TW202231405A - System and method for chemical mechanical polishing - Google Patents

Abstract

A chemical mechanical polishing system is provided. The chemical mechanical polishing system comprises a polishing head fixing a silicon slice, a pressing mechanism providing a pressure of the polishing head on a front surface of the silicon slice, a distance sensor generating a distance signal for sensing a distance comprising a real-time thickness of the silicon slice and transmitting the distance signal to a controlling unit for calculation to obtain the real-time thickness of the silicon slice, and the controlling unit adjusting the pressing mechanism according to a target thickness of the silicon slice and the real-time thickness of the silicon slice. During a final polishing process, the pressure of the pressing mechanism may be automatically adjusted through real-time thickness of the silicon slice measured by the distance sensor to control flatness of the silicon slice in a better way.

Description

Chemical mechanical polishing system and chemical mechanical polishing monitoring method

The invention relates to the technical field of semiconductor element manufacturing, in particular to a chemical mechanical polishing system and a chemical mechanical polishing monitoring method.

Chemical Mechanical Polishing (CMP), also known as chemical mechanical polishing or chemical mechanical planarization, is a key and essential technology in silicon wafer manufacturing. It polishes the surface of silicon wafers by chemical reaction and mechanical grinding. , achieve the desired flatness and remove surface defects or damaged layers.

The surface polishing of silicon wafers often needs to be completed by two polishing steps: double side polish (DSP, double side polish) and front final polish (FP, final polish). Double-sided polishing is used to grind the front and back sides of the wafer, and the desired wafer shape can be achieved through the control of the polishing table, while the final polishing only polishes the front side of the wafer.

In the final polishing process of 12-inch silicon wafers, there are high requirements for the surface flatness and uniformity of pure silicon wafers. However, the current final polishing machine does not flatten the surface of pure silicon wafers (bare wafers) during the final polishing process. Real-time monitoring function.

The purpose of the present invention is to provide a chemical mechanical polishing system and monitoring method to solve the problem of real-time monitoring of the surface flatness of pure silicon wafers in the final polishing process.

In order to solve the above technical problems, the present invention provides a chemical mechanical polishing system, comprising: a polishing head, which is used to fix a pure silicon wafer; and a pressing mechanism, which provides the polishing head to press the pure silicon wafer pressure on the upper surface of the The control unit is transmitted to the control unit for calculation to obtain the real-time thickness of the pure silicon wafer; and the control unit is used for adjusting the pressure mechanism of the pressing mechanism according to the target thickness of the pure silicon wafer and the real-time thickness data of the pure silicon wafer pressure; wherein, the pressing mechanism is located above the polishing head and is fixedly connected with the polishing head, and the control unit is electrically connected to the pressing mechanism and the distance sensor respectively.

Optionally, the distance sensor includes a first distance sensor and a second distance sensor, and the first distance sensor and the second distance sensor detect the real The thickness distance signal is transmitted to the control unit, and the control unit calculates the real-time thickness of the pure silicon wafer through the distance difference between the first distance sensor and the second distance sensor.

Optionally, the number of the first distance sensors is multiple.

Optionally, an internal back plate is further provided below the polishing head, and a first rotating mechanism is further provided above the polishing head, the first rotating mechanism connects the polishing head and the internal back plate, and drives the polishing head and the internal back plate. Internal backplate rotates.

Optionally, the first distance sensor is fixed on the inner backplane.

Optionally, the chemical mechanical polishing system for silicon wafers further includes a polishing table, and grooves are provided on the polishing table.

Optionally, the second distance sensor is fixed in the groove of the polishing table, and the surface of the second distance sensor is flush with the surface of the polishing table.

Based on the same inventive concept, the present invention also provides a chemical mechanical polishing monitoring method, comprising: using a polishing head to press a pure silicon wafer onto a polishing pad to polish the pure silicon wafer; and a distance sensor detects that the pure silicon wafer contains the pure silicon The distance signal of the real-time thickness of the wafer is transmitted, and the detected distance signal including the real-time thickness of the pure silicon wafer is transmitted to the control unit for calculation, so as to obtain the real-time thickness of the pure silicon wafer. The target thickness of the wafer and the real-time thickness data of the pure silicon wafer adjust the pressure provided by the pressing mechanism to the polishing head in real time.

Optionally, the distance sensor includes a first distance sensor and a second distance sensor, and the first distance sensor and the second distance sensor detect the real The thickness distance signal is transmitted to the control unit, and the control unit detects the real-time thickness of the pure silicon wafer through the distance difference between the first distance sensor and the second distance sensor.

