Wafer resistivity and surface film thickness detection equipment based on double coils

Abstract

The utility model discloses wafer resistivity and surface film thickness detection equipment based on double coils, which integrates a low-frequency inductance coil and a high-frequency inductance coil on a probe, detects wafer resistivity and wafer surface metal film thickness in real time through the low-frequency inductance coil, and detects an LOD value in real time through the high-frequency inductance coil. And the measured resistivity of the wafer and the thickness of the metal film on the surface of the wafer can be corrected according to the LOD value. The equipment can obviously improve the resistivity detection precision of an inductance method under the condition that a high-precision positioning system is not used, and the cost of wafer resistivity detection equipment is greatly reduced.

Description

Technical Field

[0001] This utility model belongs to the field of detection technology, specifically relating to a wafer resistivity and surface thin film thickness detection device based on dual coils. Background Technology

[0002] Wafers are the fundamental material for integrated circuit manufacturing and the cornerstone of integrated circuit development. Currently, most integrated circuit chips are manufactured on wafers using bulk silicon processes. During integrated circuit manufacturing, the resistivity of the wafer and the thickness of the metal thin film on its surface are crucial process parameters. Therefore, high-precision and high-efficiency measurement of wafer resistivity and the thickness of the metal thin film on the wafer surface is necessary.

[0003] Currently, traditional testing methods such as the four-probe method are widely used for wafer resistivity testing due to their high accuracy and stability. However, the four-probe method is a contact testing method, and during the testing process, the contact between the probe and the wafer may cause damage and contamination to the wafer surface. Furthermore, the four-probe method has low testing efficiency and a small testing range, making it difficult to adapt to working scenarios with high requirements for wafer surface integrity. Therefore, it is necessary to develop high-precision and high-efficiency non-destructive testing technologies to solve the problems existing in traditional testing methods.

[0004] Non-contact wafer resistivity measurement methods include inductive methods, microwave methods, and laser methods. These methods provide rapid and non-destructive approaches to measuring wafer resistivity and the thickness of the metal thin film on the wafer surface. Among these methods, the inductive method is widely favored due to its advantages of speed, high accuracy, and low cost. In the inductive method, an AC signal drives an inductor coil, generating an alternating induced current in the wafer. This alternating induced current changes the impedance of the inductor coil through mutual inductance. Different wafer resistivities correspond to different alternating induced current intensities, causing different changes in the coil impedance through mutual inductance. Therefore, by measuring the impedance value of the inductor coil, the resistivity of the wafer can be measured.

[0005] The accuracy of the inductive method is primarily affected by changes in the lift-off height (LOD), the distance between the inductor coil and the wafer surface. Changes in LOD during testing increase the detection error. Due to environmental vibrations and positional errors during testing, LOD variation is unavoidable. To improve the accuracy of the inductive method, traditional inductive wafer resistivity testing typically employs a high-precision mechanical positioning system to maintain a constant LOD. While this significantly improves accuracy, the high-precision mechanical positioning system also drastically increases the manufacturing cost of the testing equipment. Utility Model Content

[0006] This invention addresses the problems of existing wafer inspection technologies, such as damage to the wafer surface, low inspection efficiency, low inspection accuracy, and high manufacturing costs, by providing a wafer resistivity and surface thin film thickness inspection device based on dual coils.

[0007] This utility model is achieved through the following technical solution:

[0008] A wafer resistivity and surface thin film thickness detection device based on dual coils includes an XY-axis stage and a detection probe mounted on the XY-axis stage. The XY-axis stage controls the detection probe to any detection position in the XY plane.

[0009] The detection probe includes a low-frequency coil, a high-frequency coil, an electronic potting compound, and a housing. The low-frequency coil and the high-frequency coil are both embedded inside the housing, with the high-frequency coil located at the center of the low-frequency coil. The two coils are coaxially arranged, and the bottom surfaces of the low-frequency coil and the high-frequency coil are on the same horizontal plane. The housing is filled with electronic potting compound to fix the positions of the low-frequency coil and the high-frequency coil. The low-frequency coil is used to detect the resistivity of the wafer and the thickness of the metal thin film on the wafer surface. The high-frequency coil is used to measure the LOD value between the detection probe and the wafer.

[0010] In the above technical solution, the XY dual-axis worktable includes a base, an X-axis moving mechanism and a Y-axis moving mechanism. The X-axis moving mechanism is mounted on the base, and the Y-axis moving mechanism is mounted on the X-axis moving mechanism. The X-axis moving mechanism drives the Y-axis moving mechanism to move along the X-axis direction. The detection probe is mounted on the Y-axis moving mechanism, and the Y-axis moving mechanism drives the detection probe to move along the Y-axis direction.

