Auto focus area mask and parameter control method for wafer detection

Abstract

The application discloses an automatic focusing area shielding and parameter control method for wafer detection, which comprises the following steps: at least one automatic focusing disabled area is preliminarily demarcated on a wafer, and a shielding instruction array containing a trigger position sequence and a focusing enabling state sequence is generated according to the spatial position of the area; the shielding instruction array is issued to a motion controller; in the scanning process, the motion controller outputs a current scanning position in real time, and the current scanning position is compared with the trigger position sequence by a hardware comparison module; when any trigger position is reached, a position synchronous output function outputs a level signal to instantaneously activate or deactivate a focusing sensor according to the corresponding focusing enabling state; during the focusing sensor is in the enabled state, the output signal of the focusing sensor is subjected to limiting and biasing processing according to the sensor output limiting parameter and the focusing biasing parameter bound with the current process, and then is used for Z-axis motion control. The application significantly improves the focusing accuracy, stability and production efficiency of wafer detection.

Description

Technical Field

[0001] This invention relates to wafer inspection and processing technology in semiconductor manufacturing, specifically to an automatic focusing area shielding and parameter control method for wafer inspection, which is particularly suitable for dealing with focusing abnormalities caused by abrupt changes in reflectivity in areas such as wafer dicing paths and edges, as well as the differences in the optimal working range of sensors and the shift in focusing position under different processes. Background Technology

[0002] In the field of semiconductor wafer inspection, autofocus (AF) technology is a key element in achieving high-precision inspection. Most existing autofocus systems for wafer inspection employ a real-time closed-loop feedback control scheme: the equipment is equipped with a focus sensor (such as a confocal sensor or a laser displacement sensor), which measures the distance between the wafer surface and the objective lens in real time during the scanning process and feeds back the defocus signal to the focus controller. The controller drives the Z-axis motion mechanism to maintain the objective lens at the optimal focus distance with the wafer surface.

[0003] However, the above-mentioned solutions have the following technical drawbacks when applied to complex wafer fabrication processes:

[0004] (1) Abnormal focusing caused by sudden change in reflectivity In some wafer fabrication processes, the reflectivity of the scribe line area is high, while the reflectivity of the die interior area is low. When the stage scans at high speed, the focus sensor rapidly moves from a low-reflectivity area to a high-reflectivity area. Due to the sudden change in reflectivity, the sensor output measurement value will show a momentary anomaly (such as signal saturation or jump), causing the focus control system to misinterpret the reflectivity change as a height change, generating an incorrect Z-axis adjustment command, and causing the image to go out of focus.

[0005] (2) Limitations of existing solutions To address the aforementioned issues, some solutions have attempted to suppress outliers through image post-processing or filtering algorithms. For example, existing technologies have proposed an image mask-based assisted focusing method: extracting spatial frequency information from the image using Fourier transform, generating masking data to filter the image, and then determining the focus based on the filtered image. However, this approach has significant shortcomings: first, it is inefficient, requiring Fourier transform and filtering for each field of view, which cannot meet the real-time requirements of high-speed scanning; second, the masking process occurs after image acquisition, failing to prevent abnormal signals from entering the focus controller, thus allowing incorrect adjustment to occur; and third, it only applies to the image domain and cannot control sensor startup and shutdown at the hardware level.

[0006] Furthermore, existing solutions lack a linkage mechanism between the sensor's parameter configuration (such as output limiting and focus position offset) and the scanning area, making it impossible to dynamically adjust the sensor's operating state according to the characteristics of the area. Summary of the Invention

[0007] The objective of this invention is achieved through the following technical solutions.

[0008] This invention aims to solve the problem in the prior art where abrupt changes in wafer surface reflectivity cause abnormal output of the focusing sensor and lead to image defocusing. It also addresses the issue of differences in the optimal linear working range of sensors under different manufacturing processes and the need for frequent adjustments to the hardware reference due to focus position shifts. The invention provides an autofocus area shielding and parameter control system that can achieve regional hardware shielding and optimized configuration of sensor parameters.

