A real-time focusing device and method for wafer detection

Abstract

The present invention provides a real-time focusing device and method for wafer detection. The device includes a lens module, a controller, and a distance detection module. The lens module and the distance detection module are arranged opposite to each other, and there is a gap for placing a wafer between the lens module and the distance detection module. The lens module is used to capture an image of the detection surface of the wafer. The distance detection module is used to detect the undulation change information of the back surface of the wafer and transmit the undulation change information to the controller. The controller is used to calculate the movement compensation amount of the lens module according to the received undulation change information and send a movement control signal to the lens module according to the calculated movement compensation amount. The lens module is further used to adjust the distance between the lens and the wafer surface according to the received movement control signal. The present invention can ensure the accuracy and effect of lens focusing under the condition of a simple and low-cost overall lens design, which helps to improve the accuracy and efficiency of wafer surface detection.

Description

Technical Field

[0001] The present invention relates to the technical field of semiconductor wafer detection, and particularly to a real-time focusing device and method for wafer detection. Background Art

[0002] For high-precision wafer surface detection, an optical lens is usually used to detect the wafer surface. During the high-precision detection process, it is necessary to keep a stable and constant distance (i.e., the focusing distance) between the lens and the wafer surface during scanning. Generally, the deviation of this distance cannot exceed the depth of field of the lens, otherwise the captured image will become blurred.

[0003] However, due to processing and other factors, the wafer may not be completely flat, and there may be fluctuations of dozens of microns or even larger across the entire wafer. For relatively high-magnification lenses, this fluctuation far exceeds the depth of field of the lens itself. Without focusing, it is impossible to ensure that a clear pattern can be captured during the scanning of the wafer.

[0004] To ensure that the lens can maintain a relatively constant distance from the wafer surface during wafer scanning, the device usually needs to use some mechanisms and methods to perform real-time focusing on the wafer surface. In the prior art, some solutions to the above problems are as follows:

[0005] 1) Vertical scanning combined with image algorithm: For each shooting point on the wafer, the lens will move vertically to collect a series of pictures, and the sharpest and clearest picture is found through the image algorithm. However, since the above method requires collecting multiple pictures for each shooting point on the wafer, the overall device detection efficiency will be relatively low.

[0006] 2) Reflective lens coaxial focusing method: The laser sensor passes through the lens and hits the upper surface of the wafer vertically downward, collects the feedback signal to calculate the distance from the lens to the wafer surface at this moment, and then compares the deviation from the expected focusing distance to adjust the height of the lens once before taking a picture. This method is much faster than vertical scanning plus image algorithm because the objective lens only needs to move once. However, since the light emitted by the laser sensor passes through the lens and irradiates the wafer surface, the wavelength of the laser sensor light needs to avoid the wavelength used by the lens to collect images. Otherwise, the image captured by the lens will be affected by the light spot of the laser sensor (for example, if the image collected by the lens is the entire white light band and the laser sensor uses red light, this red light spot will be captured in the pattern collected by the lens, interfering with other image details that the lens wants to view). Especially when a series of complex optical systems are equipped behind the lens, such as optical paths for fixed-wavelength fluorescence excitation, ensuring that the light of each path does not interfere with the light of the laser sensor will increase the complexity and cost of the overall lens design.

[0007] 3) Pre-scanning method: First, a surface profile of the wafer surface is pre-acquired through a height sensor, and then the height information of each point to be photographed is recorded. In this way, when the lens subsequently acquires and takes pictures, it can be well focused on the corresponding height. However, due to the need for the pre-scanning step in the above method, there is an additional link in the overall test, which will affect the detection efficiency. Summary of the Invention

[0008] In view of the above problems, the present invention aims to provide a wafer detection real-time focusing device and method.

[0009] The object of the present invention is achieved by the following technical solutions:

[0010] In a first aspect, the present invention provides a wafer detection real-time focusing device, including: a lens module, a controller, and a distance detection module; wherein, the lens module and the distance detection module are arranged opposite to each other, and there is a gap for placing the wafer between the lens module and the distance detection module;

[0011] The lens module is used to capture an image of the wafer detection surface;

[0012] The distance detection module is used to detect the undulation change information of the back surface of the wafer and transmit the undulation change information to the controller;

[0013] The controller is used to calculate the movement compensation amount of the lens module according to the received undulation change information and send a movement control signal to the lens module according to the calculated movement compensation amount;

[0014] The lens module is further used to adjust the distance between the lens and the wafer surface according to the received movement control signal.

