Precision transmission pre-alignment device and pre-alignment method

Abstract

The present invention provides a precision transmission pre-alignment device and a pre-alignment method, the device comprising: a temperature processing unit (2), comprising a flow plate (2.1), a Peltier element (2.3) and a cooling fan (2.4), used to adjust the gas bath gas to a target temperature by heating or cooling; a gas bath thermostat (1), comprising a gas filter (1.1), a gas bath fence (1.2) and a temperature sensor (1.3), used to uniformly transfer the gas bath gas to an internal chamber (1.6) and measure the temperature; the gas bath thermostat (1) and the temperature processing unit (2) are respectively connected through an air supply pipe (1.4) and a return air pipe (1.5) to allow the gas bath gas to circulate; a pre-alignment system (3), which is arranged in the internal chamber (1.6) of the gas bath thermostat (1). The pre-alignment device disclosed in the present invention has a small structure and uniform temperature distribution, and can simultaneously realize wafer pre-alignment, surface warpage detection and surface foreign matter detection.

Description

Technical Field

[0001] The present disclosure relates to the technical field of optical alignment, and in particular to a precision transmission pre-alignment device and a pre-alignment method. Background Art

[0002] The transmission results of the wafer transmission system will directly affect the accuracy and production efficiency of the whole machine. When the robot directly takes the wafer out of the wafer box, there will be random eccentricity and direction deflection at the millimeter level. If it is directly sent to the workpiece exposure station, it is obviously impossible to achieve precise alignment exposure.

[0003] Therefore, according to the current common process technology, when the robot takes the wafer out of the cassette, it will first place it on the pre-alignment device for position correction. The pre-alignment device has also evolved from the past mechanical pre-alignment to the optical pre-alignment. In order to improve the alignment accuracy and shorten the alignment time, mechanical pre-alignment and optical pre-alignment are also used in combination, but the equipment purchase cost is relatively high. Optical pre-alignment generally uses a CCD camera to scan the edge contour or notch. The offset repeatability accuracy can reach the micron level, and the angle repeatability accuracy can reach the arc minute level. If you want to further improve the rotational alignment accuracy to the arc second level, the existing system structure is difficult to implement.

[0004] For wafers with large area and thin thickness, their surface shape is easily affected by temperature, which causes the shape and position of the marks on the wafer to change. Therefore, the temperature of the optical alignment process needs to be controlled.

[0005] In addition, the current pre-alignment device has a single function and can only pre-adjust the wafer position. Summary of the invention

[0006] 1. Technical issues to be resolved

[0007] In view of the above problems, the present disclosure provides a precision transmission pre-alignment device and a pre-alignment method, which are used to solve the technical problems of traditional devices such as limited detection accuracy, susceptibility to temperature influence, and single function.

[0008] (II) Technical solution

[0009] On the one hand, the present disclosure provides a precision transmission pre-alignment device, including: a temperature processing unit, including a flow equalizing plate, a Peltier element and a cooling fan, for adjusting the gas bath gas to a target temperature by heating or cooling; an air bath thermostat, including a gas filter, an air bath fence and a temperature sensor, for uniformly transferring the gas bath gas to an internal chamber and measuring the temperature; the air bath thermostat is connected to the temperature processing unit through an air supply duct and a return air duct, respectively, so that the air bath gas can circulate; and a pre-alignment system is arranged in the internal chamber of the air bath thermostat.

[0010] Furthermore, the pre-alignment system includes: a coarse alignment camera, used to detect marks on the wafer for coarse alignment of the wafer; a fine alignment camera, used to detect marks on the wafer for fine alignment of the wafer; a camera adjustment mechanism, used to respectively adjust the posture and position of the coarse alignment camera and the fine alignment camera; a 4-degree-of-freedom displacement system, including an xy motion platform, a z motion platform and a rotating platform rotating around the z-axis, for adjusting the posture and position of the wafer.

[0011] Furthermore, the rotating platform rotating around the z-axis includes: a wafer holding table; a vacuum pipeline, which passes through a ventilation pipe installed in the center of the rotating platform rotating around the z-axis to adsorb the wafer; the ventilation pipe, one end of which forms a static sealing structure with the bottom end cover through an O-ring, and the other end of which forms a dynamic sealing structure with the wafer holding table through a pan seal ring.

[0012] Furthermore, the precision transmission pre-alignment device also includes: a folding mirror, which is used to fold the optical path 90 degrees to detect the wafer; and a surface detection system, which is used to perform surface detection and surface cleanliness detection on the wafer.

[0013] Furthermore, the temperature processing unit further comprises: a heat sink, which is arranged at one end of the non-working surface of the Peltier element and is used to exchange cold or heat opposite to the working surface of the Peltier element.

[0014] On the other hand, the present disclosure provides a method for pre-alignment according to the aforementioned precision transmission pre-alignment device, including: S1, using a temperature processing unit and an air bath constant temperature box to provide a constant temperature environment for the pre-alignment system; S2, using a camera adjustment mechanism in the pre-alignment system to respectively adjust the relative position relationship between the coarse alignment camera, the fine alignment camera and the wafer stage; S3, using the coarse alignment camera to obtain the first coordinate of the wafer mark to perform coarse alignment of the wafer; S4, causing the wafer stage to drive the wafer to move a first distance along the x-axis, using the fine alignment camera to obtain the second coordinate of the wafer mark to perform fine alignment of the wafer.

