A double-sided adsorption device used as a connector in a wafer flattening process

Abstract

A double-sided adsorption device used as a connecting piece in a wafer flattening process includes an adsorption body with a certain thickness and two upper and lower end faces. The upper end face of the adsorption body serves as an upper adsorption area for adsorbing a polishing head, and the lower end face serves as a lower adsorption area for adsorbing wafers; an air flow channel is provided inside. The upper adsorption area is provided with multiple groups of concentric circular grooves, all of which are connected to the air flow channel; the lower adsorption area is provided with multiple adsorption holes, all of which are connected to the air flow channel; the adsorption holes are distributed in concentric circles, and the spacing between two adjacent adsorption holes on the same circle is the same, and the spacing decreases gradually from the inner circle to the outer circle; a sealing ring is provided at the edge of the lower adsorption area, and the lower end face protrudes downward, serving as a positioning ring for the wafer, and the protruding section and the lower adsorption area jointly define a space for installing the wafer, and the lower end face of the protruding section is higher than or level with the lower end face of the wafer; an isolation groove is provided between the sealing ring and the outermost adsorption hole, and the isolation groove is connected to the air flow channel.

Description

Technical Field

[0001] The present invention relates to the field of semiconductor technology, and in particular to a double-sided adsorption device used as a connecting piece in a wafer flattening process. Background Art

[0002] Silicon wafers are widely used as substrate materials for semiconductor devices. Silicon wafers are manufactured by sequentially performing the following processes on single-crystal silicon ingots: peripheral grinding, slicing, lapping, etching, double-sided polishing, single-sided polishing, cleaning, etc. Flatness is a variety of parameters used to characterize properties such as wafer morphology and thickness, including: warpage (BOW), deformation (Warp), deformation about the fitting surface (SORI), maximum thickness deviation (TTV), etc.

[0003] Among them, the single-side polishing process is a necessary process to eliminate the bumps or ups and downs on the wafer surface to improve the flatness, and the CMP (Chemical Mechanical Polishing) method is used for mirror processing. Chemical mechanical polishing technology has both mechanical polishing with abrasive properties and chemical polishing with acid and alkali resistant solutions, which can make the wafer surface fully flat, so that the subsequent thin film deposition can be carried out.

[0004] CMP polishing devices are used in the substrate industry, window industry, IC manufacturing industry and MEMS flattening manufacturing process. CMP polishing devices usually include a polishing disc, a polishing pad attached to the polishing disc, and a polishing head arranged above the polishing pad. During the polishing process, the wafer is pressed close to the polishing pad by a polishing head, and polishing liquid is dripped on the polishing pad while the polishing disc and the polishing head are rotated respectively. The two effects of chemical corrosion and mechanical friction are carried out alternately and cyclically, thereby polishing a single side of the wafer.

[0005] Among them, the wafer and the polishing head are relatively fixed through a wafer carrier such as a ceramic disk, and the wafer is fixed between the wafer and the ceramic disk by applying solid wax, melting it and then solidifying it. However, this method takes a long time to process and is inconvenient to operate. In addition, the sticking of solid wax cannot ensure the uniformity of the wax layer, which causes the wafer to bend and deform, making its surface uneven and prone to over-polishing. And the wax needs to be removed later, which can easily cause the wafer to break. For wafers of different sizes, the polishing head in the polishing device needs to be replaced with a polishing head of the corresponding size, and the wafer needs to be waxed. If the wafer is not a non-standard part but a special size, it may also be necessary to replace the waxing machine, which is costly.

[0006] In addition, the wafer surface is distorted and has a warpage (BOW) value, especially at the edge of the wafer, where the warpage is higher, affecting the flatness of the wafer. Before polishing, solid wax is generally filled in the concave part of the surface of the wafer facing the ceramic plate to make the surface of the wafer to be polished flat, but solid wax cannot guarantee the uniformity of the wax layer, and thus the surface quality of the wafer cannot be guaranteed. At the same time, the wax removal step is required, which is inconvenient to operate.

