Method for removing film layer on surface of wafer by using laser effect

Abstract

The invention discloses a method for removing a film layer on the surface of a wafer by using a laser effect. The method comprises collaborative design of a multi-stage modulation pulse laser, an auxiliary airflow regulation and control device, an optical detection feedback system and a special clamp. By optimizing laser parameters and introducing high-speed inert gas flow and closed-loop feedback control, accurate removal of a film layer is realized, and meanwhile, thermal stress and residual risk are reduced. The special clamp ensures wafer stability and reduces mechanical stress damage. The whole process is divided into a pretreatment stage, a main processing stage and a post-treatment stage which are uniformly managed by a central control system. According to the method, the removing efficiency and quality can be remarkably improved, and the requirements of modern semiconductor manufacturing for high efficiency and high reliability are met.

Description

Technical Field

[0001] The present invention relates to the field of semiconductor manufacturing and precision processing technology, and in particular to a method for removing a film layer on a wafer surface by utilizing laser action. Background Art

[0002] With the continuous advancement of semiconductor manufacturing technology, the feature size of chips has gradually shrunk to 32nm, 22nm and even below 14nm. In these advanced processes, the treatment process of the film layer on the surface of the wafer is crucial to ensuring device performance and yield. For example, during the wafer manufacturing process, residual or uneven removal of the film layer may cause defects, thereby affecting the reliability of the final product. Therefore, the development of efficient and low-damage film removal methods has become a research focus. Although existing technologies can achieve a certain degree of film removal effect, when using lasers to remove the film layer on the surface of the wafer, there are still problems such as film residue and possible thermal damage or stress to the wafer substrate. In addition, in order to meet more stringent requirements, factors such as the accuracy of the removal process and how to simplify the process flow also need to be considered.

[0003] After searching, a wafer, its manufacturing method, and electronic device with publication number CN109427614B were disclosed, and the publication date is December 29, 2020. This patent provides a method for achieving precise marking on the surface of a wafer by forming a linear film mark on the side of a silicon ingot and combining it with laser marking. This method avoids the etching step, thereby reducing the risk of wafer breakage or contamination during the marking preparation process. However, this technical solution mainly focuses on the formation of wafer surface marks, rather than directly involving the removal process of the film layer on the wafer surface. Therefore, it does not solve the problem of film layer residue that may occur during the film layer removal process, nor does it fully consider the thermal damage or stress effects that may be caused by the laser action on the wafer substrate.

[0004] After searching, a method for stripping a solid thin film based on a chemical reaction on the substrate surface was disclosed with a publication number of CN114188270B, and the publication date is November 22, 2024. This patent prepares a passivation layer on the surface of a semiconductor substrate and injects ions, and combines laser irradiation to separate the substrate at the ion implantation layer, thereby achieving the stripping of a solid thin film. This method can effectively reduce the introduction of traditional bonding processes and alleviate the problems of film deformation and cracking. However, this technical solution mainly focuses on the overall stripping of solid films, rather than the local removal of film layers on the surface of wafers. In addition, this method relies on ion implantation and chemical reaction processes, and the process complexity is relatively high, and the energy control requirements of laser irradiation are relatively strict. Any slight inappropriateness may cause damage to the substrate material or incomplete stripping of the film layer, thereby affecting device performance and production efficiency.

[0005] The above issues indicate that existing wafer surface film processing technologies still have room for improvement in terms of film removal accuracy, process optimization, and wafer substrate protection. Therefore, the present invention aims to provide a method for removing wafer surface films using lasers. This method optimizes the removal process, reduces the risk of film residue, and minimizes thermal damage and stress to the wafer substrate. It also simplifies the operational process, thus meeting the demands of modern semiconductor manufacturing for efficient, high-quality wafer processing. Summary of the Invention

[0006] The purpose of the present invention is to provide a method for removing a film layer on a wafer surface by using laser action, so as to solve the problems raised in the above background technology.

