A method and device for controlling the distance between a probe of a detector and a wafer

Abstract

The present invention provides a method and device for controlling the distance between a probe of a detector and a wafer, wherein the method comprises: before placing a wafer on a chuck of the detector, applying an AC signal to the chuck so that the chuck generates a disturbance signal, thereby generating a coupling voltage at the probe of the detector; adjusting the distance between the probe and the chuck, using a signal acquisition circuit of the detector to collect coupling voltages at different distances, and obtaining a relationship curve between the distance and the inverse of the coupling voltage; after placing the wafer on the chuck of the detector, obtaining the coupling voltage in the current state for each detection point, calculating the distance between the probe and the wafer in the current state and the inverse of the coupling voltage corresponding to the target distance using the relationship curve according to the coupling voltage in the current state, and calculating the difference between the inverse of the target coupling voltage and the inverse of the current coupling voltage; calculating the change in the driving voltage of the driving mechanism according to the difference; the driving mechanism changes the driving voltage according to the change in the driving voltage, and drives the probe of the detector to move up and down, so that the distance between the probe and the wafer is the target value.

Description

Technical Field

[0001] The present invention relates to the technical field of wafer detection, and in particular to a method and device for controlling the distance between a probe of a detector and a wafer. Background Art

[0002] In the field of integrated circuits, detectors are often needed for defect detection, gate oxide quality inspection, and surface work function measurement. The distance between the detector probe and the wafer needs to be precisely controlled to achieve the required detection accuracy and sensitivity.

[0003] In actual production measurements, due to the different thickness and warpage of the wafer, the working distance between the detector probe and the wafer is constantly changing, so that the test data is a function of the working distance, which cannot meet the actual needs. In addition, the differences in installation accuracy between devices and processing accuracy of submodules also increase the uncertainty of the working distance.

[0004] Therefore, how to accurately control the distance between the detector probe and the wafer is a problem that needs to be solved at present. Summary of the invention

[0005] The purpose of the present invention is to provide a method and device for controlling the distance between a probe of a detector and a wafer, which can accurately control the distance between the probe of the detector and the wafer.

[0006] In order to achieve the above object, the present invention provides a method for controlling the distance between a probe of a detector and a wafer, comprising:

[0007] Before placing a wafer on a chuck of the detector, applying an AC signal to the chuck to cause the chuck to generate a disturbance signal, thereby generating a coupling voltage at the probe of the detector;

[0008] Adjusting the distance between the probe and the chuck, using the signal acquisition circuit of the detector to collect the coupling voltage at different distances, and obtaining a relationship curve between the distance and the inverse of the coupling voltage;

[0009] After the wafer is placed on the chuck of the detector, for each detection point, the coupling voltage in the current state is obtained, and according to the coupling voltage in the current state, the distance between the probe and the wafer in the current state and the reciprocal of the coupling voltage corresponding to the target distance are calculated by using the relationship curve, and the difference between the reciprocal of the target coupling voltage and the reciprocal of the current coupling voltage is calculated;

[0010] The driving mechanism calculates the change in the driving voltage of the driving mechanism according to the difference; the driving mechanism changes the driving voltage according to the change in the driving voltage, and drives the probe of the detector to move up and down, so that the distance between the probe and the wafer is the target value.

[0011] In an optional solution, the relationship curve between the distance and the reciprocal of the coupling voltage is an oblique line, the abscissa is the distance, and the ordinate is the reciprocal of the coupling voltage;

[0012] The variation of the driving voltage is the product of the difference and the slope of the oblique line.

[0013] In an optional solution, the AC signal is a sinusoidal wave voltage signal.

