JPS60206027A - Plasma processing apparatus - Google Patents

Abstract

PURPOSE:To uniform processings within a sample by surrounding the external circumference of surface of sample to be processed with inactive gas on the occasion of processing a sample by etching after the reaction gas is changed to gas plasma under a reduced pressure ambient. CONSTITUTION:An upper electrode 20 and a lower electrode 30 opposed to each other are provided within a vacuum case 11 and a wafer 60 to be etched is placed on the lower electrode 30. A plasma processing apparatus is thus formed, reaction gas supplied from a reaction gas bomb 21 is injected from many gas supply holes 24 provided at the lower surface of upper electrode 20 through a flow rate control device 22 and a gas flow path 23, and plasma is thereby generated between the electrodes 20 and 30 in order to etch the wafer 60. With such a structure, an inactive gas bomb 25 is newly provided and the inactive gas supplied therefrom is injected from the external circumference of wafer 60 through the gas flow rate control device 26 and gas flow path 26 extending through the support axis of electrode 30. Thereby, the wafer 60 is surrounded by inactive gas and the gas is then exhausted from an exhaustion nozzle 10 at the bottom of case 11 through the gap 41.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to a plasma processing apparatus, and particularly to a plasma processing apparatus suitable for etching a sample with plasma under reduced pressure.

[Background of the Invention] Dry etching equipment is one type of plasma processing equipment that applies a high-frequency voltage to a reactive gas and performs a predetermined process on a sample while discharging it under reduced pressure. . In this apparatus, it is important to perform uniform etching of the wafer in order to improve production efficiency.

Although various factors affect uniform processing of wafers, gas flow and uniformity of concentration are also important factors. Hereinafter, a conventional dry etching apparatus will be explained using FIG. 1 as an example.

In FIG. 1, a vacuum vessel 11 has two electrodes 20 and 30 facing each other in parallel, a reaction gas 21 is introduced from the lower surface of the upper electrode 20, and a high-frequency voltage is applied to the lower electrode 30 (generally speaking, ) is configured such that the wafer is placed on the top surface. Gas 21 introduced from the upper electrode 20 flows radially over the lower electrode 30 and
The air is exhausted through the gap 41 between the outer peripheral side surface of the vacuum container 11 and the side wall of the vacuum container 11 .

Figure 2 shows how M
This figure shows the results when etching the film. As is clear from FIG. 2, the etching rate tends to be low at the center of the surface to be processed of the wafer, and the etching rate tends to be high at the outer periphery of the surface to be processed of the wafer. This is because the radical concentration of the reaction gas changes as shown in Figure 3, depending on whether or not the object to be etched exists under the reaction gas, depending on the outer periphery of the surface of the wafer to be processed. At the outer periphery of the surface, chemical reactions become active due to gas diffusion and etching progresses, and this is considered to be one of the reasons for the non-uniform etching rate as shown in FIG.

The disadvantage of such dry etching equipment is that the etching speed within the wafer is non-uniform, so that when etching is completed at the center of the wafer's surface to be processed, the outer periphery of the wafer's surface to be processed is over-etched, causing the pattern to become over-etched. The problem is that the dimensional accuracy of the product decreases, resulting in a decrease in product yield. Note that this type of device is, for example,
JP-A-55-82438, JP-A-56-4372
No. 5, JP-A-56-100419, JP-A-Sho 5
It is disclosed in JP 7-114231 and the like.

[Purpose of the invention]

An object of the present invention is to provide a plasma processing apparatus that can uniformly process a sample and improve product yield by locally controlling the concentration of a reactive gas supplied onto the surface of the sample to be processed. [Summary of the Invention] The present invention is characterized in that an inert gas supply system is provided to be able to supply an inert gas to the outer periphery of the processed surface of the sample during processing. [Embodiment of the Invention] An embodiment of the present invention is explained with reference to Figs. 4 and 5. do. In FIG. 4, the same parts as in FIG. 1 are indicated by the same symbols.