[0015] Preferably, the lens module includes a moving axis and a lens; wherein the moving axis is arranged facing the gap, and the lens is connected to the moving axis;

[0016] The moving axis is used to control the lens to move away from or close to the wafer on the moving axis according to the received movement control signal.

[0017] Preferably, the distance detection module includes a distance sensor;

[0018] The distance sensor is used to detect the distance between itself and the back surface of the wafer and transmit the obtained distance information to the controller;

[0019] The controller calculates the movement compensation amount according to the received distance information.

[0020] Preferably, the distance detection module includes a distance sensor;

[0021] When the wafer is a transparent film or semi-transparent, the distance sensor is used to detect the first distance between itself and the back surface of the wafer, and the second distance between itself and the front surface of the wafer through the wafer, and transmit the obtained first distance and second distance information to the controller;

[0022] The controller calculates the movement compensation amount according to the received first distance and / or second distance information.

[0023] Preferably, the device further includes a placement module, and the placement module is used to fix the wafer in the gap between the lens module and the distance detection module.

[0024] In a second aspect, based on the wafer detection real-time focusing device proposed in the first aspect above, a wafer detection real-time focusing method is further proposed, including:

[0025] The controller controls the lens module and the distance detection module to move to any position of the wafer for detection at the same time;

[0026] During the detection process, the distance detection module obtains the undulation change information of the back surface of the wafer and transmits the undulation change information to the controller;

[0027] The controller calculates the movement compensation amount of the lens module according to the received undulation change information, and issues a movement control signal to the lens module according to the calculated movement compensation amount;

[0028] The lens module adjusts the distance between the lens and the wafer surface according to the received movement control signal.

[0029] Preferably, the controller calculates the movement compensation amount of the lens module according to the received undulation change information, including:

[0030] The controller calculates the distance change amount between the distance detection module and the back surface of the wafer according to the distance data fed back by the received distance detection module, and obtains the corresponding movement compensation amount according to the obtained distance change amount.

[0031] Preferably, the method further includes: when the controller calculates that the distance between the distance detection module and the back surface of the wafer decreases by a first length, the obtained movement compensation amount is that the lens moves closer to the wafer detection surface by the first length;

[0032] When the controller calculates that the distance between the distance detection module and the back surface of the wafer increases by a second length, the obtained movement compensation amount is that the lens moves away from the wafer detection surface by the second length.

[0033] Preferably, the method further includes: the controller issues corresponding control instructions to the movement axis of the lens module according to the obtained movement compensation amount, so that the movement axis controls the lens thereon to move closer to or away from the wafer by the corresponding length distance according to the movement compensation amount.

[0034] Preferably, the method further includes: placing the wafer to be detected on the placement module, and making the target detection surface of the wafer face the lens module.

[0035] The beneficial effects of the present invention are as follows: The wafer detection real-time focusing device and method proposed above in the present invention can, under the condition of a simple and low-cost overall lens design, adjust the height of the lens module in real time during the detection process to ensure the accuracy and effect of lens focusing, which helps to improve the accuracy and efficiency of wafer surface detection. Description of the Drawings

[0036] The present invention is further described with reference to the accompanying drawings. However, the embodiments in the drawings do not constitute any limitation to the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained according to the following drawings.

[0037] Figure 1 It is a schematic structural diagram of a wafer detection real-time focusing device shown in an exemplary embodiment of the present invention;

[0038] Figure 2 It is a schematic flowchart of a wafer detection real-time focusing method shown in an exemplary embodiment of the present invention. Description of the Drawings:

[0040] 1 - lens module, 2 - controller, 3 - distance detection module, 4 - wafer. Detailed Embodiments

[0041] The present invention is further described in combination with the following application scenarios.

