JPH07312362A - Dry etching device - Google Patents

Abstract

PURPOSE:To enhance the surface uniformity of etching grate of a matter to be processed by a method wherein the charging of surface of a cramp-ring member is suppressed by plasma generated within a vacuum vessel. CONSTITUTION:In a conventional RIE device, a ring-like conductive plate 4 is provided so that it has a width so as to coat the upper surface of a cramp- ring member 8 upwardly and also so as to coat a part of outer and inner peripheral surfaces in addition to the upper surface of the cramp-ring member 8. The plate 4 is connected with a piston rod 91 being an earth potential via a cylinder 92, and ascended or descended together with the member 8. Thus, as a part exposed to plasma in the member 8 is coated with the conductive plate 4 connected with the earth potential, a surface part of the member 8 is suppressed to be charged with electricity by electrostatic shielding effects in the plate 4. Accordingly, the distortion of a plasma sheath is suppressed to consequently enhance surface uniformity of etching grate.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a dry etching apparatus for converting an etching gas into plasma by applying electric power and dry-etching an object to be processed such as a semiconductor device substrate under the plasma.

[0002]

2. Description of the Related Art A dry etching process in which an etching gas is turned into plasma by applying electric power and an object to be processed is etched under the plasma is used to manufacture various devices such as thin film transistors, LSIs, and solar cells using semiconductors. In this case, it is widely used for etching a metal film formed on a substrate while leaving a wiring pattern, an electrode pattern, etc., and for etching a semiconductor film formed on a substrate while leaving a predetermined pattern. .

The dry etching process is performed using a parallel plate type etching apparatus used for reactive ion etching (RIE) shown in FIG. 2, for example. This etching apparatus is provided with a vacuum container 1, in which an electrode 2 also serving as a substrate holder for mounting a substrate S2 on which a film to be etched is placed and an electrode 3 arranged to face the electrode 2 are provided.

The electrode 2 is used as a power application electrode for applying high frequency power or direct current power to the etching gas introduced between the electrode 2 and the electrode 3 to turn it into plasma. In the illustrated example, a matching box 21 is used. High frequency power supply 22
It is connected to the. The electrode 3 is a ground electrode, and the porous electrode plate 32 is provided at the opening of the gas nozzle 31 which constitutes a part of the electrode.
The electrode plate 32 is provided with a large number of gas supply holes having a diameter of about 0.5 mm so that the gas supplied from the gas nozzle 31 is entirely discharged between the electrodes through the holes. Has become.

The vacuum container 1 also has a ring-shaped clamp ring member 8 for pressing and fixing the peripheral portion of the substrate S2 placed on the electrode 2 to the electrode 2 in order to hold the substrate S2 on the electrode 2. And a drive device 9 for selectively moving the clamp ring member 8 to a fixed position of the base body S2 or a position that does not hinder loading and unloading of the base body S2. The device 9 in this example comprises a piston cylinder device. Normally, one piston cylinder device 9 is provided, the piston rod 91 is connected to a part of the clamp ring member 8, and the cylinder 92 is fixed to the vacuum container 1.

The vacuum container 1 is further connected to an exhaust device 7 which is connected to an exhaust pump via an opening / closing valve, and a gas supply portion 6 is connected to the gas nozzle 31 by piping. The gas supply section 6 supplies a required amount of etching gas through one or more mass flow controllers 611, 612 ... And open / close valves 621, 622. ··It is included.

According to this etching apparatus, the substrate S2 to be etched is placed on the high-frequency electrode 2 in the container 1 in a state in which the clamp ring member 8 is raised and retracted from the electrode 2 by the piston cylinder device 9, and thereafter, The clamp ring member 8 is lowered by the piston cylinder device 9, and the peripheral edge of the base body S2 is pressed and fixed to the electrode 2. Then, the etching gas is introduced from the gas supply unit 6 through the gas supply holes of the nozzle 31 and the electrode plate 32,
The inside of the container 1 is set to a predetermined etching vacuum degree by operating the exhaust device 7. Further, a high-frequency voltage is applied to the electrode 2 from a high-frequency power source 22, the gas introduced thereby is turned into plasma, and the film on the substrate S2 is etched under this plasma. The electrode 2 is provided with a water cooling device 2 as needed.
The temperature may be controlled by a temperature control device such as 0.

