Wafer non-contact flatness correction method

Abstract

The invention discloses a non-contact flatness correction method for a wafer, relates to the technical field of wafer calibration, and aims at the correction process of the wafer, and provides a lower supporting force for the lower side of a wafer body by taking gas as a soft medium. The key purpose is to forcibly drive the wafer to deform upwards by air pressure so as to counteract the downward bending deformation process caused by the gravity problem, the specific process is to fix the wafer in a negative-pressure adsorption mode, then air is continuously blown into the positive-pressure bin in a positive-pressure air blowing mode, and the key effect is that when the air is blown, the air is blown into the positive-pressure bin. Two actions of global positive pressure compensation and single-area positive pressure compensation are split, the environment pressure in a positive pressure bin is obtained in real time through a pressure sensor, the amount of blown-in gas is limited by simulating the environment pressure, the gas flow and the gas blowing mode are limited in a gradual increasing mode, and on the basis of correcting the planeness of a wafer, the planeness of the wafer is corrected. And secondary deformation damage is avoided.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of wafer calibration, in particular to a wafer non-contact flatness correction method. BACKGROUND

[0002] Wafer laser focusing technology is mainly used to solve the defocusing problem caused by the surface undulation of the wafer in semiconductor manufacturing. Currently, the main method is the flying spot method. An automatic focusing system uses 2X, 5X and 10X objective lenses to meet the clear imaging requirement of a horizontal displacement speed of 200 mm / s. The surface flatness of the test sample needs to be less than 12000 mu m. However, the thickness of the wafer sheet is relatively low (thick sheet < 200 mu m). Due to the relationship between the material and shape, when the surface flatness is greater than 12000 mu m, the automatic focusing cannot be achieved.

[0003] As for the wafer correction method, reference can be made to the related contents in CN116454001A and CN104718607A. The conventional adjustment method is mainly mechanical contact type. The essence is to pick up the wafer sheet and then adjust the structure position again. However, the wafer sheet material is special. The contact action will cause secondary scratching damage to the wafer sheet. In addition, due to the structure size characteristics of the wafer sheet, the direct contact adjustment structure will aggravate the deformation degree of the wafer sheet. Therefore, the present application provides a solution. SUMMARY

[0004] The purpose of the present application is to provide a wafer non-contact flatness correction method. The correction process of the wafer flatness is based on the material characteristics and structure size characteristics of the wafer. The mechanical contact adjustment structure will cause secondary damage to the wafer.

[0005] The purpose of the present application can be achieved by the following technical solution: a wafer non-contact flatness correction method using a correction platform and a laser focusing structure, including a negative pressure adsorption stage and a positive pressure leveling stage. In the negative pressure adsorption stage and the positive pressure leveling stage, the non-automatic focusing action is performed by the laser focusing structure. A placement platform for placing the wafer body is arranged on the correction platform. The placement platform corresponds to the internal position of the correction platform to form a positive pressure chamber. Negative pressure ports and positive pressure ports are arranged in the placement platform and the positive pressure chamber, respectively. A pressure sensing assembly for detecting the environmental pressure is arranged in the positive pressure chamber. In the positive pressure leveling stage, the global positive pressure compensation action and the single area positive pressure compensation action are subdivided. In the positive pressure leveling stage, the positive pressure chamber is filled with positive pressure air through the positive pressure port. The wafer body is provided with an upward force by the gas pressure.

[0006] Further, the surface position of the placement platform is provided with a hole sealing ring corresponding to the wafer body.

[0007] Further arrangement: the negative pressure adsorption stage and the positive pressure leveling stage are associated to form a pressure compensation micro-control system in the laser focusing structure, the motion state in the non-automatic focusing action of the wafer body in the negative pressure adsorption stage is first acquired in the pressure compensation micro-control system, the flatness of the wafer body is judged according to the motion state, and if the low flatness motion state exists, the positive pressure leveling stage is entered.

[0008] Further arrangement: the wafer surface is divided into a plurality of sub-regions along the center point of the wafer body and according to an n*n separation mode, each sub-region is numbered as Xi, Yi according to a two-dimensional coordinate system, the length of each side of each sub-region is n, and the setting position of each positive pressure air port corresponds to a position directly below the sub-region.

