Force measurement system

Force measurement system is provided. It includes: a grinding arm and a stressed layer, the stressed layer being configured to bear a force from the grinding arm; a base and a plurality of elastic bodies, the elastic bodies being fixed between the stressed layer and the base; a deformation sensor, configured to detect deformation of the elastic bodies; and an analysis device, configured to obtain the force on the stressed layer according to a detection result of the deformation sensor and an elastic constant of the elastic body.

TECHNICAL FIELD

Embodiments of the present disclosure relate to the field of semiconductors, and in particular to a force measurement system.

BACKGROUND

The chemical mechanical polishing process is to conduct a grinding operation under chemical and mechanical action. During the grinding process, the grinding amount is required to be controlled. The key elements involved in this process include controlling the down force of a grinding arm. The down force will directly influence a grinding rate and the degree of particle aggregation during the grinding process. Therefore, precise control over down force is particularly important.

SUMMARY

Various embodiments of the present disclosure provide a force measurement system, which is beneficial to detecting the balance of a force applied to a stressed layer by a grinding arm.

In order to solve the above problem, an embodiment of the present application provides a force measurement system includes: the grinding arm and a stressed layer, the stressed layer being configured to bear a force from the grinding arm; a base and a plurality of elastic bodies, the elastic bodies being fixed between the stressed layer and the base; a deformation sensor, configured to detect deformation of the elastic bodies; and an analysis device, configured to measure the force on the stressed layer according to a detection result of the deformation sensor and an elastic constant of the elastic bodies.

DESCRIPTION OF EMBODIMENTS

In order to make the objectives, technical solutions, and advantages of the embodiments of the present disclosure more clear, various embodiments of the present disclosures will be detailed below in combination with the accompanying drawings. However, a person of ordinary skill in the art can understand that in each embodiment of the present disclosure, many technical details are provided for readers to better understand the present disclosure. However, even if these technical details are not provided and based on variations and modifications of the following embodiments, the technical solutions sought for protection in the present disclosure can also be implemented.

FIG.1is a schematic structural diagram of a force measurement system.

Referring toFIG.1, a load cell12is installed on a grinding arm11. After a downforce is set on a machine, the grinding arm11drives the load cell12to act on a stressed device13, and the stressed device13makes a feedback to the load cell12by way of a counterforce, so that the load cell12obtains the current force of the grinding arm11.

In a prior art, before the load cell12is installed, a grinding disk required in an actual grinding process and installed on the grinding arm11needs to be removed first, and then the load cell12is installed on the grinding arm11by means of magnetic attraction or the like. In this way, the force acquired by the load cell12only includes a pressure stress set by the machine and applied by the grinding arm11, but does not include a self-weight of the grinding disk. Therefore, the force acquired by the load cell12is not a force acting on a grinding object during the actual grinding process, and accordingly, the machine cannot accurately monitor and calibrate the force acting on the grinding object during the actual grinding process, according to a value obtained by the load cell12.

Moreover, in order to ensure the effective transmission of data of the load cell12, a signal line of the load cell12needs to be connected to an analysis device. Since the load cell12is fixed on the grinding arm11and the grinding arm11needs to move up and down during the actual grinding step, the signal line will move up and down with the grinding arm11, and the up and down movement may cause internal damage, poor contact or other problems to the signal line, which further will cause deviations in the detection data due to the internal damage and the poor contact.

In addition, the current load cell12usually only records a maximum counterforce fed back by the stressed device13as the force applied by the grinding arm11, rather than showing the distribution of the force applied by the grinding arm11to the stressed device13. In extreme cases, there may be a certain inclination angle between the grinding disk and a grinding disk of the grinding object. In this case, a predetermined grinding result cannot be obtained even if the sum of the force provided by the grinding arm11and a self-weight of the grinding disk is equal to a predetermined grinding force.

To solve the above problem, an embodiment of the present disclosure provides a force measurement system. A plurality of elastic bodies are arranged between the stressed layer and the base, and forces applied by the grinding arm to different positions on the stressed layer are measured by the plurality of elastic bodies; in this way, the balance of the force applied by the grinding arm can be further represented according to the forces at different positions on the stressed layer.

In order to make the objectives, technical solutions, and advantages of the embodiments of the present disclosure more clear, various embodiments of the present disclosures will be detailed below in combination with the accompanying drawings. However, a person of ordinary skill in the art can understand that in each embodiment of the present disclosure, many technical details are provided for readers to better understand the present disclosure. However, even if these technical details are not provided and based on variations and modifications of the following embodiments, the technical solutions sought for protection in the present disclosure can also be implemented.

