KR102217755B1 - Depostion method and device for thin film layer - Google Patents

Abstract

The thin film deposition apparatus includes a deposition source, a crystal sensor, a correction unit, and a deposition rate control unit. The evaporation source evaporates and diffuses the thin film constituent material toward the substrate. The crystal sensor is located in the diffusion path of the thin film material. The correction unit stores a deposition thickness variation equation composed of a polynomial of a second or higher order, and calculates a deposition thickness reduction rate and a deposition thickness correction value from the resonance frequency of the crystal sensor measured at the start of a specific cycle. The deposition rate control unit controls the evaporation source according to the deposition thickness correction value input from the correction unit to control the evaporation amount of the thin film constituent material.

Description

Thin film deposition method and apparatus {DEPOSTION METHOD AND DEVICE FOR THIN FILM LAYER}

The present invention relates to a thin film deposition method and apparatus, and more particularly, to a thin film deposition method and apparatus for controlling the deposition thickness using a crystal sensor.

The thin film deposition process is a core process used to manufacture various devices such as displays, semiconductors, and solar cells. For example, an organic light-emitting device constituting an organic light-emitting display (OLED) is composed of a stack of an anode electrode, a hole injection layer, a hole transport layer, a light-emitting layer, an electron transport layer, an electron injection layer, and a cathode electrode, and an anode electrode and a cathode electrode. The remaining layers except for are organic films and are mainly formed by vacuum thermal evaporation.

In the vacuum thermal evaporation process for forming a thin film, for example, an organic film, a substrate and an evaporation source are placed in a chamber to face each other, the chamber is evacuated by vacuum, and organic matter is evaporated and diffused from the evaporation source to deposit on the substrate. It consists of a process. The evaporation source may include a crucible containing an organic material and a heater that heats the crucible.

In addition, a crystal sensor made of a piezoelectric crystal such as quartz is positioned in the diffusion path of the organic material. The piezoelectric crystal resonates at a natural frequency when a voltage of a certain frequency is applied, and the resonant frequency decreases in proportion to an increase in mass as organic matter accumulates on the surface. From this change in the resonance frequency, the deposition thickness of the thin film can be calculated.

Once mounted in a vacuum chamber, the crystal sensor is repeatedly used dozens of times. As the service life increases, a difference occurs between the thickness of the thin film calculated from the crystal sensor and the thickness of the thin film deposited on the actual substrate. That is, as the service life increases, the precision decreases, making it difficult to implement the desired thin film thickness.

In the present invention, in a thin film deposition method and apparatus using a crystal sensor, precision can be maintained even when the service life is increased by applying a correction technique when calculating the deposition thickness of a thin film from the resonance frequency of the crystal sensor. To provide a thin film deposition method and apparatus capable of accurately depositing a thin film of.

A method of depositing a thin film according to an embodiment of the present invention includes a first deposition step, a variation expression derivation step, and a second deposition step. The first deposition step includes a process of evaporating a thin film constituent material from a deposition source to deposit a thin film on a substrate, replacing the substrate, and continuously performing a deposition process in a plurality of cycles. In the step of deriving the change equation, the resonance frequency of the crystal sensor at the start of each of the plurality of cycles and the measured thickness of the thin film deposited on the substrate in each of the plurality of cycles are obtained, and from the correlation between the resonance frequency and the measured thickness, a polynomial of 2 or more orders is obtained. It includes the process of deriving the formed deposition thickness change equation. In the second deposition step, the deposition process is continuously performed in a plurality of cycles, but the deposition thickness reduction rate and deposition thickness correction value are calculated from the resonance frequency of the crystal sensor measured at the start of a specific cycle using the deposition thickness change equation, and the deposition thickness is corrected. It includes the process of controlling the evaporation amount of the thin film constituent material according to the value.

In the step of deriving the variation equation, the measured resonance frequency and thickness can constitute (x, y) data, and the deposition thickness variation equation is derived from a plurality of (x, y) data corresponding to a plurality of cycles by polynomial regression analysis. can do.