[0014] The present invention also provides a device for controlling the distance between a probe of a detector and a wafer, comprising:

[0015] An AC signal generator is used to apply an AC signal to the chuck of the detector before the wafer is placed on the chuck of the detector and before the detection starts after the wafer is placed on the chuck of the detector, so that the chuck generates a disturbance signal, thereby generating a coupling voltage at the probe of the detector;

[0016] The distance sensor is used to obtain the distance between the probe and the chuck before the wafer is placed on the chuck and convert it into an electrical signal output during the up and down movement of the probe;

[0017] A signal acquisition circuit, used for collecting the coupling voltage at different distances during the up and down movement of the probe before the wafer is placed on the chuck of the detector, and for collecting the coupling voltage at the current distance before the test starts after the wafer is placed on the chuck of the detector;

[0018] A controller, used for calculating a relationship curve between the distance and the inverse of the coupling voltage according to the output of the distance sensor and the coupling voltage obtained by the signal acquisition circuit before placing the wafer on the chuck of the detector, and determining the driving voltage change of the driving mechanism according to the relationship curve, the current coupling voltage, and the target distance between the wafer and the probe at the beginning of the detection;

[0019] The driving mechanism is used to drive the probe of the detector to move up and down before the wafer is placed on the chuck of the detector, and after the wafer is placed on the chuck of the detector, adjust the working voltage of the driving mechanism according to the output of the controller, so that the driving mechanism drives the probe to move so that the distance between the probe and the wafer is the target value.

[0020] In an optional solution, the driving mechanism includes a telescopic unit and a bearing plate;

[0021] One end of the carrying plate is connected to the top of the telescopic unit, and the other end of the carrying plate is used to fix the probe of the detector;

[0022] The telescopic unit can be telescoped up and down; the carrying plate drives the probe to move up and down based on the telescopic unit's telescopic movement.

[0023] In an optional solution, the device further includes a bearing base, which is mounted on the frame of the detector; and the bottom of the telescopic unit is arranged on the bearing base.

[0024] In an optional solution, the distance sensor is an LVDT, the main body of the LVDT is fixed on the frame of the detector, and the movable head of the LVDT is arranged on the bearing plate, so as to detect the displacement of the probe during the up and down movement of the probe.

[0025] In an optional solution, the telescopic unit includes a voice coil motor or a piezoelectric transducer.

[0026] In an optional solution, the device further comprises a relay, which is connected between the AC signal generator and the chuck, and is used to connect the AC signal generator and the chuck when the chuck is required to generate a disturbance signal; and to ground the chuck when performing detection.

[0027] In an optional solution, the relationship curve between the distance and the reciprocal of the coupling voltage is an oblique line, the abscissa is the distance, and the ordinate is the reciprocal of the coupling voltage;

[0028] At the beginning of the detection, according to the coupling voltage in the current state, the distance between the probe and the wafer in the current state is calculated using the relationship curve; according to the reciprocal of the coupling voltage corresponding to the target distance, the difference between the reciprocal of the target coupling voltage and the reciprocal of the current coupling voltage is calculated;

[0029] The variation of the driving voltage is the product of the difference and the slope of the oblique line.

[0030] The beneficial effects of the present invention are:

[0031] The present invention obtains a relationship curve between the distance between the probe and the chuck and the coupling voltage before placing the wafer on the chuck of the detector; after placing the wafer on the chuck of the detector, the difference between the coupling voltage corresponding to the target distance and the current coupling voltage is calculated according to the relationship curve and the coupling voltage in the current state, and the change of the driving voltage of the driving mechanism is calculated according to the difference. The driving mechanism changes the driving voltage according to the change of the driving voltage to drive the probe of the detector to move up and down, thereby realizing precise control of the distance between the wafer and the probe.

[0032] A height adjustment is performed before each measurement of a different point to avoid the problem of inconsistent heights between the probe and the measurement point caused by different wafer thicknesses or intra-wafer warpage of the same wafer. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] The above and other objects, features and advantages of the present invention will become more apparent through a more detailed description of exemplary embodiments of the present invention in conjunction with the accompanying drawings, in which like reference numerals generally represent like components.

[0034] Figure 1 Schematic diagram of the structure of a device for controlling the distance between a probe of a detector and a wafer in one embodiment of the present invention.

[0035] Figure 2 Schematic diagram of a device for controlling the distance between a probe head of a detector and a wafer detecting a warped wafer according to an embodiment of the present invention.

[0036] Figure 3 FIG. 4 is a relationship curve between the distance detected by the LVDT and the inverse of the coupling voltage in one embodiment of the present invention.

