JPH0794130A - Control method and control device for radical - Google Patents

Abstract

PURPOSE:To control density and composition of a generated radical by pulse- modulating electric power of a high frequency wave, a direct current, a micro wave, or an electron beam at a fixed period, and changing a duty ratio thereof to decompose a reactive gas. CONSTITUTION:CHF3 is introduced into a discharge chamber 2 and maintained at pressure of 0.4 Pa. A microwave is set at input power 300W, a flow rate 5.0sccm, a period 100 msec and an output duty ratio of a microwave power source is changed by 15-100% (continuous) to conduct on/off modulation of plasma. In this case, an Si substrate is used for a substrate 10 to be treated, high frequency is not impressed, and a sum of on/off period is set constant at 100 ms. Measurement of radical density in an upper part of the substrate 10 by means of an infrared semiconductor laser absorption spectroscope shows that the radical density and composition in the ECR plasma can be controlled by changing the duty ratio.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and a control device for controlling the density and composition of radicals with high precision, and a method and a device used in the production of thin film electronic devices and the creation and development process of new materials. To provide. Fields in which the present invention can be used are CVD using plasma, dry etching equipment and radical beams, radical CVD / etching equipment, and the like.

[0002]

2. Description of the Related Art A thin film forming process and a material processing process using plasma are indispensable techniques for manufacturing a thin film electronic device such as an LSI and creating a new material. Radicals play an important role in these processes.

[0003]

However, in the thin film formation using plasma and the material processing process,
Although radicals play an extremely important role, it has been impossible to control the density and composition of radicals with high precision. Therefore, it has been difficult to realize the formation and processing of a desired material thin film.

[0004]

SUMMARY OF THE INVENTION The present invention provides a method and apparatus for controlling the density and composition of radicals in plasma in the thin film formation and material processing plasma described above with high accuracy.

The features of the present invention are as follows. First invention In a plasma formed by applying high frequency, direct current or microwave or electron beam, the high frequency, direct current or microwave or electron beam power is pulse-modulated at a constant cycle, and the duty ratio of the pulse modulation A method for controlling radicals, characterized in that the reactive gas is decomposed by changing the temperature, and the density and composition of radicals generated from the decomposition of the reactive gas are controlled.

Second Invention A plasma discharge chamber connected to a microwave generating power source having a pulse generator by a waveguide, a vacuum container connected to the plasma discharge chamber, and a vacuum exhaust device connected to the other of the vacuum containers. A substrate to be processed provided to face the plasma emitted from the plasma discharge chamber, a first electrode for supporting the substrate to be processed, and a pulse generator for the first electrode for supporting the substrate. A high frequency or direct current or microwave or electron beam power source connected via a matching circuit, a water cooling pipe system for water cooling the first electrode, a magnetic coil provided around the plasma discharge chamber, and a water cooling mechanism. And a first reactive gas inlet provided in the discharge chamber, and a microwave is applied to the reactive gas supplied to the plasma discharge chamber to generate plasma. Formed, pulse-modulate the high frequency, direct current, microwave or electron beam power at a constant cycle, decompose the reactive gas by changing the duty ratio of the pulse modulation,
An apparatus for controlling radicals, which is configured to control the density and composition of radicals generated from decomposition of reactive gas.

In carrying out the present invention, the reactive gas is a fluorocarbon gas, a hydrogenated silicon gas containing at least silicon atoms and hydrogen atoms, a hydrogenated carbon gas containing at least carbon atoms and hydrogen atoms, or a halogen gas. Is used.

