Nanoscale metal thin film thickness eddy current measurement platform and method

Abstract

The present disclosure provides a nanoscale metal thin film thickness eddy current measurement platform and method, which can reduce the influence of probe lift-off fluctuation in dynamic measurement process and improve measurement accuracy. The probe clamping module in the platform is a non-metal cantilever beam structure, the constraint end of which is fixed on the moving structure of the displacement mechanism, and the free end is provided with a square hole for installing the probe; the width from the constraint end to the free end gradually decreases; the packaging lower cover of the probe is a rectangle matched with the square hole; the packaging upper cover is provided with a core containing groove; the eddy current detection coil is placed on the bottom surface of the threaded hole in the packaging lower cover, and the core is pressed on the eddy current detection coil; the packaging upper cover is sleeved on the core and inserted into the packaging lower cover for threaded connection until the limiting part in the core containing groove contacts the core, and the probe packaging is completed; a microporous ceramic vacuum chuck is installed on the rotating platform to vacuum adsorb the metal thin film; and the thickness measurement of different points on the surface of the metal thin film is realized through the movement cooperation between the displacement mechanism and the rotating platform.

Description

Technical Field

[0001] This invention relates to the field of micro-nano detection technology, specifically to an eddy current measurement platform and method for the thickness of nanoscale metal thin films. Background Technology

[0002] Existing methods for measuring the thickness of thin metal films mainly employ the four-probe method and optical methods. The four-probe method has low measurement efficiency, and during the measurement process, the probe comes into contact with the metal film being measured, posing a risk of film damage. The optical method requires a very clean surface of the metal film, has a complex system, and a relatively small measurement range.

[0003] For nanoscale metal thin films, it is necessary to solve the problem of thickness detection of surface metal thin films on wafers of multiple sizes; moreover, it is necessary to perform multi-point measurements on the same wafer; multi-point measurement means that the probe lifting action when switching between measurements at different locations is not only time-consuming, but the fluctuation of probe lifting may also affect the measurement accuracy. Summary of the Invention

[0004] In view of this, the present invention provides a nanoscale metal thin film thickness eddy current measurement platform and method, which can realize multi-point measurement of the thickness of metal thin films on the surface of multi-size wafers, while reducing the influence of probe lift-off fluctuations during dynamic measurement and improving measurement accuracy.

[0005] To solve the above-mentioned technical problems, the present invention is implemented as follows.

[0006] A nanoscale metal thin film thickness eddy current measurement platform includes: a positioning component and a vacuum adsorption component;

[0007] The positioning component includes a displacement mechanism, a rotational motion mechanism, a probe clamping module, and a probe;

[0008] The probe clamping module is a non-metallic cantilever beam structure. One end is a constrained end, which is fixed to the moving structure of the displacement mechanism; the other end is a free end, which has a square hole for mounting the probe; the width of the constrained end is greater than that of the free end, and they are smoothly connected by a trapezoidal connecting arm.

[0009] The probe includes a lower encapsulation cover, an upper encapsulation cover, and an inner core. The lower encapsulation cover is rectangular in shape, matching the square hole at the free end of the probe clamping module, and has an internal threaded hole that matches the external thread of the upper encapsulation cover. The upper encapsulation cover has a receiving groove that matches the inner core. After the inner core is inserted into the receiving groove, the exposed portion serves as the clamping end of the eddy current detection coil. The eddy current detection coil is placed on the bottom surface of the internal threaded hole of the lower encapsulation cover, and the inner core presses against the eddy current detection coil. The upper encapsulation cover is then fitted onto the inner core and inserted into the lower encapsulation cover for threaded connection until the limiting part in the receiving groove of the inner core contacts the inner core, completing the probe encapsulation. The probe has a lead wire exit hole for the eddy current detection coil.

[0010] The rotating motion mechanism provides a rotating platform, and the vacuum suction assembly is installed on the rotating platform, and a microporous ceramic vacuum chuck is used to realize vacuum suction of the metal film;

[0011] The thickness measurement of different points on the surface of the metal film is realized through the motion cooperation between the displacement mechanism and the rotating motion mechanism.

