JP4467760B2 - Film thickness measurement method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to the technical field of film thickness measurement, and more particularly, to a technique for obtaining film thickness by generating an eddy current in a conductive thin film and measuring a change in inductance component due to the influence of the eddy current.
[0002]
[Prior art]
An example of a conventional film thickness measurement method will be described.
Reference numeral 110 in FIG. 11A indicates a substrate body such as a silicon substrate, and a conductive thin film 111 made of a metal thin film is formed on the substrate body 110.
[0003]
When the thickness of the conductive thin film 111 is to be measured, as shown in FIG. 5B, a part of the conductive thin film 111 is removed to form an opening 112, and a probe is formed on the surface of the conductive thin film 111. When the tip of the electrode is brought into contact with each other and the opening 112 is crossed, a step between the surface of the conductive thin film 111 and the surface of the substrate body 110 at the bottom of the opening 112 is detected by a probe, and the thickness of the conductive thin film 111 is measured. (Stylus thickness measurement method).
[0004]
This film thickness measuring method is used for evaluation of a process for growing a thin film, a process for etching a thin film, and the like because an accurate value that is not affected by distortion or warpage of the substrate body 110 or the like can be obtained.
[0005]
However, the above measurement method is complicated. Moreover, since an opening cannot be formed in the semiconductor substrate that is the product, a substrate for film thickness measurement is prepared separately, a conductive thin film is formed by the same process as the product, and the thickness of the conductive thin film is measured. It is necessary to estimate the film thickness of the conductive thin film that is actually formed. Therefore, the above method is an indirect film thickness measurement.
[0006]
[Problems to be solved by the invention]
It is an object of the present invention to provide a technique that can directly and accurately measure a conductive thin film to be measured.
[0007]
[Means for Solving the Problems]
  The present invention was created in order to solve the disadvantages of the prior art, and the invention according to claim 1 is a circuit in which a reference coil and a measurement coil are connected in series, and two reference resistors are connected in series. An inductive bridge connected in parallel with a circuit is used, a conductive thin film is disposed closer to the measurement coil than the reference coil, and an AC voltage is applied to the inductance bridge to create a vortex in the conductive thin film. Generate current,It is an output terminal of the inductance bridgeA first step of measuring a voltage appearing between connection midpoints, and from the voltage appearing between the connection midpoints, the film of the conductive thin filmThicknessA film thickness measurement method to be obtained,ConductivityAn AC voltage is applied to the inductance bridge in a state where the thin film is not brought close to the reference coil and the measurement coil, and the series connection circuitSaidSecond step of measuring the AC voltage appearing between the connection midpointsAnd a distance measuring step for measuring a distance between the measuring coil and the conductive thin film,HaveIn advance, a reference conductive thin film having a different thickness is used as the conductive thin film, and the difference between the measurement results of the first and second steps and the measurement result of the distance measurement step are recorded as a database to be measured. The first and second steps and the distance measurement step are performed using the measurement conductive thin film as a conductive thin film, and the difference between the measurement results of the first and second steps and the distance measurement step Check the measurement results against the database,It is a film thickness measuring method for determining the film thickness of the conductive thin film.
  The invention described in claim 2 is the film thickness measuring method according to claim 1, wherein the first step is performed immediately before or after the second step.
  According to a third aspect of the present invention, a change in film thickness of the conductive thin film is detected.OrClaim2The film thickness measuring method according to any one of the above, wherein the first step is a film thickness measuring method performed twice or more during a film thickness change of the conductive thin film.
[0008]
First, the measurement principle of the present invention will be described. Reference numeral 10 in FIG. 2 indicates an inductance bridge called a Maxwell bridge.
[0009]
The inductance bridge 10 includes a measurement coil 11, a reference coil 12, and first and second reference resistors 14 and 15.
[0010]
The measurement coil 11 and the reference coil 12 are connected in series with each other at the connection middle point 23, and the first and second reference resistors 14 and 15 are similarly connected in series with each other at the connection middle point 24. Yes.
