JPS63190162A - Plasma treatment device - Google Patents

Abstract

PURPOSE:To permit a good plasma treatment by connecting a bias voltage source between an electrode to be imposed with a substrate and grounding potential source and regulating the ion energy of a plasma part. CONSTITUTION:High-frequency electric power is supplied from a high-frequency oscillator 3 to capacity type coupling electrodes 10, 11 disposed to confront each other in a vacuum vessel 5. Plasma discharge 9 of gas in the vacuum vessel 5 is generated between the two electrodes 10 and 11 by said electric power. The substrate 6 imposed on the electrode 11 is subjected to a deposition or etching treatment by the ions of the plasma in the generated plasma part 9. The bias voltage source 14 is disposed between the electrode 11 and earth potential 8 of the above-mentioned plasma treatment device. The ion energy of the ions when the ions arrive at the substrate 6 is adjusted by changing the bias voltage. The satisfactory deposition or etching with decreased defects is thereby permitted.

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 deboxing or etching a semiconductor substrate using plasma.

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

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 discharge tube 1 through the 2 gas introduction holes. Reference numeral 5 denotes a vacuum chamber, which is evacuated by a vacuum evacuation system (not shown), and the substrate 6 to be deposited is held on a holding plate 7 and set to a ground potential of 8 K*.
l [has been done.

Now, high-frequency power is applied to the discharge tube l by the high-frequency oscillator 3 and the discharge coil I/4 coupled to it in a crocodile conduction type.
When r is applied, if the internal pressure of the discharge tube 1 is a suitable pressure of about 10, a non-polar discharge is generated in the discharge tube and a discharge plasma 9 is generated. Now, as a discharge gas, Shichinosilane (S
By introducing IH4) and nitrogen (N, ), and heating the substrate 6 to about 300 to 400C using a heating means (not shown), a silicon nitride (8faN4) film is deposited on the substrate.

FIG. 2 similarly 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 electrodes 11 serve as a holding plate for the substrate 6 and are connected to the ground potential 8. By introducing an appropriate pressure through the gas introduction hole 2 and generating discharge plasma 9, a desired substance can be deboxed onto 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. An electrode 10.11 capacitively coupled to the oscillator 3 is 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. For example, Freon gas (CF,
) and oxygen (08) gas are introduced at appropriate pressure to generate discharge plasma 9.
If fluorine ions are generated, the silicon substrate and silicon/oxide film will be etched by the fluorine ions.

FIG. 4 shows another example, similar to FIG. 3, but with two capacitively coupled electrodes 10, 11 introduced into the vacuum chamber 5. The substrate 6 to be processed is attached to and held by one electrode 10, and the Freon gas at an appropriate pressure introduced between the electrode 11 and the grounded electrode 10 rises and discharges to generate plasma 9.

Since the discharge is a high frequency discharge (several M to several tens of MHz) and one electrode is in contact with the plasma 9 at ground potential, ions with energy corresponding to the wave height of the applied high frequency arrive at the substrate 6. This causes general sputtering, but if the discharge gas is reactive, for example, energetic fluorine ions react with the substrate to cause reactive sputtering, 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 energy of ions reaching the substrate.

In FIG. 5, it is assumed that electrodes 10 and 11 are capacitively coupled to an oscillator 3, and one of the electrodes 11 is grounded to 8. 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), which is discharged by the applied high-frequency power to form plasma 9. shall be.

The 51st prisoner corresponds to the discharge type shown in Figure 3.

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, thermal energy, reaches the same floating potential substrate inserted in the vacuum container.

FIG. 5 (■) corresponds to FIGS. 2 and 4 in terms of the discharge format. In this case, since one electrode 11 is grounded at 8 and in contact with plasma 9, the electrical current of the plasma moves the sheath away from the ground potential and becomes a potential corresponding to the internal energy Vs of the plasma. Therefore, if you place the board on the ground side electrode 11 in Figure 5 (■), the debox 1
In both cases of etching and etching, ions arrive with ion energy Vs (usually less than a few volts) corresponding to the internal energy of this plasma.

On the other hand, the high frequency electrode of lO in Figure 5 (■) is connected to the oscillator 3, so the output voltage waveform of this oscillator is now
If expressed as nwt, the potential of this electrode 10 is Vo
Changes with sinwt. 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 IOK, but when averaged over time, the potential of 10 is equal to the ground potential. Therefore 10
Even if high frequency Vosinwt is applied to the plasma 9, the average potential of the plasma 9 remains at Vs. However, since the electrode 10 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, the potential of the electrode 10 is -V
When the temperature reaches o, 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 ions arrive at the energy of Vs, and when performing sputtering, the substrate is held by the electrode on the high frequency side. , (Vs+Vo).