[0037] Description of reference numerals:

[0038] 1-chuck; 2-wafer; 3-probe; 4-LVDT; 5-telescopic unit; 6-carrying plate; 7-carrying base; 8-AC signal generator; 9-relay. DETAILED DESCRIPTION

[0039] The present invention is further described in detail below in conjunction with the accompanying drawings and specific embodiments. According to the following description and drawings, the advantages and features of the present invention will become clearer. However, it should be noted that the concept of the technical solution of the present invention can be implemented in a variety of different forms and is not limited to the specific embodiments described herein. The drawings are all in a very simplified form and are not in precise proportions, and are only used to conveniently and clearly assist in explaining the purpose of the embodiments of the present invention.

[0040] It should be understood that when an element or layer is referred to as being "on, adjacent to, connected to or coupled to other elements or layers, it may be directly on, adjacent to, connected to or coupled to other elements or layers, or there may be intervening elements or layers. In contrast, when an element is referred to as being "directly on, directly adjacent to, directly connected to or directly coupled to other elements or layers, there may be no intervening elements or layers. It should be understood that, although the terms first, second, third, etc. may be used to describe various elements, components, regions, layers and / or parts, these elements, components, regions, layers and / or parts should not be limited by these terms. These terms are only used to distinguish one element, component, region, layer or part from another element, component, region, layer or part. Therefore, without departing from the teachings of the present invention, the first element, component, region, layer or part discussed below may be represented as a second element, component, region, layer or part.

[0041] Spatially relative terms such as "under," "below," "below," "under," "above," "above," etc., may be used herein for ease of description to describe the relationship of an element or feature shown in the figures to other elements or features. It should be understood that in addition to the orientations shown in the figures, the spatially relative terms are intended to include different orientations of the device in use and operation. For example, if the device in the accompanying drawings is flipped, then the elements or features described as "under other elements" or "under" or "under" will be oriented as "on" the other elements or features. Therefore, the exemplary terms "under" and "under" may include both upper and lower orientations. The device may be oriented otherwise (rotated 90 degrees or other orientations) and the spatial descriptors used herein are interpreted accordingly.

[0042] The purpose of the terms used herein is only to describe specific embodiments and is not intended to be limiting of the present invention. When used herein, the singular forms "one", "an" and "said / the" are also intended to include plural forms, unless the context clearly indicates otherwise. It should also be understood that the terms "consisting of" and / or "comprising", when used in this specification, determine the presence of the features, integers, steps, operations, elements and / or parts, but do not exclude the presence or addition of one or more other features, integers, steps, operations, elements, parts and / or groups. When used herein, the term "and / or" includes any and all combinations of the relevant listed items.

[0043] Example 1

[0044] This embodiment provides a method for controlling the distance between a probe of a detector and a wafer, comprising:

[0045] Before placing a wafer on a chuck of the detector, applying an AC signal to the chuck to cause the chuck to generate a disturbance signal, thereby generating a coupling voltage at the probe of the detector;

[0046] Adjusting the distance between the probe and the chuck, using the signal acquisition circuit of the detector to collect the coupling voltage at different distances, and obtaining a relationship curve between the distance and the inverse of the coupling voltage;

[0047] After the wafer is placed on the chuck of the detector, the coupling voltage in the current state is obtained for each detection point, and the distance between the probe and the wafer in the current state is calculated using the relationship curve according to the coupling voltage in the current state; the difference between the inverse of the target coupling voltage and the inverse of the current coupling voltage is calculated according to the inverse of the coupling voltage corresponding to the target distance;

[0048] The driving mechanism calculates the change in the driving voltage of the driving mechanism according to the difference; the driving mechanism changes the driving voltage according to the change in the driving voltage, and drives the probe of the detector to move up and down, so that the distance between the probe and the wafer is the target value.

[0049] Specifically, the present method is described below with reference to a specific example.

[0050] The probe is generally a non-contact Kelvin probe. Before testing, first obtain the relationship curve between the distance between the probe and the chuck of the detector and the inverse of the coupling voltage. The bottom of the probe is a metal sheet, and the chuck / wafer is also a conductor. There is air between the probe and the chuck / wafer. The probe and the chuck / wafer are similar to the classic planar capacitor structure. When there is a disturbed signal on the chuck, there will also be a disturbed signal on the bottom metal of the probe. This signal is called coupling voltage, and the coupling voltage is inversely proportional to the distance. An AC signal can be applied to the chuck through a signal generator, such as a sinusoidal voltage signal, 0.75Vpp, 2KHz. The probe of the detector can be brought into contact with the chuck through a driving mechanism, and the coupling voltage at this time can be read. Then the probe can be gradually raised, and the distance the probe is raised and the corresponding coupling voltage value can be recorded.

