JPH0798870B2 - Polymer optical processing method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention and Field of Application] The present invention relates to a polymer which is characterized by being easily photo-processed by ultraviolet rays, and a portion irradiated with ultraviolet rays is efficiently etched by light or heat. For 1. Photoresist for non-development dry etching used in semiconductor integrated circuits or sensitizer for photoresist.

2. Read-only memory (ROM), write-once type organic polymer base material for optical recording.

3. Organic polymer material for microporous membrane.

4. Optical element materials such as diffraction gratings.

5. It aims to provide related materials with polymer materials used as easily photo-processable synthetic resins (drilling, cutting, surface modification, etc.).

[Relationship with Prior Art] Focusing on the high brightness and short wavelength properties of excimer lasers, an attempt to etch poly (methyl methacrylate), which is said to have the highest resolution as a polymer, with excimer lasers is a physicochemical study. Tokoromura, Toyota, Namba (Laser Research Vol.8, No.6, 941 (1980))
It was quickly confirmed that the excimer laser is extremely effective as a light source for photoetching, photolithography and the like.

Later, apart from Kawamura and others, R.Srinivasan “Laser Processing and Diagn” of International Business Machines Corporation (IBM)
ostics "Springer Series in Chemical Physics 39, Spri
(Nger-Verlarg, Berlin, 1984) found that when a polymer film was irradiated with a short-pulse far-ultraviolet excimer laser, etching at a depth of 1000 Å or more occurred photochemically instantaneously. Decomposition (Ablative Photo Decom
position).

Earl Srinivsan et al. Studied the initial melt-repellent decomposition using a 193 nm laser, and the main mechanism of the decomposition was photochemical etching, that is, direct electron excitation by photons resulted in chemical bonding of the polymer on the irradiated surface. He was proposing a mechanism to disconnect. However, when an excimer laser with a wavelength longer than 193 nm is used thereafter, a polymer having strong absorption in the ultraviolet region as a sample: poly (imide), poly (ethylene terephthalate), poly (carbonate)
It is recognized that the melt-repellent decomposition of these macromolecules is caused by etching mainly through thermal decomposition even with the use of ... (eg, J.Polym.Sci.Polym.Chem.Ed.Vol.22. , 2601-2609
(1984); Macromolecules, Vol. 19, No. 3 916-921 (198
6)). And for melt-down decomposition (1) melt-through decomposition via thermal decomposition.

(2) Photochemical melting and decomposing.

(3) Heat-assisted melt-back decomposition.

(Thermally-assisted (or activated) Photoproces
There are three ablative decomposition processes in s). 249nm
It has also been experimentally confirmed by other researchers that, when optical etching is performed with the above-mentioned long-wavelength excimer laser, melt-repellent decomposition by a thermal mechanism is likely to occur.

In the ultraviolet region, the light transmission distance to the inside of the polymer is short and the volume of light absorbed is small, so local temperature rise is likely to occur.
However, since thermal diffusion can be ignored for an extremely short time, even if optical processing is mainly thermal processing, processing with a certain degree of accuracy is possible. However, it is desirable to avoid etching due to thermal decomposition as much as possible in processing requiring high precision.

For example, when the same polymer is irradiated with excimer lasers of different wavelengths, it may be considered that etching with a longer wavelength is more likely to cause thermal ablative decomposition, but photo-etching with a longer wavelength than with a shorter wavelength. In the product produced, a large amount of polymer product is produced, the inner wall of the hole caused by etching is obviously rough, and the release product contains a large amount of the fused granular powder. It is said that the micro-patterns and lens fogging are likely to occur due to the scattering of the.

Increasing the rate of photolysis in the melt-down decomposition is extremely important for precision processing as described above, but this is due to the use of a short wavelength laser as described above and a low repetition frequency (usually 50 Hz or less). It is also possible to some extent by avoiding heat buildup, such as by using less than 1Hz). However, it is basically largely restricted by the properties of the polymer to be irradiated. For example, poly (methyl methacrylate)
The 308 nm excimer laser cannot cause melt-phobic decomposition, but only etching by thermal decomposition.
That is, a polymer that photolyzes only at a short wavelength cannot be photochemically etched in the long wavelength region even though it can be etched by thermal decomposition. On the other hand, a polymer that can be photochemically processed in the ultraviolet region of a long wavelength can be easily etched by melt-repellent photolysis even at a short wavelength. In addition to photochemical processing, such polymers can be thermally fused and decomposed by changing irradiation conditions. Therefore, it is possible to widen the processing range in performing the processing with light.

