Exposure system and pattern formation method

CROSS-REFERENCE TO RELATED APPLICATIONS

0001This application claims priority under 35 U.S.C. §119 on Patent Application No. 2004-259769 filed in Japan on September 7, 2004, the entire contents of which are hereby incorporated by reference.

BACKGROUND OF THE INVENTION

0002The present invention relates to an exposure system for use in fabrication process or the like for semiconductor devices and a pattern formation method using the same.

0003In accordance with the increased degree of integration of semiconductor integrated circuits and downsizing of semiconductor devices, there are increasing demands for further rapid development of lithography technique. Currently, pattern formation is carried out through photolithography using exposing light of a mercury lamp, KrF excimer laser, ArF excimer laser or the like, and use of F₂ laser lasing at a shorter wavelength is being examined. However, since there remain a large number of problems in exposure systems and resist materials, photolithography using exposing light of a shorter wavelength has not been put to practical use.

0004In these circumstances, immersion lithography has been recently proposed for realizing further refinement of patterns by using conventional exposing light (for example, see M. Switkes and M. Rothschild, "Immersion lithography at 157 nm", J. Vac. Sci. Technol., Vol. B19, p. 2353 (2001)).

0005In the immersion lithography, a region in an exposure system sandwiched between a projection lens and a resist film formed on a wafer is filled with a liquid having a refractive index n (whereas n > 1) and therefore, the NA (numerical aperture) of the exposure system has a value <b>n·NA.</b> As a result, the resolution of the resist film can be improved.

0006Now, a conventional pattern formation method employing the immersion lithography will be described with reference to FIGS. <b>8A</b> through <b>8D.</b>

0007First, a positive chemically amplified resist material having the following composition is prepared: <tables id="tabl0001" num="0001"><table frame="none"><tgroup cols="2" colsep="0" rowsep="0"><colspec colnum="1" colname="col1" colwidth="151mm" colsep="0" /><colspec colnum="2" colname="col2" colwidth="15mm" colsep="0" /><tbody><row><entry namest="col1" nameend="col1" align="left" valign="top">Base polymer: poly((norbornene-5-methylene-t-butylcarboxylate) (50 mol%) - (maleic anhydride) (50 mol%))</entry><entry namest="col2" nameend="col2" align="left" valign="top">2 g</entry></row><row><entry namest="col1" nameend="col1" align="left" valign="top">Acid generator: triphenylsulfonium triflate</entry><entry namest="col2" nameend="col2" align="left" valign="top">0.06 g</entry></row><row><entry namest="col1" nameend="col1" align="left" valign="top">Quencher: triethanolamine</entry><entry namest="col2" nameend="col2" align="left" valign="top">0.002 g</entry></row><row><entry namest="col1" nameend="col1" align="left" valign="top">Solvent: propylene glycol monomethyl ether acetate</entry><entry namest="col2" nameend="col2" align="left" valign="top">20 g</entry></row></tbody></tgroup></table></tables>

0008Next, as shown in FIG. <b>8A</b>, the aforementioned chemically amplified resist material is applied on a substrate <b>1</b> so as to form a resist film <b>2</b> with a thickness of 0.35 µm.

0009Then, as shown in FIG. <b>8B,</b> with water 3 for immersion lithography provided on the resist film <b>2,</b> pattern exposure is carried out by irradiating the resist film <b>2</b> with exposing light <b>4</b> of ArF excimer laser with NA of 0.68 through a mask <b>5.</b>

0010After the pattern exposure, as shown in FIG. <b>8C,</b> after discharging the water 3 for immersion lithography, the resist film 2 is baked with a hot plate at a temperature of 110°C for 60 seconds, and the resultant resist film is developed with a 0.26 N tetramethylammonium hydroxide developer. In this manner, a resist pattern <b>2a</b> made of an unexposed portion of the resist film 2 is formed as shown in FIG. <b>8D.</b>

0011As shown in FIG. <b>8D,</b> however, the resist pattern <b>2a</b> formed by the conventional pattern formation method is in a defective shape.

SUMMARY OF THE INVENTION

0012The present inventors have variously examined the reason why the resist pattern <b>2a</b> formed by the conventional immersion lithography is in a defective shape, resulting in finding the following:

0013The conventional pattern is in a defective shape because the water <b>3</b> used for immersion lithography, which has been discharged from above the resist film <b>2</b> after the exposure, still remains on the resist film <b>2</b> after the exposure, and remaining drops of the water <b>3</b> deteriorate the resist. This deterioration of the resist is caused through contact between the remaining drops and the resist, and the influence of the remaining drops increases with time. Also, it has been found that if the resist film <b>2</b> is subjected to the post exposure bake with the drops remaining thereon, the resist is more largely deteriorated.