[0009] Further arrangement: in the pressure compensation micro-control system, the SFQR value of the wafer body is acquired by the laser focusing structure, whether the wafer body is in a qualified state or a loss state is judged according to the SFQR value, the positive pressure leveling stage is entered in the loss state, the global positive pressure compensation action is preferentially performed in the positive pressure leveling stage, the calculation formula of the downforce of the wafer body is generated according to the SFQR value , and the obtained is converted into the gas volume Qp input by the positive pressure air port into the positive pressure chamber.

[0010] Further arrangement: in the global positive pressure compensation action, the actual gas volume input by the positive pressure air port into the positive pressure chamber is limited to (0.9~0.95)*Qp, and after the global positive pressure compensation action is completed, whether the wafer body is in a qualified state or a loss state is judged again, the single-region positive pressure compensation action is entered in the loss state, and the calculation formula of the downforce of a single point in the corresponding sub-region is generated according to the SFQR value: , θ is obtained by combining the SFQR value in each sub-region, the single-region positive pressure compensation action is preferentially performed on the sub-region with the largest θ in a descending adjustment mode, the obtained is converted into the gas volume input by the positive pressure air port into the positive pressure chamber, and the positive pressure air port corresponding to the sub-region is in a gas blowing state, and the positive pressure air ports in the remaining positions are in an idle state, until the entire wafer body is in a qualified state.

[0011] The present application has the following advantages: 1. The wafer surface calibration process is based on a conventional laser focusing structure, but abandons the conventional mechanical contact adjustment method. Specifically, gas is used as the "soft medium" in the calibration process. The wafer is fixed in a perforated rubber ring by negative pressure adsorption, and a positive pressure chamber is formed. When gas is continuously blown into the positive pressure chamber, the gas pressure is used to generate an upward support force on the lower side of the wafer. The purpose is to force the wafer to deform upward and offset the downward bending process caused by gravity. Compared with conventional calibration methods, it can significantly reduce mechanical damage to the wafer. 2. Based on the above content, the two methods of negative pressure adsorption and positive pressure blowing are combined into the laser focusing structure to form a pressure compensation micro-control system. In the positive pressure leveling stage, two positive pressure compensation actions are formed according to the single area and the global. One is to directly blow gas to drive the wafer slice to produce a large degree of deformation and reset. The other is to slowly increase the gas flow in a gradual manner in the single-area positive pressure compensation action. On the basis of correcting the flatness of the wafer slice, avoid the excessive amount of gas blown in, which may cause secondary upward bending damage to the wafer. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0013] Figure 1 This is a schematic structural diagram of a correction platform in a non-contact wafer flatness correction method proposed by the present invention; Figure 2 For the present invention Figure 2 A top view of Figure 3 For the present invention Figure 2 sectional view of Figure 4 This is a schematic diagram of the operation of a non-contact wafer flatness correction method proposed in the present invention.

[0014] In the figure: 1. Calibration platform; 2. Placement platform; 3. Negative pressure air port; 4. Pressure sensor component; 5. Positive pressure air port. DETAILED DESCRIPTION

[0015] The technical solutions of the present invention will be clearly and completely described below in conjunction with the embodiments. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0016] Example 1: Reference Figures 1-4 In this embodiment, a non-contact wafer flatness correction method uses a correction platform 1 and a laser focus structure, including a negative pressure adsorption stage and a positive pressure leveling stage. In both the negative pressure adsorption stage and the positive pressure leveling stage, the laser focus structure performs a non-autofocusing action. A placement platform 2 for placing the wafer body is provided on the calibration platform 1. The placement platform 2 forms a positive pressure chamber corresponding to the internal position of the calibration platform 1. A negative pressure air port 3 and a positive pressure air port 5 are provided in the placement platform 2 and the positive pressure chamber respectively. A pressure sensing component 4 for detecting the ambient pressure is provided in the positive pressure chamber. In the positive pressure leveling stage, the global positive pressure compensation action and the single-area positive pressure compensation action are subdivided, and in the positive pressure leveling stage, positive pressure air is introduced into the positive pressure chamber through the positive pressure air port 5, and the gas pressure provides an upward force on the wafer body, and a perforated sealing ring corresponding to the wafer body is set on the surface position of the placement platform 2.

