JPH03291931A - Resistless patterning method - Google Patents

Abstract

PURPOSE:To reduce the number of process steps, improve throughput, and decrease industrial waste like developing liquid, by coating a substratum with a specified film for patterning, projecting specified light having spacial intensity distribution, and selectively etching and eliminating only the film part which is irradiated or only the film part which is not irradiated. CONSTITUTION:A substratum 1 is coated with a film 2 for patterning wherein the etching rate is changed by irradiation of specified light and the absorption coefficient of said light is 0.05-5mum<-1>. After specified light 5 having spacial intensity distribution is projected on the film 2, only the film part 3 which is irradiated or only the film part 2 which is not irradiated is selectively etched and eliminated. For example, by using a parallel plane type plasma CVD system, a 500nm thick SiN film 2 is formed on an Si substrate 1, and irradiated with KrF excimer laser light 5, via a mask 4 wherein a Cr film pattern is formed on a synthetic quartz plate. Then by using 1:7 buffer hydrofluoric acid as etching solution, the part 2 which is not irradiated is selectively etched and eliminated, thereby forming an SiN film pattern.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a patterning method used for manufacturing semiconductor devices, electronic circuits, etc., and particularly to a patterning method that does not use a resist.

[Prior Art] Photoresists have conventionally been used in patterning methods. A method for patterning a film using a photoresist is performed, for example, as follows.

(i) Forming a film over the entire surface of the coated substrate.

(ii) Coating with photoresist.

(iii) Soft bake at 70-100°C.

(iv) An exposure device irradiates the photoresist with light having a spatial intensity distribution.

(V) Selectively remove the irradiated or unirradiated portions of the photoresist and develop.

(vi) Hard bake at 120-170°C.

(vri) Pattern the film using an etching device.

(viii) Remove the photoresist using an ashing device.

(Problems to be Solved by the Invention) However, the above conventional patterning method using a photoresist has the following problems: (i) The number of steps is large, and throughput cannot be increased.

(ii) A large amount of developer, etc., which becomes industrial waste, is required.

There were drawbacks such as.

The present invention was made in view of the problems with the conventional patterning method using a photoresist, and provides a new method for patterning without using a photoresist.

[Means to solve the problem]

In the present invention, the etching rate changes by irradiating a predetermined light onto the substrate, and the absorption coefficient for the etching tip is 0.05 to 5.
a step of coating the structure with a patterning film, a step of irradiating the structure with a predetermined light having a spatial intensity distribution, and a step of selectively etching away only the irradiated or unirradiated portions of the structure. According to the present invention, the number of steps is significantly reduced, thereby improving throughput, and since it does not include a photoresist development step, industrial waste such as developer is reduced. be able to.

In the present invention, a film is etched with good selectivity without using a photoresist. First, the film that can be used to achieve this purpose has a certain etching rate ratio before and after irradiation with light. is large, preferably 1
It has a performance that is 0 times or more, more preferably 100 times or more, and may increase or decrease before and after irradiation.

Here, in the present invention, the expression that the etching rate changes due to irradiation with a predetermined light means that the etching rate in the etching process changes in the light irradiated area as a direct result of the irradiation with light. Since the etching speed varies depending on the etching method and conditions, it means a change in speed in an optimal etching method based on a conventional method. Further, the predetermined light irradiation is light irradiation under conditions that can increase the etching rate ratio of the film, and the wavelength, irradiation energy, etc. may be adjusted as appropriate depending on the material of the film used, film formation conditions, etc. Just set it.

Usually, the light has a wavelength of about 180 to 500 nm. below,
When referring to light irradiation or light, it means under the above-mentioned predetermined conditions.

Next, the second performance required of the film is an appropriate absorption coefficient, preferably 0.05 to 5, in order for the film to effectively absorb light.
It is to have μl11-1. However, if the absorption coefficient decreases due to light irradiation, the absorption coefficient after light irradiation is 0.0.
The absorption coefficient before light irradiation may be 5 or more as long as it is 5 to 5 μm −1 .

Membrane materials that can be used in the present invention include:
Any item may be used as long as it satisfies the above requirements, for example, A.
Although it is possible to use a metal film made of T, W, etc., it is possible to use a film with a higher etching speed ratio, such as a semiconductor such as amorphous or crystalline, or an insulator such as amorphous or crystalline. SEN, 5i, which satisfies the above requirements for ultraviolet light in the wavelength range of 248 to 436 nm in the device
Insulator films such as N2 and semiconductor films such as Si and GaAs have excellent practicality, and both have a reduced etching rate and absorption coefficient when irradiated with light.

Note that the etching speed is also affected by the density of the film, but if the etching speed decreases due to light irradiation, the film does not need to be dense before light irradiation, and the etching speed ratio with that after light irradiation should be considered. In fact, in many cases it is more effective to be less precise. For this reason, for example, the substrate temperature during film formation may be low, and room temperature is often appropriate.

