JPS63237418A - Hardening of resist - Google Patents

Abstract

PURPOSE:To prevent the deformation of a resist pattern during an etching process by a method wherein, in a curing operation using ultraviolet rays at a resist process, a low-boiling-point component in a resist is removed by a reduced pressure method or a reduced-pressure heating method prior to the curing operation using the ultraviolet rays so that the effective curing operation can be executed. CONSTITUTION:A patterned wafer 11 is placed on a hot plate 12 inside a reduced-pressure chamber 13. The temperature of the hot plate 12 is set at about 100 deg.C. Then, an exhaust value 14 is opened; the reduced-pressure chamber 13 is evacuated and is kept at about 10 Torr for a few minutes. Then, the exhaust valve 14 is closed; a leakage valve 15 is opened; the chamber is returned to an atmospheric pressure by using N2. After a heat treatment under a reduced pressure, the wafer 11 is placed on a hot plate 16 and is irradiated with the light hnu by a deep UV lamp 17 whose light has a wavelength range of 200 nm-600 nm for several minutes. When the wafer 11 which has been treated in the above way is heated on the hot plate at 200 deg.c, the thermal deformation of a resist pattern is never caused.

Description

[Detailed Description of the Invention] [Summary] Ultraviolet curing ('UVcur) in resist process
In e), before UV-curing, low-boiling components in the resist are removed by reduced pressure or reduced-pressure heating to perform effective UV-curing and prevent deformation of the resist pattern during etching.

[Industrial application field]

The present invention relates to a method of resist hardening, and more particularly to a method of lv-curing a resist to prevent deformation during etching of patterns in a patterned, exposed and developed resist.

[Conventional technology]

When writing in a semiconductor process, a resist pattern is formed on a semiconductor substrate, and then the substrate is etched by dry etching or the like using the resist pattern as a mask to form a pattern. For example, to form an oxide film with some pattern on the surface of a semiconductor substrate, an oxide film is formed on the entire surface of the substrate, a resist is applied on top of the oxide film, and then the resist is applied through a mask with the desired pattern formed. When exposed and developed, a resist pattern with a desired pattern can be obtained. When the oxide film is etched using this resist pattern as a mask, an oxide film with a desired pattern can be obtained. Recently, there has been a demand for finer patterns in order to increase the degree of integration of semiconductor integrated circuits, and to meet this demand, dry etching has been used instead of conventional wet etching. For example, etching is performed by generating plasma in a vacuum. Reactive ion etching (RIE) is used to perform this.

In such dry etching, the temperature is 100 to 130°C.
There is a problem in that a resist pattern serving as a mask is deformed by this heat, and an accurate resist pattern is not maintained and the pattern formed on the substrate is no longer accurate.

Therefore, in order to prevent the deformation of the resist pattern due to heat as described above, deep UV curing is used to crosslink the resin in the resist, increase its molecular weight, and improve the heat resistance of the resist. Research is being carried out on ways to prevent this deformation.

The conventional deep UV-curing method is shown in FIG.
Deep tlV
Dee of wavelength 200'600 r+m with lamp 23
P LIV light 2 beam combination 4 wafer 21 is irradiated. In some cases, the temperature of the hot plate 22 may be gradually increased. In FIG. 2, the resist coated on the wafer 21 is not shown, and the lamp 23 is, for example, an Xe-1g lamp (illuminance 25, 0 mW/cm2, wavelength 350 nm).

[Problem that the invention seeks to solve]

The inventor of the present invention confirmed the following fact in the process of researching conventional UV-curing treatment.

If H,0 is contained in the resist to be UV-cured, the crosslinking reaction will be hindered, making it impossible to perform efficient resist hardening. Furthermore, if the resist is heated to 100 DEG C. or higher in order to perform UV-curing treatment without evaporating 11□0, which interferes with such a crosslinking reaction, the following problem occurs. That is, when a resist resin with a low molecular weight is used to improve resolution, the heat resistance of the resist resin becomes low, so that heating at 100° C. or higher causes thermal flow in the resist and deforms the pattern. Furthermore, even with a resist resin having a normal molecular weight, when the coating film was thick, the resist pattern was deposited thickly (and the pattern was likely to collapse), causing destruction of the resist pattern.

