JPH04314757A - Polyimide resin for laser processing - Google Patents

Abstract

PURPOSE:To obtain a polyimide resin for laser processing which is relatively inexpensive and is capable of fine, high aspect ratio and low-damage processing even by use of a long-wavelength laser by dispersing an aromatic polycyclic compound into the polyimide resin. CONSTITUTION:A polyimide resin is produced from an acid anhydride such as pyromellitic dianhydride and a diamine such as diaminodiphenyl ether. During or after producing the resin, an aromatic polycyclic compound is added and dispersed to produce a polyimide resin for laser processing. The aromatic polycyclic compound includes, for example, naphthalene, anthracene, pyrene and phthalocyanine and its effect generally increases as the number of the rings increases. By using the obtained polyimide resin, finer, higher aspect ratio and higher-quality processing than the conventional one can be performed even when using a short-wavelength laser, while fine processing can be performed even when using a long wavelength laser.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to a polyimide resin for laser processing.

0002

[Prior Art] FIGS. 4(a) and 4(b) are shown, for example, in the publication {J
．． Electrochem. Soc. , Oct. (19
90) This is a process diagram showing the conventional polyimide resin removal processing method shown in pages 2522-2527 in the order of steps, including light irradiation {Figure 4(a)} and development {Figure 4(b)}.
, shows the patterning or hole formation {FIG. 4(c)} and heating {FIG. 4(d)} steps. In the figure, 2 is the base material, 5 is the mask, 7 is the processed hole, 11 is the polyimide resin, 1
2 is a photosensitive polyimide precursor, 13 is a crosslinking part, 14 is a light source, 15 is light, and 16 is a developer.

That is, a polyimide precursor 12 imparted with photosensitivity is irradiated with light 15 from a light source 14 such as a mercury lamp, and only the irradiated portion 13 is crosslinked, thereby forming a developer 16.
The dissolution rate of the mask 5 is reduced, and the light is selectively removed from the portions blocked by the mask 5. Thereafter, the polyimide precursor 12 imparted with photosensitivity forms the structure of a normal polyimide resin 11 by heat treatment.

Furthermore, FIGS. 5(a) and 5(b) are, for example, publications {
Proceedings of LAMP '8
7 Osaka (May 1987) p581-
584} is a process diagram showing the conventional polyimide resin removal processing method shown in the process order, and each laser irradiation {
Figure 5(a)} and patterning or hole formation {Figure 5(a)} and patterning or hole formation {Figure 5(a)
b)} Shows the process. In the figure, 3 is a laser, 4 is a laser beam, and 6 is a lens.

That is, the laser beam 4 irradiated from the laser 3
is reduced and transferred onto the polyimide resin 11 using a mask 5 and a lens 6, and if the energy density of the laser is sufficient to remove the polyimide resin 11, removal processing such as patterning and hole formation is achieved. Moreover, the polyimide resin 11 in FIG.
Blackie (1990) p2-8}, etc., and has the following chemical formula 1.
is synthesized by

[0006]

[Chemical formula 1]

That is, a polyimide resin having a conventional structure is obtained by casting a polyimide precursor solution polymerized from an acid anhydride and a diamine in a solvent such as N-methylpyrrolidone, followed by dehydration and solvent removal treatment. Here, as the acid anhydride, those shown in FIG. 6 are used, and as the diamine, those shown in FIG. 7 are used.

[0008]

[Problems to be Solved by the Invention] The conventional polyimide resin and its processing method shown in FIG. 4 do not cause any effects such as heat damage when photosensitive polyimide resin is used, but the film thickness is large. It is not possible to cross-link deeply by light irradiation, and the cross-linked part and the layer beneath the cross-linked part are also removed during development, and the removal process proceeds isotropically, resulting in an increase in pattern width or hole diameter, and film loss. However, there is a problem in that it is difficult to form fine, high aspect ratio, and high quality holes. In addition, in this method, the polyimide precursor is processed and then heated to form a polyimide resin, so there is a problem that shrinkage and deformation occur during heating, and the price of the photosensitive polyimide precursor is high. There were also problems such as poorer properties compared to polyimide. Further, the conventional polyimide resin and its processing method shown in FIG. 5 are laser processing which does not require imparting photosensitivity and can use the polyimide resin after heat treatment. Conventional polyimide resin has long wavelength (500 nm ~
Absorption at short wavelengths (200-300 nm)
It is small compared to the absorption in m). When creating small, high aspect ratio, high-quality holes, long wavelength lasers require more energy to be applied due to the low optical absorption of the material, which can cause thermal damage or damage the underlying material. Furthermore, using a short wavelength laser has relatively large absorption, so it is possible to process with small energy and minimal damage to the underlying material, but depending on the required specifications of the process, There were a variety of problems, such as the lack of performance, the increased cost of lasers, and the inability to keep up with the development of accessory parts such as optical systems.

