JP6263441B2 - Thickness control method by crystal oscillation type film thickness monitor - Google Patents

Description

  The present invention relates to a film thickness control method using a crystal oscillation type film thickness monitor, and relates to a technique for correcting an error between a film thickness measured by a crystal resonator and an actual film thickness on a substrate.

  A film thickness meter (film thickness monitor) is used to control (manage) the film thickness and film forming rate (rate) in a film forming apparatus that forms a thin film by depositing a film forming material on a substrate by vapor deposition or sputtering. In this case, a crystal oscillation type film thickness monitor using a crystal resonator method is widely used.

  This crystal oscillation type film thickness monitor uses the fact that a quartz resonator serving as a measurement unit is provided in the film forming chamber, and that when the film forming material adheres to this crystal resonator, the resonance vibration changes due to changes in its mass. Thus, for example, by measuring the change in the resonance vibration (oscillation frequency), the film thickness and the film forming speed (rate) are measured. For example, when a vacuum evaporation apparatus is used as the film forming apparatus, the measurement result is evaporated. The film thickness is managed by feeding back to the heating control device of the source and controlling the rate of the deposited thin film on the substrate to be constant.

  On the other hand, in such a crystal resonator, the thin film gradually increases with the measurement, but as the thin film on the surface of the crystal resonator becomes thicker, the resonance vibration gradually decreases. At that time, for example, as shown in FIG. 1, the film formation speed on the monitor of the crystal unit and the actual film formation rate on the substrate gradually deviate, and an accurate film thickness is obtained at the initial use of the crystal unit. Even if measurement is possible, an error occurs in the film thickness measurement as time elapses (an error occurs in the film thickness between the substrate formed in the initial stage of use and the substrate formed after the time has elapsed). .)

  As the oscillation frequency gradually decreases due to the increase in the thickness of the thin film deposited on the quartz resonator as described above, an error from the actual film thickness increases, and this needs to be corrected.

  In this regard, for example, in Patent Document 1 (Japanese Patent Application Laid-Open No. 2008-122200), a calibration crystal resonator is provided in parallel with a measurement crystal resonator to increase the film thickness of the measurement crystal resonator. In response, open the shutter of the calibration crystal unit whose thickness has not increased, measure the film thickness with this calibration crystal unit, and correct the ratio between this measurement value and the measurement value of the measurement crystal unit. A correction method for converting the film thickness by multiplying as a ratio is disclosed.

  However, it is necessary to arrange a calibration crystal unit separately from the crystal unit, and it is necessary to open the shutter in the middle of the measurement and measure with the calibration crystal unit to correct the conversion. The conversion correction is based solely on the measurement with the crystal resonator, not based on the actual film thickness of the thin film on the substrate, and the calibration crystal resonator is less deposited than the measurement crystal resonator. Also, since the film forming material is gradually deposited and the film thickness gradually increases, the correction accuracy for correcting the error is inferior, and it cannot be said that the measurement accuracy of the substrate film thickness is sufficiently improved.

  Patent Document 2 (Japanese Patent Laid-Open No. 8-82517) discloses a method of measuring and correcting the film thickness of the thin film on the substrate, but the actual film thickness between the high and low oscillation frequencies is disclosed. This is merely a method for calculating an optimal correction coefficient by the least square method, and the correction between these two points is merely based on a fixed value based on the calculation result. Thickness measurement accuracy is not enough.

JP 2008-122200 A JP-A-8-82517

  The present invention solves such a problem, and uses a pre-measurement crystal resonator before the film-forming step, and the thin film of the measurement substrate at each oscillation frequency of the pre-measurement crystal resonator is different. Measure the thickness, calculate the ratio between the target film thickness measured by the pre-measurement crystal resonator and the actual film thickness of the measurement substrate thin film measured at each oscillation frequency as the correction ratio, and form the film In the process, the film thickness or the film formation speed of the thin film of the substrate (for film formation) measured by the crystal resonator during film formation is multiplied by a correction ratio corresponding to the oscillation frequency among the respective correction ratios ( For film formation) By correcting the film thickness or film formation speed of the substrate and controlling the film thickness, the error correction accuracy is greatly improved and the film thickness measurement accuracy is greatly improved. Excellent crystal oscillation that can extend the frequency band used) And its object is to provide a film thickness control method according to film thickness monitor.