0014The resist is deteriorated by the drops as follows:

0015In general, a resist is made of a material minimally dissolved in a water-soluble liquid, and a very small amount of liquid does not easily permeate into the resist film through its surface before the exposure. At this point, FIG. <b>9A</b> schematically shows an example of a plan structure of an exposed resist pattern composed of line patterns <b>20a</b> and hole patterns <b>20b</b> and formed on a substrate <b>10</b> with an insulating film <b>15</b> sandwiched therebetween. FIG. <b>9B</b> is a schematic cross-sectional view taken on line IXb-IXb of FIG. <b>9A.</b> As shown in FIG. <b>9A,</b> the chemical state of the surface of the exposed resist film <b>20</b> is largely different from that attained before the exposure, and the line patterns <b>20a</b> and the hole patterns <b>20b</b> corresponding to exposed portions where an acid is generated through the exposure and an unexposed portion <b>20c</b> (where no acid is generated) are present in a mixed manner in accordance with the layout of mask patterns.

0016Immediately after the exposure, a portion where the largest amount of acid has been generated on the resist film 20 is the surface of the exposed portions <b>20a</b> and <b>20b</b> of the resist film <b>20,</b> and the acid in an amount necessary and sufficient for development is not always generated in the whole exposed portions immediately after the exposure. Accordingly, if a small amount of liquid remains on the surface of the resist film <b>20</b> immediately after the exposure, the acid elutes from the surfaces of the exposed portions <b>20a</b> and <b>20b,</b> where the largest amount of acid is present, into a remaining drop <b>30</b> of the liquid as shown in FIG. <b>9B.</b> Furthermore, the drop <b>30</b> spreads between and partially covers adjacent exposed portions <b>20a</b> as shown in FIG. <b>9B,</b> so as to cause a situation (phenomenon) that a larger amount of acid is eluted from the exposed portions <b>20a</b> and the acid is supplied also onto the unexposed portion <b>20c.</b> As a result, the pattern is formed in a defective shape because part of the exposed portions <b>20a</b> and <b>20b</b> does not dissolve in the development or part of the unexposed portion <b>20c</b> dissolves in the developer. In particular, when the pattern is refined in such a manner that, for example, the distance between the line patterns <b>20a</b> is 0.25 µm or less or the size of the hole pattern is 0.30 µm or less, even a small amount of liquid spreads over adjacent line patterns <b>20a.</b> Furthermore, even when a small amount of acid is eluted owing to the drops, the solubility in the developer is largely lowered if the pattern size is smaller.

0017When the resist pattern in such a defective shape is used for etching a target film, the resultant pattern of the target film is also in a defective shape, and hence, the productivity and the yield of the fabrication process for semiconductor devices are disadvantageously lowered.

0018In consideration of the aforementioned conventional problem, an object of the invention is forming a fine pattern in a good shape by preventing a resist film from being deteriorated by drops of a liquid having been used for immersion lithography.

0019In order to achieve the object, according to the present invention, in the exposure system and the pattern formation method employing the immersion lithography, an immersion liquid is discharged after pattern exposure, and remaining drops of the immersion liquid are removed and dried so that none of the immersion liquid can remain on a resist film.

0020Specifically, the exposure system of this invention includes an exposure section for irradiating a formed resist film with exposing light through a mask with an immersion liquid provided on the resist film; and a drying section for drying a surface of the resist film after irradiation.

0021In the exposure system of this invention, since the immersion liquid does not remain on the surface of the exposed resist film, the resist film can be prevented from being deteriorated by remaining drops of the liquid. Accordingly, when the resist film is developed in a development system thereafter, degradation of a pattern shape derived from insufficient dissolution in a developer or unwanted dissolution of an insoluble portion can be prevented in an exposed portion or an unexposed portion of the exposed resist film, resulting in obtaining a resist pattern in a good shape.

0022In the exposure system of the invention, the drying section preferably includes air blowing means.

0023In the exposure system of the invention, the drying section preferably includes dehumidification means.

0024In the exposure system of the invention, the drying section preferably includes warming means.