[Structure] FIG. 1 shows an example of the structure of an ECR plasma processing apparatus to which the present invention is applied. In the figure, reference numeral 1 is a vacuum container forming a reaction chamber, and a discharge chamber 2 for generating ECR discharge is connected to the upper part of the vacuum container 1.
The discharge chamber 2 is provided with a waveguide 3 for introducing a microwave of 2.45 GHz, for example, and is connected to a microwave power source 4. The microwave power source 4 is connected to the pulse generator 5 so that its output can be arbitrarily controlled from a pulsed waveform to a continuous waveform. Further, for example, an inert gas such as He and methane trifluoride (CH
A first inlet 6 for introducing a reactive gas (A) such as F ₃ ) is attached to the discharge chamber 2. 7 is the discharge chamber 2
Is a cooling mechanism provided for water-cooling the outer wall of the above, and a magnetic coil 8 is attached to the outside of the cooling mechanism 7 so as to surround the discharge chamber 2. A microwave causes a discharge in the discharge chamber 2, and a magnetic field of, for example, about 875 Gauss is applied by the magnetic coil 8 so that electrons are cyclotron-moved in the discharge, and high-density plasma is generated.

On the other hand, an electrode 9 as a sample holder is installed inside the vacuum container 1, and a wafer or the like as a substrate 10 to be processed is placed on the electrode 9. A high frequency power source 12 for applying high frequency bias power is connected to the electrode 9 via a matching circuit 11. High frequency power 12
Is connected to a pulse generator 13 so that the output can be arbitrarily controlled from a pulse waveform to a continuous waveform. Therefore, a bias of minus several tens to minus 300 V is generated on the electrode 9 by applying the high frequency. 14 is a substrate to be processed which is provided through the inside of the electrode 9.
It is a cooling water cooling tube for cooling 10. Further, the vacuum container 1 is provided with a second inlet 15 for introducing an inert gas such as He and a reactive gas (B) such as methane trifluoride (CHF ₃ ) and is evacuated. An exhaust pipe 16 leading to the device 17 is connected. Each inlet 6,
A certain amount of raw material gas is introduced from 15 and is exhausted by the vacuum exhaust device 17 so that the inside of the device vacuum container 1 and the discharge chamber 2 is maintained at a predetermined gas pressure.

Trifluoromethane (C) introduced into the discharge chamber 2
HF ₃ ) becomes plasma P, and F, CF, CF ₂ , C
Radicals R such as F ₃ are generated. The plasma P extends from the discharge chamber 2 into the vacuum container 1. The radicals R generated from the plasma P are polymerized on the substrate 10 to be processed, and a polymer thin film grows. On the other hand, the substrate 10 to be processed
When a high-frequency output is applied from 12, a high-bias voltage induces a self-bias voltage on the surface of the substrate 10 to be processed, and the bias voltage causes ions to be extracted from the plasma to bombard the substrate 10 to be processed. The ion bombardment causes etching of the substrate 10 to be processed. Further, by appropriately adjusting the output of the high frequency power source 12, it is possible to generate plasma on the surface of the substrate to be processed 10 by applying high frequency.

The microwave output generated from the microwave power source 4 is modulated by the pulse generator 5, the high frequency output generated by the high frequency power source 12 is modulated by the pulse generator 13, or the microwave output and the high frequency output are modulated. It is possible to control the density and composition of the radicals R in the vacuum container 1 by time-dividing the addition and combining them appropriately.

The reason for providing the second reactive gas inlet is that, for example, in FIG. 1, the first reactive gas A is directly introduced into the discharge chamber 2 through the gas inlet 6. Discharge chamber 2
In the above, electric discharge is generated by microwave and high density plasma is generated. The plasma diffuses toward the electrode 9 due to the magnetic field. The plasma density and electron temperature also gradually decrease from the discharge chamber 2 toward the electrode 9.

Therefore, since the first reactive gas A is first introduced into the discharge chamber 2 of high density plasma, the decomposition rate of the gas is also high, and the gas is decomposed to lower order atoms.

On the other hand, the second reactive gas B supplied to the second gas introduction port 15 is introduced into the vacuum vessel 1 from the lower part of the discharge chamber 2 through the second reactive gas introduction port 15. As described above, the second reactive gas introduction port 15 contacts the plasma diffused from the high density plasma. Plasma in this region is discharged in the discharge chamber 2
The characteristic is that the electron temperature is lower (that is, lower energy) than that of the plasma in.