Optionally, the thickness of the rubber ring, the adsorption pad and the polishing pad is subtracted from the distance difference between the first distance sensor and the second distance sensor, so as to obtain the measured value of the pure silicon wafer. Instant thickness.

Compared with the prior art, the beneficial effects of the present invention are as follows: in the chemical mechanical polishing system and monitoring method provided by the present invention, the distance signal including the real-time thickness of the pure silicon wafer is detected by the distance sensor, and the detected The distance signal including the real-time thickness of the pure silicon wafer is transmitted to the control unit for calculation to obtain the real-time thickness of the pure silicon wafer in the final polishing process, and the real-time thickness data of the pure silicon wafer is fed back to the control unit; the control unit Adjust the pressure of the pressing mechanism according to the target thickness of the pure silicon wafer and the real-time thickness of the pure silicon wafer, so that the pure silicon wafer can obtain the target polishing shape. Pure silicon wafer flatness control.

The chemical mechanical polishing system and its monitoring method proposed by the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. The advantages and features of the present invention will become more apparent from the following description and claims. It should be noted that, the accompanying drawings are all in a very simplified form and in inaccurate scales, and are only used to facilitate and clearly assist the purpose of explaining the embodiments of the present invention.

Specifically, please refer to FIGS. 1-6. FIG. 1 is a schematic structural diagram of a chemical mechanical polishing system according to an embodiment of the present invention, FIG. 2 is a schematic top view of a polishing table according to an embodiment of the present invention, and FIG. 3 is a top view of a polishing head according to an embodiment of the present invention. A schematic bottom view of the first distance sensor, FIG. 4 is a bottom schematic view of a plurality of first distance sensors on a polishing head according to an embodiment of the present invention, FIG. 5 is a schematic cross-sectional view of the polishing head according to an embodiment of the present invention, and FIG. A schematic exploded cross-sectional view of a polishing head according to an embodiment of the invention.

As shown in FIGS. 1-6 , this embodiment provides a chemical mechanical polishing system, including: a polishing head 10 for fixing a pure silicon wafer 14 ; a pressing mechanism 11 , which provides the The pressure of the polishing head 10 pressing on the upper surface of the pure silicon wafer 14; the distance sensor, the distance sensor is used to detect the distance signal including the real-time thickness of the pure silicon wafer 14, and the detected distance signal includes The distance signal of the real-time thickness of the pure silicon wafer 14 is transmitted to the control unit 30 for calculation to obtain the real-time thickness of the pure silicon wafer 14; the control unit 30 is electrically connected to the pressing mechanism 11 and the distance sensor respectively. The control unit 30 is configured to adjust the pressure of the pressing mechanism 11 according to the target thickness of the pure silicon wafer 14 and the real-time thickness data of the pure silicon wafer 14; wherein the pressing mechanism is located above the polishing head, and is fixedly connected with the polishing head, and the control unit is electrically connected to the pressing mechanism and the distance sensor respectively.

As a non-limiting example, the pressure adjustment rule of the pressing mechanism may refer to the following formula: incoming thickness of pure silicon wafer - target thickness of pure silicon wafer = set pressure * removal coefficient; The incoming thickness refers to the initial thickness of pure silicon wafers.

In specific implementation, the removal coefficient can be obtained according to an empirical formula, that is, the linear relationship between the pressure of the polishing head 10 pressing on the upper surface of the pure silicon wafer 14 and the removal amount (thickness that is ground off), to obtain a fixed value (that is, the removal coefficient), when the incoming thickness of pure silicon wafers fluctuates, the pressure to be set can be calculated according to the formula. In this embodiment, the target thickness of the silicon wafer is, for example, 775500 nm. When the real-time thickness of the pure silicon wafer 14 detected by the distance sensor is 776000 nm, and the initial pressure of the pressing mechanism 11 is 0.008 MPa, the removal coefficient is 62500 nm/MPa, When the incoming thickness of pure silicon wafer is 776100nm, in the same polishing time, the pressure needs to be increased to 0.0096MPa to obtain the target thickness of pure silicon wafer.

Continuing to refer to FIG. 1 , the distance sensor includes, for example, a first distance sensor 12 and a second distance sensor 21 . The first distance sensor 12 and the second distance sensor 21 detect The distance signal of the real-time thickness of the pure silicon wafer 14 is transmitted to the control unit 30 , and the control unit 30 calculates the distance difference between the first distance sensor 12 and the second distance sensor 21 Instant thickness of pure silicon wafer 14 . In this embodiment, the distance difference between the two distance sensors needs to be used to test the real-time thickness of the pure silicon wafer 14. This is mainly because the inventor found that no element has been formed on the pure silicon wafer, so The material of each position of the pure silicon wafer is the same, and its reflectivity is also the same. Therefore, it is not suitable to use a single sensor to measure the thickness of the pure silicon wafer.