[0011]
The series connection circuit of the measurement coil 11 and the reference coil 12 and the series connection circuit of the first and second reference resistors 14 and 15 are connected in parallel to each other at parallel connection points 21 and 22 at both ends thereof.
[0012]
If the magnitude of the inductance component of the measuring coil 11 and the magnitude of the inductance component of the reference coil 12 are made equal, and the resistance components of the first and second reference resistors 14 and 15 are made equal, the inductance bridge 10 is balanced, AC voltage V at parallel connection points 21 and 22_DDoes not appear between the connection midpoints 23 and 24.
[0013]
However, even if the inductance bridge 10 is balanced, when the substrate 5 is brought close to the measuring coil 11, eddy currents are generated in the conductive thin film formed inside the substrate 5 or on the surface of the substrate 5, Due to the influence of the eddy current, the magnitude of the inductance component of the measuring coil 11 changes, and the balance of the inductance bridge 10 is lost. As a result, the AC voltage V between the connection middle points 23 and 24_SAppears.
[0014]
AC voltage V applied to the inductance bridge 10_DThe
V_D = V_D0・ Exp (iωt)
The AC voltage V appearing between the connection midpoints 23 and 24_SIs
V_S = V_S0・ Exp (iωt + φ) = V_S0・ Exp (iωt) ・ cos (φ) + i ・ V_S0・ Exp (iωt) ・ sin (φ)
It is represented by
[0015]
AC voltage V appearing at these connection midpoints 23 and 24_SOf the applied AC voltage V_DWhen the voltage having the phase synchronized with the voltage and the voltage having the phase shifted by 90 ° are obtained, the magnitude of the change in the inductance component of the measuring coil 11 due to the influence of the eddy current, that is, the inductance component of the measuring coil 11 is obtained from the ratio. A change amount ΔL is obtained.
[0016]
The change amount ΔL of the inductance component is a value corresponding to the eddy current loss in the substrate 5, and the AC voltage V_DTherefore, if the specific resistance of the substrate 5 or the conductive thin film (for example, copper thin film) on the surface of the substrate 5 is known, the film thickness can be obtained.
[0017]
In general, if the main body of the substrate 5 is an insulating substrate, eddy currents are generated only in the conductive thin film. On the other hand, even if the main body of the substrate 5 is a semiconductor substrate, the conductivity is lower than that of the conductive thin film. Since the eddy current generated in the semiconductor substrate is negligible, the change amount ΔL of the inductance component can be regarded as an influence due to the eddy current generated in the conductive thin film.
[0018]
However, the amount of change ΔL of the inductance component of the measurement coil 11 is influenced by the distance W between the measurement coil 11 and the conductive thin film on the surface of the substrate 5 in addition to the material of the conductive thin film.
[0019]
Conversely, for a conductive thin film having a known film thickness D, the distance W and the amount of change ΔL of the inductance component are measured and associated with each other as storage data, and a database is constructed. An unknown film thickness D can be obtained by bringing a substrate having a film thickness D closer to the measuring coil 11, measuring the distance W and the amount of change ΔL in the inductance component, and collating it with a database. However, this is a case where the conductivity is constant, for example, the material of the conductive thin film when the database is produced and the conductive thin film of unknown film thickness D are the same.
[0020]
Actually, a plurality of substrates having conductive thin films having different film thicknesses are prepared in advance, and the film thickness D of the conductive thin film on each substrate is measured with a stylus type film thickness measuring device or the like, and the distance W Is measured, and the variation ΔL of the inductance component for each substrate is measured, and the measured values of the film thickness D, the distance W, and the variation ΔL are stored as stored data in a storage device, thereby obtaining a database.
[0021]
FIG. 4 is a graph for explaining the relationship between the distance W and the change amount ΔL of the inductance component, where the horizontal axis is the distance W and the vertical axis is the change amount ΔL of the inductance component.