0025In the exposure system of the invention, the resist film is preferably formed on a wafer, and the drying section preferably dries a whole top surface of the wafer.

0026In this case, the exposure section preferably includes twin stages having at least two wafer placing portions, and the whole top surface of the wafer is preferably dried on one of the wafer placing portions of the twin stages.

0027In the exposure system of the invention, the air blowing means is preferably an air fan capable of blowing warm air.

0028In the exposure system of the invention, the dehumidification means can be a dehumidification apparatus for lowering humidity of an environment around the resist film by using a refrigerant. The refrigerant can be a hydrocarbon-based gas such as isobutane, butane, propane or cyclopropane, and the refrigerant is circulated through a compressor.

0029In the exposure system of the invention, the dehumidification means can be a drying agent for lowering humidity of an atmosphere around the resist film. An example of the drying agent is desiccant, and such a drying agent adsorbs moisture contained in the atmosphere for dehumidification.

0030In the exposure system of the invention, the warming means can be a warming apparatus for warming an atmosphere around the resist film.

0031The first pattern formation method of this invention includes the steps of forming a resist film on a substrate; performing pattern exposure by selectively irradiating the resist film with exposing light with an immersion liquid provided on the resist film; removing the immersion liquid remaining on a surface of the resist film after the pattern exposure; and forming a resist pattern by developing the resist film after removing the immersion liquid.

0032In the first pattern formation method, the resist film can be prevented from being deteriorated by the remaining drops of the immersion liquid. Therefore, degradation of the pattern shape derived from insufficient dissolution in a developer or unwanted dissolution of an insoluble portion can be prevented in an exposed portion or an unexposed portion of the resist film, resulting in obtaining the resist pattern in a good shape.

0033In the first pattern formation method, the step of removing the immersion liquid is preferably a step of blowing air against the resist film after the pattern exposure, a step of dehumidifying an atmosphere around the resist film after the pattern exposure, or a step of warming the resist film after the pattern exposure.

0034The second pattern formation method of this invention includes the steps of forming a resist film on a substrate; performing pattern exposure by selectively irradiating the resist film with exposing light with an immersion liquid provided on the resist film; blowing air against the resist film after the pattern exposure; and forming a resist pattern by developing the resist film after blowing air against the resist film.

0035In the second pattern formation method, even when drops of the immersion liquid remain on the resist film after discharging the immersion liquid after the pattern exposure, the drops are evaporated by blowing the air and the surface of the resist film is dried, and therefore, the resist film can be prevented from being deteriorated by the drops. Accordingly, degradation of the pattern shape derived from insufficient dissolution in a developer or unwanted dissolution of an insoluble portion can be prevented in an exposed portion or an unexposed portion of the resist film, resulting in obtaining the resist pattern in a good shape.

0036The third pattern formation method of this invention includes the steps of forming a resist film on a substrate; performing pattern exposure by selectively irradiating the resist film with exposing light with an immersion liquid provided on the resist film; dehumidifying an atmosphere around the resist film after the pattern exposure; and forming a resist pattern by developing the resist film after dehumidification.

0037In the third pattern formation method, even when drops of the immersion liquid remain on the resist film after discharging the immersion liquid after the pattern exposure, the drops are evaporated by dehumidifying the atmosphere around the resist film and the surface of the resist film is dried, and therefore, the resist film can be prevented from being deteriorated by the drops. Accordingly, degradation of the pattern shape derived from insufficient dissolution in a developer or unwanted dissolution of an insoluble portion can be prevented in an exposed portion or an unexposed portion of the resist film, resulting in obtaining the resist pattern in a good shape.

0038The fourth pattern formation method of this invention includes the steps of forming a resist film on a substrate; performing pattern exposure by selectively irradiating the resist film with exposing light with an immersion liquid provided on the resist film; warming the resist film after the pattern exposure; and forming a resist pattern by developing the resist film after warming the resist film.

0039In the fourth pattern formation method, even when drops of the immersion liquid remain on the resist film after discharging the immersion liquid after the pattern exposure, the drops are evaporated by warming the resist film and the surface of the resist film is dried, and therefore, the resist film can be prevented from being deteriorated by the drops. Accordingly, degradation of the pattern shape derived from insufficient dissolution in a developer or unwanted dissolution of an insoluble portion can be prevented in an exposed portion or an unexposed portion of the resist film, resulting in obtaining the resist pattern in a good shape.

