A relative trajectory tracking method between sensor and wafer

Abstract

The present invention provides a method for tracking the relative trajectory of a sensor and a wafer, belonging to the technical field of CMP equipment, and comprising the following steps: calculating the distance between point A and point B based on known conditions; at time T1, forming a first circle with the current position of point A as the center and the current length of point A and point B as the radius, wherein the first circle and the edge of the wafer generate a first intersection point; repeating the intersection point acquisition step until the sensor is separated from the wafer, obtaining a plurality of intersection points; and as the sensor sweeps across the wafer, curve fitting is performed on the plurality of intersection points to obtain the arc swept by the sensor on the wafer. The method for tracking the relative trajectory of a sensor and a wafer provided by the present invention can obtain the distance of the sensor relative to the center of the polishing head, the arc swept by the sensor across the wafer, and the real-time position of the sensor relative to the wafer in real time. The polishing condition of the wafer at that time can be determined from the data transmitted by the sensor, and the pressure of the polishing head can be adjusted in real time.

Description

Technical Field

[0001] The present invention relates to the technical field of CMP equipment, and in particular to a method for tracking relative trajectories between a sensor and a wafer. Background Art

[0002] Chemical Mechanical Planarization (CMP) is the most effective global planarization method available today. It leverages the synergistic effect of chemical etching and mechanical grinding to effectively achieve both local and global wafer flatness, and has been widely used in VLSI manufacturing.

[0003] When processing wafers, CMP equipment typically uses an endpoint detection system to monitor whether the metal material on the wafer has been polished. This endpoint detection system typically uses a sensor mounted on the polishing pad to monitor the wafer to ensure the polishing effect. However, if the polishing head pressure remains constant, the wafer will initially be thinner in the center and thicker at the edges, while later in the polishing process, the wafer will be thicker in the center and thinner at the edges. If the polishing head pressure is not adjusted, the wafer's topography will deviate from the target. To adjust the polishing head pressure in real time based on the wafer's polishing condition, the sensor's real-time position relative to the wafer is required. However, since the sensor rotates with the polishing pad, and the wafer also undergoes complex movements with the polishing head, the sensor's position relative to the wafer cannot be accurately determined. Summary of the Invention

[0004] Therefore, the technical problem to be solved by the present invention is to overcome the defect in the prior art that the CMP equipment cannot accurately obtain the relative position of the sensor and the wafer when grinding the wafer, thereby providing a method for tracking the relative trajectory of the sensor and the wafer.

[0005] To solve the above technical problems, the present invention provides a method for tracking the relative trajectory of a sensor and a wafer, comprising the following steps:

[0006] Get the distance L1 between the polishing disc center O1 and the polishing head revolution center O2;

[0007] Get the distance L2 between the polishing head revolution center point O2 and the polishing head center point A;

[0008] Get the distance L3 between the sensor position point B and the polishing disc center point O1;

[0009] Obtain the polishing disc's rotation speed Rpm1, and calculate the arc length displacement S1 of the polishing head's rotation center within the time (T2-T1) according to the polishing head motion formula;

[0010] Get the size of angle FO1O2, including: O1 as the pole and the line connecting O1O2 as the polar axis. According to the radian angle formula, the radian angle of angle FO1B is:

[0011] ∠FO1B=2*π / 60*Rpm1*(T2-T1)

[0012] The time when the sensor scans the wafer is T1, and the time when the sensor uploads data is T2. At T1, the radius of the sensor on the polishing plate is O1F, and at T2, the center of the polishing head is point A.

