A wafer slide detection method

Abstract

This invention provides a method for detecting wafer slippage, comprising: providing a real-time topography control unit, the real-time topography control unit being adapted to detect the thickness of an object based on electromagnetic induction; using the real-time topography control unit to detect a test wafer and obtain the test grinding endpoint signal intensity of the test wafer; obtaining a first threshold based on the test grinding endpoint signal intensity; during the grinding process of the wafer, using the real-time topography control unit to detect the wafer and obtain a curve showing the change of the grinding signal intensity of the wafer over time; and determining that the wafer slippage has occurred when the grinding signal intensity of the wafer is less than the first threshold. The wafer slippage detection method of this invention provides timely judgment and high sensitivity.

Description

Technical Field

[0001] This invention relates to the field of semiconductor manufacturing technology, and more specifically to a method for detecting wafer slippage. Background Technology

[0002] With the gradual application of 5G, its advantages such as ultra-high speed, ultra-low latency, and ultra-high density have enabled the rapid development of emerging technologies such as the Internet of Things, artificial intelligence, and autonomous driving. This necessitates that chips used in 5G technology possess characteristics such as high efficiency and low power consumption. As semiconductor chip manufacturing technology advances, the role and requirements of chemical mechanical planarization (CMP) processes for 200mm and larger wafers in chip production are becoming increasingly stringent. From 0.13μm to 14nm and even 7nm and 5nm technologies, increasingly complex polishing materials and ever-increasing polishing requirements place increasingly stringent demands on the polishing process of copper CMP.

[0003] To precisely control the wafer grinding thickness, copper CMP processes typically use lasers or friction to receive or sense changes in light and force signals. However, this often results in the grinding end point (EP) being reached prematurely or delayed, leading to insufficient or excessive grinding, requiring repeated processing or rendering the wafer unusable. Furthermore, during grinding, the wafer is prone to splitting due to the pressure applied by the grinding head, the friction of the grinding pad, the fluid dynamics of the grinding slurry, and the rotational speed. Once the wafer slips outside the grinding head, it can easily collide with the machine, causing fragmentation. Existing laser sensing methods are limited by the laser detection position and exhibit a certain degree of hysteresis, failing to detect wafer splitting in a timely manner. Summary of the Invention

[0004] Therefore, the technical problem to be solved by the present invention is to overcome the inability of existing detection technologies to detect wafer slip defects in a timely manner, and thus provide a method for detecting wafer slip.

[0005] This invention provides a method for detecting wafer slippage, comprising: providing a real-time topography control unit, the real-time topography control unit being adapted to detect the thickness of an object based on electromagnetic induction; using the real-time topography control unit to detect a test wafer and obtain the test grinding endpoint signal intensity of the test wafer; obtaining a first threshold based on the test grinding endpoint signal intensity; during the grinding process of the wafer, using the real-time topography control unit to detect the wafer and obtain a curve showing the change of the grinding signal intensity of the wafer over time; and determining that the wafer slippage has occurred when the grinding signal intensity of the wafer is less than the first threshold.

[0006] Optionally, the test wafer includes a first test wafer to an Nth test wafer, where N is an integer greater than or equal to 2; the step of obtaining the test grinding endpoint signal intensity of the test wafer includes: obtaining the first test grinding endpoint signal intensity of the first test wafer to the Nth test grinding endpoint signal intensity of the Nth test wafer; based on the average grinding endpoint signal intensity and standard deviation of the first test grinding endpoint signal intensity to the Nth test grinding endpoint signal intensity; if the standard deviation is less than or equal to a second threshold, then the average grinding endpoint signal intensity is used as the test grinding endpoint signal intensity.

[0007] Optionally, the second threshold is 0 to 1.

[0008] Optional, N is an integer greater than or equal to 10.

[0009] Optionally, the first threshold is greater than or equal to 50% and less than or equal to 90% of the signal strength at the end of the test grinding.

[0010] Optionally, the real-time topography control unit includes an inductor coil and an electromagnetic signal sensor, wherein the inductor coil is adapted to generate a magnetic field and form eddy currents in a conductor within the magnetic field, and the electromagnetic signal sensor is adapted to detect the intensity of the eddy currents.

[0011] Optionally, after determining that the wafer has slipped, the grinding of the wafer is stopped.

