Wafer placement device and wafer placement method
By designing inclined support, the wafer placement box is placed inclined and gravity is used to achieve equally spaced display, which solves the problems of inefficient efficiency and insufficient accuracy during wafer placement, and improves production efficiency and processing quality.
Patent Information
- Application Number
- CN202510171913.8
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-02-17
- Publication Date
- 2025-07-04
AI Technical Summary
In the prior art, wafers need to be manually adjusted during placement to maintain consistent spacing, resulting in low efficiency and insufficient accuracy, affecting the accuracy and consistency of subsequent processing.
Design a wafer placement device, use inclined support members to place the wafer placement box inclined, and use gravity to achieve equally spaced display, reducing the need for manual adjustment.
The wafer placement efficiency and accuracy are improved, the accuracy and consistency of subsequent processing are ensured, the risk of damage caused by scratches, collisions and other damages are reduced, and the production efficiency and process flow are optimized.
Smart Images
Figure CN120261334A_ABST
Abstract
Description
Technical Field
[0001] This application relates to the technical field of semiconductor equipment, and particularly to a wafer placement device and a placement method. Background Art
[0002] During the semiconductor manufacturing process, wafers need to be transferred between different processes and different areas within the same process. Wafer placement cassettes are required for both the transportation and storage of wafers. To improve the utilization rate of wafer placement cassettes, multiple wafers are usually stored in one wafer placement cassette.
[0003] Currently, when performing operations such as collecting Wafer ID and film separation on wafers, the wafer placement cassette is mostly placed on a workbench. Then, manual labor is relied upon to pick up the wafers manually, turn and transfer them, and then place them back into the wafer placement cassette.
[0004] However, in the process of transferring and placing the wafers back into the wafer placement cassette, the positions of the wafers need to be adjusted manually to ensure that the spacing between the wafers is consistent. This results in a relatively long time consumed during the placement process and low efficiency. Moreover, traditional manual adjustment methods often cannot provide sufficient placement accuracy, leading to inaccuracies in the positions of the wafers and affecting the accuracy and consistency of subsequent processing. Summary of the Invention
[0005] Based on this, it is necessary to provide a wafer placement device and a placement method to address the above problems of low placement accuracy and efficiency.
[0006] According to one aspect of the present application, a wafer placement device is provided, including:
[0007] A placement platform, including a placement rack and a support member. The support member is disposed on the mounting surface of the placement rack. The support member has a support surface for supporting the wafer placement cassette. The support surface faces away from the mounting surface and is an inclined surface.
[0008] In one embodiment, the wafer placement device further includes a shielding assembly. The shielding assembly is disposed on the placement platform and cooperates to enclose a protection area. The support surface is located within the protection area.
[0009] In one embodiment, the support member has an upper surface facing away from the placement rack. The area of the support surface is equal to the area of the bottom surface of the wafer placement cassette. The upper surface includes the support surface. The area of the upper surface is greater than or equal to the area of the support surface and less than or equal to twice the area of the support surface.
[0010] In one embodiment, the angle between the support surface and the mounting surface is greater than 4° and less than 6°.
[0011] In one embodiment, there are at least two of the support members, and at least two of the support members are arranged on the placement rack along the length direction of the placement rack.
[0012] In one embodiment, the cross-section of the support member along the length direction of the placement rack is a square surface, the cross-section of the support member along the width direction of the placement rack is a triangular surface, and the cross-section of the support member along the height direction of the placement rack is a triangular surface.
[0013] In one embodiment, the support member and the placement rack are of an integrally formed structure.
[0014] In one embodiment, the placement rack includes a placement plate, and the support member is arranged on the placement plate.
[0015] In one embodiment, the placement rack further includes an adjustment rack body, and the adjustment rack body is arranged on the placement plate and can adjust the angle between the placement plate and the geoid.
[0016] According to another aspect of the present application, there is provided a wafer placement method for the placement device described in any one of the above embodiments, including:
[0017] Adjust the angle of the placement platform so that the placement plate of the placement platform is parallel to the geoid;
[0018] Place the wafer placement box on the support surface of the support member, so that each wafer in the wafer placement box can tilt to the same side under the action of gravity for equidistant arrangement.