[0009] To address the aforementioned technical problems, this invention proposes an automatic focusing area shielding and parameter control method for wafer inspection. The method includes: determining the spatial location of at least one area on the wafer requiring focusing shielding based on the current wafer process information; generating a shielding command array based on the spatial location, the array containing a trigger position sequence and a corresponding focusing enable state sequence; and pre-setting the array into a motion controller. During scanning, the current scanning position is acquired in real time and compared with the trigger position sequence by a hardware comparison module; when any trigger position is reached, a control signal is output in real time according to the corresponding enable state through a position synchronization output function to instantly enable or disable the focusing sensor's measurement function. Simultaneously, during the focusing sensor's activation, its defocus signal is acquired, and after secondary processing based on the output limiting parameters and focus bias parameters bound to the current wafer process, this signal is used as the basis for driving the Z-axis motion.

[0010] Compared with the prior art, the present invention has the following beneficial effects:

[0011] (1) Hardware-level real-time shielding completely eliminates interference from reflectivity change: The PSO function directly controls the sensor laser switch within a microsecond response time, forcibly shutting down the sensor in the reflectivity change area, fundamentally preventing abnormal signals from entering the focus controller. Compared with the image post-processing solution, the response speed is improved by several orders of magnitude.

[0012] (2) The sensor always operates in the optimal linear range: The AF Limit function is used to configure the matching output limiting range for wafers of different processes to avoid sensor saturation or entering the nonlinear region and improve measurement reliability.

[0013] (3) Quickly adapt to focus offset of different processes: Through the AF Offset function, the layer thickness difference and the focus offset of transparent wafers can be compensated without mechanical adjustment. When switching processes, it can be called with one click, saving the adjustment time.

[0014] (4) Flexible area shielding capability: It not only supports regular cut-out array mask, but also supports single-point mask of any area (such as fixed foreign object point), and can even cover the entire die area to adapt to the shielding needs of various complex scenarios.

[0015] (5) Iterative optimization mechanism: Through the closed-loop process of “scanning → confirming the blurring image → adjusting the Mask coordinates → re-scanning”, the optimal Mask parameters can be quickly converged to ensure the masking effect. Attached Figure Description

[0016] Various other advantages and benefits will become apparent to those skilled in the art upon reading the following detailed description of preferred embodiments. The accompanying drawings are for illustrative purposes only and are not intended to limit the invention. Furthermore, the same reference numerals denote the same parts throughout the drawings. In the drawings:

[0017] Figure 1 This is an architecture diagram of an automatic focusing area shielding and parameter control method for wafer inspection according to the present invention.

[0018] Figure 2 This is a flowchart illustrating the automatic focusing area shielding and parameter control method for wafer inspection according to the present invention.

[0019] Figure 3 This is a schematic diagram of the Mask cutting path.

[0020] Figure 4 This is a schematic diagram of any region of the Mask.

[0021] Figure 5 This is a status-based oscilloscope signal diagram. Detailed Implementation

[0022] Exemplary embodiments of the present disclosure will now be described in more detail with reference to the accompanying drawings. While exemplary embodiments of the present disclosure are shown in the drawings, it should be understood that the present disclosure may be implemented in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the disclosure to those skilled in the art.

[0023] This invention provides an automatic focusing area shielding and parameter control system for wafer inspection, comprising the following functional modules: 1. AF Mask function (hardware-level area masking)

[0024] By utilizing the Position Synchronized Output (PSO) function of the high-speed comparator module, and through pre-programmed space mapping and real-time hardware decision-making, the start / stop status of the autofocus system is dynamically controlled during wafer scanning. The specific implementation steps are as follows:

[0025] Step 1: On the application software side, determine the areas that need to be masked (such as dicing lines, wafer edges, fixed anomalies) based on the wafer design drawing, and draw the mask area. For periodically occurring dicing lines, array mask generation is supported; for arbitrary areas (such as particle points within a single die), single-point mask drawing is supported.

[0026] Step 2: The system automatically generates two arrays based on the drawn Mask area:

[0027] Trigger position array (afTrigXposArr): Records the start and end X coordinates of all Mask regions; AF state array (GatingArr): corresponds to the AF enable state after each coordinate point (0 means AF is off, 1 means AF is on).

[0028] Step 3: Send the above array to the ACS buffer label of the motion controller through the communication interface.