  The gist of the present invention will be described with reference to the accompanying drawings.

A crystal resonator 5 serving as a measurement unit of a crystal oscillation type film thickness monitor is provided in a film forming chamber 4 of a film forming apparatus 3 for forming a thin film by depositing a film forming material on the surface of the substrate 1. wherein a film thickness control method according to the crystal oscillator type film thickness monitor deposition material is deposited providing the film deposition apparatus 3 for measuring the thickness of the thin film formed on the substrate 1 surface, advance before film formation step Using the measurement crystal resonator, measure the film thickness of the thin film on the measurement substrate for each different oscillation frequency of the pre-measurement crystal resonator, and measure the target film thickness with the pre-measurement crystal resonator. And the ratio of the actual thickness of the thin film of the measurement substrate measured at each oscillation frequency is calculated as a correction ratio, and in the film formation process, the substrate 1 measured by the crystal resonator 5 at the time of film formation is calculated. Depending on the oscillation frequency of the above correction ratios, In corrected method of controlling the thickness of the film thickness or film forming speed of the thin film substrate 1 is multiplied by the correction ratio was,
In the pre-measurement step performed before the film-forming step, a pre-measurement crystal resonator is placed in the film-forming chamber 4 of the film-forming apparatus 3 for forming a thin film by depositing a film-forming material on the surface of the measurement substrate. The pre-measurement crystal resonator of the actual film thickness of the thin film of the measurement substrate is measured by measuring the actual thin film thickness of the measurement substrate by depositing a film forming material on the pre-measurement crystal resonator The ratio to the target film thickness measured by the calculation is calculated as the correction ratio, and the calculation of the correction ratio varies depending on the increase in the film thickness of the film forming material deposited on the pre-measurement crystal resonator. Each time the oscillation frequency changes, the measurement substrate is sequentially replaced with a different measurement substrate, and the thickness of the thin film deposited on the measurement substrate is measured n times to calculate the correction ratio for each different oscillation frequency. ,
In the film forming step, another new crystal resonator 5 is provided in the film forming chamber 4 instead of the prior measurement crystal resonator, and the correction ratio corresponding to the oscillation frequency of the crystal resonator 5 is provided. Is multiplied by the film thickness or film formation speed measured by the crystal resonator 5 and is corrected in accordance with the change in the oscillation frequency. is there.

  Since the present invention is configured as described above, the error correction accuracy is greatly improved, the film thickness measurement accuracy is greatly improved, and the use time (use frequency band) of the crystal resonator can be extended. This is a film thickness control method using an oscillation type film thickness monitor.

It is a graph which shows the oscillation frequency correlation diagram of the actual film-forming speed on the substrate with respect to the film-forming speed measured by the crystal oscillator before correction, and shows that the error increases as the film thickness increases and the oscillation frequency decreases. It is a graph to show. It is a graph which shows the frequency correlation figure of the film-forming speed | velocity | rate after a correction | amendment of a present Example, and is a graph which shows that an error correction precision increases. It is a flowchart figure which shows the procedure corrected based on the correction ratio acquired by the prior measurement process of a present Example. It is schematic structure explanatory drawing of a present Example.

  An embodiment of the present invention which is considered to be suitable will be briefly described with reference to the drawings showing the operation of the present invention.

  Before the film-forming step of forming a thin film by depositing a film-forming material on the surface of the substrate 1 (for film-forming) by the film-forming apparatus 3, the pre-measurement crystal vibrator is different. Measure the thickness of the thin film on the measurement substrate at each oscillation frequency, and measure the target film thickness with the crystal resonator for pre-measurement and the actual thickness of the thin film on the measurement substrate measured at each oscillation frequency. The ratio is calculated as a correction ratio.

  In the film formation step, the film thickness or film formation speed of the thin film (for film formation) substrate 1 measured by the crystal resonator 5 at the time of film formation, The film thickness or film formation speed of the thin film of the substrate 1 is corrected by multiplying the correction ratio according to the oscillation frequency at the time of measurement (for film formation).

