JPH0355549B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a processing apparatus using plasma generated by high frequency discharge, and mainly relates to a plasma processing apparatus for performing deposition or etching processing on a semiconductor substrate using plasma.

In order to explain the present invention, first, a conventional plasma deposition and etching method using high frequency discharge and an apparatus therefor will be described.

FIG. 1 is a block diagram of a plasma deposition apparatus using high-frequency discharge. Material gas at an appropriate pressure is introduced into the first discharge tube through the second gas introduction hole. A vacuum chamber 5 is evacuated by a vacuum evacuation system (not shown), and a substrate 6 to be deposited is held on a holding plate 7 and connected to a ground potential 8.

Now, when high frequency power is applied to the discharge tube 1 using the high frequency oscillator 3 and the discharge coil 4 inductively coupled to the high frequency oscillator 3, if the internal pressure of the discharge tube 1 is a suitable pressure of about 10 ^{-2 Torr} , a non-polar discharge will be generated inside the discharge tube. A discharge plasma 9 is generated. Now as a discharge gas,
Monosilane (SiH ₄ ) and nitrogen (N ₂ ) are introduced and the substrate 6 is heated to about 300 to 400° C. by a heating means (not shown) to deposit a silicon nitride (Si ₃ N ₄ ) film on the substrate.

FIG. 2 shows a configuration diagram of another conventional deposition apparatus. Electrodes 10 and 11 capacitively coupled to the oscillator 3 are introduced into the vacuum chamber 5 which is evacuated by a vacuum evacuation system (not shown), and the electrode 11 serves as a holding plate for the substrate 6 and is connected to the ground potential 8. Gas introduction hole 2
By introducing a more appropriate pressure and generating discharge plasma 9, a desired substance can be deposited on the substrate 6 in the same manner as in the case of FIG.

Next, FIG. 3 is a block diagram of an etching apparatus using plasma using high frequency discharge. Electrodes 10 and 11 capacitively coupled to the oscillator 3 are placed on the outside of the vacuum chamber 5, and a substrate 6 is placed on a holding plate 7 inside the vacuum chamber 5. Gas introduction hole 2
For example, freon gas (CF ₄ ) and oxygen (O ₂ )
When gas is introduced at an appropriate pressure and discharge plasma 9 is generated, the silicon substrate and silicon oxide film are etched by fluorine ions.

FIG. 4 shows another example and has a configuration similar to that in FIG. 3, but two capacitively coupled electrodes 10 and 11 are introduced into the vacuum chamber 5. A substrate 6 to be processed is attached to and held by one electrode 10, and a Freon gas at an appropriate pressure is introduced between the electrode 11 and the other electrode 11, which is held and grounded.A discharge is caused to generate plasma 9.

The discharge is a high frequency discharge (several M to several tens of MHz),
In addition, since one electrode is in contact with the plasma 9 at ground potential, ions with an energy corresponding to the wave height of the applied high frequency reach the substrate 6, which causes general sputtering, but also causes the discharge gas to become reactive. In this case, for example, fluorine ions react with an energetic fluorine ion substrate to cause reactive sputtering, thereby etching the substrate. Even if the substrate in this case is an insulator, there is no problem because high frequency is applied.

FIG. 5 summarizes the various methods shown in FIGS. 1 to 4 for the case of capacitive coupling, with particular attention paid to the ion energy reaching the substrate.

In FIG. 5, electrodes 10 and 1 are connected to the oscillator 3.
1 is capacitively coupled, and one of the electrodes 11 is 8
Assume that it is grounded. The vacuum container 5 is made of an insulating material, is evacuated by a vacuum evacuation system (not shown), and a suitable pressure gas is introduced through a gas introduction hole (not shown) and discharged by applied high frequency power to form plasma 9. do.

FIG. 5A corresponds to FIG. 3 in terms of the discharge format. The plasma 9 formed within the vacuum container is at a floating potential with respect to the outside world. Therefore, in both the case of deposition and etching, the internal energy of the plasma 9, that is, the thermal energy, reaches the substrate inserted in the vacuum container and also at a floating potential.