[0013] Calculate the radian angle of BO1O2 as:

[0014] ∠BO1O2=∠FO1O2-∠FO1B

[0015] According to the radian angle, calculate the polar coordinates of point B as (L3, ∠BO1O2);

[0016] The radian angle of angle AO2O1 is calculated as:

[0017] ∠AO2O1=S1 / L2;

[0018] According to the triangle cosine theorem, the length of AO1 is calculated as:

[0019]

[0020] The radian angle of angle AO1O2 is calculated as:

[0021] ∠AO1O2=arcsin(L2*sin(∠AO2O1) / AO1);

[0022] Calculate the polar coordinates of point A as (AO1, ∠AO1O2);

[0023] Convert the polar coordinates of points A and B into the coordinates of the rectangular coordinate system with O1 as the origin:

[0024] A(AO1*cos(∠AO1O2),AO1*sin(∠AO1O2));

[0025] B(L3*cos(∠BO1O2), L3*sin(∠BO1O2));

[0026] The distance between points AB can be calculated based on the two-point distance formula, and the distance between the sensor and the polishing head rotation center can be calculated as:

[0027]

[0028] At time T1, a first circle is formed with the current position of point A as the center and the current length of AB as the radius, and the first circle intersects the edge of the wafer at the first point.

[0029] After a preset time has passed, a second circle is formed with the current position of point A as the center and the current length of AB as the radius, and the second circle and the first circle have a second intersection;

[0030] Intersection point acquisition step: After the preset time has passed again, a third circle is formed with the current position of point A as the center and the current length of AB as the radius, and the third circle and the second circle have a third intersection point;

[0031] Repeat the intersection point acquisition step until the sensor is away from the wafer and a number of intersection points are obtained;

[0032] When the sensor scans across the wafer, a curve is fitted through several intersection points to obtain the arc that the sensor scans across the wafer.

[0033] Optionally, the preset time is 1ms.

[0034] Optionally, the polishing head performs a customized displacement motion on the surface of the polishing disk.

[0035] Optionally, a controller is further included, and the controller is communicatively connected to the sensor.

[0036] Optionally, a pressure regulating device is further included, connected to the polishing head, and the pressure regulating device is communicatively connected to the controller.

[0037] Optionally, a shaft body is further included, which is arranged on one side of the polishing disc, and the polishing head is rotatably mounted on the shaft body through a support rod.

[0038] Optionally, the rotation direction of the polishing disc is the same as the revolution direction of the polishing head.

[0039] The technical solution of the present invention has the following advantages:

[0040] 1. The method for tracking the relative trajectory of the sensor and the wafer provided by the present invention can obtain the distance between the sensor and the center of the polishing head in real time when the wafer is being polished, and then obtain the arc of the sensor when it sweeps across the wafer, and obtain the real-time position of the sensor relative to the wafer. The polishing status of the wafer at this time can be known from the data transmitted by the sensor, and the pressure of the polishing head can be adjusted to ensure the polishing effect of the wafer.

[0041] 2. The method for tracking the relative trajectory of the sensor and the wafer provided by the present invention has a preset time of 1ms, and the interval time is extremely short, which can increase the number of times the sensor uploads data and improve the accuracy of measuring the real-time position of the sensor relative to the wafer.

[0042] 3. The present invention provides a method for tracking the relative trajectory of the sensor and the wafer. The polishing head is connected to a pressure regulating device. The polishing status of the wafer can be known through the feedback of the sensor. The pressure can be adjusted in real time during the polishing process through the pressure regulating device to make the wafer grinding more uniform and avoid the phenomenon of uneven grinding at the middle and edge positions of the wafer during the grinding process. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] In order to more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the specific embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0044] Figure 1 A schematic diagram of the positional relationship between the polishing plate and the polishing head in the sensor and wafer relative trajectory tracking method provided by the present invention;

[0045] Figure 2 Schematic diagram of the relative position of the sensor and the wafer at time T2.

[0046] Description of reference numerals:

[0047] 1. Sensor; 2. Polishing disc; 3. Polishing head; 4. Support rod; 5. Shaft. DETAILED DESCRIPTION

[0048] The technical solution of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making any creative efforts shall fall within the scope of protection of the present invention.