[0015] Furthermore, a unique mark A is provided on the wafer, and S3 and S4 include: S311, causing the wafer stage to drive the wafer to rotate one circle, and using a coarse alignment camera to obtain the trajectory of mark A; S312, calculating the coordinates of the wafer center O and the first angle θ of the line connecting the mark A and the wafer center O relative to the x-axis based on the trajectory; S313, moving the wafer center O to the initial coordinates of the wafer stage center, and causing mark A to fall on the x-axis to complete the coarse alignment of the wafer; S411, causing the wafer stage to drive the wafer to move a first distance along the x-axis, using a fine alignment camera to obtain the second coordinates of mark A, and combining the coordinates of the wafer center O to calculate the second angle α of the line connecting mark A and the wafer center O relative to the x-axis; S412, causing the wafer stage to drive the wafer to rotate the second angle α to complete the fine alignment of the wafer.

[0016] Further, two marks A and B are provided on the wafer, and the center line of mark A and mark B does not pass through the center O of the wafer, S3 and S4 include: S321, using a coarse alignment camera to obtain the first coordinate of mark A; S322, using a coarse alignment camera to obtain the first coordinate of mark B; S323, according to the first coordinate of mark A and the first coordinate of mark B, calculate the first angle θ of the center line of mark A and mark B relative to the x-axis; S324, the wafer stage drives the wafer to rotate the first angle θ to complete the coarse alignment of the wafer; S421, using a fine alignment camera to obtain the second coordinate of mark B, the wafer stage drives the wafer to move the first distance along the x-axis, so that mark A appears in the field of view of the fine alignment camera, at this time, the first distance P is the projection of the line connecting mark A and mark B on the x-axis; S422, according to the first distance and the preset relationship between mark A and mark B, calculate the second angle α of the center line connecting mark A and mark B relative to the x-axis; S423, the wafer stage drives the wafer to rotate the second angle α to complete the fine alignment of the wafer.

[0017] Furthermore, two marks A and B are provided on the wafer, and the center line of mark A and mark B passes through the center O of the wafer, S3 and S4 include: S331, using a coarse alignment camera to obtain the first coordinate of mark A; S332, using a coarse alignment camera to obtain the first coordinate of mark B; S333, according to the first coordinate of mark A and the first coordinate of mark B, calculate the first coordinate of the center O of the wafer and the first angle θ of the center line of mark A and mark B relative to the x-axis; S334, the wafer stage drives the wafer to rotate the first angle θ to complete the coarse alignment of the wafer; S431, the wafer stage drives the wafer to move along the x-axis, and uses the fine alignment camera to sequentially obtain the second coordinate of mark B and the second coordinate of mark A, calculate the second coordinate of the center O of the wafer and the second angle α of the center line of mark A and mark B relative to the x-axis; S432, move the center O of the wafer to the coordinate of the center of the fine alignment camera, and drive the wafer stage to rotate the second angle α to complete the fine alignment of the wafer.

[0018] Another aspect of the present disclosure provides a method for pre-alignment based on the aforementioned precision transmission pre-alignment device, characterized in that it includes: S1, using a temperature processing unit and an air bath constant temperature box to provide a constant temperature environment for the pre-alignment system; S2, using a camera adjustment mechanism in the pre-alignment system to respectively adjust the relative position relationship between the coarse alignment camera, the fine alignment camera and the wafer stage; S3, using the coarse alignment camera to obtain the edge contour and notch coordinates of the wafer to perform coarse alignment of the wafer: S4, allowing the wafer stage to drive the wafer to move a first distance along the x-axis, using the fine alignment camera to obtain the second coordinates of the image mark that has been exposed on the wafer, and performing fine alignment of the wafer.

[0019] (III) Beneficial effects

[0020] The precision transmission pre-alignment device and pre-alignment method disclosed in the present invention utilizes an air bath thermostat and a temperature processing unit, and adopts an air bath temperature control method to ensure that the temperature distribution in the box is uniform and stable; specifically, a semiconductor refrigeration method is adopted to achieve precise temperature control, and the temperature regulation efficiency is high. Furthermore, by performing the rough alignment and fine alignment processes separately, the rotation alignment accuracy can reach the arc second level, and the working time is shorter, the overall structure is simpler, and the equipment cost is lower. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 The structure diagram of the precision transmission pre-alignment device according to the embodiment of the present disclosure is schematically shown;

[0022] Figure 2 The external overall structure diagram of the precision transmission pre-alignment device according to the embodiment of the present disclosure is schematically shown;

[0023] Figure 3 The schematic diagram of the structure of the pre-alignment system in the precision transmission pre-alignment device according to the embodiment of the present disclosure is shown;

[0024] Figure 4 A schematic diagram of the structure of a vacuum adsorption passage in a pre-alignment system according to an embodiment of the present disclosure is shown;

[0025] Figure 5 The internal structure of the gas bath thermostat according to the embodiment of the present disclosure is schematically shown;

[0026] Figure 6 A schematic diagram showing a detection principle diagram of a surface shape detection system according to an embodiment of the present disclosure is shown;

[0027] Figure 7 The following schematically shows the adjustment process of the alignment scheme 1 according to the embodiment of the present disclosure;

[0028] Figure 8 The following schematically shows the adjustment process of the alignment scheme 2 according to the embodiment of the present disclosure;

[0029] Fig. 9 The following schematically shows the adjustment process of the alignment scheme 3 according to the embodiment of the present disclosure;

[0030] Description of reference numerals:

[0031] 1. Gas bath thermostat; 1.1. Gas filter; 1.2. Gas bath fence; 1.3. Temperature sensor; 1.4. Air supply duct; 1.5. Air return duct; 1.6. Internal chamber; 2. Temperature processing unit; 2.1. Flow equalizer; 2.2. Radiator; 2.3. Peltier element; 2.4. Cooling fan; 3. Pre-alignment system; 3.1. Coarse alignment camera; 3.2. Fine alignment camera; 3.3. Camera adjustment mechanism; 3.4. Wafer; 3.5. Rotating platform rotating around z-axis; 3.5.1. Wafer stage; 3.5.2. Pan Seal; 3.5.3. Ventilation duct; 3.5.4. High-precision rotating mechanism; 3.5.5. O-ring; 3.5.6. Bottom end cover; 3.6. z motion platform; 3.7. xy motion platform; 3.8. Vacuum pipeline; 4. Surface detection system; 5. Folding mirror. DETAILED DESCRIPTION

[0032] In order to make the objectives, technical solutions and advantages of the present disclosure more clearly understood, the present disclosure is further described in detail below in combination with specific embodiments and with reference to the accompanying drawings.