[0007] To achieve the above object, the present invention provides the following technical solution: a method for removing a film layer on a wafer surface by using laser action, comprising the following steps: A laser emitting unit is provided, wherein the laser emitting unit adopts a multi-level modulated pulse laser, the output wavelength of which ranges from 200nm to 1100nm, and the pulse width is adjustable between 10fs and 100ns; The focus position of the laser beam is adjusted by a dynamic focusing lens group, wherein the dynamic focusing lens group is composed of multiple aspheric lenses and is driven by a stepping motor to achieve displacement; An auxiliary airflow control device is introduced, which includes an annular nozzle array and a gas mixing chamber. The annular nozzle array is arranged around the laser beam outlet and blows high-speed inert gas toward the wafer surface; An optical detection feedback system is provided, wherein the optical detection feedback system includes a high-resolution CCD camera and an integrated signal processing unit for real-time monitoring of the thickness change of the film layer on the wafer surface and adjusting the laser power and scanning path; A special fixture is used to fix the wafer, which includes a base, a vacuum adsorption plate and a flexible buffer layer. The base is made of high-strength aluminum alloy material. The vacuum adsorption plate is connected by a micro vacuum pump to form a negative pressure environment. The flexible buffer layer is located between the vacuum adsorption plate and the wafer and has a thickness of 0.5mm to 2mm.

[0008] Preferably, the beam shaping module of the laser emitting unit is equipped with a dynamic focusing lens group, which is driven by a stepper motor and fixed to the laser body by a threaded connection. The stepper motor is connected to the lens group through a gear transmission mechanism to accurately control the displacement.

[0009] Preferably, the annular nozzle array of the auxiliary airflow control device is connected and fixed to the housing of the laser emitting unit through a flange, and the gas mixing chamber controls the proportion of different gas components through a proportional valve, which is electromagnetically driven and communicates with the central control system.

[0010] Preferably, a high-resolution CCD camera of the optical detection feedback system is mounted on a bracket near the laser head, the spectrometer is located in the laser beam path and connected to the bracket through a mirror frame, and the signal processing unit is connected to the CCD camera through a data cable and has a built-in algorithm module.

[0011] Preferably, the bottom of the base of the special fixture is fixed to the workbench by bolts, the top is provided with a groove for installing the vacuum adsorption plate, and the flexible buffer layer is fixed to the vacuum adsorption plate by bonding.

[0012] Preferably, the entire removal process is divided into three stages: pre-processing, main processing and post-processing. In the pre-processing stage, a low-power laser is used to perform a preliminary scan on the wafer surface to determine the film layer distribution and thickness information.

[0013] Preferably, in the main processing stage, laser parameters are set according to the data obtained in the preprocessing stage and a laser beam is emitted through the laser emitting unit, while the auxiliary air flow control device is started to blow high-speed inert gas to the wafer surface.

[0014] Preferably, in the post-processing stage, the wafer surface is cleaned a second time by an ultrasonic cleaning device to remove any trace residues that may exist. The ultrasonic cleaning device communicates with the central control system and completes the cleaning operation according to a preset program.

[0015] Preferably, the high-speed inert gas is nitrogen or argon, and each nozzle of the annular nozzle array is inclined and forms a certain angle with the wafer surface to ensure that the high-speed gas flow covers the entire processing area.

[0016] Compared to existing technologies, this invention offers the following advantages: Through the synergistic effects of a multi-stage modulated pulsed laser, an auxiliary airflow control device, an optical detection feedback system, and a specialized fixture, it addresses existing issues such as low film removal efficiency, high residue rates, and wafer substrate damage. Compared to traditional methods, this invention offers greater process flexibility and reliability, meeting the demands of modern semiconductor manufacturing for efficient, high-quality wafer processing. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 Schematic diagram of the system structure for laser removal of wafer surface film layers according to an embodiment of the present invention; Figure 2 Schematic diagram of the structure of a special clamp in an embodiment of the present invention.

[0018] In the figure: 1. Laser emission unit; 2. Auxiliary airflow control device; 3. Optical detection feedback system; 4. Special fixture; 5. Base; 6. Vacuum adsorption disk; 7. Flexible buffer layer. DETAILED DESCRIPTION

[0019] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0020] The present invention provides a method for removing the film layer on the surface of the wafer by using laser action. The core of the method is to achieve accurate removal of the film layer on the surface of the wafer by optimizing laser parameters, introducing auxiliary airflow control and setting multiple feedback mechanisms. Figure 1 and Figure 2 The specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings and structural relationships shown.

[0021] like Figure 1 As shown, the entire system includes a laser emitting unit 1, an auxiliary airflow control device 2, an optical detection feedback system 3 and a special fixture 4. These components together constitute a complete laser processing platform for removing the film layer on the surface of the wafer. The laser emitting unit 1 is located at the top of the system, with its output end facing the wafer surface, and is used to emit a modulated pulsed laser beam. The auxiliary airflow control device 2 is arranged around the outlet of the laser emitting unit 1, and includes an annular nozzle array and a gas mixing chamber for blowing high-speed inert gas to the wafer surface. The optical detection feedback system 3 is installed near the laser head, and captures the reflected light signal from the wafer surface through a spectrometer and monitors the film removal status in real time. The special fixture 4 is fixed on the workbench to support and fix the wafer to ensure its stability during the processing.