0040In the second pattern formation method of the invention, the air is preferably warm air.

0041In the third pattern formation method of the invention, the atmosphere is dehumidified preferably by using a refrigerant.

0042In the fourth pattern formation method of the invention, the atmosphere is dehumidified preferably by using a drying agent.

0043In any of the first through fourth pattern formation methods of the invention, the immersion liquid can be water or perfluoropolyether.

0044In any of the first through fourth pattern formation methods of the invention, the exposing light can be KrF excimer laser, Xe₂ laser, ArF excimer laser, F₂ laser, KrAr laser

0045or Ar₂ laser.

BRIEF DESCRIPTION OF THE DRAWINGS

0046<ul id="ul0001" list-style="none" compact="compact"><li>FIG. <b>1A</b> is a cross-sectional view of a principal part of an exposure system according to Embodiment 1 of the invention;</li><li>FIG. <b>1B</b> is a plan view of an air fan provided in the exposure system of Embodiment 1 of the invention;</li><li>FIGS. <b>2A, 2B</b> and <b>2C</b> are cross-sectional views for showing procedures in a pattern formation method using the exposure system of Embodiment 1 of the invention;</li><li>FIGS. <b>3A</b> and <b>3B</b> are cross-sectional views for showing other procedures in the pattern formation method using the exposure system of Embodiment 1 of the invention;</li><li>FIGS. <b>4A, 4B</b> and <b>4C</b> are cross-sectional views for showing procedures in a pattern formation method using an exposure system according to Embodiment 2 of the invention;</li><li>FIGS. <b>5A</b> and <b>5B</b> are cross-sectional views for showing other procedures in the pattern formation method using the exposure system according to Embodiment 2 of the invention;</li><li>FIGS. <b>6A, 6B</b> and <b>6C</b> are cross-sectional views for showing procedures in a pattern formation method using an exposure system according to Embodiment 3 of the invention;</li><li>FIGS. <b>7A</b> and <b>7B</b> are cross-sectional views for showing other procedures in the pattern formation method using the exposure system according to Embodiment 3 of the invention;</li><li>FIGS. <b>8A, 8B, 8C</b> and <b>8D</b> are cross-sectional views for showing procedures in a conventional pattern formation method employing immersion lithography; and</li><li>FIGS. <b>9A</b> and <b>9B</b> are diagrams of a resist pattern obtained after exposure by employing the immersion lithography for explaining a problem to be solved by the invention, wherein FIG. <b>9A</b> is a schematic plan view of the resist pattern and FIG. <b>9B</b> is a cross-sectional view thereof taken on line IXb-IXb of FIG. <b>9A.</b></li></ul>

DETAILED DESCRIPTION OF THE INVENTION

EMBODIMENT 1

0047Embodiment 1 of the invention will now be described with reference to the accompanying drawings.

0048FIG. <b>1A</b> schematically shows the cross-sectional structure of a principal part of an exposure system used for realizing a pattern formation method employing immersion lithography according to Embodiment 1 of the invention and FIG. <b>1B</b> schematically shows the plan structure of an air fan provided in the exposure system.

0049As shown in FIG. <b>1A,</b> the exposure system of Embodiment 1 includes an illumination optical system <b>50,</b> that is, an exposure section provided within a chamber 30, corresponding to a light source for exposing a design pattern on a resist film (not shown) applied on a wafer <b>40;</b> a projection lens <b>51</b> provided below the illumination optical system <b>50</b> for projecting, through an immersion liquid <b>42</b> onto the resist film, exposing light emitted from the illumination optical system <b>50</b> and entering through a mask (reticle) <b>41</b> having the design pattern to be transferred onto the resist film; and a first wafer stage <b>52A</b> for holding the wafer <b>40.</b> The projection lens <b>51</b> is held so as to be in contact with the surface of the immersion liquid <b>42</b> supplied onto the resist film formed on the wafer 40 during exposure.

0050The first wafer stage <b>52A</b> is held on a surface plate <b>53,</b> and the surface plate <b>53</b> has what is called twin stages in which a second wafer stage <b>52B</b> is provided on the side of the first wafer stage <b>52A.</b> The surface plate 53 may have three or more wafer stages.

