JPS6320830A - Fine processing - Google Patents

Abstract

PURPOSE:To prevent a mask from being charged with electricity and carry out a favorable etching treatment by using conductive organic materials as a mask on the occasion of performing a selective etching treatment accompanied by irradiation of charged particles. CONSTITUTION:A mask 32 is formed to have a desired pattern on a processed base substance 31 and the processed base substance 31 is selectively etched in accordance with the pattern of the mask 32 by a dry etching accomapnied by irradiation of charged particles 33. In such a case, the conductive organic materials are used as materials for the mask 32. Thus, even though charged beams are irradiated on the conductive materials of mask, an electric charge is not accumulated in the mask 32 and the above conductive materials prevent the mask 32 from being charged with electricity. In the case of dry etching, consequently no large potential is developed in the mask pattern and such a state of conductive organic materials helps avoid causing disturbance of an etching treatment form as well as deterioration of an insulating film quality on a base and the like which are due to the charged mask 32.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Field of Application) The present invention relates to a microfabrication method, and particularly to a microfabrication method using a dry etching technique involving irradiation with charged particles.

Conventionally, in the manufacturing process of semiconductor integrated circuits, various techniques have been used for microfabrication. In etching, dry etching with higher dimensional accuracy has been used instead of wet etching. Furthermore, in order to obtain etching anisotropy, dry etching techniques involving irradiation with charged particles, such as reactive ion etching (RIE), are employed.

However, this type of method has various problems associated with charged particle irradiation. For example, a polycrystalline silicon sample is dry-etched using a photoresist pattern as a mask, and a thin [I S! In the process of forming a polycrystalline silicon pattern on 02 (gate oxide film),
It has been reported that the quality of the SiO2 film deteriorates, resulting in poor dielectric strength. In addition, defects in the shape of the die, which are thought to be caused by the charging of the mask pattern, have also been observed.

(The problem that the invention seeks to solve) In this way, in the conventional method, the mask is charged due to the irradiation of charged particles, and this charging causes the etched shape to be disturbed and the film quality of the underlying insulating film to deteriorate. There were some problems such as:

The present invention has been made in consideration of the above circumstances, and its purpose is to provide a microfabrication method that can solve various inconveniences caused by electrification of a mask and can perform good dry etching. There is a particular thing.

[Structure of the Invention] (Means for Solving the Problems) The gist of the present invention is to form a mask from a conductive material in order to prevent the mask from being charged by irradiation with charged particles.

That is, the present invention provides a microfabrication method in which a mask is formed in a desired pattern on a substrate to be processed, and the substrate to be processed is selectively etched according to the pattern of the mask by dry etching accompanied by irradiation of charged particles. This method uses a conductive paid material as the material.

Here, charging of the mask can basically be prevented by forming the mask with a conductive material, but since the mask pattern generally used during dry etching is a resist pattern made of a paid material, commercially available photolithography is used as the mask material. It is desirable to use materials. Furthermore, the conductive material is one that becomes conductive when irradiated with light, such as a photoconductive material.

Alternatively, the conductivity may be improved by light irradiation. Note that this optical excitation is not limited to light emission by the reaction gas within the etching container, but may also be light irradiation from a light source provided within or outside the container.

(Function) According to the above method, since the mask is made of a conductive material, even if the mask is irradiated with a charged beam, no charge is accumulated on the mask, and the mask is prevented from being charged. As a result, a large potential is not generated in the mask pattern during dry etching, and it is possible to prevent disturbances in the etched shape and deterioration of the underlying insulating film due to charging of the mask.

(Example) Hereinafter, details of the present invention will be explained with reference to illustrated embodiments.

FIGS. 1(a) to 1(f) are cross-sectional views showing a polycrystalline silicon gate forming process according to an embodiment of the present invention. Note that this step is an example using a so-called three-layer resist structure including a flattening layer, an intermediate layer, and a resist.