In the second deposition step, when the resonance frequency of a specific cycle is the current frequency (x), the deposition thickness (y) corresponding to the current frequency (x) can be obtained from the deposition thickness change equation, and deposition using the following equation The thickness reduction rate (A) can be calculated.

A = (y ₀ -y)/y ₀ = Δy/y ₀

Here, y ₀ represents the measured thickness of the thin film deposited on the substrate in the first cycle among the plurality of cycles.

On the other hand, in the step of deriving the change equation, the resonance frequency and the measured thickness can constitute (x, y) data, and the deposition thickness by polynomial regression analysis from a plurality of (x, y) data corresponding to a plurality of cycles. A change equation can be derived, but by normalizing the maximum y value to 1, the deposition thickness variation equation can be derived.

In the second deposition step, when the resonance frequency of a specific cycle is the current frequency (x), the deposition thickness reduction rate (y) corresponding to the current frequency (x) may be calculated from the deposition thickness change equation.

The deposition thickness correction value may be a correction value that increases the evaporation amount of the thin film constituent material by the deposition thickness reduction rate calculated in a specific cycle. The deposition source may be controlled by the deposition rate controller, and the deposition rate controller may increase the evaporation amount of the thin film constituent material according to the deposition thickness correction value.

A thin film deposition apparatus according to an embodiment of the present invention includes a deposition source, a crystal sensor, a correction unit, and a deposition rate control unit. The evaporation source evaporates and diffuses the thin film constituent material toward the substrate. The crystal sensor is located in the diffusion path of the thin film material. The correction unit stores a deposition thickness variation equation composed of a polynomial of a second or higher order, and calculates a deposition thickness reduction rate and a deposition thickness correction value from the resonance frequency of the crystal sensor measured at the start of a specific cycle. The deposition rate control unit controls the deposition source according to the deposition thickness correction value input from the correction unit to control the evaporation amount of the thin film constituent material.

While continuously performing the deposition process in a plurality of cycles, the resonance frequency of the crystal sensor at the start of each of the plurality of cycles and the measured thickness of the thin film deposited on the substrate in each of the plurality of cycles can be obtained, and the measured resonance frequency and thickness are (x , y) When configuring the data, the deposition thickness variation equation may be derived from a plurality of (x, y) data corresponding to a plurality of cycles by a polynomial regression method.

When the resonance frequency of the crystal sensor measured at the start of a specific cycle is the current frequency (x), the deposition thickness (y) corresponding to the current frequency (x) can be obtained from the deposition thickness change equation, and the following formula The deposition thickness reduction rate (A) can be calculated using.

A = (y ₀ -y)/y ₀ = Δy/y ₀

Here, y ₀ represents the measured thickness of the thin film deposited on the substrate in the first cycle among the plurality of cycles.

On the other hand, while continuously performing the deposition process in a plurality of cycles, the resonance frequency of the crystal sensor at the start of each of the plurality of cycles and the measured thickness of the thin film deposited on the substrate in each of the plurality of cycles can be obtained, and the resonance frequency and thickness When the measured values constitute (x, y) data, the deposition thickness change equation is derived from a plurality of (x, y) data corresponding to a plurality of cycles through the process of normalizing the maximum y value to 1 by polynomial regression analysis. I can.

When the resonance frequency of the crystal sensor measured at the start of a specific cycle is the current frequency (x), the correction unit may calculate the deposition thickness reduction rate (y) corresponding to the current frequency (x) from the deposition thickness change equation.

The correction unit may calculate a deposition thickness correction value that increases the evaporation amount of the thin film constituent material by the deposition thickness reduction rate calculated in a specific cycle. The deposition rate control unit may increase the evaporation amount of the thin film constituent material by controlling the deposition source according to the deposition thickness correction value input from the correction unit.

According to the present invention, even if the service life of the crystal sensor is increased, precision can be maintained using a correction technique, and a thin film having a desired thickness can be accurately deposited regardless of the number of cycles.