Figure 5B is the discharge type shown in Figures 2 and 4.
Corresponds to the figure. In this case, one electrode 11 has 8
Since the sheath is grounded and in contact with the plasma 9, the potential of the plasma becomes a potential corresponding to the internal energy Vs of the plasma, which separates the sheath from the ground potential. Therefore, when a substrate is placed on the ground side electrode 11 in FIG. arrive.

On the other hand, the ten high-frequency electrodes in FIG.
If the output voltage waveform of this oscillator is represented by Vosinwt, then this electrode 1
It changes to the potential of 0 with Vosinwt. Here, Vo is the highest value of the high frequency waveform, w is the angular frequency, and t is the time. This electrode 10 is also in contact with the plasma 10, but when averaged over time, the potential of the electrode 10 is equal to the ground potential. Therefore Vosinwt to 10
Even if a high frequency wave of 2 is applied, the potential of the plasma 9 remains at Vs on average. However, in reality the electrode 10
Since V changes with Vosinwt, the sheath between the electrode 10 and the plasma 9 increases or decreases to maintain the potential difference between the plasma and the electrode. Therefore, when the potential of the electrode 10 becomes -Vo, ions arrive from the plasma with the highest energy (Vo-Vs). Since Vo is usually on the order of several hundred volts, the substrate held on the electrode 10 is bombarded with ions having an energy of up to several hundred volts. Therefore, when performing normal deposition, the substrate is held by the electrode on the ground side as shown in Figure 2, and the ions arrive with the energy of Vs, and when performing sputtering, the substrate is held by the electrode on the high frequency side. , the ions arrive with energy of (Vs + Vo).

In the discharge type shown in FIG. 5C, one electrode 11 is located inside the vacuum chamber as a ground electrode and is in contact with the plasma 9, and the other high-frequency electrode 10 is located outside the vacuum chamber.

As in the case of FIG. 5B, the plasma potential is equal to the internal energy Vs of the plasma, and ions with energy Vs arrive on the electrode 11. Looking at the other high-frequency electrode 10, this is equivalent to the case where the high-frequency electrode 10 in FIG. 5B is covered with an insulator so that it does not come into direct contact with plasma. Since the surface potential of this insulator also changes with Vosinwt, ions with the highest energy (Vo + Vs) arrive and sputter the insulator. This is the principle of high frequency sputtering on insulators. The configuration of FIG. 1 can be considered similar to the configuration of FIG. 5C.

Considering the various deposition devices and etching devices currently in use as described above,
It can be seen that the energy of the deposition or etching ions arriving at the substrate to be processed is determined entirely by the equipment conditions at the time and is a quantity that is difficult to control. For example, in the deposition shown in FIGS. 1 and 2, the deposition energy is determined by the internal energy Vs of the plasma 9, and this internal energy is determined by the applied high frequency power and the gas pressure of the discharge. In addition, in the configuration shown in Figure 3, the energy of the etching ions is thermal energy, and in the configuration shown in Figure 4, the energy of the etching ions is determined by the high frequency voltage Vo of the high frequency oscillator, and this high frequency voltage is the voltage required for discharge. It is.

On the other hand, if the energy of ions arriving at the processing substrate from plasma formed by high-frequency discharge can be controlled, the effect is considered to be significant.

Considering the case of deposition, if thermal kinetic energy reaches the substrate, it will simply adhere to the substrate. If you heat the board. Although it is possible to obtain kinetic energy from the substrate and move it on the substrate, it is desirable that the substrate temperature during deposition be as low as possible due to limitations in device fabrication. When ions are given energy and are allowed to reach the substrate, most of that energy simply becomes thermal energy due to collision, but some (~several percent) becomes kinetic energy on the substrate and can move on the substrate. Therefore, in the case of general deposition, the deposited film can provide good step coverage over steps and small holes on the substrate. Furthermore, when the same material is deposited on the substrate, atoms arriving at the substrate can move to appropriate lattice points due to this kinetic energy, so crystal growth can be performed at a considerably low temperature. If this energy is too large, it will collide with the substrate, forming defects and causing sputtering.
A range of several tens of volts is appropriate.

Furthermore, in the configuration shown in FIG. 4, which is considered to be the case of etching, ions usually arrive at the substrate with an energy of several hundred eV, causing crystal defects in the substrate at the same time as sputtering. In particular, when etching is performed by using a reactive gas (Freon, etc.) as the discharge gas to cause reactive sputtering, ion energy of several hundred volts is not necessary, and local etching cannot be achieved at such a high voltage. When etching, the mask is etched by spatter, creating difficulties.

