JP2007285804A - Eddy-current film thickness meter - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve a problem in cases where it is intended to inspect the formed state of a conductive thin film formed on a semiconductor substrate or a glass substrate for a liquid crystal display by using an eddy-current film thickness meter, that a measuring object generates heat, the temperature of a detection coil rises owing to the heat, which can cause a measurement error, the temperature rise of the detection coil increases the resistance value of the detection coil, the balance of a bridge is lost to cause an extra output voltage, and the film thickness of the measuring object fails to be correctly measured. <P>SOLUTION: Heat (radiant heat, heat convection of air) from the measuring object is prevented from reaching the detection coil by using a shield sheet, thereby keeping an impedance change due to a heat effect from occurring. Or else, an impedance change due to a heat effect is canceled out in a bridge at a subsequent stage by actively conducting heat (radiant heat, heat convection of air) from the measuring object to the detection coil and to a reference coil. By these means, the film thickness can be correctly measured even if the measuring object is at a high temperature. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an eddy current film thickness meter that measures the thickness of a conductive film such as a metal thin film in a non-contact manner, and more particularly to measures against heat received by a detection coil from an object to be measured.

  An eddy current film thickness meter is used as a conductive film inspection apparatus for nondestructively inspecting a film formation state of a conductive thin film formed on a semiconductor substrate or a glass substrate for a liquid crystal display.

  In an eddy current film thickness meter, when a conductor is placed in an alternating magnetic field, eddy current flows in the direction to cancel the magnetic field in the conductor, and the size and distribution of this eddy current depends on the shape of the conductor, conductivity, internal defects, etc. It is a measuring device based on the principle of measuring the electrical resistance value of the film by utilizing the change due to the above. This is because the magnetic field generated by the eddy current changes the impedance of the detection coil due to the mutual inductive action. By detecting this change in impedance as a change in voltage value or phase, the conductor that is the object to be inspected is detected. It is a method of knowing the state of (see, for example, Patent Document 1).

  Here, the film thickness measuring device will be described with reference to FIGS. FIG. 9 shows a schematic overall configuration of the film thickness measuring device 91. As shown in FIG. 9, the film thickness measuring device 91 is, for example, a measurement disposed above a substrate 50 such as a silicon wafer supported on a substrate stage 93 a driven by a drive system (moving mechanism) 3. Part 92.

  The drive system 93 is configured to operate in response to a command from the computer 94. By moving the substrate stage 93a in the vertical and horizontal directions, the relative positions of the measurement unit 92 and the substrate 50 are changed. It is supposed to change.

  The measurement unit 92 is provided with a support portion 92a made of, for example, an insulating material such as plastic. The support portion 92a includes an eddy current coil sensor (hereinafter referred to as “eddy current sensor”) 20 and a laser displacement sensor (hereinafter referred to as “displacement sensor”). A "laser sensor") 30 is attached.

  Here, the eddy current sensor 20 is disposed in the vicinity of the substrate 50 and is close to a conductive film (measurement target film) 51 formed on the substrate 50.

  This eddy current sensor 20 is configured by embedding a detection coil 3 and a reference coil 4 described later in a main body 2 made of an insulating material (FIG. 11). Further, the detection coil 3 and the reference coil 4 are connected to an inductance meter 95.

  The laser sensor 30 is attached to a predetermined position above the eddy current sensor.

  The laser sensor 30 is controlled by a laser sensor controller 96. By irradiating a predetermined position on the conductive film 51 on the substrate 50, the distance to the surface of the conductive film 51 can be set with high accuracy. Measure.

  Further, the inductance meter 5 and the laser sensor controller 6 are connected to a computer 94, and the computer 94 performs data analysis.

  FIG. 10 is a circuit diagram showing the configuration of the eddy current sensor 20, and FIG. 11 is a diagram for explaining the relative positional relationship between the detection coil 3 and the reference coil 4 of the eddy current sensor 20. The detection coil 3 is close to the conductive film 51 on the substrate 50.

