JP2013011545A - Deposition device and film thickness measurement method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a deposition device capable of obtaining a proper film thickness value even when a measured value of resonant frequency suddenly changes due to a sharp rise of temperature or other cause.SOLUTION: When the measured value of the resonant frequency sharply changes at the beginning a film forming as indicated with Lin the figure, the measured value up to a predetermined recovery time is determined as abnormal value. After the recovery time has passed, an "inclination a" and a "y-intercept b" of a linear expression representing a relationship between the time and the resonant frequency are calculated from minimum number of normal measured values. Based on the calculated linear expression, a thickness of the thin film which grows during the recovery time is calculated and is added to the film thickness obtained from a measured value obtained after the recovery time. Since the film thickness value during the abnormal value is added, a film thickness value smaller than an actual value is prevented from being output. Also when an abnormal value is output during a normal state, the film thickness during the abnormal value is calculated from the linear expression and is added to a film thickness obtained from normal measured value.

Description

  The present invention relates to the technical field of measuring a thin film during film formation.

  Thin film formation using a vacuum atmosphere includes sputtering methods and vapor deposition methods. When a thin film grows on the surface of a film formation target such as a substrate, a crystal is used to measure the thickness of the growing thin film. A vibrator is used.

The thin film is formed by the vapor emitted from the vapor deposition source and the sputtered particles emitted from the sputter source reaching and adhered to the surface of the film formation target, and the vapor and the sputtered particles reach the surface of the film formation target. In this case, the thickness of the thin film formed on the surface of the crystal resonator is measured from the change in the resonance frequency of the crystal resonator so as to reach the crystal resonator. In other words, the thickness of the thin film on the surface of the film formation target is obtained.
However, if there is a sudden increase in frequency when a large thermal shock is applied to the crystal unit or abnormal data output such as an unknown frequency jump, the thickness of the substrate surface cannot be calculated accurately. There is an inconvenience.

JP-A-11-222670

  The present invention was created to solve the above-described disadvantages of the prior art, and an object of the present invention is to provide a technique capable of correcting the abnormal data and calculating the correct film thickness.

In order to solve the above-described problems, the present invention provides a film forming object and a crystal resonator in a vacuum atmosphere, and a thin film is formed on the film forming surface of the film forming object and the detection surface of the crystal resonator. And measuring the resonance frequency of the crystal resonator, and determining the thickness of the thin film grown on the film formation surface from the measurement result, wherein the thin film is formed on the detection surface A value that can be determined that a first linear relationship is formed between the value of the resonance frequency and the measurement time when a sudden increase in the value of the resonance frequency is detected when arrival is started from a state in which the fine particles do not reach After the resonance frequency is measured, the film thickness of the thin film on the detection surface is in accordance with the first linear relationship from the time when the microparticles reach the film formation surface to a desired time. As it increased, it grew on the film formation surface from the measurement result. A film thickness measuring method for determining the thickness of the serial film.
In the present invention, when the measured resonance frequency value changes while maintaining the first linear relationship with respect to the measurement time, the measured resonance frequency value changes suddenly and the first If it is determined that the linear relationship is no longer maintained, the first linear relationship before the sudden change is maintained even after the sudden change occurs, and after the sudden change starts, Film thickness measurement for obtaining the film thickness of the thin film after the start of the sudden change by calculating the film thickness increase amount of the thin film growing on the film formation surface from the first linear relationship and the measurement time after the sudden change Is the method.
Further, according to the present invention, when it is determined from the measurement result of the resonance frequency after the sudden change that the sudden change has been resolved, the time after the time when the measurement result of the resonance frequency that has been determined to eliminate the sudden change is obtained. From the measurement result of time, the second linear relationship is obtained, and the elapsed time of the measurement result from the value of the film thickness of the thin film on the film formation surface obtained from the measurement result obtained from the second linear relationship. And a value obtained by subtracting the value of the film thickness of the film formation surface obtained from the first linear relationship to the value of the film thickness of the film formation surface obtained from the linear result. is there.
In addition, the present invention assumes that the second linear relationship before the sudden change is maintained when the sudden change occurs after the second linear relationship is obtained, and that the composition is obtained from the measurement result. This is a film thickness measurement method for determining the film thickness of the thin film on the film surface.
The present invention also provides a vacuum chamber in which a film formation target is disposed, a vacuum exhaust device that evacuates the vacuum chamber, and a film formation of the film formation target in a vacuum atmosphere disposed in the vacuum chamber. A film forming source that allows a thin film material to reach the surface; and a crystal resonator disposed at a position that does not prevent the thin film material from reaching the film forming surface in the vacuum chamber; and is connected to the crystal resonator, A measurement device for measuring the resonance frequency of the crystal resonator; and a computer connected to the measurement device to which the resonance frequency is input, the computer forming a thin film on the detection surface. When a sudden increase in the value of the resonance frequency is detected when arrival starts from a state where particles do not reach, after determining that a linear relationship has been formed between the measurement value of the resonance frequency and the measurement time, the minute frequency From the time when the particles reach the film formation surface, Until Nozomu time, the film thickness of the thin film on the detection surface is configured evaporation apparatus to determine a thickness of the thin film grown on the deposition surface as increased with the linear relationship.

