JPH04306597A - Plasma generating device and method for controlling it - Google Patents

Abstract

PURPOSE:To control the self-bias generated at a high frequency electrode into a constant value with the zenor voltage of a zenor diode irrespective of the supplied power by connecting zenor diode between the high frequency electrode and earth electrode, and thereby forming a DC constant voltage circuit. CONSTITUTION:A vacuum trough 1 is fitted with a high frequency electrode 4 through a gas lead-in hole 3 and electric insulation, and the electrode 4 holds a material to be processed 5. A high frequency power supply 7 is connected with a high frequency matching circuit 8 through a coaxial cable 11, and the circuit 8 is connected to the electrode 4 through a Cu plate 14, and the peripheral line of the cable 11 is connected with the vacuum trough 1 as earth electrode. Then the high frequency electrode 4 is grounded via a LPF 9 and a zenor diode 10. Thereby the self-bias can be controlled constant only by supplying a certain value or more of high frequency power, and the value of self-bias be set with the zenor voltage of this diode 10.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for forming, etching, and processing thin films using plasma, and a method for controlling the same.

0002

2. Description of the Related Art In each plasma generation apparatus for sputtering, etching, and plasma processing, a negative self-bias is generated in a high-frequency electrode that applies high-frequency waves. The value of this self-bias is determined by the structure of the electrode, the area ratio between the electrode and the ground,
Varies depending on gas type, pressure, high frequency power, etc. Furthermore, even if these process conditions are kept constant, they will vary irregularly depending on the history of the equipment.

[0003] Keeping this self-bias constant is important in terms of stabilizing the process, and therefore there is a well-known method of monitoring the self-bias and changing the high-frequency power so that the measured value is always constant. It is being

On the other hand, when the electrode for applying high frequency or DC power and the substrate holder for holding the material to be processed are provided separately, self-bias (floating) generated on the surface of the substrate holder containing the material to be processed (potential) tends to be ignored, and the potential is only consciously recognized when a bias is actively applied from the outside.

[0005]

[Problems to be Solved by the Invention] However, the above-mentioned prior art method of varying the high frequency power in order to keep the self-bias generated in the high frequency electrode constant, is a plasma generation source itself. The magnitude of the applied power is the biggest factor that determines the plasma density, and as a result, there is a problem that the characteristics of the thin film, rate, etc. are unstable, and therefore the original purpose of stabilizing the process is not satisfactory. I couldn't say that.

On the other hand, even when an electrode for applying high frequency or direct current power and a substrate holder for holding the material to be processed are provided separately, and no bias is applied from the outside to the substrate holder containing the material to be processed, When the treated material is exposed to plasma, a self-bias (floating potential) is generated on its surface, and its value influences the properties of the thin film. However, this value is often ignored, and even if its significance is acknowledged, its control
This method uses a method of varying the applied power of high frequency or direct current, which is the source of the plasma mentioned above, and has the same problem that the characteristics, rate, etc. of the thin film are unstable.

The present invention is intended to solve these problems, and its purpose is to eliminate the self-bias generated on the surface of the material to be treated or the surface of the high-frequency electrode, regardless of the magnitude of applied DC or high-frequency power. An object of the present invention is to provide a device and a control method for keeping the self-bias generated in a constant value at an arbitrary value.

[0008]

[Means for Solving the Problems] The plasma generating device of the present invention is characterized by the following features.

[0009] In an apparatus for generating plasma by flowing gas through a vacuum chamber provided with a high frequency electrode and applying a high frequency between the vacuum chamber, which is a ground electrode, and the high frequency electrode,
A Zener diode is connected between the high frequency electrode and the ground electrode.
connected.

[0010] Furthermore, gas is caused to flow through a vacuum chamber provided with a high-frequency electrode and a substrate holder that holds the material to be processed separately, and a high-frequency wave is generated between the vacuum chamber, which is a ground electrode, and the high-frequency electrode. In the apparatus which generates plasma by applying a voltage, a Zener diode is connected between the substrate holder and the earth electrode.

Furthermore, gas is caused to flow through a vacuum chamber provided with a DC electrode and a substrate holder that holds the material to be processed separately, so that a DC current is generated between the vacuum chamber, which is a ground electrode, and the DC electrode. In an apparatus for generating plasma by applying a voltage, a Zener diode is connected between the substrate holder and a ground electrode.