  As shown in FIG. 10, the eddy current sensor 20 has a bridge circuit (hereinafter referred to as a bridge) 10 called a Maxwell bridge. The state where the detection coil 3 and the reference coil 4 of the eddy current sensor 20 are connected in series is shown. A thick arrow indicates that only the detection coil 3 influences the substrate 50.

In the eddy current sensor 20, a voltage generated due to mutual influence between the detection coil 3 and the substrate 50 is generated at both ends of the detection coil 3 by the alternating voltage (V _D ) applied to the bridge 10 from the alternating voltage source 26. Therefore, the difference (V _s ) between the terminals of the detection coil 3 and the reference coil 4 is obtained by the bridge 10 and sent to the computer 94 via the measurement circuit 27 and stored in advance. The film thickness is obtained by collating

  A specific method for obtaining the film thickness will be described in detail with reference to FIGS.

  A configuration example of the eddy current film thickness meter 20 is shown in FIG. The detection coil (pickup coil) 3 is arranged in the vicinity of the conductive film 51 to be measured about 0.3 mm, the reference coil 4 is arranged about several mm from the detection coil 3, and a bridge type as shown in FIG. A film is formed, and the film thickness can be known from the voltage generated when an AC voltage is applied.

R1, L1 is detected and the reference coil resistance, self-inductance, a change in impedance of the detection coil due to induced eddy currents in the conductive film 51 for each component, R _e, L _e farther To becomes as follows.

Here, assuming that the impedance of the path of I ₁ is Z ₁ , I ₁ and dI ₁ / dt can be written as follows.

When these are used to rewrite V _x , the following results.

Amplitude │V _x │ of V _x future is written as follows.

Therefore, the phase setting of the reference signal at the phase detection in the measurement of the alternating voltage signal V _x from the formula _{(1), R e, L} e is seen to be able to independently measured.

Change in the impedance of the detection coil due to eddy currents in the conductive film 51 is easily understood considering the R _e, L _e considers thin film of the conductive film 51 as one of the loop, as in Figure 14. When the mutual inductance is M _CL , the resistance of the virtual loop, and the self-inductance are R _L and L _L , the impedance Z _{C of the} detection coil is as follows.

When R _L changes in proportion to the sheet resistance of the conductive film 51, R _e and L _e change, and the output voltage of equation (1) changes. Therefore, there is a relationship between the sheet resistance and V _x , and if the “relation between the film thickness and the sheet resistance” corresponding to the material of the conductive film 51 is used, the film thickness of the conductive film 51 can be obtained from the measurement result of V _x .

  As shown in FIG. 11, the detection coil 3 and the reference coil 4 are bonded and fixed to the lower end and the inside of the main body 2 made of an insulator, respectively. The eddy current sensor 20 is supported from above and does not contact the conductive film 51.

  Conventionally, the detection coil may be affected by the ambient temperature change and the measured value may drift. Refer to the design film thickness value stored in the memory device in advance using the CPU. There has been a device that performs correction processing (see, for example, Patent Document 2).

  Furthermore, a method is disclosed in which the detection coil and the reference coil are connected in series and the amount of change in inductance component is measured by the bridge circuit. In addition, a method for correcting a measured value against a drift phenomenon of an inductance component has been developed (for example, see Patent Document 3).

JP-A-5-149927 (page 3, FIG. 1) JP 2001-343205 A (Page 4, FIG. 1) JP 2002-148010 A (page 3, FIG. 2)

  When an attempt is made to inspect the film formation state of a conductive thin film formed on a semiconductor substrate or a glass substrate for a liquid crystal display, the object to be measured has heat, and the heat raises the temperature of the detection coil. Measurement error sometimes occurred. When the temperature of the detection coil rises, the resistance value of the detection coil increases, the balance of the output of the bridge circuit is lost and an extra output voltage is generated, and the film thickness of the object to be measured cannot be measured correctly. It was that. In this case, since the detection coil portion which is a sensor is locally heated in proximity to the object to be measured, the memory device is preliminarily applied from the surrounding environment by a method as disclosed in Patent Document 2 or Patent Document 3. Even if correction processing was performed with reference to the stored design film thickness value, correction could not be performed.