[0022]
The plot in the graph is an example of the stored data in the database, and a substrate with a conductive thin film thickness D of 435.5 nm, 752.3 nm, 949.8 nm, 1168.0 nm, and 1851.7 nm is used. Is stored data of the amount of change ΔL of the inductance component of the measuring coil 11 when V is changed to 200 μm, 250 μm, 300 μm, 350 μm, and 400 μm.
[0023]
The AC voltage V applied to the inductance bridge 10_DIs about several volts, for example, and the frequency is about 1 MHz to 10 MHz.
[0024]
The symbol a₁~ A_FiveThis curve is a curve obtained by connecting stored data in the database for each substrate having a different film thickness D. From this graph, it can be seen that the change amount ΔL of the inductance component is a function of the distance W and the film thickness D (ΔL = f (W, D)).
[0025]
FIG. 5 is a graph in which the horizontal axis represents the amount of change ΔL in the inductance component, and the vertical axis represents the film thickness D.₁~ B_Five4 is a curve obtained by connecting stored data having the same distance W by cubic spline interpolation in the database of FIG.
[0026]
Here, five curves b of 200 μm, 250 μm, 300 μm, 350 μm, and 400 μm where stored data exist are shown.₁~ B_FiveAlthough only shown, a cubic spline curve can be obtained by interpolating the measurement result for an arbitrary distance W having a size other than the above.
[0027]
Accordingly, when a substrate with an unknown film thickness D is brought close to the measuring coil 11 and the distance W and the change amount ΔL of the inductance component are measured, a cubic spline curve passing through the measurement result is obtained from the measurement result and the stored data in the database. be able to.
[0028]
When the measured variation ΔL of the inductance component is given to this cubic spline curve, an unknown film thickness D is obtained.
[0029]
The conductive thin film that can measure the distance W and the amount of change ΔL and can check the film thickness D by collating with the database has the same conductivity as the conductive thin film obtained when the stored data constituting the database is obtained. Need to be. There are various types of conductive thin films, such as copper thin films, aluminum thin films, and alloy thin films. A database may be prepared for each material of the conductive thin film to be measured.
[0030]
As described above, if the method of the present invention is used, there is no need to move the substrate or the measurement coil 11 to make the distance W constant, so a mechanism for moving the substrate or the measurement coil 11 in the vertical direction is unnecessary. Since no movement time in the vertical direction is required, high-speed measurement is possible at low cost.
[0031]
8 to 10 are graphs showing the measurement accuracy of the method of the present invention and other film thickness measurement methods.
[0032]
The graph of FIG. 8 is an example in which the film thickness distribution of the copper thin film formed on the surface of the silicon substrate is measured, and the horizontal axis indicates the distance from the substrate center to the measurement point when the substrate center is zero. The vertical axis indicates the measured film thickness.
[0033]
D₁Is a curve obtained by moving the substrate or the measurement coil 11 in the vertical direction, making the distance W between the copper thin film and the measurement coil 11 constant, measuring the change ΔL of the inductance component, and connecting the obtained film thickness D ( Distance adjustment method), symbol d₂Is a curve connecting the results of measuring the resistance value by the four-probe method and converting it to the film thickness D, and the symbol d_ThreeIs a line segment connecting the film thicknesses D determined by the method of the present invention.
[0034]
According to the method of the present invention, it can be seen that even if the distance W is not constant, it is obtained with high accuracy.
[0035]
The graph of FIG. 9 is the result of measuring the in-plane film thickness distribution of the copper thin film for the seed layer formed on the silicon substrate surface by the sputtering method. Symbol e₁Is a curve connecting the film thickness D when the change amount ΔL of the inductance component is measured with the distance W between the copper thin film and the measuring coil 11 constant (distance adjustment method), and the symbol e₂The two curves shown by are the results of two measurements by the method of the present invention.
