KR20060135156A - Photomask and exposing method using the same - Google Patents

Abstract

A photo mask and an exposing method using the same are provided to increase resolution of a photoresist pattern formed on a wafer even though at least two patterns having different pitches are formed on one mask. A photo mask includes a transparent substrate, plural light shielding patterns formed on a front surface of the substrate to define a transmitting region on the substrate, and a transmittance control film(140) formed on a rear surface of the transparent to adjust an index of reflection of an entering light source(110). The light shielding pattern has a first pattern(146) having a first pitch and a second pattern(148) having a second pitch smaller than the first pitch. The first pattern is formed on a periphery region, and the second pattern corresponds to a cell region.

Description

Photo mask and exposure method using the same {PHOTOMASK AND EXPOSING METHOD USING THE SAME}

1 is a schematic diagram illustrating a wafer exposure apparatus according to the prior art.

FIG. 2 is a schematic diagram illustrating diffraction results of light transmitted through a mask applied to the exposure apparatus of FIG. 1.

3 is a schematic diagram illustrating a wafer exposure apparatus according to an exemplary embodiment of the present invention.

4 is a schematic diagram illustrating diffraction results of light transmitted through a mask applied to the exposure apparatus of FIG. 3.

5 is a schematic flowchart illustrating an exposure method according to an exemplary embodiment of the present invention.

* Description of the symbols for the main parts of the drawings *

100 wafer exposure apparatus 110 light source

120: condenser lens 130: mask

140: permeation control membrane 142: first permeation control membrane

144: second transmission control film 146: the first pattern

148: Second Pattern 150: Projection Lens

W: Wafer

The present invention relates to a photo mask and an exposure method using the same. More specifically, the present invention relates to a photomask for transferring a photoresist pattern to a photoresist film formed on a semiconductor substrate in a manufacturing process and an exposure method using the same.

Generally, a semiconductor device uses a deposition process for forming a film on a semiconductor substrate, a chemical mechanical polishing process for planarizing the film, a photolithography process for forming a photoresist pattern on the film, and the photoresist pattern. A series of unit processes such as an etching process for forming the film into an electrical pattern, an ion implantation process for implanting specific ions into a predetermined region of the semiconductor substrate, and a cleaning process for removing impurities on the semiconductor substrate are performed. Formed by performing.

Among these processes, a photolithography process is performed to form a predetermined circuit pattern on a semiconductor substrate.

In addition, the photolithography process includes a coating process for forming a photoresist composition layer on a semiconductor substrate, a bake process for curing the coated photoresist composition with a photoresist film, and transferring a pattern of a photo mask to the photoresist film. And a developing step for forming the photoresist film to which the pattern of the photo mask has been transferred as a photoresist pattern.

In addition, in order to perform the exposure process, a photo mask having a mask pattern corresponding to a circuit pattern transferred on a semiconductor substrate is required.

In general, the photo mask is divided into a light transmitting portion and a blocking portion so as to selectively transmit the debt of the light source, thereby selectively applying light to a specific region of the photoresist applied thereon to form a pattern. Is formed, and the etching process is performed using the photoresist pattern.

In this case, the photo mask is very important because the photo mask pattern becomes a source of the pattern to be formed on the semiconductor substrate.

Photolithographic apparatuses are largely classified into contact, proximity, and projection types according to alignment and exposure methods for matching a circuit pattern of a mask and a wafer.

Here, the contact type photolithography apparatus is the first to be developed, and is a method of exposing the mask in direct contact with the wafer, and the proximity type photolithography apparatus is a method of exposing the mask and the wafer while maintaining a constant gap.

However, the contact type photolithography apparatus has a problem that mask contamination and abnormality of the circuit pattern on the wafer due to impurity particles occur due to the adhesion between the mask and the wafer, and superposition that occurs when the mask and the wafer have different flatness. There was a problem that the precision is lowered.

In addition, the proximity photolithography apparatus has a problem in that the diffraction of the light is induced due to the gap between the mask and the wafer, thereby degrading resolution.

As an alternative to the contact and proximity exposure methods, therefore, the use of a projection type photolithography apparatus in semiconductor manufacturing using a projection exposure method that maintains a significant gap between the mask and the wafer and transfers the pattern on the mask through the lens onto the wafer is recommended. This is the current trend.