Continuing to refer to FIG. 2 and FIG. 3 , the number of the first distance sensor 12 may be one or multiple. When a plurality of first distance sensors 12 are used, these first distance sensors 12 are, for example, arranged in an array or are arranged in a radiating shape with the center of a pure silicon wafer as the origin. No restrictions.

Referring to FIGS. 5 and 6 , a pure silicon wafer adsorption pad 13 is disposed under the polishing head 10 (ie, on the side close to the pure silicon wafer), and the pure silicon wafer adsorption pad 13 can be used to adsorb the pure silicon wafer 14 . In this embodiment, the material of the pure silicon wafer adsorption pad 13 is, for example, suede, and the pure silicon wafer adsorption pad 13 is used for adsorbing the pure silicon wafer 14 and protecting the back surface of the pure silicon wafer 14 Will not cause scratches. An inner back plate 16 may also be provided below the polishing head 10 , and a first rotation mechanism 15 may be provided above the polishing head 10 , and the first rotation mechanism 15 is connected to the polishing head 10 and the inner back plate 16, and drive the polishing head 10 and the inner back plate 16 to rotate. A rubber ring 18 is also disposed between the polishing head 10 and the pure silicon wafer adsorption pad 13 , and the pure silicon wafer adsorption pad 13 is pasted on the rubber ring 18 . The rubber ring 18 is sleeved on the outer side of the snap ring 17, the snap ring 17 is fixedly connected with the polishing head 10, and the fixed connection between the snap ring 17 and the polishing head 10 is, for example, a bolt connection.

Please refer to FIGS. 2-3 and 5-6 , the first distance sensor 12 can be fixed on the inner backplane 16 . The fixing method of the first distance sensor 12 on the inner backplane 16 is, for example, snap connection. The first distance sensor 12 is located at the center diameter of the polishing head 10 . When a plurality of first distance sensors 12 are used, these first distance sensors 12 are, for example, arranged in an array or are arranged in a radiating shape with the center of a pure silicon wafer as the origin. No restrictions.

Continuing to refer to FIG. 1 , the chemical mechanical polishing system further includes a polishing table 20 , and the polishing table 20 is provided with at least one groove. The groove is, for example, a strip-shaped groove, extending from the center of the polishing table 20 to the edge of the polishing table 20 , and the length of the groove is greater than the radius of the pure silicon wafer 14 . The second distance sensor 21 can be fixed in the polishing table 20, and keep the second distance sensor 21 and the polishing table 20 at the same level, that is, the top of the second distance sensor 21. The face is flush with the top face of the polishing table 20 . In the final polishing process, when the polishing table 20 is rotated, the second distance sensor 21 can monitor the real-time thickness of each position of the pure silicon wafer 14 .

Further, a polishing pad 22 is disposed on the polishing table 20 . In this embodiment, the material of the polishing table 20 is, for example, ceramic, and the polishing pad 22 is adhered to the polishing table 20 and covers the second distance sensor 21 . The flatter the surface of the polishing table 20 is, the better the uniformity of polishing is. Different materials of the polishing pad 22 are selected according to different processes. In this embodiment, the material of the polishing pad 22 is, for example, a non-woven fabric, and the surface of the polishing pad 22 has several grooves, which can evenly distribute the polishing liquid to all surfaces. Different areas of the polishing pad 22 are used to perform a final polishing process on the front surface of the silicon wafer 14 . The chemical mechanical polishing system further includes a second rotation mechanism 23 for driving the polishing table 20 and the polishing pad 22 to rotate.

As mentioned above, the distance sensor includes the first distance sensor 12 and the second distance sensor 21 , and the distance between the first distance sensor 12 and the second distance sensor 21 is passed through. The difference can test the real-time thickness of the silicon wafer 14 . In this embodiment, since the first distance sensor 12 and the second distance sensor 21 include a rubber ring 18 , a pure silicon wafer adsorption pad 13 , a pure silicon wafer 14 and a polishing pad 22 , the pure silicon wafer 14 and the polishing pad 22 are The real-time thickness of the silicon wafer 14 is the difference between the first distance sensor 12 and the second distance sensor 21 minus the rubber ring 18 , the pure silicon wafer adsorption pad 13 and the polishing pad 22 . thickness of.