Therefore, when the second reactive gas is introduced from the second reactive gas inlet 15, the decomposition of the second reactive gas is slightly lower than the decomposition of the first reactive gas. Will be things.

As described above, a gas is selected for plasmas having different energies (plasma having different electron temperatures),
By appropriately introducing the gas from the first reactive gas introducing port 6 or the second reactive gas introducing port 15, respectively, various reactions can be selectively caused.

In the present invention, what kind of gas is intended to be introduced as the second reactive gas into the vacuum container 1 and what kind of reaction is to be performed is described in Examples 1 to 1.
3, CHF ₃ and C as the first reactive gas
An inert gas such as HF ₃ / He is introduced. Essentially, in the first and second embodiments, CHF ₃ and CHF are supplied from the second gas inlet 15 instead of the first gas inlet 6.
_{Even if} a mixture of ₃ and He or the like is introduced, a similar effect is expected. In addition, since decomposition and dissociation is suppressed when gas is introduced from the second gas introduction port 15, the composition of radicals differs from that when introduced from the first gas introduction port 6 depending on the selection of gas.

Next, in the following process, various changes occur between the first gas inlet 6 and the second gas inlet 15. First
From the gas inlet 6 of, for example, an inert gas (He, N
It is also possible to introduce e, Ar, Xe, Kr) or H _{2 and} to introduce a reactive gas such as CHF ₃ from the second inlet 15.

First, when CHF ₃ is introduced from the first gas introduction port 6, the microwave is introduced into the microwave introduction port as shown in FIG. 1 (immediately below the microwave indicated by the arrow in the figure) because of the high decomposition of the gas.
The deposited film adheres to the microwave introduction window 19 installed in the window 19 due to radicals and the like generated by the decomposition of CHF ₃ and stains it.
If this pollution becomes large, the efficiency of microwave introduction is reduced and the discharge becomes unstable.

On the other hand, when an inert gas or H ₂ is introduced through the first inlet 6, CHF ₃ (gas B) introduced through the second gas inlet 15 flows down due to the flow of these gases (A). No contamination of the window 19 occurs since it is not introduced into the 2.

Further, the inert gas or H ₂ introduced through the first gas inlet 6 is decomposed by the plasma having a high electron temperature, and ions of He, Ar, Ne, Xe, Kr and He are introduced.
Metastable atoms of ^* , Ar ^* , Ne ^* , Xe ^* , Kr ^* are generated. Also, H atoms are generated rather than H ₂ .

Therefore, the CHF ₃ (gas (B)) introduced through the second gas inlet 15 is mildly decomposed by the plasma having a relatively low electron temperature, and metastable atoms (He ^* , Ne ^* , Ar ^* , Kr ^* , X
e ^* ) or the reaction between H atom and CHF ₃ becomes dominant. When the ratio of the collision reaction with other atoms such as the latter becomes large, the reaction with that decomposed by plasma changes greatly, and the density and composition of the radicals generated also change.

Further, as in the third embodiment, a second electrode 18 formed of a mesh or the like is inserted, and an inert gas is introduced through the first gas inlet 6 and a reactive gas is introduced through the second gas inlet 15. When (CHF ₃ ) is introduced, plasma and ions are removed at the electrode 18, so that He ^* , Ne ^* , Ar ^* , generated by the decomposition of the inert gas, is generated at the electrode 9 of the vacuum container 1.
Metastable atoms having a long life of Kr ^* and Xe ^* and radicals generated by the reaction of these metastable atoms with CHF ₃ gas are introduced into the electrode 9. At this time, CHF ₃ is not decomposed by plasma, but is decomposed by collision with metastable atoms, and thus the radical characteristics generated also change.

Also in this case, since the temporal density of the metastable atoms is changed by changing the on / off duty ratio of the plasma, CHF ₃ is decomposed and the composition of the generated radicals is also changed. Is possible.

