Wafer non-contact flatness correction method
By combining non-contact negative pressure adsorption and positive pressure leveling with a laser focusing structure, the flatness of the wafer is corrected using gas pressure, which solves the damage problem caused by mechanical contact correction and achieves efficient and accurate wafer flatness correction.
Patent Information
- Application Number
- CN202511070518.7
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- Filing Date
- 2025-07-31
- Publication Date
- 2026-05-15
- Estimated Expiration
- 2045-07-31
AI Technical Summary
In existing technologies, mechanical contact wafer alignment methods can cause secondary damage to the wafer and are difficult to effectively correct the surface flatness of wafers with low thickness.
A non-contact wafer flatness correction method is adopted, which combines negative pressure adsorption and positive pressure leveling with a laser focusing structure. Gas pressure is used to provide upward support to the wafer, and positive pressure compensation is performed globally and in single areas to avoid deformation caused by mechanical contact.
It effectively corrects the flatness of wafers, reduces mechanical damage, avoids secondary deformation caused by excessive gas pressure, and improves correction accuracy and efficiency.
Smart Images
Figure CN120809650B_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of wafer calibration technology, and more specifically to a non-contact flatness correction method for wafers. Background Technology
[0002] In semiconductor manufacturing, wafer laser focusing technology is mainly used to solve the defocusing problem caused by surface undulations on wafers. Currently, it mainly uses a flying shooting method. The autofocus system uses 2X, 5X, and 10X objectives to meet the clear imaging requirements with a horizontal displacement speed of 200mm / s. The surface flatness of the test sample needs to be <12000μm. However, the thickness of wafer wafers is relatively low (thick wafers <200μm). Due to the material and shape of the wafers, when the surface flatness is >12000μm, autofocus is not possible.
[0003] Regarding wafer calibration methods, please refer to the relevant content in publication numbers CN116454001A and CN104718607A. Conventional methods mostly use mechanical contact adjustment, which essentially involves picking up the wafer and then readjusting its structural position. However, due to the special material of wafers, the contact gripping action can cause secondary scratch damage to the wafer. Furthermore, due to the structural and dimensional characteristics of the wafer itself, direct contact adjustment will exacerbate the degree of wafer deformation. This invention proposes a solution to this problem. Summary of the Invention
[0004] The purpose of this invention is to provide a non-contact flatness correction method for wafers. Due to the material properties and structural dimensions of the wafers themselves, mechanical contact adjustment structures can cause secondary damage to the wafers during the wafer flatness correction process.
[0005] The objective of this invention can be achieved through the following technical solution: a non-contact flatness correction method for wafers, which uses a correction platform and a laser focusing structure, including a negative pressure adsorption stage and a positive pressure leveling stage, wherein non-automatic focusing is performed by the laser focusing structure in both the negative pressure adsorption stage and the positive pressure leveling stage.
[0006] The calibration platform is provided with a placement platform for placing the wafer body. The placement platform forms a positive pressure chamber corresponding to the internal position of the calibration platform. Negative pressure air port and positive pressure air port are respectively provided in the placement platform and the positive pressure chamber. A pressure sensing component for detecting ambient pressure is provided in the positive pressure chamber.
[0007] The positive pressure leveling stage is further divided into global positive pressure compensation action and single-area positive pressure compensation action. In the positive pressure leveling stage, positive pressure air is introduced into the positive pressure chamber through the positive pressure air port to provide upward support to the wafer body with gas pressure.
[0008] A further setting is made: a perforated sealing ring is placed on the surface of the platform to correspond to the wafer body.
[0009] Further configuration: The negative pressure adsorption stage and the positive pressure leveling stage are associated with 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. The flatness of the wafer body is judged based on the action state. If there is a low flatness action state, the positive pressure leveling stage is entered.
[0010] Further configuration: the wafer surface is divided into multiple sub-regions along the center point of the wafer body and in an n*n partitioning manner, and each sub-region is numbered as Xi and Yi according to the two-dimensional coordinate system, the side length of each sub-region is n, and the position of each positive pressure gas port corresponds to the position directly below the sub-region.
