JPS59126778A - Method and device for plasma etching - Google Patents

Abstract

PURPOSE:To enable precision plasma etching with good efficiency and high uniformity by interposing an insulating flat plate having many fine holes between a lower electrode to be placed thereon with an object to be treated and an upper electrode disposed oppositely thereto. CONSTITUTION:An electronic part forming material having a resist pattern is placed on a lower electrode 4 and an insulating flat plate 5 consisting of a ceramic, etc. having many fine holes is interposed, via supports 8 and 8' between an upper electrode 3 and the electrode 4, then a high frequency voltage is impressed on the electrode 3 and the plasma etching of the above-mentioned material is performed, in a plasma etching device consisting of a bell-shaped cover part 1, a bottom plate 2 attached with the electrode 4 and disposed with the electrode 3 oppositely to the electrode 4. The active seed of the above-mentioned material arriving at the object to be treated is adequately suppressed by the above-mentioned constitution, whereby precision etching having high uniformity is obtd., the damage of the resist, etc. is prevented, hence treating electric power is increased and high speed etching is made possible.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improved plasma etching method and apparatus.

In recent years, gas plasma etching has become commonly used in the manufacture of semiconductor devices. The electrode structures used to perform this gas plasma etching include the cylindrical coaxial type, the cylindrical induction type, and the parallel plate type. In comparison, it is attracting particular attention because it has the advantage of less side etching and highly accurate etching that is faithful to ultra-fine patterns.

However, this parallel plate type electrode requires a low processing power output because (1) the etching speed is slow and productivity is low, and (2) the resist mask and sample to be processed are easily damaged by plasma ion bombardment. Must be held down (3
) Requires post-treatment to recover from damage caused by plasma ions after etching. (4) Silicon nitride (Si3N), which is important as an insulating gate film and protective film for semiconductor devices.
) When etching a film, there are practical problems such as the film thickness of the photoresist used as a mask is large and the selectivity for the silicon dioxide (si02) film, which is often used as a base, is low. .

In order to solve these problems, a device was developed in which an electrode plate made of a porous plate was inserted between parallel plate electrodes and connected to one electrode to act as an intermediate electrode (%
(Kaimei No. 56-76242).

This device makes the active species generated by plasma discharge uniform and highly dense, enabling highly uniform and precise etching, protects the sample from plasma ion bombardment, and increases the etching speed by 5 to 10 times compared to conventional etching. However, it has become clear that the following problems occur in a device using this intermediate N pole. That is, it has been found that when an aluminum porous plate is used as an intermediate electrode, a new problem arises in that aluminum is sputtered and contaminates the material to be etched, impairing its electrical properties.

In view of these circumstances, the present inventors have overcome the shortcomings of the conventional plasma etching method using parallel plate electrodes, improved the selectivity for silicon nitride, photoresist films, and silicon dioxide films, and improved the etching target material. As a result of intensive research into a plasma etching method using a parallel plate electrode type device that prevents contamination, the inventors have found that the objective can be achieved by interposing an insulating plate between the electrodes, and the present invention has been made. Ta.

That is, in plasma etching an electronic component forming material having a resist pattern, the present invention places the object to be processed on a lower electrode, arranges an upper electrode facing it, and places a gap between the two electrodes. A plasma etching method characterized by applying a high frequency voltage to an upper electrode through an insulating flat plate having a large number of pores, and an apparatus equipped with an insulating flat plate having a large number of pores suitable for carrying out the method. This is what we provide.

Next, the present invention will be explained in more detail with reference to the accompanying drawings.

FIG. 1 is a sectional view for explaining the main part of the structure of the device of the present invention, in which a flat upper electrode 3 and a lower electrode 4 are placed in a closed container consisting of a bell-shaped lid 1 and a bottom plate 2. are arranged in parallel, and an insulating flat plate 5 having porous holes is inserted between them. The upper electrode 3 is suspended by fitting and fixing its support column 6 into a hole 7 provided at the top of the bell-shaped lid 1, and the lower electrode 4 is fitted into the center of the bottom plate 2. Alternatively, it is constructed integrally with the bottom plate 2, and its upper surface also serves as a mounting table for an electronic component forming material to be processed having a resist pattern. The upper electrode 3 is connected to the support column 6
The lower electrode 4 is connected to a high frequency power source through the ground.