1 is a flow chart showing a thin film deposition method according to an embodiment of the present invention.
2 is a block diagram showing a thin film deposition apparatus according to an embodiment of the present invention.
FIG. 3 is a graph for explaining a process of deriving a deposition thickness change equation in a second step shown in FIG. 1.
FIG. 4 is a graph illustrating a process of calculating a correction value for a deposition thickness in a third step shown in FIG. 1.
5 is a graph showing the actual deposition thickness of a thin film deposited by applying the correction of the third step.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings so that those of ordinary skill in the art may easily implement the present invention. The present invention may be implemented in various different forms and is not limited to the embodiments described herein.

1 is a flow chart showing a thin film deposition method according to an embodiment of the present invention.

Referring to FIG. 1, the thin film deposition method includes a first step (S10) of continuously performing a deposition process in a plurality of cycles, and a deposition consisting of a polynomial of a second or higher order from the correlation of the actual deposition thickness of the thin film to the vibration frequency of the crystal sensor. A second step (S20) of deriving a thickness change equation, and a third step (S30) of controlling an evaporation amount by calculating a deposition thickness correction value from the deposition thickness change equation.

2 is a block diagram showing a thin film deposition apparatus according to an embodiment of the present invention.

Referring to FIG. 2, the thin film deposition apparatus 100 includes a chamber 20 accommodating a substrate 10 in an internal space, a deposition source 30 installed inside the chamber 20, and a crystal sensor 40. . The chamber 20 is evacuated by a vacuum pump (not shown) to maintain a vacuum.

The substrate 10 may be a substrate of an organic light emitting display, and may be formed of a rigid glass substrate or a flexible plastic film. The substrate 10 is fixed to a support 21 such as an electrostatic chuck or a vacuum chuck, and is disposed so that the evaporation surface faces downward. A pattern mask 22 defining a deposition area may be positioned under the deposition surface of the substrate 10.

The evaporation source 30 includes a crucible 31 containing a thin film constituent material, for example, an organic material, and a heater 32 that heats the crucible 31. When the temperature of the crucible 31 by the heater 32 reaches the evaporation temperature of the organic material, the organic material is evaporated and diffused from the crucible 31 and deposited on the substrate 10.

The crystal sensor 40 may include a piezoelectric crystal 41 made of crystal or the like, and an oscillator 42 that converts the vibration frequency of the piezoelectric crystal 41 into an electric signal and outputs an electric signal. The piezoelectric crystal 41 is located in the diffusion path of the organic material, and the organic material is deposited on the piezoelectric crystal 41 during thin film deposition.

The piezoelectric crystal 41 resonates at a natural frequency by receiving a voltage of a certain frequency by an electrode (not shown), and the resonance frequency decreases in proportion to the thickness of the organic material accumulated on the surface. The crystal sensor 40 is a type of mass sensor and calculates the deposition thickness of the thin film from the change of the resonance frequency.

Once the chamber 20 is evacuated to a vacuum, thin film deposition is continuously performed in a plurality of cycles while replacing the substrate 10 and the deposition source 30. One cycle refers to the deposition process for one thin film. Since the crystal sensor 40 is continuously used during a plurality of cycles, an organic material deposited in the previous cycle is continuously accumulated on the piezoelectric crystal 41. Therefore, as the number of cycles increases, the precision of the determination sensor 40 decreases.

FIG. 3 is a graph for explaining a process of deriving a deposition thickness change equation in a second step shown in FIG. 1. Referring to FIG. 3, the horizontal axis (x) of the graph is the resonance frequency of the crystal sensor, and the vertical axis (y) is the actual thickness of the thin film deposited on the substrate.

2 and 3, in the second step (S20), the measured thickness of the thin film deposited on the actual substrate 10 is calculated for the resonance frequency of the crystal sensor 40 measured at the start of each cycle, and the resonance It consists of a process of deriving a deposition thickness change equation composed of a polynomial of a second or higher order from the correlation between the frequency and the measured thickness.

Specifically, the resonant frequency of the crystal sensor 40 was measured at the start of each cycle, and the thickness of the thin film deposited on the actual substrate 10 was measured for each cycle, and the result is shown as a plurality of points in the graph. .

That is, the x-coordinate of each of the plurality of points displayed in the graph is the resonance frequency of the crystal sensor 40 measured at the start of each cycle, and the y-coordinate is the actual thickness measurement value of the thin film deposited on the substrate 10 in each cycle. Show.