[0012] The technical solution of this invention has the following advantages:

[0013] The wafer slip detection method of the present invention includes: providing a real-time topography control unit, the real-time topography control unit being adapted to detect the thickness of an object based on electromagnetic induction; using the real-time topography control unit to detect a test wafer and obtain the test grinding endpoint signal intensity of the test wafer; obtaining a first threshold based on the test grinding endpoint signal intensity; during the grinding process of the wafer, using the real-time topography control unit to detect the wafer and obtain the change curve of the grinding signal intensity of the wafer over time; when the grinding signal intensity of the wafer is less than the first threshold, determining that the wafer has slipped. Since the real-time topography control unit detects based on electromagnetic induction, the detection area is much larger than that of a laser, allowing for immediate feedback when slippage occurs, specifically a sudden drop in the grinding signal until it falls below the first threshold. The wafer slip detection method of the present invention provides timely judgment and high sensitivity.

[0014] Furthermore, the first threshold is greater than or equal to 50% and less than or equal to 90% of the signal strength at the end of the test grinding process. If the first threshold is greater than 90% of the signal strength at the end of the test grinding process, it is easily affected by signal noise, leading to misjudgment; if the first threshold is less than 50% of the signal strength at the end of the test grinding process, the sensitivity is greatly reduced, which is not conducive to stopping the grinding process in a timely manner. Attached Figure Description

[0015] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0016] Figure 1 This is a schematic flowchart of the wafer slip detection method in an embodiment of the present invention;

[0017] Figure 2 This is a schematic diagram of the change curve of the grinding signal intensity of the wafer over time under normal conditions in an embodiment of the present invention;

[0018] Figure 3 This is a schematic diagram of the change curve of the grinding signal intensity of the wafer under abnormal conditions over time in an embodiment of the present invention. Detailed Implementation

[0019] The technical solution of the present invention will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0020] In the description of this invention, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing the invention and for simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the invention. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0021] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0022] Furthermore, 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.

[0023] This invention provides a method for detecting wafer slippage, such as... Figure 1 As shown, it includes the following steps:

[0024] Step S1: Provide a real-time topography control unit, which is adapted to detect the thickness of an object based on electromagnetic induction.

[0025] Step S2: Use the real-time topography control unit to detect the test wafer and obtain the test grinding endpoint signal intensity of the test wafer;

[0026] Step S3: Obtain a first threshold based on the signal intensity at the end of the test grinding process;

[0027] Step S4: During the wafer grinding process, the real-time topography control unit is used to detect the wafer and obtain the change curve of the wafer grinding signal intensity over time.

[0028] Step S5: When the intensity of the grinding signal of the wafer is less than the first threshold, it is determined that the wafer has slipped.

[0029] Since the real-time topography control unit detects wafer slippage based on electromagnetic induction, the detection area is much larger than that of a laser, allowing for immediate feedback when slippage occurs. Specifically, the grinding signal intensity drops sharply until it falls below the first threshold. The wafer slippage detection method of this invention provides timely judgment, high sensitivity, and is easily automated.

[0030] Before the wafer is polished, the wafer includes: a wafer base structure; a barrier layer located on the surface of the wafer base structure; grooves in the barrier layer and a portion of the wafer base structure; and an initial metal interconnect layer located in the grooves and on the surface of the barrier layer. In the wafer polishing step, the initial metal interconnect layer is polished using a CMP process until the barrier layer is exposed, thereby forming a metal interconnect layer located in the grooves. The material of the metal interconnect layer includes copper. After the metal interconnect layer is formed, the barrier layer is removed.

[0031] In this embodiment, the test wafers include a first test wafer to an Nth test wafer, where N is an integer greater than or equal to 2. The step of obtaining the test grinding endpoint signal intensity of the test wafers includes: obtaining the first test grinding endpoint signal intensity of the first test wafer to the Nth test grinding endpoint signal intensity of the Nth test wafer; based on the average grinding endpoint signal intensity and standard deviation of the first test grinding endpoint signal intensity to the Nth test grinding endpoint signal intensity; if the standard deviation is less than or equal to a second threshold, then the average grinding endpoint signal intensity is used as the test grinding endpoint signal intensity. Since the wafer performance parameters obtained from different batches and different intermediate steps vary greatly, it is necessary to obtain the test grinding endpoint signal intensity of the test wafers to obtain a benchmark value for comparison. Specifically, when the selected test wafers have good consistency, reflected in a small standard deviation, the average grinding endpoint signal intensity can be directly used as the test grinding endpoint signal intensity. When the selected test wafers have poor consistency and the test data dispersion is large, reflected in a large standard deviation, the data with the largest deviation from the average can be removed, and the calculation of the average and standard deviation can be repeated until the standard deviation is less than the second threshold. The corresponding average value can then be used as the effective value for obtaining the test grinding endpoint signal intensity. In one specific embodiment, the second threshold is 0 to 1. In one embodiment, N is an integer greater than or equal to 10, which can obtain a more accurate test grinding endpoint signal intensity.

