JPH097960A - Method and apparatus for plasma cvd processing - Google Patents

Abstract

PURPOSE: To make it possible to perform a CVD process in a wide pressure range from low to high pressures by altering the state of the change of the peak value of high-frequency power at the first period of the high-frequency power applied to a plasma generating coil, and electronically controlling the temperature of the plasma. CONSTITUTION: A plasma generating coil 11 is wound on the periphery of a cylinder 2, and a high-frequency power source 20 for the coil is connected to the one end of the coil 11 via a matching unit 19. The high-frequency power for generating a plasma is periodically modulated. The frequency of the fundamental wave of the high-frequency power periodically modulated applied to the coil 11 is suitably selected according to the type of the substrate to be treated and the specification of the treatment. The method of the modulation is set as one of plasma CVD process conditions similar to the pressure and the flow rate of the reactive gas. Thus, the plasma CVD can be executed based on the pressure of a wide range.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is one of semiconductor manufacturing apparatuses, and a plasma CVD method in which a reactive gas is brought into a plasma state and a thin film is formed on a substrate to be processed such as a wafer or a glass substrate by using the plasma. And the device.

[0002]

2. Description of the Related Art Plasma CVD (Chemical V
Since the reaction mechanism of thin film formation in apor Deposition) is complicated, the mechanism is not clearly understood even now. The main reason for this is that the reactive gas used in plasma CVD is a polyatomic molecule, and it is necessary to consider both the gas phase reaction and the surface reaction of the substrate to be processed in the reaction system.

As a plasma CVD apparatus, a parallel plate type or ECR is generally used.

The parallel plate type is the most widely used type. High frequency power is applied between two plate electrodes installed in the reaction chamber to generate plasma, and the substrate to be processed on the substrate mounting table is processed. It produces a thin film on the surface.

The pressure in the reaction chamber of the CVD process in the parallel plate electrode device is usually 0.1 to 10 Torr, which is used in a relatively high region.

Further, pulse discharge may be used to improve the film quality by CVD or to suppress the generation of powder.

Since ECR can generate a high density plasma at a low pressure, it is used for a CVD process which requires a particularly low pressure. As for the structure of the device, when compared with the plate electrode type,
Since no electrode is required inside the reaction chamber, the inside of the reaction chamber has a simple structure, but it is complicated as a whole because a waveguide for introducing microwaves and a coil for magnetic field generation are required outside the reaction chamber. . Further, it is not suitable for uniform and large-area plasma generation.

[0008]

In the plasma CVD apparatus of parallel plate electrode type described above, the CVD process at low pressure is disadvantageous, and since the electrode is installed inside the reaction chamber, impurities on the thin film by the electrode are formed. Is concerned about the impact of.

Further, in the ECR apparatus, it is difficult to cope with an increase in the diameter of the substrate to be processed, and the process pressure of the CVD is only on the low pressure side, and the allowable pressure range is narrow. In addition, the structure of the device becomes large, and the klystron oscillator must be used in order to use the pulse discharge, and it is difficult to reduce the cost.

In view of such circumstances, the present invention enables a CVD process in a wide pressure range from low pressure to high pressure by using a coil as a plasma generation source, and is necessary for modulating high frequency power for plasma generation. Plasma C that is equipped with means and can reduce the cost and widen the process margin
A VD method and an apparatus thereof are provided.

[0011]

According to the present invention, high frequency power is applied to a plasma generating coil to generate plasma,
In the method of performing CVD using plasma, the electron temperature control of plasma is performed by changing the mode of change of the peak value of the high frequency power in one cycle of the high frequency power applied to the plasma generating coil. Plasma CVD method, vacuum chamber, target substrate mounting table provided in vacuum chamber for controlling temperature of target substrate, plasma generating coil, and high frequency power source for coil connected to the plasma generating coil In a plasma CVD apparatus capable of evacuating the vacuum chamber and introducing a reactive gas into the vacuum chamber, an oscillating unit for periodically modulating high frequency power by the high frequency power supply for coils is provided. The present invention also relates to a plasma CVD apparatus provided with a means capable of arbitrarily changing the position of the plasma generating coil in the height direction.

[0012]

Since the high frequency power is periodically modulated, the discharge current changes with time and the electron temperature changes with time, so that the ratio of the excited species of plasma changes and the etching characteristics change.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings.

In FIGS. 1 and 2, quartz is concentrically formed on the vacuum container 1 which is made of a conductive material and has an airtight structure.
A cylinder 2 made of an insulating material such as ceramics is connected in an airtight manner, and an upper end of the cylinder 2 is airtightly closed by a lid 3 made of a conductive material or an insulating material and surrounded by the vacuum container 1, the cylinder 2 and the lid 3. The space forms an airtight vacuum chamber 14.