0051As a characteristic of Embodiment 1, an air fan <b>54</b> corresponding to a drying section capable of blowing warm air is provided above the second wafer stage <b>52B</b> of the surface plate <b>53.</b>

0052FIG. <b>1B</b> is a plan view of the air fan <b>54.</b> As shown in FIG. <b>1B,</b> a draft port <b>54a</b> in the shape of a slit penetrating the air fan <b>54</b> in the vertical direction and an exhaust port <b>54b</b> extending in parallel to the draft port <b>54a</b> are provided on the top face of the air fan <b>54.</b> Although not shown in the drawing, the exhaust port <b>54b</b> is communicated with another exhaust port for discharging the air to the outside of the chamber <b>30.</b>

0053It is not always necessary to provide the air fan <b>54</b> above the second wafer stage <b>52B</b> but it may be provided on the side of the second wafer stage <b>52B</b> (the surface plate <b>53)</b> so that the air can blow from the side of the wafer <b>40</b> along a direction substantially parallel to the principal surface. Alternatively, it is not always necessary to provide the air fan <b>54</b> within the chamber <b>30</b> but it may be provided outside the chamber <b>30.</b>

0054Now, a pattern formation method using the exposure system of FIGS. <b>1A</b> and <b>1B</b> will be described with reference to FIGS. <b>2A</b> through <b>2C, 3A</b> and <b>3B.</b>

0055First, a positive chemically amplified resist material having the following composition is prepared: <tables id="tabl0002" num="0002"><table frame="none"><tgroup cols="2" colsep="0" rowsep="0"><colspec colnum="1" colname="col1" colwidth="151mm" colsep="0" /><colspec colnum="2" colname="col2" colwidth="15mm" colsep="0" /><tbody><row><entry namest="col1" nameend="col1" align="left" valign="top">Base polymer: poly((norbornene-5-methylene-t-butylcarboxylate) (50 mol%) - (maleic anhydride) (50 mol%))</entry><entry namest="col2" nameend="col2" align="left" valign="top">2 g</entry></row><row><entry namest="col1" nameend="col1" align="left" valign="top">Acid generator: triphenylsulfonium triflate</entry><entry namest="col2" nameend="col2" align="left" valign="top">0.06 g</entry></row><row><entry namest="col1" nameend="col1" align="left" valign="top">Quencher: triethanolamine</entry><entry namest="col2" nameend="col2" align="left" valign="top">0.002 g</entry></row><row><entry namest="col1" nameend="col1" align="left" valign="top">Solvent: propylene glycol monomethyl ether acetate</entry><entry namest="col2" nameend="col2" align="left" valign="top">20 g</entry></row></tbody></tgroup></table></tables>

0056Next, as shown in FIG. <b>2A,</b> the aforementioned chemically amplified resist material is applied on a wafer <b>40</b> so as to form a resist film <b>43</b> with a thickness of 0.35 µm.

0057Then, as shown in FIG. <b>2B,</b> with an immersion liquid <b>42</b> of water provided between the resist film <b>43</b> and a projection lens <b>51,</b> pattern exposure is carried out by irradiating the resist film <b>43</b> through a mask (not shown) with exposing light <b>44</b> of ArF excimer laser with NA of 0.68.

0058After discharging the liquid <b>42</b> from above the resist film <b>43,</b> the wafer <b>40</b> is moved to be positioned below the air fan <b>54</b> of FIG. <b>1A.</b> Thereafter, the top face of the resist film <b>43</b> is exposed to the warm air of a temperature of approximately 35°C as shown in FIG. <b>2C,</b> thereby drying drops of the liquid remaining on the top face of the exposed resist film <b>43.</b>

0059Next, as shown in FIG. <b>3A,</b> the resist film <b>43,</b> whose surface has been dried after the exposure, is baked with a hot plate at a temperature of 105°C for 60 seconds, and thereafter, the resultant resist film <b>102</b> is developed with a 0.26 N tetramethylammonium hydroxide aqueous solution (alkaline developer). In this manner, a resist pattern 43b made of an unexposed portion of the resist film <b>43</b> and having a line width of 0.09 µm is formed as shown in FIG. <b>3B.</b>

0060In this manner, according to the pattern formation method of Embodiment 1, after the pattern exposure through the immersion liquid <b>42,</b> the drops remaining on the resist film 43 are dried and removed by using the warm air, and therefore, the resist film <b>43</b> can be prevented from being deteriorated by the drops after the exposure. Accordingly, degradation of the pattern shape derived from insufficient dissolution in the developer of an exposed portion <b>43a</b> of the resist film <b>43</b> or unwanted dissolution of the unexposed portion can be prevented, resulting in obtaining the resist pattern <b>43b</b> in a good shape.