The present invention was made to solve the above-mentioned problems, and it is possible to perform fine processing, high aspect ratio, and low damage even by using a relatively inexpensive long wavelength laser, and it is also possible to perform processing using a short wavelength laser. Even when using
The purpose is to obtain a polyimide resin for laser processing that has a high aspect ratio and can be processed with high quality.

0010

[Means for Solving the Problems] The polyimide resin for laser processing of the present invention is made of a polyimide resin in which an aromatic polycyclic substance is dispersed.

[0011]

[Operation] Generally, in laser processing, the laser beam is absorbed by the material according to the material's absorption coefficient (absorbance per unit length), and this absorbed energy is used for processing. Furthermore, aromatic polycyclics generally have large absorption coefficients over a wide wavelength range. Since the polyimide resin in this invention has aromatic polycyclic substances dispersed therein, the absorption coefficient at each wavelength is large, and therefore absorption in the depth direction becomes large, and laser energy is concentrated in the extreme surface layer. This energy is converted into kinetic energy that instantaneously sublimates the resin or scatters decomposition products far away, so the thermal energy remaining in the polyimide resin is extremely small, making it difficult to cause thermal damage to the surrounding area. This makes it possible to form fine, high-quality holes, and to perform anisotropic processing, making it possible to achieve a high aspect ratio by repeating this process.

0012

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a process diagram showing a processing method using a polyimide resin for laser processing according to an embodiment of the present invention in order of steps. In the figure, numeral 1 indicates a high light absorption type polyimide resin which is a polyimide resin for laser processing according to an embodiment of the present invention. The laser beam 4 irradiated from the laser 3 is reduced and transferred onto the high light absorption type polyimide resin 1 using a mask 5 and lens 6, and patterning is performed if the energy density of the laser is sufficient to remove the high light absorption type polyimide resin 1. Removal processes such as hole formation and hole formation are accomplished. Specific examples of the structure of the high light absorption type polyimide resin 1 in this invention will be shown below, but the invention is not limited to these examples.

Example 1. The polyimide resin 1 for laser processing according to the embodiment of the present invention is as follows:
It can be obtained by the chemical formula 2 shown below.

[0014]

[Case 2]

That is, 1 for the weight of the polyimide precursor.
Approximately 0% of anthracene, an aromatic polycyclic compound, was prepared in advance by 8
The mixture is mixed into N-methylpyrrolidone, a solvent heated to about 0°C, stirred thoroughly, and then mixed into the polyimide precursor, which has been heated to about 80°C. As a polyimide precursor, R
1 is No. 1 in FIG. The skeleton of the acid anhydride shown in No. 1, R2 is No. 1 in FIG. This is a polyamic acid solution which is the skeleton of the diamine shown in 1. Thereafter, this mixture was applied to the substrate using a spin coater while keeping it at about 80°C to form a uniform film, and prebaked at about 150°C for about 30 minutes.
By post-baking at approximately 00°C for approximately 90 minutes, the N-methylpyrrolidone remaining in the film is evaporated, hydrogen groups and hydroxyl groups contained in the molecular chain of polyamic acid are reacted to form water, and molecules By detaching from the chains, a polyimide resin for laser processing according to an embodiment of the present invention is obtained. At this time, since anthracene is finely dispersed in such a polyimide resin, the absorption coefficient for each wavelength increases significantly, resulting in a highly light-absorbing polyimide resin. The absorption coefficient of the highly light-absorbing polyimide resin produced in this way at a wavelength of 530 nm is approximately 2000c.
m-1, which is 4 times greater than the approximately 500 cm-1 of conventional polyimide resin 10. This reduces the laser energy density required for laser processing, so for example, YAG
Machining that used to require several J/cm2 due to the second harmonic is now possible at around several hundred mJ/cm2, making it possible to perform processing with controllability in the depth direction and without heat damage in the periphery. Also wavelength 2
A diameter of 10 to 48 nm using a KrF excimer laser, for example.
When drilling a hole of about 20 μm, the hole that previously could only be tapered has become extremely anisotropic.
A high aspect ratio is now possible. In the embodiment of this invention, anthracene is added at 1% by weight based on the weight of polyamic acid.
A sufficient effect can be expected at around 0%, but it may be increased if it can be distributed, or it may be decreased depending on the specifications.
It is preferably about 3 to 30%. If it is less than 3%, it is difficult to obtain an effect, and if it exceeds 30%, dispersion becomes difficult.