[0036]
The graph of FIG. 10 shows the measurement results when a copper thin film for wiring is further laminated by plating on the surface of the copper thin film of the substrate used when the graph of FIG. 9 is obtained. Symbol f₁Is the curve e in FIG.₁Is a curve connecting the measurement results when the distance W is constant,₂The two curves shown by are the film thickness distribution obtained by the method of the present invention.
[0037]
As described above, the method of the present invention has the same accuracy as when the distance W is constant.
[0038]
Next, an accurate method for obtaining the inductance component variation ΔL will be described.
It is known that there is a drift phenomenon in the inductance element. Even when the inductance bridge 10 is balanced and no voltage appears between the connection midpoints 23 and 24, the balance is lost and the connection is lost. It has been confirmed that a voltage appears at the midpoints 23 and 24.
[0039]
It is said that the drift phenomenon is the effect of temperature change or the influence of the surrounding magnetism, but the cause is not yet clearly understood.
[0040]
An example of the drift phenomenon is shown in FIG.
The vertical axis of FIG. 6 indicates the magnitude of the inductance component of the measuring coil 11 obtained from the AC voltage appearing at the connection midpoints 23 and 24 of the inductance bridge 10, and the horizontal axis indicates time.
[0041]
Symbol c₁Is a curve connecting measured values when the substrate is not brought close to the measuring coil 11 (the value on the right vertical axis), and c₂Is a curve connecting measured values when a substrate having a conductive thin film having a certain thickness is brought close to the measuring coil 11 (value on the left vertical axis).
[0042]
Thus, it can be seen that the magnitude of the inductance component of the measuring coil 11 changes regardless of the presence or absence of the substrate.
[0043]
The true value of the inductance component of the measuring coil 11 is L₀, Drift amount due to time change is L_driftWhen the change amount of the inductance component due to the influence of the eddy current generated in the conductive thin film is ΔL, the magnitude L of the inductance component of the measuring coil 11 when there is no influence of the eddy current.₁And the magnitude L of the inductance component when there is an influence of eddy current₂Is
L₁ = L₀+ L_drift
L₂ = L₀+ L_drift+ ΔL
It becomes.
[0044]
Immediately before measuring the film thickness of the conductive thin film by the inductance bridge 10, first, when the AC voltage between the connection midpoints 23 and 24 is measured in a state where the substrate is not brought close to the measuring coil 11, the voltage becomes the drift amount L_driftNext, when the substrate is immediately brought close to the measuring coil 11 and the AC voltage between the connection midpoints 23 and 24 is measured, the AC voltage is L_driftThe size of + ΔL is shown. Therefore, the drift amount L is calculated by subtracting these two measured values._driftIs deleted, and the magnitude of the change ΔL is obtained.
[0045]
In this subtraction, after subtracting the measured value of the AC voltage appearing at the connection midpoints 23 and 24, it may be converted into the change amount ΔL of the inductance component,_driftAnd drift amount L_driftAfter converting to the sum of + change amount ΔL, the change amount ΔL may be obtained by subtraction.
[0046]
As described above, the drift amount L_driftIs deleted, an accurate change amount ΔL is obtained. Not only when measuring conductive thin films with unknown film thickness, but also when creating a database, the drift amount L_driftIt is preferable to measure the accurate change amount ΔL.
[0047]
DETAILED DESCRIPTION OF THE INVENTION
The method of the present invention will be described with reference to the drawings.
[0048]
The code | symbol 40 of Fig.1 (a) has shown the storage chamber of the film thickness measurement mechanism. A substrate transfer robot 41 is disposed in the storage chamber 40. The substrate transfer robot 41 has a bendable arm 43 and a hand 42 attached to the tip of the arm 43. The arm 43 is configured to be foldable. When the bending of the arm 43 is controlled by a motor (not shown), the arm 43 extends and contracts in a horizontal plane. Due to the expansion and contraction of the arm 43, the hand 42 is moved in the horizontal plane.