[0042] See Figure 1 , which shows a wafer detection real-time focusing device, including: a lens module 1, a controller 2, and a distance detection module 3; wherein, the lens module 1 and the distance detection module 3 are oppositely arranged, and there is a gap for placing the wafer 4 between the lens module 1 and the distance detection module 3;

[0043] The lens module 1 is used to capture an image of the detection surface of the wafer 4;

[0044] The distance detection module 3 is used to detect the undulation change information on the back surface of the wafer 4 and transmit the undulation change information to the controller 2;

[0045] The controller 2 is used to calculate the movement compensation amount of the lens module 1 according to the received undulation change information and send a movement control signal to the lens module 1 according to the calculated movement compensation amount;

[0046] The lens module 1 is further used to adjust the distance between the lens and the surface of the wafer 4 according to the received movement control signal.

[0047] In a scenario, the lens module 1 and the distance detection module 3 are arranged vertically corresponding to each other. The lens of the lens module 1 is aligned downward, and the distance detection module 3 is arranged upward. The wafer 4 to be detected is fixedly arranged in the gap between the lens module 1 and the distance monitoring module. The lens module 1 aligns with the upper surface of the wafer 4 for detection, and the distance detection module 3 detects the distance between itself and the back surface of the wafer 4.

[0048] Preferably, the controller includes intelligent processing terminals such as computers and servers.

[0049] Preferably, the lens module 1 includes a motion axis and a lens. The motion axis is arranged facing the gap, and the lens is connected to the motion axis.

[0050] The motion axis is used to control the lens to move away from or close to the wafer 4 on the motion axis according to the received movement control signal.

[0051] In a scenario, the motion axis includes a vertical axis arranged in the vertical direction and a driver. The lens is connected to the vertical axis, and the driver controls the vertical axis to drive the lens to rise or fall according to the received movement control signal to adjust the distance between the lens and the upper surface (detection surface) of the wafer 4.

[0052] Preferably, the distance detection module 3 includes a distance sensor.

[0053] The distance sensor is used to detect the distance between itself and the back surface of the wafer 4 and transmit the obtained distance information to the controller 2.

[0054] The controller 2 calculates the movement compensation amount according to the received distance information.

[0055] In a scenario, the distance sensor includes a high-precision distance sensor. The distance sensor can detect the distance between itself and the back surface (lower surface) of the wafer 4, and the detection accuracy of the distance sensor is at the micron level or higher.

[0056] Preferably, the distance detection module 3 includes a distance sensor.

[0057] When the wafer is a permeable film or semi-transparent, the distance sensor is used to detect the first distance between itself and the back surface of the wafer, and the second distance between itself and the front surface of the wafer through the wafer, and transmit the obtained first distance and second distance information to the controller 2.

[0058] In a scenario, the controller 2 calculates the movement compensation amount according to the received second distance information.

[0059] In another scenario, the controller 2 can also perform comprehensive calculations according to the received first distance and second distance information to obtain the movement compensation amount.

[0060] If the wafer is a transparent film or semi-transparent, the distance sensor on the back surface can detect not only the distance between itself and the back surface of the wafer, but also the distance between itself and the front surface of the wafer through the wafer, and transmit the obtained distance information to the controller; the controller calculates the movement compensation amount according to the received distance information.

[0061] Preferably, the device further includes a placement module for fixing the wafer 4 in the gap between the lens module 1 and the distance detection module 3.

[0062] In order to accurately detect the warpage change of the back surface (lower surface) of the wafer 4, the back surface of the wafer 4 needs to be exposed. In one scenario, the way the placement module fixes the wafer 4 can include the way of clamping or supporting point bearing.

[0063] See Figure 2 Based on the above Figure 1 shown wafer detection real-time focusing device, an embodiment of the present invention also proposes a wafer detection real-time focusing method, including:

[0064] The controller controls the lens module and the distance detection module to move to any position of the wafer for detection at the same time;

[0065] During the detection process, the distance detection module obtains the undulation change information of the back surface of the wafer and transmits the undulation change information to the controller;

[0066] The controller calculates the movement compensation amount of the lens module according to the received undulation change information, and issues a movement control signal to the lens module according to the calculated movement compensation amount;

[0067] The lens module adjusts the distance between the lens and the wafer surface according to the received movement control signal.