[0022] The laser emitting unit 1 is the core energy source of the entire system. It uses a multi-level modulated pulse laser inside, with an output wavelength range of 200nm to 1100nm and a pulse width adjustable between 10fs and 100ns. The laser's beam shaping module is equipped with a dynamic focusing lens group, which consists of multiple aspheric lenses and is driven by a stepper motor to achieve real-time adjustment of the focal position. The dynamic focusing lens group is fixed to the laser body by a threaded connection, and the stepper motor is connected to the lens group through a gear transmission mechanism, thereby accurately controlling the displacement of the lens group. This design ensures that the laser beam can form a uniform energy distribution on the wafer surface, while performing high-precision scanning operations on local areas.

[0023] The annular nozzle array of the auxiliary airflow control device 2 is arranged directly around the laser beam outlet, and the nozzle array is fixed to the outer shell of the laser emitting unit 1 through a flange. The gas mixing chamber is located behind the annular nozzle array, and the proportion of different gas components is controlled by a proportional valve to generate the best airflow combination. The proportional valve is electromagnetically driven and communicates with the central control system to adjust the gas flow and composition according to real-time feedback information. Each nozzle of the annular nozzle array is tilted and forms a certain angle with the wafer surface to ensure that the high-speed airflow can cover the entire processing area. The outlet of the gas mixing chamber is connected to the annular nozzle array through a pipe, and the inner wall of the pipe is polished to reduce the gas flow resistance.

[0024] The core components of the optical inspection and feedback system 3 include a high-resolution CCD camera and an integrated signal processing unit. The CCD camera is mounted on a bracket near the laser head, which is bolted to the housing of the laser emitting unit 1. A beam splitter, located in the laser beam path and connected to the bracket via a mirror mount, separates the light reflected from the wafer surface and directs it to the CCD camera. The signal processing unit, which has a built-in algorithm module and is connected to the CCD camera via a data cable, receives image data and calculates changes in film thickness. The signal processing unit also communicates with the central control system to adjust laser power and scanning path based on the calculated results.

[0025] Special fixture 4 such as Figure 2 As shown, it consists of a base 5, a vacuum adsorption plate 6 and a flexible buffer layer 7. The base 5 is made of high-strength aluminum alloy material. The bottom is fixed to the workbench by bolts, and the top is provided with a groove for installing the vacuum adsorption plate 6. The vacuum adsorption plate 6 is connected through a micro vacuum pump, which can form a negative pressure environment at the bottom of the wafer, thereby firmly fixing it. The flexible buffer layer 7 is located between the adsorption plate 6 and the wafer. It is made of silicone material with a thickness ranging from 0.5mm to 2mm and can be flexibly replaced according to the size of the wafer. The flexible buffer layer 7 is fixed to the vacuum adsorption plate 6 by bonding, and its surface is specially treated to improve wear resistance and anti-aging performance.

[0026] In actual operation, the wafer to be processed is first placed on a dedicated fixture 4. A microvacuum pump is activated to generate negative pressure on the vacuum adsorption plate 6, thereby firmly securing the wafer to the fixture. This then enters the preprocessing phase, where a low-power laser is used to perform a preliminary scan of the wafer surface. This process is controlled by a central control system, which sets the laser parameters, including wavelength, pulse width, and repetition rate. A CCD camera captures the reflected light signal from the wafer surface in real time, and a signal processing unit calculates the film thickness. This data is then transmitted to the central control system for parameter setting in the subsequent main processing phase.

[0027] At the beginning of the main processing stage, the central control system sets the laser parameters according to the data obtained in the pre-processing stage and starts the laser emission unit 1. The laser beam adjusts the focal position through the dynamic focusing lens group so that it acts accurately on the film layer on the surface of the wafer. At the same time, the auxiliary airflow control device 2 is started, and high-speed inert gas is blown out from the annular nozzle array, covering the entire processing area. The high-speed airflow not only carries away the ablation products, but also cools the surface of the wafer, thereby effectively suppressing the heat accumulation effect. The optical detection feedback system 3 continuously monitors the film removal status. When it detects that the film layer in a certain area has not been completely removed, the system automatically increases the laser irradiation time in that area; on the contrary, if the film layer has been completely removed, it quickly switches to the next area.

