JPH0513319A - Pattern formation - Google Patents

Abstract

PURPOSE:To form a fine pattern very accurately and efficiently. CONSTITUTION:This method includes a process wherein a thin carbon film 17 is applied onto the whole surface of the material to be patterned 16, a process wherein charged particle beam 1 is applied to a specified place of the surface of the carbon film 17 in an activated oxygen gas atmosphere for progressing the etching of the part irradiated with the charged particle beam, a process of patterning the carbon film 17, and a process wherein a directional etching is conducted by RIE with the patterned carbon film 17 used as a mask for transferring a pattern of the carbon film 17 onto the material to be patterned 16.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for patterning a semiconductor device using a charged particle beam.

[0002]

2. Description of the Related Art Conventionally, formation of a wiring pattern in a semiconductor device has been performed as follows. First, after a wiring material such as aluminum is deposited on the entire surface of the substrate, a resist is applied on the wiring material, and the resist is selectively exposed using light or an electron beam. At this time, an exposure light source having a higher resolution is required as the pattern becomes finer.
An electron beam is used exclusively for ultrafine processing of μm or less. After that, development is performed to form a resist pattern, and directional etching such as reactive ion etching is performed using the resist pattern as a mask to transfer the pattern to the wiring material. Finally, the unnecessary resist pattern was removed by stripping.

However, in such a pattern forming method, in order to improve the accuracy of the finally formed pattern, it is necessary to improve not only the resolution of the exposure light source but also the developing characteristics of the resist material and the accuracy of the etching technique. In particular, it has been considered almost impossible to realize the precision of a fine pattern of 0.1 μm or less.

Therefore, as a method for realizing the precision of a fine pattern of 0.1 μm or less, a direct writing process using a focused energy beam is being studied. This is based on the property that when a sample is irradiated with an electron beam or an ion beam in a reactive gas atmosphere, the reaction between the reactive gas adsorbed on the surface of the sample and the sample material is promoted and etching or deposition occurs. , To directly pattern the sample,
The etching rate at this time is determined by the density of the adsorbed gas on the sample surface, which depends on the pressure of the reactive gas, the energy and electric charge of the beam, and the reaction probability between the adsorbed gas and the sample surface molecules due to the beam. Incidentally, processing examples of silicon, silicon oxide film, silicon nitride film, resist material and the like using a reactive gas such as xenon fluoride, chlorine trifluoride and tungsten hexafluoride and an electron beam have been reported.

According to this, the pattern accuracy is limited only to the size of the focused energy beam (including scattering in the solid), and in addition, resist coating, exposure and development steps, and further pattern transfer and resist removal. Since the process can be omitted, it is expected as a technology that can meet the demands for ultra-fine processing and shortening the number of processes.

[0006]

However, in the above-mentioned conventional direct writing process using the focused energy beam, the amount of adsorbed gas is increased. Therefore, when the gas pressure is increased, the beam does not reach the sample and a large current is applied to the sample. When the electron beam is irradiated at a high density for a long time, a hydrocarbon-based deposit that interferes with the etching reaction is generated due to the residual gas component, so that the etching rate is reduced, which is not practical.

Further, if the background vacuum is set to a high vacuum and carbon-free so that the above-mentioned deposit does not hinder the etching reaction, there is a problem that the apparatus becomes large in scale.

As described above, it is extremely difficult to accurately form an ultrafine pattern of 0.1 μm or less, and even if it is possible, there is a problem that the efficiency is extremely low.

The object of the present invention is to solve the above-mentioned problems.
Provided is a pattern forming method capable of forming a fine pattern with high accuracy and high efficiency.

[0010]

In order to achieve the above-mentioned object, the present invention comprises a step of forming a carbon film on a material to be patterned, and a step of forming the surface of the carbon film in an activated oxygen gas atmosphere. The step of irradiating a predetermined portion with the charged particle beam to etch the portion of the carbon film irradiated with the charged particle beam to pattern the carbon film, and the patterned carbon film
Directional etching using the carbon film as a mask to transfer the pattern of the carbon film to the material to be patterned.

[0011]

In the present invention, since the carbon film is used as an etching mask in an oxygen gas atmosphere, a large etching selectivity with respect to the material to be patterned can be obtained, and many kinds of materials can be accurately patterned. Also, the car
Since the carbon film is a thin film, the scattering of the charged particle beam in the carbon film is suppressed, and the carbon film is patterned with high accuracy. In addition, the amount of etching by the charged particle beam is reduced, and the etching processing time is shortened. Furthermore, since the oxygen gas is activated, the reaction probability between the oxygen gas and the carbon film is increased, and a high etching rate can be obtained.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the pattern forming method of the present invention will be described with reference to FIGS.