[0029] Step 4: During the scanning process, the motion controller outputs the X coordinate of the current scanning position in real time. The AF Mask controller (high-speed comparison module) performs a hardware comparison between the current coordinate and the preset position in afTrigXposArr. When a trigger point is matched, a level signal is output through the PSO function according to the corresponding state in GatingArr.

[0030] If the status is "1" (AF enabled zone), AF_ENABLE (high level) is output to activate the AF sensor laser and receive the reflected signal normally. If the status is "0" (AF disabled zone), AF_DISABLE (low level) is output to force the AF sensor laser to be turned off and skip focus detection.

[0031] Step 5: If no trigger point is matched, keep the current output state unchanged.

[0032] Step 6: When the image processing unit acquires an image in the AF disabled area, since the focus sensor is turned off or the signal is blocked, it will not produce incorrect Z-axis adjustment due to sudden changes in reflectivity, thus ensuring image clarity.

[0033] 2. AF Limit function (sensor output limiting)

[0034] The AF sensor output is designed with upper and lower soft limits (i.e., AF Limit parameters). When the defocus amount output by the sensor exceeds the set limit range, the system performs a limiting process to prevent the piezoelectric or Z-axis drive mechanism from running out of the effective measurement range (In Capture Range) of the AF sensor, which would cause focusing failure.

[0035] Due to differences in surface reflectivity, transparency, and other characteristics, wafers manufactured using different processes have varying optimal linear operating ranges for their sensors. For example, high-reflectivity wafers may cause sensor signals to saturate prematurely, while thin, transparent wafers may narrow the linear range due to multiple reflections. By properly configuring the AF Limit, the sensor can always operate within the linear region, effectively suppressing abnormal interference introduced by process characteristics.

[0036] For wafers with large warpage, the AF Limit should be set to a larger range (e.g., ±500μm) to accommodate surface undulations; for flat wafers, it can be set to a smaller range to improve response sensitivity.

[0037] 3 Substrate function (AF Offset)

[0038] The Substrate function allows for the offset setting (i.e., AF Offset value) of the focus position after autofocus. Wafers from different manufacturing processes may exhibit differences in focus position, for example: Focal plane offset caused by different process layer thicknesses; The transparency of thin wafers causes the optimal focal plane to deviate from the theoretical surface. The fixed height difference between the target layer and the non-target layer in a multi-layer structure.

[0039] By setting the AF Offset value, the aforementioned issue of inconsistent focus positions can be easily addressed without needing to readjust the hardware reference of the focusing system. This offset value can be linked to the process formula, and the system automatically loads the corresponding AF Offset when switching between different processes.

[0040] 4. Collaborative Control and Formulation Management

[0041] The above three functions are configured with parameters through software recipes, and together with parameters such as In Focus Range, MaxVel, and Max Acc, form a complete outlier suppression system. Operators select the corresponding recipe based on the wafer process type, and the system automatically loads the following configurations: The trigger point array and state array of AF Mask; The upper and lower limits of AF Limit; AF Offset value; other focus control parameters.

[0042] Figure 2 This is a flowchart illustrating the automatic focusing area shielding and parameter control method for wafer inspection according to the present invention.

[0043] The specific implementation of this invention is described in detail below: 1. System Overall Architecture

[0044] The autofocus control system of the present invention includes the following core components (see Figure 1 ):

[0045] Host computer software: responsible for recipe management, mask area drawing, parameter configuration, and recipe library management.

[0046] Motion controller: responsible for X / Y / Z axis motion planning and real-time coordinate output.

[0047] AF Mask Controller (based on high-speed comparison module): responsible for real-time coordinate comparison, PSO trigger decision, and level signal output.

[0048] AF sensor: Confocal / laser sensor, controlled by the AF_ENABLE signal.

[0049] Focus controller: Receives the defocus measurement value and generates Z-axis drive commands.

[0050] Image processing unit: image acquisition, defect detection, and blur judgment.

[0051] 2. Implementation of AF Mask Function

[0052] (1) Functional Overview

[0053] The AF Mask function dynamically controls the autofocus system's on / off state during wafer scanning through pre-programmed spatial mapping and real-time hardware decision-making, achieving masking of specific areas. Its core design is as follows:

[0054] AF Activation Area: Normal chip area (Die), where the system activates the confocal sensor to perform precision focusing.