  In order to solve the above-mentioned problem, the present invention provides a means for shielding or guiding heat to the coil in the main body portion of the eddy current film thickness meter so that the bridge circuit has both the detection coil and the reference coil. This cancels out the effects of heat generated by the system or the effects that occur as a result of countermeasures, and enables measurement with less error.

  The first means of the present invention uses the shielding plate (hereinafter referred to as a heat shield) to reach the detection coil using the heat (radiant heat, air convection) from the object to be measured, which is the direct cause. This prevents the impedance from changing due to the influence of heat.

  In addition, the second means of the present invention is a method in which the heat (radiant heat, air convection) from the object to be measured, which is a direct cause, is actively guided to the detection coil and the reference coil, and the impedance due to the influence of the heat. -The change in dance is canceled by the bridge circuit in the subsequent stage.

According to the first means of the present invention, the temperature increase of the detection coil due to the heat from the object to be measured is suppressed by the heat shield. Accordingly, a change in resistance value due to the temperature of the detection coil is suppressed, and a correct film thickness can be measured even when the object to be measured is at a high temperature.
In addition, since the slit is provided in the thermal shield, the influence of the eddy current in the thermal shield on the output of the bridge circuit is reduced.
Further, since a dummy having the same shape as that of the thermal shield is placed near the reference coil, the influence of the thermal shield on the output of the bridge circuit is canceled out.

  According to the second means of the present invention, the temperature rise of the detection coil and the reference coil due to heat from the object to be measured is canceled by the bridge circuit. The film thickness can be measured correctly even when the object to be measured is at a high temperature.

  Hereinafter, specific embodiments to which the present invention is applied will be described in detail with reference to the drawings.

  First, the first means of the present invention will be described.

  FIG. 1 shows a perspective view of an eddy current sensor according to an embodiment of the present invention. FIG. 2 shows a longitudinal sectional view. The detection coil 3 and the reference coil 4 are respectively bonded and fixed to the lower end and inside of the main body 2 made of an insulator.

  Further, a heat shield 5 is bonded and fixed below the detection coil 3. The heat shield 5 has a thick film made of a conductive material (metal) and is an aggregate of pieces 5a divided by the slits 5b.

  A dummy 6 is bonded and fixed below the reference coil 4. Dami-5 is an aggregate of pieces 6a having a thick film made of a conductive material (metal) and divided by slits 6b.

  As shown in FIGS. 1 and 2, a metal film (heat shield) 5 is inserted between the detection coil 3 and the substrate 50 to prevent heat inflow from the substrate 50. A heat transfer path is provided so that the heat flowing into the heat shield 5 is released to a heat bath (not shown) above the main body 20.

  If there is a metal film (heat shield) 5, an eddy current is induced there, so that the film thickness of the original conductive film 51 cannot be measured correctly and the detection sensitivity is lowered, so that the influence of the eddy current is reduced. Therefore, the diameter of the eddy current path is reduced. That is, for example, a slit 5b as shown in FIGS. 1 and 2 is inserted.

  In order to eliminate the influence of eddy current on the heat shield 5, a metal film (dummy) 6 having the same shape and thickness as the heat shield 5 is also placed under the reference coil 4 as shown in FIGS. As a result, the influence of the heat shield 5 is offset and does not appear in the bridge 10 output. That is, the impedance change of the detection coil 3 due to the heat shield 5 becomes the same as the impedance change of the reference coil 4 due to the dummy 6, and the bridge 10 output originating from the difference in impedance between the two coils remains zero. Therefore, only information on the sheet resistance of the conductive film 51 of the substrate 50 appears in the output of the bridge 10, and correct measurement is possible.

  Since the temperature of the detection coil 3 due to the heat from the substrate 50 is suppressed by the heat shield 5, the change in the resistance value of the detection coil 3 due to the temperature is suppressed, the output of the extra bridge 10 is eliminated, and even the high-temperature conductive film 51 is used. Correct film thickness measurement is possible.