FIG. 1 is a process diagram of a wiring pattern forming method. Further, FIG. 2 shows a configuration diagram of an electron beam etching apparatus used for forming a wiring pattern.

First, for convenience of explanation, an electron beam etching apparatus will be described. This etching apparatus includes a lens barrel 2 having an electron optical system for generating, focusing and scanning an electron beam 1, and a sample stage 4 for placing a sample substrate 3 which is separated from the lens barrel 2 by an aperture 6. The sample chamber 5 provided, the exhaust systems 7 and 8 that differentially exhaust the lens barrel 2 and the sample chamber 5 to supply the activating gas into the sample chamber 5 without affecting the electron optical system, and the supply of the activating gas. And means 100.

The activating gas supply means 100 is a quartz discharge tube 9 fixed in the sample chamber 5 so that one end thereof faces.
A gas introduction system 11 including a mass flow controller 10 connected to the other end of the quartz discharge tube 9; and a coaxial cable 1
High-frequency oscillator 12 connected to the quartz discharge tube 9 via 3
And a coaxial cable 13 provided in the middle of the quartz discharge tube 9.
And a high frequency cavity 14 for supplying the high frequency power transmitted from the high frequency oscillator 12 into the quartz discharge tube 9.

Next, a method for forming a wiring pattern of a semiconductor device using such an electron beam etching apparatus will be described. First, an aluminum alloy film 16 having a thickness of 8000 angstrom is formed on the silicon dioxide film 15 by sputtering, and a carbon thin film 17 having a thickness of 1000 angstrom is laminated on the aluminum alloy film 16 by sputtering to form a sample substrate 3. Formed (FIG. 1a).

Next, the sample substrate 3 is placed on the sample stage 4 in the sample chamber 5 which is evacuated to 1 × 10 ^-6 Torr by the exhaust systems 7 and 8, and then the gas introduction system 11 is placed.
Further, 10 sccm of oxygen gas is introduced into the quartz discharge tube 9, and the pressure in the sample chamber 5 is maintained at 1 × 10 ⁻³ Torr. At this time,
The inside of the lens barrel 2 is kept at 10 ⁻⁶ Torr level. Thereafter, 100 W of 2.45 GHz high-frequency power oscillated from the high-frequency oscillator 12 is applied into the quartz discharge tube 9 through the high-frequency cavity 14 to discharge the gas. Active neutral particles such as O ^* , electrons and oxygen ions are present in this discharge gas,
Only active neutral particles such as O ^{* having} a long life are transported to the sample chamber 5 together with oxygen molecules and guided to the surface of the sample substrate 3. Therefore, when the surface of the sample substrate 3 is irradiated with the electron beam 1 and the region of the aluminum alloy film 16 to be removed is drawn by the electron beam 1, only the carbon thin film 17 in the irradiation region is etched and a mask pattern is formed. At this time, the irradiation conditions are an acceleration energy of 20 KeV and an irradiation amount of 200 μC / cm ² (FIG. 1b).

Here, when oxygen gas was not activated and was supplied as it was and drawing was performed under the same conditions as described above, hydrocarbon-based deposits were observed in the irradiation region, and etching of the carbon thin film 17 was not observed. It was This is because the residual gas component adsorbed on the surface of the carbon thin film 17 is decomposed or polymerized more easily than the reaction between oxygen and the carbon thin film 17 by the irradiation of the electron beam 1 to form a film. on the other hand,
When O ^* is supplied, oxygen atoms are quickly combined with the decomposed residual gas component and exhausted as carbon dioxide.

Then, the patterned carbon thin film 17 is formed.
Directional etching of the aluminum alloy film 16 is performed by a normal reactive ion etching method using the mask as a mask (FIG. 1).
c).

Finally, the carbon thin film 17 is removed by plasma ashing treatment of oxygen or hydrogen, and the aluminum alloy film 1
The patterning of 6 is completed (Fig. 1d).

Thus, since the carbon thin film 17 is used as an etching mask in an oxygen gas atmosphere, a large etching selection ratio with the aluminum alloy film 16 can be obtained,
The patterning accuracy is improved. Further, since the carbon thin film 17 is a thin film, the scattering of the electron beam 1 in the carbon thin film 17 is suppressed, and the carbon thin film 17 is highly accurately patterned. Moreover, the amount of etching by the electron beam 1 is reduced, and the etching processing time is shortened. Further, since the oxygen gas is activated, the reaction probability between the oxygen gas and the carbon thin film 17 becomes high, and a large etching rate can be obtained. Therefore, a fine wiring pattern can be efficiently formed with extremely high precision. At the same time, by setting the acceleration energy of the electron beam 1 to 5 KeV or less, the etching rate is increased and efficient pattern formation can be performed. This is because the secondary electron emission rate of the solid due to electron beam irradiation is generally the maximum within the range of 0.1 to 2 KeV in the acceleration energy of the electron beam 1.