  Even if an abnormal measurement value is output at the start of film formation, after the measured value transition returns to a normal state, the growth thickness of the thin film while the measurement value that cannot be used as an abnormal value is output is displayed. Since it can be calculated, the thickness of the thin film to be formed is not calculated to be small.

  Moreover, even if the measured value shows an abnormal value after the linear relationship is formed, the film thickness increase amount can be obtained from the linear relationship while the abnormal value is occurring, so the film thickness is calculated to be small. There is nothing.

An example of a thin film forming apparatus to which the present invention can be used Graph to explain the sudden rise in resonance frequency at the start of thin film formation Graph for explaining the state when the measured value of resonance frequency suddenly changes and returns

FIG. 1 shows a film forming apparatus 10 of the present invention, and the film forming apparatus 10 has a vacuum chamber 11.
A substrate holder 13 is disposed inside the vacuum chamber 11, and a film formation target 16 is disposed on the substrate holder 13.

  A film formation source 17 is disposed at a position facing the film formation target 16 in the vacuum chamber 11. A thin film material, which is a substance for forming a thin film, is arranged inside the film forming source 17, and the thin particles of the thin film material are configured to be discharged into the vacuum chamber 11.

A crystal resonator 15 is disposed on the side of the substrate holder 13 in the vacuum chamber 11. The quartz crystal resonator 15 is disposed at a position where the fine particles of the thin film material facing the film formation target 16 facing the film formation source 17 are not shielded.
A shutter 19 is provided in the vicinity of the opening from which the fine particles of the film forming source 17 are discharged so as to cover the opening.

A vacuum evacuation device 29 is connected to the vacuum chamber 11, and the vacuum evacuation device 29 is operated to evacuate the vacuum chamber 11 to form a vacuum atmosphere at a predetermined pressure. Release fine particles of material.
Here, the film forming apparatus 10 is a vapor deposition apparatus, and the fine particles are vapors of a thin film material. For example, when the film forming apparatus 10 is a sputtering apparatus, the fine particles are sputtered particles of the thin film material. Fine particles other than particles are also included in the present invention.

Here, the thin film material placed in the film forming source 17 is heated to start the discharge of the thin film material in a vapor state, and when the vapor discharge is stabilized, the shutter 19 is opened.
The film formation target 16 has a film formation surface 21 that faces the film formation source 17, and the crystal unit 15 has a detection surface 22 that faces the film formation source 17.

  The vapor of the thin film material released from the film formation source 17 reaches both the film formation surface 21 and the detection surface 22 and grows a thin film on both the film formation surface 21 and the detection surface 22. In this example, the thin film material is heated to release the vapor of the thin film material into the vacuum chamber 11 to reach the film formation surface 21 and the detection surface 22. The sputtering gas introduced into the vacuum chamber 11 is formed into plasma, the target is sputtered, and the sputtering particles composed of the thin film material reach the film formation surface 21 and the detection surface 22. It suffices for the fine particles to reach the film formation surface 21 and the detection surface 22.

  A measuring device 25 is disposed outside the vacuum chamber 11, and the crystal resonator 15 is connected to the measuring device 25. The measuring device 25 continuously measures the resonance frequency of the crystal resonator 15 at a predetermined time. Has been. The measurement intervals between the predetermined times may be equal intervals or may be non-equal intervals according to mathematical formulas or stored contents.