[0011] Further configuration: In the pressure compensation microcontroller system, the SFQR value of the wafer body is obtained using a laser focusing structure. Based on the SFQR value, it is determined whether the wafer body is in a qualified state or a deformed state. In the deformed state, it enters the positive pressure leveling stage, and in the positive pressure leveling stage, global positive pressure compensation is prioritized. The calculation formula for the wafer body's downward support force is generated based on the SFQR value. and based on the obtained This is converted to the amount of gas Qp input from the positive pressure port into the positive pressure chamber.
[0012] Further settings include: during the global positive pressure compensation operation, the actual gas flow rate from the positive pressure port to the positive pressure chamber is limited to (0.9~0.95)*Qp. Furthermore, after completing the global positive pressure compensation operation, the wafer body is again assessed for either a qualified state or a lossy state. If a lossy state exists, the operation proceeds to a single-region positive pressure compensation operation, and a calculation formula for the single-point downward force in the corresponding sub-region is generated based on the SFQR value. Combining the SFQR value of each sub-region with θ, and prioritizing the sub-region with the largest θ for single-region positive pressure compensation in an adjustment manner from largest to smallest, based on the obtained... The amount of gas input from the positive pressure port into the positive pressure chamber is calculated, and the positive pressure port corresponding to the sub-region is restricted to a venting state, while the positive pressure ports in other positions are idle, until the entire wafer body is in a qualified state.
[0013] The present invention has the following beneficial effects:
[0014] 1. The calibration process for wafer surfaces is based on conventional laser focusing structures, but abandons conventional mechanical contact adjustment methods. Specifically, gas is used as a "soft medium" in the calibration process. This is manifested as follows: the wafer is fixed in a perforated rubber ring by negative pressure adsorption to form a positive pressure chamber. When gas is continuously pumped into the positive pressure chamber, the gas pressure generates an upward downward force on the lower side of the wafer. The purpose is to force the wafer to deform upward and counteract the downward bending deformation caused by gravity. Compared with conventional calibration methods, this can significantly reduce mechanical damage to the wafer.
[0015] 2. Based on the above, the negative pressure adsorption and positive pressure blowing methods 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 single area and global. The first is to directly blow in gas to drive the wafer to undergo a large deformation and reset. The second is to gradually increase the gas flow in the single area positive pressure compensation action. On the basis of correcting the flatness of the wafer, the amount of gas blown in should be avoided to prevent the wafer from undergoing secondary upward bending deformation damage due to excessive gas volume. Attached Figure Description
[0016] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.
[0017] Figure 1 This is a schematic diagram of the structure of the calibration platform in the non-contact flatness calibration method for wafers proposed in this invention;
[0018] Figure 2 In this invention Figure 2 Top view;
[0019] Figure 3 In this invention Figure 2 A sectional view;
[0020] Figure 4 This is a schematic diagram illustrating the operation of a non-contact flatness correction method for wafers proposed in this invention.
[0021] In the diagram: 1. Calibration platform; 2. Placement platform; 3. Negative pressure port; 4. Pressure sensing component; 5. Positive pressure port. Detailed Implementation
[0022] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.
[0023] Example 1: Refer to Figures 1-4 The non-contact flatness correction method for wafers in this embodiment uses a correction platform 1 and a laser focusing 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 focusing structure performs non-automatic focusing.
[0024] 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 corresponding to the internal position of the calibration platform 1. 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. The positive pressure chamber is provided with a pressure sensing component 4 for detecting the ambient pressure.
[0025] The positive pressure leveling stage is further divided into global positive pressure compensation action and single-area positive pressure compensation action. In the positive pressure leveling stage, positive pressure air is introduced into the positive pressure chamber through positive pressure air port 5 to provide upward support to the wafer body with gas pressure. A perforated sealing ring is set on the surface of the platform 2 corresponding to the wafer body.