  That is, for each change stage of the oscillation frequency that changes as the film thickness of the film forming material deposited on the crystal oscillator for pre-measurement of the crystal oscillation type film thickness monitor increases, for example, FIG. As shown in FIG. 4, the measurement substrate is sequentially replaced with a different measurement substrate every n stages of the oscillation frequency that gradually decreases as the film thickness of the film-forming material deposited on the pre-measurement crystal resonator increases. The film thickness of the thin film deposited on the measurement substrate is measured n times, and the correction ratios for the different oscillation frequencies are calculated and acquired. The correction ratio corresponding to the oscillation frequency at the time of measurement 5 is multiplied by the film thickness or film formation speed measured by the crystal resonator 5 to perform correction corresponding to the change in the oscillation frequency.

  Therefore, even if the error of the measured value of the crystal unit 5 from the actual film thickness gradually increases with the change of the oscillation frequency, it is not a fixed value but a measurement at each oscillation frequency (every n stages) measured in advance. Since the measured value of the crystal unit 5 is corrected by the correction ratio for each oscillation frequency obtained by comparison with the actual film thickness of the substrate for use, the error correction accuracy is extremely increased.

  Further, the pre-measurement step of measuring the actual film thickness of the thin film deposited on the measurement substrate for each of the different oscillation frequencies before the film formation step is gradually performed using the pre-measurement crystal resonator. For each oscillating frequency that changes, specifically, for each oscillating frequency, for example, by sequentially measuring the actual film thickness while replacing the substrate for sequential measurement at every number of changing stages (every n stages) Since the ratio can be easily acquired in multiple stages (n stages), and this correction ratio can be used to perform error correction using the correction ratio corresponding to the oscillation frequency of the crystal resonator 5 at the time of measurement, it is simple and efficient. The correction ratio based on the actual film thickness can be acquired in multiple stages, and this is input in advance to the error correction processing section of the crystal oscillation film thickness monitor, for example, and the correction ratio is selected according to the change in the oscillation frequency And multiply this by the measured value to correct the error. It becomes the Rukoto is easily, in which a very error correction accurately, the film thickness control method according to good crystal oscillation type film thickness monitor practical.

  Specific embodiments of the present invention will be described with reference to the drawings.

  In this embodiment, a film forming material (vapor deposition material) is evaporated from the evaporation source 2 in the film forming chamber 4 (vacuum chamber 4) and fixed to the substrate holder (for film forming) and deposited on the surface of the substrate 1 to form a thin film. A crystal oscillation type film thickness monitor is provided in the film forming apparatus (vapor deposition apparatus) 3 to control (manage) the film thickness of the substrate 1, and a crystal resonator serving as a measurement unit of the crystal oscillation type film thickness monitor 5 is provided in the vacuum chamber 4 of the vapor deposition apparatus 3, and the film thickness and film deposition rate (rate) of the substrate 1 (for film formation) by the vapor deposition apparatus 3 are measured and fed back to the heating control device 7 of the evaporation source 2. Thus, the rate is uniformly controlled, but the error between the measured value of the crystal resonator 5 and the actual film thickness is corrected by multiplying by the correction ratio, and the film thickness is managed.

  Further, the crystal oscillation type film thickness monitor according to the present embodiment has a rate based on a crystal resonator 5 as a measurement unit provided in the vacuum chamber 4 and a measurement value by the crystal resonator 5 as shown in FIG. The film thickness monitoring device 8 monitors and controls the film thickness, and the film thickness monitoring device 8 is previously measured for each oscillation frequency by the film thickness inspection device 9 (such as an ellipsometer or a stylus type surface roughness measuring device) as described above. The actual thickness of the measurement substrate is measured, and the correction ratio for each oscillation frequency is calculated in advance from the actual measurement value in the calculation unit and stored in the host controller 10 (although the calculation unit is provided as a separate mechanism). Or may be incorporated in the host controller 10.) Then, as shown in FIGS. 2 and 3, for each correction point at each oscillation frequency as a measurement point, the correction ratio calculated and acquired based on the actual film thickness measured at that point is the higher-level controller 10. The rate is kept constant by correcting the measured value by the quartz crystal resonator 5 and feeding back to the heating control device 7 for controlling the output of the power source for heating the vapor deposition source 2. It is configured to control (manage) the thickness.