  The measuring device 25 is connected to a computing device 26 composed of a computer or the like, and a measured value that is a resonance frequency continuously measured by the measuring device 25 is output to the computing device 26. An arithmetic device 27 is arranged in the calculation device 26, and calculation and determination are made by the arithmetic device 27. From the measurement result including the input measurement value and the measurement time, the crystal unit 15 The film thickness of the thin film on the detection surface 22 is obtained, and the film thickness value of the thin film on the detection surface 22 is converted into the film thickness value of the thin film on the film formation surface 21 based on a preset film thickness relationship. From two or more measurement results (measurement value and measurement time of the measurement value), the film thickness increase amount of the thin film grown between the measurement results is obtained, and the film obtained before the measurement result for obtaining the film thickness increase amount The latest film thickness is obtained by adding the increase in film thickness to the thickness.

  The calculation device 26 can know the measurement time of the measurement value of the input resonance frequency, and calculates and sets the growth rate of the thin film on the film formation surface 21 from the converted film thickness value and measurement time. The vapor deposition rate can be controlled by controlling the film formation source 17 so that the growth rate is within a predetermined range including the reference value as compared with the reference value thus obtained. Yes.

When there is no change in the vapor release rate of the film forming source 17 and the vapor release rate is a constant value, a linear relationship that is a linear expression is formed between the resonance frequency and the measurement time, and when the linear relationship is maintained, The film formation rate is a constant value because it has a linear relationship.
On the other hand, the measured value of the resonance frequency of the crystal unit 15 is affected by factors other than the film thickness change such as heat and pressure fluctuation in the vacuum chamber 11.

  In the crystal resonator 15 of the film forming apparatus 10, the room temperature is maintained without being heated before the shutter 19 is opened, whereas the fine particles of the thin film material are at a high temperature. When the fine particles reach the detection surface 22 and the film formation surface 21, the crystal resonator 15 and the film formation target 16 are heated.

  Since the crystal resonator 15 releases heat from the attachment part to the holding device or the like, the temperature rise rate gradually decreases even if fine particles reach continuously, but the temperature when the shutter 19 is opened is low. Since the rise is large, the measurement result when the shutter 19 is opened is greatly affected.

In the graph of FIG. 2, the horizontal axis indicates a measurement time that is a time from the reference time with a predetermined time before the start of film formation, and the vertical axis indicates the value of the measured resonance frequency. A symbol L ₁ in the figure is a curve connecting the measured values of the resonance frequency at the measurement time, and shows a case where the measured value of the resonance frequency suddenly increases when the shutter 19 is opened. The symbol t ₀ indicates the start time when the thin film growth is started by opening the shutter.

According to this curve L ₁ , the measured value of the resonance frequency rapidly increases due to a rapid temperature rise, and then the rate of temperature rise decreases, and the influence of the thin film growth on the detection surface 22 is affected by the change in the resonance frequency. It becomes dominant and the resonance frequency is lowered. After the decrease starts, a linear relationship is formed between the measured value of the resonance frequency and the time.

From the start time t ₀ of the thin film formation to the time when the resonance frequency recovers to the value of the start time t ₀ and the linear relationship is formed, when the film thickness is obtained according to this curve L ₁ , The film thickness of the formed thin film becomes zero, and the film thickness based on the measured value is smaller than the actual value.
When the shutter 19 is opened, the arrival is started from the state in which the fine particles forming the thin film do not reach the detection surface 22.

In the vapor deposition method, the fine particles are vapor of a thin film material, and in the sputtering, the fine particles are sputtered particles of the thin film material constituting the target.
When the temperature of the crystal unit 15 suddenly increases due to the arrival of fine particles on the detection surface 22, the temperature of the crystal unit 15 also increases rapidly.

A control procedure is stored in the storage device 28 in the calculation device 26, and the calculation device 27 of the calculation device 26 connected to the measurement device 25 follows the calculation procedure stored in the storage device 28 as follows. To work.
A clock is provided in the measuring device 25 so that the measurement time when the resonance frequency is measured can be known. When the film formation is started, the measurement value of the resonance frequency and the measurement time of the measurement value are stored. It is stored in the device 28.