[0032] In this embodiment, the curve of the wafer's grinding signal intensity changing over time is obtained as follows: Figure 2 and Figure 3 As shown. Figure 2 The graph shows the variation of the wafer grinding signal intensity over time under normal conditions, where the horizontal axis represents time and the vertical axis represents signal intensity. Figure 2 As can be seen, the signal strength decreases first over time, indicating that the wafer is polished and thinned; then it reaches a stable state, and the signal strength corresponding to the stable state is the signal strength at the end of the polishing process. Figure 3 The graph shows the change in wafer grinding signal intensity over time under abnormal conditions, with a standard curve marked with a dashed line for comparison. The horizontal axis represents time, and the vertical axis represents signal intensity. Figure 3 As can be seen, the signal strength decreases over time, indicating that the wafer is being polished and thinned. Then, before the signal strength reaches the end of the polishing process, the signal strength drops sharply until it falls below the first threshold, indicating an anomaly, specifically that wafer slippage has occurred.

[0033] In one embodiment, the first threshold is greater than or equal to 50% and less than or equal to 90% of the signal strength at the end of the test grinding. If the first threshold is greater than 90% of the signal strength at the end of the test grinding, it is easily affected by signal noise, leading to misjudgment; if the first threshold is less than 50% of the signal strength at the end of the test grinding, the sensitivity is greatly reduced, which is not conducive to stopping the grinding equipment in a timely manner.

[0034] In this embodiment, the real-time topography control unit includes an inductor coil and an electromagnetic signal sensor. The inductor coil is adapted to generate a magnetic field and form eddy currents in a conductor within the magnetic field. The electromagnetic signal sensor is adapted to detect the intensity of the eddy currents. Since the metal induces eddy currents in a changing electric field, and the greater the film thickness, the stronger the signal generated by the eddy currents, the degree of polishing can be determined based on the magnitude of the detected eddy current signal. The original electrical signal can be converted into thickness information using a simple linear function. The parameters of the linear function need to be obtained beforehand by calibrating the real-time topography control unit with a wafer of standard thickness.

[0035] In this embodiment, grinding of the wafer is stopped after it is determined that wafer slippage has occurred. In a specific embodiment, a slippage alarm device may also be added.

[0036] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. A method for detecting wafer slippage, characterized in that, The application relates to a real-time topography control unit, a method for detecting a wafer and a method for detecting a wafer. The real-time topography control unit comprises an inductive coil and an electromagnetic signal sensor, the inductive coil is used for generating a magnetic field and forming an eddy current in a conductor in the magnetic field, and the electromagnetic signal sensor is used for detecting the intensity of the eddy current. The test wafers comprise a first test wafer to an Nth test wafer, N is an integer greater than or equal to 10, the step of obtaining the test end-of-grinding signal intensity of the test wafers comprises the steps that a first test end-of-grinding signal intensity of the first test wafer to an Nth test end-of-grinding signal intensity of the Nth test wafer are obtained, the average end-of-grinding signal intensity and the standard deviation of the first test end-of-grinding signal intensity to the Nth test end-of-grinding signal intensity are obtained, if the standard deviation is less than or equal to a second threshold value, the average end-of-grinding signal intensity is taken as the test end-of-grinding signal intensity, if the standard deviation is greater than the second threshold value, the data with the largest deviation from the average value is removed, and then the average value and the standard deviation are calculated repeatedly until the standard deviation is less than the second threshold value, and the average end-of-grinding signal intensity at this time is taken as the test end-of-grinding signal intensity, and the second threshold value is 0-1. The first threshold value is greater than or equal to 50% of the test end-of-grinding signal intensity and less than or equal to 90% of the test end-of-grinding signal intensity. During the grinding of the wafer, the real-time topography control unit is used to detect the wafer to obtain the change curve of the grinding signal intensity of the wafer with time. When the grinding signal intensity of the wafer is less than the first threshold value, it is judged that the wafer has a slip sheet. After it is judged that the wafer has a slip sheet, the grinding of the wafer is stopped.

2. The method of claim 1, wherein ​

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