JP2006126695A - Method for forming pattern - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for forming a pattern by which an alignment mark can be accurately detected to form a pattern even when high positional accuracy is required with a small-sized high performance device, in exposure techniques in a photolithography process of a semiconductor device and a printed wiring board or in a simple curing process of a photosensitive resin. <P>SOLUTION: In a process of forming a photosensitive resin pattern on a substrate, a portion except for a pattern forming portion is first exposed and developed to obtain an alignment mark, and then the pattern portion is exposed and developed. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

The present invention relates to an exposure technique in a photolithography process for a semiconductor element, a printed wiring board, or the like, or a process for simply curing a photosensitive resin, and more particularly to a pattern forming method for adjusting the alignment between a photomask and an exposed substrate for exposure.

With the development of electronics, the miniaturization of peripheral devices such as semiconductor devices or related semiconductor packages has continued unchanged in recent years.
A factor driving miniaturization is the social demand for enabling rapid processing of the information volume that has been increasing in recent years.
In order to meet such demands, not only the semiconductor elements themselves, but also the surrounding semiconductor package substrates, printed wiring boards, and even those that connect substrates or information terminals have advanced high-speed response technology. I have to let it.

Among these, in particular, progress in miniaturization technology in semiconductor elements, their packages, and printed wiring boards has been made from various fields and directions.
In the semiconductor element, development of a new material for the gate insulating film of the MOSFET and proposal of an element structure for suppressing impact ionization due to the short channel effect have been performed from the viewpoint of materials and structures.
Also in semiconductor package substrates, the connection from the package substrate to the printed circuit board is changed from the lead frame to the BGA, and the connection between the chip and the package substrate is changed from wire bonding to flip chip bonding. In addition, the viewpoint of development of materials suitable for miniaturization and fine materials is also being actively carried out.

However, the technology that supports such miniaturization technology from the ground up and contributes most to miniaturization is the improvement of the photolithographic technology. By the improvement of this photolithographic technology, the element elements can be reduced, and the wiring patterns and patterns Miniaturization on a physical scale such as width reduction is possible.

Here, as the element elements to be formed and the scale of the wiring are miniaturized, more stringent positional accuracy is required.
It is an exposure process using a mask that determines the position of a pattern in a patterning process such as formation of elements and circuits on a printed wiring board such as the semiconductor element and its package.
There are various alignment marks for this purpose, such as those with part of the processing material with irregularities, those with through holes, and those with some pattern printed, but in most cases the confirmation method is Although there are various differences in the specific method, the alignment is basically performed by irradiating the alignment mark portion with light and detecting the scattered light, reflected light, diffracted light, or transmitted light. Position alignment by visual recognition is performed.

In such an alignment method, a decrease in the visibility of the alignment mark causes a serious problem of insufficient direct position accuracy.
One of the factors that reduce the visibility of the mark is adhesion of the resist to the alignment mark site.
In order to form a pattern, the step of applying a resist is performed before the exposure. In particular, when a liquid resist is used, it may be difficult to apply it while avoiding only the alignment mark portion.
Further, since the resist generally has a unique color, when the resist adheres to the alignment mark site, there arises a problem that the visibility of the alignment mark is further lowered during exposure. This tendency becomes more prominent as the applied resist film thickness increases.

For example, even when the alignment method described in Patent Document 1 is used, the positional accuracy is not limited to the detection ability of alignment marks provided on the periphery of a pattern area on a straight line that passes through the center of the pattern, that is, visibility. The above problem remains unsolved.
JP-A-4-369825

Therefore, the present invention accurately detects the alignment mark even when high positional accuracy is required as the semiconductor package substrate, the printed wiring board, or the semiconductor element is miniaturized and enhanced in performance. An object of the present invention is to provide a pattern forming method that can be formed.

The present invention has been made in view of the above-mentioned problems, and the first invention is an alignment in which a portion other than the pattern forming portion is exposed and developed in the step of forming a photosensitive resin pattern on the substrate. A pattern forming method is characterized in that after a mark exists, exposure and development are performed on a pattern portion to form a pattern.

According to a second aspect of the present invention, in the pattern forming method, the photosensitive resin to be used is a positive type.

According to a third aspect of the present invention, there is provided a pattern forming method, wherein the pattern portion is formed on the exposed portion other than the pattern portion with reference to the alignment mark.

According to a third aspect of the present invention, there is provided a pattern forming method, wherein the alignment mark is a hole formed in a substrate.

According to a fourth aspect of the present invention, there is provided a method for forming a putter, wherein the alignment mark is a hole penetrating the substrate.

According to a fifth aspect of the present invention, there is provided a pattern forming method, wherein the wavelength for detecting the alignment mark is different from the wavelength for exposing the pattern portion.

The present invention relates to a processing material having alignment marks such as a printed wiring board, a semiconductor element, and a package substrate thereof. By performing the steps of performing only the exposure and development, the visibility of the part can be improved, and the effect of improving the alignment accuracy is achieved.
Moreover, when performing this process, there is an effect of suppressing a decrease in productivity due to an increase in processes by using a wavelength band different from the wavelength band normally used.

