JPH01173711A - Thin film forming device - Google Patents

Abstract

PURPOSE:To effectively prevent the electric discharge generating between RF electrodes and a circumferential member and the use of an earth shield is unnecessitated by a method wherein the RF electrodes are formed by a thin plate, and the RF electrodes are junctioned pinching an insulating spacer. CONSTITUTION:A high frequency introducing bar 15, to be connected to the external RF power source 3, is introduced into the inside passing through a chamber 1 airtightly, and a thin plate type RF electrodes 2a and 2b are fixed to the electrically insulated mounting surfaces 15a and 15b located at the lower end of the chamber 1 using fixings. In the above-mentioned state, both of the RF electrodes 2a and 2b are closely fixed by an insulating spacer 9 through the intermediary of a microscopic space S. On the outer circumference 1a of the chamber 1 where the bar 15 penetrates, the bar 15 is tightened and fixed by a holder 18 through the intermediaries of insulating materials 16a and 16b and an air gap 17. An earth shield 19, with which the electric discharge generating between the bar 15 and the inner wall of the chamber 1 will be prevented, is provided on the inner surface 1b of the chamber 1. However, as almost no electric discharge is generated, the side earth shield can be abolished entirely.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention provides plasma CVD with an improved RF main electrode structure;
This invention relates to a plasma-applied thin film forming apparatus for cleaning, etching, etc.

[Prior art] Plasma is generated by discharging between an RF main electrode to which high-frequency power is applied and a ground electrode held at earth potential.
In plasma-applied thin film forming equipment used for film formation, etc.,
In order to prevent discharge from occurring around the RF main electrode and the inner wall of the chamber, a shielding plate called an earth shield is generally provided around the RF main electrode.

This earth shield will be specifically explained using a parallel plate type plasma CVD apparatus shown in FIG. 3 as an example.

In the figure, an RF electrode 2 connected to an external high-frequency power source 3 and a substrate 4 set in a holder (ground electrode) 5 held at earth potential are arranged in parallel in a vacuum chamber 1, and in a space facing them. Generate plasma P and connect RF electrode 2
The gas introduced from inside the substrate is decomposed and attached to the substrate surface. Here, R to which high frequency power is applied
Since the F electrode 2 will discharge even the inner wall of the chamber which is at ground potential if left as it is, an earth shield 6 which is held at ground potential is placed around the RF main electrode except for the surface facing the substrate with a predetermined gap. This prevents power loss and dust from adhering to the inner walls of the chamber.

[Problems to be Solved by the Invention] However, when an RF main electrode earth shield is provided around the RF main electrode, the following problems are pointed out.

■ The gap dimension C between the RF electrode 2 and the earth shield 6 is
It is desirable to adjust this to 1 mm or less, but on the other hand,
This gap forms a capacitor with low resistance to high frequencies, and the applied high-frequency power can easily escape.

(2) When high power is applied, the discharge intensity becomes strong around the RF electrode 2 in the vicinity of the earth shield 6, which adversely affects film formation.

■ Discharge products may accumulate in the gap between the electrode earth shields 2.6 and may change the discharge.

■ In order to maintain the gap between the electrode and the earth shield 2.6 at a set value of about 1 mm, special measures must be taken in the design of the earth shield 6 to take into account thermal deformation, and the manufacturing cost is also high.

Therefore, in consideration of the above-mentioned problems, a thin film forming apparatus that does not require the conventionally conventional earth shield is considered to be advantageous.

By the way, as a thin film forming apparatus that has the possibility of eliminating the need for an earth shield, there is a so-called two-plane plasma generation system as shown in FIG. That is, in this device, a pair of front and back RF electrodes 2a and 2b for applying high-frequency power are installed in a vacuum chamber 1, and a substrate 4.4 is placed on both sides of the electrodes to face each RF main electrode a or 2b. Plasma Pa and Pb are generated between the substrate 4 and the two surfaces of the substrate can be processed such as film formation at the same time.

The biggest feature of this device is that it has a single high frequency power source 3 and a matching box 7, and has an RF electrode 2a.

It is possible to supply the high frequency power necessary for 2b.

The problems when adopting this type of method are as follows:
RF electrode 2a directly connected to the generation conditions of plasma Pa and Pb
, 2b is difficult to balance, as already disclosed by the present inventors in JP-A-61-8914 etc., fixed or variable capacitors 8a, 8b are connected to the branch circuit from the matching box 7. Improvements have been made to easily overcome this problem by providing RFq node means such as the following.

However, in this type of thin film forming apparatus, since the RF electrodes 2a and 2b are joined on the back side via the insulating spacer 9 as shown in the figure, it is not necessary to provide an earth shield at least on the back side. It becomes unnecessary. However, each of the RF main electrodes a and 2b is formed of a thick hollow box body that includes a gas introduction chamber G for introducing gas into the chamber 1 from the surface as shown by the arrow in the figure. When they are joined back to back, both RF
The width dimension B of the electrodes 2a and 2b ends up being at least several tens of mm. Therefore, it is now necessary to prevent electrical discharge between the circumferential surfaces of the RF electrodes 2a and 2b and the chamber inner wall 1, etc., and for this purpose, a side earth shield 6a is installed to cover the circumferential surfaces of the RF electrodes 2a and 2b. The current situation is that

Based on the above-mentioned technical background, the present invention provides an improved electrode structure that can completely eliminate the earth shield including the side earth shield, especially in relation to the two-sided plasma generation method. The present invention provides a thin film forming apparatus.

