JPH01153734A - Polymer readily processable with light - Google Patents

Abstract

PURPOSE:To provide the title polymer composed of an aromatic poly(ether sulfone) or poly(arylate), etchable with light or heat in high efficiency after exposure to ultraviolet radiation and useful as an organic polymer base for optical recording. CONSTITUTION:The objective polymer readily processable with light is composed of (A) a poly(ether sulfone) having a structure of formula I, etc., and derived from 4,4'-dichlorodiphenyl sulfone or (B) a poly(arylate) having a structure of formula II, etc., and composed of an aromatic dicarboxylic acid and a bisphenol. The polymer A or B or a composition produced by blending the polymer with other polymer [e.g. poly(methyl methacrylate)] as a photosensitizer is subjected to photo-processing with ultraviolet radiation having a wavelength of <=380nm in vacuum, in an inert gas or in air at normal temperature-100 deg.C.

Description

[Detailed Description of the Invention] [Object of the Invention and Field of Application] The present invention relates to a polymer that is characterized by being easily photoprocessed by ultraviolet rays, and a polymer that can be efficiently etched by light or heat in a portion irradiated with ultraviolet rays. 1. Photoresists for developmentless dry etching used in semiconductor integrated circuits, or sensitizers for photoresists.

2. Organic polymer base material for optical recording such as read-only memory (ROM) and write-once type.

3. Organic polymer material for microporous membranes.

4. Optical element materials such as diffraction gratings.

5. The aim is to provide related industries with polymeric materials that can be used as different photoprocessable synthetic resins (for drilling, cutting, surface modification, etc.).

[Relationship with prior art] Focusing on the high brightness and short wavelength properties of the excimer laser, an attempt was made to use an excimer laser to etch poly(methyl methacrylate), which is said to have the highest resolution among polymers, as part of physical and chemical research. Same village, Toyota, Namba (Laser Research Vol. 8゜11k16.941 (Showa 55)
(2005)), and it was quickly established that excimer lasers are extremely effective as light sources for photoetching, photolithography, etc.

Afterwards, apart from the villagers, R.3riniVasan of International Business Machines Corporation (IBM)
process+nc+ and Diagno
sticks”5prinoer 5eries i
n Chemical Physics 3
9゜Springer-■erlarg, Berl
(In, 1984) found that when a polymer film is irradiated with a short-pulse far-UV excimer laser, etching to a depth of 1000 nm or more occurs instantaneously photochemically. blative P
Hot.

o ecompos + t on ).

R. Srinivsan et al., in their early research on ablative decomposition using a 193 nm laser, found that the main mechanism of decomposition was photochemical etching, that is, direct electron excitation by photons that caused chemical bonding of polymers on the irradiated surface. He proposed a mechanism in which the wire would be disconnected. However, when using an excimer laser with a wavelength longer than 193 nm, the sample may be a polymer with strong absorption in the ultraviolet region, such as poly(imide), poly(ethylene terephthalate), poly(carbonate), etc. It is acknowledged that even if ... is used, the melt-repellent decomposition of these polymers mainly results in etching via thermal decomposition (for example, J. Polym, Sct.

Polym, Chem, Ed, Vol, 22,
2601-2609 (1984); lyjacro
molecules', VOl, 19, No, 3
916-921 (1986)'').For melt-repellent decomposition, (1)' melt-repellent decomposition via thermal decomposition.

(2) Photochemical ablation decomposition.

(3) Therally-assisted (or
It is said that there are three melt-repellent decomposition processes: activated) photoprocess).

It has since been experimentally confirmed by other researchers that when optical etching is performed using an excimer laser with a long wavelength of 249 rv or more, thermal decomposition is likely to occur.

In the ultraviolet region, the distance of light transmission into the interior of the polymer is short, and the volume in which light is absorbed is small, so local high temperatures are likely to occur.
However, since thermal diffusion can be ignored for an extremely short period of time, even if optical processing is mainly thermal processing, it is possible to perform processing with a certain degree of precision. However, in machining that requires high precision, it is desirable to avoid etching due to thermal decomposition as much as possible.