A gas introducing pipe 4 for introducing a reaction gas into the vacuum chamber 14 is connected to the lid 3, an exhaust pipe 5 is connected to the bottom surface of the vacuum container 1, and a vacuum pump 6 is connected to the exhaust pipe 5.
, And a plate electrode 8 whose temperature can be adjusted via an insulating material 7 is provided on the inner bottom of the vacuum container 1. A substrate 16 to be processed such as a wafer or a glass substrate is placed on the plate electrode 8, and the substrate 16 to be processed can be heated to a required temperature. The electrode high frequency power source 10 is connected via the.

A plasma generating coil 11 is wound around the cylinder 2, and a coil high frequency power source 20 is connected to one end of the plasma generating coil 11 via a matching unit 19. The plasma generating coil 11 is provided so as to be able to move up and down with respect to the cylinder 2, and its position can be changed by an elevating means (not shown). The coil high-frequency power source 20 has an oscillating unit capable of outputting modulated high-frequency power as described later.

FIG. 3 shows an example of the oscillating section of the coil high-frequency power source 20 which outputs the high-frequency power applied to the plasma generating coil 11, and the oscillating section of the coil high-frequency power source 20 mainly generates a fundamental wave. And a signal synthesizer 22 connected to the fundamental wave generator 21, an amplifier 23 connected to the signal synthesizer 22, and a modulated wave generator 24 connected to the signal synthesizer 22.

The high frequency power of the steady sine curve waveform (see FIG. 4) output from the fundamental wave generator 21 is input to the signal synthesizer 22 and the modulation signal is also input from the modulation wave generator 24. The signal synthesizer 22 outputs the fundamental wave in a form modulated in each cycle Ts. Further, the high frequency output from the signal synthesizer 22 is amplified by the amplifier 23 to a predetermined power value (peak value) and output.

As an example of the modulation waveform from the signal synthesizer 22, FIGS. 5 (a) (b) (c) (d) are shown. The output waveform from the amplifier 23 is shown in FIGS. 5 (a) (b) (c).
A waveform obtained by amplifying (d) is obtained. Note that in FIG. 5, the envelope of the output waveform is trapezoidal (FIG. 5A) and triangular (FIG. 5A).
(B)), rectangular wave (Fig. 5 (c)), intermittent wave (Fig. 5)
Although (d) is shown, it is needless to say that it can be variously changed by manipulating the signal from the modulated wave generator 24, such as repeating a sine curve or step change.

The operation will be described below.

The substrate 16 to be processed is placed on the flat plate electrode 8, the vacuum chamber 14 is evacuated by the vacuum pump 6, and a predetermined pressure is maintained by a pressure control device (not shown) while the vacuum chamber 14 is kept in the vacuum chamber 14. A reactive gas is introduced from the gas introduction pipe 4.

High frequency power output from the coil high frequency power supply 20 is applied to the plasma generating coil 11 by the matching unit 19 described above.
When applied through the plasma generating coil 11, the reactive gas is ionized by the action of the high frequency alternating electric field and the magnetic field to generate the plasma 15 in the vacuum chamber 14, and further, the plasma on the plate electrode 8 is applied. A thin film is formed on the surface of the processing substrate 16.

As described above, since the high frequency power for plasma generation is periodically modulated, the discharge current changes with time. The electron temperature rises during the period when the discharge current increases,
The electron temperature decreases during the period when the discharge current decreases. This is because the time constant of changes in the electron temperature of plasma is smaller than the time constant of changes in plasma density.

Plasma parameters other than the electron temperature change during the changing period of the electron temperature, but at this time, the ratio of the excited species also changes. As a result, the chemical reaction in the vapor phase and the chemical reaction on the surface of the wafer are changed, so that the CVD characteristics are also changed.

As the output waveform of the high frequency power of the amplifier 23, the output waveform of the modulation signal generator 24 is shown in FIGS.
It can be freely changed by changing it as shown in the example of (d), and is appropriately changed and optimized so as to obtain a required CVD characteristic.

The frequency of the fundamental wave of the periodically modulated high frequency power applied to the plasma generating coil 11 is appropriately selected depending on the type of the substrate 16 to be processed and the processing specifications, and is usually in the range of 1 MHz to 100 MHz. An appropriate value is selected. In addition, the modulation method is appropriately changed and optimized in order to control the electron temperature of plasma to make the ratio of active species appropriate in accordance with the object to be processed and the processing specifications of the required process.

Thus, the modulation method is set as one of the plasma CVD process conditions in the same manner as the pressure and the flow rate of the reactive gas. The period of the modulation signal is arbitrarily set within the range of 10 μs to 10 ms.