  On the crystal unit 15, the thickness of the thin film formed on the detection surface 22 and the amount of change in the resonance frequency are in a proportional relationship, and when the growth rate of the thin film is a constant value, the measurement time and measurement of the resonance frequency are performed. A linear expression is established between the values and is in a linear relationship.

Here, there is a linear relationship between the elapsed time x from a predetermined reference time (x = measurement time−reference time), and the following linear expression between the resonance frequency value y,
y = a * x + b (1)
Is established, the value of “slope a” and the value of “y intercept b” in the above equation (1) are obtained from the measurement time of the resonance frequency and the value of the resonance frequency by the least square method.

Since the resonance frequency of the crystal unit 15 decreases as the thickness of the thin film formed on the detection surface 22 increases, the resonance frequency does not increase when the thin film is growing.
When the calculation device 26 detects an increase in the resonance frequency exceeding a predetermined allowable increase value, the calculation device 26 determines that there is a rapid increase in temperature, classifies the measured value as an abnormal value, and calculates the least square method. Excluded from the range of measured values used for calculation so that they are not used.

  In this example, the recovery time required until the measurement time and the measured value have a linear relationship is known in advance after the resonance frequency is increased due to a rapid rise in temperature, and when an abnormality due to a sudden increase in the resonance frequency is detected, it is stored in advance. When the recovery time thus set elapses, it is assumed that a linear relationship is established, and the measured value of the resonance frequency measured after the recovery time elapses is stored as normal.

  In addition, if it is detected that a linear relationship is established between the measurement time and the measured value for a plurality of measured values close to the measurement time of the latest measured value among the obtained measured values, the measured value for which the linear relationship is established May be stored as normal.

The storage device 28 stores the minimum number of measurement values used when calculating the equation (1). In any case, after the linear relationship is established, the minimum number of resonance frequencies are continuously measured. When the minimum number of normal measurement values are obtained, “slope a” and “y intercept b” in equation (1) are calculated by the method of least squares.
The start time t ₀ when the measured value changes according to the expression (1) from the expression (1) having the calculated “slope a” and “y intercept b” and the value indicating the time of the start time t _0. The resonance frequency f ₀ is obtained.

Then, the values of and start time t ₀ to at resonant frequency f ₀ of the starting time t _0, the normal measured value and the value of the measurement time, a normal measured value from the start time t ₀ is obtained The initial film thickness of the thin film grown up to the measurement time can be calculated according to equation (1).
When the time from the start time t ₀ to the measurement time when a normal measurement value is obtained is the recovery time, the initial film thickness of the thin film grown during the recovery time is calculated.

  When the initial film thickness is added to the film thickness after the normal measurement value is obtained, the film thickness of the thin film grown from the start time to the current measurement time can be calculated. The calculated film thickness is the same value as when no abnormal measurement value due to a sudden change in temperature is detected, and is the value when there is no sudden change in the resonance frequency.

Next, a processing procedure when an abnormal measurement value is obtained from a state where a normal measurement value is obtained will be described. In this case, it is assumed that the minimum number of normal measurement values have already been obtained, and “slope a” and “y intercept b” in equation (1) have been calculated. Note that the “inclination a” and “y intercept b” already calculated here include the linear relationship obtained after recovery from the rapid temperature rise (first linear relationship).
When it is determined that the linear relationship is formed, when a new measurement result is obtained, the calculation device 26 firstly calculates a value between the measurement value in the measurement result and the already obtained equation (1). It is determined whether or not the error that is the absolute value of the difference and the error value that is the absolute value of the difference from the immediately preceding measurement value are less than or equal to the allowable error stored in advance.

  When the error value is equal to or less than the allowable error, it is determined that the measurement value having the error is normal, and in addition to the measurement value used for calculation as the latest measurement value, “slope a” and “y intercept b” And recalculate.

  In the storage device 28, an integer value equal to or greater than the minimum number is stored as a calculated number. After the number of measured values used for calculation reaches the calculated number, the latest normal measured value is obtained. The measurement value is added to the measurement value used for the calculation, and the measurement value at the oldest measurement time is excluded from the measurement values used for the calculation among the measurement values used for the previous calculation. As a result, a constant calculated number is maintained, and the “slope a” and “y intercept b” in the equation (1) are calculated according to the calculated number of measured values including the latest measured value and the measurement time corresponding to these measured values. And calculate.