[0011] In the above technical solution, a first drive motor is provided at one end of the X-axis moving mechanism as the driving source of the X-axis moving mechanism; a second drive motor is provided at one end of the Y-axis moving mechanism as the driving source of the Y-axis moving mechanism.

[0012] In the above technical solution, a wafer stage is also provided on the XY-axis worktable. The wafer stage is fixedly installed on the base of the XY-axis worktable by bolts. A U-shaped groove is provided on the wafer stage for placing the wafer to be tested into the U-shaped groove.

[0013] Advantages and beneficial effects of this utility model:

[0014] The detection device of this invention integrates a low-frequency inductor coil and a high-frequency inductor coil on the probe. The low-frequency coil detects the wafer resistivity and the thickness of the metal film on the wafer surface in real time, while the high-frequency coil detects the LOD value in real time. The measured wafer resistivity and the thickness of the metal film on the wafer surface can then be corrected based on the LOD value.

[0015] This invention provides a testing device that does not require direct contact with the wafer during the testing process, thus avoiding potential damage to the material surface. It enables comprehensive and rapid testing, improving efficiency; results are available immediately after testing, eliminating waiting time; and it is suitable for various conductive materials, including ferromagnetic and non-ferromagnetic materials. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of the testing equipment of this utility model.

[0017] Figure 2 This is a schematic diagram of the cross-section of the detection probe.

[0018] Figure 3 This is a flowchart of the detection method for the detection equipment of this utility model.

[0019] For those skilled in the art, other related figures can be obtained from the above figures without any creative effort. Detailed Implementation

[0020] The technical solution of this utility model will be further described below with reference to specific embodiments.

[0021] This patent proposes a wafer resistivity and surface thin film thickness detection device based on a dual-coil circuit, see appendix. Figure 1 The testing equipment includes an XY-axis two-axis stage 1 and a testing probe 2 mounted on the XY-axis two-axis stage. The XY-axis two-axis stage 1 can control the testing probe 2 to any testing position in the XY plane, thereby scanning and testing the wafer on the XY-axis two-axis stage and testing the resistivity of the wafer.

[0022] For details, please see the appendix. Figure 1 The XY-axis two-axis worktable 1 includes a base 101, an X-axis moving mechanism 102, and a Y-axis moving mechanism 103. The X-axis moving mechanism 102 is mounted on the base 101, and the Y-axis moving mechanism 103 is mounted on the X-axis moving mechanism 102. The X-axis moving mechanism 102 drives the Y-axis moving mechanism 103 to move along the X-axis. The detection probe 2 is mounted on the Y-axis moving mechanism 103 via a mounting bracket 201. The Y-axis moving mechanism 103 drives the detection probe 2 to move along the Y-axis. Thus, through the combined action of the X-axis moving mechanism 102 and the Y-axis moving mechanism 103, the detection probe 2 can be moved to any position in the XY plane. Furthermore, one end of the X-axis moving mechanism 102 is equipped with a first drive motor 1021, serving as the drive source for the X-axis moving mechanism; one end of the Y-axis moving mechanism 103 is equipped with a second drive motor 1031, serving as the drive source for the Y-axis moving mechanism.

[0023] See appendix Figure 2The detection probe 2 includes a low-frequency coil 01, a high-frequency coil 02, an electronic potting compound 03, and a housing 04. Both the low-frequency coil 01 and the high-frequency coil 02 are embedded inside the housing 04, with the high-frequency coil 02 located at the center of the low-frequency coil 01. They are coaxially arranged, and the bottom surfaces of the low-frequency coil 01 and the high-frequency coil 02 are on the same horizontal plane. The housing 04 is filled with the electronic potting compound 03 to fix the positions of the low-frequency coil 01 and the high-frequency coil 02. The electronic potting compound has good insulation properties, preventing electrical short circuits between the coils. It also has certain heat resistance and impact resistance, adapting to the temperature and vibration conditions of the working environment, protecting the internal coils and electronic components, and providing a fixing function. After encapsulation, it can effectively isolate interference from the external environment (such as humidity and dust). The low-frequency coil 01 is used to detect the resistivity of the wafer and the thickness of the metal thin film on the wafer surface. The low-frequency coil 01 generates a large eddy current response through excitation, which can penetrate deep into the metal layer of the wafer thin film, thereby analyzing the thickness and resistivity of the metal thin film. The high-frequency coil 02 is used to measure the lift-off height (LOD) between the detection probe 2 and the wafer. The high frequency of the high-frequency coil makes the coil sensing depth shallow, which is suitable for detecting the lift-off height close to the wafer surface. The high-frequency signal is more susceptible to changes in distance and can provide accurate real-time feedback.