On the other hand, the method for controlling a plasma generator according to the present invention is characterized by the following features.

[0013] In the control method of an apparatus for generating plasma by flowing gas into a vacuum chamber provided with a high-frequency electrode and applying a high-frequency wave between the vacuum chamber, which is a ground electrode, and the high-frequency electrode, the high-frequency A Zener diode is connected between the electrode and the ground electrode to form a DC constant voltage circuit, and the self-bias generated in the high-frequency electrode is controlled regardless of the magnitude of the high-frequency power applied to the high-frequency electrode. Control so that it remains constant.

[0014] Furthermore, gas is caused to flow through a vacuum chamber provided with a high-frequency electrode and a substrate holder that holds the material to be processed separately, and a high-frequency wave is generated between the vacuum chamber, which is a ground electrode, and the high-frequency electrode. In a method of controlling an apparatus that generates plasma by applying a voltage, a Zener diode is connected between the substrate holder and a ground electrode to form a DC constant voltage circuit, and a high frequency voltage is applied to the high frequency electrode. To control the self-bias generated in the substrate holder to be constant regardless of the magnitude of electric power.

Furthermore, gas is caused to flow through a vacuum chamber provided with a DC electrode and a substrate holder that holds the material to be processed separately, so that a DC current is generated between the vacuum chamber, which is a ground electrode, and the DC electrode. In a method for controlling an apparatus that generates plasma by applying a voltage, a Zener diode is connected between the substrate holder and a ground electrode to form a DC constant voltage circuit, and a DC voltage is applied to the electrode. The self-bias generated in the substrate holder is controlled to be constant regardless of the magnitude of DC power and DC voltage.

[0016]

[Operation] According to the above structure of the present invention, by connecting a Zener diode between the high frequency electrode and the earth electrode to form a DC constant voltage circuit, the self-bias generated in the high frequency electrode can be eliminated. can be controlled to be constant by the Zener voltage of the Zener diode, regardless of the magnitude of the power applied to the high frequency electrode.

[0017] Furthermore, when the electrode for applying high frequency or DC power and the substrate holder for holding the material to be processed are provided separately, the gap between the substrate holder for holding the material to be processed and the ground electrode By connecting a Zener diode to the electrode to form a DC constant voltage circuit, the self-bias (floating potential) generated on the surface of the substrate holder containing the material to be processed can be controlled by the high frequency or DC power applied to the electrode. Regardless of the magnitude, the Zener voltage of the Zener diode can be controlled to be constant.

[0018]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be explained in detail below with reference to the drawings. FIG. 1 is a schematic diagram showing an embodiment of the present invention used in reactive ion etching.

A high frequency electrode 4 is provided in the vacuum layer 1 with a gas inlet 3, a vacuum exhaust port 2, and an insulator 6 interposed therebetween. In reactive ion etching, the high frequency electrode 4 also serves as a substrate holder, and thus holds the material to be processed 5 (substrate). High frequency matching circuit 8 from high frequency power supply 7 to coaxial cable 11
Then, the high frequency matching circuit 8 is connected to the high frequency electrode 4 through a copper plate 14, respectively. The outer peripheral line of the coaxial cable 11 is connected to the vacuum layer 1 which is a ground electrode. Up to this point, the general reactive ion etching apparatus shown in FIG. 7 is the same as the conventional one. In the present invention, the high frequency electrode 4 is connected to earth through a low pass filter 9 and further through a Zener diode 10. This is a major feature.

With such a configuration, after the vacuum layer is evacuated,
First, a mixed gas of freon and oxygen is flowed through the gas inlet 3. The pressure is kept constant based on the relationship between the gas flow rate and the effective pumping speed of the vacuum exhaust port 2: pressure=gas flow rate/effective pumping speed.

High frequency power is applied to the high frequency electrode 4 via the high frequency matching circuit 8. The high frequency matching circuit 8 is for preventing loss of high frequency power supplied from the high frequency power supply 7 to the high frequency electrode 4, and generally performs impedance matching using a coil and two capacitors.