FIG.2is a schematic structural diagram of a force measurement system according to an embodiment of the present disclosure.

Referring toFIG.2, the force measurement system includes: a grinding arm21and a stressed layer30, the stressed layer30being configured to bear a force applied to the grinding arm21; a base31and a plurality of elastic bodies32, the plurality of elastic bodies32being fixed between the stressed layer30and the base31; a deformation sensor33configured to detect deformation of the elastic bodies32; and an analysis device (not shown) configured to obtain a force acting on the stressed layer30according to a detection result of the deformation sensor33and an elastic coefficient of the elastic bodies32.

In this embodiment, the force measurement system further includes a grinding disk20fixed on the grinding arm21, and the grinding arm21applies a force to the stressed layer30through the grinding disk20. Since the elastic bodies32are installed between the stressed layer30and the base31, the grinding disk20can be installed on the grinding arm21. The grinding arm21can drive the grinding disk20to apply a force to the stressed layer30together, and the elastic bodies32can measure the sum of the force applied by the grinding arm21and the self-weight of the grinding disk20. In this way, the measurement result of the elastic bodies32are closer to a force on the grinding object during the actual grinding process, thus ensuring that the grinding object has a better grinding result during the actual grinding process.

In this embodiment, a signal line of the deformation sensor33is fixed by the base31. Since the base31does not move during the grinding process, fixing the signal line by the base31can favorably ensure that the signal line has good stability and excellent performance, thereby ensuring that the deformation sensor33can accurately obtain the deformation of the elastic bodies32, and moreover ensuring that the analysis device can accurately obtain the sum of the force applied by the grinding arm21and the self-weight of the grinding disk20according to the deformation of the elastic bodies32.

In this embodiment, the actual designation of the stressed layer varies according to application scenarios. Specifically, in the actual polishing process, the stressed layer30is generally configured as a polishing pad, and the polishing object is generally configured as a wafer; in a test process of the force measurement system, the stressed layer30can also serve as a stressed surface of a test structure; that is, the test structure is used to simulate a polishing pad to ensure the accuracy of parameters of the force measurement system used in the actual grinding process.

Hereinafter, a description is provided by an example where the stressed layer30serves as a stressed surface of the test structure. Details are specified as follows:

In this embodiment, the number of elastic bodies32is greater than or equal to three, for example four. A larger number of elastic bodies32can detect forces at more positions on the surface of the stressed layer30. Since at least three points can define a plane, the number of elastic bodies32needs to be greater than or equal to three, and then the analysis device can calculate a stress condition on the entire surface of the stressed layer30to represent a stress condition on the stressed surface of the grinding object during the actual grinding process, and to determine the stress balance of the grinding object.

When the number of elastic bodies32is less than three, the analysis device can only obtain a stress condition on a straight path or in a local point-shaped region on the surface of the stressed layer30; in addition, the stress balance of the grinding object can be represented by a maximum force difference between different positions on the surface of the stressed layer30or by parameters such as the variance of force on the stressed surface.

When the number of elastic bodies32is three, the elastic bodies32can be distributed in a triangular shape to better support the stressed layer30; in this embodiment, the number of elastic bodies32is four or more, and the four elastic bodies32define a rectangle to stably support the stressed layer30.

In this embodiment, the stressed layer30has a center of stress. In a direction parallel to a top surface of the stressed layer30, there are at least two of the elastic bodies32having the same distance from the center of stress. The center of stress refers to the center of the stressed surface of the stressed layer30. Ideally, stresses at any two positions on the stressed surface are equal; and when the force of the grinding arm21is mainly concentrated on the center of stress, stresses at different positions on the stressed surface should follow the principle of equal distance and equal stress, that is, the stresses at different positions having equal distance from the center of stress are the same. Therefore, the stress balance of the stressed layer30can be obtained by comparing the deformations of the elastic bodies32at different positions with the same distance from the center of stress.

At least the following two cases may lead to a poor stress balance of the stressed layer30. Case 1: when applying a force to the stressed layer30, the grinding arm21shifts, resulting in that the center of the actual stressed surface of the stressed layer30is not a predetermined center of stress. Case 2: there is a certain inclination angle between the grinding disk20and the stressed layer30, resulting in that the forces applied by the grinding arm21and by the grinding disk20to the stressed layer30are concentrated on one side of the center of stress.

When the balance of force on the stressed layer30does not meet the predetermined requirements, it can be considered that in the actual grinding process, the stress balance of the grinding object may not meet the predetermined requirements, so the machine, the grinding arm21or the grinding disk20need to be calibrated according to parameters fed back by the deformation sensor33.