  If the error value between the latest measurement value and the previously calculated equation (1) or the difference from the previous measurement value is not within the allowable error, immediately before the “slope a The value of the resonance frequency is calculated based on the equation (1) for determining “and“ y intercept b ”and the measurement time, the film thickness is calculated from the calculated resonance frequency, and not the film thickness determined from the abnormal measurement value. The film thickness obtained from the measurement time and the equation (1) is defined as the film thickness at the measurement time. Therefore, an abnormal measurement value is output to the film thickness obtained from the normal measurement value (here, the value obtained by adding the initial film thickness to the film thickness obtained from the measurement value). The time during which the measured value is output and the corrected film thickness value obtained by equation (1) are added. As a result of removing the abnormal value, the film thickness value is interrupted and is smaller than the actual value. No film thickness value is output.

Measurement is continued at each set measurement time or at a specified interval while abnormal measurement values are being measured, and the difference between the measurement value and the previous measurement value is predetermined when the measurement value error is within the allowable error. When it becomes smaller than the value, it is determined that the abnormal situation has ended, and the measured value returns to a normal value.
Then, after the time when the measured value that was determined to have returned to normal after the abnormality was resolved, the increase in film thickness obtained from the measured value and the measured time is the film thickness immediately before the abnormal measured value is measured. The current film thickness is obtained by adding the corrected film thickness value to the added film thickness. Then, after the cancellation time, when the number of measured values reaches the minimum number or the calculated number, “slope a” and “y intercept b” are recalculated to obtain a new linear relationship (second linear relationship). .

  It should be noted that the film thickness while the abnormal value is output is calculated by the equation (1) having “slope a” and “y intercept b” after returning to the normal measurement value, and from the normal measurement value You may add to the calculated | required film thickness.

In the graph of FIG. 3, the horizontal axis is the measurement time indicating the time from the reference time with the predetermined time as the reference time, and the vertical axis indicates the film thickness of the thin film on the film formation surface 21 obtained from the resonance frequency. ing. A symbol L ₂ in the figure indicates a state in which the film thickness obtained from the measurement value and the measurement time change according to a linear relationship. In the graph of FIG. 3, the measured value suddenly changes from the linear relationship of the straight line L ₂ to become abnormal, and after changing according to the curve (straight line) L _{3, the} linear state recovers and changes according to the straight line L ₄ . Shows the case. A symbol t ₀ is a start time when film formation is started.

  Even after the normal measurement value is recovered once, when the error of the measurement value exceeds the allowable error, the obtained “slope a” and “y intercept b” are obtained in the same manner as the above procedure ( The resonance frequency is calculated from the equation (1) and the measurement time, and the film thickness is obtained as the resonance frequency at the measurement time. This is also performed until the measured value returns to a normal value.

As described above, according to the present invention, when an abnormality is caused by a rapid increase in temperature immediately after the thin film is formed, or when an error exceeds an allowable error from a normal state where the linear relationship is maintained, the film thickness is increased. The value of can be made uninterrupted.
Further, according to the present invention, the film thickness of the film formation surface at the cancellation time, which is the measurement time of the measurement result that determines that the sudden change has been eliminated, is the film thickness immediately before the sudden change until the sudden change is resolved after the start of the sudden change. The correction film thickness value obtained from the time of the first time and the first linear relationship can be added, and the amount of increase in film thickness after the cancellation time can be calculated from the measurement result after the cancellation time, The latest film thickness can be obtained by adding the thickness value to the obtained film thickness value.

In this case, a second linear relationship between the measurement value and the measurement time is obtained from the measurement result after the cancellation time, and after the second linear relationship is obtained, another sudden change occurs and the measurement value May become abnormal.
Assuming that the second linear relationship before such another sudden change is maintained, it has grown on the deposition surface after another sudden change from the measurement time after the second sudden change and the second linear relationship. The amount of increase in the thickness of the thin film can be obtained, and the latest film thickness can be obtained by adding to the film thickness value immediately before the sudden change.