[0049] In the description of the present invention, it should be noted that the terms "center", "up", "down", "left", "right", "vertical", "horizontal", "inside", "outside", etc., indicating directions or positional relationships, are based on the directions or positional relationships shown in the accompanying drawings. They are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific direction, be constructed and operated in a specific direction. Therefore, they cannot be understood as limiting the present invention.

[0050] In the description of the present invention, it should be noted that, unless otherwise expressly specified or limited, the terms "mounted," "connected," and "connected" should be understood in a broad sense. For example, they may refer to fixed, detachable, or integral connections; mechanical or electrical connections; direct or indirect connections through an intermediate medium; and internal communication between two components. Those skilled in the art will understand the specific meanings of the above terms in the present invention based on the specific circumstances.

[0051] In addition, the technical features involved in the different embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0052] This embodiment provides a specific implementation method of the relative trajectory tracking method between the sensor and the wafer, such as Figure 1 and Figure 2 As shown, the following steps are included:

[0053] Obtain the distance L1 between the center point O1 of the polishing plate 2 and the revolution center point O2 of the polishing head 3;

[0054] Obtain the distance L2 between the revolution center O2 of the polishing head 3 and the center A of the polishing head 3;

[0055] Obtain the distance L3 between the position B of the sensor 1 and the center O1 of the polishing plate 2;

[0056] Obtain the rotation speed Rpm1 of the polishing disk 2, and calculate the arc length displacement S1 of the rotation center of the polishing head 3 within the time (T2-T1) according to the motion formula of the polishing head 3;

[0057] Get the size of angle FO1O2, including: O1 as the pole and the line connecting O1O2 as the polar axis. According to the radian angle formula, the radian angle of angle FO1B is:

[0058] ∠FO1B=2*π / 60*Rpm1*(T2-T1)

[0059] The time when sensor 1 scans the wafer is T1, the time when sensor 1 uploads data is T2, the radius of sensor 1 on polishing plate 2 at T1 is O1F, and the center of polishing head 3 is point A at T2;

[0060] Calculate the radian angle of BO1O2 as:

[0061] ∠BO1O2=∠FO1O2-∠FO1B

[0062] According to the radian angle, calculate the polar coordinates of point B as (L3, ∠BO1O2);

[0063] The radian angle of angle AO2O1 is calculated as:

[0064] ∠AO2O1=S1 / L2;

[0065] According to the triangle cosine theorem, the length of AO1 is calculated as:

[0066]

[0067] The radian angle of angle AO1O2 is calculated as:

[0068] ∠AO1O2=arcsin(L2*sin(∠AO2O1) / AO1);

[0069] Calculate the polar coordinates of point A as (AO1, ∠AO1O2);

[0070] Convert the polar coordinates of points A and B into the coordinates of the rectangular coordinate system with O1 as the origin:

[0071] A(AO1*cos(∠AO1O2),AO1*sin(∠AO1O2));

[0072] B(L3*cos(∠BO1O2), L3*sin(∠BO1O2));

[0073] The distance between points AB can be calculated based on the two-point distance formula. The distance between sensor 1 and the rotation center of polishing head 3 is calculated as:

[0074]

[0075] At time T1, a first circle is formed with the current position of point A as the center and the current length of AB as the radius, and the first circle intersects the edge of the wafer at the first point.

[0076] After a preset time has passed, a second circle is formed with the current position of point A as the center and the current length of AB as the radius, and the second circle and the first circle have a second intersection;

[0077] Intersection point acquisition step: After the preset time has passed again, a third circle is formed with the current position of point A as the center and the current length of AB as the radius, and the third circle and the second circle have a third intersection point;

[0078] Repeat the intersection point acquisition step until the sensor is away from the wafer and a number of intersection points are obtained;

[0079] When the sensor 1 scans across the wafer, a curve line scanned by the sensor 1 on the wafer is obtained by performing curve fitting on a number of intersection points.

