JPH0722154B2 - Dry etching equipment - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a dry etching apparatus which is used for pattern formation of a high-density solid-state element including a semiconductor integrated circuit, and which can achieve uniform etching with high accuracy.

[Technical Background of the Invention and Problems Thereof] In the manufacture of a semiconductor large-scale integrated circuit (LSI), a resist pattern having a predetermined shape is formed by using a lithographic technique on a work piece maintained on the entire surface of a substrate. The material is etched using the resist pattern as a mask to form a pattern. Therefore, the etching technology is an important technology that determines the pattern accuracy, and the processability, reproducibility, and
Development has been advanced with the aim of improving uniformity and controllability.

The etching technique widely used at present is a dry etching technique called reactive ion etching (RIE), which is a reaction vessel 7 having a gas inlet 1 and an outlet 3 as shown in FIG. There are two discharge electrodes 5 held parallel to each other inside, and a substrate 9 is placed on one of the discharge electrodes 5. Then, a gas containing an element which reacts with the material to be processed and becomes a volatile reaction product is introduced from the gas introduction port 1, and the pressure in the reaction vessel 7 is evacuated and adjusted to be a constant pressure. Then, a high-frequency voltage source 11 applies a high-frequency voltage between the discharge electrodes 5 to generate glow discharge, and the work piece is etched by highly reactive active species generated in the plasma region 13 between the discharge electrodes 5. It is a thing. Since this method has no undercut and has high controllability, it is an indispensable technique for manufacturing a high-density LSI having a pattern of 1 μm or more.

However, in this conventional method, when etching a finer submicron-width groove, the etching rate decreases as the groove width becomes narrower and the groove becomes deeper, and the etching completion time depends on the groove width. The problem of being different has arisen (eg M.oda et al, Proc.Symp.on
Dry Process, Tokyo, Oct., P.115 (1984)).

To explain this problem in more detail, the active species used for this type of dry etching include ions and radicals, but the ions are shown in the ion sheath portion (reference numeral 15 in FIG. 4) in which a constant bias is maintained. (According to the portion) and accelerated to enter the etching surface from the direction perpendicular to the substrate 9. On the other hand, electrically neutral radicals are generated by the ion sheath 15
It is incident from every angle where plasma can be expected from the etching surface without being affected by. Therefore, the amount of radicals reaching the bottom surface of the groove to be etched is the width of the groove,
It depends on the depth.

FIG. 5 is an enlarged view showing the inside of the groove during etching. Radicals that can be incident on the bottom surface 19a of the groove 19 without colliding with the mask 17 or the side surface of the groove 19 are It is limited to those that can be incident from the range of the angle θ determined by the depth and the height of the mask. Therefore, if the groove width becomes narrower or the groove becomes deeper and the angle θ becomes smaller, the groove bottom surface 19a
Therefore, there is a problem that the amount of radicals arriving at is reduced, and thus the etching rate is reduced.

More specifically, using numerical values, for example, if a groove with a width of 2 μm and a groove with a width of 0.5 μm are etched at the same time, it becomes 2 μm.
Even if the m-width groove is completed, the situation where the 0.5 μm-width groove is etched by about 70% occurs, and if etching is continued until the 0.5 μm-width groove is completely etched,
The groove having a width of 2 μm is over-etched, which causes problems such as increased undercut and damage to the underlying material. Further, since the LSI pattern includes grooves having a width of 0.5 to several hundreds of μm, this problem is an extremely serious obstacle to the realization of an LSI having a submicron width.

[Object of the Invention] The present invention has been made in view of the above, and an object of the present invention is to provide a dry etching apparatus capable of performing highly accurate and uniform etching at a uniform etching rate even when patterns of various widths are mixed. To provide.

[Summary of the Invention] In order to achieve the above object, in a dry etching apparatus in which a reactive gas is glow-discharged to generate low-temperature gas plasma, and a substrate surface is etched by using active species generated in the plasma, The invention is summarized in that a filter means having a through hole of a predetermined size having a height larger than a width is provided on the substrate while maintaining a distance from the substrate at a predetermined distance.

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

FIG. 1 is a block diagram of a dry etching apparatus according to an embodiment of the present invention. The dry etching apparatus shown in FIG. 4 is the same as the dry etching apparatus shown in FIG. 4 except that one of the discharge electrodes 5 on which the substrate 9 is placed is the portion of the ion sheath portion 15 between the two discharge electrodes 5. The other configuration is the same except that the filter 21 is provided above the filter at a predetermined interval, and the same reference numerals are given to the same components.

This filter 21 has a through hole 21a having a predetermined diameter and length, as shown in FIG.
Are formed at a predetermined interval, and the filter 21
This material is formed of an insulating plate that does not affect discharge and does not generate abnormal discharge. By disposing this filter 21 on the substrate 9, a plasma region 13 formed by causing glow discharge to occur between the discharge electrodes 5 to which a high frequency voltage is applied by the high frequency voltage source 11 as described above.
Among the active species having a high reactivity generated in step 2, the active species moving in an oblique direction with respect to the substrate 9 collide with the side wall of the filter 21 and disappear. As a result, the plasma region 13
The groove to be etched in the substrate 9 through the filter 21 from
The active species that can be incident on 9a are limited to those having an incident angle of α in FIG. 2, and the active species have a distribution having a strong directivity in the direction perpendicular to the substrate 9. Therefore, the amount of active species that reaches the unit area of the bottom of the groove 9a is constant and uniform regardless of the groove width, and it is possible to etch fine grooves or wide grooves at the same speed, The depth of the groove does not increase and the etching rate does not decrease.

