JP2023069982A - Exposure method - Google Patents

Abstract

To provide an exposure method for manufacturing inexpensive and highly integrated circuits.SOLUTION: Provided is a method in which a photoresist is covered with a photoresist-protecting cover and the gap between the photoresist and cover is filled with a solid, thereby deformation of the photoresist due to pressure in the vertical and horizontal directions of the photoresist is difficult to occur, and exudation of interaction between the photoresist and the solid is made to be less.

Description

The present invention relates to an exposure method for manufacturing integrated circuits.

If the density of an integrated circuit is increased, the precision will be increased, so efforts have been made to increase the density.

Therefore, there has been a demand for an exposure method that is inexpensive and has a low running cost to obtain a fine pattern, which is the key to the manufacture of integrated circuits.

JP 2020-184051 Nikkei XTECH Process Manufacturing Technology Overview Source: February-November 2006 Nikkei Microdevices 2-methyl-2-propanol Wikipedia

Immersion lithography has advanced to the point where water is used. However, there is a problem such as decomposition of the liquid containing the liquid by the exposure light.

High-density circuit pattern imaging requires a short-wavelength light source and a high-precision optical system, requiring a very expensive, high-intensity short-wavelength light source and increasing running costs.

The exposure method of the present invention is intended to solve such conventional problems, and is intended to provide an exposure method for high-density circuit patterns using inexpensive equipment and low running costs.

In the method of the present invention, in order to achieve the above object, the photoresist is covered, the photoresist and the cover are brought into close contact with each other, the small space between the photoresist and the cover is filled with a liquid, the liquid is cooled and solidified, and exposed. ing.

Effects of the present invention

Since the exposure method of the present invention employs the above-described method, the slight space between the photoresist and its cover is filled with a solidified substance, and the pressure exerted on the cover in the vertical or horizontal direction causes the It prevents the deformation of the photoresist and the generation of minute gases due to temperature changes.

In addition, since the gap between the photoresist and the cover is filled with a solidified liquid, the solid does not seep out from the photoresist, and conversely, the solid does not seep into the photoresist. Therefore, it is possible to use high refractive index alcohol or oil.

By performing immersion exposure on the photoresist cover, there is an effect that even if an oil system with a high refractive index of light is used, fine separated substances from the photoresist are not mixed.

Contact exposure using graphene or graphite as a photoresist cover eliminates the risk of photoresist peeling.

At this time, if the circuit pattern of the mask is covered with graphene or graphite, the circuit pattern of the mask is protected and there is no fear of adhesion of fine particles.

Also, when a mask having a circuit sandwiched between graphene or graphite is used, the mask has a three-dimensional structure, which reduces the vibration of the mask in the front-rear direction and in the plane direction, and causes almost no residual stress in the mask, and the graphene having the circuit pattern of the mask. Alternatively, if the graphite is protruded in the direction of the photoresist by an electric force, the photoresist can be brought into close contact with the mask with a uniform and extremely weak pressure, and the circuit pattern of the mask can be enlarged or reduced to align with the photoresist. and exposure by an EUV light source becomes possible.

During EUV exposure, water is filled between the photoresist and its cover graphene or graphite to form ice. .

FIG. 2 is an illustration of contact exposure of the exposure method of the present invention using graphene or graphite for the circuit pattern of the photoresist cover and the mask.

When the gap between the photoresist and its cover is filled with a liquid of 2-methyl-2-propanol having a melting point of 25.69° C. and a boiling point of 82.4° C. shown in Non-Patent Document 2, and is immediately cooled below the melting point and exposed, When the photoresist cover is under pressure when it is liquid, the movement of the liquid causes deformation of the photoresist.

In addition, if the material is solid, it is difficult for the components of the photoresist to penetrate, and the bubbles generated by the temperature change do not grow and become large.

When used for immersion exposure, the gap between the photoresist and its cover, the quartz glass plate, is very narrow, and has the same effect as filling the gap with a material having the optical refractive index of quartz glass.