[0019] In the above-mentioned wafer placement device and placement method, by making the support surface of the placement platform for supporting the wafer placement box be an inclined surface, after the wafer placement box is placed on the support surface of the placement platform, each wafer in the wafer placement box can tilt to the same side under the action of gravity, and then equidistant arrangement is carried out. There is no need for staff to manually adjust the positions of the wafers to keep the distances between the wafers consistent, effectively shortening the placement time of the wafers, improving the placement efficiency and placement accuracy of the wafers, and effectively ensuring the accuracy and consistency of subsequent processing. Description of the Drawings
[0020] Figure 1 It is a schematic structural diagram of a wafer placement device according to some embodiments of the present application.
[0021] Figure 2 It is a schematic structural diagram of a wafer placement device according to some embodiments of the present application from another perspective.
[0022] Figure 3 It is a schematic structural diagram of a wafer placement device according to some embodiments of the present application from yet another perspective.
[0023] Figure 4 Flow schematic diagram of the wafer placement method for some embodiments of the present application.
[0024] Reference numerals:
[0025] 1. Placement platform;
[0026] 11. Placement rack; 111. Placement plate; 112. Adjusting rack body;
[0027] 12. Support member; 121. Support surface; 122. Upper surface;
[0028] 2. Shielding assembly. Detailed implementation manners
[0029] To make the above objects, features, and advantages of the present application more obvious and understandable, the following will describe the detailed implementation manners of the present application with reference to the accompanying drawings. Many specific details are set forth in the following description to fully understand the present application. However, the present application can be implemented in many other ways different from those described herein, and those skilled in the art can make similar improvements without departing from the connotation of the present application. Therefore, the present application is not limited by the specific embodiments disclosed below.
[0030] In the description of the present application, it should be understood that if there appear these terms "center", "longitudinal", "transverse", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", "axial", "radial", "circumferential", etc., the orientation or positional relationship indicated by these terms is based on the orientation or positional relationship shown in the drawings, and is only for the convenience of describing the present application and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the present application.
[0031] In addition, if there appear these terms "first", "second", these terms are only used for descriptive purposes and cannot be understood as indicating or implying relative importance or implicitly specifying the quantity of the indicated technical features. Thus, the features defined with "first", "second" may explicitly or implicitly include at least one of such features. In the description of the present application, if there appears the term "plural", the meaning of "plural" is at least two, such as two, three, etc., unless otherwise specifically defined.
[0032] In this application, unless otherwise clearly specified or limited, if terms such as "installed", "connected", "linked", "fixed", etc. appear, these terms shall be understood in a broad sense. For example, it may be a fixed connection, a detachable connection, or integrated; it may be a mechanical connection or an electrical connection; it may be directly connected or indirectly connected through an intermediate medium, and it may be the communication inside two components or the interaction relationship between two components, unless otherwise clearly limited. For those of ordinary skill in the art, the specific meanings of the above terms in this application can be understood according to specific circumstances.
[0033] In this application, unless otherwise clearly specified or limited, if there is a description such as the first feature being "on" or "under" the second feature, its meaning may be that the first and second features are in direct contact, or the first and second features are indirectly in contact through an intermediate medium. Moreover, the first feature being "above", "over" and "on top of" the second feature may mean that the first feature is directly above or obliquely above the second feature, or simply indicates that the first feature is at a higher horizontal level than the second feature. The first feature being "under", "beneath" and "underneath" the second feature may be that the first feature is directly below or obliquely below the second feature, or simply indicates that the first feature is at a lower horizontal level than the second feature.
[0034] It should be noted that if an element is referred to as "fixed to" or "disposed on" another element, it may be directly on the other element or there may also be an intermediate element. If an element is considered to be "connected" to another element, it may be directly connected to the other element or there may be an intermediate element at the same time. If so, the terms "vertical", "horizontal", "up", "down", "left", "right" and similar expressions used in this application are only for the purpose of illustration and do not represent the only implementation manner.