For example, when the same polymer is irradiated with excimer lasers of different wavelengths, it can be assumed that thermal ablation decomposition occurs more easily when etching with longer wavelengths, but photoetching with longer wavelengths is more likely than with short wavelengths. In this case, the product produced has a high proportion of polymer products, the inner walls of the holes created by etching are obviously rough, and the emitted product contains a large amount of fused granular powder, so the granular powder It is said that micro-pattern stains and lens fogging are likely to occur due to the scattering of particles.

Increasing the rate of photodecomposition in ablative decomposition is extremely important for precision machining as described above, but this requires not only the use of a short wavelength laser as described above, but also the use of a low repetition frequency (usually 501- This can be achieved to some extent by avoiding heat accumulation, such as by using a frequency below IZ (in some cases below IHz). However, it is fundamentally limited by the characteristics of the polymer to be irradiated. For example, poly(methyl methacrylate) cannot be subjected to ablation photolysis using a 308r+n+ excimer laser, but etching only occurs due to thermal decomposition. That is, polymers that only undergo photodecomposition at short wavelengths can be etched by thermal decomposition in the long wavelength range, but cannot be etched photochemically.

On the other hand, polymers that can be photochemically processed in the long wavelength ultraviolet region can be easily etched by repellent photolysis even at short wavelengths. Furthermore, such polymers can be thermally decomposed by ablative repellency by changing the irradiation conditions during photochemical processing. Therefore, when processing with light, the processing range can be widened.

From this point of view, the present invention was arrived at as a result of intensive searches for polymers that are susceptible to photorepellent decomposition even at long wavelengths in the ultraviolet region.

[Structure of the Invention] Polymers that are easily photochemically fused and decomposed by ultraviolet rays and that can be thermally photoprocessed include polymers that contain a polycyclic fused aromatic compound in most of the main chain of the polymer. Molecules (patent application 1986-
In addition to monocyclic aromatic polymers, aromatic poly(ether sulfone) and poly(
It was found that there are polymers containing arylate). Compared to other polymers, these polymers are easily photochemically processed not only by ultraviolet lasers with short wavelengths but also by lasers with wavelengths longer than 200 nm, and they are also thermally repellent if conditions are appropriately selected. We discovered that it is possible to perform decomposition.

Furthermore, as shown in the examples, these polymers can also be etched by ultraviolet rays emitted from discharge lamps, which have much lower output and brightness than excimer lasers. In this case: (1) Films of these polymers decrease in film thickness at a measurable rate.

(2) The rate at which the film thickness decreases is significantly faster than that of other polymers.

Conventionally, a huge amount of research has been conducted on many polymers because weather resistance is considered to be one of the practical properties of polymers due to changes in their physical properties (particularly reduction in elongation) due to ultraviolet irradiation. However, there are almost no reports that investigate the etching properties of resins other than photodegradable resins and photosensitive resins, especially heat-resistant polymers, and changes in the irradiated surface. Slightly p, 31
Ais et al. report LJ, Appl, polyn+,
Sci, Vol, 17°1895 (1973)
)...Poly(ethylene terephthalate) is simply volatilized and lost by light. p, 31
AIS etc. place a 300-mesh wire mesh on a poly(ethylene terephthalate) film and irradiates it with ultraviolet rays for i, ooo hours, causing the film surface to dent in the irradiated area.
It is acknowledged that the poly(ethylene terephthalate) is slightly etched by light as the wire mesh pattern is transferred onto the film.

In contrast to this prior known knowledge, the present inventors have discovered that the polymer targeted by the present invention is etched by ultraviolet light much faster than poly(ethylene terephthalate).