  Further, since the heat shield 5 has the slit 5b, the influence of the eddy current in the heat shield 5 on the output of the bridge 10 is small. Furthermore, since the dummy 6 having the same shape as the heat shield 5 is also placed near the reference coil 4, the influence of the heat shield 5 on the output of the bridge 10 is offset.

In order to show the above effect concretely, the calculation model was used for estimation.
An example relating to the configuration of FIGS. 1 and 2 will be described. The estimation was made with a simplified model (FIG. 14) in which the sensitivity drop due to the heat shield 5 was simplified.

  First, a decrease in sensitivity due to the heat shield 5 without the slit 5b was estimated. The impedance change between the detection coil 3 and the reference coil 4 was calculated to obtain the output of the bridge 10.

  The calculation method of the sensitivity decrease by the heat shield 5 is arranged as five concentric virtual loops under the detection coil 3, and here, the conductive film 51 and the heat shield 5 are considered (see FIG. 4). For simplification, the conductive film 51 and the heat shield 5 are assumed to be at the same height (even if they are different by about 0.3 mm, the calculation result is not greatly affected). Assuming 5 loops (width 0.5mm) with radii 0.5, 1.0, 1.5, 2.0, 2.5mm, conductive film 51 as third loop, heat shield 5 as other It was made to correspond to the loop of.

The conductive film 51 has a sheet resistance equivalent to a Cu thickness of 1 μm, and the heat shield 5 has a Cu equivalent to 100 μm. The detection coil 3 is a solenoid having a length of 1.71 mm, an outer diameter of 2.4 mm, and an inner diameter of 0.4 mm. 10 turns per layer, 6 layers, 60 turns in total, distance h = 0.3 mm from coil bottom to conductive film 51, coil self-inductance L _C = 1.75 × 10 ⁻⁶ H, coil resistance R _C = It was 0.66Ω. The impedance change when the conductive film 51 does not have the third loop is also calculated, and this is used as the impedance change of the reference coil 4 by the dummy 6 and the bridge is obtained from the equation (1) (see Table 3) using these values. 10 outputs were calculated (R difference of both coils was calculated as Re and L difference was calculated as Le).

  When the heat shield 5 and the dummy 6 are present, the bridge 10 output amplitude when the AC voltage of 5 MHz and amplitude 1 V is applied to the bridge 10 is 2.40 mV (see FIG. 4).

  On the other hand, when only the third loop exists, that is, when there is no heat shield 5 and dummy 6, the output amplitude is 5.16 mV (see FIG. 3). That is, it can be said that if there is the heat shield 5 and the dummy 6 without the slits 5b and 6b, the sensitivity of the film thickness meter is approximately halved.

Next, consider a simplified model (FIG. 14) where the heat shield 5 has slits 5b. Changes in the R and L of the detection coil 3 will be examined by changing the dimensions of the loop of the heat shield 5. “Change amounts R _e and L _e of R and L of the detection coil 3” when the loop size was changed were compared using the model of FIG. The amount of change in R and L of the detection coil 3 due to the large shield is shown in FIG. The amount of change in R and L of the detection coil 3 due to the small shield is shown in FIG.

5 shows a loop radius of 1.5 mm and a width of 0.5 mm, and FIG. 6 shows a loop radius of 0.15 mm and a width of 0.05 mm. It is the result of putting values into the formulas (2) and (3) (see Table 5) and plotting them. The cases of 1 MHz and 10 MHz are shown. R _L is the resistance of the loop, the coil is the solenoid described above, and the self-inductance L _L of the loop and the mutual inductance M _CL with the coil are shown in the figure. In the loop having the radius of 1/10, the width is also 1/10. Therefore, if the thickness of the heat shield 5 is the same (if the sheet resistance is the same), R _L is the same. _RL when the heat shield 5 is copper having a thickness of 1 μm is indicated by an arrow in the figure. It can be seen that Re and Le are greatly reduced when the loop diameter is reduced.