[0028] During the post-processing phase, ultrasonic cleaning equipment performs a secondary cleaning of the wafer surface, thoroughly removing any trace residue. The ultrasonic cleaning equipment communicates with a central control system, automatically completing the cleaning process according to pre-set procedures. Throughout the entire processing process, the central control system centrally manages the operating status of each component, allowing operators to initiate automated operations by simply entering initial parameters.

[0029] The above-described specific embodiments demonstrate that this invention addresses existing issues such as low film removal efficiency, high residual rates, and wafer substrate damage through the synergistic effects of a multi-stage modulated pulsed laser, an auxiliary airflow control device, an optical detection feedback system, and a specialized fixture. The interconnections and coordination between these components ensure system stability and reliability, while also improving process flexibility and processing quality.

[0030] In order to better enable relevant personnel in this technical field to fully understand and implement the present invention, the specific implementation principle of the present invention is further supplemented below with reference to a specific application scenario.

[0031] During the actual processing, the wafer to be processed is first placed on a special fixture 4. The base 5 in the fixture 4 is fixed to the workbench by bolts to ensure the stability of the overall structure. Subsequently, the micro vacuum pump is started to create a negative pressure environment in the vacuum adsorption disk 6, and the flexible buffer layer 7 contacts the bottom of the wafer to firmly fix the wafer. The silicone material of the flexible buffer layer 7 can effectively alleviate the local stress concentration caused by the adsorption force and avoid microcracks or deformation on the wafer surface. At the same time, the thickness of the flexible buffer layer 7 can be flexibly adjusted according to the wafer size to meet the processing requirements of wafers of different specifications.

[0032] After the wafer is fixed, the pre-processing stage begins. During this stage, the central control system sets the initial parameters of the laser emitting unit 1, including wavelength, pulse width, and repetition rate. The laser emitting unit 1 outputs a low-power laser beam, and the dynamic focusing lens group adjusts the focal position via a stepper motor to ensure that the laser beam evenly covers the wafer surface. At this point, the optical detection feedback system 3 is activated, and the CCD camera captures the light signal reflected from the wafer surface via a spectrometer. The signal processing unit then calculates the film thickness distribution information. This data is analyzed by the algorithm module and transmitted to the central control system for parameter optimization in the subsequent main processing stage.

[0033] At the beginning of the main processing stage, the central control system dynamically adjusts the output power and scanning path of the laser emitting unit 1 based on the data obtained in the pre-processing stage. The high-energy pulsed laser beam output by the laser acts on the film layer on the surface of the wafer. Since the laser wavelength range is 200nm to 1100nm and the pulse width is adjustable between 10fs and 100ns, it can accurately match the absorption characteristics of the film material to avoid thermal damage to the wafer substrate. At the same time, the auxiliary airflow control device 2 is started, and the annular nozzle array blows high-speed inert gas to the surface of the wafer. The gas mixing chamber accurately controls the ratio of gas components through a proportional valve, such as the mixing ratio of nitrogen and argon, to generate the best airflow combination. The high-speed airflow not only carries away the ablation products, but also suppresses the heat accumulation effect on the wafer surface through cooling, thereby reducing the impact of thermal stress.

[0034] During the main processing, the optical inspection feedback system 3 continuously monitors the film removal status. If the CCD camera detects that the film in a certain area has not been completely removed, the signal processing unit will adjust the laser exposure time in real time and increase the scanning density in that area. Conversely, if the film has been completely removed, it will quickly switch to the next area to avoid over-processing and damage to the wafer substrate. This closed-loop feedback mechanism significantly improves the accuracy and efficiency of film removal.

[0035] After entering the post-processing stage, the wafers are transferred to an ultrasonic cleaning system for secondary cleaning. Ultrasonic cleaning uses high-frequency vibrations to remove any trace impurities that may remain on the wafer surface, ensuring that the surface cleanliness after film removal meets process requirements. The entire post-processing process is managed by a central control system, and the operator only needs to enter initial parameters to complete the automated operation.

[0036] In summary, in this specific application scenario, the present invention achieves precise removal of film layers from wafer surfaces through the stable fixation of the dedicated fixture 4, the multi-stage modulation of the laser emission unit 1, the efficient cooling of the auxiliary airflow control device 2, and the real-time monitoring of the optical detection feedback system 3. The synergistic effect of these components not only reduces the residual film rate but also effectively mitigates the impact of thermal stress on the wafer substrate, thus meeting the demand for efficient and high-quality wafer processing in modern semiconductor manufacturing.