As can be seen from FIG. 2, the incident angle distribution of the active species incident on the groove 9a of the substrate 9 is determined by the thickness of the filter 21, that is, the through hole 21.
It is determined by the length and diameter of a and the distance between the substrate 9 and the filter 21. And the thicker the filter 21 is,
The smaller the diameter of the through hole 21a, the more the substrate 9 and the filter 21.
The larger the distance between and, the stronger the directivity of the active species in the vertical direction with respect to the substrate 9, and the smaller the groove width dependence of the etching rate. However, if the distance between the substrate 9 and the filter 21 is much larger than the mean free path of the gas, the probability that radicals that have passed through the filter 21 collide with the substrate 9 before entering the substrate 9 and lose directionality is increased. The effects of 21 are reduced. Further, the effective installation location of the filter 21 is the ion sheath portion 15 where almost no active species are generated, and even if it is installed in the plasma region 13, there is no effect.

Further, when etching a region wider than the inner diameter of the through hole 21a by using the filter 21, the filter 21 or the substrate 9 is formed so that the incident amount of active species becomes constant on the entire surface of the substrate 9.
It is effective to vibrate in a horizontal direction to etch.

FIG. 3 is a graph comparing etching characteristics when the present invention is applied and when it is not applied.

The etching characteristics shown in the figure are that the filter 21 has an inner diameter of 2 mm, an outer diameter of 3 mm, and a height of 10 mm, and 80 glass tubes are bundled to form a filter having a diameter of 50 mm, and a normal reactive ion etching (RIE) is performed. We are investigating whether the filter is used or not. In this case, a 4-inch diameter silicon wafer is used as the substrate,
Moreover, it was applied on this silicon wafer as a work material.
A 2.0 μm photoresist was used. An opening hole of 0.3 μm to 5 μm was formed in the 0.2 μm thick silicon resin coated on the photoresist using electron beam lithography and RIE of CF ₄ to form an etching mask. Further, oxygen was used as an etching gas, and etching was performed under the conditions of a gas flow rate of 30 SCCM, a pressure of 40 m Torr, and a discharge power of 0.2 W / cm ² . And depth
The relationship between the groove width and the depth when etching is performed with a target of 1.4 μm is shown in the graph of FIG. 3. In this figure, the etching depth is standardized to 1.4 μm and the curve A represents the present invention. A case where the present invention is applied, and a curve B is a graph when the present invention is not applied.

As can be seen from this graph, when the present invention is not applied (curve B), the etching depth decreases as the width becomes narrower in the region where the groove width is 1.5 μm or less, and the etching rate becomes slower. When the invention is applied (curve A), a uniform etching depth is obtained when the groove width is 0.5 μm or more, and the etching depth decreases when it becomes 0.5 μm or less. That is, in this embodiment, when the present invention is applied, it is possible to perform etching with high precision even in a groove having a width narrower by about one third as compared with the conventional method.

In the above embodiment, if the diameter of the glass tube used for the filter is made smaller, even finer grooves, for example, submicron width grooves can be etched uniformly and with high precision.

Further, although the case of reactive ion etching (RIE) has been described in the above embodiment, the present invention is not limited to this, and the present invention can be applied to all dry etching apparatuses that perform etching using reactive gas plasma. In addition, the present invention further includes, for example, Si, SiO ₂ , Si ₃ N ₄ , PSG, Al, Mo,
It can be applied to dry etching of all materials related to LSI manufacturing such as W, Ti, Ta, and silicone resin. An apparatus for separating the plasma generation chamber and the sample chamber and transporting plasma between the chambers for etching has also been proposed.
Even in this case, by installing a filter having a through hole in the plasma transport portion on the substrate, uniform etching independent of the groove width can be achieved.

[Effects of the Invention] As described above, according to the present invention, since the filter means having the through hole of a predetermined size whose height is larger than the width is provided on the substrate at a predetermined distance, this filter is provided. By the means, only the active species in the direction substantially perpendicular to the substrate hits the desired groove to be etched in the substrate, and the amount of the active species per unit area is uniform regardless of the groove width, etc. Even if it is narrow or wide or different, there is no variation and it is possible to perform highly precise and highly selective etching up to a submicron width groove at the same constant uniform speed, which is useful for developing high density, large capacity LSI. You can make a big contribution.

[Brief description of drawings]

FIG. 1 is a block diagram of a dry etching apparatus according to an embodiment of the present invention, FIG. 2 is a partially enlarged sectional view of the dry etching apparatus of FIG. 1, and FIG. 3 is a case where the present invention is applied and a case where it is not applied. 4 is a graph showing a comparison of etching characteristics in FIG. 4, FIG. 4 is a configuration diagram of a conventional dry etching apparatus, and FIG. 5 is a partially enlarged cross-sectional view for explaining the operation of the apparatus of FIG. 5 ... Discharge electrode, 7 ... Reaction vessel, 9 ... Substrate, 9a ... Groove, 21 ... Filter, 21a ... Through hole.

Claims (1)

[Claims] 1. A dry etching apparatus in which a reactive gas is glow-discharged to generate a low-temperature gas plasma, and the surface of a substrate is etched by using active species generated in the plasma, in a gap between the substrate and the substrate. The dry etching apparatus is characterized in that a filter means having a through hole of a predetermined size whose height is larger than its width is provided while maintaining a predetermined distance.