JPH023294B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a plasma processing apparatus, and more particularly to a gas etching apparatus using plasma discharge for use in manufacturing semiconductor devices, semiconductor integrated circuit devices, and the like.

Gas etching equipment that uses plasma discharge is also called dry etching equipment, and in recent years, in the manufacturing process of semiconductor devices such as _ICs , polycrystalline silicon films and oxidation It is widely used for fine patterning of silicon films, silicon nitride films, aluminum evaporated films, etc., and for removing photoresists using oxygen plasma. Such gas plasma etching has advantages over conventional solution etching, such as less chemical pollution, reduced number of etching steps such as being able to perform etching using a photoresist as a mask, and better etching accuracy.

By the way, there is one type of plasma etching apparatus having the structure shown in FIG. That is, a sealed etching chamber is constituted by the substrate 1 and the bell gear 2, and within the etching chamber there is a sample stage 5 which also serves as one electrode and which is arranged on the substrate 1 in a manner that maintains airtightness and is rotatable. The other electrode plate 8 is arranged on the bell gear 2 side facing the sample stage 5.

After placing the sample 4 to be etched on the sample stage 5 and evacuating the etching chamber through the exhaust pipe 7 provided on the side wall of the bell gear 2, the other bell gear 2 is placed inside the etching chamber. The reaction gas for etching is supplied to a predetermined pressure (lower than atmospheric pressure) through a gas supply pipe 6 provided on the side wall, and then to the side of the bell gear 2 facing the sample stage 5 which also serves as the electrode. By applying a high frequency voltage to the arranged electrode plate 8, plasma is generated and the film on the surface of the sample 4 is etched.

However, in such a plasma etching apparatus, not only the surface of the sample 4 to be etched placed on the sample stage 5 is etched, but also the back side of the sample 4 that is in contact with the sample stage 5 is etched under reduced pressure. Under such conditions, there is a phenomenon in which radical etching gas inevitably circulates and causes unnecessary etching.
The drawback was that it was not possible to etch only one side of the plate. Therefore, it is conceivable to cover the non-etched surface of sample 4 with a photoresist film or the like, but this has the problem of increasing the number of steps, and it has been desired to eliminate the above drawbacks by a simple sample arrangement structure.

An object of the present invention is to provide a novel plasma processing apparatus that solves the above-mentioned conventional drawbacks. That is, in the plasma processing apparatus according to the present invention, a gas outflow hole is provided in the center of the workpiece placement area on the upper surface of the sample stage, and a gas outflow hole is provided at the peripheral edge of the workpiece in communication with the gas outflow hole. A gap is formed between the side wall of the sample stand facing the sample stand, and the gas ejected from the gas outflow hole causes gas to flow from the lower surface of the object placed on the sample stand into the gap. A curtain is formed to protect the lower surface of the object from the etching gas, so that only the surface of the sample can be etched.

Embodiments of the present invention will be described in detail below with reference to the drawings.

FIG. 2 is a sectional view showing a sample stage according to an embodiment of the plasma processing apparatus according to the present invention.
1 is a disc-shaped base 12 whose upper surface is formed in a concave shape and a gas introduction hole 13 is bored in the center thereof, and a sample mounting plate 15 is placed on the top of the base 12 with a gap between the concave-shaped surface and the disc-shaped base 12. 14. The sample mounting plate 15 has an object to be processed 1 on the upper surface.
9. A recess 16, hereinafter referred to as a wafer, has a depth approximately equal to the thickness of the wafer and matches the size of the wafer, and a gas outlet is provided at the center of the recess 16, which communicates with the gas introduction hole 13 through the gap 14. A hole 17 is provided. In this case, it is convenient to prepare several types of mounting plates 15 having recesses 16 that match the wafer size.

In order to perform plasma etching only on the surface of a wafer using a plasma processing apparatus using a sample stage 11 configured as described above, a sample mounted on a base 12 placed opposite an electrode plate in an etching chamber (not shown) is used. A wafer 19 is placed in each recess 16 on the mounting plate 15 with the surface to be processed facing upward, and the etching chamber is evacuated to a vacuum of about 10 ^-6 Torr.

After the exhaust, the etching reaction gas is once supplied into the etching chamber so that the pressure is lower than atmospheric pressure. On the other hand, the gas introduction hole 1 of the sample stage 11
3, injecting an inert gas such as argon (Ar) or helium (He) at a gas pressure slightly higher than the gas pressure in the etching chamber,
The inert gas is ejected onto the back surface of each wafer 19, that is, the non-etched surface, at a flow rate of about 10 c.c./min, for example, from each gas outlet hole 17 of the sample mounting plate 15 through which the inert gas is communicated.

This ejected gas thus flows through the gap between the wafer 19 and the bottom surface of the recess 16, creating a gas curtain in the gap 18 between the peripheral edge of the wafer 19 and the side wall of the recess 16. At this time, the supply amount of the etching reaction gas is adjusted so that the entire gas pressure in the etching chamber is about 0.2 to 0.6 Torr.