[0026] Basic principle: The flatness of the wafer body is a key parameter determining the quality of subsequent processes such as dicing and photolithography. Specifically, it is based on calibration platform 1, with... Figure 1 For example, the outer diameter of the placement platform 2 matches the wafer body; this part is not shown in this invention, but is referred to in the key reference. Figure 3 After the wafer body is placed on the placement platform 2, negative pressure conditions can be generated through the negative pressure air port 3. In this invention, an air pump structure is also needed. The air pump structure can generate a negative pressure environment through the negative pressure air port 3, and can also continuously blow air into the positive pressure chamber through the positive pressure air port 5.
[0027] When a wafer is fixed to a perforated sealing ring in a relatively fixed and sealed manner using negative pressure adsorption, the inside of the positive pressure chamber becomes a relatively sealed space. Combined with the material properties of the wafer itself and the influence of gravity, this causes localized deformation due to the wafer sagging in certain areas. The key content of this invention is to continuously blow gas into the positive pressure chamber, using the gas pressure to provide an upward lifting force from the bottom of the wafer, which pushes the wafer upward to counteract gravitational deformation. This part is the basic content of this invention.
[0028] Example 2: The key aspects of this invention lie in the negative pressure adsorption stage and the positive pressure leveling stage. The basic operating process includes the following:
[0029] 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 during the non-autofocus action in the negative pressure adsorption stage is first obtained. The flatness of the wafer body is judged based on the action state. If there is a low flatness action state, the positive pressure leveling stage is entered.
[0030] Solution Description: The negative pressure adsorption stage can be understood as part of the wafer "fixation" stage. Therefore, a laser focusing structure is first needed to detect the flatness of the wafer after it has been fixed. A brief explanation of the laser focusing structure's operation is as follows:
[0031] After the laser beam is projected onto the wafer surface, the sensor analyzes the changes in the shape of the reflected light spot (such as spot shift, deformation, or abnormal intensity distribution) and calculates the focal offset in real time. It also measures the height difference range (SFQR value) between the highest and lowest points of each small area (Site) on the wafer. The larger the SFQR value, the lower the flatness of the area. The action state proposed in this 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 on in this invention. Essentially, it includes a laser generator and a mechanical vision analysis unit.
[0032] During operation, the wafer body is first fixed to the perforated sealing ring by adsorption, and then the SFQR value of the wafer body is obtained by 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. Otherwise, if the wafer body is in a lossy state according to the SFQR value, it enters the positive pressure leveling stage.
[0033] During the positive pressure leveling stage, the essence is to continuously inject gas into the positive pressure chamber through the positive pressure vent. The purpose is to forcibly change the bending direction of the wafer body from bottom to top to counteract the degree of gravitational deformation. Figure 2 As shown, the negative pressure gas ports 3 must be arranged in a circular array along the center point of the placement platform 2, while the center point of the wafer body and the center point of the placement platform 2 are on the same vertical axis. However, the difference lies in the position limitation of the positive pressure gas ports 5.
[0034] like Figure 2 As shown, the specific method is to restrict multiple positions based on the surface area of the wafer body. The purpose is that, since the detection process of the laser focusing structure is a single-point area, when gas is injected through the positive pressure port 5, the pneumatic movement is based on the action position of the laser focusing structure. This is a method of controlling the overall area flatness in a single-area independent control manner.
[0035] Figure 1 This is merely a rough schematic diagram of the overall structure. In reality, the positive pressure vent 5 needs to be divided according to the surface area of the wafer body, such as... Figure 2 As shown, the entire wafer body is divided into several sub-regions along the center point of the wafer body and in an n*n partitioning manner. Each sub-region has a side length of n. After the wafer body is fixed, the setting position of each positive pressure port 5 corresponds exactly to the center point of the sub-region.
[0036] Example 3: The following supplementary explanation is provided for Example 2:
[0037] The positive pressure chamber is a hollow structure. After gas is continuously injected through the positive pressure port 5, the gas will fill the positive pressure chamber in an "evenly distributed" state. Compared with the closed positive pressure chamber, the gas pressure generated by the gas on the wafer body is directly related to the amount of gas injected. And because of the "even distribution" of the gas, the overall pressure inside the positive pressure chamber is relatively uniform. Therefore, refer to the calculation method of F=P*S.