After the discharge starts, a self-bias is generated in the high-frequency electrode 4. This is due to the difference in mobility between electrons and ions, and as a result, the potential on the surface of the high-frequency electrode 4 becomes a superposition of the high-frequency voltage and the negative DC voltage that is a self-bias. A low-pass filter 9 is attached to remove this high frequency voltage component. The effects of self-bias on devices are thought to include electrical damage caused by charge-up on the substrate surface, or physical damage caused by accelerating ions incident on the substrate. Therefore, it is desirable that the self-bias potential is small, but if it is too small, it will be difficult to align the direction of the ions incident on the substrate, making it difficult to perform anisotropic etching, which is the original purpose of reactive ion etching. . Therefore, it would be ideal to control the potential at a certain level and at a constant level.

In this embodiment, a Zener diode 10 having a Zener voltage equal to the self-bias value that is desired to be constant is connected between the high frequency electrode 4 and the earth electrode.
We can make it happen.

As shown in FIG. 6, as the high frequency power applied to the high frequency electrode 4 is increased, discharge starts at 20 W and a slight self-bias occurs. At about 30W, the self-bias value becomes equal to the Zener voltage. As the high-frequency power is further increased, the self-bias becomes larger than the Zener voltage. However, when the Zener voltage is exceeded, the electrons forming the self-bias flow to the ground, so the value of the self-bias becomes equal to the Zener voltage. Therefore, it becomes possible to control the self-bias to a constant level regardless of the high frequency power. In the conventional device shown in FIG. 7, the self-bias monotonically increases as the high frequency power increases, as shown in FIG. It is possible to control the self-bias by changing the high frequency power, but in order to control it at a constant low value, the high frequency power must also be reduced, which reduces the etching rate and changes the high frequency power. This caused fluctuations in the etching rate.

In this embodiment, it is possible to control the self-bias to a constant level simply by applying high-frequency power above a certain value, and the value of the self-bias is determined by the Zener voltage of the Zener diode 10 used. It can be set with . Therefore, high frequency power can be sufficiently applied, and the etching rate does not decrease or fluctuate.

Another embodiment of the invention is shown in FIG.

A high frequency electrode 4 is provided in the vacuum layer 1 with a gas inlet 3, a vacuum exhaust port 2, and an insulator 6 interposed therebetween. Material to be treated 5
A substrate holder 12 for holding a substrate is attached to a part of the vacuum layer 1 separately from the high-frequency electrode 4 and via an insulator 13. The high frequency power supply 7 is connected to the high frequency matching circuit 8 by a coaxial cable 11, and the high frequency matching circuit 8 is connected to the high frequency electrode 4 by a copper plate 14, respectively. The outer peripheral line of the coaxial cable 11 is a vacuum layer 1 which is a ground electrode.
Connect to. Up to this point, the apparatus is a general plasma ion etching apparatus, sputtering apparatus, and plasma processing apparatus, and is the same as the conventional one. When discharge is performed with such a configuration, a self-bias called a floating potential is generated on the surface of the substrate holder 12 including the material to be processed 5. This self-bias also causes electrical and physical damage to the device as described above. However, if the self-bias is reduced to zero, that is, if the substrate holder 12 is grounded, abnormal discharge may occur on the surface of the processed material 5 or the substrate holder 12, or desired characteristics may not be obtained. As mentioned above, it is necessary to control the potential to a certain degree and to keep it constant.

The present invention solves this problem by connecting the substrate holder to earth through a low-pass filter 9 and further through a Zener diode 10. This is a major feature.

As the high frequency power applied to the high frequency electrode 4 increases, the self-bias on the surface of the substrate holder 12 containing the material to be processed 5 increases. As described above, when the Zener voltage is exceeded, the electrons forming the self-bias flow to the ground, so the value of the self-bias becomes equal to the Zener voltage. Therefore, it becomes possible to control the self-bias to a constant level regardless of the high frequency power. Therefore, the self-bias can be set independently as a process condition, and no adverse effects such as rate fluctuations will occur. The self-bias generated on the surface of the substrate holder 12 containing the material to be processed 5 may exhibit a positive polarity depending on the device structure, gas type, gas pressure, etc. If the positive polarity is to be kept constant, the Zener diode 10 used may be connected in reverse.