[0068] Preferably, the controller calculates the movement compensation amount of the lens module according to the received undulation change information, including:

[0069] The controller calculates the distance change amount between the distance detection module and the back surface of the wafer according to the distance data fed back by the distance detection module, and obtains the corresponding movement compensation amount according to the obtained distance change amount.

[0070] In one scenario, when the controller calculates that the distance between the distance detection module and the back surface of the wafer decreases by a first length, the obtained movement compensation amount is that the lens moves closer to the wafer detection surface by the first length;

[0071] When the controller calculates that the distance between the distance detection module and the back surface of the wafer increases by a second length, the obtained movement compensation amount is that the lens moves away from the wafer detection surface by the second length.

[0072] In a certain scenario, a distance sensor continuously detects the distance data between itself and the back surface of the wafer and transmits it to the controller. The controller calculates the movement compensation amount based on the obtained distance data. For example, when the distance sensor detects that the distance to the back surface of the wafer has increased by x μm, it means that the wafer warps upward by x μm at this position, indicating that the upper surface of the wafer also warps by x μm simultaneously. At this time, the distance between the upper surface of the wafer and the lens is shortened by x μm. Therefore, by obtaining a movement compensation amount of upward x μm, the controller controls the lens to move upward by x μm according to the obtained movement compensation amount, so that the lens and the upper surface of the wafer maintain an appropriate distance to meet the focusing distance of the lens.

[0073] The controller issues corresponding control instructions to the movement axis of the lens module according to the obtained movement compensation amount, so that the movement axis controls the lens on it to move a corresponding length distance closer to or away from the wafer according to the movement compensation amount.

[0074] Preferably, the method further includes: placing the wafer to be detected on the placement module, and facing the target detection surface of the wafer towards the lens module.

[0075] In a certain scenario, the working process of the real-time focusing device for wafer detection is as follows: The controller controls the lens above the wafer and the distance sensor below to move to any position of the wafer simultaneously to start scanning and detection. Among them, the initial distance between the lens and the wafer detection surface is set according to the focal length of the lens. The lens moves horizontally and captures an image of the upper surface of the wafer and transmits it to the processing device (such as a computer, smart terminal, memory, display, etc.); among them, during the scanning and detection process, the distance sensor moves along with the lens at the same time. The distance sensor and the lens always maintain corresponding positions. The distance sensor continuously collects the distance data between itself and the lower surface of the wafer and transmits it to the controller. The controller monitors the undulation change information (distance change between the current position and the previous position) of the lower surface of the wafer in real time based on the obtained distance data, and obtains the movement compensation amount according to the obtained undulation change information; the controller outputs a control signal to the movement axis according to the obtained movement compensation amount to control the lens on the movement axis to move up and down. The movement axis compensates the height of the lens accordingly through the feedback control signal, so as to achieve real-time focusing of the upper lens on the upper surface of the wafer.

[0076] Among them, the working principle of the real-time focusing device and method for wafer detection shown in the above embodiments of the present invention is as follows:

[0077] In general, due to the warping of the wafer itself, it is necessary to perform real-time focusing on the upper surface of the wafer on the same side of the lens to capture images. At the same time, due to processing technology reasons, the thickness of the wafer is usually very uniform, and the deviation of the thickness is much smaller than the warping degree (for example, the warping of general wafers is dozens of micrometers or even higher, but the thickness uniformity error is only a few micrometers or even lower). Therefore, the present invention utilizes the above characteristics of the wafer, and by setting a height sensor on the opposite side of the lens, it collects the data change of the undulation of the back surface of the wafer, so as to feedback in real time the height that needs to be adjusted by the front lens. The real-time focusing device and method for wafer detection proposed above in the present invention effectively avoid the deficiencies of the aforementioned existing methods, and can, under the condition of a simple and low-cost overall lens design, adjust the height of the lens module in real time during the detection process to ensure the accuracy and effect of lens focusing, which helps to improve the accuracy and efficiency of wafer surface detection.