Anisole with a melting point of -37°C and a boiling point of 154°C, which is used in oil immersion optical microscopes, is used between the photoresist cover glass and the objective lens. An immersion exposure is obtained.

When the cover is removed from the photoresist after the exposure, the photoresist is heated to the boiling point of 2-methyl-2-propanol of 82.4° C. or higher to evaporate 2-methyl-2-propanol, and the photoresist is exposed to the vapor pressure. When the cover is removed from the substrate, the photoresist does not come off and does not disturb the formed circuit pattern.

During contact exposure, graphene or graphite is used as a photoresist cover, and the circuit pattern formed on the quartz glass or fluorite substrate of the mask is directly adhered, or the circuit pattern of the mask is covered with graphene or graphite as a cover. The cover and the graphene or graphite that is the cover of the photoresist are in close contact with each other, and the alignment is performed while the cover is in close contact with the graphite. By doing so, the generation of fine particles is also reduced. The graphene or graphite cover applied to the mask and the mask body are in close contact with each other by electrostatic force.

For exposure to EUV light, as shown in FIG. A mask 6 made of a circuit pattern 5 is attached to an outer frame 7 and is brought into close contact with the cover 2 for exposure. At this time, the circuit pattern 5 is held by applying an electrostatic force between the two sheets of graphene or graphite 4 .

A repulsive electrostatic potential is applied to the electrode 8 installed inside the outer frame 7 and the mask 6 made of graphene or graphite, and the mask 6 is inflated slightly outward and brought into close contact with the photoresist cover 2, so that the mask 6 is uniform. It is possible to achieve close contact with a very small pressure, and by adjusting the extent to which the mask 6 bulges to the outside, it is possible to correct alignment due to distortion due to wafer warpage or the like.

Since it is a contact exposure, a reflective optical system for EUV light is not required, exposure can be performed with a weak EUV light source, and EUV light with a shorter wavelength can be used without wavelength selectivity, resulting in a finer pattern.

Since the photoresist 1 is covered with a solid 3 made of ice, outgassing from the photoresist 1 does not leak to the outside, and the inside of the mask 6 is cut off from the outside, so there is no contamination. Moreover, many spare parts can be prepared for the mask 6 by the nano-implantation method, and it can be cleaned by exchanging.

Since the graphene or graphite 4 has good thermal conductivity, the heat generated by the irradiation light at the time of exposure also immediately escapes to the side of the photoresist 1 and the temperature rise is small.

When the graphene or graphite 4, which is the cover 2 of the photoresist 1, is electrically connected to each other, when the wafer is chucked with an electrostatic chuck, the graphene or graphite 4 is a conductor and is strongly attracted to the solid 3. At this time, since the gap between the graphene or graphite 4 and the solid 3 is extremely small, an intermolecular force works and they are strongly adsorbed, and the graphene or graphite 4 of the mask 6 and the graphene or graphite 4 of the cover 2 are lightly adhered and aligned. However, the cover 2 cannot be peeled off.

INDUSTRIAL APPLICABILITY The present invention is used in an exposure process during integrated circuit fabrication.

1 photoresist 2 cover 3 solid 4 graphene or graphite 5 circuit pattern 6 mask 7 outer frame 8 electrode

Claims (5)

An exposure method in which a solid is placed between the photoresist and its cover for exposure. 2. The exposure method according to claim 1, wherein the immersion exposure is performed from outside the photoresist cover. 2. The exposure method according to claim 1, wherein graphene or graphite is used as a cover for the photoresist, and a mask is adhered thereon for exposure. 4. The exposure method according to claim 3, wherein the circuit pattern of the mask is covered with graphene or graphite for exposure. 4. The exposure method according to claim 3, wherein a mask formed by sandwiching a circuit pattern between graphene or graphite is brought into close contact with the exposure method.

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