[0038] Where P represents the ambient pressure inside the positive pressure chamber, and S represents the pressure-bearing area of the wafer body, the upward force generated by the gas on the wafer body is obtained, and further, referring to the ideal gas equation P*V=n*R*T, the conversion method between gas volume and P is indirectly obtained. This part is a common knowledge issue and will not be explained in detail in this invention.
[0039] The key lies in the detailed distinction between global positive pressure compensation and single-region positive pressure compensation, which are explained below:
[0040] S1: In the global positive pressure compensation operation, the calculation formula for the wafer body under-support force is first roughly generated based on the above SFQR value: , among them This indicates the downward force that should be provided after the wafer body experiences flatness deviation. Expressed as the bulk elastic modulus of the wafer, Expressed as wafer thickness, The radius of warpage indicates the flatness deviation of the wafer. Indicates Poisson's ratio, This represents the cross-sectional area of the wafer body relative to the positive pressure chamber, where... , , and It is a relative constant, and among them... Specifically, this is obtained through a laser interferometer, and is related to the SFQR value. The conversion process will not be detailed in this invention. What needs to be stated is that the gas pressure input into the positive pressure chamber is roughly calculated based on the SFQR value, thereby calculating the gas volume input into the positive pressure chamber. The global positive pressure compensation action also includes the following:
[0041] S1-1: To avoid excessive upward deformation of the wafer due to excessive gas pressure caused by the input gas volume, the gas volume needs to be further limited in the global positive pressure compensation operation. If the roughly calculated gas volume is represented as Qp, the actual gas volume input to the positive pressure chamber through the positive pressure port should be (0.9~0.95)*Qp.
[0042] S2: After completing part S1, it is necessary to perform non-autofocus again using the laser focusing structure to obtain the SFQR value and further determine the operating 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 operation, as described above. Figure 2 This can be understood as follows: The overall surface area is divided into four quadrants along the center point of the wafer body. Each sub-region is numbered (Xi, Yi) using a two-dimensional coordinate system. The SFQR value of each sub-region is then obtained through a laser focusing structure. Furthermore, the angle θ between the wafer body support point and the deformation zone in that sub-region is obtained based on the SFQR value. The support point represents the center point of the wafer body, while the deformation zone mainly represents the center point of the corresponding sub-region. A formula for calculating the single-point downward force is then generated, expressed as: , among them Indicates the required support force in the sub-region. Expressed as the stiffness coefficient of the wafer body, This represents the target correction displacement in the sub-region, where... For a constant value, while θ and This can be roughly calculated by correlating the SFQR value with the laser interferometer. However, the specific operation process includes the following steps:
[0043] S2-1: First, collect the SFQR values in each sub-region and obtain θ. Following an adjustment method from largest to smallest, prioritize performing single-region positive pressure compensation on the sub-region with the largest θ. During single-region positive pressure compensation, only the positive pressure port 5 of that sub-region is vented, based on the calculated... The gas volume is controlled and only the positive pressure port at this position is used for blowing, while the positive pressure ports 5 at other positions are idle. The purpose is to forcibly change the degree of deformation of the wafer body in an "instantaneous concentration" manner. However, due to the fluidity of the gas, the "increased" gas pressure will still be "evenly distributed" to the entire wafer body.
[0044] S2-2: After completing S2-1, obtain the SFQR value of the wafer body again. If the vector state still exists, further correction is performed according to the contents introduced in S2 and S2-1 until the overall wafer body is in a qualified state.
[0045] In summary, the wafer calibration process uses gas as a "soft medium" to provide downward support to the underside of the wafer. The key purpose is to use gas pressure to force the wafer to deform upwards, thus counteracting the downward bending deformation caused by gravity. Specifically, the wafer is fixed by negative pressure adsorption, and then gas is continuously pumped into the positive pressure chamber by positive pressure blowing. The key function is to separate the gas injection into two actions: global positive pressure compensation and single-area positive pressure compensation. Pressure sensors are used to obtain the ambient pressure inside the positive pressure chamber in real time. The amount of gas injected is limited by simulating the ambient pressure, and the gas flow and blowing method are limited by gradually increasing the gas flow. This avoids secondary deformation damage while calibrating the flatness of the wafer.
