JPS62144330A - Reactive sputtering etching method - Google Patents

Abstract

PURPOSE:To prevent the temperature rise of a substance substrate to be etched, and to obviate the roughening of an etching surface, the undercut of an etching shape, the deterioration in selectivity with a mask material, etc. by lowering the temperature of cooling water in an electrode within a predetermined range. CONSTITUTION:In a parallel plate type dry etching device, single crystal silicon or polycrystalline silicon as substances to be etched 4 is arranged closely on a target electrode 2 in a vacuum chamber 1. When a substance such as silicon tetrachloride is blown off from a gas blow-off pipe 5 is turned ON, plasma is generated between a counter electrode 7 and the target electrode 2 in which discharge intervals are determined, and etching progresses. Cooling water 9 is circulated into the target electrode 2 by a refrigerating circulator 8 in order to prevent the temperature rise of a substrate composed of the substance to be etched 4. An excellent value can be acquired within the range of the temperature of cooling water of 0--20 deg.C at the selection ratio of silicon as the substance to be etched to an silicon oxide film as a mask material.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a reactive sputter etching method using one parallel plate dry etching device.

[Conventional technology]

The reactive spack etching method has become an indispensable technique for manufacturing semiconductor devices.

It is no exaggeration to say that the etching characteristics of this etching method are determined by the combination of the target electrode member and etching introduction gas suitable for the material to be etched. In this method, active ions in the plasma generated by applying a high-frequency electric field between two electrodes located on parallel plates are accelerated in an ion sheath zone near the surface of the electrode (on the cathode side where the material to be etched is placed), and the material to be etched is On the surface of a substrate made of material, an etching reaction progresses due to physical ion bombardment and chemically active neutral molecules generated in plasma. These etching reactions involve ion sputtering heat,
As the temperature of the material to be etched increases due to the heat of the chemical reaction, the temperature of the material to be etched gradually rises.

In the conventional reactive sputter etching method, cooling water maintained at a room temperature of about 20 DEG C. is circulated inside the electrode in order to prevent these temperature increases.

[Problem that the invention seeks to solve]

Recently, miniaturization and high aspect ratio have been imposed on dry etching processing technology. - In the element isolation method as an example,
Since a deep groove of about 3 to 10 .mu.m is required to be dug in the silicon substrate, the etching time is much longer than in the past, and the temperature of the substrate of the material to be etched tends to rise accordingly.

Normally, the causes of problems in reactive sputter etching are the deposition of products due to re-reaction with halogen compounds in the plasma due to temperature rise, the roughening of the surface of the material to be etched due to re-deposition, and the above-mentioned re-deposition. The increase in substrate temperature during reactive sputter etching has adverse effects in many ways, such as a decrease in etching speed and a decrease in accuracy in etching such as undercuts in the cross-sectional shape of grooves.

The object of the present invention is to reduce the temperature of the etched material caused by an increase in substrate temperature in reactive sputter etching.
It is an object of the present invention to provide a reactive sputter etching method that can prevent flow of the surface of the material to be etched, undercutting of the etched shape, decrease in etching rate, decrease in selectivity with the mask material, etc.

[Means for solving problems]

The present invention provides a reactive sputter etching method using a dry etching device in which a substrate made of a material to be etched is closely spaced on an electrode and cooling water is circulated inside the electrode, in order to maintain the electrode at a low temperature. The temperature of the cooling water inside the electrode is controlled within the range of 0 to -20°C. The cooling water should be mixed with ethylene glycol to prevent it from freezing even at temperatures below 0°C.

[Effect]

By lowering the temperature of the cooling water inside the electrode to a range of 0 to -20°C, it is possible to prevent the temperature of the substrate to be etched from rising, and prevent the etching surface from being caused by deposits, redeposit, etc., which are problems during reactive spuck etching. Etching is possible without causing defects such as roughness of the etching, undercutting of the etched shape, and decreased selectivity with the mask material.

〔Example〕

Embodiments according to the present invention will be described with reference to the drawings.

FIG. 1 shows the basic structure of a parallel plate type dry etching apparatus used in the practice of the present invention. In this parallel plate type dry etching apparatus, a target electrode 2 (the target electrode material is generally metal, but it is made of alumina immersed in thermal conductivity to prevent metal contamination during etching and to take into account the etching characteristics) is placed in a vacuum chamber 1. Single crystal silicon or polycrystalline silicon, which is the material to be etched 4, is closely placed on top of the electrode covering member 3 (a grooved plate made of a ceramic material such as the above may be used as the electrode covering member 3). Next, silicon tetrachloride, for example, is blown out from the gas blowing pipe 5 as an etching introduction gas, and a high frequency type #+
6, plasma is generated between the opposing electrode 7 which determines the discharge interval and the target electrode 2, and etching progresses. Correspondingly, the substrate temperature of the material to be etched 4 increases.

In order to prevent this rise in substrate temperature, cooling water 9 is circulated inside the target electrode 2 by a refrigeration circulation machine 8 .

FIG. 2 shows the selection ratio between silicon, which is the material to be etched, and silicon oxide film, which is the mask material, depending on the cooling water temperature setting side.

When the temperature of the cooling water is 20° C. (room temperature) as in the conventional case, the substrate temperature of the material to be etched 4 rises to about 150° C., and a good selection ratio of 5 cannot be obtained. According to experiments conducted by the inventor, the cooling water temperature ranges from 0 to -20°C.
A good selectivity ratio could be obtained within the range of . It was also confirmed that by lowering the temperature of the cooling water to 0 to -20 DEG C., defects such as roughness of the etched surface, undercutting of the etched shape, and grooves did not occur.

As described above, in the reactive sputter etching method of this embodiment, a refrigerating circuit 8 is used inside the target electrode 2 in order to prevent the temperature of the substrate of the material to be etched from rising as the etching progresses. It is preferable to circulate cooling water 9 at a temperature of -20 DEG C. to maintain the substrate of the material to be etched, which is disposed in close proximity to the target electrode 2, at a low temperature.

〔Effect of the invention〕

According to the present invention, it is possible to prevent the temperature of the material to be etched during etching from rising, thereby preventing roughening of the surface of the material to be etched due to re-deposition by re-reactants, undercutting of the cross-sectional shape, reduction in etching speed, etc. Excellent effects such as high selectivity with other materials can be obtained.

[Brief explanation of drawings]

Fig. 1 is a block diagram of a dry etching apparatus used in an embodiment of the present invention, and Fig. 2 is a graph showing the selectivity ratio between silicon, the material to be etched, and oxide film, the mask material, depending on the cooling water temperature setting. It is. 1 ・・・・・・・・・・・・・・・ Vacuum chamber 2 ・・・
・・・・・・・・・・・・ Target electrode 3 ・・・
...... Electrode covering member 4 ...
...... Material to be etched 5 ...
・・・・・・・・・・・・ Gas blow-off pipe 6 ・・・・・・
・・・・・・・・・ High frequency power supply 7 ・・・・・・・・・
...... Counter electrode 8 ......
・・・・・・ Refrigeration circulation machine q ・・・・・・・・・・・・・・・
... Cooling water agent Patent attorney Yoshiyuki Iwasa Figure 1! Arrest Jfu2shi;, Warm/f (”c) Fig. 2

Claims (1)

[Claims] (1) In a reactive sputter etching method using a dry etching device in which a substrate made of a substance to be etched is placed closely on an electrode and cooling water is circulated inside the electrode, the inside of the electrode is kept at a low temperature. A reactive sputter etching method characterized by controlling the temperature of cooling water within a range of 0 to -20°C.