  That is, as described above, in the present embodiment, the vapor deposition apparatus for forming a thin film by depositing a film deposition material (vapor deposition material) on the surface of the substrate 1 in a preliminary measurement process performed before the film deposition process (vapor deposition process). The pre-measurement crystal resonator is provided in the vacuum chamber 4 in place of the crystal resonator 5, and an evaporation material is deposited on the pre-measurement crystal resonator to form an actual thin film on the measurement substrate. The host controller measures the thickness by the film thickness inspection device 9 and calculates the ratio of the actual film thickness of the thin film of the measurement substrate to the target film thickness measured by the pre-measurement crystal resonator as the correction ratio. Keep memory in 10.

  In addition, the correction ratio is calculated and acquired n times for each change stage (measurement point) of the oscillation frequency that decreases as the film thickness of the vapor deposition material deposited on the pre-measurement crystal unit increases. The correction ratio for each different oscillation frequency is calculated, and in the vapor deposition process, the correction ratio corresponding to the oscillation frequency of the crystal resonator 5 is selected and acquired for each correction point corresponding to the measurement point. An arithmetic process that multiplies the film thickness or film forming speed measured by the quartz oscillator 5 is performed, and correction is performed in accordance with the change in the oscillation frequency.

  Specifically, the pre-measurement step of measuring the film thickness of the thin film deposited on the actual measurement substrate for each different oscillation frequency before the vapor deposition step is different for each oscillation frequency. In this step, the film thickness of the thin film deposited on the measurement substrate is measured. When the preliminary measurement is completed, another new crystal resonator 5 is formed in place of the preliminary measurement crystal resonator. It is provided in the chamber 4.

  Therefore, even if the error of the measured value of the crystal unit 5 from the actual film thickness gradually increases with the change of the oscillation frequency, it is not a fixed value but a measurement at each oscillation frequency (every n stages) measured in advance. Since the measured value of the crystal unit 5 is corrected by the correction ratio for each oscillation frequency obtained by comparison with the actual film thickness of the substrate for use, the error correction accuracy is extremely increased.

  Note that the present invention is not limited to this embodiment, and the specific configuration of each component can be designed as appropriate.

DESCRIPTION OF SYMBOLS 1 Substrate 3 Deposition apparatus 4 Deposition chamber 5 Crystal resonator

Claims (1)

A crystal resonator serving as a measurement unit of a crystal oscillation type film thickness monitor is provided in a film forming chamber of a film forming apparatus for forming a thin film by depositing a film forming material on the surface of the substrate, and the film forming material is deposited on the crystal resonator. a film thickness control method according to the crystal oscillator type film thickness monitor provided in the film forming apparatus for measuring the thickness of a thin film formed on the cause to the substrate surface, prior to film formation process using the pre-measurement for crystal oscillator Measure the film thickness of the thin film on the measurement substrate for each different oscillation frequency of this pre-measurement crystal unit and measure for each target film thickness and each oscillation frequency measured by the pre-measurement crystal unit The ratio of the measured substrate to the actual film thickness of the thin film is calculated as a correction ratio, and in the film formation process, the film thickness or film formation speed of the substrate thin film measured by the crystal resonator during film formation is calculated. Multiplying each correction ratio by the correction ratio according to the oscillation frequency A method of controlling the film thickness by correcting the thickness or deposition rate of the thin film of the substrate,
In the pre-measurement step performed before the film formation step, a pre-measurement crystal resonator is provided in the film formation chamber of the film formation apparatus for forming a thin film by depositing a film formation material on the surface of the measurement substrate. The film thickness of the thin film on the measurement substrate is measured by depositing a film forming material on the pre-measurement crystal resonator, and the actual thickness of the thin film on the measurement substrate is measured by the pre-measurement crystal resonator. The ratio to the target film thickness is calculated as the correction ratio, and the calculation of the correction ratio is an oscillation frequency that changes as the film thickness of the film forming material deposited on the pre-measurement crystal unit increases. For each change step, the thickness of the thin film deposited on the measurement substrate is sequentially changed to n times, and the correction ratio for each different oscillation frequency is calculated.
In the film forming step, another new crystal resonator is provided in the film forming chamber instead of the pre-measurement crystal resonator, and the correction ratio corresponding to the oscillation frequency of the crystal resonator is A film thickness control method using a crystal oscillation type film thickness monitor, wherein a film thickness or a film formation speed measured by a child is multiplied and corrected in accordance with a change in oscillation frequency .

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