[0051] This embodiment uses a linear variable differential transformer (LVDT) to measure the moving height of the probe. The LVDT linear position sensor can measure movements as small as a few millionths of an inch to ±30 inches. This type of electromechanical transducer is very common and can change the linear motion of a mechanically coupled object into a corresponding electrical signal.

[0052] After research and analysis, it is found that the distance the probe is raised is linearly related to the inverse of the coupling voltage. Figure 3 The horizontal and vertical coordinates of the solid point in the lower left corner of the straight line represent the displacement of the probe and the inverse of the coupling voltage detected by the LVDT when the probe is in contact with the chuck (the distance between the probe and the chuck is 0). The horizontal and vertical coordinates of the previous solid point adjacent to it represent the displacement of the probe and the inverse of the coupling voltage detected by the LVDT after the probe is raised a certain distance (the distance is the difference between the horizontal coordinates of the two solid points). The relationship curve of the detector is Y=0.551X+13.701,R 2 =0.9985. X represents the displacement of the probe detected by the LVDT, and Y represents the reciprocal of the coupling voltage. 2 It should be noted that the relationship curves between different detectors and chucks are not the same, and each detector needs to be tested once to obtain the relationship curve between the detector and the chuck.

[0053] Before starting the test, the wafer is placed on the chuck of the detector. For the current detection point, an AC signal generator is used to apply an AC signal to the chuck to obtain the coupling voltage in the current state. Then, the connection between the AC signal generator and the chuck is cut off and the chuck is grounded. According to the coupling voltage in the current state, the distance between the probe and the wafer in the current state is calculated using the relationship curve (according to the relationship curve, the LVDT value corresponding to the reciprocal value of the coupling voltage in the current state is found, and the LVDT value when the probe and the chuck are in contact is subtracted from the value to obtain the distance between the probe and the wafer); according to the reciprocal of the coupling voltage corresponding to the target distance (obtained according to the curve), the difference between the reciprocal of the target coupling voltage and the reciprocal of the current coupling voltage is calculated. According to the difference, the change in the driving voltage of the driving mechanism is calculated; the driving mechanism changes the driving voltage according to the change in the driving voltage, drives the probe of the detector to move up and down, and makes the distance between the probe and the wafer the target value. The driving mechanism can be a voice coil motor (VCM, Voice Coil Motor) or a piezoelectric transducer (PZT, Piezo-electric Transducer). The piezoelectric transducer is deformed by the applied voltage, so as to drive the probe of the detector to move up and down. In this embodiment, the relationship curve between the distance and the reciprocal of the coupling voltage is a slanted line, the horizontal axis is the distance, the vertical axis is the reciprocal of the coupling voltage, and the change in the driving voltage is the product of the difference between the reciprocal of the target coupling voltage and the reciprocal of the current coupling voltage and the slope of the slanted line.

[0054] During formal testing, when adjusting the probe height, the actual height of the probe movement can be monitored by LVDT, thereby further optimizing the change in the driving voltage.

[0055] This embodiment can obtain very small static error and high dynamic response, thereby achieving accurate control of the working distance between the probe and the wafer.

[0056] Example 2

[0057] Reference Figures 1 to 3 This embodiment provides a device for controlling the distance between a probe of a detector and a wafer, comprising:

[0058] The AC signal generator 8 is used to apply an AC signal to the chuck 1 of the detector before the wafer 2 is placed on the chuck 1 of the detector and before the detection starts after the wafer 2 is placed on the chuck 1 of the detector, so that the chuck 1 generates a disturbance signal, thereby generating a coupling voltage at the probe 3 of the detector;

[0059] The distance sensor is used to obtain the distance between the probe 3 and the chuck 1 before the wafer 2 is placed on the chuck 1 and during the process of the probe 3 moving up and down, and convert it into an electrical signal output;