[0055] AF disabled zones include, but are not limited to, wafer edges, dicing lines, areas with fixed foreign objects or abnormal points, and any user-specified areas that need to be shielded. Within these zones, the system forcibly shuts down the sensor laser and skips focus detection.

[0056] This feature is not only applicable to regular cuts, but can also be flexibly applied to areas of any shape or dot, such as fixed defect points or particulate contamination areas within a single die.

[0057] (2) Implementation process

[0058] The specific implementation steps of AF Mask are as follows:

[0059] Step 1: Recipe Setup and Problem Confirmation

[0060] Set up a detection recipe in the application software, perform a wafer scan, and check if there is any blurring (false image) caused by focusing abnormalities in the image. If the blurring is found to be related to a specific area (such as a cut line or a fixed abnormal point), then it is determined that an AF Mask needs to be added.

[0061] Step 2: Drawing the Mask Area

[0062] For dicing traces: Determine the location and width of the dicing traces based on the wafer design, draw dicing trace Mask1, and record its starting coordinates (a, b) in the X direction. Using the array function, automatically generate other dicing trace Masks (Mask2, Mask3…) based on the periodic distribution of dicing traces on the wafer, and obtain the corresponding coordinate arrays (c, d, e, f…), such as… Figure 3 As shown.

[0063] For any region (such as a fixed foreign object point): directly select the abnormal point region on the image, draw the abnormal point Mask1, and record its X-coordinate range (m, f). If the die area is small and there is an abnormal point in its central region, you can also directly cover the entire die area with a cut-path type Mask, such as... Figure 4 As shown.

[0064] Step 3: Generate and distribute the point array.

[0065] The user interface (UI) automatically generates two arrays based on the drawn mask area:

[0066] AF trigger position array (afTrigXposArr): Records the start and end X coordinates of all Mask regions (for cutting tracks, arranged in order such as {a,b,c,d,e,f}).

[0067] AF status array (GatingArr): corresponds to the AF enable status after each coordinate point. It usually adopts the alternating pattern of "0-1-0-1...", where "0" means that AF is turned off after reaching the coordinate (entering the disabled area), and "1" means that AF is turned on after reaching the coordinate (entering the enabled area).

[0068] For example, for three cutting paths, generate afTrigXposArr(6) = {a,b,c,d,e,f} and GatingArr(6) = {0,1,0,1,0,1}.

[0069] This array is sent to the motion controller's ACS buffer label via the communication interface as the basis for real-time decision-making.

[0070] Step 4: Real-time hardware decision and output

[0071] At the start of the scan, the motion controller outputs the X coordinate of the current scan position in real time. The AF Mask controller (high-speed comparison module) continuously compares the current coordinate with the preset position in afTrigXposArr: when the current position matches a trigger point, it outputs the corresponding level signal through the PSO function according to the corresponding state in GatingArr. If the status is "1" (AF enabled zone), a high level (AF_ENABLE) is output to activate the AF sensor laser and perform focus measurement normally. If the status is "0" (AF disabled zone), the output is low (AF_DISABLE), forcibly turning off the AF sensor laser, skipping focus detection, and keeping the current position on the Z axis or moving according to the 3D Mapping compensation value.

[0072] The decision-making process is completed at the hardware level, with a response time in the microsecond range. See the status model oscilloscope signal for details. Figure 5 As shown.

[0073] Step 5: Verification and Iterative Optimization

[0074] Scan the same wafer again to check if the masking issue has been eliminated. If the masking is not completely gone, adjust the coordinates of the mask area (e.g., fine-tune the start / end position of the dicing mask), and repeat steps 2 to 4 until the masking is completely gone. Finally, save the optimized mask parameters to the Recipe for subsequent batch testing.

[0075] Step 6: Image Acquisition

[0076] When the image processing unit acquires an image in the AF disabled area, the focus sensor is turned off, so there will be no incorrect Z-axis adjustment due to sudden changes in reflectivity or multiple reflections, thus ensuring image sharpness.

[0077] (3) Key technological innovations

[0078] Hardware-level real-time decision-making: Utilizing the PSO function of the high-speed comparison module, the sensor laser is directly controlled to switch on and off at the moment of coordinate matching. The response speed is much faster than the traditional software query method, avoiding abnormal signals from entering the controller.

