JPS5897831A - Pattern formation - Google Patents

Abstract

PURPOSE:To allow the large impression of high frequency power and contrive the improvement of through-put and working accuracy, by fluoridizing a resist with fluoric radical accordingly contriving the improvement of heat resistance. CONSTITUTION:On a P type Si substrate 11, a thermal oxide film 12 1mum thick is produced by a dry oxidation at 1,000 deg.C, and succeedingly the novolak positive type resist 13 is applied for a spin coat on the thermal oxide film 12. Next, using a 1:1 projection exposer, a desired pattern is exposed on the resist, thereafter the development is peformed in alkaline developer for 90sec, and accordingly a resist pattern 14 is formed. It is set up in a chemical dry etching device and applied for a fluorization, and next, when contained in an oven and post- baked, the resist 13 is subject no damages, and a good etching pattern can be obtained at a high frequency power 1kW. Therefore, a practicable etching speed for the thermal oxide film 12 can be increased from approx. 1,500Angstrom /min up to approx. 3,000Angstrom /min.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a pattern forming method, and more particularly to an improvement in a resist pattern forming method prior to reactive ion etching of a silicon oxide film.

Technical Background of the Invention Near the melting point, reactive ion etching has been used to precisely etch fine patterns into thin films constituting VLSI devices. This reactive ion etching method
As shown in the figure, a sample 4 is placed on the high-frequency power application side electrode s of a pair of parallel plate electrodes 2.3 arranged in the vacuum chamber 1.
A gas containing at least one halogen atom in the molecule is introduced into the chamber 1, and an electrode 2.3 is placed on the chamber 1.
In this method, discharge plasma is generated by applying high-frequency power between the etching steps, and the portion of the sample 4 to be etched is etched using this plasma. During etching, the DC potential between the electrodes 2.3 becomes less noble with respect to the plasma potential P, as shown in FIG.

In particular, the difference between the potential (electrode peak) Q of the electrode 3 to which the horse leg power is applied and the plasma potential P is as large as several 100 EV). Due to this DC potential difference of several hundred (V), positive ions in the plasma are accelerated toward the electrode (electrode) 3 and bombard the object to be etched, causing an etching reaction to proceed. The reactive ion etching method is distinguished from the plasma etching method because it is characterized by this i, ion bombardment.

By the way, when etching a ``sjo'' film on a Si substrate using the reactive ion etching method, it is necessary to make the etching rate of Bi slower than the etching rate of sio. gas, CHF,
, C, F, or C, F, etc. are used. As a result, although the etching speed of Si is sufficiently slow,
The etching speed of aio is also slow and the throughput is low. sio.

In order to increase the etching speed, it is possible to increase the applied high-frequency power, but as the high-frequency power increases, the plasma potential 8 and gas temperature rise, which may cause problems such as thermal damage to the resist and roughening of the resist pattern. invite A possible solution to this problem is to cool the sample by adsorbing the sample to an electrode plate and cooling the electrode plate. However, in this case, an initial electrostatic chuck mechanism is required for the adsorption, and an etching device is required. In addition, since the resist was not directly cooled, it was difficult to cool it sufficiently.

OBJECTS OF THE INVENTION An object of the present invention is to provide a pattern forming method that can improve the heat resistance of a resist, thereby making it possible to apply a large amount of high-frequency power, thereby improving throughput and processing accuracy.

SUMMARY OF THE INVENTION As a result of extensive research into thermal damage to positive resists, the present inventors have discovered the fact that the higher the post-baking temperature of the resist, the more likely the resist is to be thermally damaged. However, the post-baking temperature is a certain constant temperature (
If the temperature exceeds λ (usually about 140C), the resist itself will soften,
There is a problem that the resist profile deteriorates. Therefore, as a result of intensive research by the present inventors for the purpose of hardening the resist, it has been found that when the resist surface is fluorinated using fluorine radicals, the core surface hardens and the 160
It has been found that the resist profile does not deteriorate even if host baking is performed at a temperature of E') or higher.

The present invention has focused on these points, and after exposing a resist coated on a film to be processed to a desired pattern, the resist is exposed to form a resist pattern, and then the remaining resist is exposed to fluorine using fluorine radicals. oxidation treatment, for example, a mixed gas plasma of CF4 and H, and then post-baking the resist at a temperature of 160 (C) or more,
In this method, the film to be processed is selectively etched using the resist as a mask using the rib reactive ion etching method.

Effects of the Invention According to the present invention, by fluorinating the resist with fluorine radicals, even if the resist is post-baked at a temperature of 160 (r) or more, it is possible to stick the resist profile due to the softening of the resist. Furthermore, by using the above-mentioned resist, thermal damage to the resist can be minimized even if the applied high-frequency power is increased.