Finally, H ₂ does not easily decompose and requires high energy (high electron temperature). Therefore, H
By introducing ₂ from the gas introduction port 6, H atoms are efficiently formed, and H atoms and the gas introduction port 6 or the gas introduction port 15 are formed.
It is also possible to control the composition of radicals and the like by the reaction with the CHF ₃ gas introduced further.

As described above, the gas inlet 6 or the gas inlet
What kind of gas is introduced into 15 can be appropriately selected according to the process.

[0027]

【Example】

[Embodiment 1] Next, an EC shown in FIG. 1 as a first embodiment.
A radical control method relating to a fluorocarbon thin film deposition method using the R plasma processing apparatus will be described. First, methane trifluoride (CHF ₃ ) was placed in the discharge chamber 2 of the apparatus shown in FIG.
Is introduced and the pressure of CHF ₃ is maintained at 0.4 Pa. Microwave input power is 300 W, flow rate is 5.0 sccm,
The cycle is set to 100 msec, and the duty ratio of the output of the microwave power source is 15 to 100% (continuous) by the pulse generator 5.
The plasma on / off modulation was performed. In this case, a Si substrate was used as the substrate 10 to be processed, and no high frequency was applied. Sum of ON period and OFF period is 100 ms
It was fixed at.

Using an infrared semiconductor laser absorption spectroscope (not shown) installed in the vacuum container 1, 2 cm of the substrate 10 to be processed
The radical densities of CF, CF ₂ and CF _{3 in} the upper part were measured.

2 and 3 show examples of the results obtained by applying the present invention. It can be seen from FIG. 2 that the CF, CF ₂ and CF ₃ radical densities are increased by performing on / off discharge rather than continuous discharge. The CF ₃ radical increases slightly with the increase of the ON period, but the ON period is 70 mse.
It gradually decreases above c. That is, the change in density was small with respect to the change in the ON-OFF period, and it was observed that the density was slightly decreased in continuous discharge. On the other hand, CF
₂₎ It was found that the density of CF radicals was 3 times and 4 times larger when the ON period was 15 ms than when discharging continuously. Decreases rapidly with increasing on-time, on-time 50
Saturates over msec. From this, it was found that it is possible to control the radical density and composition in the ECR plasma by changing the duty ratio.

FIG. 3 shows the on / off modulation duty ratio dependence of the fluorocarbon film deposited on Si and SiO ₂ . The plasma treatment time is 120 minutes.
No difference in the deposited film thickness was observed in the difference between the Si and SiO ₂ substrates. The deposited fluorocarbon film thickness increases with the duty ratio. On the other hand, the deposition rate (film thickness of the deposited fluorocarbon / (discharge time 12
It was found that 0 min × duty ratio)) decreases with the duty ratio. There is a correlation between the deposition rate and the CF ₂ and CF radical densities, and it is possible to control the film thickness of radicals in plasma and the deposition rate by changing the duty ratio.

[Embodiment 2] Next, a radical control method relating to an etching method using the above-mentioned ECR plasma processing apparatus will be described as a second embodiment. First, methane trifluoride (CHF ₃ ) is introduced into the discharge chamber 2 and the pressure is kept at 0.4 Pa. The microwave has a cycle of 100 sec, the microwave power output is time-divided by the pulse generator 5, and the duty ratio is 1 to 10 at microwave powers of 400 W and 100 W.
The microwave power was modulated by changing it to 0% (continuous). In this case, as the substrate 10 to be processed, one having an appropriate etching pattern formed on SiO ₂ was used. The substrate 10 to be processed is biased by applying harmonics of 13.56 MHz.
A voltage of 100 V was applied to the surface of the substrate 10 to be processed. In this case, as in the case of Example 1, the substrate to be processed was processed using an infrared semiconductor laser absorption spectroscope (not shown) installed in the vacuum container 1.
The CF, CF ₂ , and CF ₃ radical densities at the upper part of 10 cm were measured. It was found that the CF, CF ₂ and CF ₃ radicals behaved in Example 1 much like those shown in FIG.