0061The temperature of the warm air blown by the air fan <b>54</b> is preferably, for example, not less than room temperature (23°C) and not more than 60°C, which does not limit the invention.

EMBODIMENT 2

0062Now, a pattern formation method according to Embodiment 2 of the invention will be described with reference to FIGS. <b>4A</b> through <b>4C, 5A</b> and <b>5B.</b>

0063First, a positive chemically amplified resist material having the following composition is prepared: <tables id="tabl0003" num="0003"><table frame="none"><tgroup cols="2" colsep="0" rowsep="0"><colspec colnum="1" colname="col1" colwidth="151mm" colsep="0" /><colspec colnum="2" colname="col2" colwidth="15mm" colsep="0" /><tbody><row><entry namest="col1" nameend="col1" align="left" valign="top">Base polymer: poly((norbornene-5-methylene-t-butylcarboxylate) (50 mol%) - (maleic anhydride) (50 mol%))</entry><entry namest="col2" nameend="col2" align="left" valign="top">2 g</entry></row><row><entry namest="col1" nameend="col1" align="left" valign="top">Acid generator: triphenylsulfonium triflate</entry><entry namest="col2" nameend="col2" align="left" valign="top">0.06 g</entry></row><row><entry namest="col1" nameend="col1" align="left" valign="top">Quencher: triethanolamine</entry><entry namest="col2" nameend="col2" align="left" valign="top">0.002 g</entry></row><row><entry namest="col1" nameend="col1" align="left" valign="top">Solvent: propylene glycol monomethyl ether acetate</entry><entry namest="col2" nameend="col2" align="left" valign="top">20 g</entry></row></tbody></tgroup></table></tables>

0064Next, as shown in FIG. <b>4A,</b> the aforementioned chemically amplified resist material is applied on a wafer (substrate) <b>101</b> so as to form a resist film <b>102</b> with a thickness of 0.35 µm.

0065Then, as shown in FIG. <b>4B,</b> with an immersion liquid <b>103</b> of water provided between the resist film <b>102</b> and a projection lens 105, pattern exposure is carried out by irradiating the resist film <b>102</b> through a mask (not shown) with exposing light <b>104</b> of ArF excimer laser with NA of 0.68.

0066Next, as shown in FIG. <b>4C,</b> after discharging the liquid <b>103</b> from above the resist film <b>102,</b> the wafer <b>101</b> is moved to be placed in a dehumidification vessel <b>110</b> provided with a drying agent <b>111</b> such as desiccant. At this point, the inside atmosphere of the dehumidification vessel <b>110</b> is dehumidified by the drying agent <b>111</b> contained therein, and therefore, drops of the liquid remaining on the top face of the exposed resist film <b>102</b> are dried.

0067Next, as shown in FIG. <b>5A,</b> the resist film <b>102,</b> whose surface has been dried after the exposure, is baked with a hot plate at a temperature of 105°C for 60 seconds, and thereafter, the resultant resist film <b>102</b> is developed with a 0.26 N tetramethylammonium hydroxide aqueous solution (alkaline developer). In this manner, a resist pattern <b>102b</b> made of an unexposed portion of the resist film <b>102</b> and having a line width of 0.09 µm is formed as shown in FIG. <b>5B.</b>

0068In this manner, according to the pattern formation method of Embodiment 2, after the pattern exposure through the immersion liquid <b>103,</b> the remaining drops on the resist film 102 are dried through the dehumidification, and therefore, the resist film <b>102</b> can be prevented from being deteriorated by the drops after the exposure. Accordingly, degradation of the pattern shape derived from insufficient dissolution in the developer of an exposed portion <b>102a</b> of the resist film <b>102</b> or unwanted dissolution of the unexposed portion can be prevented, resulting in obtaining the resist pattern <b>102b</b> in a good shape.

0069The drying agent <b>111</b> is not limited to the desiccant. Also, the dehumidification means is not limited to the drying agent <b>111,</b> but for example, a compressor system in which moisture vapor within an atmosphere is set by using a cooler containing a refrigerant may be used for the dehumidification.