  The film thickness of the thin film on the film formation surface 21 is obtained by converting the film thickness of the thin film on the detection surface 22, and the growth rate of the thin film on the film formation surface 21 depends on the measurement time interval and the film on the detection surface 22. The amount of increase in the thickness of the thin film material can be determined by controlling the amount of current supplied to the heating device in the film forming source 17 and the output voltage of the sputtering power source connected to the film forming source 17. The growth rate of the thin film on the film formation surface 21 can be controlled to a constant value.

  When the film thickness of the film formation surface 21 of the film formation target 16 calculated based on the output signal of the crystal unit 15 and the above equation (1) reaches a predetermined film thickness, the shutter 19 is closed, and then The release of the fine particles (vapor) of the thin film material is stopped, the film formation target 16 on which the thin film is formed is unloaded from the vacuum chamber 11, and the film formation target 16 on which the thin film is not formed is loaded into the vacuum chamber 11. Then, thin film formation is started.

DESCRIPTION OF SYMBOLS 10 ... Film-forming apparatus 11 ... Vacuum chamber 13 ... Substrate holder 15 ... Crystal oscillator 16 ... Film-forming object 17 ... Film-forming source 25 ... Measuring apparatus 26 ... Calculation apparatus 29 ... Vacuum exhaust apparatus

Claims (5)

Arranging the film formation target and the crystal resonator in a vacuum atmosphere, and growing a thin film together on the film formation surface of the film formation target and the detection surface of the crystal resonator,
A film thickness measurement method for measuring a resonance frequency of the crystal resonator and obtaining a thickness of the thin film grown on the film formation surface from a measurement result,
Detecting a sudden increase in the value of the resonance frequency when reaching the detection surface from a state in which the fine particles forming the thin film do not reach,
After the resonance frequency of a value at which it can be determined that a first linear relationship is formed between the value of the resonance frequency and the measurement time,
From the time when the fine particles reached the film formation surface to a desired time, the film thickness of the thin film on the detection surface increased according to the first linear relationship, and the film formation was performed based on the measurement result. A film thickness measurement method for obtaining the film thickness of the thin film grown on a surface. When the measured resonance frequency value changes while maintaining the first linear relationship with respect to the measurement time, the measured resonance frequency value changes suddenly and maintains the first linear relationship. If you decide that
Even after the sudden change occurs, the first linear relationship before the sudden change is maintained, and after the start of the sudden change, the first linear relationship and the measurement time after the sudden change The film thickness measuring method according to claim 1, wherein the film thickness increase amount of the thin film growing on the film formation surface is calculated to determine the film thickness of the thin film after the start of the sudden change. From the measurement result of the resonance frequency after the sudden change, when it is determined that the sudden change has been resolved, from the measurement result of the time after the time when the measurement result of the resonance frequency that has determined the cancellation of the sudden change is obtained, Find the second linear relationship
The film formation obtained from the elapsed time of the measurement result and the first linear relation from the value of the film thickness of the thin film on the film formation surface obtained from the measurement result obtained from the second linear relation The film thickness measurement method according to claim 2, wherein a value obtained by subtracting the value of the film thickness of the surface is added to the value of the film thickness of the film formation surface obtained from the linear result.   When the sudden change occurs after the second linear relationship is obtained, it is assumed that the second linear relationship before the sudden change is maintained, and from the measurement result, The film thickness measuring method according to claim 3, wherein the film thickness is obtained. A vacuum chamber in which an object to be deposited is placed;
An evacuation device for evacuating the vacuum chamber;
A film forming source that is disposed in the vacuum chamber and causes a thin film material to reach a film forming surface of the film forming object in a vacuum atmosphere;
In the vacuum chamber, a crystal resonator disposed at a position that does not prevent the thin film material from reaching the film formation surface;
A measuring device connected to the crystal resonator and measuring the resonance frequency of the crystal resonator;
A computer connected to the measuring device and receiving the resonance frequency;
The calculator detects a sudden rise in the value of the resonance frequency when reaching the detection surface from a state in which the fine particles forming the thin film do not reach,
After determining that a linear relationship is formed between the measurement value of the resonance frequency and the measurement time,
From the time when the microparticles reach the film formation surface to a desired time, the film thickness of the thin film on the detection surface is increased according to the linear relationship, and the thin film grown on the film formation surface A vapor deposition device configured to determine the thickness.

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