[0007] In view of this, the present invention aims to design a dedicated wafer connection and fixing device that is non-destructive to the wafer, easy to operate, and low-cost for the wafer flattening single-side polishing process. Summary of the invention

[0008] The object of the present invention is to provide a double-sided adsorption device used as a connecting piece in a wafer flattening process.

[0009] In order to achieve the above object, the technical solution adopted by the present invention is:

[0010] A double-sided adsorption device used as a connecting piece in a wafer flattening process comprises an adsorption body with a certain thickness, wherein the thickness direction of the adsorption body is defined as an up-and-down direction; the adsorption body has two upper and lower end faces.

[0011] The upper end surface of the adsorption body serves as the upper adsorption area for adsorbing the polishing head, and the lower end surface of the adsorption body serves as the lower adsorption area for adsorbing the wafer; an air flow channel is arranged inside the adsorption body, and a vacuum port for connecting to a vacuum generator is provided in the air flow channel.

[0012] The upper adsorption area is provided with a plurality of groups of concentric circular grooves, and each of the circular grooves is connected to the air flow channel;

[0013] The lower adsorption area is provided with a plurality of adsorption holes, each of which is connected to the airflow channel; the adsorption holes are distributed in the shape of concentric circles on the lower adsorption area, and the spacing between two adjacent adsorption holes on the same circle is the same, and the spacing decreases gradually from the inner circle to the outer circle of the concentric circle; the airflow channel, the circular groove and the adsorption holes jointly define a vacuum chamber;

[0014] A sealing ring is provided at the edge of the lower adsorption area, and the lower end surface of the sealing ring protrudes downward relative to the lower adsorption area, the protruding section of the sealing ring serves as a positioning ring of the wafer, and the protruding section of the sealing ring and the lower adsorption area jointly define a space for installing the wafer, and the lower end surface of the protruding section of the sealing ring is higher than or level with the lower end surface of the wafer; an isolation groove is provided between the sealing ring and the outermost adsorption hole, and the isolation groove is connected to the airflow channel.

[0015] The relevant contents in the above technical solution are explained as follows:

[0016] 1. In the above scheme, the use process of this technical scheme is: first flip the adsorption body so that the lower adsorption area is set upward, and the wafer is embedded in the protruding section of the sealing ring and fixed, and the wafer fits the lower adsorption area. Then flip the adsorption body so that the lower adsorption area faces downward, and the wafer is fixed by the sealing ring and will not fall off. The upper adsorption area faces upward, aligns and fits to the lower surface of the polishing head, and then vacuum is applied. The wafer is adsorbed and fixed on the lower adsorption area of ​​the adsorption device, and the adsorption device and the wafer are adsorbed and fixed on the polishing head as a whole, that is, the adsorption device is used as a connector between the wafer and the polishing head. Then perform polishing. After polishing is completed, stop vacuuming, first remove the adsorption device and the wafer as a whole from the polishing head, then flip the adsorption device so that the lower adsorption area is set upward, and then take out the wafer.

[0017] 2 In the above scheme, adsorption devices of different sizes are designed and processed according to different wafer diameter sizes, and the density of holes can be customized according to the degree of wafer warping. When wafers of different sizes need to be fixed, the adsorption device can be directly replaced. However, for wafers of different sizes, it is necessary to replace the polishing head in the polishing device with a polishing head of the corresponding size. For wafers of special sizes, it is even necessary to customize the polishing head, which is costly and time-consuming. At the same time, the wafer needs to be waxed. If the wafer is not a non-standard part but a special size, it may be necessary to replace the waxing machine, which is costly. In addition, the adsorption device of the present technical solution has strong versatility and is suitable for single-sided polishing, grinding, and MEMS flattening manufacturing processes in the flattening process. In summary, the present technical solution is easy to operate, low-cost, highly versatile, stable in connection, and convenient for non-standard customization.

