JPH0519299B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an etching apparatus for forming a pattern on a semiconductor substrate by dry etching.

(Prior Art and its Problems) Conventionally, a wet etching method has been adopted for manufacturing semiconductor circuits and the like. However, wet etching has many drawbacks such as the occurrence of side etching, and as the degree of integration increases and it becomes necessary to form finer circuit patterns, dry etching methods that do not use chemicals have been proposed. Ion etching methods using parallel plate electrodes, etc., in which physical etching and chemical etching through chemical reactions proceed simultaneously, have been attracting attention.

In this method, for example, a pair of parallel plate electrodes facing each other are arranged in a reaction vessel, an object to be etched such as a substrate is placed on one of the plate electrodes, and an etching gas is introduced into the reaction vessel to maintain a predetermined pressure. A predetermined high frequency power is applied to the above-mentioned parallel plate electrodes in the etching gas atmosphere to generate reactive plasma, and the substrate, etc. is etched by the physical and chemical effects of the plasma.

FIG. 3a shows a schematic front sectional view of a conventional etching apparatus, in which a grounded reaction vessel 6 equipped with a gas introduction part 1 and an exhaust hole 9 has a gas introduced thereinto.
A grounded flat plate electrode 2 provided with a large number of pores 21 for ejecting 0 and a water-cooled substrate holding flat plate electrode 3 on which a plurality of silicon substrates 4 to be processed are placed are placed facing each other.
High frequency power is applied from a high frequency power source 5.

FIG. 3b shows a detailed sectional view of the substrate-holding flat plate electrode 3, and FIG. 3c shows a plan view thereof. It consists of an electrode cover 31 made of aluminum. Aluminum substrate holders 32 are dropped into eight holes drilled in the electrode cover 31. Electrode cover 31
The entire surface of the substrate holder 32 and the substrate holder 32 are insulated with alumite. Alumite insulation film is commonly used for this part because it is thin and tough and conducts heat well, but even when using insulation materials other than alumite, it is necessary to make it easier for the heat generated by etching to escape to the electrode. A thin insulating film is used. The substrate 4 is placed on the substrate holder 32.

The surface other than the substrate 4 as described above, that is,
The exposed surfaces of the electrode body 30 and the electrode cover 31 are covered with a Teflon resin film 8 (consisting of a side cover portion 80 and a front cover portion 81) for the purpose of further insulating the plasma and the electrode 3. In addition to Teflon, this coating uses insulating materials such as quartz, alumina, and synthetic resin.

FIGS. 4a and 4b show cross-sectional shapes of trench-etched grooves in the silicon substrate 4 when the surface of the silicon substrate 4 is trench-etched using the conventional apparatus described above. 11 is a SiO ₂ resist mask, and 12 is a silicon substrate. In FIG. 4a, a taper 13 is formed in the trench, and in FIG. 4b, a subtrench 14 is formed at the bottom of the trench.

The reason why the cross-sectional shape of the trench groove is abnormal as described above is said to be due to the following reason. In other words, insulation products generated by etching may accumulate around the substrate, and charges may be charged thereto, causing abnormal discharge. Exposed insulating films such as alumite are etched and become thinner, deteriorating voltage resistance and causing dielectric breakdown even at low self-bias voltages induced during etching, resulting in abnormal discharge. . When an abnormal discharge occurs, the self-bias voltage fluctuates violently over time as shown in Figure 4c, and due to this fluctuation in self-bias voltage, the cross-sectional shape of the trench etching groove and trench etching hole becomes tapered. This results in the formation of sub-trench grooves.

In order to solve this problem, the inventor conducted various experiments and tried to expose the electrode 3 or a conductor that is electrically connected to the electrode 3 in a part of the insulator 8 covering the electrode 3, and found that a good etching process could be achieved. It was discovered that the shape could be obtained with extremely good reproducibility. beginning,
As the conductor, noble metals such as stainless steel, gold, platinum, etc. were used. However, it has been found that these conductive materials have the disadvantage of causing metal contamination and damaging the substrate.

(Objective of the Invention) The present invention solves the above problems and provides an etching apparatus that can perform etching with good shape and quality with good reproducibility in the etching process during semiconductor device manufacturing, particularly in the trench etching process. For the purpose of providing.

(Structure of the Invention) The present invention provides a pair of opposing high-frequency power application electrodes arranged in a reaction vessel that can be evacuated to a vacuum.
The object to be etched is placed on the surface of one of the electrodes, the surface of the electrode exposed to plasma other than the placement part is covered with an insulator, and the object to be etched is etched by reactive gas plasma. In the etching apparatus, a part of the covered insulator is provided with a silicon carbide surface that is electrically connected to the electrode.
The above objective has been achieved.

(Function) As in the above configuration, when the silicon carbide surface that is electrically connected to the electrode is exposed on a part of the insulator that covers the electrode, this surface is electrically connected to the plasma in a direct current manner, so the insulator that covers the electrode and the generated deposits. The surface of the object is less likely to be charged, and even if it is charged, the potential is low and below the withstand voltage of the insulating film, and abnormal discharge due to dielectric breakdown or the like will not occur. Therefore, there is no variation in the self-bias voltage, and etching results with good shape and good reproducibility can be obtained.