Generally, in the exposure method, exposure is performed in a state where the photomask and the substrate to be exposed are in contact, contact exposure, exposure is performed by bringing the distance between them to several μm to several mm, proximity exposure, between the two. Examples include projection exposure in which a pattern is projected through a lens.
The projection exposure method is further divided into a method of exposing a necessary pattern on the substrate at once and a so-called step-and-repeat exposure method of dividing a pattern and repeating exposure and movement of the substrate and lens for each division.
The exposure method of the present invention is equipped with a mechanism for aligning alignment marks in any of these exposure methods, and has versatility that can be applied if the confirmation method is based on visual recognition.
In addition, the photosensitive resin such as a resist can be applied to any one of a liquid and dry film, but since the process of the present invention includes a process of exposing a pattern later, Even in such a case, a positive type photosensitive resin in which an exposed portion is developed is applicable.

As described above, when a photosensitive resin such as a liquid resist adheres to the alignment mark portion in the substrate to be exposed, the visibility of the portion is lowered.
For this reason, alignment during exposure to the alignment mark portion becomes difficult. However, in this case, the alignment accuracy allows exposure to the portion, that is, removal of the resist at the portion. Therefore, it is sufficient that the accuracy is within 100 μm, that is, the accuracy of within 100 μm is satisfied. In most cases, there is no problem.

As a method of exposing only the alignment mark portion in the substrate to be exposed, a method using a mask that transmits light only in a portion corresponding to the portion, an optical system different from the optical system used for normal exposure, or a collection method is used. By using an optical system having a variable light pattern, a method of condensing light from a light source only on the part can be considered.

Further, the exposure process of the present invention is as described above with respect to the positional accuracy, and a highly fine processing accuracy or a cross-sectional shape without a taper is not required in the resin after development. As a light source used in the exposure step, a light source having a wide wavelength band that is different from the light source wavelength of pattern exposure in which a single wavelength is generally used, that is, a photosensitive wavelength band of a photosensitive resin such as a resist is used. Is possible.

Alignment accuracy using the part by removing the resist of the part by improving the visibility by developing the substrate exposed only to the part of the alignment mark using the above technique by a normal development process. Will be improved.

Hereinafter, the above-described embodiment will be described in detail by way of examples. However, the present invention is not limited to these illustrated examples.

As a substrate to be exposed, a 5 μm-thick liquid resist for forming a circuit pattern with a copper wire is applied on the entire surface, the thickness with a copper foil is 1.0 mm, and the size is 10 cm × 10 cm. The rigid substrate was used.
As shown in FIG. 1, the substrate 1 to be exposed has through-hole-shaped alignment mark portions 2 in the vicinity of both upper and lower ends, and from a light source different from the exposure source through the same optical system used for exposure. Alignment is performed by irradiating the part with the light and detecting the transmitted light.
In this example, after performing exposure of about 500 mj / cm as an exposure amount only on the part, a development process that is not different from a normal one was performed, and a normal exposure process for exposing a circuit pattern was performed.

Generally, in a positive type liquid resist, the film thickness slightly decreases after development in an unexposed area.
In the conventional method, in the subsequent processes such as etching and ion doping in the semiconductor process, this slight decrease is not a problem.
However, in the present invention, since the steps of exposure and development are performed twice in total, there is a concern that a decrease in film thickness causes a problem.

Table 1 summarizes the resist film thickness and the remaining film ratio when the normal exposure process is continued after the exposure process of the present invention is performed in this example.
Here, the residual film ratio is the ratio of the film thickness after development to that before development, that is, after coating. As a result, it can be seen that the remaining film ratio is 95% or more even if the development in the normal photolithography process is performed later through the process of the present invention.
With this remaining film ratio, there will be no problem in general subsequent processes such as etching and ion doping.

Actually, in the three examples of this embodiment listed in Table 1, in any case, a normal circuit wiring pattern can be obtained without any special measures in the subsequent circuit pattern forming process. It was.

For the improvement of the position accuracy, the position of a specific portion of the circuit pattern in the case where the circuit pattern is formed after the process of the present invention and the case where the circuit pattern is formed without the process of the present invention as in the past. This was done by measuring the deviation distribution and comparing it.
In the conventional method, it is widely distributed in a circle having a radius of about 30 μm, and the average value of the deviation is 18.7 μm.
However, in the case formed by the process of the present invention, the distribution of misalignment was within a circle with a radius of about 9.4 μm, and the average value was greatly improved to 5.6 μm.

Explanatory drawing which shows the example of the board | substrate used for pattern formation of this invention.

Explanation of symbols

1 ... Substrate 2 ... Alignment mark part

Claims (6)

In the process of forming the pattern of the photosensitive resin on the substrate, after exposing the portions other than the pattern forming portion and having the developed alignment mark, the pattern portion is exposed and developed to form a pattern. A pattern forming method. The pattern forming method according to claim 1, wherein the photosensitive resin is a positive type. The pattern forming method according to claim 1, wherein the pattern portion is formed on the exposed portion other than the pattern portion with reference to the alignment mark. The pattern forming method according to claim 1, wherein the alignment mark is a hole formed in the substrate. The method for forming a putter according to claim 4, wherein the alignment mark is a hole penetrating the substrate. The pattern forming method according to claim 1, wherein a wavelength for detecting the alignment mark is different from a wavelength for exposing the pattern portion.

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