[0033] The terms used herein are only for describing specific embodiments and are not intended to limit the present disclosure. The terms "comprise", "include", etc. used herein indicate the existence of the features, steps, operations and / or components, but do not exclude the existence or addition of one or more other features, steps, operations or components.

[0034] It should be noted that if directional indication is involved in the embodiments of the present disclosure, the directional indication is only used to explain the relative position relationship, movement status, etc. between the components in a certain specific posture. If the specific posture changes, the directional indication will also change accordingly.

[0035] The ordinal numbers used in the specification and claims, such as "first", "second", "third", etc., to modify the corresponding elements, do not themselves mean or represent any ordinal number of the element, nor do they represent the order of one element and another element, or the order of manufacturing methods. The use of these ordinal numbers is only used to clearly distinguish a component with a certain name from another component with the same name.

[0036] The present disclosure provides a precision transmission pre-alignment device, see Figure 1-2, including: a temperature processing unit 2, including a flow equalizing plate 2.1, a Peltier element 2.3 and a cooling fan 2.4, for adjusting the gas bath gas to a target temperature by heating or cooling; a gas bath thermostat 1, including a gas filter 1.1, a gas bath fence 1.2 and a temperature sensor 1.3, for uniformly transferring the gas bath gas to an internal chamber 1.6 and measuring the temperature; the gas bath thermostat 1 and the temperature processing unit 2 are connected to each other through an air supply pipe 1.4 and a return air pipe 1.5, respectively, so that the gas bath gas can circulate; a pre-alignment system 3, arranged in the internal chamber 1.6 of the gas bath thermostat 1.

[0037] like Figure 2 As shown in FIG. 1 , the overall external structure of the precision transmission pre-alignment device consists of two parts: an air bath thermostat 1 and a temperature processing unit 2. The air bath thermostat 1 is composed of a heat-insulating material (such as polyurethane foam) and a metal shell; the temperature processing unit 2 adopts semiconductor refrigeration technology, that is, a Peltier element 2.3 is used as a temperature regulator to adjust the air bath gas to the target temperature by heating or cooling, thereby achieving precise temperature control. The specific structure is shown in FIG. Figure 1 As shown, the gas bath thermostat 1 is provided with a gas filter 1.1, a gas bath fence 1.2 and an internal chamber 1.6 for placing the pre-alignment system 3, and a temperature sensor 1.3 for temperature measurement is installed on the chamber wall. The temperature processing unit 2 is provided with a flow plate 2.1, a Peltier element 2.3 and a cooling fan (or air supply fan) 2.4, wherein the temperature in the temperature processing unit 2 can be changed by controlling the magnitude and flow direction of the current of the Peltier element 2.3.

[0038] The air bath thermostat 1 and the temperature treatment unit 2 are connected through the air supply pipe 1.4 and the return air pipe 1.5. The fresh air entering through the air supply pipe 1.4 is filtered by the gas filter 1.1 on the top, and then is evenly blown through the air bath fence 1.2, so that the gas can be evenly transferred to the pre-alignment system 3, avoiding the influence of turbulence on the working condition of the pre-alignment system 3; the return air in the air bath thermostat re-enters the temperature treatment unit 2 through the return air pipe 1.5, and after the return air is temperature-adjusted by the Peltier unit 2.3, it is evenly blown through the flow equalizing plate 2.1, and then returns to the air bath thermostat 1 through the air supply pipe 1.4.

[0039] The precision transmission pre-alignment device disclosed in the present invention uses air bath adjustment for temperature control, which has higher precision and can make the temperature distribution of the entire internal space of the device uniform, providing a stable working environment for the optical components inside the device, which helps to improve the accuracy of detection; secondly, the entire device is a partially closed environment, which helps to maintain internal cleanliness; finally, the constant temperature environment can make the temperature of the wafer more accurately controlled when it is placed on the worktable, reduce the deformation of the wafer due to temperature, and improve the accuracy of overlay. In addition, the semiconductor refrigeration method is adopted, which has a simple structure, does not require a refrigeration medium, has a small size, is flexible to control, has a small thermal inertia, and has a high temperature regulation efficiency.

[0040] Based on the above embodiments, Figure 3 As shown, the pre-alignment system 3 includes: a coarse alignment camera 3.1, used to detect marks on the wafer to perform coarse alignment on the wafer 3.4; a fine alignment camera 3.2, used to detect marks on the wafer to perform fine alignment on the wafer 3.4; a camera adjustment mechanism 3.3, used to adjust the posture and position of the coarse alignment camera 3.1 and the fine alignment camera 3.2 respectively; a 4-DOF displacement system, including an xy motion platform 3.7, a z motion platform 3.6 and a rotating platform 3.5 rotating around the z-axis, for adjusting the posture and position of the wafer 3.4.

[0041] The coarse alignment camera 3.1 uses a linear array CCD camera, and the fine alignment camera 3.2 uses an area array CCD camera; the camera adjustment mechanism 3.3 is used to adjust the posture and position of the CCD camera, and can achieve adjustment and movement in the x, y and z directions. For wafers of different sizes and mark position information, compatibility can be achieved by adjusting the micro-motion stage and the relative position relationship between the CCD camera and the wafer stage.