The heat shield 5 is assumed to be thick in order to release heat. For example, if Cu is 100 μm, 1 / _RL is about 250. Further, comparing the larger Re and ωLe at each frequency (comparing the larger contribution to the output of the bridge 10), it can be seen that the magnitude is different by 3 digits at both 1 MHz and 10 MHz. The output of the bridge 10 by Re and ωLe in the figure is shown as Vx on the right vertical axis of FIGS. It can be seen that in the region where 1 / _RL is 250 and the coil is one order of magnitude smaller, this Vx is also three orders of magnitude smaller. In order to make the entire area of the heat shield 5 equal, 100 pieces with a loop diameter of 1/10 are necessary, so from the above (1/1000) times 100 = 1/10, the contribution to the output of the bridge 10 is larger than that of a large loop. 1/10. Therefore, it is considered that the decrease in sensitivity is about 1/10.

  Since the sensitivity reduction due to the heat shield 5 of the large loop is about 50%, the sensitivity reduction can be estimated to be about several percent with 1/10 of the small loop. If the loop is made smaller (and the number is increased accordingly), the influence on the coil is reduced. The effect of eddy current is reduced in the same way as coil foils used in low-temperature experiments and copper wire bundles and slits in bulk parts in Cu adiabatic demagnetization cooling.

  Accordingly, the influence of heat from the substrate 50 can be prevented with the configuration of FIG. 1 with little reduction in sensitivity, the conductivity of the heat shield 5 can be canceled, and the film thickness of the conductive film 51 can be measured correctly.

  In addition, when the heat shield 5 and the dummy 6 under the reference coil 4 are thermally connected (connected by a small thermal resistance) and a thermal resistance is provided between the heat bath (not shown) above the detection system, the detection coil 3 The temperature difference of the reference coil 4 becomes smaller, and the influence of heat from the substrate 50 can be canceled more. The thermal resistance may be adjustable by making it a jumper wire that is easy to attach and remove.

  The above is the explanation of the first means of the present invention.

  Next, the second means of the present invention will be described.

  FIG. 7 is a perspective view of an eddy current sensor 71 according to the embodiment of the present invention. FIG. 8 is a longitudinal sectional view. The bridge circuit to be used is shown in FIG.

  Unlike the first means of the present invention, heat from the substrate 50 is actively taken into the detection coil 73 and the reference coil 74, and the influence of the heat is canceled by the bridge circuit 10 (FIG. 10).

  A planar coil is used for the detection coil 73 and the reference coil 74. A planar coil is a coil wound spirally on a plane. The reference coil 74 is attached to a depressed position (concave portion) 72a of the main body 72, and has heat inflow due to heat radiation from the substrate 50 and air convection. In a planar coil, as the distance from the conductive film 51 increases, the influence of the conductive film 51 on the coil impedance decreases rapidly. On the other hand, the temperature rise of the coil due to heat from the substrate 50 does not decrease so rapidly.

  Therefore, the arrangement of FIGS. 7 and 8 causes the detection coil 73 and the reference coil 74 to have the same temperature and cancel the influence of heat, and the impedance change amount of each coil varies depending on the distance from the conductive film 51. Information on the film thickness of the conductive film 51 of the substrate 50 is output to the bridge 10 (FIG. 10).

  Therefore, only the information on the sheet resistance of the conductive film 51 of the substrate 50 appears in the bridge output 10, and correct measurement is possible.

  The above is the description of the second means of the present invention.

  As mentioned above, although embodiment of this invention was described, of course, this invention is not limited to these, Based on the technical idea of this invention, a various deformation | transformation is possible.

  For example, in the first means, the temperature difference between the detection coil 3 and the reference coil 4 is reduced by connecting the heat shield 5 and the dummy 6. Thereby, only “a change in the impedance of the detection coil 3” due to the eddy current generated in the conductive film 51 of the substrate 50 may be captured.

  Further, in the first means, the heat shield 5 and the dummy 6 are further connected between a heat bath (not shown) (an object having a large heat capacity for escaping heat), and in each connection portion, a thermal resistance is connected. May be configured to be settable. By appropriately setting the thermal resistance value, the temperature difference between the detection coil 3 and the reference coil 4 is reduced. Thereby, only “a change in the impedance of the detection coil 3” due to the eddy current generated in the conductive film 51 of the substrate 50 may be captured.