[0024] A wafer stage 3 is also provided on the XY-axis worktable 1. The wafer stage 3 is fixedly installed on the base 101 of the XY-axis worktable 1 by bolts. A U-shaped groove is provided on the wafer stage 3 for placing the wafer to be tested into the U-shaped groove.

[0025] A control system 4 is also provided on the XY two-axis worktable 1 to control the operation of the testing equipment.

[0026] The detection method of this utility model for wafer resistivity and surface metal thin film thickness detection equipment based on dual coils is described in the appendix. Figure 3 The details are as follows:

[0027] 1. First-time use requires calibration: Select a standard wafer sample for calibration, whose resistivity ρ and surface metal film thickness are known; then use the testing equipment of this invention to test the sample, fix the sample on the wafer stage 3, and test and record the voltage value output by the low-frequency coil 01 under different LOD values, thereby obtaining the relationship between resistivity and surface metal film thickness and the voltage value output by the low-frequency coil 01 under different LOD values.

[0028] 2. Testing: For the wafer to be tested, the sample is fixed on the wafer stage 3. By controlling the XY axis stage 1, the position of the testing probe 2 is adjusted to perform single-point or multi-point global testing at any position. During the testing process, the low-frequency coil 01 of the testing probe 2 detects the wafer in real time and outputs a voltage value (the working frequency of the low-frequency coil is 0.5MHz-0.6MHz), while the high-frequency coil 02 detects the LOD value in real time (the working frequency of the high-frequency coil is 2.5MHz-3MHz). Based on this LOD value, the resistivity value and surface metal film thickness value measured by the low-frequency coil 01 are corrected: that is, based on the relationship between the wafer resistivity and surface metal film thickness and the output voltage value of the low-frequency coil 01 under different LOD values ​​obtained by calibration, the resistivity value and surface metal film thickness value of the wafer to be tested corresponding to the LOD value detected in real time by the high-frequency coil 02 are obtained.

[0029] The above description is merely an illustration of the present utility model and is not intended to limit the present utility model to the structure and use shown and described. Therefore, all corresponding modifications and equivalents made within the spirit and principles of the present utility model shall fall within the scope of the patent application of the present utility model.

Claims

1. A wafer resistivity and surface thin film thickness detection device based on dual coils, characterized in that: The XY two-axis workbench and the detection probe installed on the XY two-axis workbench are used to control the detection position of the detection probe in the XY plane; The detection probe comprises a low-frequency coil, a high-frequency coil, electronic potting glue and a shell, the low-frequency coil and the high-frequency coil are embedded in the shell, the high-frequency coil is located at the center of the low-frequency coil, the two are coaxially arranged, and the bottom surface of the low-frequency coil and the bottom surface of the high-frequency coil are in the same horizontal plane; the inside of the shell is filled with electronic potting glue to fix the positions of the low-frequency coil and the high-frequency coil.

2. The dual coil based wafer resistivity and surface film thickness measurement apparatus of claim 1, wherein: The XY two-axis workbench comprises a base, an X-axis moving mechanism and a Y-axis moving mechanism, the X-axis moving mechanism is installed on the base, the Y-axis moving mechanism is installed on the X-axis moving mechanism, the Y-axis moving mechanism is driven by the X-axis moving mechanism to move along the X-axis direction, and the detection probe is installed on the Y-axis moving mechanism and is driven by the Y-axis moving mechanism to move along the Y-axis direction.

3. The dual coil based wafer resistivity and surface film thickness measurement apparatus of claim 2, wherein: One end of the X-axis moving mechanism is provided with a first driving motor as a driving source of the X-axis moving mechanism, and one end of the Y-axis moving mechanism is provided with a second driving motor as a driving source of the Y-axis moving mechanism.

4. The dual coil based wafer resistivity and surface film thickness measurement apparatus of claim 1, wherein: A wafer table is further arranged on the XY two-axis workbench, the wafer table is fixedly installed on the base of the XY two-axis workbench by bolts, and a U-shaped groove is arranged on the wafer table for placing a wafer to be detected in the U-shaped groove.

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