Yet another embodiment is shown in FIG.

A gas inlet 3, a vacuum exhaust port 2, and a DC electrode 17 are provided in the vacuum layer 1 via an insulator 6. Material to be treated 5
A substrate holder 12 for holding a substrate is attached to a part of the vacuum layer 1 separately from the DC electrode 17 and via an insulator 13. A DC power supply 15 is connected to the DC electrode 17 with a high voltage cable 16. Up to this point, it is a general sputtering apparatus and is the same as the conventional one.

Even in the case of direct current discharge with such a configuration, self-bias is generated on the surface of the substrate holder 12 containing the material to be processed 5, as described above, and it is desired to stabilize the process by controlling this bias.

Therefore, the present invention similarly provides a Zener diode 10 between the substrate holder 12 containing the material to be processed 5 and the ground.
Connect to solve this problem.

As the DC power applied to the DC electrode 17 increases, the self-bias on the surface of the substrate holder 12 containing the material to be processed 5 increases toward the negative side. Same as above Zener
When the voltage is exceeded, the electrons forming the self-bias flow to ground, so the value of the self-bias becomes equal to the Zener voltage. Therefore, it is possible to control the self-bias to a constant level regardless of the applied DC power. Therefore, the self-bias can be set independently as a process condition, and no adverse effects such as rate fluctuations will occur. The embodiments described above include a substrate holder that holds a material to be processed;
This is to control the self-bias of the surface of the high-frequency electrode that also serves as a substrate holder, that is, the surface of the material to be processed. The embodiment shown in FIG. 4 controls the self-bias of a high-frequency electrode that does not hold a substrate (a high-frequency electrode that also serves as a substrate holder).

A high frequency electrode 4 is provided in the vacuum layer 1 with a gas inlet 3, a vacuum exhaust port 2, and an insulator 6 interposed therebetween. Material to be treated 5
A substrate holder 12 for holding a substrate is attached to a part of the vacuum layer separately from the high frequency electrode 4 and via an insulator 13. A coaxial cable 11 connects a high frequency power source 7 to a high frequency matching circuit 8, and from the high frequency matching circuit 8 to a copper plate 1.
4 are respectively connected to the high frequency electrode 4. The outer peripheral line of the coaxial cable 11 is connected to the vacuum layer 1 which is a ground electrode. The high frequency electrode 4 is connected to the ground through a low pass filter 9 and a Zener diode 10.

With this configuration, the self-bias generated on the surface of the high-frequency electrode 4 is controlled independently of the high-frequency power applied. The theory is the same as above.

If the apparatus and control method of this embodiment are used for surface treatment, it is possible to increase the plasma density, that is, increase the applied high frequency power, without causing sputtering at the high frequency electrode 4, that is, to reduce the self-bias. It becomes possible.

Further, when used in a sputtering apparatus, it is useful for stabilizing the self-bias on the target surface and indirectly controlling the self-bias generated on the surface of the material to be processed.

The configuration shown in FIG. 5 can also be considered as an application example of the present invention. A high frequency power source 7 and a Zener diode 10 are connected to the high frequency electrode 4 as before. The self-bias generated on the surface of the high-frequency electrode 4 is controlled independently of the high-frequency power applied. A high frequency power source 21 is also connected to the substrate holder 12 holding the material 5 to be processed through the coaxial cable 2.
5. Connect via the high frequency matching circuit 22. Further, the substrate holder 12 includes a low-pass filter 23 and a Zener filter.
It is grounded to earth via a diode 24. and,
The self-bias generated on the surface of the substrate holder 12 containing the material to be processed 5 is controlled independently of the high-frequency power applied. By independently controlling each process condition in this way, a more stable process can be created.

[0040]

As described above, according to the present invention, according to the above structure of the present invention, a DC constant voltage circuit is constructed by connecting a Zener diode between a high frequency electrode and a ground electrode. By forming this, the self-bias generated in the high-frequency electrode can be controlled to be constant by the Zener voltage of the Zener diode, regardless of the magnitude of the power applied to the high-frequency electrode.