[0060] A signal acquisition circuit is used to collect the coupling voltage at different distances during the up and down movement of the probe 3 before the wafer is placed on the chuck 1 of the detector, and to collect the coupling voltage at the current distance before the test starts after the wafer 2 is placed on the chuck 1 of the detector;

[0061] The controller is used to calculate the relationship curve between the distance and the inverse of the coupling voltage according to the output of the distance sensor and the coupling voltage obtained by the signal acquisition circuit before the wafer 2 is placed on the chuck 1 of the detector, and to determine the driving voltage change of the driving mechanism according to the relationship curve, the current coupling voltage, and the target distance between the wafer 2 and the probe 3 at the beginning of the detection;

[0062] The driving mechanism is used to drive the probe 3 of the detector to move up and down before the wafer 2 is placed on the chuck 1 of the detector, and after the wafer is placed on the chuck 1 of the detector, adjust the working voltage of the driving mechanism according to the output of the controller, so that the driving mechanism drives the probe to move so that the distance between the probe and the wafer is the target value.

[0063] Reference Figure 3 In this embodiment, the relationship curve between the distance between the probe and the chuck / wafer and the reciprocal of the coupling voltage is a slant line, with the horizontal axis being the distance and the vertical axis being the reciprocal of the coupling voltage; LKIN is the coupling voltage. At the beginning of the detection, according to the coupling voltage in the current state, the distance between the probe and the wafer in the current state is calculated using the relationship curve; according to the reciprocal of the coupling voltage corresponding to the target distance, the difference between the reciprocal of the target coupling voltage and the reciprocal of the current coupling voltage is calculated; the change in the driving voltage is the product of the difference and the slope of the slant line.

[0064] In this embodiment, the driving mechanism includes a telescopic unit 5 and a bearing plate 6; one end of the bearing plate 6 is connected to the top of the telescopic unit 5, and the other end of the bearing plate 6 is used to fix the probe 3 of the detector; the telescopic unit 5 can be telescoped up and down; the bearing plate 6 drives the probe 3 to move up and down based on the telescopic unit 5. The device also includes a bearing base 7, which is mounted on the frame of the detector; the bottom of the telescopic unit 5 is set on the bearing base 7. The telescopic unit 5 can be a voice coil motor or a piezoelectric transducer.

[0065] In this embodiment, the distance sensor is an LVDT 4, the main body of the LVDT 4 is fixed on the frame of the detector, and the movable head of the LVDT 4 is arranged on the bearing plate 6, so as to detect the displacement of the probe 3 during the up and down movement of the probe 3. The distance sensor can also be a grating or a distance encoder.

[0066] In this embodiment, the device also includes a relay 9, which is connected between the AC signal generator 8 and the chuck 1, and is used to connect the AC signal generator 8 and the chuck 1 when the chuck 1 is required to generate a disturbance signal; when performing formal testing, the connection between the AC signal generator 8 and the chuck 1 is disconnected to ground the chuck 1.

[0067] In this embodiment, a plurality of temperature sensors are installed to test the temperature of the bearing base 7 and the ambient temperature, and then the bearing base 7 temperature and the ambient temperature are fed back to the LVDT to perform temperature compensation on the displacement value measured by the LVDT. The temperature compensation reduces the influence of the ambient temperature on the test accuracy and improves the displacement accuracy and precision.

[0068] The above description is only a description of the preferred embodiments of the present invention, and is not intended to limit the scope of the present invention. Any changes or modifications made by a person skilled in the art in the field of the present invention based on the above disclosure shall fall within the scope of protection of the claims.

Claims

1. A method for controlling the distance between a probe of a detector and a wafer, characterized in that: include: Before placing a wafer on a chuck of the detector, applying an AC signal to the chuck to cause the chuck to generate a disturbance signal, thereby generating a coupling voltage at the probe of the detector; Adjusting the distance between the probe and the chuck, using the signal acquisition circuit of the detector to collect the coupling voltage at different distances, and obtaining a relationship curve between the distance and the inverse of the coupling voltage; After the wafer is placed on the chuck of the detector, for each detection point, the coupling voltage in the current state is obtained, and according to the coupling voltage in the current state, the distance between the probe and the wafer in the current state and the reciprocal of the coupling voltage corresponding to the target distance are calculated by using the relationship curve, and the difference between the reciprocal of the target coupling voltage and the reciprocal of the current coupling voltage is calculated; Calculating a change in a driving voltage of a driving mechanism according to the difference; The driving mechanism changes the driving voltage according to the variation of the driving voltage, and drives the probe of the detector to move up and down, so that the distance between the probe and the wafer is the target value.