[0049]
A film thickness sensor 7 and a distance measuring device 9 are attached to the ceiling of the storage chamber 40. FIG. 1B shows a state in which the arm 43 is extended and the hand 42 is stationary at a position below the film thickness sensor 7.
[0050]
An inductance bridge 10 shown in FIG. 2 is built in the film thickness sensor 7.
As described above, the inductance bridge 10 includes the measurement coil 11, the reference coil 12 connected in series to the measurement coil 11, and the first and second reference resistors 14 and 15 connected in series to each other. ing. The series connection circuit of the measurement coil 11 and the reference coil 12 and the series connection circuit of the first and second reference resistors 14 and 15 are configured to be connected in parallel to each other at the parallel connection points 21 and 22.
[0051]
A measuring device 8 is disposed outside the storage chamber 40.
An AC voltage source 26 and a measurement circuit 27 are arranged in the measuring device 8, and the parallel connection points 21 and 22 are connected to the AC voltage source 26 and configured to apply an AC voltage. Yes.
[0052]
A connection midpoint 23 where the measurement coil 11 and the reference coil 12 are connected to each other and a connection midpoint 24 where the first and second reference resistors 14 and 15 are connected to each other are connected to the measurement circuit 27. When an AC voltage is applied to the inductance bridge 10, the AC voltage appearing at the connection midpoints 23 and 24 is measured by the measurement circuit 27.
[0053]
The measurement coil 11 and the reference coil 12 are arranged in the film thickness sensor 7 such that the measurement coil 11 is positioned below and the reference coil 12 is positioned above the measurement coil 11 as shown in FIG. Yes.
[0054]
Accordingly, when the hand 42 is stationary at a position below the film thickness sensor 7, the measurement coil 11 is close to the hand 42, and the reference coil 12 is positioned farther from the hand 42 than the measurement coil 11. It has become.
[0055]
In this state, when an AC voltage is applied to the inductance bridge 10, the drift amount L is between the connection midpoints 23 and 24 even when the inductance bridge 10 is balanced in advance._driftAC voltage corresponding to
This drift amount L_driftIs obtained by the measuring circuit 8 and stored.
[0056]
Next, as shown in FIG. 1C, the substrate 5 is placed on the hand 42, and the substrate 5 is moved to a position directly below the measurement coil 11 and the distance measuring device 9 to be stationary.
[0057]
The substrate 5 includes a substrate body 30 made of a semiconductor wafer such as silicon, plate-like glass, and the like, and a conductive thin film (for example, a copper thin film) 31 formed on the surface of the substrate body 30.
[0058]
The substrate 5 is disposed on the hand 42 with the conductive thin film 31 facing upward. Therefore, the measurement coil 11 is located closer to the conductive thin film 31 than the reference coil 12.
[0059]
Since the substrate 5 is warped and distorted, the distance W between the surface of the substrate 5 and the distance measuring device 9 is not constant even if the distance between the hand 42 and the measuring coil 11 is constant.
[0060]
The distance measuring device 9 is a device that irradiates a measurement object with laser light and measures the distance between the reflected light and the measurement object. Laser light is emitted to the surface of the conductive thin film 31 of the substrate 5 to determine the distance between the distance measuring device 9 and the conductive thin film 31, and from the difference in height between the distance measuring device 9 and the measuring coil 11, the measuring coil 11. And the distance W between the conductive thin film 31 can be obtained.
[0061]
Since the distance W between the conductive thin film 31 and the measurement coil 11 varies in the plane of the substrate 5, the substrate 5 is moved horizontally, and the portion where the distance W of the substrate 5 is measured is positioned directly below the measurement coil 11. .
[0062]
In this state, when an AC voltage is applied to the inductance bridge 10 to generate an eddy current in the conductive thin film 31 and the AC voltage appearing between the connection midpoints 23 and 24 is measured, the drift amount of the inductance component of the measuring coil 11 L_driftAnd the total amount of change ΔL of the inductance component of the measuring coil 11 due to the influence of the eddy current is obtained.