[0041] Furthermore, when the electrode for applying high frequency or DC power and the substrate holder for holding the material to be processed are provided separately, the gap between the substrate holder for holding the material to be processed and the ground electrode. By connecting a Zener diode to the electrode to form a DC constant voltage circuit, the self-bias (floating potential) generated on the surface of the substrate holder containing the material to be processed can be controlled by the high frequency or DC power applied to the electrode. Regardless of the magnitude, the Zener voltage of the Zener diode can be controlled to be constant.

By independently controlling the self-bias in this way, it has the effect of keeping the process more stable and the effect of encouraging the creation of new processes and devices.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram 1 showing one embodiment of the present invention.

FIG. 2 is a schematic diagram 2 showing one embodiment of the present invention.

FIG. 3 is a schematic diagram 3 showing one embodiment of the present invention.

FIG. 4 is a schematic diagram 4 showing one embodiment of the present invention.

FIG. 5 is a schematic diagram 5 showing one embodiment of the present invention.

FIG. 6 is a diagram showing the relationship between high frequency power and self-bias according to the present invention.

FIG. 7 is a schematic diagram showing a conventional example.

FIG. 8 is a conventional relationship diagram between high frequency power and self-bias.

[Explanation of symbols]

1: Vacuum layer 2: Vacuum exhaust port 3: Gas inlet 4: High frequency electrode 5: Material to be treated 6, 13: Insulator 7, 21: High frequency power supply 8, 22: High frequency matching circuit 9, 23: Low-pass filter 10, 24: Zener diode 11, 25: Coaxial cable 12: Board holder 14: Copper plate 15: DC power supply 16: High voltage cable 17: DC electrode

Claims (6)

[Claims] 1. In an apparatus for generating plasma by flowing gas through a vacuum chamber provided with a high-frequency electrode and applying a high frequency between the vacuum chamber, which is a ground electrode, and the high-frequency electrode, the high-frequency electrode 1. A plasma generating device characterized in that a Zener diode is connected between the electrode and the ground electrode. 2. A method for controlling an apparatus that generates plasma by flowing gas through a vacuum chamber provided with a high-frequency electrode and applying a high frequency between the vacuum chamber, which is a ground electrode, and the high-frequency electrode, comprising: A Zener diode is connected between the high frequency electrode and the earth electrode to form a DC constant voltage circuit,
Regardless of the magnitude of the high frequency power applied to the high frequency electrode,
A method for controlling a plasma generator, comprising controlling the self-bias generated in the high-frequency electrode to be constant. 3. Gas is caused to flow through a vacuum chamber provided with a high-frequency electrode and a substrate holder that holds a material to be processed separately, and a high-frequency wave is generated between the vacuum chamber, which is a ground electrode, and the high-frequency electrode. In a device that generates plasma by applying
A Zener diode is connected between the substrate holder and the ground electrode.
A plasma generator characterized in that a cord is connected to the plasma generator. 4. Gas is caused to flow through a vacuum chamber provided with a high-frequency electrode and a substrate holder that holds a material to be processed separately, and a high-frequency wave is generated between the vacuum chamber, which is a ground electrode, and the high-frequency electrode. In a method of controlling an apparatus that generates plasma by applying a voltage, a Zener diode is connected between the substrate holder and a ground electrode to form a DC constant voltage circuit, and a high frequency voltage is applied to the high frequency electrode. A method for controlling a plasma generator, characterized in that the self-bias generated in the substrate holder is controlled to be constant regardless of the magnitude of electric power. [Claim 5] A gas is caused to flow through a vacuum chamber provided with a DC electrode and a substrate holder that holds the material to be processed separately.
In the apparatus for generating plasma by applying a DC voltage between the vacuum chamber, which is a ground electrode, and the DC electrode, a Zener diode is connected between the substrate holder and the ground electrode. A plasma generating device characterized by the following. [Claim 6] A gas is caused to flow through a vacuum chamber provided with a DC electrode and a substrate holder that holds the material to be processed separately.
In the method for controlling an apparatus that generates plasma by applying a DC voltage between the vacuum chamber, which is a ground electrode, and the DC electrode, a zener is connected between the substrate holder and the ground electrode.
A DC constant voltage circuit is formed by connecting diodes, and the self-bias generated in the substrate holder is controlled to be constant regardless of the magnitude of DC power and DC voltage applied to the DC electrode. Characteristic control method for plasma generator.