[0042] Before the calibration system works for the first time, the position and posture of the CCD camera relative to the wafer can be adjusted with multiple degrees of freedom. According to the wafer size and the marks on the wafer, the camera adjustment mechanism 3.3 is used to adjust the relative position relationship of the coarse alignment camera 3.1, the fine alignment camera 3.2 and the wafer stage (that is, to clarify the coordinates of the center of the CCD camera in the entire system, which is convenient for the subsequent acquisition of the coordinates of the marking points), so that the marks on the wafer are located in the field of view of the coarse alignment camera 3.1, and the marks on the wafer can be located in the field of view of the fine alignment camera 3.2 after the coarse alignment adjustment is completed. After debugging, the camera adjustment mechanism 3.3 is locked, and no further adjustment is required under the same wafer and exposure field conditions.

[0043] Compared with the existing pre-alignment devices, the precision transmission pre-alignment device disclosed in the present invention combines the functions of coarse alignment and fine alignment, which can not only improve the alignment accuracy but also save time and effectively control the cost.

[0044] On the basis of the above-mentioned embodiment, the rotating platform 3.5 rotating around the z-axis includes: a wafer holding table 3.5.1; a vacuum pipeline 3.8, which passes through a ventilation pipe 3.5.3 installed in the center of the rotating platform 3.5 rotating around the z-axis to adsorb the wafer 3.4; the ventilation pipe 3.5.3, one end of which forms a static sealing structure with the bottom end cover 3.5.6 through an O-ring 3.5.5, and the other end of which forms a dynamic sealing structure with the wafer holding table 3.5.1 through a universal sealing ring 3.5.2.

[0045] Figure 4The specific structure diagram of the vacuum adsorption passage is shown in FIG. 3. The high-precision rotating mechanism 3.5.4 adopts a hollow passage design. The vacuum pipeline 3.8 can pass through the ventilation pipe 3.5.3, through the high-precision rotating mechanism 3.5.4 and the wafer holding table 3.5.1. In order to ensure the sealing performance, the present invention adopts two forms of O-ring sealing and universal seal. The ventilation pipe 3.5.3 and the bottom end cover 3.5.6 are statically sealed at the end by the O-ring 3.5.5, and the wafer holding table 3.5.1 and the ventilation pipe are statically sealed by the universal seal ring 3.5.2. The plate carrier 3.5.1 and the ventilation duct 3.5.3 are dynamically sealed; the bearing table 3.5.1 and the ventilation duct 3.5.3 are matched with the shaft hole clearance, and the universal seal ring 3.5.2 first plays the role of sealing. Due to its special structure, the greater the pressure difference on both sides of the seal, the larger the opening of its U-shaped cross section, and the greater the sealing force. In addition, since its sealing material is Teflon, it has good wear-resistant guiding performance and is flexibly connected to the ventilation duct 3.5.3, it can be guided and automatically centered, which reduces the requirements for the processing accuracy of the ventilation duct 3.5.3.

[0046] The structure of the Varisal seal ring is adopted. Compared with the static seal of the O-ring, the Varisal seal ring will not produce particle impurities after a long period of sliding friction. Under the working conditions of the static seal of the O-ring, rubber powder particles will be produced, which is not allowed in the semiconductor industry with strict requirements on cleanliness. In addition, the ventilation duct is arranged inside the high-precision rotating mechanism. Compared with arranging it on the external side, the influence of the ventilation duct on the rotation accuracy can be minimized during rotation.

[0047] The present invention designs a vacuum sealing air path structure based on a pre-alignment position adjustment mechanism, reduces the spatial size of the structure, increases the reliability of the seal, and avoids the influence of the ventilation duct on the movement accuracy of the motion platform.

[0048] Based on the above embodiment, the precision transmission pre-alignment device also includes: a folding mirror 5 for folding the optical path 90° to detect the wafer 3.4; a surface detection system 4 for performing surface detection and surface cleanliness detection on the wafer 3.4.

[0049] like Figure 5 As shown, the folding mirror 5 and the surface shape detection system 4 are also arranged in the internal chamber 1.6 of the gas bath thermostat 1, for simultaneously detecting the wafer 3.4. The folding mirror 5 can fold the light of the laser, which helps to reduce the outline volume of the whole system; the surface shape detection system 4 performs analysis and detection based on the principle of double-beam equal-thickness interference, such as Figure 6As shown, the laser light source is expanded and collimated, and is divided into reference light and test light through the reference surface. The test light is reflected to the surface of the wafer 3.4 through the folding mirror 5, and then reflected from the wafer 3.4 back to the inside of the surface detection system 4 and interferes with the reference light. The warpage value of the wafer surface can be analyzed based on the light and dark stripes generated by the interference. Subsequently, according to the measured warpage value, certain measures are taken to correct it before or on the exposure station to ensure the flatness of the wafer, which is of great significance for improving the transmission accuracy. In addition, the surface detection system 4 can also detect the cleanliness of the wafer surface at the same time. If there are foreign particles, the interference stripes will mutate at this position to avoid the subsequent process of the wafer being contaminated, resulting in a waste of resources.

[0050] Based on the above embodiment, the temperature processing unit 2 further comprises: a heat sink 2.2, which is arranged at one end of the non-working surface of the Peltier element 2.3 and is used to exchange cold or heat opposite to the working surface of the Peltier element 2.3.

[0051] By changing the direction of the current loaded on the Peltier element 2.3, the heating end and the cooling end can be interchanged, and the power (temperature) can be precisely adjusted by changing the current or voltage. The cooling fan 2.4 is installed at one end of the working surface of the Peltier element 2.3, and its main function is to generate air power to blow the heat or cold generated by the Peltier element 2.3 into the air bath thermostat 1; and the radiator 2.2 is installed at one end of the non-working surface of the Peltier element 2.3, and the cold or heat opposite to the working surface is exchanged in time to prevent the working efficiency of the Peltier element 2.3 from being reduced.