[0035] The use of the wafer placement box can provide a relatively high cleanliness environment for the wafer, avoiding the contamination of the wafer by the pollution sources in the manufacturing environment with a cleanliness lower than that of the wafer placement box. In order to improve the utilization rate of the wafer placement box, usually multiple wafers are stored in a wafer placement box. That is, a plurality of card slots are provided in the wafer placement box, and the card slots divide and support the wafers, so that the bottom of the wafers is suspended and the wafers are placed in an orderly manner in the wafer placement device. In order to prevent the wafers from being damaged due to shaking in the card slots, a plurality of fixing slots with the same thickness as the wafers are provided on the lid of the wafer placement box. In order to enable each wafer to be inserted into the corresponding fixing slot respectively, it is necessary to manually adjust the wafers so that the distance between the wafers is kept consistent, which directly leads to the problems of long time consumption, inaccurate adjustment and low efficiency during the placement process of the wafers.
[0036] In addition, when collecting WaferID information and performing operations such as film separation and classification during the production process of wafers, operators need to frequently load and unload wafers manually from the cassette. The wafers should be placed in the cassette with the same orientation and front-back side requirements, and at the same time, the relative positions of the wafers should be kept consistent. Currently, the method for collecting Wafer ID and performing film separation operations is to place the cassette on a horizontal workbench and rely on manual handling to pick up the wafers and then transfer and place them in the cassette after flipping. However, in the last step of transferring and placing the wafers back into the cassette, to avoid damaging the wafers due to problems such as scraping, collision, and skew insertion, manual adjustment of the wafers is required to keep the spacing between the wafers consistent, which directly leads to the problems of long time consumption, inaccurate adjustment, and low efficiency during the placement process of the wafers.
[0037] That is, traditional manual adjustment methods often cannot provide sufficient placement accuracy, resulting in inaccuracies in the positions of the wafers, which affects the accuracy and consistency of subsequent processing. Moreover, the existing technology relying on manual adjustment has the problem of low adjustment efficiency, increasing the waiting time on the production line and affecting production efficiency.
[0038] In summary, the present application provides a wafer placement device, which enables the wafer cassette to be in an inclined state after being placed on it, and the wafers in the wafer cassette can tilt to one side due to gravity, realizing an equidistant arrangement of the wafers, effectively solving the problems existing in placement accuracy, operation convenience, and wafer protection, thereby improving production efficiency and wafer processing quality. At the same time, it improves operation convenience and reduces the risk of damage to the wafers due to scraping, collision, skew insertion, etc.
[0039] Specifically, reference can be made to Figures 1 - 3 In an embodiment of the present application, a wafer placement device is provided, including a placement platform 1 having a placement rack 11 and a support member 12. Among them, the placement rack 11 can be placed on a bearing surface (such as the ground, a tabletop, or the surface of other support bodies) for use. The placement rack 11 has an installation surface facing away from the bearing surface, and the support member 12 is disposed on the installation surface of the placement rack 11 so that the support member 12 can support the wafer cassette.
[0040] Specifically, the support member 12 has a support surface 121 for supporting the wafer cassette. The support surface 121 faces away from the installation surface, and the support surface 121 is an inclined surface. It can be understood that the support surface 121 is an inclined surface inclined with respect to the geoid.
[0041] Among them, the geoid is a level surface that coincides with the mean sea level and extends into the interior of the continent. It is a special level surface that coincides with the mean sea level and extends into the interior of the continent. It is an important reference surface of the earth's gravity field, used to describe the shape of the earth and the inhomogeneity of the gravity field, and is also the reference surface of orthometric height. The geoid is a global and unique reference surface that reflects the true shape of the earth (i.e., the "physical surface" of the earth) and takes into account the inhomogeneity of the mass distribution inside the earth. In surveying work, the geoid is used as the basis.
[0042] By making the support surface 121 an inclined plane inclined to the geoid, when the wafer placement box is placed on the support surface 121 of the support member 12, each wafer in the wafer placement box can be inclined to the same side under the action of gravity, and then be arranged at equal intervals, without the need for workers to manually adjust the positions of the wafers to keep the intervals between the wafers consistent, effectively shortening the placement time of the wafers, improving the placement efficiency and placement accuracy of the wafers, and effectively ensuring the accuracy and consistency of subsequent processing.