[0017] Basic principle: The flatness of the wafer body is the key parameter that determines the quality of subsequent cutting, lithography and other operations. It is based on the calibration platform 1. Figure 1 For example, the outer diameter of the placement platform 2 matches the wafer body. This part is not shown in the present invention. The key reference is Figure 3 After the wafer body is placed on the placement platform 2, a negative pressure condition can be generated through the negative pressure air port 3. For this purpose, the present invention further requires the use of an air pump structure. On the one hand, the air pump structure can generate a negative pressure environment through the negative pressure air port 3, and on the other hand, it can also continuously blow air into the positive pressure chamber through the positive pressure air port 5; When the wafer body is fixed on the perforated sealing ring in a relatively fixed and closed manner through negative pressure adsorption, the interior of the positive pressure chamber becomes a relatively sealed space. Combined with the material properties of the wafer body itself and the influence of gravity, the problem of local deformation caused by the falling of the wafer body in a local position is caused. The key content of the present invention is: by continuously blowing gas into the positive pressure chamber, the gas pressure is used to provide an upward force from the bottom of the wafer body to push the wafer to bend upward and offset the deformation caused by gravity. This part is the basic content of the present invention.

[0018] Example 2: The key content of the present invention lies in the negative pressure adsorption stage and the positive pressure leveling stage. The basic operation process includes the following contents: The negative pressure adsorption stage and the positive pressure leveling stage are linked to the laser focusing structure to form a pressure compensation micro-control system. In the pressure compensation micro-control system, the action state of the wafer body in the non-autofocus action during the negative pressure adsorption stage is first obtained, and the flatness of the wafer body is judged according to the action state. If there is an action state of low flatness, the positive pressure leveling stage is entered.

[0019] Solution Description: It can be understood that the negative pressure adsorption stage belongs to the "fixing" stage of the wafer. To this end, it is first necessary to use a laser focusing structure to detect the flatness of the wafer body after it is fixed. The operation process of the laser focusing structure is briefly explained: After the laser beam is projected onto the wafer surface, the sensor calculates the focus offset in real time by analyzing the morphological changes of the reflected light spot (such as light spot offset, deformation, or abnormal intensity distribution). It also measures the height difference range (SFQR value) between the highest point and the lowest point of each small area (Site) on the wafer. The larger the SFQR value, the lower the flatness of the area. The action state proposed by the present invention can be represented by the SFQR value. The higher the SFQR value, the lower the flatness of the wafer body. This part will not be elaborated in the present invention. It essentially includes a laser generator and a machine vision analysis unit. During operation, the wafer body is first fixed on the perforated sealing ring by adsorption, and the SFQR value of the wafer body is obtained by the laser focusing structure. If the wafer body is in a qualified state according to the SFQR value, it is not necessary to enter the positive pressure leveling stage. On the contrary, if the wafer body is in a lost state according to the SFQR value, it enters the positive pressure leveling stage. In the positive pressure leveling stage, the essence is to continuously inject gas into the positive pressure chamber through the positive pressure air port, the purpose of which is to force the bending direction of the wafer body to change from bottom to top and offset the degree of gravity deformation, such as Figure 2 As shown, the negative pressure gas port 3 must be arranged in a circular array along the center point of the placement platform 2, and the center point of the wafer body and the center point of the placement platform 2 are on the same vertical axis, but the difference lies in the position limit of the positive pressure gas port 5; like Figure 2 As shown, multiple position restrictions are specifically implemented based on the surface area of ​​the wafer body. The purpose is that: because the detection process of the laser focus structure belongs to a single-point area, when the gas is injected through the positive pressure gas port 5, pneumatic operation is specifically performed based on the action position of the laser focus structure, thereby achieving overall area flatness control in a single-area independent control manner; Figure 1 It only shows a rough schematic diagram of the overall structure, but in actual situations, the positive pressure gas port 5 needs to be split according to the surface area of ​​the wafer body, such as Figure 2As shown, the whole wafer body is divided into several sub-regions along the center point of the wafer body and in a n*n separation mode, and the length of each side of each sub-region is n. After the wafer body is fixed, the setting position of each positive pressure air port 5 is just at the center point position of the sub-region.