[0080] In this embodiment, the polishing head 3 is rotatably mounted on the shaft 5 via a support rod 4. The polishing head 3 carries the wafer on the polishing plate 2 for grinding. The direction of rotation of the polishing plate 2 is the same as the direction of revolution of the polishing head 3, wherein the polishing head 3 rotates with the wafer. Based on the arc obtained when the sensor 1 sweeps across the wafer, the real-time position of the sensor 1 relative to the wafer can be obtained. The data transmitted by the sensor 1 can be used to determine the grinding condition of the wafer at the detected part, and the pressure of the polishing head 3 can be adjusted to ensure the polishing effect of the wafer.

[0081] As an alternative embodiment, the polishing head 3 may not rotate.

[0082] Specifically, O1F is a ray formed by the sensor 1 at time T1 and the center O1 of the polishing disk 2. The size of the angle FO1O2 can be obtained according to the position of the polishing disk 2 when it is stopped and the rotation speed information of the polishing disk 2.

[0083] In this embodiment, the preset time is set to 1ms, which is a very short interval. This can increase the number of times the sensor 1 uploads data and improve the accuracy of measuring the real-time position of the sensor 1 relative to the wafer. The preset time can also be changed according to the actual polishing situation and is not limited to being set to 1ms.

[0084] In this embodiment, the support rod 4 connected to the polishing head 3 is a telescopic rod, such as a cylinder. The tail of the cylinder is rotatably mounted on the shaft 5, and the driving end of the cylinder is connected to the polishing head 3. A motor is installed in the shaft 5. The motor can drive the support rod 4 to rotate or swing, and then the support rod 4 drives the polishing head 3 to rotate or swing, so that the polishing head 3 can rotate or swing on the polishing disk 2 when grinding the wafer. Through the telescopic movement of the cylinder, the polishing head 3 can perform more complex movements on the polishing disk 2, such as reciprocating contraction while swinging, forming a motion curve similar to the sin function or cos function graph in trigonometric functions.

[0085] As an alternative embodiment, the support rod 4 can also be composed of an outer tube and an inner tube, the inner tube is slidably installed in the outer tube, the inner tube is connected to the polishing head 3, and the outer tube is rotatably installed on the shaft 5.

[0086] As an alternative embodiment, the coordination between the extension and contraction and the swing of the support rod 4 can also form motions of other curves, not limited to the curves in the sin function or cos function graphs.

[0087] In this embodiment, a pressure regulating device is connected to the polishing head 3 to adjust the pressure between the wafer and the polishing plate 2. Feedback from the sensor 1 indicates the polishing status of the wafer. The pressure regulating device can be used to adjust the pressure in real time during the polishing process, ensuring more uniform polishing of the wafer and avoiding uneven polishing between the center and edge of the wafer during the polishing process.

[0088] Among them, the pressure regulating device can be a cylinder, which is vertically installed in the polishing head 3, with the driving end of the cylinder facing downward. The driving end of the cylinder is connected to the wafer stage, and the wafer is adsorbed or installed on the wafer stage. By adjusting the distance between the wafer stage and the polishing disk 2, the pressure between the wafer and the polishing disk 2 is adjusted.

[0089] In this embodiment, a controller is also provided, and the servo motor for controlling the rotation of the polishing disk 2, the sensor 1, the pressure regulating device, the motor or cylinder for adjusting the length of the support rod 4, and the motor for driving the support rod 4 to rotate are all communicated with the controller. The operator inputs known information into the controller in advance, processes the information according to the information transmitted by the sensor 1, and finally feeds back the signal to the pressure regulating device, so that the pressure regulating device adjusts the pressure between the polishing head 3 and the polishing disk 2.

[0090] Specifically, by using a servo motor to control the rotation of the polishing disc 2, the position of the polishing disc 2 when it stops rotating and the position when it starts rotating can be accurately known; and since the polishing disc 2 rotates in a circle, the central angle of the circle is also easy to calculate.