[0018] 3. In the above scheme, this technical scheme uses an adsorption device to adsorb and fix the wafer, and combines a sealing ring on the lower adsorption area to assist in fixing the wafer. It is easy to operate and stable to fix. It can be wax-free and wax-free. The wafer can be subsequently cleaned with pure water to remove the polishing liquid. There is no need for special cleaning and wax removal, and the wafer can be fixed without damage. In addition, the adsorption holes on the lower adsorption area are unevenly distributed, with dense outer layers and sparse inner layers, which can achieve the wafer being stretched and flattened on the surface of the adsorption device, reduce the warpage (BOW), and avoid over-polishing of the wafer.

[0019] 4. In the above scheme, the adsorption holes are distributed in concentric circles on the lower adsorption area, and the spacing between two adjacent adsorption holes on the same circle is the same, and the spacing decreases gradually from the inner circle to the outer circle of the concentric circle. This means that the adsorption holes are distributed non-uniformly, and the spacing between adjacent adsorption holes in the outer layer is smaller than the spacing between the adsorption holes in the inner layer, that is, the adsorption holes in the outer layer are more densely distributed, and their corresponding adsorption force is stronger, and the adsorption holes in the inner layer are more sparse, and their corresponding adsorption force is weaker. The edge of the wafer is more warped than the middle part. When the wafer is adsorbed in the lower adsorption area, the adsorption force on its edge is stronger and the adsorption force on the middle is weaker, so that the wafer is stretched from the center to the edge, thereby reducing the warping of the wafer. According to the warping of the wafer, the spacing between layers and the spacing between adsorption holes on the same layer can be customized.

[0020] 5. In the above scheme, this technical scheme designs a double-sided perforated and grooved adsorption device, which adsorbs the polishing head on the upper side and the wafer on the lower side. A circular groove is set in the upper adsorption area, and an adsorption hole is set in the lower adsorption area, and the circular groove and the adsorption hole are both connected to the air flow channel, that is, the circular groove, the adsorption hole and the air flow channel together form a vacuum chamber. When evacuating, the upper adsorption area and the lower adsorption area generate adsorption force at the same time. The circular groove has a larger air extraction area than the adsorption hole, the purpose is to make the adsorption force of the upper adsorption area greater. In this technical scheme, the upper adsorption area and the lower adsorption area share a common air flow channel. Because the wafer is small in size and light in weight, the adsorption force required is small, usually between 50 microns and 5 mm, so the shared air flow channel will not affect the adsorption force on the wafer. If independent air flow channels are used, the structure is more complicated, and the two parts need to be spliced ​​and connected. This technical scheme uses a common air flow channel, which simplifies the structure, is simple to process, and is also simple to operate during the polishing process.

[0021] 6. In the above scheme, a sealing ring is provided at the edge of the lower adsorption area, and the lower end surface of the sealing ring protrudes downward relative to the lower adsorption area. The protruding section of the sealing ring serves as a positioning ring for the wafer, and the protruding section of the sealing ring and the lower adsorption area together define a space for installing the wafer. The sealing ring is used to seal the lower adsorption area of ​​the adsorption device to prevent the polishing liquid from entering the adsorption holes of the lower adsorption area, resulting in a decrease in adsorption force and even causing the wafer to fall off. The protruding section of the sealing ring also serves as a positioning ring for the wafer. The diameter of the sealing ring is generally slightly smaller than the diameter of the wafer. The wafer is clamped in the protruding section of the sealing ring to assist in positioning the wafer.

[0022] 7. In the above scheme, an isolation groove is provided between the sealing ring and the outermost adsorption hole, and the isolation groove is connected to the airflow channel. When polishing liquid flows into the lower adsorption area, the polishing liquid is discharged through the isolation groove to prevent the polishing liquid from entering the adsorption hole and affecting the adsorption force.

[0023] 8. In the above scheme, in the two adjacent circles of adsorption holes, the number of adsorption holes in the outer circle is 5 to 15 more than the number of adsorption holes in the inner circle.

[0024] 9. In the above solution, a plurality of ventilation holes are provided at the bottom of the circular groove, and the circular groove is connected with the air flow channel through the ventilation holes.

[0025] 10. In the above solution, the vacuum port is located on the side of the adsorption body.

[0026] 11. In the above solution, the air flow channel is arranged along the radial direction of the adsorption body.