[0052] The precision transmission pre-alignment device disclosed in the present invention can simultaneously realize the functions of wafer pre-alignment, temperature control, surface warpage detection and surface foreign matter detection, can accurately control the temperature of the local closed system, perform coarse and fine alignment of the wafer, and can simultaneously detect the warpage value of the wafer and detect whether there are foreign matters on the wafer surface; the device has a high system integration and rich functions, and is of great significance for improving exposure resolution and overlay accuracy as well as the efficiency of the entire system.

[0053] The present disclosure also provides a method for pre-alignment according to the aforementioned precision transmission pre-alignment device, comprising: S1, using the temperature processing unit 2 and the gas bath constant temperature box 1 to provide a constant temperature environment for the pre-alignment system 3; S2, using the camera adjustment mechanism 3.3 in the pre-alignment system 3 to respectively adjust the relative position relationship between the coarse alignment camera 3.1, the fine alignment camera 3.2 and the wafer stage 3.5.1; S3, using the coarse alignment camera 3.1 to obtain the first coordinate of the wafer mark to perform coarse alignment of the wafer; S4, allowing the wafer stage 3.5.1 to drive the wafer 3.4 to move a first distance along the x-axis, and using the fine alignment camera 3.2 to obtain the second coordinate of the wafer mark to perform fine alignment of the wafer.

[0054] The pre-alignment method includes two main steps: coarse alignment and fine alignment. The deflection angle after coarse alignment debugging can only represent that it has been fully corrected at the coarse alignment level, but in fact, a smaller deflection angle still exists after coarse adjustment. First, coarse alignment is performed using the coarse alignment camera 3.1, and then the wafer 3.4 is moved along the x-axis for a first distance. The deflection angle can be calculated based on the coordinate change, so as to perform fine alignment. The rotation alignment accuracy of this method can reach the arc second level, and the working time is shorter, the overall structure is simpler, and the equipment cost is lower.

[0055] Based on the above embodiment, the alignment scheme 1 is as follows Figure 7 As shown, a unique mark A is provided on the wafer 3.4, and S3 and S4 include: S311, causing the wafer stage 3.5.1 to drive the wafer 3.4 to rotate one circle, and using the coarse alignment camera 3.1 to obtain the trajectory of the mark A; S312, calculating the coordinates of the wafer center O and the first angle θ of the line connecting the mark A and the wafer center O relative to the x-axis according to the trajectory; S313, moving the wafer center O to the initial coordinates of the center of the wafer stage 3.5.1, and making the mark A fall on the x-axis to complete the coarse alignment of the wafer; S411, causing the wafer stage 3.5.1 to drive the wafer 3.4 to move a first distance along the x-axis, using the fine alignment camera 3.2 to obtain the second coordinates of the mark A, and combining the coordinates of the wafer center O, calculating the second angle α of the line connecting the mark A and the wafer center O relative to the x-axis; S412, causing the wafer stage 3.5.1 to drive the wafer 3.4 to rotate the second angle α to complete the fine alignment of the wafer.

[0056] The specific steps of alignment scheme 1 are as follows: the robot places the wafer 3.4 on the wafer stage 3.5.1, the center O of the wafer is eccentric to the center W of the wafer stage, and the initial coordinates of the center W of the wafer stage are (x0, y0); the distance between the only mark A on the wafer 3.4 and the center O of the wafer is n. S311, the wafer stage 3.5.1 rotates one circle driven by the rotating platform 3.5 rotating around the z-axis, and the coarse alignment camera 3.1 successfully scans the trajectory of the mark A on the wafer; S312, the coordinates (x1, y1) of the wafer center O and the first angle θ of the line connecting the mark A and the wafer center O relative to the x-axis are calculated based on the trajectory; S313, the program calculates the relative position of the wafer center O (x1, y1) relative to the initial coordinates (x0, y0) of the wafer stage center W, and the 4-DOF displacement system under the wafer 3.4 performs associated motion to move the wafer center O to (x0, y0), and rotates the wafer 3.4 by the first angle θ with (x0, y0) as the center, so that the A mark falls on the x-axis (at the correction level that can be achieved by coarse alignment), and the coordinates of the wafer stage center W become (2x0-x1, 2y0-y1); the coarse alignment is now completed.

[0057] S411, the wafer stage 3.5.1 drives the wafer 3.4 to move a first distance m along the x-axis, and the coordinate of the wafer center O becomes (x0+m, y0); mark A appears in the field of view of the precision alignment camera 3.2. After the above-mentioned rough adjustment, there is still a second angle α between the line connecting mark A and the wafer center O and the x-axis. The actual coordinate of mark A is (x0+m+Δx, y0+Δy). Therefore, relative to the wafer center coordinate O (x0+m, y0), the rotation angle tanα=Δy / Δx; S412, the high-precision rotating mechanism 3.5.4 rotates the wafer 3.4 by α relative to the center (x0+m, y0) so that mark A is on the x-axis, and the precision alignment process ends.

[0058] Based on the above embodiment, alignment scheme 2 is as follows Figure 8 As shown, two marks A and B are provided on the wafer 3.4, and the center line of the mark A and the mark B does not pass through the center O of the wafer. S3 and S4 include: S321, using the coarse alignment camera 3.1 to obtain the first coordinate of the mark A; S322, using the coarse alignment camera 3.1 to obtain the first coordinate of the mark B; S323, according to the first coordinate of the mark A and the first coordinate of the mark B, calculate the first angle θ of the center line of the mark A and the mark B relative to the x-axis; S324, the wafer stage 3.5.1 drives the wafer 3.4 to rotate the first angle θ to complete the wafer coarse alignment. Accurate; S421, use the precision alignment camera 3.2 to obtain the second coordinate of mark B, the wafer stage 3.5.1 drives the wafer 3.4 to move a first distance along the x-axis, so that mark A appears in the field of view of the precision alignment camera 3.2. At this time, the first distance P is the projection of the line connecting mark A and mark B on the x-axis; S422, according to the first distance and the preset relationship between mark A and mark B, calculate the second angle α of the center line of mark A and mark B relative to the x-axis; S423, the wafer stage 3.5.1 drives the wafer 3.4 to rotate the second angle α to complete the wafer precision alignment.

