step 1: Obtain the thickness of the film layer to be etched in the area to be etched on the wafer to be etched; Step 2: If the thickness of the film layer to be etched in the etchable region on the wafer to be etched is less than or equal to the target thickness, generate an etching endpoint signal; Step 3: In response to the etching endpoint signal, stop etching the wafer to be etched.
11. The etching endpoint detection method according to claim 10, characterized in that, The wafer to be etched includes a co-etched wafer; Step one specifically includes: obtaining the thickness of the film layer to be etched on the co-etching wafer; Step two specifically includes: generating an etching endpoint signal when the thickness of the film to be etched on the co-etched wafer is less than or equal to the target thickness.
12. The etching endpoint detection method according to claim 10, characterized in that, Step three specifically includes: In response to the etching endpoint signal, etching of the wafer to be etched is stopped after a first preset time; or, in response to the etching endpoint signal, etching of the wafer to be etched is stopped immediately.
13. The etching endpoint detection method according to claim 10, characterized in that, Between step two and step three, the etching endpoint detection method further includes: If the etching time is less than the second preset time, the thickness of the film layer to be etched in the area to be etched on the wafer to be etched is obtained again.