[0012] Optionally, the lead wire lead-out hole of the eddy current detection coil arranged on the probe is arranged on the inner core and the upper cover of the packaging.

[0013] Optionally, the displacement mechanism comprises a linear displacement module and a lifting module; the lifting module is installed on the sliding block of the linear displacement module; the rotating motion mechanism is installed on the median line of the stroke of the linear displacement module, and the line connecting the rotating center and the midpoint of the stroke of the linear displacement module is perpendicular to the motion direction of the linear displacement module.

[0014] Optionally, the stroke of the linear displacement module is 400 mm, and the speed range is 120-200 mm / min; the speed range of the rotating motion mechanism is 60-240 r / min, and the rotating motion mechanism can rotate forward and reversely; the stroke of the lifting module is 10 mm, and the accuracy is 10 μm.

[0015] Optionally, the vacuum suction assembly comprises a microporous ceramic vacuum chuck, a PU gas pipe, a gas slip ring, a solenoid valve, a pressure gauge, a pressure regulating valve and a vacuum pump; the vacuum pump, the pressure regulating valve and the solenoid valve are connected in sequence; the solenoid valve provides negative pressure to the microporous ceramic vacuum chuck through the PU gas pipe provided with the gas slip ring; the pressure gauge is used to measure the pressure of the vacuum pipeline, and the microporous ceramic vacuum chuck is subjected to air suction and pressure relief by changing the working state of the solenoid valve.

[0016] Optionally, the outer wall of the lower cover of the packaging of the probe is provided with two protrusions, and threaded holes are arranged on the protrusions; the square hole arranged on the free end of the probe clamping module has a groove matched with the protrusions and a mounting step with a threaded hole; after the probe is inserted into the square groove of the probe clamping module, the probe is fixed and connected through bolts.

[0017] Optionally, the width of the constraint end of the probe clamping module is 90 mm, and the width of the free end is 36 mm.

[0018] Optionally, the rotating motion mechanism and the microporous ceramic vacuum chuck are fixed and connected through bolts through an adapter plate; the microporous ceramic vacuum chuck and the rotating platform of the rotating motion mechanism are coaxial.

[0019] Optionally, the probe clamping module is made of polyformaldehyde material.

[0020] The application further provides a nanoscale metal film thickness eddy current measurement method, which adopts the measurement platform.

[0021] Place the wafer to be measured in a coaxial position with the microporous ceramic vacuum chuck and control the vacuum suction assembly to perform suction;

[0022] The upper control end sends a first instruction to control the servo motor of the displacement mechanism to rotate, so that the probe is in the wafer center position in the initial state, at which time the thickness of the wafer center position is measured;

[0023] The upper control end sends a second instruction to control the probe to move a specified distance along the diameter direction of the wafer, and then sends a third instruction to control the servo motor of the rotary motion mechanism to rotate, so that the wafer rotates one revolution, and the thickness of the film on the current path is measured;

[0024] The second instruction and the third instruction are repeatedly executed to control the probe to move different distances along the diameter direction of the wafer, and the wafer rotates one revolution, so that the measurement of multiple points in the wafer plane can be completed.

[0025] Advantages:

[0026] (1) The measurement platform provided by the application adopts a combined structure of a displacement mechanism and a rotary motion mechanism. The probe is fixed on the displacement mechanism by a clamping mechanism and is controlled by the displacement mechanism to move in three dimensions, thereby controlling the plane and height position of the probe. The rotary motion mechanism carries the wafer, i.e. the nanoscale metal film to be measured, and changes the position of the detection point by rotating. Through the cooperation of displacement and rotation, the probe can detect the thickness of each position on the wafer without moving too much, thereby reducing the influence of probe movement on measurement accuracy.

[0027] (2) The rotary motion mechanism uses suction to carry the wafer and does not limit the size of the wafer, so that the measurement of the thickness of the surface metal film of a wafer of multiple sizes can be realized.

[0028] (2) Considering that the metal film is nanoscale and very sensitive to slight vibration, the probe clamping module of the application adopts a tapered design, with the width gradually decreasing from the constraint end to the free end, thereby reducing the conduction of motor vibration of the moving mechanism to the probe, so as to reduce the influence of probe lift fluctuation during dynamic measurement and improve measurement accuracy.