[0059] The specific steps of alignment scheme 2 are as follows: S321, use the coarse alignment camera 3.1 to obtain the first coordinate of mark A; S322, use the coarse alignment camera 3.1 to obtain the first coordinate of mark B; S323, according to the coordinates of mark A and mark B, obtain the first angle O of the line connecting the two points deviating from the x-axis; S324, make the wafer stage 3.5.1 drive the wafer 3.4 to rotate so that the line connecting the two points A and B in the image data collected by the coarse alignment camera 3.1 is parallel to the x-axis; at this point, the coarse alignment is completed.

[0060] S421, the precision alignment camera 3.2 collects the second coordinate (xb, yb) of mark B, and then the wafer stage 3.5.1 drives the wafer 3.4 to move the first distance P along the x-axis, so that mark A appears in the field of view of the precision alignment camera 3.2. At this time, the first distance P is the projection of the line connecting mark A and mark B on the x-axis; S422, according to the preset relationship between mark A and mark B, it can be known that the actual distance between the two marks is P1; the rotation angle α of precision alignment is expressed as: cos α=P / P1; S423, the wafer stage 3.5.1 drives the wafer 3.4 to rotate the second angle α to complete the wafer precision alignment.

[0061] Compared with alignment scheme 1, alignment scheme 2 uses two marks. The final calculation of the precise alignment deflection angle is only related to the relative positions of A and B, and has nothing to do with the coordinates of the center of the wafer. Therefore, the deflection angle accuracy will be higher; but alignment scheme 2 uses two marks, which is relatively cumbersome and takes longer time to align.

[0062] Based on the above embodiment, alignment scheme 3 is as follows Fig. 9 As shown, two marks A and B are provided on the wafer 3.4, and the center line of the mark A and the mark B passes through the wafer center O. S3 and S4 include: S331, using the coarse alignment camera 3.1 to obtain the first coordinate of the mark A; S332, using the coarse alignment camera 3.1 to obtain the first coordinate of the mark B; S333, according to the first coordinate of the mark A and the first coordinate of the mark B, calculate the first coordinate of the wafer center O and the first angle θ of the center line of the mark A and the mark B relative to the x-axis; S334, move the wafer center O to the initial coordinate of the wafer stage center, and make the wafer stage 3.5.1 drive the wafer 3.4 to rotate the first angle θ, and complete the wafer alignment. Rough circle alignment; S431, make the wafer stage 3.5.1 drive the wafer 3.4 to move a first distance P along the x-axis, use the precision alignment camera 3.2 to obtain the second coordinate of mark B and the second coordinate of mark A in turn, so that mark A appears in the field of view of the precision alignment camera 3.2. At this time, the first distance P is the projection of the line connecting mark A and mark B on the x-axis; calculate the second coordinate of the wafer center O and the second angle α of the center line connecting mark A and mark B relative to the x-axis; S432, move the wafer center O to the coordinate of the center of the precision alignment camera 3.2, and make the wafer stage 3.5.1 drive the wafer 3.4 to rotate the second angle α to complete the wafer precision alignment.

[0063] The specific steps of alignment scheme 3 are as follows: Steps S331 to S333 of alignment scheme 3 correspond one to one with steps S321 to S323 of alignment scheme 2, and will not be repeated here. In the coarse alignment step S334, the center O of the wafer is moved to the initial coordinates of the center of the wafer table, and the wafer table 3.5.1 drives the wafer 3.4 to rotate the first angle θ to complete the coarse alignment of the wafer. On the basis of S331 to S334, the center can be fine-tuned again in the subsequent fine alignment process. It should be noted that the center and angle after the coarse alignment can only represent that they have been fully corrected at the coarse alignment level, but in fact, the center O of the wafer after coarse alignment is still eccentric with the center W of the wafer table, and a smaller deflection angle still exists.

[0064] S431, the coordinate point U (x0', y0') of the center of the high-power lens precision alignment camera 3.2; the wafer stage 3.5.1 drives the wafer 3.4 to move along the x-axis, and based on the adjustment of the coarse alignment, the actual coordinates of the mark B (xb, yb) can be collected in the field of view of the precision alignment camera 3.2; the wafer stage 3.5.1 drives the wafer 3.4 to continue to move the first distance P along the x-axis, and the actual coordinates of the mark A collected by the precision alignment camera 3.2 are (xa, ya), and the first distance P is the projection of the line connecting the mark A and the mark B on the x-axis; S432, according to the geometric relationship between the mark A, the mark B and the center O of the wafer, the coordinates of the actual center O can be calculated, and then the center O of the wafer can be more accurately adjusted to the coordinate U (x0', y0') of the center of the precision alignment camera 3.2; in addition, according to the preset relationship between the mark A and the mark B, it can be known that their distance is P1, so the adjusted rotation angle is cosα=P / P 1 ; The wafer stage 3.5.1 drives the wafer 3.4 to rotate at the second angle α to complete the wafer fine alignment. Finally, the robot takes the wafer from the center of the circle after fine alignment calibration.

[0065] Compared with Alignment Scheme 2, Alignment Scheme 3 adds a step of re-aligning the center of the wafer during the fine alignment process, which ensures the positioning accuracy of the center of the wafer while ensuring the deflection angle. However, because of the addition of the fine alignment process of the center, Alignment Scheme 3 takes longer.