[0046] The above description is merely an example and illustration of the structure of the present invention. Those skilled in the art can make various modifications or additions to the specific embodiments described, or use similar methods to replace them, as long as they do not deviate from the structure of the invention or exceed the scope defined in the claims, all of which should fall within the protection scope of the present invention.
[0047] In the description of this specification, references to terms such as "an embodiment," "example," "specific example," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.
[0048] The preferred embodiments of the present invention disclosed above are merely illustrative of the invention. These preferred embodiments do not exhaustively describe all details, nor do they limit the invention to specific implementations. Clearly, many modifications and variations can be made based on the content of this specification. This specification selects and specifically describes these embodiments to better explain the principles and practical applications of the invention, thereby enabling those skilled in the art to better understand and utilize the invention. The invention is limited only by the claims and their full scope and equivalents.
Claims
1. A non-contact flatness correction method for wafers, characterized in that, Using a calibration platform (1) and a laser focusing structure, including a negative pressure adsorption stage and a positive pressure leveling stage, non-automatic focusing is performed through the laser focusing 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 corresponding to the internal position of the calibration platform (1). 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). The positive pressure chamber is provided with a pressure sensing component (4) for detecting the ambient pressure. 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, positive pressure air is introduced into the positive pressure chamber through the positive pressure air port (5) to provide upward support to the wafer body with gas pressure. 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. The flatness of the wafer body is judged based on the action state. If there is a low flatness action state, it enters the positive pressure leveling stage. In the pressure compensation microcontroller system, the SFQR value of the wafer body is obtained using a laser focusing structure. Based on the SFQR value, the wafer body is determined to be in a qualified state or a deformed state. In the deformed state, it enters the positive pressure leveling stage, and in the positive pressure leveling stage, global positive pressure compensation is prioritized. The formula for calculating the under-support force of the wafer body is generated based on the SFQR value. , This indicates the downward force that should be provided after the wafer body experiences flatness deviation. Expressed as the bulk elastic modulus of the wafer, Expressed as wafer thickness, The radius of warpage indicates the flatness deviation of the wafer. Indicates Poisson's ratio, This represents the cross-sectional area of the wafer body relative to the positive pressure chamber, where... , , and It is a relative constant, and based on the obtained Converted to the amount of gas Qp input into the positive pressure chamber from the positive pressure port (5); In the global positive pressure compensation action, the actual gas volume of the positive pressure port (5) into the positive pressure chamber is expressed as (0.9~0.95)*Qp. In the process of completing the global positive pressure compensation action, the wafer body is judged again to be in a qualified state or a lossy state. If there is a lossy state, it enters the single-region positive pressure compensation action, and the calculation formula of the single-point downward force in the corresponding sub-region is generated according to the SFQR value: , Indicates the required support force in the sub-region. Expressed as the stiffness coefficient of the wafer body, This represents the target correction displacement in the sub-region. Combined with the SFQR value of each sub-region, θ is obtained. Following an adjustment method from largest to smallest, single-region positive pressure compensation is preferentially applied to the sub-region with the largest θ. Based on the obtained... The amount of gas input into the positive pressure chamber by the positive pressure port (5) is calculated, and the positive pressure port (5) corresponding to the sub-region is restricted to be in the blotting state, while the positive pressure ports (5) in other positions are in the idle state. The SFQR value of the wafer body is obtained again. If there is still a loss state, the above global positive pressure compensation action is repeated until the entire wafer body is in a qualified state.
2. The non-contact flatness correction method for wafers according to claim 1, characterized in that, The surface of the placement platform (2) is provided with a perforated sealing ring corresponding to the wafer body.
3. The non-contact flatness correction method for wafers according to claim 1, characterized in that, The wafer surface is divided into multiple sub-regions along the center point of the wafer body and in an n*n partitioning manner. Each sub-region is numbered (Xi, Yi) according to the two-dimensional coordinate system. The side length of each sub-region is n. The position of each positive pressure gas port (5) is located directly below the sub-region.