FIG. 6 shows another example of the high frequency power supply. The periodically modulated signal output from the arbitrary signal generator 25 is input to the high frequency power amplifier 26. The high frequency power amplifier 26 amplifies the input modulation signal with a predetermined amplification factor and outputs it. Since the arbitrary signal generator 25 can arbitrarily set the required waveform, not only the peak value of the high frequency but also the frequency and the waveform can be arbitrarily changed within one cycle.
The range of modulation methods is expanded.

Thus, the high frequency power modulated periodically by the coil high frequency power source 20 can be applied to the plasma generating coil 11.

Even when a modulated wave is directly generated by the arbitrary signal generator 25, the modulated wave is optimized according to the required processing specifications of the process. Moreover, mechanical adjustment such as changing the center of plasma by changing the vertical position of the plasma generating coil 11 is also possible.

It should be noted that the number of turns of the plasma generating coil 11 can be selected to be any number of turns of 1 or more.
Considering the uniformity of the generated plasma, the plasma density, etc., one roll is sufficient. Further, the example in which the plasma generating coil 11 is provided in a state of being wound around the cylinder 2 is shown. However, the high frequency power applying method of the present invention is applicable to the case where the coil is provided in parallel with the lid 3 or the reaction chamber. It can be applied to any coil and its installation method, such as when it is provided on the side surface of No. 1 or inside the reaction chamber 1.

A specific example of the operation of this embodiment will be described below.

FIG. 7 shows the relationship between the high frequency power applied to the plasma generating coil 11, the plasma (electron) density (solid line in the figure) and the average value of the electron temperature (broken line in the figure) measured by the double probe method. It is a figure.

The measurement conditions are as follows. Frequency of high-frequency power: 13.56 MHz Pressure: 1.0 Pa Gas: C ₂ F _{6 When} high-frequency power is 1.0 KW, plasma (electron) density is low even at pressure of 1.0 Pa. None, 4 × 10 ¹¹
A value as high as ECR, which is the number of pieces / cm ³ , is obtained.

FIG. 8 shows the pulse width of the pulsed high frequency power applied to the plasma generating coil 11 (ON time of the high frequency power), the plasma (electron) density (solid line in the figure) measured by the double probe method, and the average of the electron temperature. It is the figure which showed the relationship of a value (broken line in a figure). The OFF time of the pulse is fixed at 10 μs.

The measurement conditions are as follows. High-frequency power: 1.0 KW High-frequency power frequency: 13.56 MHz (continuous) Pressure: 1.0 Pa gas: C ₂ F _{6 When the} pulse width (high-frequency power ON time) is shortened, The average value of is low. From this result, it is understood that the average value of the electron temperature of plasma can be controlled by changing the pulse width.

[0037]

As described above, according to the present invention, since high frequency power is applied to the plasma generating coil to generate plasma, cost reduction can be realized, and high frequency power can be easily modulated. By modulating the power,
Plasma CVD can be performed under a wide range of pressure,
Moreover, by controlling the average value of the electron temperature of the plasma,
It exhibits an excellent effect such that the process margin of plasma CVD can be widened.

[Brief description of drawings]

FIG. 1 is a perspective view showing an embodiment of the present invention.

FIG. 2 is a sectional view of the embodiment.

FIG. 3 is a block diagram showing an example of an oscillating unit in the embodiment.

FIG. 4 is a diagram showing a fundamental wave in the high frequency power supply.

5 (a), (b), (c) and (d) are diagrams showing examples of applied power waveforms in the high frequency power supply.

FIG. 6 is a diagram showing an example of a high frequency power supply in the present embodiment.

FIG. 7: High frequency power applied to coil and plasma density,
It is a diagram which shows the relationship of electron temperature.

FIG. 8 is a diagram showing the relationship between the pulse width of the pulsed high-frequency power applied to the coil, the plasma density, and the electron temperature.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Vacuum container 2 Cylinder 3 Lid 4 Gas introduction pipe 5 Exhaust pipe 6 Vacuum pump 11 Plasma generation coil 19 Matching device 20 High frequency power supply for coil

Claims (3)

[Claims] 1. A high frequency power is applied to a plasma generating coil to generate plasma, and the plasma is used to perform CVD.
In the method for performing plasma, the electron temperature control of plasma is performed by changing the manner of changing the peak value of the high frequency power in one cycle of the high frequency power applied to the plasma generating coil. CVD method. 2. A vacuum chamber, a target substrate mounting table provided in the vacuum chamber, capable of controlling the temperature of a target substrate, a plasma generating coil, and a coil high-frequency power source connected to the plasma generating coil. In a plasma CVD apparatus capable of evacuating the vacuum chamber and introducing a reactive gas into the vacuum chamber, an oscillating unit for periodically modulating high frequency power by the high frequency power supply for coils is provided. A plasma CVD apparatus characterized by the above. 3. The plasma CVD apparatus according to claim 2, further comprising means capable of arbitrarily changing the position of the plasma generating coil in the height direction.