[0027] 12. In the above solution, a sealing groove is provided at the edge of the lower adsorption area, and the sealing ring is embedded in the sealing groove. The lower end surface of the outer groove wall of the sealing groove is lower than the lower end surface of the inner groove wall of the sealing groove.

[0028] The working principle of the present invention is as follows: the present invention uses the adsorption device as a connector between the wafer and the polishing head. First, the adsorption body is turned over so that the lower adsorption area is set upward, and the wafer is embedded in the protruding section of the sealing ring and fixed, and the wafer is attached to the lower adsorption area. Then the adsorption body is turned over so that the lower adsorption area is facing downward, and the wafer is fixed by the sealing ring and will not fall off. The upper adsorption area is facing upward, aligned and attached to the lower surface of the polishing head, and then vacuum is drawn. The wafer is adsorbed and fixed on the lower adsorption area of ​​the adsorption device, and the adsorption device and the wafer are adsorbed and fixed on the polishing head as a whole. Through the double-sided adsorption of the adsorption device, the wafer and the polishing head are relatively fixed, and then the polishing process is performed. After the polishing is completed, the vacuum is stopped, and the adsorption device and the wafer are first removed from the polishing head as a whole, and then the adsorption device is turned over so that the lower adsorption area is set upward, and then the wafer is taken out.

[0029] Due to the application of the above technical solution, the present invention has the following advantages compared with the prior art:

[0030] 1. Since the present invention adopts a double-sided adsorption device in the flattening process, the wafer and the polishing head are relatively connected and fixed. For wafers of different sizes, wafers with different warpages, and even wafers of special sizes, adsorption devices of different specifications can be customized at low cost. Avoid replacing the polishing head or customizing the polishing head, which is costly and time-consuming. In summary, the double-sided adsorption device of the present invention is easy to operate, low-cost, highly versatile, has stable connection, and is convenient for non-standard customization.

[0031] 2. Since the present invention mainly adopts adsorption to fix the wafer, combined with a sealing ring to assist in fixing the wafer, it is easy to operate and stable to fix. Waxing-free and wax-free wafer fixing can be achieved, and it is easy to clean and can fix the wafer without damage.

[0032] 3. Since the adsorption holes of the adsorption wafer of the present invention are distributed non-uniformly, with dense outer layers and sparse inner layers, the adsorption force of the outer layer is stronger and the adsorption force of the inner layer is weaker, the adsorption force on the edge of the wafer is stronger and the adsorption force in the middle is weaker, so that the wafer is stretched from the center to the edge, the warpage (BOW) of the wafer is reduced, the flatness is improved, and the wafer is prevented from being over-polished. And according to the warpage of different batches of wafers, the spacing between the adsorption holes and the spacing between the adsorption holes on the same layer can be customized.

[0033] 4. Since the present invention is provided with a sealing ring, it can not only prevent the polishing liquid from entering the adsorption hole of the lower adsorption area to ensure the adsorption force, but also serve as a positioning ring for the wafer to assist in fixing the wafer, facilitate wafer loading, and fix it to the adsorption device. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Attached Figure 1 A three-dimensional diagram of the upper adsorption area of ​​the adsorption device according to an embodiment of the present invention;

[0035] Attached Figure 2 A three-dimensional diagram of the lower adsorption area of ​​the adsorption device according to an embodiment of the present invention;

[0036] Attached Figure 3 A three-dimensional cross-sectional view from the perspective of the upper adsorption area of ​​the adsorption device according to an embodiment of the present invention;

[0037] Attached Figure 4 A three-dimensional cross-sectional view of the lower adsorption area of ​​the adsorption device according to an embodiment of the present invention;

[0038] Attached Figure 5 is a cross-sectional view of an adsorption device according to an embodiment of the present invention;

[0039] Attached Figure 6 This is a diagram showing the use status of the adsorption device of an embodiment of the present invention as a connecting piece between a wafer and a polishing head.