Furthermore, since the ultraviolet light source used in the UV-cure treatment includes the wavelength at which the resist is sensitive, naphthoquinonediazide, the photosensitizer, decomposes and N2 is generated. On the other hand, the photocrosslinking reaction proceeds from the resist surface due to the photocrosslinking reaction promoting wavelength (230 to 400 nIII in the case of novolak resin) contained in the ultraviolet light source.

In this way, the N2 (2) generated as described above accumulates inside the resist pattern that has been hardened by the photo-crosslinking reaction that proceeds from the resist surface, and when it accumulates in excess, it pierces through the hardened portion of the resist surface and destroys the resist pattern. Resulting in. In addition, [after JV-cure treatment, further heating (
120℃ or higher), the residual solvent in the resist (
Ethylene glycol ethyl ether acetate (e.g., ethylene glycol ethyl ether acetate) evaporates above its boiling point (boiling point: 145°C) and breaks through the hardened portion of the resist surface, destroying the resist pattern, similar to when N2 accumulates. .

The present invention was created in view of these points, and it is an object of the present invention to provide an improved method for resist curing.

Means for Solving Problem c] Figures 1+8) and (b) are diagrams explaining the embodiment of the present invention,
In the figure, 11 is a wafer on which a resist is applied;
2 is a hot plate, 13 is a vacuum chamber in which the wafer and hot plate are stored, 14 is an exhaust valve, 15 is a leak valve, 16 is a hot plate, and 17 is a DCep.
It is a UV lamp.

In the present invention, DeepU shown in FIG.
Before V-curing, the wafer 11 coated with resist is placed in a vacuum state in a vacuum chamber 13, and then D-curing is performed.
Perform deep UV-cure with eepυ syrup 17.

[Effect]

When the resist is placed under reduced pressure as described above, low-boiling components (mainly 11
10), thereby removing Deep UV-
Crosslinking of the photosensitive resin is promoted during the curing stage, increasing the heat resistance of the resist and preventing deformation of the resist pattern during dry etching.

〔Example〕

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

First, I will explain the results of experiments conducted by the present inventor.
As shown in FIG. 1(a), a wafer 11 with a resist pattern formed thereon, that is, a resist pattern that has been coated, exposed, and developed, is placed in a vacuum chamber 13 and evacuated. A vacuum was maintained. At this time, less than 760 Torr is sufficient, especially 50 Torr.
It is even more effective if it is less than Torr. Furthermore, it is more effective to heat the wafer 11 by placing it on a hot plate 12 or by other methods while maintaining the reduced pressure as shown in FIG. 1 (al). Eep IJV-cure was performed in the same manner as above.

The reason why deep UV-curing is performed after reduced pressure or reduced-pressure heat treatment is to remove low-boiling point components (mainly H, O, etc.) in the resist that prevent crosslinking of the resin in deep UV-curing at a low temperature. Although it is possible to remove the low boiling point component by heating alone, the resist pattern is thermally deformed at a temperature below the removable temperature, so the heating method cannot be used.

Therefore, the above-mentioned method of maintaining reduced pressure was adopted, and the rationale for this method is thought to be as follows. The resist contains a photosensitizer shown by the chemical formula, and the main body of this photosensitizer, NQD (naphthoquinone diazide), is

When exposed to light in an N2 atmosphere, ketene with the structure 01g is obtained. During development after exposure of the resist, N20 is taken in and becomes indenecarboxylic acid with the structure of ketene. This substance does not bond with other substances in any part of it, and therefore does not bond with resin and crosslink to increase heat resistance, and recent high-resolution resists contain large amounts of this substance.