Therefore, the etching speed of the processed film can be increased, and throughput can be improved. Furthermore, etching li! Since thermal damage to the resist can be reduced, processing precision can be improved.

Embodiment of the Invention FIGS. 3(a) and 3(b) are cross-sectional views illustrating a pattern forming process according to an embodiment of the present invention. First, the first
As shown in Figure (a), P-type B i III @ J J wo 1011198 and 1000
A thermal oxide film (film to be processed) 12 of 1 [μm] is formed by wet oxidation of (t?), and then a novolak positive resist 13 (product name OFPR-800) is formed on the thermal oxidation JIIJJ.
(manufactured by Tokyo Ohka) was spin coded. Next, a desired pattern was exposed on the resist using a 1:1 projection light exposure machine, and then development was performed for 90 seconds with an alkaline developer solution, and the third [
! A resist pattern 14 as shown in l(b) was formed.

The samples obtained in this way were divided into two sets of 5 sheets each, and one was placed in a chemical dry etching device (product name: CDE-11, manufactured by Tokuda Seisakusho), and CF4flt, t120 [T
IJZ minute], 0. Flow rate 120 (d/min), pressure 0.2
The fluorination treatment was performed under conditions of (Torr). next,
Place these 5 samples in an oven and heat at 220 LC) for 3
Post-baked for 0 minutes.

In addition, for the remaining five samples, the upper limit of flAk- that can maintain the profile of the resist pattern 14 is
Baking treatment was performed at 140 (t) for 30 minutes.

The samples obtained by the above two methods were placed at the electrode (lower electrode) 3 in the reactive ion etching apparatus shown in FIG.
Place it on top, CF, flow rate 20Ls#/min], H takashi flow rate 3
When the etching rate of the thermal oxide film 12 was measured under conditions of 0 (d/min) and a pressure of 0.1 (Torr) while changing the applied high-frequency power, the results shown in FIG. 4 were obtained. That is, For all samples, the etching rate increased as the applied high-frequency power increased.
For samples made by normal processes, high frequency power of 60
It was found that at 0 [W], the resist 13 was damaged and wrinkles became noticeable.

On the other hand, in the sample subjected to the fluorination treatment and the baking treatment at 220 E'), the high frequency power was 1
However, the resist 13 was not damaged at all, and a good etching pattern could be obtained. Therefore, it has become possible to increase the etching rate of the practical thermal oxide film (SIO) 12 from about 1500 (A/min) to about 3000 [A/min].

Note that the present invention is not limited to the embodiments described above. For example, the conditions such as gas flow rate and pressure in the fluorination treatment, and the temperature conditions (160 r or more) in the post-baking treatment may be adjusted as appropriate depending on the specification number. Furthermore, the gas used for the fluorination treatment was CFs and 0.
It is not limited to a mixed gas with fluorine radicals, but any gas t) that generates fluorine radicals may be used. Furthermore, the resist may be of a negative type instead of a positive type.

Furthermore, plasma equipment that generates fluorine radicals
It is possible to use not only a parallel plate type but also a cylindrical type. Furthermore, it goes without saying that the film to be processed is not limited to #oxidized #(SiOl), but can be applied to various other films. In addition, various modifications can be made without departing from the gist of the present invention.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram showing the general configuration of a reactive ion etching device, FIG. 2 is a schematic diagram showing the direct R11L position distribution in the device, and FIGS. FIG. 4 is a cross-sectional view showing the pattern forming process according to the embodiment, and a characteristic diagram showing the relationship between the applied high frequency power and the etching rate (1). 1... Vacuum chamber, 2, 3... Electrode, 4... Sample, 5... High frequency electromagnetic fishing, 6... Matching box, 11... 81 substrate, 12... Thermal oxide film (processed @
), 13... resist, 14... resist pattern. Applicant's representative Patent attorney Takehiko Suzue Figure 1 Figure 2 Figure 3 Takagawa Mekuryoku□□□〕

Claims (1)

[Claims] <11 After exposing a resist coated on a film to be processed to a desired pattern, the resist is exposed to form a resist pattern, and then the resist surface is fluorinated with fluorine radicals. , then apply the above resist to 160 (
C) A pattern forming method that eliminates post-baking at a temperature above and then selectively etching the film to be processed using the resist as a mask using a reactive ion etching method. (2) Special feature 1Ffli!, characterized in that an 8tO film is used as the Roe coating film. The pattern forming method according to item 1. (3) The pattern forming method according to claim 1, item 6, wherein, as the means for the fluorination treatment, the resist is treated with a mixed gas plasma of CF and O2.