[0079] Flexible Mask Definition: It not only supports regular cut-line array masks, but also supports single-point masks for arbitrary areas (such as fixed foreign object points), and can even cover the entire die area, adapting to the shielding needs of various complex processes.

[0080] Coordinate and state array coordinated control: By combining afTrigXposArr and GatingArr, precise switching of multiple non-contiguous regions is achieved, and the array length can be dynamically expanded to facilitate the handling of any number of restricted areas.

[0081] Iterative optimization mechanism: Through a closed-loop process of "scanning → confirming the blurring image → adjusting the mask coordinates → re-scanning", the optimal mask parameters can be quickly converged to ensure the masking effect.

[0082] Seamless integration with existing equipment: The array is distributed based on the buffer label mechanism of the standard motion controller, and the focus shielding of complex areas can be achieved through software configuration without modifying the hardware.

[0083] 3. Software recipe library and multi-process adaptive control.

[0084] (1) Functional Overview

[0085] A formula library is established on the application software side, and multiple sets of control parameters and strategy combinations are predefined according to different process characteristics to achieve one-click adaptation to different wafer processes (thin, transparent, warped, multilayer, high reflectivity differences, etc.).

[0086] (2) Formula contents

[0087] Each recipe includes the following parameter configurations:

[0088] Table 1 Parameter Configuration Table

[0089] Table 2 Formulation Table

[0090] (4) Work process

[0091] Before testing, the operator selects the corresponding recipe from the software based on the current wafer process type; the system automatically loads all parameter configurations in the recipe; during the scanning process, the system executes the corresponding control strategy according to the recipe settings.

[0092] 4. AF Limit and Substrate functions.

[0093] (1) AF Limit function

[0094] The AF Limit function provides upper and lower soft limits for the AF sensor's output. When the sensor's output defocus exceeds the set limit range, the system performs limiting processing to prevent the piezoelectric or Z-axis drive mechanism from running out of the AF sensor's In Capture range, which could cause focusing failure.

[0095] For wafers with large warpage, the AF Limit should be set to a larger range (e.g., ±500μm) to accommodate surface undulations; for flat wafers, a smaller range can be set to improve response sensitivity. Furthermore, the optimal linear operating range for sensors differs depending on the wafer manufacturing process (e.g., multiple reflections in thin, transparent wafers can narrow the linear range, and saturation shifts may occur near high-reflectivity dicing). By properly configuring the AF Limit, the sensor can always operate within the linear region, effectively suppressing abnormal interference introduced by process characteristics (such as abrupt changes in reflectivity, transparency, and multilayer structures).

[0096] This function works in conjunction with parameters such as In Focus Range, Max Vel, and Max Acc to form a complete outlier suppression system.

[0097] (2) Substrate function (AF Offset function)

[0098] The Substrate function allows for offset settings of the focus position after AF focusing. Different wafer manufacturing processes may result in differences in the focus position, for example:

[0099] Focal plane shift caused by different layer thicknesses; The transparency of thin wafers causes the optimal focal plane to deviate from the theoretical surface. The fixed height difference between the target layer and the non-target layer in a multi-layer structure; Focal plane shift caused by different layer thicknesses; The transparency of thin wafers causes the optimal focal plane to deviate from the theoretical surface. The fixed height difference between the target layer and the non-target layer in a multi-layer structure; Focal plane shift caused by different layer thicknesses; The transparency of thin wafers causes the optimal focal plane to deviate from the theoretical surface. The fixed height difference between the target layer and the non-target layer in a multi-layer structure.

[0100] By setting the AF Offset value, the aforementioned issue of inconsistent focus positions can be easily addressed without needing to readjust the hardware reference of the focusing system. This offset value can be bound to a formula, and when switching between different processes, the system automatically loads the corresponding AF Offset, achieving one-click adaptation.

[0101] 5. Integrated Control Process

[0102] (1) Preparation before scanning

[0103] 1. Selecting a Recipe: The operator selects the corresponding recipe from the software based on the wafer process type (thin / transparent / warped / multilayer / conventional).

[0104] 2. Load Configuration: The system automatically loads the following configuration based on the selected recipe; 3. AF Mask Configuration: Generate a trigger position array afTrigXposArr and a status array GatingArr (e.g., for three cutting tracks: afTrigXposArr={a,b,c,d,e,f}, GatingArr={0,1,0,1,0,1}), and send them to the motion controller; 4. Focus control parameters: AF Limit, In Focus Range, Max Vel, Max Acc, AF Offset, etc.