[0029] (3) The application designs a special probe packaging structure with square connection and protruding connecting ears, which can not only ensure the stability of the coil, but also ensure the connection and fastening between the probe and the clamping module, thereby reducing the influence of vibration on the lift height.

[0030] (4) In a preferred embodiment, the probe clamping module is made of polyformal material, which has good physical properties and dimensional stability, further reducing the influence of probe lift fluctuation during dynamic measurement and improving measurement accuracy. BRIEF DESCRIPTION OF DRAWINGS

[0031] Figure 1 This is a three-dimensional view of the entire invention;

[0032] Figure 2 This is a connection diagram between the rotating module and the metal film fixing module;

[0033] Figure 3 This is a connection diagram between the linear displacement module and the lifting module;

[0034] Figure 4 3D diagram and cross-sectional view of the probe packaging module;

[0035] Figure 5 This is a schematic diagram of a robotic arm for holding the probe.

[0036] Figure 6 This is an overall connection diagram of the vacuum adsorption module. Detailed Implementation

[0037] The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0038] This invention provides a nanoscale metal thin film thickness eddy current measurement platform. The platform employs a combination of a displacement mechanism and a rotational motion mechanism. The probe is fixed to the displacement mechanism via a clamping mechanism and its three-dimensional movement is controlled by the displacement mechanism to control the probe's position. The rotational motion mechanism carries the wafer, i.e., the nanoscale metal thin film to be measured, and changes the position of the detection point by rotating it. Through the coordination of displacement and rotation, the thickness of the probe at various locations on the wafer can be measured without excessive movement. Furthermore, the rotational motion mechanism uses an adsorption method to carry the wafer, which is not limited by wafer size and can realize the measurement of the thickness of surface metal thin films on wafers of various sizes.

[0039] Furthermore, considering that metal films are nanoscale and highly sensitive to minute vibrations, this invention designs a probe clamping module and probe packaging structure with a special structure, which can ensure the stability of coil fixation and the tight connection between the probe and the clamping module, reducing the impact of vibration on the lifting height.

[0040] like Figure 1 As shown, the measurement platform proposed in this invention consists of two parts: a positioning component and a vacuum adsorption component. The positioning component includes a displacement mechanism, a rotational motion mechanism 3, a probe clamping module 4, and a probe 5.

[0041] The probe clamping module is fixed on the displacement mechanism, and the probe is fixed on the probe clamping module. The metal film to be measured is arranged on the rotary motion mechanism. The displacement mechanism provides horizontal displacement and height adjustment, and provides a basic measurement position for the probe. The rotary motion mechanism drives the metal film to be measured to rotate, and the probe moves relative to the metal film to be measured. During measurement, the linear motion of the displacement mechanism and the rotation of the rotary motion mechanism enable the probe to measure any point on the metal film to be measured.

[0042] Referring to Figure 3 In an embodiment, the displacement mechanism comprises a linear displacement module 1 and a lifting module 2. The lifting module is installed on the sliding block of the linear displacement module. The rotary motion mechanism is installed on the median line of the stroke of the linear displacement module, and the line connecting the center of the rotary circle and the midpoint of the stroke of the linear displacement module is perpendicular to the motion direction of the linear displacement module. The cooperation of the linear displacement module and the lifting module makes the control simple and the precision high.

[0043] As Figure 1 shown. In a preferred embodiment, the stroke of the linear displacement module is 400 mm, the speed is 120-200 mm / min, the speed of the rotary motion module is 60-240 r / min, the rotary motion module can rotate forward or reversely, the stroke of the lifting module is 10 mm, and the precision is 10 μm. The linear displacement module adopts a C5 grade ball screw and a guide rail for transmission, and is used for adjusting the horizontal position of the probe of the eddy current sensor. Two limit sensors and one photoelectric origin sensor are respectively installed on the linear displacement module, and are used for limiting and setting the origin. The lifting module is used for adjusting the vertical height of the probe of the eddy current sensor, and can be controlled by a differential head. The linear displacement module and the lifting module are fixed and connected by bolts, as Figure 3 shown. The thickness measurement of different points on the surface of the metal film is realized by the cooperation of the linear displacement module and the rotary module.