In this state, a predetermined high frequency voltage is applied to the electrode plate facing the sample mounting plate 15, which also serves as an electrode, to generate plasma, and plasma etching is performed on the surface of each wafer 19 described above.

In this way, the gas curtain prevents the etching gas from entering the non-etched back surface of the wafer 19 to be processed as in the conventional method during plasma etching, making it possible to perform etching only on the desired surface of the wafer 19. Therefore, the flatness of the surface of the wafer 19 is ensured in the process of surface processing while holding the wafer 19 after etching with a vacuum chuck or the like, and the processing accuracy is improved.

It is important that the flow rate of the inert gas ejected from the gas outlet hole 17 is set to the minimum necessary flow rate to generate the gas curtain described above without inhibiting plasma etching on the surface of the wafer 19. When the gas pressure inside the etching chamber (chamber volume is approximately 100 mm) is 10 ^-1 ~
In the range of 10 ^-2 Torr, the inner surface of the recess 16 of the sample mounting plate 15 and the wafer 19 placed in the recess 16
The flow rate of the inert gas can be varied from several cc to several 10 c.c./cm depending on the size of the gap between the bottom surface and the peripheral edge of the inert gas and the size of the cavity 18.
It is necessary to control it to about min.

Note that FIGS. 3 and 4 show cross-sectional views of main parts of the sample mounting plate according to other embodiments of the plasma processing apparatus of the present invention. First, regarding the embodiment of FIG. Sample mounting plate 3 fitted to base 12
A gas reservoir groove 36 is provided along the peripheral edge of the wafer 19 on the surface of the wafer 19 mounting area on the surface of the wafer 19 , and the gas flows around the gas outlet hole 17 provided at the center of the gas reservoir groove 36 . It has a structure in which communication grooves 37 are arranged radially from the outflow hole 17,
Further, in the embodiment shown in FIG. 4, the surface of the wafer 19 mounting area on the sample mounting plate 45 is shaped like a mortar-shaped surface 46 with a very gentle slope as shown in the figure, with the gas flow hole 17 provided at the center thereof as the center. In the structure of the sample mounting plate 35 shown in FIG. 3 and the sample mounting plate 45 shown in FIG. The flow rate of the inert gas ejected from the gas outlet hole 17 is
By controlling the inert gas flow rate to be slightly increased, for example, 15 to 20 c.c./min, compared to the inert gas flow rate in the embodiment shown in FIG. The back surface and peripheral edge of the mounted wafer 19 and the gas reservoir groove 36 of the mounting plate 35
Alternatively, it is possible to create a gas curtain between the wafer mounting surface of the mounting plate 45 and the wafer mounting surface to prevent the etching reaction gas from going around without inhibiting plasma etching on the surface of the wafer 19. Therefore, the same object as the embodiment shown in FIG. 2 can be achieved with both of these embodiment structures. Furthermore, it goes without saying that this configuration can be modified in various ways without changing the gist of the present invention, and in this example, the sample stage was explained as a combination of both the base and the sample mounting plate, but it can be implemented as an integrated body. It may be configured.

As is clear from the above description, the plasma processing apparatus of the present invention can easily etch only the surface of the object to be processed, so it is extremely advantageous for use in manufacturing various semiconductor devices. The structure of the sample stage of the embodiment can also be applied to various plasma processing apparatuses.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram showing a conventional plasma processing apparatus, FIG. 2 is a cross-sectional view showing a sample stage according to an embodiment of the plasma processing apparatus according to the present invention, and FIGS. 3 and 4 are plasma processing apparatus according to the present invention. FIG. 7 is a sectional view of a main part showing a sample mounting plate according to another embodiment of the processing apparatus. In the figure, 11 is a sample stage, 12 is a base, 13 is a gas introduction hole, 14 is a gap, 15, 35, and 45 are sample mounting plates, 16 is a recess in the base, 17 is a gas outlet hole, and 18 is a gap. , 19 is an object to be treated, 36 is a gas reservoir groove, 37 is a communication groove, and 46 is a mortar-shaped surface.

Claims (1)

[Scope of Claims] 1. A closed etching chamber, an electrode 8 that generates etching gas plasma under reduced pressure in the etching chamber, and a sample on which a workpiece 19 is placed on the upper surface facing the electrode 8. In the plasma processing apparatus equipped with a table 11, a gas outlet hole 17 is provided in the center of the processing object 19 mounting area on the upper surface of the sample table 11, and the gas outlet hole 1
7, a gap 18 is formed at the peripheral edge of the object to be processed 19 and defined between the side wall of the sample stage facing the edge end surface, and the gas ejected from the gas outlet hole 17, A plasma characterized in that a gas curtain is formed in the gap 18 from the lower surface of the object 19 placed on the sample stage 11 to protect the lower surface of the object 19 from the etching gas. Processing equipment.