[Summary of the invention] Aromatic poly(ether sulfone) that is the object of the present invention
is a commercial product manufactured using 4,4'-dichlorodiphenylsulfone as a raw material, and has the following structure. Poly(ether sulfones) having other structures are also commercially available and are included in the target polymers of the present invention.

Poly(arylate) is a polymer consisting of aromatic dicarboxylic acid and bisphenol, and those having the structural formula are available on the market. However, some or all of bisphenol is bisphenol-A instead of bisphenol-A.
Even if it is 8, there is no problem. Furthermore, a poly(arylate) using hydroxy aromatic carboxylic acid as a starting material instead of aromatic dicarboxylic acid and aromatic diol may be used.

The poly(ether sulfones) and poly(arylates) targeted by the present invention include those having one or more substituents on their benzene rings. Further, the polymer may be a crystalline or amorphous polymer. In the case of a crystalline polymer, it may be photo-processed in an unstretched state, or it may be stretched and oriented and used for light irradiation. Moreover, there is no problem even if the film is subjected to optical processing without being stretched, then stretched and oriented for subsequent use. Furthermore, it can be copolymerized with other polymers.

Blend or block polymerized compositions also contain aromatic poly(ether sulfone) in the backbone of most of the main chain of the polymer.
Or, as long as it contains poly(arylate), it is included within the scope of the polymer of the present invention.

An interesting example of blending is blending the subject polymer of the present invention with a polymer that is difficult to photochemically decompose, such as poly(methyl methacrylate). May be used as a sensitizer.

In this case, the blending amount ranges from several percent to several tens of percent to sufficiently exhibit the effect as a sensitizer. Therefore, in the case where the polymer targeted by the present invention is used as a sensitizer, even if the majority of the polymer is composed of a polymer not targeted by the present invention, it does not fall within the scope of the claims of the present invention. cannot be interpreted as such.

Most of the ultraviolet light used for irradiation is 380℃m.
Any ultraviolet light having a shorter wavelength may be used, and there is no problem even if it is light including visible light. Industrially, discharge lamps (high-pressure mercury lamps, carbon arcs, mercury resonance lamps, etc.) can be used. A more desirable light source is a pulse discharge tube containing argon or xenon, which can emit a large amount of light (for example, 10 to 40 KJ/pulse) over a wide area in a short period of time.

Furthermore, efficient optical processing can be performed by using a combination of an ultraviolet laser and the target polymer of the present invention. These ultraviolet lasers include XeF (wavelength 350nl)
, N2 (wavelength 337 nm), Xe Cj
(wavelength 30801), YAG (1/4 wavelength (4
Double harmonic) 256n+++ >, Kr F (wavelength 2
48nm), ArF (wavelength 193nm),
Using an F2 (wavelength: 157nlIl) Nohoka dye laser as a light source, optical processing such as drilling, cutting, 9 surface layer processing, and 9 surface modification can be performed.

Prior to photoprocessing, a photosensitizer such as a dye or a catalyst may be added to the target polymer of the present invention, and the polymer may be irradiated with light. Optical processing may be performed in any atmosphere such as vacuum, inert gas, or air. Optical processing humidity generally ranges from room temperature to 10
The temperature may be within the range of 0° C., but if thermal processing is acceptable, the temperature may be further increased and the light irradiated.

When performing optical processing, if precision processing is required, almost the same level of fine processing can be achieved by combining technology, processes, and equipment such as photomasks and wafer exposure aligners. In this case, products with significantly higher added value or with significantly higher functionality can be produced.

Next, examples and comparative examples of the present invention will be described.

Example-1 Photo-etching using a discharge lamp As a light source, a near-ultraviolet transmitting filter (450 nI1) was used as a light source.
1-2900m) A 1.5KW water-cooled special discharge lamp was used. Its peak wavelength was 365°Cm.

The irradiated film sample was placed on a rotating table 150° C. away from the light source and rotated 5 times per hour to ensure uniform irradiation.