[0044] Referring to Figure 1 and Figure 5The probe clamping module 4 is used to install the sensitive element (i.e. the detection coil) of the eddy current sensor and fix the position of the sensitive element relative to the linear displacement module. Since the eddy current sensor belongs to an electromagnetic sensor, other metals should be avoided around the probe as much as possible. Therefore, the probe clamping module is made of non-metallic material, preferably polyformaldehyde material, which has good physical properties and dimensional stability. During the movement of the linear displacement table, the probe clamping module may be affected by vibration due to the operation of the motor and environmental factors, thereby affecting the lift-off height and measurement accuracy. Therefore, the probe clamping module is designed in a tapered shape, one end of which is a constraint end 41 fixed to the moving structure of the displacement mechanism, and the other end is a free end 42, which is provided with a square hole 43 for installing the probe. The width of the probe clamping module gradually decreases from the constraint end (large end) to the free end (small end), and the constraint end and the free end are smoothly connected through a trapezoidal connecting arm. In the embodiment of the present application, the width of the two ends decreases from 90 mm to 36 mm. In the embodiment of the present application, the large end of the probe clamping module is connected to the lifting module on the linear displacement module and can move with the displacement table, and the small end of the probe clamping module is used to clamp the probe. The connection between the probe clamping module and the probe and the lifting module can be connected by bolt fixing. Figure 1

[0045] As shown in Figure 4 , the probe 5 is divided into an upper packaging cover 51, an inner core 52 and a lower packaging cover 53, the inner core and the lower packaging cover fix the eddy current sensor coil 54, and after the upper packaging cover is connected with the inner thread of the lower packaging cover through the outer thread, the upper packaging cover contacts the inner core to complete the overall packaging. The opening on the coil probe 5 leads out. The two ends of the lead wire are welded with the inner core and the outer layer of the SMA coaxial line respectively and are fixed by using a heat shrink tube to prevent loosening, and high-temperature epoxy resin glue is used to fill the gap of the probe packaging.

[0046] Specifically, the outer shape of the lower packaging cover is rectangular which matches the square hole of the free end of the probe clamping module, and the two are connected in a square shape, which is more stable than a cylindrical shape. The lower packaging cover is provided with an inner thread hole which matches the outer thread of the upper packaging cover; the upper packaging cover is provided with a receiving groove which matches the inner core, and the exposed part of the inner core after being inserted into the receiving groove serves as the pressing end of the eddy current detection coil; the eddy current detection coil is placed on the bottom surface of the inner thread hole of the lower packaging cover, and the inner core is pressed on the eddy current detection coil, the upper packaging cover is sleeved on the inner core and is screwed into the lower packaging cover, until the limiting part in the receiving groove of the inner core contacts the inner core, the packaging of the probe is completed. Figure 4 In the structure shown in the figure, the inner core and the upper packaging cover are provided with lead wire lead-out holes at the central axes thereof, which are convenient for leading out the lead wire.

[0047] ​Preferably, the outer wall of the lower cover of the package is provided with two protrusions, and threaded holes are formed in the protrusions. The square hole formed in the free end of the probe clamping module has a groove matching the protrusions and a mounting step with a threaded hole. After the probe is inserted into the square slot of the probe clamping module, the probe is fixed and connected by bolts. In this way, the stability of the coil can be ensured, and the connection between the probe and the clamping module can be fastened, thereby reducing the influence of vibration on the lift-off height.