[0078] Examples of the embodiments are shown in the drawings, where the same or similar reference numerals represent the same or similar elements or elements with the same or similar functions throughout. The embodiments described below with reference to the drawings are exemplary and are intended to explain the present invention and should not be construed as limiting the present invention. In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", "axial", "radial", "circumferential", etc. indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be construed as limiting the present invention. For example, in one scenario, the wafer can be set horizontally or vertically as needed. Correspondingly, the lens module and the distance detection module can be set up and down or left and right, front and back accordingly. The present application does not make specific limitations on this.

[0079] In the present invention, unless otherwise clearly specified and defined, the terms "install", "connect", "connect", "fix", etc. should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or integrated; it can be a mechanical connection or an electrical connection; it can be directly connected or indirectly connected through an intermediate medium, and it can be the communication inside two elements or the interaction relationship between two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0080] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than limiting the protection scope of the present invention. Although the present invention has been described in detail with reference to the preferred embodiments, those of ordinary skill in the art should understand that the technical solutions of the present invention can be modified or equivalently replaced without departing from the essence and scope of the technical solutions of the present invention.

Claims

1. A real-time focusing device for wafer detection, characterized in that, Comprising: A lens module, a controller, and a distance detection module; wherein, the lens module and the distance detection module are arranged vertically opposite to each other, and there is a gap for placing a wafer between the lens module and the distance detection module; The lens module is used for taking an image of the detection surface of the wafer; The distance detection module is used for detecting the undulation change information of the back surface of the wafer and transmitting the undulation change information to the controller; The controller is used for calculating the movement compensation amount of the lens module according to the received undulation change information and sending a movement control signal to the lens module according to the calculated movement compensation amount; The lens module includes a movement axis and a lens; the movement axis is used for controlling the lens to move away from or close to the wafer on the movement axis according to the received movement control signal; The lens module is also used for adjusting the distance between the lens and the wafer surface according to the received movement control signal; The distance detection module is used for detecting the distance between itself and the back surface of the wafer and transmitting the obtained distance information to the controller, and the controller calculates the movement compensation amount according to the received distance information; the distance detection module includes a distance sensor; wherein, When the wafer is a transparent film or semi-transparent, the distance sensor is used for detecting the first distance between itself and the back surface of the wafer and the second distance between itself and the front surface of the wafer through the wafer, and transmitting the obtained first distance and second distance to the controller; The controller calculates the movement compensation amount according to the received first distance and second distance.

2. The real-time focusing device for wafer detection according to claim 1, characterized in that, The movement axis is arranged facing the gap, and the lens is connected to the movement axis.

3. The real-time focusing device for wafer detection according to claim 1, characterized in that, It further includes a placement module, and the placement module is used for fixing the wafer in the gap between the lens module and the distance detection module.

4. A focusing method based on the real-time focusing device for wafer detection according to any one of claims 1-3, characterized in that, Comprising: The controller controls the lens module and the distance detection module to move to any position of the wafer simultaneously for detection; During the detection process, the distance detection module acquires the undulation change information of the back surface of the wafer and transmits the undulation change information to the controller; The controller calculates the movement compensation amount of the lens module according to the received undulation change information and sends a movement control signal to the lens module according to the calculated movement compensation amount; The lens module adjusts the distance between the lens and the wafer surface according to the received movement control signal.

5. The focusing method for wafer detection according to claim 4, characterized in that, The controller calculates the movement compensation amount of the lens module according to the received undulation change information, including: The controller calculates the distance change amount between the distance detection module and the back surface of the wafer according to the distance data fed back by the received distance detection module, and obtains the corresponding movement compensation amount according to the obtained distance change amount.

6. The focusing method for wafer detection according to claim 5, characterized in that, When the controller calculates that the distance between the distance detection module and the back surface of the wafer decreases by a first length, the obtained movement compensation amount is that the lens moves closer to the detection surface of the wafer by a first length; When the controller calculates that the distance between the distance detection module and the back surface of the wafer increases by a second length, the obtained movement compensation amount is that the lens moves away from the detection surface of the wafer by a second length.

7. The focusing method for wafer detection according to claim 6, characterized in that, The controller sends corresponding control instructions to the movement axis of the lens module according to the obtained movement compensation amount, so that the movement axis controls the lens thereon to move closer to or away from the wafer by a corresponding length distance according to the movement compensation amount.

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