First, as shown in FIG. 1(a), an element isolation insulating film 12 and a gate oxide film (Si○zjl
>13 and doped polycrystalline silicon fl! on top of these. 14 was formed. Thereafter, as shown in FIG. 1 (1), a film 15 of polyvinylcarbazole, which is a paid material having photoconductivity, is applied to the polycrystalline silicon film 14 by about 100 ml.
．． Formed by spin code to a thickness of 8 [μTrL],
This was thoroughly dried. Next, apply S on this thin Pa15.
i3N4 thin film 16 was deposited to a thickness of approximately 500 cm.

Furthermore, a positive photoresist 17 (OFPR
-800, manufactured by Tokyo Ohka Co., Ltd.) at approximately 1.25 [μrrL
] thickness.

Next, by the usual glue sogerahuie process, Fig. 1 (C)
As shown in FIG. 2, the resist 17 was exposed and developed to form a resist pattern. Thereafter, 5iaN41J16 was selectively etched by RIE using a CF4/H2i1 gas mixture, using the resist 17 as a mask, as shown in FIG. 1(d). Subsequently, after removing resist 17, 02
By RIE using gas, as shown in Fig. 1(e),
The polyvinylcarbazole thin film 15 was selectively etched using the Si3N4 film 16 as a mask.

Then, by RIE using CF4/H2 mixed gas, 5
i3N41116 was completely removed. After that, CCQ+
Figure 1(f) was obtained by RIE using /He mixed gas.
As shown in FIG. 2, the underlying polycrystalline silicon film 14 was selectively etched using the polyvinyl carbazole thin film 15 as a mask. Next, the mask pattern was completely removed by O2 plasma ashing to form a polycrystalline silicon gate.

In addition, the above 5iiN41a16. Polyvinylcarbazole 1illa15. For each etching of the polycrystalline silicon film 14, a dry etching apparatus equipped with parallel flat plates 21 and 22 as shown in FIG. 2 was used. Then, a high frequency type 812 is placed on the lower double positive 22 side where the workpiece #i23 is placed.
Etching was performed while applying high frequency power from No. 4 and supplying a gas depending on the etching material.

Now, the microfabrication process according to the present invention is as shown in FIG.
This is selective etching of the polycrystalline silicon film 14 using the polyvinyl carbazole thin film 15 shown in ) as a mask. During this etching, the film becomes conductive due to light emission caused by polygonylcarbazole discharge, which serves as a mask. Therefore, even if the mask is irradiated with charged particles during etching, almost no charge is accumulated on the mask, and the mask is prevented from being charged.

Here, since the mask is conductive, the charge flowing into the mask escapes to the ground end etc. via the polycrystalline silicon film 14. Furthermore, when the polycrystalline silicon film 14 is completely etched, there is no way for the charges to escape, but the charges continue to escape until the polycrystalline silicon 11014 is completely separated, so the amount of charge accumulated in the mask is extremely small. Therefore, electric charges accumulated in the mask do not cause discharge or the like to occur between the mask and the substrate 11, and the underlying Si
This does not cause deterioration of the characteristics of O21J13.

On the other hand, if the mask is an insulator as in the prior art, charges will be accumulated in the mask during etching due to the irradiation of charged particles. When the polycrystalline silicon model 14 is completely separated, the amount of charge accumulated in the mask becomes extremely large. Therefore, when the polycrystalline silicon pattern 14 is completely separated, there is a possibility that a discharge will occur between the mask and the substrate 11 due to the charge accumulated in the mask, and this discharge will cause a breakdown in the dielectric strength of the underlying SiO2 film 13. etc. will be invited.

In this way, according to the method of this embodiment, the polycrystalline silicon film 1
Since the polyvinyl carbazole thin film 15 is used as a mask when selectively etching 4 by RIE, it is possible to prevent the mask from being charged, and the gate oxidation I11
It is possible to eliminate the characteristic deterioration described in No. 3. Furthermore, since the mask is not electrically charged, there is no problem such as bending of ions by charges accumulated in the mask, and a good etched shape can be obtained.