From this point of view, the present invention has been achieved as a result of earnestly searching for a polymer that easily undergoes melt-repellent photodecomposition even in the long wavelength side in the ultraviolet region.

[Structure of the Invention] As a polymer that is easily photochemically fused and decomposed by ultraviolet rays and can be thermally photoprocessed, a polymer containing a polycyclic fused aromatic compound in most of the skeleton of the polymer main chain is used. Molecules (Japanese Patent Application No. 61-13
(Application No. 0359), in addition to monocyclic aromatic polymers,
It has been found that there are polymers containing aromatic poly (ether sulfones) and poly (arylates). These polymers are easily photochemically processed not only by UV lasers with a shorter wavelength than other polymers but also by lasers with a wavelength longer than 200 nm. It has been found that disassembly can be performed. Further, as shown in the examples, these polymers have excimer
It can also be etched by the ultraviolet light emitted from a discharge lamp, which is much lower than a laser. In this case, (1) the thickness of these polymer films decreases at a measurable speed.

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

Conventionally, a great deal of research has been conducted on many polymers, because weather resistance is important as one of the practical characteristics of the change in physical properties of polymers (especially, reduction in mechanical elongation at break) due to ultraviolet irradiation. However, there are almost no reports of pursuing changes in the photo-etching property and irradiation surface of resins other than photo-degradable resins and photosensitive resins, especially heat-resistant polymers.
Slightly reported by P. Blais et al. (J.Appl.Polym.Sci.Vol.17.189
5 (1973) ・ ・ ・ Poly (ethylene terephthalate) is volatilized and dissipated by light. P.Blais
Etc. 30 on poly (ethylene terephthalate) film
Place a 0 mesh wire net and irradiate it for 1,000 hours with ultraviolet light, the film surface of the exposed part will be dented, and the pattern of the wire net will be transferred onto the film, and the poly (ethylene terephthalate) will be slightly etched by the light. I admit that.

In response to this prior known knowledge, the present inventors have found that the target polymer of the present invention is etched by ultraviolet rays significantly faster than poly (ethylene terephthalate).

[Outline of the Invention] Aromatic poly (ether sulfone) which is the object of the present invention
Is produced from 4,4'-dichlorodiphenyl sulfone as a raw material (there are also commercially available products), and has the following structure Have. Besides this Poly (ether sulfone) having the structure of is also commercially available and is included in the target polymer of the present invention.

Poly (arylate) is a polymer composed of aromatic dicarboxylic acid and bisphenol, but has a structural formula Are available on the market. However, bisphenol may be partially or wholly bisphenol-S instead of bisphenol-A. Further, a poly (arylate) obtained by using a hydroxyaromatic carboxylic acid as a starting material instead of the aromatic dicarboxylic acid and the aromatic diol may be used.

The poly (ether sulfone) and poly (arylate) which are the subject of the present invention also include those having one or more substituents on the benzene ring. Further, the polymer may be a crystalline or amorphous polymer. In the case of a crystalline polymer, light processing may be carried out without being stretched, or a stretched orientation may be used for light irradiation. Further, there is no problem even if light processing is performed in the unstretched state and then stretched and oriented for use in the subsequent use. Furthermore, compositions copolymerized, blended or block polymerized with other polymers also contain the aromatic poly (ether sulfone) or poly (arylate) of the present invention as long as the backbone of the main chain of the polymer contains an aromatic poly (ether sulfone) or poly (arylate). Included in the category of polymers.

As one example of interest to be used by blending, as a sensitizer, a polymer which is unlikely to undergo photochemical melting and decomposing, for example, poly (methyl methacrylate) is blended with a polymer to be the subject of the present invention. May be used. In this case, the blending amount is about several percent to several tens percent, and the effect as a sensitizer is sufficiently exhibited. Therefore, when the target polymer of the present invention is used as a sensitizer, the technique of the present invention can be applied as it is even if the polymer is a composition in which most of the polymer is not the target of the present invention.