[0048] Referring to Figure 2 , the rotary motion mechanism provides a rotating platform on which the vacuum suction assembly is installed. As shown in Figure 6 , the vacuum suction assembly includes a microporous ceramic vacuum chuck 61, a PU air pipe 62, an air slip ring 63, a solenoid valve 64, a pressure gauge 65, a pressure regulating valve 66, and a vacuum pump 67. The vacuum pump, the pressure regulating valve, and the solenoid valve are connected in sequence. The solenoid valve provides negative pressure to the microporous ceramic vacuum chuck through the PU air pipe provided with the air slip ring, and the air slip ring is responsible for ensuring that the vacuum pipeline is not affected by rotation. The pressure gauge is used to measure the pressure of the vacuum pipeline. The vacuum pump generates negative pressure and uses the pressure regulating valve to adjust the pressure of the vacuum pipeline. The negative pressure is applied to one side of the wafer, and the pressure difference between the two sides of the wafer is the difference between the atmospheric pressure and the internal pressure of the chuck, which can fix and release the wafer. By changing the working state of the solenoid valve, the metal thin film fixing module can be pumped and depressurized, thereby realizing the fixing and releasing of the wafer. The microporous ceramic vacuum chuck 61 can be installed on the rotating platform by a adapter plate 7 using bolts. The microporous ceramic vacuum chuck is coaxial with the rotating platform, and the installation method of the adapter plate facilitates the replacement and maintenance of the microporous ceramic vacuum chuck 61.

[0049] The multi-point measurement process is completed by the displacement mechanism and the rotary motion mechanism. The motor operation actions of the displacement mechanism and the rotary motion mechanism are set as a set of instructions, and each instruction includes the direction, angle, and speed parameters of the motor rotation. When measuring, the instructions are issued to realize the sequential operation of the two modules.

[0050] The main process of the test is as follows: first, place the wafer to be measured in the coaxial position with the vacuum ceramic chuck and perform suction. Send instruction 1 through the upper control end to control the servo motor of the displacement mechanism to rotate, ensuring that the probe is in the center of the wafer in the initial state, and measure the thickness of the center of the wafer at this time. Then, control the probe to move a certain distance along the diameter of the wafer through instruction 2, and control the servo motor of the rotary motion mechanism to rotate one revolution through instruction 3, thereby measuring the thickness of the film on the path. Repeat instructions 2 and 3 to control the probe to move different distances along the diameter of the wafer, and make the wafer rotate one revolution, thereby completing the measurement of the multi-point positions in the wafer plane.

[0051] In practice, the power line of the servo motor, the coding line, and the limiting line of the positioning module are connected with the servo driver, and then the Panaterm is used to adjust the parameters of the servo driver and carry out debugging. The communication mode is MINAS standard protocol, and the number of instruction pulses received by the motor per rotation is 10000. After debugging, the communication mode is modified to Modbus, the RS485 bus is connected, the Modbus communication baud rate and parity bit are set, and then the pre-execution motion of the positioning platform is set. Finally, the precise displacement control of the positioning platform is realized by sending instructions using Modbus commix.

[0052] The rotation table and the motor rotation speed ratio is 1 / 12, that is, the rotation table needs to rotate 12 circles for every 1 circle of the motor, and 120000 pulses need to be sent. The lead of the displacement table is 4mm, that is, the motor needs to rotate 1 circle for every 4mm of the displacement table, and 10000 pulses need to be sent.

[0053] The above specific embodiments only describe the design principles of the present application, and the shapes and names of the components in the description can be different and are not limited. Therefore, those skilled in the art of the present application can modify or equivalently replace the technical solutions described in the foregoing embodiments; and these modifications and replacements do not deviate from the purpose and technical solutions of the present application, and should all belong to the protection scope of the present application.

Claims

1. A nanoscale metal thin film thickness eddy current measurement platform, characterized in that, The application relates to a metal film thickness measuring device. The device comprises a positioning assembly and a vacuum suction assembly. The positioning assembly comprises a displacement mechanism, a rotary motion mechanism, a probe clamping module and a probe. The probe clamping module is a non-metal cantilever beam structure, one end of which is a constraint end fixed on the moving structure of the displacement mechanism, and the other end is a free end provided with a square hole for mounting the probe. The probe comprises a lower packaging cover, an upper packaging cover and an inner core. The outer shape of the lower packaging cover is rectangular and matched with the square hole of the probe clamping module, and the lower packaging cover is provided with an internal thread hole matched with the external thread of the upper packaging cover. The upper packaging cover is provided with a receiving groove matched with the inner core.

2. The measurement platform of claim 1, wherein, The exposed part of the inner core after being inserted into the receiving groove is used as the compression end of the eddy current detection coil.