[0066] The present disclosure also provides a method for pre-alignment according to the aforementioned precision transmission pre-alignment device, comprising: S1, using the temperature processing unit 2 and the gas bath constant temperature box 1 to provide a constant temperature environment for the pre-alignment system 3; S2, using the camera adjustment mechanism 3.3 in the pre-alignment system 3 to respectively adjust the relative position relationship between the coarse alignment camera 3.1, the fine alignment camera 3.2 and the wafer stage 3.5.1; S3, using the coarse alignment camera 3.1 to obtain the edge contour and notch coordinates of the wafer 3.4, and perform coarse alignment of the wafer; S4, allowing the wafer stage 3.5.1 to drive the wafer 3.4 to move a first distance along the x-axis, and using the fine alignment camera 3.2 to obtain the second coordinates of the image mark that has been exposed on the wafer 3.4, and perform wafer fine alignment.

[0067] Alignment scheme 4 does not require any prior marking on the wafer, and the specific steps are as follows: only rough alignment of the wafer is performed during the first exposure, and the edge contour and notch information of wafer 3.4 are scanned by using a rough alignment camera 3.1 (alignment scheme 1 does not use notches and edges, but scans the contour of mark A), and wafer 3.4 is roughly aligned, and then sent to the workpiece stage for exposure by a robot.

[0068] The wafer after the first exposure is pre-aligned again. As above, the edge and notch information of wafer 3.4 needs to be used for coarse alignment; and in the fine alignment process, the exposed image on the wafer is directly used as a mark (that is, replacing mark A and mark B in alignment scheme 3). The subsequent alignment and calculation process is similar to alignment scheme 3 and will not be repeated here.

[0069] In the calculation formula for the deflection angle of the above four alignment schemes, since there is an order of magnitude difference between the numerator and the denominator, the accuracy of the correction angle α obtained by the precise alignment is very high. The alignment method disclosed in the present invention does not directly align to the arc second level in one step, but is divided into two steps of coarse alignment and fine alignment. Compared with the one-step alignment to the arc second level, the working time is shorter, the overall structure is simple, and the equipment cost is low.

[0070] The complete process of the above-mentioned pre-alignment method using the precision transmission pre-alignment device is described below. The robot takes out the wafer 3.4 from the cassette, the automatic door of the pre-processing system 3 opens, and the robot places the wafer 3.4 on the wafer stage 3.5.1 of the pre-alignment system 3. The vacuum vents on the wafer stage 3.5.1 act to suck the wafer 3.4 tightly. The pre-alignment system 3 performs rough and fine adjustments of the posture according to the above steps. At the same time, the surface detection system 4 detects and analyzes the surface shape and surface cleanliness of the wafer 3.4. After the posture adjustment and surface detection are completed, the vacuum adsorption of the wafer stage 3.5.1 is released, the robot takes out the wafer 3.4, and the automatic door of the pre-alignment system 3 closes, completing the entire alignment and detection process.

[0071] The precision transmission pre-alignment device disclosed in the present invention can simultaneously realize the functions of wafer pre-alignment, temperature control, surface warpage detection and surface foreign matter detection; based on the pre-alignment system, a vacuum sealing gas path structure is designed to reduce the spatial size of the structure, increase the reliability of the seal, and avoid the influence of the ventilation duct on the motion accuracy of the motion stage. The pre-alignment method disclosed in the present invention takes into account the functions of coarse alignment and fine alignment, which can not only improve the alignment accuracy but also save time and effectively control the cost.

[0072] The specific embodiments described above further illustrate the purpose, technical solutions and beneficial effects of the present disclosure. It should be understood that the above description is only a specific embodiment of the present disclosure and is not intended to limit the present disclosure. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present disclosure should be included in the protection of the present disclosure.

Claims

1. A precision transmission pre-alignment device, characterized in that: include: A temperature processing unit (2), comprising a flow balancing plate (2.1), a Peltier element (2.3) and a cooling fan (2.4), for regulating the bath gas to a target temperature by heating or cooling; The gas bath thermostat (1) comprises a gas filter (1.1), a gas bath fence (1.2) and a temperature sensor (1.3), which is used to uniformly transfer the gas bath gas to the internal chamber (1.6) and measure the temperature; the gas bath thermostat (1) is connected to the temperature processing unit (2) through an air supply pipe (1.4) and an air return pipe (1.5) respectively, so that the gas bath gas can circulate; A pre-alignment system (3) is arranged in the inner chamber (1.6) of the gas bath thermostat (1); The pre-alignment system (3) comprises: a 4-DOF displacement system, including an xy motion platform (3.7), a z motion platform (3.6) and a rotating platform (3.5) rotating around a z axis, for adjusting the posture and position of the wafer (3.4); The rotating platform (3.5) rotating around the z-axis comprises: Film holder (3.5.1); A vacuum pipeline (3.8) passes through a ventilation pipe (3.5.3) installed at the center of the rotating platform (3.5) rotating around the z-axis to adsorb the wafer; The ventilation pipe (3.5.3) has one end formed with a static sealing structure through an O-ring (3.5.5) and a bottom end cover (3.5.6), and the other end formed with a dynamic sealing structure through a universal seal ring (3.5.2) and the wafer support table (3.5.1).

2. The precision transmission pre-alignment device according to claim 1, characterized in that: The pre-alignment system (3) comprises: A coarse alignment camera (3.1) is used to detect marks on the wafer to perform coarse alignment on the wafer (3.4); A precision alignment camera (3.2) for detecting marks on the wafer to perform precision alignment on the wafer (3.4); The camera adjustment mechanism (3.3) is used to respectively adjust the posture and position of the coarse alignment camera (3.1) and the fine alignment camera (3.2).

3. The precision transmission pre-alignment device according to claim 2, characterized in that: The precision transmission pre-alignment device also includes: A folding mirror (5) used to fold the optical path by 90° to detect the wafer (3.4); A surface shape detection system (4) is used to perform surface shape detection and surface cleanliness detection on the wafer (3.4).