The reason why the etching rate of a film made of the above-mentioned film material changes due to light irradiation, and sometimes the absorption coefficient changes, is that when the etching rate decreases, incomplete bonds and hydrogen in the film are destroyed by light irradiation. As a result, the membrane becomes denser.
Additionally, when the etching rate increases, the bonded state transitions to a non-bonded state due to light irradiation, and as a result, the bond is broken.
This is thought to be due to a change in the etching rate or a change in the absorption coefficient, and the suitable wavelength band of light is determined by incomplete bonding and electron transition energy of hydrogen.

As long as the above conditions are met, any film forming method such as thermal CVD, plasma CVD, optical CVD, sputtering, vapor deposition, etc. may be used to form the above film, but it is possible to use plasma CVD at room temperature. It is optimal because it can easily form a film with appropriate density, appropriate etching rate, and appropriate absorption coefficient. In addition, the thickness of the film is 0.1 to 1μ
About m is sufficient.

Next, after forming a film that satisfies the above conditions, by irradiating it with light having a desired spatial intensity distribution using a conventional method, the etching speed of the light-irradiated area and the non-irradiated area is greatly changed, and then etching is performed. Patterning can be formed by selectively removing the light irradiated portion or the non-irradiated portion.

A mask is preferably used to give the light a spatial intensity distribution, and this can be done by contact exposure, reduced projection exposure, or the like. Etching may be wet or dry etching as long as the etching speed ratio before and after light irradiation is large, for example, 10 times or more.

For example, etching may be performed using buffered hydrofluoric acid or chemical dry etching.

Further, light sources that can be used for light irradiation include a KrF excimer laser, a high-pressure mercury lamp, etc., and any optical system that incorporates a suitable lens or the like and can irradiate a parallel beam can be used as the light irradiation means. Incidentally, the light irradiation energy may be sufficient to achieve a desired etching rate, but it is usually 0.05 to 2 W/cm for about 210 to 200 minutes on the substrate.

As described above, in the method of the present invention, the number of steps required for patterning is 3, which is less than half of that when using conventional photoresists, improving throughput, and since no developing step is required, industrial waste such as developer is reduced. can be significantly reduced.

(Example) An example in which the present invention is used for patterning a SiN film will be described below with reference to FIG.

In FIG. 1, 1 is a Si substrate, 2 is a photo-irradiated SiN film formed by plasma CVD, 3 is a photo-irradiated SiN layer,
4 is a mask, and 5 is a KrF excimer laser beam.

(a) shows the process of forming a SiN film. 5iH42 (1
/NH* 50/N2200 sccm, pressure 0.2
The film was formed for 10 minutes under the conditions of Torr% RF power of 300 W and substrate temperature of room temperature to form a 500 nm thick SiN film.

(b) shows a step of irradiating light with a spatial intensity distribution. A MrF excimer laser was used as a light source, and a parallel light beam uniform over a large area was formed by an optical system including a fly's eye lens and a collimator lens. The mask used was a synthetic quartz plate with a Cr film pattern formed thereon, with a minimum pattern width of 1 μm, and was brought into close contact with the substrate. Illuminance on the board is 0.5W/cm
The irradiation was carried out for 45 minutes.The absorption coefficient before the light irradiation was 6 or more, but it decreased to 1.8 after the light irradiation.

Furthermore, after irradiation, the film thickness decreased by about 20%, probably due to densification (see Figure 2).

(c) shows a step of removing the unirradiated portion of the film by etching. Etching was performed for 30 seconds using 1N buffered hydrofluoric acid as an etching solution. The etching speed is 90 nm/min in the light irradiated area and 11100 n/min in the non-irradiated area.
n, and there was a difference of more than one digit. As a result, the minimum line width is 1
A μm SiN film pattern was formed. That is, patterning could be successfully completed in just three steps.

〔Effect of the invention〕

As mentioned above, according to the patterning method of the present invention that does not use a photoresist, the number of patterning steps is greatly reduced, resulting in improved throughput. It has the effect of reducing the amount of industrial waste. Further, since each process such as forming a film used for patterning can be easily performed, the present invention is extremely useful in practice in patterning processes in the manufacture of semiconductor elements, electronic circuits, and the like.

[Brief explanation of drawings]

FIG. 1 is a diagram showing the flow of the steps of the present invention carried out in Examples, in which (a) is a step of forming a film on a substrate, and (b) is a step of irradiating light with a spatial intensity distribution. , (c) shows a step of selectively etching away only the irradiated or non-irradiated portions of the film. FIG. 2 shows the absorption spectra of the SiN film described in the example before and after light irradiation. 1 is a Si substrate, 2 is a photoirradiated SiN film formed by plasma CVD, 3 is a photoirradiated SiN layer, 4 is a mask, and 5 is a KrF excimer laser beam.

Claims (1)

[Claims] 1. The etching rate changes upon irradiation of a predetermined light onto the substrate, and the absorption coefficient for the light is 0.05 to 5 μm^
-^1 A step of coating the patterning film, a step of irradiating the film with a predetermined light having a spatial intensity distribution,
and a step of selectively etching away only the irradiated or non-irradiated portions of the film. 2. The resistless patterning method according to claim 1, wherein the film is made of a semiconductor or an insulator. 3. The resistorless patterning method according to claim 2, wherein the semiconductor or insulator is crystalline or amorphous.