[0020] Embodiment three: the following supplementary description is made for embodiment two: The positive pressure chamber is only a hollow structure. After the gas is continuously injected through the positive pressure air port 5, the gas will be filled in the positive pressure chamber in a "equal division" state. Relative to the closed positive pressure chamber, the gas pressure generated by the gas on the wafer body is directly related to the gas injection amount. Because of the "equal division" mode of the gas, the internal pressure of the whole positive pressure chamber is relatively consistent. Then, referring to the calculation method of F=P*S; Wherein P represents the environmental pressure in the positive pressure chamber, and S represents the pressure area of the wafer body, the lifting force generated by the wafer body on the gas is obtained, and further referring to the ideal gas equation P*V=n*R*T, the conversion method between the gas amount and P is indirectly obtained. This part is a common sense problem and will not be described in detail in the present application. The key lies in the global positive pressure compensation action and the single region positive pressure compensation action, and the following description is made: S1: in the global positive pressure compensation action, first, the calculation formula about the wafer body lifting force is roughly generated according to the above SFQR value: Wherein represents the wafer body plane deviation lifting force, represents the wafer body elastic modulus, represents the wafer thickness, represents the wafer plane deviation warping radius, represents the Poisson's ratio, represents the cross-sectional area of the wafer body relative to the positive pressure chamber, wherein , , and are relative constants, and wherein is obtained by the laser interferometer device, which is associated with the SFQR value. The conversion process will not be described in detail in the present application. It needs to be indicated that: the gas pressure input into the positive pressure chamber is roughly calculated according to the SFQR value, so as to calculate the gas amount input into the positive pressure chamber. The global positive pressure compensation action also includes the following contents: S1-1: To prevent excessive upward deformation of the wafer caused by excessive gas pressure generated by the input gas volume, the gas volume needs to be further limited during the global positive pressure compensation operation. If the roughly calculated gas volume is expressed as Qp, the actual gas volume input to the positive pressure chamber through the positive pressure port should be (0.9~0.95)*Qp; S2: After completing S1, it is necessary to perform non-autofocus action with the laser focus structure again to obtain the SFQR value and further judge the action status of the wafer body. Similarly, if it is in a qualified state, it is not necessary to enter the positive pressure leveling stage. Otherwise, it enters the single-area positive pressure compensation action. Refer to Figure 2 It can be understood as follows: the entire surface area is divided into four quadrants along the center point of the wafer body. Each sub-area can be numbered as (Xi, Yi) according to the two-dimensional coordinate system, and the SFQR value in each sub-area is obtained again through the laser focusing structure. The angle θ between the support point of the wafer body and the deformation zone in the sub-area is further obtained based on the SFQR value in the corresponding sub-area. The support point is represented by the center point of the wafer body, and the deformation zone is mainly represented by the center point of the corresponding sub-area. The single-point support force calculation formula is generated, which is expressed as: , among which Indicates the support force required in the sub-area. Expressed as the stiffness coefficient of the wafer body, Represents the target correction displacement in the sub-area, where is a constant, and θ and It can be roughly calculated by correlating the SFQR value with the laser interferometer. , but the specific operation process includes the following steps: S2-1: First, collect the SFQR values ​​in each sub-area and obtain θ. Then, the sub-area with the largest θ is adjusted from large to small, and the single-area positive pressure compensation action is performed first. When the single-area positive pressure compensation action is performed, only the positive pressure port 5 of the sub-area is inflated. According to the calculated The gas volume is controlled and only the positive pressure port at that location is used for blowing, while the positive pressure ports 5 at other locations are left idle. The purpose is to force the deformation of the wafer body to change in an instantaneous concentrated manner. However, due to the fluidity of the gas, the "increased" gas pressure will still be "evenly distributed" over the entire wafer body. S2-2: After completing S2-1, obtain the SFQR value of the wafer body again. If there is still a loss of quality, further correction is performed according to the contents described in S2 and S2-1 until the entire wafer body is in a qualified state.

[0021] In summary, the correction process for the wafer sheet provides a supporting force to the lower side of the wafer body by using gas as a "soft medium", the key purpose is to force the wafer sheet to deform upward by gas pressure to offset the downward deformation process caused by gravity, the specific process is to fix the wafer sheet by negative pressure adsorption, and then continuously blow gas into the positive pressure chamber by positive pressure blowing, the key role is to separate the global positive pressure compensation and single area positive pressure compensation when blowing gas, the pressure sensor is used to obtain the environmental pressure in the positive pressure chamber in real time, the gas volume is limited by simulating the environmental pressure, and the gas flow and blowing mode are limited by increasing, on the basis of correcting the flatness of the wafer sheet, secondary deformation damage is avoided.