In the dry etching apparatus having the structure in which the substrate is fixed to the substrate holder by the clamp mechanism as described above, the driving device 9 portion of the clamp ring member 8 is generally attached to a vacuum container having a ground potential. However, since high-frequency power and DC power are applied to the electrode 2 which also serves as the substrate holder, the electrode 2 and the clamp ring member 8 need to be insulated from each other. Therefore, when the material of the clamp ring member 8 is formed of an electrically insulating material such as ceramics such as alumina or resin, or when the material of the clamp ring member 8 is a conductive material such as a metal, the electrode 2 and the clamp ring member are formed. The clamp ring member 8 is placed in an electrically floating state by interposing an insulator between the drive ring 9 and the drive device 9 and the clamp ring member 8.

[0009]

However, as described above, the clamp ring member 8 is made of an electrically insulating material.
Alternatively, when it is electrically floated, as illustrated in FIG. 3, the surface portion of the clamp ring member 8 facing the plasma P is charged by the action of ions and electrons in the generated plasma P. This surface charge distorts the plasma sheath PS, resulting in in-plane nonuniformity of the etching rate. That is, in the example of FIG. 3, the distance from the substrate S2 (a plate body in the illustrated example) to the plasma sheath PS increases toward the peripheral portion of the substrate, and the etching rate becomes slower in the peripheral portion than in the central portion of the substrate. Such a phenomenon is remarkable when the etching vacuum degree is a low pressure of 50 mTorr or less, and a silicon oxide (SiO ₂ ) film or an ITO (Indi
um Tin Oxide) becomes a problem when etching the film.

Therefore, the present invention is a dry etching apparatus having a clamp ring member for pressing and fixing an object to be processed on an electrode which also serves as a holder thereof, and charges the surface of the clamp ring member by plasma generated in a vacuum container. An object of the present invention is to provide a dry etching apparatus that can suppress the etching rate and improve the in-plane uniformity of the etching rate of the object to be processed.

[0011]

In order to solve the above-mentioned problems, the present inventor has conducted extensive research, and the shape of the plasma sheath is strongly affected by the electric potential of the opposing surfaces. It has been found that it is sufficient to suppress the charging of the surface portion of the clamp ring member due to the plasma.

Based on the above findings, the dry etching apparatus of the present invention is a dry etching apparatus in which an etching gas is turned into plasma by applying electric power and the object to be processed is etched under the plasma. A clamp ring member, which is made of an electrically insulating material or is electrically floated, for pressing and fixing to the double-purpose holder, and a position where the clamp ring member is fixed to the object to be processed or does not hinder loading and unloading of the object to be processed. It is characterized in that it is provided with a clamp ring member driving means for moving to and a shield means for covering the surface of the clamp ring member facing the plasma and having its own surface potential fixed.

Examples of the electrically insulating material used as the material of the clamp ring member include ceramics such as alumina, resin, and quartz glass. When the main body material of the clamp ring member is a conductor or the like, a spacer made of the insulating material is provided between the clamp ring member main body and the object to be processed and the holder, and between the clamp ring member main body and the clamp ring member driving means. It is conceivable that the clamp ring member is electrically floated by being interposed therebetween.

The shielding means may be one that is covered with a shield made of a conductor that is connected to a fixed potential, or one that connects the conductive film coated on the surface of the clamp ring member to a fixed potential. Conceivable. Although it is considered that the shielding means is typically directly connected to a ground potential which is a fixed potential, it may be grounded via another resistor, or grounded via a DC power source and a capacitor connected in parallel. At this time, the distortion of the plasma sheath can be suppressed while controlling it more precisely.

[0015]

According to the dry etching apparatus of the present invention, by providing the shielding means for suppressing the charging of the clamp ring member made of an electrically insulating material or electrically floated, the ions in the generated plasma Under the action of electrons and electrons, the surface portion of the clamp ring member facing the plasma is suppressed from being charged by the plasma. As a result, the distortion of the plasma sheath, which occurs when the surface portion is charged as in the conventional case, is suppressed, and the in-plane uniformity of the etching rate is improved.