The insulating flat plate 5 having a large number of holes disposed between the upper electrode 3 and the lower electrode 4 is supported by a suitable support 88#, and the supporting means may be any known method. may also be used. For example, when the distance between the upper and lower electrode plates is 50TMl, the supporting position of the flat plate 5 is at least 30 mm below the upper electrode 3 and at least 10 mm above the lower electrode 4 on which the object to be processed is placed. It is particularly preferable that the electrode be disposed within a range of 15 to 20 gourds above the lower electrode 4. Further, the shape of the flat plate 5 is preferably a shape that is compatible with a normal plasma etching device.
For example, a disk-shaped one is suitable for the bell-shaped one shown in FIG.

However, the shape is not particularly limited as long as the purpose of the present invention is not hindered, and the size of the surface of the oxtail flat plate 5 is not particularly limited as long as the effects of the present invention are effectively achieved. However, it is preferable to select it so as to sufficiently cover the lower electrode 4 and the object to be processed placed on the upper surface thereof, that is, the electronic component forming material having the Rennost pattern.

This insulating multi-pored flat plate 5 used in the method and apparatus of the invention is made of an insulating material and has a large number of small through holes 9 throughout the plate. It is preferable to use a plate-shaped body in which pores are uniformly distributed throughout the plate. As the insulating material, for example, ceramics, glass, etc. are used, and ceramics are particularly preferred.

FIG. 2 is a plan view showing a preferred example of the flat plate 5 used in the present invention, and FIG. 3 is a plan view showing another example of the flat plate. In FIG. 2, a circular flat plate 5 has many pores 9 throughout the disk.・Although, as shown in FIG. 3, depending on the purpose, it may be advantageous to use a donut-shaped flat plate with a relatively large hole 9' formed in the center of the disk. can.

A large number of pores formed in an insulating flat plate can have any shape such as square, rectangle, circle, or triangle.
It is desirable to distribute it uniformly over the entire plate. In addition, the size of the pores is less than 10 mm, preferably 5 to 8 mm.
In the extreme range, 1 to 511i per Icd! It is appropriate to drill the holes at a ratio of approximately 1.

When performing plasma etching by applying a high frequency voltage to the upper electrode in an atmosphere of plasma gas using the apparatus of the present invention, it is necessary to perform plasma etching by applying a high frequency voltage to the upper electrode in an atmosphere of plasma gas. Plasma discharge is generated between the insulating flat plate, and the generated active species pass through the pores of the insulating flat plate, reach the workpiece placed on the upper surface of the lower electrode, for example a wafer, and effectively Etching is performed. When using the apparatus of the present invention, the object to be treated is not directly exposed to the plasma discharge region, and the intermediate plate is made of an insulating material. The active species that reach this amount are moderately suppressed and reduced, and the workpiece is etched with a moderate force. As a result, highly uniform and precise etching can be obtained, and furthermore, damage to resists and various objects to be processed due to plasma ion bombardment can be effectively prevented, thereby significantly improving selectivity to photoresists and substrates. Such an effect is not practical if a conductive material is used for the flat plate because the object to be processed will be contaminated. Furthermore, when plasma etching is performed using the apparatus of the present invention, the processing power output is increased to reduce the etching rate, and the adverse effects of plasma ion bombardment can also be suppressed, thereby improving productivity.

According to the present invention, it is possible to easily perform dry etching of silicon nitride films, which has been a problem in the past, and it is possible to conveniently overcome the deterioration of the characteristics of the processed material and other disadvantages caused by the use of an intermediate electrode. .