Therefore, in the present invention, ketene is maintained in a reduced pressure state so as not to incorporate HLO, and the ketene is bonded to the resin to mediate crosslinking as expressed by the following, thereby improving the heat resistance of the resist. In other words, by reducing the pressure or holding the resin under reduced pressure by heating, low-boiling components that prevent crosslinking of the resin are removed, so that subsequent resist hardening by Deep Uv-cure can be effectively performed.

In one embodiment of the invention, TSMl? A wafer 11 patterned with -8800 resist (Tokyo Ohka) is placed on a hot plate 12 in a vacuum chamber 13 .

The temperature of the hot plate 12 is set to a high temperature (approximately 100° C.) so that the resist pattern is not thermally deformed. Next, open the exhaust valve 14 and open the decompression chamber 13.
Evacuate the inside with a rotary pump, etc. (not shown), and reduce to 10
Hold at about Torr for several minutes. Next, exhaust valve 14
, open the leak valve 15 and return to atmospheric pressure with N2.

After the reduced pressure heat treatment, the wafer 11 is placed on the hot plate 6, and a deep beam with a wavelength of 200 nm to 600 nm is placed
Light hv is irradiated with the UV lamp 17 for several minutes. The temperature of the hot play area 6 at this time is set to a high temperature (about 100° C.) so that the resist pattern is not thermally deformed.

The wafer 11 subjected to the above treatment was heated at 200° C. on a 7) plate, but there was no thermal rhombus in the resist pattern. However, in the case where the conventional deep UV-curing was performed without applying the reduced pressure heat treatment, the resist pattern was thermally deformed. Furthermore, when dry etching was performed, the wafers subjected to the above treatment were able to form patterns as designed, whereas conventional Deep UV-
The one that was cured could not form the pattern as designed.

It is also possible to hold the resist under reduced pressure in the iJf chamber 13 and then perform deep UV-curing in the same chamber, but according to this method, for each wafer, the chamber 13 is brought to atmospheric pressure and the wafer is The wafer is placed in a chamber, then the chamber is evacuated for deep LIV-curing, the vacuum is leaked, and the wafer is taken out.
The process described above must then be repeated for a new wafer, increasing processing time and reducing throughput.

However, according to the method of the present invention, for example, if a plurality of wafers are stored in a cassette, the cassette is placed in a chamber, the resist is maintained under reduced pressure, and after this process, deep UV-curing is performed for each wafer. This has the advantage that the processing time is shortened and the device does not need to be complicated.

〔Effect of the invention〕

As described above, according to the present invention, deformation of a patterned resist during etching is prevented, which is effective in improving the reliability of semiconductor devices, and is also effective in increasing manufacturing yield.

[Brief explanation of drawings]

Figure 1 (al and (bl) are diagrams explaining the method of the present invention, Figure 2
The figure shows a conventional U-secure method. In FIG. 1, 11 is a wafer, 12 is a hot plate, 13 is a vacuum chamber, 14 is an exhaust valve, 15 is a leak valve, 16 is a real play 1., and 17 is a deep tlV lamp. Agent: Moto Kuki, Patent Attorney: Yoshiyuki Osuga, Patent Attorney: Figure 2 shows the UV-cure of rice.

Claims (4)

[Claims] (1) The patterned resist on the wafer (11) is placed in a reduced pressure state in a reduced pressure chamber (13), and then the wafer (11) is irradiated with ultraviolet rays in the atmosphere to cure the resist. Resist hardening method. The method according to claim 1, characterized in that (2) the wafer (11) is heated under reduced pressure in a reduced pressure chamber (13). (3) A method according to claim 1, characterized in that the wafer (11) is heated by irradiation with ultraviolet rays. (4) The reduced pressure state is less than atmospheric pressure (760 Torr), and the reduced pressure heating is performed at a pressure of less than 760 Torr and a temperature of 20° C. or more.
The method described in section.