JPS6260875A - Plasma cvd apparatus - Google Patents

Abstract

PURPOSE:To equalize the amount of ions of gas converted into plasma and to form a high quality insulating film of a uniform thickness by concentrically arranging plural gas introducing holes pierced in the face of a lower electrode confronting a upper electrode so that the intervals are made gradually smaller from the central part toward the peripheral part. CONSTITUTION:An upper electrode 1 and a lower electrode 2 are used as parallel flat electrodes in a plasma CVD apparatus. Gas is introduced into the apparatus from the central part of the upper electrode 1 through plural gas introducing holes 3 pierced in the faces of the upper electrode 1 confronting the lower electrode 2. The gas introducing holes 3 are concentrically arranged so that the intervals (d) are made gradually smaller from the central part toward the peripheral part.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a plasma CVD apparatus, and particularly to an electrode structure of a parallel plate type plasma CVD apparatus.

(Prior Art) FIG. 4 is an explanatory diagram of electrodes in a conventional parallel plate plasma CVD apparatus, in which (a) is a cross-sectional view of the upper electrode, and (b) is the electrode opposite to the lower electrode (hereinafter referred to as the upper electrode). FIG. 3 is a plan view showing the distribution of gas introduction holes formed on the opposing surface. In the figure (a), 1 is an upper electrode, and gas introduction holes 3 are provided on the surface 2 facing the upper electrode, and as shown in the figure (b), there are provided at each intersection 5 of equally spaced virtual mesh lines 4. , the number is the same per unit area in the center and periphery of the upper electrode 1.

FIG. 5 shows the characteristics caused by the upper electrode 1 of FIG. 4, in which (a) is a schematic cross-sectional view in which the upper electrode 1 and the lower electrode 6 face each other with a facing interval of 7, and (b) is a schematic cross-sectional view of the upper electrode 1 and the lower electrode 6 with a facing interval of 7.
A diagram showing the electric field strength distribution (vertical @) in the diametric direction r (horizontal axis) from the center O of the electrode facing surface corresponding to the diagram (a), and (c) is a diagram showing the electric field intensity distribution (vertical @) formed on the facing surface of the lower electrode 6. The film thickness ratio (vertical axis) of the silicon nitride film (SiN)
(horizontal axis), and the film thickness ratio is standardized with the maximum film thickness of SiN as 1.

As can be seen from this figure (b), the electric field strength distribution at the facing interval 7 decreases significantly as it approaches the R edge of the electrode facing surface, and therefore the SiN film thickness also becomes thinner at the periphery of the electrode facing surface. .

(Problems to be Solved by the Invention) As mentioned above, the thickness of the deposited film of SiN etc. formed by the conventional plasma CVD apparatus has poor uniformity as seen in FIG. This has the drawback of deteriorating the manufacturing yield of semiconductor devices that require deposited films.

It is an object of the present invention to eliminate such drawbacks in the conventional parallel plate type plasma CVD apparatus.

(Means for Solving the Problems) In order to achieve the above object, the present invention changes the opening position of the gas introduction hole 3 in the upper electrode facing surface 2 from the center O of the upper electrode facing surface 2, for example. The gas introduction holes 3 are formed on the lower electrode facing surface 8 by continuously changing the distance r=Ae''+C and increasing the number of gas introduction holes 3 per unit area around the upper electrode 1. This ensures the uniformity of the film thickness of a semiconductor deposited film such as SiN.

(Function) According to the present invention, the uniformity of the film thickness of the semiconductor deposited film is improved;
Therefore, the yield in manufacturing semiconductor devices can be improved.

(Example) Hereinafter, the present invention will be explained in detail by way of an example using the drawings.

FIG. 1 is a cross-sectional view of an upper electrode 1 showing an embodiment of the present invention (
a) and a plan view (b) showing the surface facing the upper electrode.Hereinafter, a parallel plate plasma CVD apparatus having an upper electrode 1 and a lower electrode 6 with a radius of 20 (!11) will be described as an example.