Since the organic matter deposited in the previous cycle is continuously accumulated on the surface of the piezoelectric crystal 41, the resonance frequency of the crystal sensor 40 measured at the start of each of the plurality of cycles decreases as the number of cycles increases. In addition, as the number of cycles increases, the thickness of the thin film deposited on the actual substrate 10 decreases due to a decrease in precision of the crystal sensor 40.

From the above-described measured data, a deposition thickness variation equation consisting of a polynomial function of a second order or higher is derived using a known polynomial regression method. The polynomial regression method is a known numerical analysis method that obtains a polynomial that best represents n data consisting of (x1, y1), (x2, y2), (x3, y3) ... (xn, yn).

For example, the deposition thickness change equation derived in the second step S20 may be expressed as a quadratic function of Equation 1 below. The quadratic function shown in Equation 1 is only an example, and the deposition thickness variation equation can be derived in various forms according to given measured data.

[Equation 1]

y = -9×10 ^-9 x ² + 1.1033×10 ^-1 x-329496

The graph of FIG. 3 is an actual measurement value when the target thickness of the thin film is set to 1,000 Å, and even if the target thickness of the thin film is changed to another value, a substantially the same deposition thickness change equation is derived.

For example, when the target thickness of the thin film is set to 500 Å, since the time taken for one cycle is reduced by half compared to the case of 1,000 Å, it is possible to obtain two times more measured values than the result shown in FIG. 3. On the other hand, when the target thickness of the thin film is set to 2,000 Å, the time taken for one cycle is doubled compared to 1,000 Å, and thus an actual measured value that is twice less than the result shown in FIG. 3 can be obtained.

As described above, since there is a difference in the number of data depending on the target thickness of the thin film, but the trend of the data is the same, it is possible to derive a substantially identical deposition thickness change equation regardless of the target thickness.

FIG. 4 is a graph illustrating a process of calculating a correction value for a deposition thickness in a third step shown in FIG. 1. The graph of FIG. 4 is the same as the deposition thickness change equation derived in the second step.

2 and 4, the third step (S30) calculates a deposition thickness change amount and a deposition thickness correction value from the resonance frequency of the crystal sensor 40 measured at the start of a specific cycle using the deposition thickness change equation. And, it consists of depositing a thin film by reflecting the deposition thickness correction value to the process of the cycle.

The first step (S10) and the second step (S20) may be a preliminary process for obtaining a deposition thickness change equation, and the third step (S30) may be a main process of depositing a thin film by reflecting a deposition thickness correction value. . That is, the third step (S30) is a process of continuously performing thin film deposition in the same process as the first step (S10), but depositing a thin film using a deposition thickness correction value obtained from the deposition thickness change equation.

In the third step (S30), while continuously performing thin film deposition in a plurality of cycles, the resonance frequency of the crystal sensor 40 is measured at the start of a specific cycle, and this value is denoted by x. Then, the difference with respect to the resonance frequency (x ₀ ) of the determination sensor 40 measured at the start of the first cycle can be known. This difference is indicated by Δx in FIG. 4.

Substituting x into the deposition thickness change equation derived in the second step (S20), the deposition thickness (y) corresponding to the current frequency (x) can be found, and the deposition thickness of the first cycle closest to the target thickness (y ₀ ) You can see the difference. This difference is indicated by Δy in FIG. 4. The deposition thickness reduction rate is a value obtained by dividing Δy by y ₀ , and a deposition thickness correction value is calculated from the deposition thickness reduction rate (Δy/y ₀ ).

For example, if the deposition thickness reduction rate (Δy) is 5% at the current frequency (x), it means that the thickness of the thin film approaches the target thickness when 5% is additionally deposited in the current process. The deposition thickness correction value means a correction value instructing to additionally deposit an organic material as much as the deposition thickness reduction rate (Δy/y ₀ ).

In FIG. 2, the deposition source 30 is electrically connected to the deposition rate control unit 50, and the deposition rate control unit 50 controls the operation of the deposition source 30 to increase the amount of organic matter evaporated from the deposition source 30. Adjust.