[0037] Any content not described in detail in the specification belongs to the prior art known to those skilled in the art, and the model parameters of each electrical appliance are not specifically limited, and conventional equipment can be used. In this technical solution, electrical control components not mentioned are not shown in the figures because they belong to the prior art and will not be described here.

[0038] While embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions, and variations may be made to these embodiments without departing from the principles and spirit of the invention, and that the scope of the invention is defined by the appended claims and their equivalents.

Claims

1. A method for removing a film layer on a wafer surface by using laser action, characterized in that The following steps are involved: A laser emitting unit (1) is provided, wherein the laser emitting unit (1) adopts a multi-level modulated pulse laser, the output wavelength of which ranges from 200 nm to 1100 nm, and the pulse width of which is adjustable between 10 fs and 100 ns; The focus position of the laser beam is adjusted by a dynamic focusing lens group, wherein the dynamic focusing lens group is composed of multiple aspheric lenses and is driven by a stepping motor to achieve displacement; An auxiliary airflow control device (2) is introduced, wherein the auxiliary airflow control device (2) comprises an annular nozzle array and a gas mixing chamber, wherein the annular nozzle array is arranged around the laser beam outlet and blows high-speed inert gas toward the wafer surface; An optical detection feedback system (3) is provided, wherein the optical detection feedback system (3) includes a high-resolution CCD camera and an integrated signal processing unit for real-time monitoring of the thickness change of the film layer on the wafer surface and adjusting the laser power and scanning path; A special fixture (4) is used to fix the wafer. The special fixture (4) includes a base (5), a vacuum adsorption disk (6) and a flexible buffer layer (7). The base (5) is made of a high-strength aluminum alloy material. The vacuum adsorption disk (6) is connected to the wafer via a micro vacuum pump to form a negative pressure environment. The flexible buffer layer (7) is located between the vacuum adsorption disk (6) and the wafer and has a thickness of 0.5 mm to 2 mm.

2. The method for removing a film layer on a wafer surface by using laser action according to claim 1, characterized in that: The beam shaping module of the laser emission unit (1) is equipped with a dynamic focusing lens group, which is driven by a stepper motor and fixed to the laser body by a threaded connection. The stepper motor is connected to the lens group via a gear transmission mechanism to accurately control the displacement.

3. The method for removing a film layer on a wafer surface by using laser action according to claim 1, characterized in that: The annular nozzle array of the auxiliary airflow control device (2) is connected and fixed to the housing of the laser emitting unit (1) via a flange, and the gas mixing chamber controls the proportion of different gas components via a proportional valve, which is driven by an electromagnetic and communicates with a central control system.

4. The method for removing a film layer on a wafer surface by using laser according to claim 1, characterized in that: The high-resolution CCD camera of the optical detection feedback system (3) is installed on a bracket near the laser head, the spectroscope is located in the laser beam path and is connected to the bracket through a mirror frame, and the signal processing unit is connected to the CCD camera through a data line and has a built-in algorithm module.

5. The method for removing a film layer on a wafer surface by using a laser according to claim 1, characterized in that: The bottom of the base (5) of the special clamp (4) is fixed to the workbench by bolts, and the top is provided with a groove for mounting a vacuum adsorption plate (6), and the flexible buffer layer (7) is fixed to the vacuum adsorption plate (6) by bonding.

6. The method for removing a film layer on a wafer surface by using laser according to claim 1, characterized in that: The entire removal process is divided into three stages: pre-processing, main processing and post-processing. In the pre-processing stage, a low-power laser is used to perform a preliminary scan of the wafer surface to determine the film distribution and thickness information.

7. The method for removing a film layer on a wafer surface by using laser according to claim 6, characterized in that: In the main processing stage, laser parameters are set according to the data obtained in the pre-processing stage, and a laser beam is emitted through a laser emission unit (1), while an auxiliary air flow control device (2) is started to blow high-speed inert gas to the wafer surface.

8. The method for removing a film layer on a wafer surface by using laser according to claim 6, characterized in that: In the post-processing stage, the wafer surface is cleaned again by ultrasonic cleaning equipment to remove any trace residues that may exist. The ultrasonic cleaning equipment communicates with the central control system and completes the cleaning operation according to the preset program.

9. The method for removing a film layer on a wafer surface by using laser according to claim 1, characterized in that: The high-speed inert gas is nitrogen or argon, and each nozzle in the annular nozzle array is inclined and forms a certain angle with the wafer surface to ensure that the high-speed airflow covers the entire processing area.

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