In this case, the effective irradiation area was 1oo=X1oo, and the degree of symmetry was 90% or more. When I measured the irradiation energy on the film surface with a UV digital meter, it was 365r.
27m W/sea. In order to avoid thermal processing, irradiation was carried out for 100 hours by blowing cold air onto the sample surface to keep the sample temperature below 80°C.

After irradiation, the thickness of the sample film was measured to determine the decrease in film thickness.

A commercially available film sample was used. Poly(ether proboscis sulfone) is VICTREX (trade name) film grade, poly(arylate) is U polymer manufactured by Unitika Co., Ltd.
A sheet of 8000 (trade name) was obtained and used for testing. The test results are shown in the table below.

Table 1 Change in film thickness due to ultraviolet irradiation The decrease in film thickness after 100 hours of irradiation is twice or 8 times, respectively, compared to the poly(ethylene terephthalate) shown in Comparative Example-1.
It's being etched twice as fast.

Comparative Example-1 The main polymers other than photoresist used as irradiation samples in the report by R. Srinivsan et al. are poly(methyl methacrylate), poly(imide), poly(carbonate), and poly(ethylene terephthalate). It is.

A test similar to Example 1 was conducted using commercially available sheets or films of these resins. The results are shown in Table 2.

Table 2 Changes in film thickness due to ultraviolet irradiation Poly(ethylene terephthalate) from the above table.

Although poly(carbonate) is slightly etched by light, the film thickness of poly(methyl methacrylate) and poly(imide) does not change at all even after 100 hours of irradiation.

Furthermore, a test was conducted to confirm whether light absorption is a condition for photoetching to occur. Since monocyclic aromatic polymers have ultraviolet absorption based on benzene rings, they were tested using the same method and conditions as in Example-1.

The irradiated samples were commercially available poly(ether/ether/ketone), poly(ether/imide), poly(phenylene sulfide), and poly(sulfone) and were tested. After irradiation, the elongation of all samples decreased significantly, and poly(sulfone) was particularly brittle. However, the thickness of the film did not change before and after irradiation in any of the samples, and no evidence of photoetching was observed.

Among these, poly(sulfone) has a resin structure synthesized from 2,2-bis-(4-hydroxyphenyl)propane and 4,4'-dichlorodiphenylsulfone, and poly(ether) It is a resin in the same family as sulfone).

Poly(sulfone) has high heat resistance, but
Weather resistance is low due to absorption in the vicinity, and it is easily susceptible to chemical changes and photooxidative decomposition due to ultraviolet rays, which lowers the intrinsic viscosity of the polymer and generates GO and COz, which tends to cause a decrease in molecular weight. known (B.

D, Gen5ner, P, G, Kellehe
r, J, Appl.

Polym, Sci, Vol. 12, 1199 (
1968) ). Therefore, it was assumed that poly(sulfone) mainly changes into a volatile substance when exposed to light and is susceptible to etching. However, tests have shown that poly(sulfone) is similar to the same family of polymers, poly(ether sulfone).
It was found that m-, whose absorption increases rapidly below -33OnIll, makes it difficult to be etched by light, but rather causes embrittlement mainly due to irradiation. From the above, even though the necessary condition for photoetching to occur is that the irradiated polymer has strong absorption in the ultraviolet region, it cannot be said that photoetching will always occur, and rather, embrittlement will predominately occur. It turns out that there are cases where this happens.

It has also been found that even among monocyclic aromatic polymers that absorb in the ultraviolet region, there are relatively few polymers that are easily etched by light, and these are limited to those with a limited structure.

Patent applicant Teijin Yuka Co., Ltd.
Company Japan Electric Co., Ltd.
Ceremony in front of Patent Attorney 1) Jun Haku procedural amendment September 2nd, 1988

Claims (1)

[Claims] A method of photo-processing a polymer made of aromatic poly(ether sulfone) or poly(arylate) using ultraviolet light of 380 nm or less.