In figure (b), the gas introduction hole 3 on the upper electrode facing surface 2 is located at a distance r from the center 0 of the upper electrode facing surface 2.
In the case of
＋.

Upper electrode facing surface 2 when B=1cm and C=-3■
FIG. Note that n is the center O of the upper electrode facing surface 2
The number of the gas introduction holes 3 calculated in the radial direction from , the distance d between the gas introduction holes 3 on one concentric circle is 4a++, and the diameter of the gas introduction holes 3 is 1 mm.

Figure 2 shows the number of gas introduction holes 3 (horizontal axis) obtained from the above formula.
A calculation diagram of the relationship between and the distance from the center 0 (vertical axis) is shown.

FIG. 3 shows a plasma CvD′jA according to an embodiment of the present invention.
Lower electrode facing surface 8 and (a) 1 The film thickness of the SiN film obtained by the apparatus of the present invention and the film thickness of SiN on the silicon wafer 9 formed by the conventional apparatus, normalized by the maximum film thickness of 1. In the figure (b), the film thickness ratio in the diametrical direction on the lower electrode facing surface 8 is shown. As can be seen from this figure (b), the deposited film obtained by the conventional plasma CVD apparatus becomes extremely thin around the lower electrode facing surface 8.

It shows a variation of about 60%.

On the other hand, the SiN deposited film according to the present invention has no variation of about 6%, which is more than 10 times smaller than the conventional one, even at the peripheral edge of the lower electrode facing surface 8. According to the present invention, the thickness of the deposited film is uniform. This shows that it is possible to achieve

The same result can be obtained even if the position of the gas introduction hole 3 is not made continuous as in the above embodiment, but is made smaller stepwise in the radial direction from the center of the upper 'fj:tflIi facing surface 2.

(Effects of the Invention) As is clear from the above detailed description, the present invention provides a plasma CVD method that can provide uniformity in the thickness of a deposited film.
This is because it is a device and can therefore be implemented in semiconductor manufacturing to improve yield.

There are many benefits to using it.

[Brief explanation of the drawing]

Fig. 1 is a cross-sectional view of the upper electrode and a plan view showing the gas introduction hole showing an embodiment of the present invention, Fig. 2 is a calculation diagram showing the position of the gas introduction hole, and Fig. 3 is an embodiment of the invention. 4 is a cross-sectional view of the upper electrode and a plan view showing the gas introduction hole in a conventional plasma CVD device, and FIG. 5 is a schematic diagram of the electrode in a conventional plasma CVD device. FIG. 2 is a diagram showing the electric field strength and the film thickness of the silicon nitride film. 1... Upper electrode, 2... Upper electrode opposing surface, 3
...Gas introduction hole, 6...Lower electrode, 7...
Electrode facing interval, 8...Lower electrode facing surface. Patent applicant Matsushita Electric Industrial Co., Ltd. Figure 1 (a) 3〃S introduction JL (b) Figure 2 a) (b) Strain direction of electrode j7 (C)

Claims (3)

[Claims] (1) In a plasma CVD apparatus having parallel plate electrodes, a plurality of gas introduction holes are arranged concentrically on the surface of the upper electrode facing the lower electrode through which gas is introduced from the center,
A plasma CVD apparatus characterized in that the arrangement interval becomes smaller from the center to the periphery. (2) Connect the nth (n is a positive integer) gas introduction hole from the center of the upper electrode toward the periphery at r=Ae from the center of the upper electrode.
The plasma CVD apparatus according to claim 1, wherein the plasma CVD apparatus is provided at a distance of ^-^(^1^/^B^n^)+C. However, A, B, and C are constants to be selected, respectively, and n is the number of gas introduction holes calculated in the radial direction from the center of the surface facing the upper electrode. (3) Claim (1) characterized in that a plurality of gas introduction holes are arranged concentrically around the center of the upper electrode, and the intervals on the same concentric circle are approximately constant.
Plasma CVD apparatus described in Section 2.