2. The method for controlling the distance between a probe of a detector and a wafer according to claim 1, characterized in that: The relationship curve between the distance and the reciprocal of the coupling voltage is a slanted line, the abscissa is the distance, and the ordinate is the reciprocal of the coupling voltage; The variation of the driving voltage is the product of the difference and the slope of the oblique line.

3. The method for controlling the distance between a probe of a detector and a wafer according to claim 1, characterized in that: The AC signal is a sinusoidal wave voltage signal.

4. A device for controlling the distance between a probe of a detector and a wafer, characterized in that: include: An AC signal generator is used to apply an AC signal to the chuck of the detector before the wafer is placed on the chuck of the detector and before the detection starts after the wafer is placed on the chuck of the detector, so that the chuck generates a disturbance signal, thereby generating a coupling voltage at the probe of the detector; The distance sensor is used to obtain the distance between the probe and the chuck before the wafer is placed on the chuck and convert it into an electrical signal output during the up and down movement of the probe; A signal acquisition circuit, used for collecting the coupling voltage at different distances during the up and down movement of the probe before the wafer is placed on the chuck of the detector, and for collecting the coupling voltage at the current distance before the test starts after the wafer is placed on the chuck of the detector; A controller, used for calculating a relationship curve between the distance and the inverse of the coupling voltage according to the output of the distance sensor and the coupling voltage obtained by the signal acquisition circuit before placing the wafer on the chuck of the detector, and determining the driving voltage change of the driving mechanism according to the relationship curve, the current coupling voltage, and the target distance between the wafer and the probe at the beginning of the detection; The driving mechanism is used to drive the probe of the detector to move up and down before the wafer is placed on the chuck of the detector, and after the wafer is placed on the chuck of the detector, adjust the working voltage of the driving mechanism according to the output of the controller, so that the driving mechanism drives the probe to move so that the distance between the probe and the wafer is the target value.

5. The device for controlling the distance between the probe of the detector and the wafer as claimed in claim 4, characterized in that: The driving mechanism comprises a telescopic unit and a bearing plate; One end of the carrying plate is connected to the top of the telescopic unit, and the other end of the carrying plate is used to fix the probe of the detector; The telescopic unit can be telescoped up and down; the carrying plate drives the probe to move up and down based on the telescopic unit's telescopic movement.

6. The device for controlling the distance between the probe of the detector and the wafer as claimed in claim 5, characterized in that: The device also includes a bearing base, which is mounted on the frame of the detector; the bottom of the telescopic unit is arranged on the bearing base.

7. The device for controlling the distance between the probe of the detector and the wafer as claimed in claim 6, characterized in that: The distance sensor is an LVDT, the main body of the LVDT is fixed on the frame of the detector, and the movable head of the LVDT is arranged on the bearing plate, so as to detect the displacement of the probe when the probe moves up and down.

8. The device for controlling the distance between the probe of the detector and the wafer as claimed in claim 5, characterized in that: The telescopic unit includes a voice coil motor or a piezoelectric transducer.

9. The device for controlling the distance between the probe of the detector and the wafer as claimed in claim 5, characterized in that: The device also includes a relay connected between the AC signal generator and the chuck, and is used to connect the AC signal generator and the chuck when the chuck is required to generate a disturbance signal; and to ground the chuck when testing is performed.

10. The device for controlling the distance between a probe of a detector and a wafer according to claim 5, characterized in that: The relationship curve between the distance and the reciprocal of the coupling voltage is a slanted line, the abscissa is the distance, and the ordinate is the reciprocal of the coupling voltage; At the beginning of the detection, according to the coupling voltage in the current state, the distance between the probe and the wafer in the current state is calculated by using the relationship curve; According to the reciprocal of the coupling voltage corresponding to the target distance, the difference between the reciprocal of the coupling voltage of the target and the reciprocal of the current coupling voltage is calculated; The variation of the driving voltage is the product of the difference and the slope of the oblique line.

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