[Means for Solving the Problems] In the present invention, substrates are placed on both sides of a pair of RF main electrodes to which high-frequency power is applied, and plasma is generated between the RF main electrodes and the opposing substrates to cover the two surfaces of the substrates. Regarding the thin film forming device that simultaneously forms thin films, each RF main electrode is formed on a thin plate with a thin wall thickness,
These RF main electrodes are joined with insulating spacers interposed therebetween.

[Operation] With such an electrode structure, the width of the pair of RF main electrodes sandwiching the insulating spacer can be reduced to a few millimeters, and the electrical discharge between the electrode circumferential side and the chamber etc. can be ignored. It can be reduced. Therefore, it is possible to substantially eliminate the ground shields from the RF main electrode including the side ground shields.

[Example 1] An example shown in FIGS. 1 and 2 will be described below.

FIG. 1 shows an outline of a vertical two-sided plasma CVD apparatus according to the present invention, and the symbols of each part are those of the conventional example (FIGS. 3 and 4).
(Figure) is commonly used. That is, 1 is a vacuum chamber, 2
A, 2b are a pair of front and back RF main electrodes 3 that are electrically insulated with an insulating spacer 9 sandwiched between their outer peripheries and are joined back to back.
The RF main power source 4 that applies high frequency power to the F electrodes 2a12b via the matching box 7 is shown as a substrate set in a holder 5 and placed facing the RF electrodes 2a and 2b.

A branch circuit 1 applies high frequency power from the RF power source 3 to the RF electrodes 2a and 2b via the matching box 7.
Barrier pull capacitors 8b and 8b are provided at 0a and 10b, and the RF power is adjusted with these to connect the RF electrodes 2a and 2b.
The plasmas Pa and Pb generated between the substrate 4.4 and the substrate 4.4 are homogenized, and the film forming conditions such as the speed on the two surfaces of the substrates where films are formed simultaneously are made the same. Note that 11 indicates an exhaust port of the chamber 1, and 12 indicates a gas introduction port for introducing a film-forming raw material gas between the electrode and the substrate. Further, 13 indicates a heater set on the back side of the substrate holder 5.

Therefore, in the vertical two-sided plasma CVD apparatus as described above, the pair of RF main electrodes a and 2b are formed of a thin plate member such as a single stainless steel plate, and both RF electrodes 2a and 2b are placed on the back side. They are joined together with an insulating spacer 9 sandwiched between their outer peripheries.

Specific mounting structure of RF electrodes 2a and 2b and chamber 1
Details of the RF power introduction mechanism are shown in FIG. That is, a high frequency introduction bar 15 connected to an external RF main power source is hermetically penetrated through the chamber 1 and introduced into the interior, and the electrically insulated mounting surfaces 15a and 15b at the lower end thereof are
The thin plate-shaped RF electrodes 2a and 2b are fixed using fixtures (not shown). In this installed state, both RF electrodes 2
a- and 2b are closely attached to each other through a minute gap S formed by an insulating spacer 9. A holder 18 is fastened to the outer surface 1a of the chamber 1 through which the high-frequency introduction bar 15 passes through, through insulating materials 16a and 16b and an air gap 17, in order to fix the bar 15. Further, an introduction part earth shield 19 is attached to the inner surface 1b of the chamber 1 to prevent electric discharge between the high frequency introduction bar 15 and the inner wall of the chamber.

Now, with the improved electrode structure as described above,
Since the paired RF electrodes 2a12b are formed into thin thin plates, the overall width A when they are joined with a narrow insulating material 9 in between can be reduced to the order of several mm+. can.

With such a narrow exposure dimension, almost no discharge occurs between the electrode circumferential surfaces a and b and the opposing inner wall of the chamber, and even if discharge occurs, it will be negligible. Therefore, in this apparatus, the side earth shield which was previously necessary is also substantially unnecessary, and the intended plasma CVD apparatus which completely eliminates the earth shield around the electrode can be realized.

Although the embodiment shows a method in which the gas inlet 12 is opened into the chamber 1, a method in which the gas flows out from inside the RF electrodes 2a and 2b may also be adopted. In this case, the RF electrodes 2a and 2b do not need to be changed except that the gas holes are opened, and the gas is guided into the gap S between them and allowed to flow out.

Furthermore, although the embodiments have been exemplified in the case of a plasma CVD apparatus, the present invention is similarly applicable to plasma cleaning apparatuses and etching apparatuses that utilize a two-sided plasma generation system.

[Effects of the Invention] As described above, the thin film forming apparatus of the present invention having an electrode structure in which a thin plate RF main electrode is bonded effectively prevents electrical discharge with surrounding members of the RF main electrode, while preventing the earth shield from having various disadvantages. can make the use of .

[Brief explanation of the drawing]

FIG. 1 is a schematic sectional view of an apparatus showing an embodiment of the present invention, and FIG. 2 is a broken sectional view of the main parts thereof. FIGS. 3 and 4 are schematic cross-sectional views showing examples of conventional devices using an earth shield, respectively. 1...Chamber 2a, 2b...RF electrode 3...
・RF main power supply 4... Board 5... Holder
6.6a...Earth shield 7...Matching box 8a, 8b...Capacitor

Claims (1)

[Claims] In an apparatus in which a substrate is placed on both sides of a pair of RF electrodes to which high-frequency power is applied, plasma is generated between the RF electrode and the opposing substrate to simultaneously form a thin film on two surfaces of the substrate, the RF electrode is formed into a thin plate. A thin film forming apparatus characterized in that these RF electrodes are joined with an insulating spacer interposed therebetween.