When performing reactive sputtering, in principle, the ion energy can be set to a value that promotes the chemical reaction;
The value is also preferably on the order of several volts to several tens of volts.

As seen from the above considerations, in an apparatus that generates plasma using high-frequency discharge and performs deposition or etching, ions can be made to arrive on a substrate with controlled energy ranging from several volts to several tens of volts. If obtained, it would be a significant advance in this process.

The present invention has been made to satisfy the above-mentioned needs, and an object of the present invention is to provide a plasma processing apparatus that can control the energy of ions that reach a substrate to be processed, thereby improving step coverage. This makes it possible to perform a deposition process that is good or has few defects, or to perform an etching process that can prevent etching due to unnecessary sputtering. The present invention will be described below with reference to the embodiment shown in FIG.

To explain the configuration of the plasma processing apparatus shown in FIG. 6, a vacuum chamber 5 evacuated by a vacuum chamber exhaust system (not shown) has an electrode 1 connected to an oscillator 3 in a capacitive manner.
0 and 11 are provided. The ground electrode 11 also serves as a holding plate for the substrate 6 to be processed and is connected to the ground potential 8 via a bias voltage source 14 according to the invention.

Gas at an appropriate pressure is introduced into the vacuum chamber through a gas introduction hole (not shown), and discharge plasma 9 is generated by high frequency power from the oscillator 3. On the other hand, the negative voltage (-V _B ) from the bias voltage source 14 is applied to the electrode 1.
1. As a result, ions having an energy of (V _B +V _S ) can be caused to arrive at the processing substrate 6 by the plasma 9 . That is, bias voltage source 1
By changing the negative potential (-V _B ) of 4,
Ion energy can be adjusted.

In such a configuration of the present invention, the processing substrate 6 does not necessarily need to be located on the electrode 11; for example, the electrode 11 may be grounded, the processing substrate may be separated from the electrode 11 and brought into contact with the plasma, and a negative voltage (-V _B ) may be applied. may be applied.

According to the present invention, since the substrate to be plasma-treated is placed on an electrode connected to ground potential via a bias voltage source, the plasma potential Vs is extremely low.
As a result, the energy that causes ions in the plasma to reach _{the substrate can be adjusted over a wide range of (V B +} Vs) by varying V _B. becomes possible. By adjusting this ion energy,
In the etching process, unnecessary etching of the etching mask and the like can be prevented, and at the same time, the etching speed can be increased. Furthermore, etching processing with a small amount of undercut can be performed. On the other hand, in the deposition process, a deposition film with good step coverage can be formed, and a deposition film with few defects can also be formed.

[Brief explanation of drawings]

Figures 1 and 2 are configuration diagrams of conventional deposition equipment using plasma generated by high-frequency discharge, and Figure 3
Figure 4 is a configuration diagram of a conventional etching apparatus using plasma generated by high-frequency discharge, Figure 5 A, B,
C is a configuration diagram for explaining the operating principles of the configurations from FIGS. 1 to 4, which are classified into three types in order to explain them from the operating principles, and FIG. show. 1...Discharge tube, 2...Gas introduction hole, 3...High frequency oscillator, 4...Inductively coupled discharge coil, 5...
Vacuum container, 6... Processing substrate, 7... Holding plate, 8...
...Earth potential connection, 9...Generated plasma, 10...
... Capacitive coupling electrode (high frequency electrode), 11... Capacitive coupling electrode, 12... Plasma potential power supply, 13...
...Probe, 14... Board applied power supply.

Claims (1)

[Claims] 1. A plasma processing apparatus for depositing or etching a substrate using a chemical reaction of plasma, comprising: means for supplying high-frequency power to the vacuum chamber to generate plasma discharge in the gas within the vacuum chamber; an electrode provided for placing a substrate to be processed on a generated plasma section in a vacuum chamber; and an electrode provided for controlling energy when ions in the generated plasma section reach the substrate on the electrode. 1. A plasma processing apparatus comprising: a bias voltage source connected between the plasma processing apparatus and a ground potential source.