In this embodiment, a groove301is formed in the stressed layer30. The groove301is configured to receive a calibration weight. A center of the groove301serves as the center of stress, so as to prevent a case where the center of gravity of the stressed layer30shifts due to the arrangement of the groove301. When the stressed layer30is under a force, a calibration weight of any weight can be placed anywhere in the groove301to control the stressed layer30to have a good stress balance, and to cause the stressed layer30to bear a predetermined force. Thus, the force and position of the grinding arm21and the weight and angle of the grinding disk20can be calibrated according to the position and weight of the calibration weight, so that the sum of the force set on the machine and the self-weight of the grinding disk20is equal to a grinding force required for the grinding object; in this way, a case where the actual force is greater than or less than the required grinding force can be avoided, and the stressed layer30can achieve a relatively high force balance.

In addition, it can be seen from the above that the balance of the force on the stressed layer30is also reflected in whether stresses at different positions having different distances from the center of stress are equal. When the stresses are not equal, it can be considered that the grinding disk20and the surface of the stressed layer30are not in good fit, resulting in that no stress exists in a partial surface of the stressed layer30.

In this embodiment, in a direction perpendicular to the surface of the stressed layer30, orthographic projections of the elastic bodies32are entirely coincident with an orthographic projection of the grinding disk20. In this way, when performing stress calculation, the analysis device has a larger number of data anchor points that can reflect the true stress condition, which is beneficial to more accurately calculating the stress condition in other regions of the stressed surface.

In this embodiment, a diameter of the groove301is less than a diameter of the grinding disk20, and the groove301is only configured to receive the calibration weight; in other embodiments, the diameter of the groove is greater than the diameter of the grinding disk, the grinding disk and the calibration weight can be put into the groove together, and in the direction perpendicular to the surface of the stressed layer, the orthographic projections of at least part of the elastic bodies are outside the orthographic projection of the grinding disk. The calibration weight can be either a standard weight or a weight customized according to actual needs.

In this embodiment, a center axis of one of the elastic bodies32passes through the center of stress, that is, the elastic bodies32are also located between the center of stress and the base31.

When the analysis device calculates the stress condition on the stressed layer30, the stress condition at the center of stress can be further obtained, and the stress condition between the center of stress and an edge of stress can be calculated more effectively to improve the accuracy of the calculation result.

In this embodiment, the analysis device is further configured to calibrate the plane position and orientation of the grinding arm21according to difference of deformation between the elastic bodies32. By calibrating the plane position of the grinding arm21, it can be ensured that in the direction perpendicular to the surface of the stressed layer30, the center of a surface, facing the stressed layer30, of the grinding disk20is in the same axis as the predetermined center of stress; by calibrating the orientation of the grinding arm21, it can be ensured that the grinding disk20and the surface of the stressed layer30are in good fit, and a case where an inclination angle between the grinding disk20and the surface of the stressed layer30goes beyond an allowable error range can be avoided, thus ensuring that the actual stressed surface of the stressed layer30has a good stress balance.

In this embodiment, the plurality of elastic bodies32are of the same specification; specifically the plurality of elastic bodies32are the same in length and elastic coefficient. In this way, it is beneficial to ensuring that under the same force, different elastic bodies32have the same deformation and the same rebound force, so as to ensure that the grinding disk20can grind different regions of the grinding object to the same degree, thus avoiding difference in wear caused by different pressing forces.

The elastic bodies32may be configured as a spring with a maximum elastic force of 15N, the deformation sensor33may be configured as a laser sensor, and the maximum elastic force of the elastic bodies32may be calibrated according to the requirements of the grinding object and the specific grinding process.

In this embodiment, before the grinding arm21applies a force to the stressed layer30, a measurement value of the deformation sensor33needs to be calibrated to zero, thereby avoiding an adverse effect of the self-weight of the stressed layer30on the detection result.

In this embodiment, a plurality of elastic bodies are arranged between the stressed layer and the base, and forces applied by the grinding arm to different positions on the stressed layer are measured by the plurality of elastic bodies; moreover, the balance of force applied by the grinding arm can be further represented according to the forces at different positions on the stressed layer.

The ordinary skills in the art can understand that the implementations described above are particular embodiments for implementing the present application. In practical uses, various changes in forms and details may be made to the implementations without departing from the spirit and scope of the present application. Any person skilled in the art may make their own changes and modifications without departing from the spirit and scope of the present disclosure. Therefore, the protection scope of the present disclosure shall be subject to the protection scope of the claims.