[0105] (2) During the scanning process

[0106] 1. Coordinate output: The motion controller outputs the X coordinate of the current scanning position to the AF Mask controller (high-speed comparison module) in real time.

[0107] 2. Hardware Decisions and AF Start-up / Stop:

[0108] The AF Mask controller performs a hardware comparison between the current coordinates and the preset position in afTrigXposArr; When a trigger point is matched, a level signal is output through the PSO function according to the corresponding state in GatingArr: If the status is "1" (AF enabled zone): AF_ENABLE (high level) is output to activate the AF sensor laser and receive reflected signals normally; If the status is "0" (AF disabled zone): output AF_DISABLE (low level), forcibly turn off the AF sensor laser, and skip focus detection; If no trigger point is matched, the current output state remains unchanged.

[0109] 3. Z-axis drive: The focus controller drives the Z-axis movement based on the current defocus value. If the AF sensor is enabled, it also receives real-time defocus signals for closed-loop fine-tuning (real-time feedback is usually disabled for transparent wafers depending on the formulation).

[0110] 4. Outlier handling: Real-time monitoring of focus status; if outliers exceed the set ranges such as AF Limit and In Focus Range, they will be limited or ignored.

[0111] (3) After scanning

[0112] Data logging: The system records the focus status data for this scan, including the number of times AF is enabled / disabled in each area, the frequency of outliers, and the actual defocus deviation.

[0113] Recipe optimization: If the blurring phenomenon is not completely eliminated, the Mask coordinates (such as fine-tuning the start / end position of the cutting mask) or focus parameters can be adjusted according to the recorded data. Repeat the iterative process of "scan → confirm → adjust" until the best effect is achieved. Finally, save the optimized parameters to the recipe.

[0114] Anomaly Analysis: Areas where focusing anomalies occur frequently can be marked as suspected defect points for subsequent re-inspection or process improvement reference.

[0115] When a trigger point is matched, a level signal is output through the PSO function according to the corresponding state in GatingArr:

[0116] If the status is "1" (AF enabled zone): AF_ENABLE (high level) is output to activate the AF sensor laser and receive reflected signals normally; If the status is "0" (AF disabled zone): output AF_DISABLE (low level), forcibly turn off the AF sensor laser, and skip focus detection; If no trigger point is matched, the current output state remains unchanged.

[0117] 6. AF System Control Function Design Description.

[0118] The AF system control function design of this invention includes the following core functional modules:

[0119] 1) AF Limit function

[0120] Design upper and lower soft limits for the output of the AF sensor.

[0121] To avoid extreme situations where the piezoelectric or Z-axis moves out of the AF sensor's In Capture range, causing the AF to fail.

[0122] It works in conjunction with parameters such as In Focus Range, Max Vel, and Max Acc to form a complete outlier suppression system.

[0123] 2) Substrate function (AF Offset function)

[0124] It allows for easy offsetting of the focus position after AF focusing.

[0125] Addressing the issue of inconsistent focal positions across different manufacturing processes (including optimal focal plane offset for thin, transparent wafers).

[0126] There is no need to readjust the focusing system's baseline; it can be adapted to different processes through software parameters.

[0127] 3) AF Mask function

[0128] By using pre-programmed space mapping and real-time hardware decision-making, the start and stop status of the autofocus system is dynamically controlled during wafer scanning.

[0129] AF Activation Area: Normal chip area → Activate confocal sensor to perform precision focusing.

[0130] AF Disabled Zone: Wafer Edge / Cut Track → Force sensor laser off, skip focus detection.

[0131] Alternative implementation methods

[0132] In addition to pre-programmed coordinate arrays, the AF Mask's decision-making can also incorporate real-time image recognition technology. This allows the vision system to detect cutting paths or abnormal areas online and dynamically generate masking commands, further enhancing the system's adaptability to unknown or changing processes. Furthermore, besides turning the laser on / off, the focus sensor can also be controlled by electronically blocking the signal flow returned to the controller, achieving an equivalent effect.