Note that the effects related to the above-mentioned processed shape are as follows: 7.
This is particularly effective in forming grooves with a large velocity ratio. That is, when a mask 32 is formed on a silicon substrate 31 as shown in FIG. 3(a) and a groove with a large aspect ratio is formed by selectively etching the silicon substrate 31 by RIE or the like, the mask 32 is conductive. Also, the mask 32 is not charged even by the irradiation of the ions 33. Therefore, the ions 33 are irradiated vertically into the groove, thereby making vertical etching possible.

On the other hand, if the mask 32 is an insulator, the ions 33
The mask 32 is charged by the irradiation.

When the mask 32 is charged, the ions 33 entering the groove are bent by the charge of the mask 32, as shown in FIG. 3(b). This makes it difficult to form vertical and deep grooves.

Note that the present invention is not limited to the method of the embodiment described above. For example, the material used for the mask is not limited to a photoconductive sterile material such as polyvinylcarbazole, but also a conductive precipitated material such as polyacetylene.
It may be 4. Generally speaking, when a photoconductive wired material is used as a mask, in order to ensure that the material is irradiated with light, a light source is provided outside the etching container, and from this light source a wavelength that improves the conductivity of the material is emitted. Alternatively, the area may be irradiated with light. Furthermore, the present invention can be applied not only to selective etching of polycrystalline silicon but also to selective etching of glass materials. Furthermore, the etching method is not limited to RIE, but can be applied to various dry etching methods that involve irradiation with charged particles. In addition, various modifications can be made without departing from the gist of the present invention.

[Effects of the Invention] As detailed above, according to the present invention, by using a conductive wired material as a mask during selective etching that involves irradiation with charged particles, it is possible to prevent the mask from being charged. Etching can be performed.

[Brief explanation of the drawing]

FIGS. 1(a) to (f) are top views showing the polycrystalline silicon gate forming process according to one embodiment of the present invention, and FIG. 2 is a schematic diagram of the dry etching apparatus used in the above embodiment method. The schematic diagrams shown in FIGS. 3(a) and 3(b) are schematic diagrams for explaining problems caused by charging of the mask. 11.31... Silicon substrate, 12... Insulating film for element isolation, 13... Gate oxide film (S i 02 FA
), 14... Polycrystalline silicon film, 15... Polyvinyl carbazole film (conductive organic material), 16... S
1yoN4 film, 17...photoresist, 21.22...
・Parallel plate electrophotography, 23... Processed substrate, 24... High frequency power source, 32... Mask, 33... Ion. Applicant's representative Patent attorney Takehiko Suzue S1 Figure 1 Figure 2 (a) Figure 31 (b)

Claims (6)

[Claims] (1) Form a mask in a desired pattern on the substrate to be processed,
A microfabrication method in which the substrate to be processed is selectively etched according to the pattern of the mask by dry etching accompanied by irradiation with charged particles, characterized in that a conductive organic material is used as the material of the mask. Microfabrication method. (2) The microfabrication method according to claim 1, wherein polyacetylene is used as the conductive organic material. (3) The microfabrication method according to claim 1, characterized in that, as the mask material, an organic material having photoconductivity that becomes conductive or has high conductivity upon irradiation with light is used. . (4) The microfabrication method according to claim 3, wherein polyvinylcarbazole is used as the organic material having photoconductivity. (5) The mask is irradiated with light in a wavelength range that improves the conductivity of the material forming the mask before or during the etching. Microfabrication method. (6) The mask is a flattening layer that is the lowest layer of a multilayer resist structure in which a flattening layer, an intermediate layer, and a resist are formed on a substrate having irregularities, and the patterned resist is used as a mask to form the intermediate layer. 2. The microfabrication method according to claim 1, wherein said layer is selectively etched, and said planarization layer is selectively etched using said intermediate layer as a mask.