As the degree of integration of semiconductor devices increases and design rules decrease sharply, various problems arise due to the resolution limitation of photolithography.

Therefore, the use of resolution enhancement technology is required to manufacture semiconductor devices using photolithography near the resolution limit.

Accordingly, in photolithography technology, attention has been focused on increasing the resolution in the exposure process.

Such resolution enhancement techniques include a method of using a light source having a smaller wavelength than a conventional method, a method of using a phase inversion mask, and a method of using off-axis illumination (OAI), which is a kind of modified illumination method.

Theoretically, when the incident light is used, the resolution is increased by about 1.5 times compared to the conventional lighting, and the depth of focus (DOF) is also improved. As the degree of integration of semiconductor devices increases, it is important to improve the depth of focus, since no exposure of the photoresist is performed on the same focal plane in the wafer plane or anywhere in the same chip.

1 is a schematic diagram illustrating a wafer exposure apparatus according to the prior art.

Referring to FIG. 1, the exposure apparatus includes a light source 10, a condenser lens 20, a mask 30, a projection lens 40, and a wafer W. In FIG. In addition, a first pattern 32 having a relatively large pitch and a second pattern 34 having a relatively small pitch are formed on the entire surface of the mask 30. Light incident from the light source 10 (indicated by a solid arrow) passes through the condenser lens 20 and is irradiated to the entire surface of the mask 30 in a uniform direction. At this time, the diffraction light generated when passing through the first pattern 32 and the second pattern 34 is again collected by the projection lens 40 and transferred to the wafer (W).

Such a projection exposure method is recognized that there is no problem of low contamination and alignment, and is mainly applied to current semiconductor manufacturing, thereby improving productivity of semiconductor manufacturing.

In this case, when the first pattern 32 having a high pitch and the second pattern 34 having a low pitch exist as shown in the drawing, when the illumination system having one illumination condition is used as described above, the first pattern ( 32) and at least one of the second patterns 34 may not be normally formed.

In addition, in order to solve the problem, the exposure apparatus has a problem in that a plurality of masks 30 are manufactured according to the pattern pitch of the mask 30 to form a photoresist pattern on the wafer W.

FIG. 2 is a schematic diagram illustrating diffraction results of light transmitted through a mask applied to the exposure apparatus of FIG. 1.

Referring to FIG. 2, the photo mask 30 includes a transmission region for transmitting light generated from a light source (not shown) and a blocking region for blocking light. Light is diffracted while passing through the mask 30.

At this time, the light is not affected by the angle of incidence, and all the same amount of light is transmitted. Therefore, when the incident angle of light is suitably used for the second pattern 34, the image sharpness is lowered in the first pattern 32.

As a result, the entire process may become unstable, and an optimized mask of the first pattern 32 and the second pattern 34 may be manufactured and subjected to the exposure process twice. When the processes of the first pattern 32 and the second pattern are performed at the same time, the process becomes unstable because they must be mutually compromised.

Therefore, there is an urgent need for a new method that can effectively improve the resolution of a pattern on a wafer without involving extreme changes in current exposure illumination systems.

The problems as described above are serious limitations in view of the current trend of research on semiconductor devices that proceed in the direction of manufacturing high-performance semiconductor devices in a short time, and there is an urgent need for technology development to solve them. to be.

The first object of the present invention for solving the above problems is to provide a photo mask having a plurality of different pitch patterns and to improve the resolution on the substrate.

A second object of the present invention is to provide an exposure method using the photo mask as described above.

In order to achieve the first object of the present invention, a photo mask according to an embodiment of the present invention is formed on a transparent substrate and the front surface of the transparent substrate and a plurality of light shielding patterns defining a transmission area on the substrate, and the transparent substrate Is formed on the rear of the may include a transmission control film for adjusting the refractive index of the incident light source.

The exposure method according to another embodiment of the present invention for achieving the second object of the present invention comprises the steps of generating light from a light source, a transparent substrate, formed on the front surface of the transparent substrate to define a transmission region on the substrate Irradiating the light onto a photo mask including a plurality of light blocking patterns and a transmission control film formed on a rear surface of the transparent substrate to adjust a refractive index of an incident light source, and preserving the light passing through the photo mask pattern. Projecting onto the semiconductor substrate.