Most of the ultraviolet rays used for irradiation may be ultraviolet rays having a wavelength shorter than 380 nm, and light including visible light may be used. Industrially, a discharge lamp (high-pressure mercury lamp, carbon arc, mercury resonance lamp, etc.) equipped with a near-ultraviolet transmission filter (lower limit shielding wavelength 290 nm) can be used. A more desirable light source is a pulse discharge tube containing argon or xenon that can emit a large amount of light (for example, 10 to 40 KJ / pulse) over a wide area in a short time. Further, by using a combination of the ultraviolet laser and the target polymer of the present invention, it is possible to perform efficient optical processing.
For these ultraviolet lasers, XeF (wavelength 350nm), N
_{In addition to 2} (wavelength 337 nm), XeCl (wavelength 308 nm), dye laser can be used as a light source to perform optical processing such as drilling, cutting, surface layer processing and surface modification. Prior to photoprocessing, a photosensitizer such as a dye or a catalyst may be added to the polymer of the present invention to perform light irradiation. The optical processing may be performed in any atmosphere of vacuum, inert gas, or air. Generally, the light processing temperature may be in the range of normal temperature to 100 ° C., but if thermal processing may be accompanied, the temperature may be further raised to irradiate light.

When precision processing is required when performing optical processing, almost the same degree of fine processing can be performed by combining with technology, processes and equipment such as photomasks and aligners for wafer exposure. In this case, a product with a significantly high added value or a significantly functionalized product can be produced.

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

Example-1 Photo-etching with a discharge lamp With a near-ultraviolet transmission filter as a light source (450 nm to 290 n
m) A water-cooled special discharge lamp 1.5KW was used. Its peak wavelength was 365 nm.

The irradiation film sample was placed on a rotary table 150 mm away from the light source and rotated 5 times per hour so that the irradiation was performed uniformly.

In this case, the effective irradiation area is 100 mm x 100 mm, and the uniformity is 90%.
That was all. When the irradiation energy on the film surface was measured with a UV digital meter, it was 27 mW / sec at 365 nm. In order to avoid thermal processing, cold air was blown to the surface of the sample with a blower so that the sample temperature became 80 ° C or less, and irradiation was performed for 100 hours.

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 sulfone) is VICTREX (trade name) film grade, and poly (arylate) is Unitika U-polymer-8000.
A sheet of (brand name) was obtained and used for the test. The test results are shown in the following table.

The decrease in film thickness after 100 hours of irradiation was 2% each as compared with the poly (ethylene terephthalate) shown in Comparative Example-1.
Etched twice or eight times as fast.

Comparative Example-1 The main polymers other than the photoresist used as the irradiated sample in the report of Earl Srinivsan and others are poly (methyl methacrylate), poly (imide), poly (carbonate), poly (ethylene terephthalate). Is.
The same tests as in Example-1 were conducted using sheets or films of these resins which are commercially available. The results are shown in Table 2.

From the above table, poly (ethylene terephthalate) and poly (carbonate) are slightly etched by light, but poly (methyl methacrylate) and poly (imide)
, The film thickness did not change even after 100 hours of irradiation.

Further, a test was carried out to confirm whether or not light absorption is a condition under which photoetching occurs. Since monocyclic aromatic polymers have ultraviolet absorption based on the benzene ring, they were tested in the same manner and conditions as in Example-1.

Irradiated samples were poly (ether / ether / ketone), poly (ether / imide), poly (phenylene / sulfide) and poly (sulfone). The post-irradiation samples all showed a marked decrease in elongation, and poly (sulfone) was particularly brittle. However, the film thickness did not change in any of the samples before and after irradiation, and no trace of photoetching was observed.