  In the second means, the reference coil 74 is attached to the recessed position (recessed portion) 72a of the main body 72 so that there is heat radiation from the substrate 50 and heat inflow due to air convection. You may attach to the through-hole (hole) and level | step difference which were provided in. The present invention is applicable if the reference coil 74 is attached so as to be farther from the conductive film 51 than the detection coil 73 and exposed to heat radiation from the substrate 50 and heat inflow due to air convection.

It is a perspective view of the eddy current type sensor 1 of the 1st means of this invention. The detection coil 3 and the reference coil 4 are fixed in the lower end and inside of the main body 2. A heat shield 5 is fixed below the detection coil 3. A dummy 6 is fixed below the reference coil 4. It is sectional drawing of the eddy current type sensor 1 of the 1st means of this invention. The heat shield is fixed between the detection coil 3 and the conductive film 51 to be measured. It is a calculation model (when there is no thermal shield) of the 1st means of this invention. The detection coil 3 is affected by the third loop corresponding to the conductive film 51 indicated by the solid line. On the other hand, the reference coil 4 has no effect. It is a calculation model (when there is a thermal shield) of the first means of the present invention. In addition to the third loop corresponding to the conductive film 51 indicated by the solid line, the detection coil is affected by the first, second, fourth, and fifth loops corresponding to the thermal shield 5. On the other hand, the reference coil is affected by the first, second, fourth, and fifth loops corresponding to Dami-6. It is a graph (when there is no slit in a heat shield) of the calculation result of the sensitivity fall by the 1st means of the present invention. It is a graph (when there is a slit in a heat shield) of the calculation result of the sensitivity fall by the 1st means of the present invention. It can be seen that Re and Le are greatly reduced compared to FIG. As a result, the effectiveness of the slit was confirmed. It is a perspective view of the eddy current type sensor 71 of embodiment of the 2nd means of this invention. The detection coil 73 is fixed to the lower end of the main body 72. On the other hand, the reference coil 74 is attached to the recess 72a. Thereby, the heat from the substrate 50 reaches both the reference coil 74 and the detection coil 73. Further, although the detection coil 73 is affected by the conductive film 51, the reference coil 74 is not affected by the conductive film 51. It is sectional drawing of the eddy current type sensor 71 of embodiment of the 2nd means of this invention. 1 is a schematic overall configuration diagram of an eddy current film thickness measuring device 91. FIG. It has a measuring unit 92 disposed above a substrate 50 such as a silicon wafer supported on a substrate stage 93a driven by a drive system (moving mechanism) 93. The drive system 93 is configured to operate in accordance with a command from the computer 94, and changes the relative position between the measurement unit 92 and the substrate 50 by moving the substrate stage 93a in the vertical and horizontal directions. It is like that. 1 is a circuit diagram of an eddy current film thickness meter (eddy current sensor) 20. FIG. A difference between outputs of the reference coil 4 and the detection coil 3 is obtained by the bridge 10 and received by the measurement circuit 27. FIG. 4 is a diagram for explaining a relative positional relationship between a detection coil 3 and a reference coil 4 of the eddy current sensor 20. The detection coil 3 is at the lower end of the main body 2 near the conductive film 51 of the substrate 50. On the other hand, the reference coil is separated from the conductive film 51 of the substrate 50. 2 is a perspective view of an eddy current sensor 20. FIG. It is a figure which shows arrangement | positioning of the component of the eddy current type sensor 20 used as the basis of a calculation model. The schematic positions of the conductive film 51, the detection coil 3, and the reference coil 4 that are measurement targets are shown. It is a circuit diagram of an eddy current type sensor. L ₁ and R ₁ correspond to the reference coil 4. L ₂ and R ₂ correspond to the detection coil 3. 3 is a calculation model of the eddy current sensor 20. The relationship between the detection coil 3 and the conductive film 51 was modeled as a calculation model. A loop corresponds to the conductive film 51. The mutual inductance M _CL affects the detection coil 3 and the conductive film 51.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Eddy current sensor (eddy current type film thickness meter), 2 ... Main-body part, 3 ... Detection coil, 4 ... Reference coil, 5 ... Thermal shield, 5a ...・ Section, 5b ... slit, 6 ... dummy, 6a ... section, 6b ... slit,
10 ... Inductance bridge (bridge), 14 ... reference resistance, 15 ... reference resistance,
20 ... Eddy current sensor (eddy current type film thickness meter), 21 ... Parallel connection point, 22 ... Parallel connection point, 23 ... Connection midpoint, 24 ... Connection midpoint, 26 ... AC voltage source, 27 ... Measurement circuit 30 ... Laser displacement sensor,
50 ... substrate, 51 ... conductive film,
71 ... Eddy current sensor (eddy current film thickness meter), 72 ... Main body, 72a ... Recess, 73 ... Planar coil (detection coil), 74 ... Planar coil (reference coil) )
DESCRIPTION OF SYMBOLS 91 ... Film thickness measuring apparatus, 92 ... Measuring part, 92a ... Supporting part, 93 ... Drive system (moving mechanism), 93a ... Substrate stage, 94 ... Computer 95 ... Inductance meter, 96 ... Laser sensor controller,