[0022] The above is only an example and description of the structure of the present application, and those skilled in the art can make various modifications or supplements to the described specific embodiments or use similar ways to replace, as long as they do not deviate from the structure of the invention or exceed the scope defined by the present claims, which shall belong to the protection scope of the present application.

[0023] In the description of the present application, the description of the terms "one embodiment", "example", "specific example" and the like means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present application. In the present application, the illustrative description of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner.

[0024] The preferred embodiments of the present application disclosed above are only used to help explain the present application. The preferred embodiments do not describe all the details and limit the present application to the specific embodiments. Obviously, many modifications and changes can be made according to the content of the present application. The present application selects and describes these embodiments in order to better explain the principles and practical applications of the present application, so that those skilled in the art can well understand and utilize the present application. The present application is limited by the claims and their entire scope and equivalents.

Claims

1. A non-contact flatness correction method for a wafer, characterized in that: A correction platform (1) and a laser focus structure are used, including a negative pressure adsorption stage and a positive pressure leveling stage, and non-auto focus action is performed by the laser focus structure in both the negative pressure adsorption stage and the positive pressure leveling stage; The calibration platform (1) is provided with a placement platform (2) for placing the wafer body, the placement platform (2) forms a positive pressure chamber at an internal position corresponding to the calibration platform (1), and the placement platform (2) and the positive pressure chamber are respectively provided with a negative pressure air port (3) and a positive pressure air port (5), and the positive pressure chamber is provided with a pressure sensing component (4) for detecting the ambient pressure; In the positive pressure leveling stage, global positive pressure compensation action and single-area positive pressure compensation action are subdivided, and in the positive pressure leveling stage, positive pressure air is introduced into the positive pressure chamber through the positive pressure air port (5), so as to provide an upward force on the wafer body by the gas pressure.

2. The non-contact flatness correction method for a wafer according to claim 1, wherein: A sealing ring with holes corresponding to the wafer body is provided on the surface of the placement platform (2).

3. The non-contact flatness correction method for a wafer according to claim 1, wherein: The negative pressure adsorption stage and the positive pressure leveling stage are linked to the laser focusing structure to form a pressure compensation micro-control system. In the pressure compensation micro-control system, the action state of the wafer body in the non-autofocus action during the negative pressure adsorption stage is first obtained, and the flatness of the wafer body is judged according to the action state. If there is an action state of low flatness, the positive pressure leveling stage is entered.

4. The non-contact flatness correction method for a wafer according to claim 3, wherein: The wafer surface is divided into a plurality of sub-regions along the center point of the wafer body and in an n*n separation manner, and each sub-region is numbered as (Xi, Yi) according to a two-dimensional coordinate system, the side length of each sub-region is n, and the setting position of each positive pressure air port (5) corresponds to the position directly below the sub-region.

5. The non-contact flatness correction method for a wafer according to claim 1, wherein: In the pressure compensation micro-control system, the laser focusing structure is used to obtain the SFQR value of the wafer body. According to the SFQR value, it is judged whether the wafer body is in a qualified state or a failed state. In the failed state, it enters the positive pressure leveling stage, and the global positive pressure compensation action is performed first in the positive pressure leveling stage. The calculation formula of the wafer body support force is generated according to the SFQR value. , and according to the obtained Converted to the gas volume Qp inputted into the positive pressure chamber through the positive pressure port (5).

6. The non-contact flatness correction method for a wafer according to claim 5, wherein: In the global positive pressure compensation action, the actual gas volume of the positive pressure port (5) to the inside of the positive pressure chamber is limited to (0.9~0.95)*Qp, and when the global positive pressure compensation action is completed, it is judged again whether the wafer body is in a qualified state or a loss state. In the loss state, the single-area positive pressure compensation action is entered, and the calculation formula of the single-point downward force in the corresponding sub-area is generated according to the SFQR value: , combined with the SFQR value in each sub-region and obtain θ, the single-region positive pressure compensation action is performed on the sub-region with the largest θ in the adjustment mode from large to small, and according to the obtained The amount of gas inputted into the positive pressure chamber by the positive pressure gas port (5) is converted, and the positive pressure gas port (5) corresponding to the sub-area is limited to be in an inflation state, and the positive pressure gas ports (5) in other positions are in an idle state until the entire wafer body is in a qualified state.

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