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

Although poly (sulfone) has high heat resistance, it has low weather resistance because it has absorption at around 320 nm, and it is susceptible to chemical changes due to ultraviolet light-photooxidative decomposition, which reduces the intrinsic viscosity of the polymer and reduces CO, CO It is known that the molecular weight is likely to decrease due to the occurrence of ₂ (BD Gensner, PG Kelleher, J. Appl. Polym.
Sci. Vol. 12, 1199 (1968)). Therefore, it was presumed that poly (sulfone) was mainly converted to a volatile substance by light and was susceptible to etching. However, in tests, poly (sulfone) is a polymer of the same family, poly (ether sulfone) --- absorption increases sharply below 330 nm--
It was found that the embrittlement mainly occurs by the irradiation, rather than the etching by the light. From the above, it cannot be said that photo-etching does not always occur even if the irradiated polymer has a strong absorption in the ultraviolet region even under the necessary conditions for photo-etching, and rather, embrittlement occurs predominantly. It turns out that there are cases where

It was also found that even a monocyclic aromatic polymer that absorbs in the ultraviolet region has a relatively small number of polymers that are easily etched by light, and is limited to a specific structure.

Example-2 Optical etching by excimer laser-
(1) XeCl (wavelength 308 nm) laser and KrF (wavelength 24) for reference
A commercially available poly (ether sulfone) film was irradiated by using a laser (8 nm) to conduct a drilling experiment. In the experiments, the full width at half maximum was 20 ns, and the pulse intervals (repetition frequency) were all set to 1 Hz to avoid thermal processing as much as possible.

The energy density per pulse is 50 mJ / cm ² to 6 J / cm ²
The relationship between the etching depth per pulse and the energy density was experimentally determined.

The poly (ether sulfone) used in the experiment is TALPA 1000LC (thickness 75 μm) manufactured by Mitsui Toatsu. The result of the test is shown in FIG.

For the energy density per pulse, a convex lens (focal length 100 mm or 170 mm) was used between the laser and the irradiated sample, and the specified energy density was obtained by adjusting the distance between the laser, the convex lens, and the sample, respectively. . Further, the etching depth per pulse was obtained by first obtaining the number of shots required to make a hole through a film having a predetermined thickness and then performing back calculation.

Example-3 Photo-etching by excimer laser-
(2) All tests were performed under the same conditions as in Example-2 except that commercially available poly (arylate) was used as the sample.

The poly (arylate) used is u-polymer u-8000 (thickness 100 μm) manufactured by Unitika. The test results are shown in FIG.

Next, the drawings and electron micrographs will be described.

FIG. 1 attached shows the relationship between the depth of etching per pulse and the energy density in Example-2 of the present invention. Further, FIG. 2 is a graph showing the relationship between the depth of etching per pulse and the energy density in Example-3 of the present invention.

Figures 3 and 4 are morphological observations of the film surface of a TALPA 1000LC manufactured by Mitsui Toatsu Co., Ltd. when 100 pulses of 800 mJ / cm ² / pulse of XeCl laser light (308 nm) was irradiated on the film surface using a scanning electron microscope (magnification × 2000) It is a thing. Here, FIG. 3: Laser light is vertically irradiated to the sample.

Figure 4: Irradiate the sample with laser light at an angle (45 °).

FIG. 5: No laser light irradiation. (Blank) Observation of the surface of the sample.

The fingerprint-like striped pattern in FIG. 3 has an interval of about 1 μm, but it shows that the shape of the striped pattern changes from a fingerprint pattern to a vertical striped pattern when the irradiation angle is changed.

[Brief description of drawings]

FIG. 1 and FIG. 2 are graphs showing the relationship between the irradiation energy density and the photoetching depth in the optical processing by the excimer laser. 3 to 5 are electron micrographs of the surface of the material before and after the irradiation with the excimer laser.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification number Reference number within the agency FI Technical display location C08G 75/23 NTV (72) Inventor Masahiro Hosoi 3-37-19 Oyama, Sagamihara City, Kanagawa Teijin Plastics Research Institute Co., Ltd. (56) References JP-A-60-245643 (JP, A) JP-A-57-117540 (JP, A)

Claims (1)

[Claims] 1. A method of photoprocessing a polymer, which comprises irradiating an aromatic poly (ether sulfone) or poly (arylate) with ultraviolet rays of 290 nm to 380 nm.