EMBODIMENT 3

0070Now, a pattern formation method according to Embodiment 3 of the invention will be described with reference to FIGS. <b>6A</b> through <b>6C, 7A</b> and <b>7B.</b>

0071First, a positive chemically amplified resist material having the following composition is prepared: <tables id="tabl0004" num="0004"><table frame="none"><tgroup cols="2" colsep="0" rowsep="0"><colspec colnum="1" colname="col1" colwidth="151mm" colsep="0" /><colspec colnum="2" colname="col2" colwidth="15mm" colsep="0" /><tbody><row><entry namest="col1" nameend="col1" align="left" valign="top">Base polymer: poly((norbornene-5-methylene-t-butylcarboxylate) (50 mol%) - (maleic anhydride) (50 mol%))</entry><entry namest="col2" nameend="col2" align="left" valign="top">2 g</entry></row><row><entry namest="col1" nameend="col1" align="left" valign="top">Acid generator: triphenylsulfonium triflate</entry><entry namest="col2" nameend="col2" align="left" valign="top">0.06 g</entry></row><row><entry namest="col1" nameend="col1" align="left" valign="top">Quencher: triethanolamine</entry><entry namest="col2" nameend="col2" align="left" valign="top">0.002 g</entry></row><row><entry namest="col1" nameend="col1" align="left" valign="top">Solvent: propylene glycol monomethyl ether acetate</entry><entry namest="col2" nameend="col2" align="left" valign="top">20 g</entry></row></tbody></tgroup></table></tables>

0072Next, as shown in FIG. <b>6A,</b> the aforementioned chemically amplified resist material is applied on a wafer (substrate) <b>201</b> so as to form a resist film <b>202</b> with a thickness of 0.35 µm.

0073Then, as shown in FIG. <b>6B,</b> with an immersion liquid <b>203</b> of water provided between the resist film <b>202</b> and a projection lens <b>205,</b> pattern exposure is carried out by irradiating the resist film <b>202</b> through a mask (not shown) with exposing light <b>204</b> of ArF excimer laser with NA of 0.68.

0074Next, as shown in FIG. <b>6C,</b> after discharging the liquid <b>203</b> from above the resist film <b>202,</b> the wafer <b>201</b> is moved to be positioned in a warming vessel 210 in which the atmosphere is warmed to approximately 33°C. Thus, drops of the liquid remaining on the top face of the exposed resist film <b>202</b> are dried through warming.

0075Next, as shown in FIG. <b>7A,</b> the resist film <b>202,</b> whose surface has been dried after the exposure, is baked with a hot plate at a temperature of 105°C for 60 seconds, and thereafter, the resultant resist film <b>202</b> is developed with a 0.26 N tetramethylammonium hydroxide aqueous solution (alkaline developer). In this manner, a resist pattern <b>202b</b> made of an unexposed portion of the resist film <b>202</b> and having a line width of 0.09 µm is formed as shown in FIG. <b>7B.</b>

0076In this manner, according to the pattern formation method of Embodiment 3, after the pattern exposure through the immersion liquid <b>203,</b> the drops remaining on the resist film <b>202</b> are dried through the warming, and therefore, the resist film <b>202</b> can be prevented from being deteriorated by the drops after the exposure. Accordingly, degradation of the pattern shape derived from insufficient dissolution in the developer of an exposed portion <b>202a</b> of the resist film <b>202</b> or unwanted dissolution of the unexposed portion can be prevented, resulting in obtaining the resist pattern <b>202b</b> in a good shape.

0077As the means for warming the exposed resist film <b>202,</b> for example, a heater provided within the warming vessel <b>210</b> may be used. Alternatively, the warming vessel <b>210</b> for warming the wafer <b>201</b> is not always necessary as far as the temperature of the atmosphere covering the resist film <b>202</b> can be, for example, not less than room temperature (23°C) and not more than 60°C, which does not limit the invention.

0078Although a positive resist is used in each of Embodiments 1 through 3, the present invention is applicable to a negative resist.

0079Although water is used as the immersion liquid in each embodiment, perfluoropolyether may be used instead of water. Moreover, a surfactant may be added to the immersion liquid.

0080Although the ArF excimer laser is used as the exposing light for the pattern exposure in each embodiment, KrF excimer laser, Xe₂ laser, F₂ laser, KrAr laser, Ar₂ laser or the like may be used instead.

0081As described so far, according to the exposure system and the pattern formation method of this invention, a resist can be prevented from being deteriorated by an immersion liquid remaining on the resist, and hence, a resist pattern can be formed in a good shape. Thus, the invention is useful as, for example, an exposure system and a pattern formation method using the same for use in fabrication process or the like for semiconductor devices.