[0133] The above description is merely a preferred 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. A method for automatic focusing area shielding and parameter control for wafer inspection, characterized in that, include: Based on the current wafer manufacturing process information, determine the spatial location of at least one area on the wafer that needs to be shielded for focusing. Based on the spatial location, a masking command array is generated. The masking command array includes a trigger position sequence related to the scanning direction and a focus enable state sequence corresponding to each trigger point in the trigger position sequence. The array of shielding instructions is pre-loaded into the motion controller; During the scanning process, the current scanning position provided by the motion controller is acquired in real time, and a hardware comparison module compares the current scanning position with the trigger position sequence. In response to the current scanning position reaching any trigger position, the position synchronization output function outputs a control signal in real time according to the focus enable state corresponding to the trigger position, so as to instantly enable or disable the measurement function of the focus sensor. Specifically, while the focus sensor is in the enabled state, its output defocus amount signal is acquired, and the defocus amount signal is further processed according to at least one control parameter bound to the process information of the current wafer, and then used as the basis for driving the Z-axis movement; the at least one control parameter includes an output limiting parameter for limiting the output range of the defocus amount, and / or a focus offset parameter for compensating for focus position offset.

2. The method according to claim 1, characterized in that, Determining the spatial location of at least one region on the wafer that needs to be shielded from focusing includes at least one of the following methods: Identify periodic structural regions on the wafer and generate an array-type shielding region that covers all periodically occurring similar regions based on their design dimensions and periods; Alternatively, based on the analysis of wafer scan images, fixed abnormal points or particulate contamination areas can be identified, thereby defining single-point shielding areas of arbitrary shapes.

3. The method according to claim 2, characterized in that, The trigger position sequence is a coordinate sequence arranged along the X-axis scanning direction. The coordinate sequence is composed of the start X-coordinate and end X-coordinate of all the shielded areas in sequence. The focus enable state sequence is a corresponding binary sequence, where 0 indicates that the autofocus disabled area is entered after the trigger point, and 1 indicates that the autofocus enabled area is entered after the trigger point.

4. The method according to claim 1, characterized in that, The control signal is a level signal, which is directly connected to the focus sensor through a hardware circuit to control the on and off of the measurement laser, or to control whether the output signal is transmitted to the downstream focus controller.

5. The method according to claim 2, characterized in that, Also includes: The output limiting parameter and the focus bias parameter are encapsulated together with the shielding area delineation information into a recipe file corresponding to the process. When switching wafer manufacturing processes, the masking instruction array and various control parameters can be configured with one click by calling the corresponding recipe file.

6. The method according to claim 2, characterized in that, It also includes an iterative optimization step: After performing a scan using the current masking instruction array, the acquired image is obtained; Determine whether the image clarity at the boundary of the shielded area meets a preset standard; If the requirements are not met, the spatial position of the shielded area is adjusted and a new shielding instruction array is generated. The scan and verification are performed again until the image clarity meets the standards.

7. An automatic focusing area shielding and parameter control system for wafer inspection, characterized in that, include: The host computer software module is used to provide a human-computer interaction interface to define the autofocus shielding area and configure the output limiting parameters and focus offset parameters. The array generation module is used to generate a masking instruction array containing a trigger position sequence and a focus enable state sequence based on the defined area. The motion controller is used to control the scanning motion of the platform and output the current scanning position in real time. The hardware comparison and position synchronization output module has a pre-set masking instruction array inside, which is used to compare the current scanning position with the trigger position sequence in real time, and output an enable or disable control signal when the positions match. The focusing sensor, whose measurement function is controlled by the control signal; The focus controller is used to receive the output signal of the focus sensor when the focus sensor is enabled, and to generate a Z-axis drive command after secondary processing using the output limiting parameter and focus bias parameter to control the Z-axis drive mechanism.

8. The system according to claim 7, characterized in that, The focusing sensor is a confocal sensor or a laser displacement sensor; the Z-axis drive mechanism is a piezoelectric ceramic actuator or a linear motor.

9. The system according to claim 7, characterized in that, The host computer software module also includes a recipe management unit, which is used to store and call recipe files corresponding to different wafer processes, integrating shielding area information, output limiting parameters and focus bias parameters.

10. A computer-readable storage medium having a computer program stored thereon, characterized in that, When the program is executed by the processor, it implements the steps of the method as described in any one of claims 1 to 6.

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