[0043] In summary, when the wafer placement device of the present application is in use, the placement rack 11 can be first placed on a bearing surface (such as the ground, a tabletop, or the surface of other support bodies), and then the wafer placement box is placed on the support surface 121 of the support member 12, so that the bottom surface of the wafer placement box is inclined to the geoid, and each wafer in the wafer placement box can be inclined to the same side under the action of gravity to be arranged at equal intervals. That is, the wafer placement device makes the support surface 121 for supporting the wafer placement box on the placement platform 1 an inclined plane, so that after the wafer placement box is placed on the support surface 121 of the placement platform 1, each wafer in the wafer placement box can be inclined to the same side under the action of gravity, and then be arranged at equal intervals, without the need for workers to manually adjust the positions of the wafers to keep the intervals between the wafers consistent, effectively shortening the placement time of the wafers, improving the placement efficiency and placement accuracy of the wafers, and effectively ensuring the accuracy and consistency of subsequent processing.
[0044] In one of the embodiments, the wafer placement device further includes a shielding assembly 2. The shielding assembly 2 is disposed on the placement platform 1 and cooperates to enclose a protection area, and the support surface 121 is located in the protection area, so that the wafer placement box on the support surface 121 is not easily dropped from the placement platform 1.
[0045] Specifically, in one embodiment, the shielding assembly 2 includes four columns and a shielding ring. The four columns are respectively located at the left front corner, left rear corner, right front corner, and right rear corner of the placement rack 11, and are connected to the placement rack 11 or the support member 12. The shielding ring is sleeved on the four columns, and a protection area is formed inside the shielding ring. After the wafer placement box is placed on the support member 12, it can be located inside the shielding ring, so as to reduce the probability of falling from the placement platform 1 through the shielding of the shielding ring. In addition, to further improve the shielding effect of the shielding ring on the wafer placement box, there are multiple shielding rings, and the multiple shielding rings are uniformly arranged along the height direction of the columns. Among them, the height direction of the columns is perpendicular to the geoid.
[0046] In another embodiment (not shown), the shielding assembly 2 includes four shielding frames. The four shielding frames are respectively located on the left side, right side, front side, and rear side of the placement rack 11, and are connected to the placement rack 11 or the support member 12. The extension lines of the four shielding frames are connected in pairs and cooperate to enclose a protection area. After the wafer placement box is placed on the support member 12, it can be located between the four shielding frames, so as to reduce the probability of falling from the placement platform 1 through the shielding of the shielding frames. Among them, the shielding frame can be a plate-like structure or a mesh structure.
[0047] In one of the embodiments, the support member 12 has an upper surface 122 facing away from the placement rack 11. The upper surface 122 includes a support surface 121. The area of the support surface 121 is equal to the area of the bottom surface of the wafer placement box. The area of the upper surface 122 is greater than or equal to the area of the support surface 121 and less than or equal to twice the area of the support surface 121, so as to ensure the support effect of the support member 12 on the wafer placement box.
[0048] Specifically, the area ratio range between the upper surface 122 and the support surface 121 is 1 - 1.5. More specifically, the area ratio range between the upper surface 122 and the support surface 121 is 1 - 1.25. This range can not only ensure the effective support of the support member 12 on the wafer placement box, but also make the wafer placement box have not too much moving space on the support member 12, thereby ensuring the placement stability of the wafer placement box on the support member 12.
[0049] In addition, when the area ratio between the upper surface 122 and the support surface 121 is greater than 1, it can also provide space for the setting of the shielding assembly 2. That is, when the area ratio between the upper surface 122 and the support surface 121 is greater than 1, the shielding assembly 2 can be arranged on the upper surface 122 of the support member 12, so that the shielding assembly 2 can effectively shield the wafer placement box on the support member 12 and reduce the probability of the wafer placement box falling from the placement platform 1.
[0050] Further, in order to improve the placement stability of the wafer placement box on the support member 12, in one embodiment, an anti-slip structure may be provided on the support surface 121. By means of the anti-slip structure, the friction force is increased to prevent the wafer placement box from sliding on the support surface 121. Among them, the anti-slip structure can be made of rubber, silica gel, soft plastic or fiber fabric, and has a grid-like or textured surface with minute protrusions. Due to the softness of the anti-slip structure, the impact of the wafer placement box on the support member 12 and the placement rack 11 when placed on the support surface 121 can also be reduced, and the service life of the placement platform 1 can be extended.