The photomask and the exposure method using the same according to the present invention configured as described above have a high resolution photoresist pattern on the wafer even if two or more patterns having different pitches exist in one mask. Can be formed on.

Hereinafter, a mask and an exposure method using the same according to an exemplary embodiment of the present invention will be described in detail with reference to the accompanying drawings.

3 is a schematic diagram illustrating a wafer exposure apparatus according to an exemplary embodiment of the present invention.

Referring to FIG. 3, the wafer exposure apparatus 100 includes a light source 110, a condenser lens 120, a mask 130, a transmission control layer 140, and a projection lens 150.

The light source 110, the condenser lens 120, the mask 130, the transmission control layer 140, and the projection lens 150 will be described in detail as follows. The solid arrows in the figure visually indicate the path of light.

Light of a specific wavelength is emitted to the light source 110, and the wavelength is continuously shortened due to the increase in the degree of integration. An excimer laser that emits an excimer laser beam may be used as the light source 110.

For example, a krypton fluoride (KrF) laser beam with a wavelength of 248 nm, a fluoride fluoride (ArF) laser beam with a wavelength of 193 nm, an argon fluoride laser with a wavelength of 157 nm, and a fluorine (F2) with a wavelength of 157 nm. A florin laser or the like that emits a laser beam may be used as the light source 110.

The condenser lens 120 focuses the light emitted from the light source 110 and allows uniform incidence on the entire surface of the mask 130 on which the pattern is formed.

In addition, the condenser lens 120 may vary the degree of condensing according to the pitch distribution of the pattern formed on the mask 130.

The mask 130 is a transparent substrate (not shown) made of a material capable of transmitting light provided from the light source 110 and a first pattern 146 selectively projecting and shielding the light provided to the transparent substrate. ) And a second pattern 148 having a pitch smaller than that of the first pattern 146.

In addition, the mask 130 includes the first pattern 146 and the second pattern 148 and has a structure surrounding the first pattern 146 and the second pattern 148. (Not shown) and on the pellicle frame to cover the first pattern 146 and the second pattern 148 so that the first pattern 146 and the second pattern 148 are not contaminated by dust or the like. A pellicle film (not shown) attached thereto may be provided.

In the above description, the mask 130 pattern is divided into two parts, but may be divided into several parts according to the pitch of the pattern.

In addition, the permeation control layer 140 is formed on the rear surface of the mask 130.

The permeation control layer 140 may include a first permeation control layer 142 and a second permeation control layer 144 having different thicknesses according to the position of the first pattern 146 and the position of the second pattern 148. The first permeation control layer 142 is formed to be thicker than the second permeation control layer 144.

In addition, the transmission control layer 140 is formed of a film having a different refractive index than the material of the mask 130. Accordingly, the transmittance is changed according to the angle of incidence, and since the amount of light transmitted is changed according to the angle of incidence at a specific thickness of the film, only light having a specific angle may increase transmittance.

The projection lens 150 selectively directs the light passing through the shielded mask onto the wafer W to be described later. Examples of the projection lens 150 include a reduced projection lens. An exposure method employing a refractive optical system whose exposure area is reduced by the magnification of the projection lens 150 is called a reduced projection exposure method.

Such a reduced projection exposure method may reduce the pattern pitch of the mask 130 as much as possible and make the pitch distribution of the pattern implemented on the wafer W uniform.

The photoresist pattern is formed on the wafer W by the light guided by the projection lens 150.

A photoresist film (not shown) is formed on the wafer W, and the photoresist film is formed on the wafer W through a photoresist composition coating process and a soft bake process.

The photoresist pattern formed through the exposure process may be used as an etching mask or an ion implantation mask.

FIG. 4 is a schematic diagram illustrating diffraction results of light transmitted through a mask 130 applied to the exposure apparatus of FIG. 3.

Referring to FIG. 4, the amount of light transmitted through the mask 130 is affected by a difference in incident angle at a specific thickness of the transmission control layer 144. In addition, the transmittance of the light having a specific incident angle may be increased, and the same effect may be obtained by changing the refractive index of the transmission control layer 144.