[0063]
Drift amount L_driftAnd the amount of change ΔL, the previously calculated drift amount L_driftIs subtracted, the amount of change ΔL is obtained.
[0064]
When the change ΔL and the measured distance W are collated with a database and a corresponding cubic spline curve is obtained, the film thickness D of the conductive thin film 31 can be obtained accurately from the cubic spline curve.
[0065]
Note that the stored data in the database used at this time is that the AC voltage between the connection points 23 and 24 is first measured without the influence of the eddy current, and then the distance W And the AC voltage between the connection points 23 and 24 is measured, and the drift amount L_drift, And an accurate change amount ΔL is used.
[0066]
As described above, in the present invention, the distance W between the conductive thin film 31 and the measuring coil 11, the film thickness D of the conductive thin film 31, and the change amount ΔL of the inductance component are measured in advance and used as a database. Therefore, the film thickness D can be obtained by measuring the distance W and the change amount ΔL.
If the distance W is constant, the film thickness D can be obtained simply by measuring the change ΔL.
[0067]
In the above embodiment, the drift amount L is not affected by the eddy current._driftAfter measuring, the measurement object is actually brought close to the measurement coil 11 and the drift amount L_driftAnd the amount of change ΔL were measured, but conversely, the drift amount L_driftAnd the amount of change ΔL, the drift amount L_drift, Drift amount L_driftThe value of may be deleted.
[0068]
Although the distance between the conductive thin film 31 and the measuring coil 11 has been measured using a laser as described above, the present invention is not limited thereto. For example, the film thickness sensor 7 may be provided with an electrode, and a capacitance component formed between the electrode and the conductive thin film 31 may be measured to determine the distance W between the measurement coil 11 and the conductive thin film 31. .
[0069]
When determining the distance by measuring the capacitance component, the film thickness can be measured by the film thickness sensor 7 without moving the substrate 5 in the same part as the distance measured, and therefore the distance W can be accurately determined.
[0070]
In short, in the present invention, when the distance between the substrate 5 and the measuring coil 11 fluctuates, it is only necessary to obtain the actual distance W and is not limited by the method.
[0071]
In the above description, when measuring the change amount ΔL of the inductance component, the substrate 5 to be measured is arranged on the hand 42 of the substrate transport robot 41. However, the film thickness measuring method of the present invention is limited to this. Is not to be done.
[0072]
For example, the substrate can be placed on a stage fixed in a film forming apparatus or an etching apparatus, and the film thickness of the conductive thin film can be measured during the growth of the conductive thin film or during the etching of the conductive thin film.
[0073]
For example, reference numeral 50 in FIG. 7 denotes a vacuum processing apparatus. Here, a sputtering apparatus is shown as an example of the vacuum processing apparatus 50.
[0074]
The vacuum processing apparatus 50 includes a vacuum chamber 51, and a table 52 is disposed on the bottom wall. A hole 60 is provided on the surface of the table 52, and the film thickness sensor 7 is disposed in the hole 60.
[0075]
Within the hole 60, the measurement coil 11 is disposed at a position on the surface side of the table 52, while the reference coil 12 is disposed at a position below the measurement coil 11.
[0076]
In the film thickness sensor 7, the above-described inductance bridge 10 is configured, and the inductance bridge 10 is connected to a film thickness measuring device 8 disposed outside the vacuum chamber 51.
[0077]
A cathode electrode 55 is attached to the upper portion of the vacuum chamber 51 via an insulator 54, and a target 56 made of a conductive material is disposed on the surface of the cathode electrode 55 facing the bottom surface of the vacuum chamber 51. .