When the apparatus of the present invention is used as a cathode-coupled parallel plate apparatus, and the upper electrode is grounded and a high-frequency voltage is applied to the lower electrode on which the object to be processed is placed, the Since plasma is generated and acts between the flat plate having pores and the lower electrode, the resist and the object to be processed are directly bombarded with plasma ions and are damaged, making it impossible to expect an improvement in the selectivity of the i-underlayer. Therefore, in the device of the present invention, it is important to apply a high frequency voltage to the upper electrode.

In the above description, a parallel plate electrode type in which the upper and lower electrodes are placed horizontally has been described, but in the present invention, it is not particularly necessary to make them horizontal, and there is no problem even if they are placed vertically.

Next, the present invention will be explained in more detail with reference to Examples.

Example: An upper electrode with a diameter of 140tTan and a lower electrode with a diameter of 140mm that also serves as a workpiece mounting table! Single wafer automatic processing type plasma etching equipment OAPM arranged in parallel at 5om intervals
-301B (manufactured by Tokyo Ohka Kogyo Co., Ltd.), diameter 160+m
n, 2 holes in diameter and 1.5 holes in the ceramic plate of 2 brains.
A flat plate uniformly formed at a ratio of crl/crl was arranged parallel to the electrode plate at a position 30s+ below the upper electrode. 4
A workpiece on which a 1,000A silicon nitride film was formed on an inch silicon wafer was placed approximately in the center of the lower electrode surface, and carbon tetrafluoride gas containing 8% by weight of oxygen gas was used as the plasma processing gas. The degree of vacuum in the reaction chamber is 0.5TO.
rr, the silicon nitride film was plasma etched for 75 seconds with a high frequency oscillator output of 200 W. As a mask, a resist film of 0MR85 (trade name, manufactured by Tokyo Ohka Kogyo Co., Ltd.) with a thickness of 1 μm was used, and as a base layer, a resist film with a thickness of 1.00 μm was used.
Although an OA silicon dioxide layer was used, there was almost no reduction in the resist film, and uniform, high-precision etching processing was performed over the entire wafer surface.

The etching rate of the silicon nitride film was 800A for 7 minutes, and the etching rate of the underlying silicon dioxide layer was 300A.
A: In 7 minutes, the selectivity with respect to the silicon nitride film was 2.7.

For comparison, when an insulating flat plate with many pores was removed from the above apparatus and etching was performed under the same conditions as above, the etching time was only 67 seconds, which was sufficient, but the resist film was only 3.5 seconds. 000A decreased. The etching rates of the silicon nitride film and the photoresist film were 900X/min and 2,700A/min, respectively, and the selectivity was 0.
3, the etching rate of the underlayer was 600 A/min, and the selectivity with respect to silicon nitride was 1.5.

[Brief explanation of the drawing]

FIG. 1 is a side sectional view showing the main parts of the device of the present invention, FIG. 2 is a plan view showing one example of an insulating flat plate, and FIG. 3 is a plan view showing another example of an insulating flat plate. It is a diagram. In the figure, 1 is a bell-shaped lid, 2 is a bottom plate, 3 is an upper electrode, 4
5 is a lower electrode, and 5 is an insulating flat plate having many pores. Patent applicant: Tokyo Denshi Kagaku Co., Ltd. Agent Akira Agata Figure 1 Figure 2 Figure 3

Claims (1)

[Claims] ■ When performing plasma etch processing on an electronic component forming material having a resist pattern, the object to be processed is placed on the lower electrode, the upper electrode is placed opposite it, and the object is placed between the two electrodes. 1. A plasma etching method characterized by applying a high frequency voltage to an upper electrode with an insulating flat plate having a large number of pores interposed therebetween. 2. In a parallel plate plasma etching apparatus having an upper electrode for applying a high-frequency voltage and a lower electrode disposed opposite to the upper electrode and on which the object to be processed is placed, the space between the upper electrode and the lower electrode is 11 with many pores
! A plasma etching device characterized by having a 3R flat plate. 3. The device according to claim 2, wherein the insulating flat plate is a ceramic plate.