[0016]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows a dry etching apparatus used for RIE (reactive ion etching) which is an embodiment of the present invention. This device has a width that covers the upper surface of the clamp ring member 8 above the clamp ring member 8 in the conventional RIE device shown in FIG. 2, and in addition to the upper surface of the clamp ring member 8, a part of the outer peripheral surface and the inner peripheral surface. A ring-shaped conductive plate 4 having a U-shaped cross section is installed so as to cover it. The plate 4 is connected to and supported by the piston rod 92, which is at ground potential, via the cylinder 92, and moves up and down together with the clamp ring member 8. That is, the plate 4 is grounded and has a fixed potential. Other configurations are the same as those of the conventional apparatus shown in FIG. 2, and the etching operation is also the same. The same parts are designated by the same reference numerals.

According to this etching apparatus, the portion of the clamp ring member 8 facing the plasma is covered with the conductive plate 4 connected to the ground potential.
Due to the electrostatic shielding effect due to, the surface portion of the clamp ring member 8 is suppressed from being charged, distortion of the plasma sheath is suppressed, and as a result, the in-plane uniformity of the etching rate is improved.

Although the plate 4 is directly grounded here, it may be grounded via a resistor or a DC power supply. Instead of the plate 4, the surface of the clamp ring member 8 may be replaced. It may be covered with a conductive film and the film may be grounded or the like. Next, a specific example of reactive dry etching using the RIE apparatus shown in FIG. 1 will be described.

Aluminum was used as the material of the plate 4. First, an ITO film having a thickness of 0.12 μm is formed on the surface, and the substrate S1 on which an etching pattern is drawn with a resist is loaded into the container 1 and placed on the electrode 2, and then the clamp ring member 8 is placed. The peripheral edge of the substrate S1 was pressed and fixed to the electrode 2 by. After that, 20mTorr in the container 1
The degree of vacuum is r, and methane (CH ₄ ) gas and hydrogen (H ₂ ) gas are contained in the container 1 at 25 sccm and 60 sccm, respectively.
At the same time as the flow rate of 1
A high frequency power of 3.56 MHz is applied with an electric power of 200 W to turn the gas into a plasma, and the substrate S1 is heated under the plasma.
The upper ITO film was etched.

When the same etching was repeated by changing the substrate S1, the in-plane uniformity of the etching rate was ± 4%.
Met. On the other hand, when the RIE apparatus shown in FIG. 2 that does not employ the plate 4 is used as a comparative example, and the same substrate S1 is used under the other conditions and etching is repeated under the other conditions, in-plane uniformity of etching rate Is ± 1
It was 4%.

The present invention is applicable not only to the RIE device but also to the E device.
It can also be applied to CR and magnetron etching equipment.

[0022]

As described above, according to the present invention, there is provided a dry etching apparatus having a clamp ring member for pressing and fixing an object to be processed on an electrode which also serves as a holder for the dry etching apparatus. It is possible to obtain a dry etching apparatus that can suppress the charging of the surface of the clamp ring member, improve the in-plane uniformity of the etching rate of the object to be processed, and consequently improve the yield.

[Brief description of drawings]

FIG. 1 is a diagram showing a schematic configuration of a reactive ion etching (RIE) apparatus that is an embodiment of the present invention.

FIG. 2 is a diagram showing a schematic configuration of an example of a conventional dry etching apparatus.

FIG. 3 is a diagram illustrating distortion of a plasma sheath due to charging of a clamp ring member in a conventional device.

[Explanation of symbols]

 1 Vacuum container 2 Base holder / high frequency electrode 20 Water cooling device 21 Matching box 22 High frequency power supply 3 Ground electrode 31 Gas nozzle 32 Porous electrode plate 4 Plate 6 Etching gas supply part 7 Exhaust device 8 Clamp ring member 9 Piston cylinder device 91 Piston rod 92 Cylinder S1, S2 Base

Claims (1)

[Claims] 1. An electric device for pressing and fixing an object to be processed to a holder which also serves as an electric power application electrode in a dry etching apparatus for converting an etching gas into plasma by applying electric power and etching the object to be processed under the plasma. A clamp ring member made of an insulating material or electrically floated, and a clamp ring member driving means for moving the clamp ring member to a position where the object to be processed is fixed or a position where loading and unloading of the object is not hindered. A dry etching apparatus, comprising: a shielding unit that covers a surface of the clamp ring member facing the plasma and has a fixed surface potential.