3. The measurement platform of claim 1, wherein, The eddy current detection coil is placed on the bottom surface of the internal thread hole of the lower packaging cover.

4. The measurement platform of claim 3, wherein, The inner core is compressed on the eddy current detection coil.

5. The measurement platform of claim 1, wherein, The upper packaging cover is sleeved on the inner core and is screwed into the lower packaging cover until the limiting part in the receiving groove of the inner core contacts the inner core, and the packaging of the probe is completed.

6. The measurement platform of claim 1, wherein, The probe is provided with a lead-out hole of the eddy current detection coil.

7. The measurement platform of claim 1, wherein, The rotary motion mechanism provides a rotary platform, and the vacuum suction assembly is installed on the rotary platform.

8. The measurement platform of claim 1, wherein, The micro-porous ceramic vacuum chuck is used to realize the vacuum suction of the metal film.

9. The measurement platform of claim 1, wherein, The thickness measurement of different points on the surface of the metal film is realized through the motion cooperation between the displacement mechanism and the rotary motion mechanism. The lead-out hole of the eddy current detection coil is arranged on the inner core and the upper packaging cover. The displacement mechanism comprises a linear displacement module and a lifting module. The lifting module is installed on the sliding block of the linear displacement module. The rotary motion mechanism is installed on the median line of the stroke of the linear displacement module, and the connection line between the rotary center and the midpoint of the stroke of the linear displacement module is perpendicular to the motion direction of the linear displacement module. The stroke of the linear displacement module is 400mm, and the speed range is 120-200mm / min. The speed range of the rotary motion mechanism is 60-240r / min, and the rotary motion mechanism can rotate forward and reversely. The stroke of the lifting module is 10mm, and the precision is 10mu m. The vacuum suction assembly comprises a micro-porous ceramic vacuum chuck, a PU air pipe, an air slip ring, an electromagnetic valve, a pressure gauge, a pressure regulating valve and a vacuum pump. The vacuum pump, the pressure regulating valve and the electromagnetic valve are sequentially connected. The electromagnetic valve provides negative pressure for the micro-porous ceramic vacuum chuck through the PU air pipe provided with the air slip ring. The pressure gauge is used for measuring the pressure of the vacuum pipeline. The vacuum pump, the pressure regulating valve and the electromagnetic valve are sequentially connected. The electromagnetic valve provides negative pressure for the micro-porous ceramic vacuum chuck through the PU air pipe provided with the air slip ring. The pressure gauge is used for measuring the pressure of the vacuum pipeline. The limiting part in the receiving groove of the inner core contacts the inner core, and the packaging of the probe is completed. The lower packaging cover of the probe is provided with two protrusions, and the protrusions are provided with thread holes. The square hole of the probe clamping module is provided with a groove matched with the protrusions and a mounting step provided with a thread hole. After the probe is inserted into the square groove of the probe clamping module, the probe is fixed and connected through bolts. The width of the constraint end of the probe clamping module is 90mm, and the width of the free end is 36mm. The rotary motion mechanism and the micro-porous ceramic vacuum chuck are fixed and connected through a conversion plate and bolts. The micro-porous ceramic vacuum chuck and the rotary platform of the rotary motion mechanism are coaxial. The probe clamping module is made of polyformaldehyde material.

10. A method of measuring the thickness of a nanoscale metal film by eddy current, characterized in that, The method comprises the following steps: The wafer to be measured is placed in a coaxial position with the microporous ceramic vacuum chuck, and the vacuum suction assembly is controlled to perform suction; The upper control end sends a first instruction to control the servo motor of the displacement mechanism to rotate, so that the probe is in the wafer center position in the initial state, and the thickness of the wafer center position is measured at this time; The upper control end sends a second instruction to control the probe to move a specified distance along the wafer diameter direction, and then sends a third instruction to control the servo motor of the rotary motion mechanism to rotate, so that the wafer rotates one round, and the film thickness on the current path is measured; The second instruction and the third instruction are repeatedly executed to control the probe to move different distances along the wafer diameter direction and make the wafer rotate one round, so that the measurement of multiple points in the wafer plane can be completed.

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