[0040] In the above drawings: 1. adsorption body; 2. upper adsorption area; 3. lower adsorption area; 4. polishing head; 5. wafer; 6. air flow channel; 7. vacuum port; 8. circular groove; 9. adsorption hole; 10. sealing ring; 11. isolation groove; 12. sealing groove; 13. polishing pad; 14. polishing disk. DETAILED DESCRIPTION

[0041] The present invention will be further described below in conjunction with the accompanying drawings and embodiments:

[0042] Example 1: A double-sided adsorption device as a connector in a wafer flattening process

[0043] See attached Figure 1~2As shown, the double-sided adsorption device includes an adsorption body 1 with a certain thickness, and the thickness direction of the adsorption body 1 is defined as the up and down direction; the adsorption body 1 has two upper and lower end surfaces.

[0044] See attached Figures 3-5 As shown, the upper end surface of the adsorption body 1 serves as the upper adsorption area 2 for adsorbing the polishing head 4, and the lower end surface of the adsorption body 1 serves as the lower adsorption area 3 for adsorbing the wafer 5; an airflow channel 6 is provided inside the adsorption body 1, and a vacuum port 7 for connecting to a vacuum generator is provided in the airflow channel 6; the vacuum port 7 is located on the side of the adsorption body 1. The airflow channel 6 is arranged along the radial direction of the adsorption body 1.

[0045] The upper adsorption area 2 is provided with a plurality of groups of concentric circular grooves 8, each of which is connected to the air flow channel 6. A plurality of vents are provided at the bottom of the circular grooves 8, and the circular grooves 8 are connected to the air flow channel 6 through the vents.

[0046] The lower adsorption area 3 is provided with a plurality of adsorption holes 9, each of which is connected to the airflow channel 6; the adsorption holes 9 are distributed in concentric circles on the lower adsorption area 3, and the spacing between two adjacent adsorption holes 9 on the same circle is the same, and the spacing decreases gradually from the inner circle to the outer circle of the concentric circle; the airflow channel 6, the circular groove 8 and the adsorption holes 9 jointly define a vacuum chamber. In two adjacent circles of adsorption holes 9, the number of adsorption holes 9 in the outer circle is 5 to 15 more than the number of adsorption holes 9 in the inner circle.

[0047] A sealing ring 10 is provided at the edge of the lower adsorption area 3, and the lower end surface of the sealing ring 10 protrudes downward relative to the lower adsorption area 3. The protruding section of the sealing ring 10 serves as a positioning ring for the wafer 5, and the protruding section of the sealing ring 10 and the lower adsorption area 3 jointly define a space for installing the wafer 5, and the lower end surface of the protruding section of the sealing ring 10 is higher than or level with the lower end surface of the wafer 5; an isolation groove 11 is provided between the sealing ring 10 and the outermost adsorption hole 9, and the isolation groove 11 is connected to the airflow channel 6. A sealing groove 12 is provided at the edge of the lower adsorption area 3, and the sealing ring 10 is embedded in the sealing groove 12.

[0048] The loading process of this embodiment is as follows: first, the adsorption body 1 is turned over so that the lower adsorption area 3 is set upward, and the wafer 5 is embedded in the protruding section of the sealing ring 10 and fixed, and the wafer 5 fits the lower adsorption area 3. Then, the adsorption body 1 is turned over so that the lower adsorption area 3 faces downward, and the wafer 5 is fixed by the sealing ring 10 and will not fall off. The upper adsorption area 2 faces upward, aligns and fits to the lower surface of the polishing head 4, and then vacuum is drawn. The wafer 5 is adsorbed and fixed on the lower adsorption area 3 of the adsorption device, and the adsorption device and the wafer 5 are adsorbed and fixed on the polishing head 4 as a whole. Through the double-sided adsorption of the adsorption device, the wafer 5 and the polishing head 4 are relatively fixed, and then the polishing process is performed. After polishing is completed, stop vacuuming, first remove the adsorption device and the wafer 5 as a whole from the polishing head 4, then turn the adsorption device over so that the lower adsorption area 3 faces upward, and then take out the wafer 5.