[0078]
In the table 52, an electrostatic adsorption electrode 62 is provided.₁62₂Is disposed, the substrate 5 is disposed on the table 52 with the conductive thin film 31 facing the target 56 side, and the electrostatic adsorption electrode 62 is disposed.₁62₂When a positive and negative DC voltage is applied to the substrate 5, the substrate 5 is electrostatically attracted to the surface of the table 52.
[0079]
The measurement coil 11 is fixed at a position close to the substrate 5 in a non-contact manner in the hole 60. When the substrate 5 is electrostatically adsorbed on the table 52, the measurement coil 11, the conductive thin film 31, Is a size obtained by adding the thickness of the substrate body 30 to the distance between the measurement coil 11 and the back surface of the substrate 5 (the surface of the substrate body 30).
[0080]
First, the drift amount L with no substrate placed on the table 52_driftNext, the substrate 5 having the conductive thin film 31 having a known film thickness D is immediately placed on the table 52 (the conductive thin film 31 is directed toward the target 56), and is electrostatically adsorbed. The amount of change ΔL of the inductance component with respect to the film thickness D is measured in advance.
[0081]
Since the thickness of the substrate body 30 is known, the distance W between the conductive thin film 31 and the measuring coil 11 is also known. Therefore, even if the distance W is not measured, the change amount of the film thickness D and the inductance component A database is created from the relationship with ΔL.
[0082]
In the actual thin film formation step, the drift amount L is set before placing the substrate on the table 52 in a state where the vacuum chamber 51 is in a vacuum atmosphere._driftThen, while maintaining the vacuum atmosphere, the substrate body 30 to be deposited is placed on the table 52, and the sputtering gas is introduced into the vacuum chamber 51 with the substrate body 30 electrostatically adsorbed on the table 52. Then, the target 56 is sputtered, and the conductive thin film 31 is grown on the surface of the substrate body 30.
[0083]
During the growth of the conductive thin film 31, an AC voltage is applied to the inductance bridge 10, and the drift amount L_driftAnd the amount of change ΔL is measured, and the drift amount L obtained in advance_driftIs used to calculate the change amount ΔL. If the thickness of the substrate main body 30 is the same as the thickness of the substrate main body 30 of the substrate 5 used when the database was created, there is no need to measure the distance W, and the growth from the change ΔL and the stored data in the database. The film thickness D of the conductive thin film 31 on the way can be obtained.
[0084]
As described above, when the film thickness sensor 7 is arranged in the base 52 of the vacuum processing apparatus 50, the film thickness D of the conductive thin film 31 during the growth can be measured.
[0085]
Therefore, when the conductive thin film 31 is grown while repeatedly measuring the film thickness D, it can be accurately detected that the film thickness D of the conductive thin film 31 has reached a predetermined value. And if sputtering is complete | finished at that time, the conductive thin film 31 with a sufficient film thickness precision will be obtained.
[0086]
In addition, the code | symbol 61 of FIG. 7 is a heating apparatus, and can also heat the board | substrate 5 during sputtering. In this case, the database is preferably prepared at the same temperature as the temperature of the stage 52 when the conductive thin film is actually grown.
[0087]
The vacuum processing apparatus 50 is a sputtering apparatus. However, the present invention is not limited to the sputtering apparatus. In addition to an apparatus for growing a conductive thin film such as a CVD apparatus or a vapor deposition apparatus, a conductive thin film such as an etching apparatus. The present invention can also be applied to an apparatus for reducing the film thickness.
[0088]
When applied to an etching apparatus, the film thickness D can be measured during the etching of the conductive thin film 31, so that the end point can be detected accurately.
[0089]
Further, the present invention is not limited to an apparatus that performs processing in a vacuum atmosphere. That is, the film thickness can be measured in a vacuum atmosphere, used for an apparatus for forming or etching a film in an air atmosphere or a pressurized atmosphere, or the film thickness can be measured under atmospheric pressure or under pressure.