[0051] In one embodiment, the angle between the support surface 121 and the mounting surface is greater than 4° and less than 6°. Specifically, the angle between the support surface 121 and the mounting surface is 5°. It can be understood that the larger the angle between the support surface 121 and the mounting surface, the worse the stability of the wafer placement box on the support surface 121; the smaller the angle between the support surface 121 and the mounting surface, the less likely the wafers in the wafer placement box are to tilt to the same side under the action of gravity. Therefore, through testing in this application, it is determined that when the angle between the support surface 121 and the mounting surface is greater than 4° and less than 6°, and the angle between the support surface 121 and the mounting surface is 5°, the wafer placement box can have high placement stability on the support surface 121, and the wafers in the wafer placement box are also likely to tilt to the same side under the action of gravity, ensuring the use effect.
[0052] In one embodiment, there are at least two support members 12, and the at least two support members 12 are arranged on the placement rack 11 along the length direction of the placement rack 11. It can be understood that during the wafer production process, the staff needs to collect Wafer ID information, separate films, classify, etc. for the wafers in two or more wafer placement boxes at the same time. In this application, by arranging two or more support members 12 on the placement rack 11, each support member 12 can be used to place a wafer placement box, so that at least two wafer placement boxes can be placed on the placement platform 1 at the same time, facilitating the staff to operate on the wafers in two wafer placement boxes at the same time.
[0053] Specifically, in the embodiments of the present application, there are two support members 12. The two support members 12 are arranged on the placement rack 11 along the length direction of the placement rack 11, and the two support members 12 are connected to each other to effectively utilize the space on the placement rack 11. And by operating two wafer placement boxes simultaneously, batch processing can be achieved, reducing the time cost of a single operation and improving the overall production efficiency. Processing two wafer placement boxes simultaneously can also reduce the idle time of the equipment, ensure the continuity of the production line, and avoid equipment idleness caused by the processing of a single wafer placement box. When collecting Wafer ID information or performing film separation operations, processing two wafer placement boxes simultaneously can reduce the number of times the wafers move between different devices or workstations, thereby reducing the risk of contamination. When collecting Wafer ID information for the wafers in two wafer placement boxes simultaneously, data recording and management can be completed more efficiently, facilitating subsequent quality traceability. During the film separation and classification processes, processing two wafer placement boxes simultaneously can quickly screen out the wafers that meet the requirements and improve the classification efficiency. Therefore, by enabling the staff to operate the wafers in two wafer placement boxes simultaneously, the present application can not only improve production efficiency, reduce the risk of contamination, but also optimize the process flow and enhance data management capabilities, thereby achieving efficient and high-quality wafer production.
[0054] In one of the embodiments, the cross-section of the support member 12 along the length direction of the placement rack 11 is a square surface, the cross-section of the support member 12 along the width direction of the placement rack 11 is a triangular surface, and the cross-section of the support member 12 along the height direction of the placement rack 11 is a triangular surface. That is, the support member 12 has a solid triangular structure. Compared with other frame structures with inclined surfaces, the solid triangular structure can not only provide an inclined surface with respect to the geoid, but also provide a relatively high supporting force for the wafer placement box. And compared with other frame structures with inclined surfaces, the overall structure of the solid triangular structure is also simpler, and the production cost is lower.
[0055] In one of the embodiments, the placement rack 11 includes a placement plate 111 and an adjustment frame 112, and the support member 12 is arranged on the placement plate 111. The placement plate 111 can ensure that it has a large planar contact area through its plate-like structure, which is convenient for connecting with the support member 12 and can also provide better connection strength and stability after connection.
[0056] The adjustment frame 112 is arranged on the placement plate 111 and can adjust the angle between the placement plate 111 and the geoid, so as to ensure that when the placement rack 11 is placed on various bearing surfaces, the angle between the support surface 121 and the installation surface can be adjusted to a specified angle through the adjustment frame 112.
[0057] In one embodiment, the support member 12 and the placement rack 11 are of an integrally formed structure, so as to reduce the assembly and processing steps between the support member 12 and the placement rack 11, thereby significantly shortening the production cycle and improving the production efficiency. In addition, by integrating the support member 12 and the placement rack 11 into a whole, the structural strength and stiffness of the placement platform 1 can also be effectively improved.