FIGS. 2(a) and 2(b) are a cross-sectional view of a machined hole and a laser energy density in the depth direction of the machined hole during laser processing using the polyimide resin for laser processing according to the embodiment of the present invention, respectively. It is a characteristic diagram showing the distribution, and Fig. 3 (
(a) and (b) are a cross-sectional view of a machined hole and a characteristic diagram showing the laser energy density distribution in the depth direction of the machined hole, respectively, when laser processing is performed using a conventional polyimide resin. In the figure, Er is the minimum laser energy density required for processing, and E
i is the applied laser energy density. When the polyimide resin 1 for laser processing according to the embodiment of the present invention produced as described above is irradiated with a laser, absorption increases significantly, so that compared to the conventional polyimide resin 11 shown in FIG. Absorbed. Therefore, it is possible to perform processing with small processing units and good controllability. Therefore, it is possible to achieve a high aspect ratio, and even when the laser energy has a spatial distribution, the effect of tapering the machined hole 7 is small. Further, at this time, the amount of heat remaining in the polyimide resin is reduced, and the effects of heat accumulation due to repeated irradiation are also reduced, so the hole diameter does not spread to the surrounding area and become larger.

The aromatic polycyclic substance to be dispersed in the polyimide resin according to the present invention may be any substance as long as it increases light absorption of the desired wavelength without impairing other properties of the polyimide resin. For example, as shown in FIG. There are aromatic polycyclic compounds,
Generally, the larger the ring number, the greater the effect. Examples other than those shown in Figure 8 include phthalocyanine, penanthrene, decacyclene,
Compounds such as phenanthroline, perylene, porphyrin, and carbazole may also be used. Further, for example, a dye such as a coumarin-based dye may be used. Parts of these substituents are substituted with reactive groups to impart polarity to the molecule, which is more preferable because it is easily soluble in solvents.

In the above example, an aromatic polycyclic substance was dispersed in a polyimide precursor solution, and then heated and solidified to obtain a polyimide resin for laser processing according to an example of the present invention. It does not need to be used if it is not particularly necessary when mixing substances. In addition, for a system in which a polyimide solution can be obtained directly, an aromatic polycyclic substance may be mixed therein and dispersed. When using a solvent, the solvent is not particularly limited, and for example, conventionally used N-methylpyrrolidone or the like may be used. The machined hole is not limited to a hole that reaches the base material shown in the figure, but may be a hole that is stopped midway. Furthermore, the present invention can also be applied to polymer materials other than polyimide resins.

[0019]

[Effects of the Invention] As described above, by using a polyimide resin in which an aromatic polycyclic substance is dispersed, the present invention achieves fineness, high aspect ratio, and low damage even when using a relatively inexpensive long wavelength laser. It is possible to obtain a polyimide resin for laser processing that can be processed with finer details, higher aspect ratio, and higher quality than conventional ones even when a short wavelength laser is used.

[Brief explanation of the drawing]

FIG. 1 is a process diagram using a polyimide resin for laser processing according to an embodiment of the present invention.

FIG. 2 is a cross-sectional view of a machined hole and a characteristic diagram showing the laser energy density distribution in the depth direction of the machined hole during laser processing using a polyimide resin for laser processing according to an embodiment of the present invention.

FIG. 3 is a cross-sectional view of a processed hole when laser processing is performed using a conventional polyimide resin, and a characteristic diagram showing the laser energy density distribution in the depth direction of the processed hole.

FIG. 4 is a process diagram showing a conventional polyimide resin removal processing method in order of steps.

FIG. 5 is a process diagram showing the conventional polyimide resin removal processing method in order of steps.

FIG. 6 is a diagram showing examples of acid anhydrides used to synthesize polyimide resins.

FIG. 7 is a diagram showing examples of diamines used to synthesize polyimide resins.

FIG. 8 is a diagram showing an example of an aromatic polycyclic product according to the present invention.

[Explanation of symbols]

1 Polyimide resin for laser processing according to the embodiment of this invention 4 Laser light 7 Processed hole

Claims (1)

[Claims] 1. A polyimide resin for laser processing comprising a polyimide resin in which an aromatic polycyclic substance is dispersed.