[0090]
The conductive thin film that can be measured according to the present invention is not limited to the one exposed on the surface of the substrate 5. For example, even when an insulating thin film is further formed on the surface of the conductive thin film 31 formed on the surface of the substrate body 30, the measurement can be performed. In this case, the distance W between the conductive thin film 31 and the measuring coil 11 may be directly measured, or the distance between the insulating thin film on the surface of the conductive thin film and the measuring coil 11 is measured, and the insulating thin film The distance W between the conductive thin film 31 and the measuring coil 11 may be obtained indirectly by subtracting the film thickness.
[0091]
In the above example, the film thickness D is obtained by performing cubic spline interpolation using stored data and measurement results in the database. However, the interpolation method is not limited to this, and other approximate curves may be used. Good. In short, any interpolation method can be used as long as the unknown film thickness D can be obtained with high precision from the distance W of the value not stored in the database, the change amount ΔL, and the recording data.
[0092]
【The invention's effect】
According to the method of the present invention, the drift amount L of the inductance component_driftTherefore, accurate film thickness measurement can be performed.
In addition, since the film thickness D can be obtained from an approximate curve by collating with a database prepared in advance, even if the distance W varies, it is necessary to move the substrate or the measurement coil to make the distance W constant. Absent.
[Brief description of the drawings]
FIGS. 1A to 1C are diagrams for explaining the procedure of the method of the present invention.
FIG. 2 is a diagram for explaining the measurement principle of the method of the present invention.
FIG. 3 is a diagram for explaining the relative positional relationship between a measurement coil and a reference coil;
FIG. 4 is a graph in which measured values constituting a database are plotted with a change amount ΔL of an inductance component with respect to a distance W.
FIG. 5 is a graph in which the film thickness D of the same measured value is related to the change amount ΔL of the inductance component.
FIG. 6 is a graph for explaining the change over time in the value of the inductance component;
FIG. 7 shows an example of a vacuum processing apparatus that can use the method of the present invention.
FIG. 8 shows an example of measuring the film thickness distribution in the substrate surface (1).
FIG. 9 shows an example of measuring the film thickness distribution in the substrate surface (2).
FIG. 10 shows an example of measuring the film thickness distribution in the substrate surface (3).
FIG. 11 is a diagram for explaining a film thickness measuring method using a stylus type film thickness meter.
[Explanation of symbols]
10 …… Inductance bridge
11 …… Measurement coil
12 …… Reference coil
14, 15 ... Reference resistance
31 …… Conductive thin film

Claims (3)

Using an inductance bridge in which a circuit in which a reference coil and a measurement coil are connected in series and a circuit in which two reference resistors are connected in series are connected in parallel,
The conductive thin film is disposed closer to the measurement coil than the reference coil, and an AC voltage is applied to the inductance bridge to generate an eddy current in the conductive thin film, which is an output terminal of the inductance bridge A first step of measuring a voltage appearing between the connection midpoints;
A film thickness measuring method for obtaining a film thickness of the conductive thin film from a voltage appearing between the connection midpoints,
A second step of the conductive thin film by applying an AC voltage to the inductance bridge with no closer to the measuring coil and the reference coil, measures the AC voltage that appears between the connection point of the series connection circuit,
A distance measuring step for measuring a distance between the measuring coil and the conductive thin film;
Have
In advance, record the difference between the measurement results of the first and second steps and the measurement result of the distance measurement step as a database, using a reference conductive thin film with a different known film thickness as the conductive thin film,
The first and second steps and the distance measurement step are performed using the measurement conductive thin film as the measurement object as the conductive thin film, and the difference between the measurement results of the first and second steps and the distance measurement are performed. Check the measurement results of the process against the database,
A method for measuring a film thickness of the conductive thin film.   The film thickness measurement method according to claim 1, wherein the first step is performed immediately before or after the second step. A claim 1 or any one thickness measuring method according to claim 2 for detecting a change in thickness of the conductive thin film, the first step is in the film thickness change of the conductive thin film A film thickness measurement method performed twice or more.

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