[0049] See attached Figure 6 As shown, when the embodiment is working, the adsorption device adsorbs on both sides, the lower adsorption area 3 adsorbs and fixes the wafer 5, and the upper adsorption area 2 adsorbs and fixes it to the polishing head 4. The adsorption device serves as a connecting piece to connect and fix the wafer 5 and the polishing head 4. The polishing plate 14 is attached to the polishing pad 13, and the wafer 5 is pressed close to the polishing pad 13 by the polishing head 4. While dripping polishing liquid on the polishing pad 13, the polishing plate 14 and the polishing head 4 are rotated respectively. The two effects of chemical corrosion and mechanical friction are performed alternately and cyclically, thereby polishing the lower surface of the wafer 5.

[0050] The above embodiments are only for illustrating the technical concept and features of the present invention, and their purpose is to enable people familiar with the technology to understand the content of the present invention and implement it accordingly, and they cannot be used to limit the protection scope of the present invention. Any equivalent changes or modifications made according to the spirit of the present invention should be included in the protection scope of the present invention.

Claims

1. A double-sided adsorption device as a connecting member in a wafer flattening process, characterized in that: The double-sided adsorption device comprises an adsorption body (1) having a certain thickness, wherein the thickness direction of the adsorption body (1) is defined as an up-down direction; the adsorption body (1) has two upper and lower end surfaces; The upper end surface of the adsorption body (1) serves as an upper adsorption area (2) for adsorbing a polishing head (4), and the lower end surface of the adsorption body (1) serves as a lower adsorption area (3) for adsorbing a wafer (5); an air flow channel (6) is provided inside the adsorption body (1), and the air flow channel (6) is provided with a vacuum port (7) for communicating with a vacuum generator; The upper adsorption area (2) is provided with a plurality of groups of concentric circular grooves (8), and each of the circular grooves (8) is connected to the air flow channel (6); The lower adsorption area (3) is provided with a plurality of adsorption holes (9), each of which is in communication with the airflow channel (6); the adsorption holes (9) are distributed in the form of concentric circles on the lower adsorption area (3), and the spacing between two adjacent adsorption holes (9) on the same circle is the same, and the spacing decreases gradually from the inner circle to the outer circle of the concentric circle; the airflow channel (6), the circular groove (8) and the adsorption holes (9) jointly define a vacuum chamber; A sealing ring (10) is provided at the edge of the lower adsorption area (3), and the lower end surface of the sealing ring (10) protrudes downward relative to the lower adsorption area (3), the protruding section of the sealing ring (10) serves as a positioning ring for the wafer (5), and the protruding section of the sealing ring (10) and the lower adsorption area (3) together define a space for mounting the wafer (5), and the lower end surface of the protruding section of the sealing ring (10) is higher than or flush with the lower end surface of the wafer (5); an isolation groove (11) is provided between the sealing ring (10) and the outermost adsorption hole (9), and the isolation groove (11) is connected to the air flow channel (6).

2. The double-sided adsorption device as a connection member in the wafer flattening process according to claim 1, characterized in that: In two adjacent circles of adsorption holes (9), the number of adsorption holes (9) in the outer circle is 5 to 15 more than the number of adsorption holes (9) in the inner circle.

3. The double-sided adsorption device as a connection member in the wafer flattening process according to claim 1, characterized in that: A plurality of ventilation holes are provided at the bottom of the circular groove (8), and the circular groove (8) is connected to the air flow channel (6) through the ventilation holes.

4. The double-sided adsorption device as a connection member in the wafer flattening process according to claim 1, characterized in that: The vacuum port (7) is located on the side of the adsorption body (1).

5. The double-sided adsorption device as a connection member in the wafer flattening process according to claim 1, characterized in that: The air flow channel (6) is arranged along the radial direction of the adsorption body (1).

6. The double-sided adsorption device as a connection member in the wafer flattening process according to claim 1, characterized in that: A sealing groove (12) is provided at the edge of the lower adsorption area (3), and the sealing ring (10) is embedded in the sealing groove (12).

7. The double-sided adsorption device as a connection member in the wafer flattening process according to claim 6, characterized in that: The lower end surface of the outer groove wall of the sealing groove (12) is lower than the lower end surface of the inner groove wall of the sealing groove (12).

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