In FIG. 4, after the installation of the wafer 60 as a sample on the lower electrode 30 and the evacuation of the inside of the Makabe container 11 to a predetermined pressure are completed in the same manner as in the past, the reaction gas supply cylinder 21 is
The flow rate of the reaction gas is controlled by the flow rate control device 22, passes through the gas flow path 23, and is supplied from the gas supply hole 24.

On the other hand, the flow rate of the inert gas is controlled by the flow rate control device 26 from the gas supply pump 25 constituting the inert gas supply system, and the flow rate of the inert gas is also controlled by the flow rate control device 26, and the lower electrode 3
The gas is also supplied from the gas supply hole 28 located on the outer periphery of the wafer 0. The reactant gas supplied in this way is transferred to the upper electrode 20.
Plasma is generated by discharge between the wafer 60 and the lower electrode 30, and the surface of the wafer 60 to be processed is etched into a predetermined pattern.

Thereafter, this gas passes through the gap 41, passes through the exhaust nozzle 10, and is exhausted by an exhaust device (not shown). Note that the pressure inside the vacuum container 11 is adjusted to an optimal pressure by an exhaust device.

In the plasma processing apparatus as in this embodiment, the flow rates of the reactive gas and the inert gas can be controlled and supplied, so that the following effects can be achieved.

That is, in the case where the etching rate distribution is non-uniform as shown in FIG. The radical concentration of the reactive gas near the outer periphery of the processing surface of the wafer 60 is diluted to suppress chemical reactions at the outer periphery of the processing surface of the wafer 60, thereby suppressing etching. Therefore, the uniformity of the etching rate within the wafer 60 can be improved compared to the conventional method by appropriately balancing the supply amounts of the reactive gas and the inert scum. FIG. 6 explains another embodiment, in which a gas is used to efficiently guide the inert gas supplied from the inert gas supply port 28 provided in the lower electrode 30 to the outer periphery of the surface to be processed of the wafer 60. Guidance plate 70
(insulator) is provided. When such a gas guide plate is provided, the inert gas is mainly supplied to the outer circumference of the processed surface of the wafer along the guide plate, thereby suppressing etching at the outer circumference of the processed surface of the wafer. will further improve.

[Effects of the Invention] As explained above, the present invention provides an inert gas supply system capable of supplying an inert gas to the outer periphery of the surface to be processed of the sample during processing. By controlling the reaction gas concentration appropriately, the uniformity of processing within the sample can be improved, and the yield of products can be improved.

[Brief explanation of drawings]

Figures 1, 2, and 3 explain conventional dry etching equipment. Figure 1 is a vertical cross-sectional view of the dry etching equipment, Figure 2 is an etching rate distribution diagram, and Figure 3 is a radical FIG. 4 is a vertical cross-sectional view showing an embodiment of the plasma processing apparatus according to the present invention, FIG. 5 is an etching rate distribution diagram using the plasma processing apparatus shown in FIG. 4, and FIG. 6 is a diagram showing the plasma processing according to the present invention. FIG. 7 is an enlarged vertical cross-sectional view of the vicinity of the lower electrode showing another embodiment of the device. 10...Exhaust nozzle 11...Vacuum container 20...
Upper electrode 21...Reactive gas supply cylinder 22...Flow rate control device 23...Gas flow path 24...Gas supply port 25...Inert gas supply cylinder 26...Flow rate control device 27...・Gas flow passage 28・
...Gas supply port 30...Lower electrode 41...Gap 50...High frequency power supply 60...Wafer 70...
Gas induction board 2 figures, 3 figures glaze, &1 electric tower 1

Claims (1)

[Claims] 1. An apparatus for converting a reactive gas into plasma under reduced pressure and treating a sample with the plasma, characterized in that an inert gas supply system is provided to supply an inert gas to the outer periphery of the surface to be processed of the sample during processing. plasma processing equipment.