Claims (15)

Using a circuit in which a reference coil and a detection coil are connected in series and an inductance bridge in which two reference resistors are connected in series, it can be placed at a predetermined position near the conductive film formed on the surface of the measurement object An eddy current that can be arranged at a position closer to the conductive film than the reference coil and that generates a predetermined eddy current to the conductive film and detects a magnetic field due to the eddy current An eddy-current film thickness meter, which is a coil sensor, and includes means for shielding heat from the measurement object to the coil or guiding the heat to the coil. 2. The eddy current film thickness meter according to claim 1, wherein as the means, a thermal shield is provided between the detection coil and the measurement object in order to shield the heat from the measurement object. . The thermal shield has a slit for reducing the diameter of the eddy current generated in the thermal shield so that the magnetic field due to the eddy current generated in the conductive film can be detected. The eddy current film thickness meter according to claim 2. 4. The eddy current film thickness meter according to claim 2, further comprising a dummy corresponding to the thermal shield in the vicinity of the reference coil. 5. The eddy current film thickness meter according to claim 2, further comprising a heat bath connected to the heat shield to release heat of the heat shield. 6. The eddy current film thickness meter according to claim 2, wherein the heat shield and the dummy have a thick film made of a conductive material. 7. The conductive material of the heat shield and the thick thick film is any one of copper, aluminum, nickel, zinc, tin, lead, gold, and silver. The eddy current film thickness meter according to any one of the above. 8. The eddy current film thickness meter according to claim 7, wherein the conductive material of the heat shield and the thick film of the dummy is the same material. 8. The eddy current film thickness meter according to claim 7, wherein conductive materials of the heat shield and the thick film are different from each other. 10. The eddy current film thickness meter according to claim 2, wherein the thermal shield and the dummy are connected to reduce a temperature difference between the reference coil and the detection coil. 3. A thermal resistor is inserted between the heat shield and the dummy and the heat bath for connecting the heat shield and the dummy and further connecting to the heat bath. The eddy current film thickness meter according to any one of 1 to 10. The thermal shield and the dummy are connected, and further connected to a thermal bath, the thermal resistance is inserted between the thermal shield and the dummy and the thermal bath, and the value of the thermal resistance The eddy current film thickness meter according to claim 11, wherein the eddy current film thickness meter can be set. 2. The eddy current film thickness meter according to claim 1, wherein the means has a structure for guiding the heat from the measurement object to the reference coil. The eddy current film thickness meter according to claim 13, wherein the structure is formed in a main body of the eddy current coil sensor. The eddy current film thickness meter according to claim 14, wherein the structure is any one of a recess, a through hole, and a step formed in the main body.

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