Therefore, when the exposure process of the first pattern 146 and the second pattern 148 is performed in the mask 130, if the thickness of the transmission control layer 144 is adjusted, the light of high angle is required. The first pattern 146 transmits a lot of light at a high angle, and the second pattern 148 requiring a low angle of light may be adjusted to receive a lot of light at a small angle.

Accordingly, the process of the first pattern 146 and the second pattern 148 having different pitches can be simultaneously performed without changing an existing exposure illumination system or additionally manufacturing a mask.

5 is a schematic flowchart illustrating an exposure method according to an exemplary embodiment of the present invention.

First, referring to FIGS. 3 and 4, first, light having a specific wavelength is generated from the light source 110 (step S10).

Thereafter, the generated light is focused on the condenser lens 120 and irradiated to the entire surface of the mask 130 in a uniform direction.

Referring to FIG. 3, the mask 130 may include a transparent substrate, a plurality of light blocking patterns formed on a front surface of the transparent substrate to define a transmissive region on the substrate, and a light source formed on the back surface of the transparent substrate and incident. It includes a including a transmission control film 140 for adjusting the refractive index.

In detail, the light blocking pattern includes the first pattern 146 and the second pattern 148 having a pitch smaller than that of the first pattern 146.

In addition, the permeation control layer 140 may include a first permeation control layer 142 and a second permeation control layer having different thicknesses according to the position of the first pattern 146 and the position of the second pattern 148. 144, and the first permeation control layer 142 is formed to be thicker than the second permeation control layer 144.

Referring to FIG. 4, the amount of light transmitted through the mask 130 is affected by a difference in incident angle at a specific thickness of the transmission control layer 144.

Therefore, when the exposure process is performed in the mask 130, the second pattern 148 through which the high angle light is transmitted through the first pattern 146 which requires high angle light and the low angle light is required. The thickness of the transmission control film 140 may be adjusted to transmit a lot of light of a small angle.

The projection lens 150 guides and transfers diffracted light generated when passing through the first pattern 146 and the second pattern 148 onto the wafer W (step S30).

Briefly referring to the exposure method, light is first generated from a light source. The light is connected to the mask 130 by the condenser lens 120.

The light connected to the mask 130 is diffracted through the first pattern 146 and the second pattern 148, wherein the light is selectively transmitted by the transmission control layer 140 according to the incident angle. do. The diffracted light is collected in the projection lens 150 and transferred to the wafer (W).

Therefore, due to this stabilized process, high resolution and an optimal depth of focus can be obtained, and it is also possible to form a pattern of a desired shape on the wafer W.

As described above, the mask and the exposure method using the same according to an embodiment of the present invention can improve the resolution of the photoresist pattern formed on the wafer even if two or more patterns having different pitches exist in one mask. have. In addition, the operating performance and yield of the semiconductor device can be improved.

Although described above with reference to a preferred embodiment of the present invention, those skilled in the art will be variously modified and changed within the scope of the invention without departing from the spirit and scope of the invention described in the claims below I can understand that you can.

Claims (6)

Transparent substrate; A plurality of light blocking patterns formed on the front surface of the transparent substrate to define a transmission region on the substrate; And And a transmission control film formed on the rear surface of the transparent substrate to control the refractive index of the incident light source. The method of claim 1, wherein the plurality of light blocking patterns include a first pattern having a first pitch and a second pattern having a second pitch smaller than the first pitch. Photo mask. The photomask of claim 2, wherein the first pattern corresponds to a peripheral region to be formed on a semiconductor substrate, and the second pattern corresponds to a cell region to be formed on the semiconductor substrate. The photomask of claim 2, wherein the transmission control film includes a first transmission control film and a second transmission control film having different thicknesses according to the position of the first pattern and the position of the second pattern. The photomask of claim 4, wherein the first permeation control layer is thicker than the second permeation adjustment layer. Generating light from a light source; A photomask image including a transparent substrate, a plurality of light shielding patterns formed on a front surface of the transparent substrate to define a transmission area on the substrate, and a transmission control layer controlling a refractive index of a light source formed on a rear surface of the transparent substrate and incident Irradiating the light on; And Projecting light passing through the photo mask pattern onto a predetermined semiconductor substrate.

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