FIG. 4 shows an example of the etching result obtained by applying the present invention. That is, FIG. 4 shows the relationship between the etching rate of SiO ₂ and the processed shape. The plasma processing time in this case is 5 minutes. The etching rate increases with the duty ratio. On the other hand, it can be seen that the processed shape becomes a vertical shape with the duty ratio. From this, it is possible to control radicals in plasma and etching shape by changing the duty ratio.

[Third Embodiment] Next, a radical control method relating to an etching method using a radical beam apparatus will be described as a third embodiment. FIG. 5 shows a radical beam device used in the third embodiment. 5, parts that are the same as those shown in FIG. 1 are given the same reference numerals, and descriptions thereof will be omitted. In the ECR plasma processing apparatus shown in FIG. 5, a second electrode formed by a mesh between the vacuum container 1 and the vacuum container 2.
Inserted 18. The second electrode 18 removes charged particles such as ions and electrons generated from plasma in the discharge chamber 2 by applying appropriate positive and negative biases, and guides only radicals to the vacuum container 1. Is possible.

First, in this example, as in Example 2, methane trifluoride (CHF ₃ ) was introduced into the discharge chamber 2,
Keep the pressure at 0.4 Pa. Microwave has a cycle of 100 msec
The microwave power was time-divided and 400 W and 100 W were alternately introduced. The pulse generator 5 changed the microwave power supply output to a duty ratio of 15 to 100% (continuous) to perform plasma power modulation. In this case, SiO ₂ was used as the substrate 10 to be processed. 13.56 to substrate 10
A high frequency of MHz was applied to generate a harmonic discharge with a high frequency power of 500 W to generate plasma. As a result, a bias voltage of 200 V is applied to the surface of the substrate 10 to be processed. Further, the high frequency application was continued without the pulse generator 13 modulating the pulse.

In this example, as in Example 1, an infrared semiconductor laser absorption spectroscope (not shown) installed in the vacuum container 1 was used to remove CF, 2 cm above the substrate 10 to be processed.
The CF ₂ and CF ₃ radical densities were measured. CF, CF
The duty ratio dependence of ₂ , CF ₃ radicals was similar to the result of Example 1 shown in FIG. From this, it is understood that it is possible to form a radical beam whose radical composition can be arbitrarily changed.

That is, FIG. 6 shows an example of the etching result obtained by applying the present invention. That is, FIG.
The relationship between the etching rate of O ₂ and the processed shape is shown.
The plasma treatment time is 5 minutes. The etching rate increases with the duty ratio. On the other hand, it can be seen that the processed shape becomes a vertical shape with the duty ratio. From this, it was found that the radicals in the plasma and the etching shape can be controlled by changing the duty ratio.

[0037]

According to the present invention, since the density and composition of radicals generated from plasma can be controlled with high precision, high-quality thin film materials with controlled radicals and high-precision fine-grained materials can be used in plasma CVD and plasma etching processes. It is possible to generate a processed thin film. For example, plasma CV
A plasma etching apparatus or microwave obtained by capacitively coupling or inductively coupling high-frequency application of a halogen gas such as fluorocarbon gas or the like in a process of forming an amorphous silicon and microcrystalline silicon thin film, a diamond thin film, a silicon compound by D. It can be applied to a dry etching process using a plasma etching apparatus that generates plasma.

Further, plasma CVD in which radicals are controlled
It becomes possible to provide an apparatus and a plasma etching apparatus. Further, there is a great industrial advantage that it is possible to provide a radical beam device in which the radical composition can be arbitrarily changed.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing the configuration of an apparatus showing an example of implementation of the apparatus of the present invention.

FIG. 2 is a characteristic diagram showing the relationship between the radical density and the on-off period measured in Example 1 using the device of the present invention.