4. The precision transmission pre-alignment device according to claim 1, characterized in that: The temperature processing unit (2) further comprises: The heat sink (2.2) is arranged at one end of the non-working surface of the Peltier element (2.3) and is used to exchange cold or heat opposite to the working surface of the Peltier element (2.3).

5. A method for pre-alignment according to the precision transmission pre-alignment device according to any one of claims 1 to 4, characterized in that: include: S1, using a temperature processing unit (2) and an air bath thermostat (1) to provide a constant temperature environment for a pre-alignment system (3); S2, using the camera adjustment mechanism (3.3) in the pre-alignment system (3) to respectively adjust the relative positional relationship between the coarse alignment camera (3.1), the fine alignment camera (3.2) and the film stage (3.5.1); S3, using the coarse alignment camera (3.1) to obtain the first coordinate of the wafer mark and perform coarse alignment of the wafer; S4, causing the wafer stage (3.5.1) to drive the wafer (3.4) to move a first distance along the x-axis, using the fine alignment camera (3.2) to obtain a second coordinate of the wafer mark, and performing fine alignment of the wafer.

6. The method for pre-alignment according to the precision transmission pre-alignment device according to claim 5, characterized in that: The wafer (3.4) is provided with a unique mark A, and the S3 and S4 include: S311, causing the wafer stage (3.5.1) to drive the wafer (3.4) to rotate one circle, and using the coarse alignment camera (3.1) to obtain the trajectory of the mark A; S312, calculating the coordinates of the wafer center O and a first angle θ between the line connecting the mark A and the wafer center O and the x-axis according to the trajectory; S313, moving the center O of the wafer to the initial coordinate of the center of the wafer stage (3.5.1), and making the mark A fall on the x-axis, completing the rough alignment of the wafer; S411, causing the wafer stage (3.5.1) to drive the wafer (3.4) to move a first distance along the x-axis, using the precision alignment camera (3.2) to obtain a second coordinate of the mark A, and combining the coordinate of the wafer center O to calculate a second angle α between the mark A and the wafer center O and the x-axis; S412, causing the wafer stage (3.5.1) to drive the wafer (3.4) to rotate at the second angle α, thereby completing wafer fine alignment.

7. The method for pre-alignment according to the precision transmission pre-alignment device according to claim 5, characterized in that: The wafer (3.4) is provided with two marks A and B, and the center line connecting the mark A and the mark B does not pass through the center O of the wafer, and the S3 and the S4 include: S321, using the coarse alignment camera (3.1) to acquire the first coordinate of the mark A; S322, using the coarse alignment camera (3.1) to acquire the first coordinate of the mark B; S323, calculating a first angle θ between the center line of the marker A and the center line of the marker B and the x-axis according to the first coordinate of the marker A and the first coordinate of the marker B; S324, causing the wafer stage (3.5.1) to drive the wafer (3.4) to rotate by the first angle θ, thereby completing rough alignment of the wafer; S421, using the precision alignment camera (3.2) to obtain the second coordinate of the mark B, the wafer stage (3.5.1) drives the wafer (3.4) to move a first distance along the x-axis, so that the mark A appears within the field of view of the precision alignment camera (3.2), and the first distance is the projection of the line connecting the mark A and the mark B on the x-axis; S422, calculating a second angle α between a center line of the marker A and the marker B and the x-axis according to the first distance and a preset relationship between the marker A and the marker B; S423, causing the wafer stage (3.5.1) to drive the wafer (3.4) to rotate at the second angle α, thereby completing wafer fine alignment.

8. The method for pre-alignment according to the precision transmission pre-alignment device according to claim 5, characterized in that: The wafer (3.4) is provided with two marks A and B, and the center line connecting the mark A and the mark B passes through the center O of the wafer, and the S3 and the S4 include: S331, using the coarse alignment camera (3.1) to acquire the first coordinate of the mark A; S332, using the coarse alignment camera (3.1) to acquire the first coordinate of the mark B; S333, calculating the first coordinate of the wafer center O and the first angle θ between the center line of the mark A and the mark B and the x-axis according to the first coordinate of the mark A and the first coordinate of the mark B; S334, causing the wafer stage (3.5.1) to drive the wafer center O to move to the initial coordinates of the wafer stage center, and causing the wafer (3.4) to rotate by the first angle θ, thereby completing wafer rough alignment; S431, causing the wafer stage (3.5.1) to drive the wafer (3.4) to move a first distance along the x-axis, using the precision alignment camera (3.2) to sequentially obtain the second coordinate of the mark B and the second coordinate of the mark A, and calculating the second coordinate of the wafer center O and the second angle α of the center line of the mark A and the mark B relative to the x-axis; S432, moving the center O of the wafer to the coordinates of the center of the fine alignment camera (3.2), and causing the wafer stage (3.5.1) to drive the wafer (3.4) to rotate by the second angle α, thereby completing wafer fine alignment.

9. A method for pre-alignment according to the precision transmission pre-alignment device according to any one of claims 1 to 4, characterized in that: include: S1, using a temperature processing unit (2) and an air bath thermostat (1) to provide a constant temperature environment for a pre-alignment system (3); S2, using the camera adjustment mechanism (3.3) in the pre-alignment system (3) to respectively adjust the relative positional relationship between the coarse alignment camera (3.1), the fine alignment camera (3.2) and the film stage (3.5.1); S3, using the coarse alignment camera (3.1) to obtain the edge profile and notch coordinates of the wafer (3.4) to perform coarse alignment of the wafer; S4, causing the wafer stage (3.5.1) to drive the wafer (3.4) to move a first distance along the x-axis, using the fine alignment camera (3.2) to obtain second coordinates of an image mark that has been exposed on the wafer (3.4), and performing fine alignment of the wafer.

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