In the third step (S30), the deposition rate control unit 50 controls the deposition source 30 using the calculated deposition thickness correction value, thereby increasing the evaporation amount of the organic material according to the deposition thickness correction value. By this evaporation amount correction, the actual thickness of the thin film deposited on the substrate 10 in the current cycle may be close to the target thickness.

The deposition rate control unit 50 and the crystal sensor 40 may be electrically connected to the correction unit 60. The correction unit 60 functions to store the deposition thickness change equation derived in the second step (S20) and calculate a deposition thickness reduction rate (Δy/y ₀ ) and a deposition thickness correction value at the current frequency (x).

The target thickness of the thin film in the third step S30 may be the same as or different from the target thickness of the second step S20. Even if the target thickness of the third step (S30) is different from the target thickness of the second step (S20), the deposition thickness reduction rate (Δy/y ₀ ) is the same at the current frequency (x), so the calculated deposition thickness correction value You can increase the evaporation amount of organic matter in proportion.

The calculation of the deposition thickness reduction rate and the deposition thickness correction value in the third step (S30) and the control of the deposition source accordingly may be performed in all of a plurality of cycles or may be selectively performed in a predetermined number of cycles. In the former case, it is possible to achieve a deposition thickness very close to the target thickness in all of a plurality of cycles.

Meanwhile, when the deposition thickness change equation is derived from the measured data obtained in the second step S20, the maximum y value (y ₀ ) is normalized to 1 to derive the deposition thickness change equation. Then, a polynomial of a second or higher order having different coefficients from Equation 1 described above is derived, and in this function, a y value corresponding to a specific x value is directly coincident with the deposition thickness reduction rate.

In other words, in the deposition thickness change equation derived without the normalization process, the deposition thickness reduction rate is calculated by dividing Δy by y ₀ each time, but the deposition thickness change equation derived by normalizing the maximum y value (y ₀ ) to 1 corresponds to a specific x value. Since the y value is a ratio (deposition thickness reduction rate) to the maximum y value (y ₀ ), the calculation process can be simplified.

5 is a graph showing the actual deposition thickness of a thin film deposited by applying the correction of the third step. Referring to FIG. 5, as a result of performing additional deposition using the above-described deposition thickness correction value in a plurality of cycles, it can be seen that the deposition thickness of the thin film is uniformed close to the target thickness regardless of the number of cycles.

In the above, preferred embodiments of the present invention have been described, but the present invention is not limited thereto, and it is possible to implement various modifications within the scope of the claims, the detailed description of the invention, and the accompanying drawings. It is natural to fall within the scope of

100: thin film deposition apparatus 10: substrate
20: chamber 21: support
22: pattern mask 30: evaporation source
31: crucible 32: heater
40: crystal sensor 41: piezoelectric crystal
42: oscillator 50: deposition rate control unit
60: correction unit

Claims (14)