[0091] Obviously, the above embodiments are merely examples for clarity of explanation and are not intended to limit the implementation methods. Those skilled in the art will readily appreciate that other variations or modifications based on the above descriptions are possible. It is not necessary and impossible to enumerate all implementation methods here. Obvious variations or modifications arising therefrom remain within the scope of protection of the present invention.

Claims

1. A method for tracking relative trajectories between a sensor and a wafer, characterized in that: The following steps are involved: Obtaining the distance L1 between the center point O1 of the polishing plate (2) and the revolution center point O2 of the polishing head (3); Obtaining the distance L2 between the revolution center O2 of the polishing head (3) and the center A of the polishing head (3); Obtaining the distance L3 between the position B of the sensor (1) and the center O1 of the polishing plate (2); Obtaining the rotation speed Rpm1 of the polishing disc (2), and obtaining the arc length displacement S1 of the rotation center of the polishing head (3) within the time (T2-T1) according to the motion formula of the polishing head (3); Get the size of angle FO1O2, including: O1 as the pole and the line connecting O1O2 as the polar axis. According to the radian angle formula, the radian angle of angle FO1B is: ∠FO1B=2*π / 60*Rpm1*(T2-T1) The time when the sensor (1) scans the wafer is T1, the time when the sensor (1) uploads data is T2, the radius of the sensor (1) on the polishing disk at time T1 is O1F, and the center of the polishing head (3) at time T2 is point A; Calculate the radian angle of BO1O2 as: ∠BO1O2=∠FO1O2-∠FO1B According to the radian angle, calculate the polar coordinates of point B as (L3, ∠BO1O2); The radian angle of angle AO2O1 is calculated as: ∠AO2O1=S1 / L2; According to the triangle cosine theorem, the length of AO1 is calculated as: The radian angle of angle AO1O2 is calculated as: ∠AO1O2=arcsin(L2*sin(∠AO2O1) / AO1); Calculate the polar coordinates of point A as (AO1, ∠AO1O2); Convert the polar coordinates of points A and B into the coordinates of the rectangular coordinate system with O1 as the origin: A(AO1*cos(∠AO1O2),AO1*sin(∠AO1O2)); B(L3*cos(∠BO1O2), L3*sin(∠BO1O2)); The distance between points AB can be calculated based on the two-point distance formula, and the distance between the sensor and the polishing head rotation center can be calculated as: At time T1, a first circle is formed with the current position of point A as the center and the current length of AB as the radius, and the first circle intersects the edge of the wafer at the first point. After a preset time has passed, a second circle is formed with the current position of point A as the center and the current length of AB as the radius, and the second circle and the first circle have a second intersection; Intersection point acquisition step: After the preset time has passed again, a third circle is formed with the current position of point A as the center and the current length of AB as the radius, and the third circle and the second circle have a third intersection point; Repeating the intersection point acquisition step until the sensor (1) is away from the wafer and a plurality of intersection points are obtained; When the sensor (1) scans the wafer, a curve line scanned by the sensor (1) on the wafer is obtained by curve fitting a plurality of intersection points; The tracking method further comprises a controller, which is in communication connection with the sensor (1); the tracking method further comprises a pressure regulating device, which is connected with the polishing head (3), and the pressure regulating device is in communication connection with the controller.

2. The method for tracking the relative trajectory of the sensor and the wafer according to claim 1, wherein: The preset time is 1ms.

3. The method for tracking the relative trajectory between the sensor and the wafer according to claim 1, wherein: The polishing head (3) performs a customized displacement motion on the surface of the polishing disc (2).

4. The method for tracking the relative trajectory between the sensor and the wafer according to claim 1, wherein: It also includes a shaft (5) arranged on one side of the polishing disc (2), and the polishing head (3) is rotatably mounted on the shaft (5) via a support rod (4).

5. The method for tracking the relative trajectory between the sensor and the wafer according to claim 1, wherein: The rotation direction of the polishing disc (2) is the same as the revolution direction of the polishing head (3).

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