On the other hand, unlike the metals mentioned above, silicon carbide (hereinafter referred to as SiC) does not become a source of metal contamination or dust, and compared to other conductors, the yield of products increases dramatically. .

(Example) Hereinafter, an example of the present invention will be described with reference to the drawings.

FIG. 1a shows a schematic front sectional view of an etching apparatus according to an embodiment of the present invention. Similar to FIG. A grounded flat plate electrode 2 provided with pores 21 for spouting the processed gas 10 and a water-cooled substrate holding flat plate electrode 3 on which a plurality of silicon substrates 4 to be processed are placed are placed facing each other. Power is applied.

FIG. 1b shows a detailed cross-sectional view of the substrate-holding flat electrode 3, and similarly to FIG. and an electrode cover 31 made of aluminum. In the eight holes around the electrode cover 31,
An aluminum substrate holder 32 is dropped. The electrode cover 31 and the substrate holder 32 are
Each surface is anodized and insulated.
The substrate 4 is placed on the substrate holder 32.

The difference between this device and the conventional device described above is that a new large hole is made in the center of the electrode cover 31, and the SiC cover 7 is installed in this hole to expose its surface. is a SiC main body 70 fixed to the electrode 3 with a fixing bolt 73
and a SiC lid 71 that covers the upper part of the fixing bolt 73.

After doing the above, board 4 and SiC cover 7
The exposed surfaces of the electrode body 30 and the electrode cover 31 other than those shown in FIG.

FIG. 2a shows the cross-sectional shape of the trench etching groove on the substrate 4 when the surface of the silicon substrate 4 is trench-etched using the apparatus of the above embodiment. 11 is a SiO ₂ resist mask, and 12 is a silicon substrate. There is no taper or sub-trench in the trench, and the cross-sectional shape is almost ideal.

At this time, the temporal change in self-bias voltage is extremely flat, as seen in Figure 2b.
It was found that there were no abnormal discharges.

When a stainless steel plate cover was placed in place of the SiC cover 7, the shape of the trench etching groove was good, but due to sputtering during etching, heavy metals such as iron, nickel, and chromium were released into the atmosphere. The particles re-adhered to the substrate 4 or were implanted into the substrate 4, causing a short circuit in the semiconductor device of the product or deterioration of the withstand voltage or fluctuation of the threshold value of the semiconductor element, resulting in a decrease in yield.

When a noble metal cover such as gold or platinum is used, it is chemically stable and durable against the corrosive gases of etching, but the cover is chemically stable and durable against the corrosive gases of etching. Neutral species and ions were likely to re-deposit, causing the same problems as described above. Precious metals are also too expensive.

When a cover made of a light metal such as aluminum is used, it is easily corroded by corrosive gas and has a short life span, and sputtering during etching causes the same problems as described above.

Even when using a pure carbon cover here,
The contamination was the same.

In contrast, a silicon carbide cover resists corrosive gases well, and carbon contamination of the device due to sputtering is greatly reduced. The surface of silicon carbide is slightly etched during the etching process, but
This is rather advantageous since it has the effect of preventing the formation of an insulating polymer film on the silicon carbide surface and ensuring direct current conduction.

Note that although the pair of opposing electrodes are described as parallel plate electrodes in the above description, the electrodes do not need to be in the shape of a flat plate. It may have a cylindrical shape.

Furthermore, the pattern of exposure of the silicon carbide surface may have a shape other than the above-mentioned circular shape, and can be selected quite freely.

(Effects of the Invention) According to the present invention, in the etching process during semiconductor device manufacturing, particularly in the trench etching process,
To provide an etching device capable of etching a good shape and high quality with good reproducibility.

[Brief explanation of the drawing]

Figures 1a, b, and c are explanatory diagrams of an etching apparatus according to an embodiment of the present invention, and a is a schematic cross-sectional view of the apparatus;
b is a detailed view of the substrate holding flat plate electrode portion, and c is a plan view thereof. FIG. 2a is a sectional view of a trench etched groove processed by the etching apparatus according to the embodiment of the present invention. FIG. 2b is a diagram of the temporal change in the self-bias voltage at that time. 3a, b, and c are explanatory diagrams of a conventional etching apparatus, in which a is a schematic cross-sectional view of the apparatus, b is a detailed view of the substrate-holding flat electrode portion thereof, and c is a plan view. FIGS. 4a and 4b are cross-sectional views of trench etching grooves processed by the above-mentioned conventional etching apparatus. FIG. 4c is a diagram of the temporal change in self-bias voltage at that time. DESCRIPTION OF SYMBOLS 1...Gas introduction part, 2...Electrode, 3...Substrate holding plate electrode, 4...Object to be etched, 5...High frequency power source, 6...Reaction container, 7...SiC cover, 8
...Insulator, 9...Exhaust hole, 10...Gas, 11
...SiO ₂ resist mask, 12...substrate.

Claims (1)

[Claims] 1. Arranged in a reaction container that can be evacuated to a vacuum,
An object to be etched is placed on the surface of one of a pair of opposing high-frequency power application electrodes, and the
In an etching apparatus configured to cover a surface exposed to plasma other than the mounting part with an insulating material and etching the object to be etched using reactive gas plasma, a part of the covered insulating material is provided with the electrode and the etching device. An etching device characterized by having a conductive silicon carbide surface.