FIG. 7 is a schematic flowchart of a chemical mechanical polishing monitoring method according to an embodiment of the present invention. Referring to FIGS. 1-7 , the present embodiment further provides a chemical mechanical polishing monitoring method, including: step S10 , using the polishing head 10 to press the pure silicon wafer 14 onto the polishing pad 22 to polish the pure silicon wafer 14 and step S20, the distance sensor detects the distance signal including the real-time thickness of the pure silicon wafer 14, and transmits the detected distance signal including the real-time thickness of the pure silicon wafer 14 to the control unit 30 for calculation, In order to obtain the real-time thickness of the pure silicon wafer 14, the control unit 30 can adjust the pressure of the pressing mechanism 11 according to the target thickness of the pure silicon wafer 14 and the real-time thickness data of the pure silicon wafer 14, so that the pure The silicon wafer 14 obtains the polished topography of the target thickness.

During chemical mechanical polishing, the pure silicon wafer 14 is fixed on the polishing head 10 , the pure silicon wafer 14 is moved to the top of the polishing table 20 , the pure silicon wafer 14 is pressed onto the polishing table 20 by the polishing head 10 , and The surface to be polished of the pure silicon wafer 14 is brought into contact with the relatively rotating polishing pad 22, and at the same time, the polishing liquid is transported to the polishing pad 22, and the polishing liquid is evenly distributed on the polishing pad 22 by centrifugal force, thereby passing through the surface of the pure silicon wafer 14. The relative motion with the polishing pad 22 flattens the surface of the pure silicon wafer 14 . At the same time, the real-time thickness of the pure silicon wafer 14 is tested by the distance difference between the first distance sensor 12 and the second distance sensor 21 , wherein the real-time thickness of the pure silicon wafer 14 The thickness of the rubber ring 18 , the thickness of the pure silicon wafer adsorption pad 13 and the real-time thickness of the polishing pad 22 are subtracted from the difference between the first distance sensor 12 and the second distance sensor 21 . The control unit 30 can adjust the pressure of the pressing mechanism 11 according to the target thickness of the pure silicon wafer 14 and the real-time thickness data of the pure silicon wafer 14 , so that the pure silicon wafer 14 can obtain a polished profile of the target thickness. .

As a non-limiting example, the pressure adjustment rule of the pressing mechanism may refer to the following formula: incoming thickness of pure silicon wafer - target thickness of pure silicon wafer = set pressure * removal coefficient; The incoming thickness refers to the initial thickness of pure silicon wafers.

In specific implementation, the removal coefficient can be obtained according to an empirical formula, that is, the linear relationship between the pressure of the polishing head 10 pressing on the upper surface of the pure silicon wafer 14 and the removal amount (thickness that is ground off), to obtain a fixed value (that is, the removal coefficient), when the incoming thickness of pure silicon wafers fluctuates, the pressure to be set can be calculated according to the formula. In this embodiment, the target thickness of the silicon wafer is, for example, 775500 nm. When the real-time thickness of the pure silicon wafer 14 detected by the distance sensor is 776000 nm, and the initial pressure of the pressing mechanism 11 is 0.008 MPa, the removal coefficient is 62500 nm/MPa, When the incoming thickness of pure silicon wafer is 776100nm, in the same polishing time, the pressure needs to be increased to 0.0096MPa to obtain the target thickness of pure silicon wafer.

The chemical mechanical polishing monitoring method provided in this embodiment is suitable for the front side final polishing (FP, final polish) process of pure silicon wafers, especially the final polishing process of 12-inch pure silicon wafers.

To sum up, in the chemical mechanical polishing system and the chemical mechanical polishing monitoring method provided by the embodiments of the present invention, the distance signal including the real-time thickness of the pure silicon wafer is detected by the distance sensor, and the detected distance signal including the pure silicon wafer is detected. The distance signal of the real-time thickness of the silicon wafer is transmitted to the control unit for calculation to obtain the real-time thickness of the pure silicon wafer in the final polishing process, and the real-time thickness data of the pure silicon wafer is fed back to the control unit. The target thickness and the real-time thickness data of the pure silicon wafer adjust the pressure of the pressing mechanism, so that the pure silicon wafer can obtain the target polishing shape. Wafer flatness control.

The above description is only a description of the preferred embodiments of the present invention, and does not limit the scope of the present invention. Any changes and modifications made by those of ordinary skill in the field of the present invention according to the above disclosure belong to the protection scope of the claims.