[0058] According to another aspect of the present application, there is provided a wafer placement method for the placement device of any of the above embodiments, including:
[0059] Adjust the angle of the placement platform 1 so that the placement plate 111 of the placement platform 1 is parallel to the geoid, so that the angle between the support surface 121 and the geoid is a specified angle. In the embodiment of the present application, the specified angle is 5°.
[0060] Place the wafer placement box on the support surface 121 of the support member 12, so that each wafer in the wafer placement box can tilt to the same side under the action of gravity, and be arranged at equal intervals, which helps to protect the wafers, improve the processing efficiency, and optimize the detection and storage processes, thereby improving the overall quality and efficiency of semiconductor manufacturing.
[0061] Specifically, place two wafer placement boxes on the support surfaces 121 of two support members 12 respectively, so that the staff can operate on the wafers in the two wafer placement boxes at the same time, so as to improve the production efficiency, reduce the pollution risk, optimize the process flow, and enhance the data management ability, and realize efficient and high-quality wafer production.
[0062] When the placement method of the present application is used for the above wafer placement device, by making the support surface 121 of the placement platform 1 for supporting the wafer placement box be an inclined surface, after the wafer placement box is placed on the support surface 121 of the placement platform 1, each wafer in the wafer placement box can tilt to the same side under the action of gravity, and then be arranged at equal intervals, without the need for the staff to manually adjust the positions of the wafers to keep the intervals between the wafers consistent, effectively shortening the placement time of the wafers, improving the placement efficiency and placement accuracy of the wafers, and effectively ensuring the accuracy and consistency of subsequent processing.
[0063] The technical features of the above embodiments can be combined arbitrarily. For the sake of brevity of description, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, it should be considered to be within the scope described in this specification.
[0064] The above-described embodiments merely represent several implementation manners of the present application. The description thereof is relatively specific and detailed, but it should not be construed as a limitation to the scope of the patented application. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present application, several modifications and improvements can still be made, and these all fall within the protection scope of the present application. Therefore, the protection scope of the patent of the present application shall be subject to the appended claims.
Claims
1. A wafer placement device, characterized in that, Comprising: A placement platform, including a placement rack and a support member. The support member is disposed on the mounting surface of the placement rack. The support member has a support surface for supporting a wafer placement box. The support surface faces away from the mounting surface, and the support surface is an inclined surface.
2. The wafer placement device according to claim 1, wherein, The wafer placement device further includes a shielding assembly. The shielding assembly is disposed on the placement platform and cooperates to enclose a protection area. The support surface is located within the protection area.
3. The wafer placement device according to claim 1, wherein The support member has an upper surface facing away from the placement rack. The area of the support surface is equal to the area of the bottom surface of the wafer placement box. The upper surface includes the support surface. The area of the upper surface is greater than or equal to the area of the support surface and less than or equal to twice the area of the support surface.
4. The wafer placement device according to claim 1, characterized in that, The angle between the support surface and the mounting surface is greater than 4° and less than 6°.
5. The wafer placement device according to claim 1, wherein At least two support members are provided. At least two support members are disposed on the placement rack along the length direction of the placement rack.
6. The wafer placement device according to claim 1, wherein, The cross-section of the support member along the length direction of the placement rack is a square surface. The cross-section of the support member along the width direction of the placement rack is a triangular surface. The cross-section of the support member along the height direction of the placement rack is a triangular surface.
7. The wafer placement device according to claim 1, wherein The support member and the placement rack are of an integrally formed structure.
8. The wafer placement device according to claim 1, characterized in that, The placement rack includes a placement plate. The support member is disposed on the placement plate.
9. The wafer placement device according to claim 8, characterized in that, The placement rack further includes an adjustment frame body. The adjustment frame body is disposed on the placement plate and can adjust the angle between the placement plate and the geoid.
10. A wafer placement method, characterized in that, For the placement device according to any one of claims 1-9, including: Adjust the angle of the placement platform so that the placement plate of the placement platform is parallel to the geoid; Place the wafer placement box on the support surface of the support member so that each wafer in the wafer placement box can tilt to the same side under the action of gravity for equidistant arrangement.