A first deposition step of evaporating a thin film constituent material from a deposition source to deposit a thin film on a substrate to a first target thickness, replacing the substrate and continuously performing a deposition process in a plurality of cycles;
The resonant frequency of the crystal sensor at the start of each of the plurality of cycles and the measured thickness of the thin film deposited on the substrate in each of the plurality of cycles are obtained, and the correlation between the first target thickness, the resonance frequency and the measured thickness A variation formula deriving step of deriving a deposition thickness variation equation consisting of a polynomial of a second or higher order from And
The deposition process is continuously performed in a plurality of cycles, but the deposition thickness reduction rate and the deposition thickness correction value are calculated from the resonance frequency of the crystal sensor measured at the start of a specific cycle deposited to a second target thickness using the deposition thickness change equation. And a second deposition step of controlling the evaporation amount of the thin film constituent material such that the deposition thickness is the same as the second target thickness according to the deposition thickness correction value,
The first target thickness and the second target thickness are different, but the first target thickness is smaller than the second target thickness. The method of claim 1,
In the step of deriving the change equation, the resonance frequency and the measured thickness value constitute (x, y) data, and the deposition thickness change by polynomial regression analysis from a plurality of (x, y) data corresponding to the plurality of cycles Thin film deposition method to derive the equation. The method of claim 2,
In the second deposition step, when the resonance frequency of the specific cycle is the current frequency (x), the deposition thickness (y) corresponding to the current frequency (x) is obtained from the deposition thickness change equation, and the following equation is used: A thin film deposition method for calculating the deposition thickness reduction rate (A).
A = (y ₀ -y)/y ₀ = Δy/y ₀
Here, y ₀ represents the measured thickness of the thin film deposited on the substrate in the first cycle among the plurality of cycles. The method of claim 1,
In the step of deriving the change equation, the resonance frequency and the measured thickness value constitute (x, y) data, and the deposition thickness change by polynomial regression analysis from a plurality of (x, y) data corresponding to the plurality of cycles A thin film deposition method that derives an equation, but normalizes the maximum y value to 1 to derive the deposition thickness change equation. The method of claim 4,
In the second deposition step, when the resonance frequency of the specific cycle is the current frequency (x), the deposition thickness reduction rate (A) corresponding to the current frequency (x) is calculated from the deposition thickness change equation . The method according to any one of claims 2 to 5,
The deposition thickness correction value is a correction value for increasing the evaporation amount of the thin film constituent material by the deposition thickness reduction rate calculated in the specific cycle. The method of claim 6,
The deposition source is controlled by a deposition rate control unit,
The deposition rate control unit increases the evaporation amount of the thin film constituent material according to the deposition thickness correction value. An evaporation source for evaporating and diffusing the thin film component material toward the substrate;
A crystal sensor positioned in the diffusion path of the thin film material;
The deposition thickness decrease rate from the resonance frequency of the crystal sensor measured at the start of a specific cycle deposited on the basis of the second target thickness, and stores a deposition thickness change equation consisting of a polynomial of a second or higher order obtained based on the first target thickness A correction unit that calculates a correction value for the deposition thickness and; And
And a deposition rate controller configured to control the deposition source according to the deposition thickness correction value input from the correction unit to control an evaporation amount of the thin film constituent material such that the deposition thickness is the same as the second target thickness,
The first target thickness and the second target thickness are different, but the first target thickness is smaller than the second target thickness. The method of claim 8,
While continuously performing the deposition process in a plurality of cycles, the resonance frequency of the crystal sensor at the start of each of the plurality of cycles and the measured thickness of the thin film deposited on the substrate in each of the plurality of cycles are obtained, and the resonance frequency and the thickness When the measured values constitute (x, y) data,
The deposition thickness variation equation is derived from a plurality of (x, y) data corresponding to the plurality of cycles by a polynomial regression analysis method. The method of claim 9,
When the resonant frequency of the crystal sensor measured at the start of the specific cycle is the current frequency (x), the correction unit obtains a deposition thickness (y) corresponding to the current frequency (x) from the deposition thickness change equation , Thin film deposition apparatus for calculating the deposition thickness reduction rate (A) using the following equation.
A = (y ₀ -y)/y ₀ = Δy/y ₀
Here, y ₀ represents the measured thickness of the thin film deposited on the substrate in the first cycle among the plurality of cycles. The method of claim 8,
While continuously performing the deposition process in a plurality of cycles, the resonance frequency of the crystal sensor at the start of each of the plurality of cycles and the measured thickness of the thin film deposited on the substrate in each of the plurality of cycles are obtained, and the resonance frequency and the thickness When the measured values constitute (x, y) data,
The deposition thickness change equation is derived from a plurality of (x, y) data corresponding to the plurality of cycles through a process of normalizing a maximum y value to 1 by polynomial regression analysis. The method of claim 11,
When the resonant frequency of the crystal sensor measured at the start of the specific cycle is the current frequency (x), the deposition thickness reduction rate (A) corresponding to the current frequency (x) from the deposition thickness change equation Thin film deposition apparatus to calculate. The method according to any one of claims 9 to 12,
The correction unit calculates the deposition thickness correction value for increasing the evaporation amount of the thin film constituent material by the deposition thickness reduction rate calculated in the specific cycle. The method of claim 13,
The deposition rate controller controls the deposition source according to the deposition thickness correction value input from the correction unit to increase the evaporation amount of the thin film constituent material.

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