10: Polishing head 11: Pressurizing mechanism 12: The first distance sensor 13: Pure silicon adsorption pad 14: pure silicon wafer 15: The first rotation mechanism 16: Internal backplane 17: Snap ring 18: Rubber ring 20: Polishing table 21: Second distance sensor 22: polishing pad 23: Second rotating mechanism 30: Control unit S10, S20: Steps

1 is a schematic structural diagram of a chemical mechanical polishing system according to an embodiment of the present invention;

2 is a schematic top view of a polishing table according to an embodiment of the present invention;

3 is a schematic bottom view of a first distance sensor on a polishing head according to an embodiment of the present invention;

4 is a schematic bottom view of a plurality of first distance sensors on a polishing head according to an embodiment of the present invention;

5 is a schematic cross-sectional view of a polishing head according to an embodiment of the present invention;

6 is a schematic exploded cross-sectional view of a polishing head according to an embodiment of the present invention;

FIG. 7 is a schematic flowchart of a chemical mechanical polishing monitoring method according to an embodiment of the present invention.

none

10: Polishing head

11: Pressurizing mechanism

12: The first distance sensor

13: Pure silicon adsorption pad

14: pure silicon wafer

15: The first rotation mechanism

20: Polishing table

21: Second distance sensor

22: polishing pad

23: Second rotating mechanism

30: Control unit

Claims (10)

A chemical mechanical polishing system comprising: a polishing head for fixing a pure silicon wafer; a pressing mechanism, the pressing mechanism provides the pressing force of the polishing head on an upper surface of the pure silicon wafer; a distance sensor for detecting a distance signal including a real-time thickness of the pure silicon wafer, and transmitting the detected distance signal including the real-time thickness of the pure silicon wafer to a control unit performing a calculation to obtain the instant thickness of the pure silicon wafer; and the control unit for adjusting the pressure of the pressing mechanism according to a target thickness of the pure silicon wafer and the real-time thickness data of the pure silicon wafer; Wherein, the pressing mechanism is located above the polishing head and is fixedly connected with the polishing head, and the control unit is electrically connected to the pressing mechanism and the distance sensor respectively. The chemical mechanical polishing system of claim 1, wherein the distance sensor comprises a first distance sensor and a second distance sensor, the first distance sensor and the second distance sensor detect The distance signal including the real-time thickness of the pure silicon wafer is transmitted to the control unit, and the control unit calculates the real-time thickness of the pure silicon wafer through the distance difference between the first distance sensor and the second distance sensor thickness. The chemical mechanical polishing system of claim 2, wherein the number of the first distance sensors is multiple. The chemical mechanical polishing system according to claim 2, wherein an inner back plate is further provided below the polishing head, and a first rotation mechanism is further provided above the polishing head, and the first rotation mechanism connects the polishing head and the inner back plate plate, and drives the polishing head and the inner back plate to rotate. The chemical mechanical polishing system of claim 4, wherein the first distance sensor is fixed on the inner backplane. The chemical mechanical polishing system of claim 2, wherein the chemical mechanical polishing system for silicon wafers further comprises a polishing table, and a groove is provided on the polishing table. The chemical mechanical polishing system of claim 6, wherein the second distance sensor is fixed in the groove of the polishing table, and a surface of the second distance sensor and a surface of the polishing table flush. A chemical mechanical polishing monitoring method, comprising: Using a polishing head to press a pure silicon wafer onto a polishing pad to polish the pure silicon wafer; and A distance sensor detects a distance signal including a real-time thickness of the pure silicon wafer, and transmits the detected distance signal including the real-time thickness of the pure silicon wafer to a control unit for calculation, so as to obtain the pure silicon wafer. For the real-time thickness of the silicon wafer, the control unit adjusts the pressure provided by a pressing mechanism to the polishing head in real time according to a target thickness of the pure silicon wafer and the real-time thickness data of the pure silicon wafer. The chemical mechanical polishing monitoring method of claim 8, wherein the distance sensor comprises a first distance sensor and a second distance sensor, the first distance sensor and the second distance sensor The distance signal including the real-time thickness of the pure silicon wafer detected by the sensor is transmitted to the control unit, and the control unit detects the pure silicon wafer through the distance difference between the first distance sensor and the second distance sensor of this instant thickness. The chemical mechanical polishing monitoring method according to claim 9, wherein the thickness of a rubber ring, an adsorption pad and the polishing pad is subtracted from the distance difference between the first distance sensor and the second distance sensor, to obtain the real-time thickness of the pure silicon wafer for testing.

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