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

As in the case of FIG. 5, 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. 5(5) is covered with an insulator so that it does not come into direct contact with plasma. Since the surface potential of this insulator also varies by Vosinwt, ions with the highest energy (Vo+Vs) arrive and sputter the insulator. This is the principle of high frequency sputtering for insulators. The configuration of FIG. 1 can be considered similar to the configuration of FIG. 5(C).

Considering the various deposition and etching equipment currently in use as described above, the energy of the deposition or etching ions that arrive at the substrate to be processed is determined entirely by the equipment conditions at that time, and is difficult to control. It can be seen that For example, in the deposition errors shown in FIGS. 1 and 2, the deposition energy is determined by the internal energy (3) 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 FIG. 3, the energy of etching ions is thermal energy, and in the configuration shown in FIG. 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 a deposition error, if it arrives at the substrate with thermal kinetic energy, it is not just a trap that attaches to the substrate. If the substrate is heated, it is possible to obtain kinetic energy from the substrate and move on the substrate, but in the case of deposition, the substrate temperature is desired to be as low as possible due to restrictions in device fabrication. When ions are given energy and are allowed to reach the substrate, most of the energy simply becomes thermal energy due to collision, but a portion (~several percent) becomes kinetic energy on the substrate and can move on the substrate.

Therefore, in the case of a general deposition system, the deposited film can form an adhesion-resistant film with good step coverage against steps and small holes on the substrate.

Furthermore, when the same material as the substrate is deposited, atoms arriving at the substrate can move to appropriate lattice points using this kinetic energy, so crystal growth can be performed at a considerably low temperature. The energy to be delivered is suitably in the range of several volts to several tens of volts, since if the value is too large, defects may be formed on the substrate due to collisions and sputtering may occur.

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 (such as Freon) as the discharge gas and causing reactive sputtering, ion energy of several hundred volts is not necessary, and local etching cannot be achieved at such a high voltage. The mask in this case is etched by sputtering, creating difficulties.

When performing reactive sputtering, in principle, the ion energy can be set to a value that promotes the chemical reaction, and that value is also a
v ~ dozens of tens of degrees is lllll desirable.

As seen in the above discussion, in a device that uses high-frequency discharge to generate plasma and performs deposition or etching, ions can be made to arrive on the substrate with controlled energy ranging from several volts to several tens of volts. If you can do it,
This process can bring great advances.

The present invention was made in order 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 achieving good step coverage. Alternatively, it is possible to perform a deposition process with fewer defects, or to enable an etching process in which etching due to unnecessary sputtering can be prevented. 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.
The vacuum tank 5, which is evacuated by a vacuum evacuation system (not shown), is provided with electrodes 10 and 11 that are capacitively coupled to the oscillator 3.

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 from a gas introduction plate (not shown), and discharge plasma 9 is generated by high frequency power from the oscillator 3. On the other hand, a negative potential (-Vi) is applied to the electrode 11 from the bias voltage source 14. As a result, ions having an energy of (VB+Vs) can be caused to reach the processing substrate 6 from the plasma 9. That is, by changing the negative potential (-VB) of the bias voltage source 14, the ion energy can be adjusted.

In such a structure 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 potential (-VB) may be applied. It 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 bias voltage 1 is applied, and as a result, by varying the energies V and VB that cause ions in the plasma to reach the substrate, it becomes possible to adjust the energy over a wide range (Vl+Vs). By adjusting this ion energy, unnecessary etching of the etching mask and the like can be prevented in the etching process.

Etching speed can be increased. Furthermore, etching processing with a small amount of undercut can be performed. on the other hand,
In the debossing process 9, it is possible to form a debossing film with good step coverage, and it is also possible to form a debossing film with few defects.

[Brief explanation of the drawing]

FIGS. 1 and 2 are block diagrams of a conventional deposition device using plasma generated by high-frequency discharge, and FIG. Figure 4 is a configuration diagram of a conventional etching apparatus using plasma generated by high-frequency discharge, and Figure 5 (AI @ (C) is the first
The configuration shown in Figure 4 works! ! ! , and FIG. 6 is a block diagram for explaining the operating principle classified into 311tK for explaining the principle, and FIG. 6 is a block diagram of the plasma processing apparatus of the present invention. DESCRIPTION OF SYMBOLS 1... Discharge tube, 2... Gas introduction hole, 3... High frequency oscillator, 4... Inductively coupled discharge coil, 5... Vacuum vessel, 6... Processed 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 source, 13. ...probe,
14... Board applied power supply. Figure 3 51 between 24 and 24

Claims (1)

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