FIG. 3 is a characteristic diagram showing the relationship between polymer thickness and on-off period measured in Example 1 using the device of the present invention.

FIG. 4 (A) is a characteristic diagram showing the relationship between the etching rate and the period and taper angle measured in Example 2 using the device of the present invention, and FIG. 4 (B) is the device of the present invention. 5 is a characteristic diagram showing the relationship between the etching rate measured in Example 2, and the period and taper angle. FIG.

FIG. 5 is a schematic view showing the configuration of an apparatus showing another example of implementation of the apparatus of the present invention.

FIG. 6 is a characteristic diagram showing the relationship between the etching rate and the period measured in Example 3 using the device of the present invention.

[Explanation of symbols]

 1 Vacuum Container 2 Discharge Chamber 3 Waveguide 4 Microwave Power Supply 5 Pulse Generator 6 First Reactive Gas Inlet 7 Water Cooling Mechanism 8 Magnetic Coil 9 First Electrode 10 Processed Substrate 11 High Frequency Matching Circuit 12 High Frequency Power Supply 13 Pulse Generator 14 Cooling water cooling pipe 15 Second reactive gas inlet 16 Exhaust pipe 17 Vacuum exhaust device 18 Second mesh electrode 19 Window P Plasma R Radical

Claims (4)

[Claims] 1. In a plasma formed by applying high frequency, direct current or microwave or electron beam, the high frequency, direct current or microwave or electron beam power is pulse-modulated at a constant cycle, and the pulse modulation is performed. A method for controlling radicals, characterized in that the reactive gas is decomposed by changing the duty ratio, and the density and composition of radicals generated by the decomposition of the reactive gas are controlled. 2. The reactive gas comprises fluorocarbon gas, hydrogenated silicon gas containing at least silicon atoms and hydrogen atoms, hydrogenated carbon gas containing at least carbon atoms and hydrogen atoms, or halogen. A method for controlling the described radicals. 3. A plasma discharge chamber connected to a microwave generation power source having a pulse generator by a waveguide, a vacuum container connected to the plasma discharge chamber, and a vacuum exhaust device connected to the other of the vacuum containers. A substrate to be processed provided facing the plasma emitted from the plasma discharge chamber, a first electrode supporting the substrate to be processed, and a pulse generator for the first electrode supporting the substrate, and high frequency matching A high frequency or direct current or microwave or electron beam power source connected via a circuit, a water cooling pipe system for water cooling the first electrode, a magnetic coil provided around the plasma discharge chamber, and a water cooling mechanism. A first reactive gas inlet provided in the discharge chamber, applying microwave to the reactive gas supplied to the plasma discharge chamber,
Radicals resulting from the decomposition of reactive gas by forming plasma and subjecting the high frequency, direct current, microwave or electron beam power to pulse modulation at a constant cycle and changing the duty ratio of the pulse modulation to decompose the reactive gas. A device for controlling radicals, which is configured to control the density and composition of the radical. 4. A plasma discharge chamber connected to a microwave generating power source having a pulse generator by a waveguide, a vacuum container connected to the plasma discharge chamber, and an evacuation device connected to the other of the vacuum containers. A substrate to be processed provided facing the plasma emitted from the plasma discharge chamber, a first electrode supporting the substrate to be processed, and a pulse generator for the first electrode supporting the substrate, and high frequency matching A high frequency or direct current, or microwave or electron beam power source connected via a circuit, a water cooling pipe system for water cooling the first electrode, a magnetic coil provided around the plasma discharge chamber, and a water cooling mechanism. And a first reactive gas inlet provided in the discharge chamber,
A mesh-shaped second member is provided between the plasma discharge chamber and the vacuum container.
An electrode is provided and a second reactive gas inlet is provided on the side wall of the container so that charged particles such as ions and electrons generated from plasma in the plasma discharge chamber can be removed and only radicals can be guided. Characteristic radical control device.