In this embodiment, the aluminum alloy film 1 is used.
Although the pattern formation of No. 6 has been described, the material is not limited to this, and any material that can be selectively etched with respect to carbon in the reactive ion etching step is not limited to the wiring material. For example, it goes without saying that it is also applicable to polycrystalline silicon, tungsten and the like.

Further, as an oxygen gas activating means, ozone may be supplied by using an ozonizer instead of applying high frequency power, which facilitates maintenance of the apparatus. Further, as the gas activation means, light irradiation, radiation irradiation, thermal decomposition, or the like may be used in addition to discharge.

Furthermore, the gas to be activated and supplied is not limited to oxygen, and other gas such as hydrogen gas may be used. In this case, the underlying aluminum alloy or the like exposed during patterning of the carbon film may be used. Oxidation of the surface can be suppressed, and the processing time of the next step, reactive ion etching, can be shortened.

Next, a method of forming a fine element isolation region will be described.

First, a silicon dioxide film 15 having a thickness of 500 angstrom is formed on a silicon substrate 18 by thermal oxidation, and further, a thickness of 1500 is formed on the silicon dioxide film 15 by LPCVD.
An angstrom silicon nitride film 19 is laminated to form a sample substrate 3 (FIG. 3a).

Then, the sample substrate 3 is placed on the sample stage 4
After mounting on top, oxygen gas 10 sccm and tetrafluoromethane 10 sccm are introduced into the quartz discharge tube 9 and activated by applying high frequency power. Thus, O ^* and F
^{When the} electron beam 1 is irradiated while guiding active neutral particles such as ^* to the surface of the sample substrate 3, the etching reaction of the irradiation portion of the silicon nitride film 19 is promoted and a pattern is formed. At this time, the acceleration energy of the electron beam 1 is 20K
The eV and irradiation dose are 400 μC / cm ² , and irradiation is performed in two times (FIG. 3b).

Then, after a predetermined cleaning process, normal field oxidation is performed using the patterned silicon nitride film 19 as a mask (FIG. 3c).

Finally, part of the silicon dioxide film 15 and the silicon nitride film 19 are removed to form an element isolation region 20 (FIG. 3d).

Thus, a fine element isolation region is easily formed.

By the way, the silicon nitride film 19 is etched by a mixed gas containing O ^* and F ^* even without irradiation of the electron beam 1. This has already been put to practical use as a downflow etching process. In this embodiment, since the pressure in the sample chamber 5 is extremely lower than that in the normal downflow process, the etching rate of the entire surface of the silicon nitride film 19 is 5 angstroms / minute or less, and one sample substrate 3 is drawn. The film loss between them is about 100 to 200 angstroms. Therefore, the electron beam 1
Irradiating in multiple times or more to locally accelerate the etching reaction or to keep the sample substrate 3 at 0 ° C. or lower to suppress the etching action by O ^* and F ^* , and operate only the electron beam irradiation part. The patterning is effectively performed by controlling the etching process.

[0032]

As described above, according to the present invention, a large etching selection ratio can be obtained between the carbon film and the material to be patterned, and many kinds of materials can be accurately patterned. Further, the scattering of the charged particle beam in the carbon film is suppressed, and the carbon film is patterned with high accuracy. Furthermore, the amount of etching by the charged particle beam is reduced,
The etching processing time is shortened. In addition, the reaction probability between the oxygen gas and the carbon film becomes high, and a large etching rate can be obtained. Therefore, a fine pattern of the material to be patterned can be formed with high efficiency and high accuracy.

[Brief description of drawings]

FIG. 1 is a process diagram illustrating a wiring pattern forming method of the present invention.

FIG. 2 is a configuration diagram of an electron beam etching apparatus used in the present invention.

FIG. 3 is a process chart illustrating a method for forming a fine element isolation region.

[Explanation of symbols]

 1 Electron Beam 3 Sample Substrate 9 Quartz Discharge Tube 11 Gas Introduction System 12 High Frequency Oscillator 16 Aluminum Alloy Film 17 Carbon Thin Film

Claims (1)

Claim: What is claimed is: 1. A step of forming a carbon film on a material to be patterned, and irradiating a predetermined portion of the surface of the carbon film with a charged particle beam in an activated oxygen gas atmosphere. This etches the portion of the carbon film irradiated with the charged particle beam to pattern the carbon film, and the patterned carbon film.
A step of performing directional etching using the carbon film as a mask to transfer the pattern of the carbon film to the material to be patterned.