JP2005150182A - Method of forming pattern - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To realize good forming of a resist pattern obtained by an electron beam (EB) exposure having a low accelerating voltage. <P>SOLUTION: A resist film 102 is formed on a substrate 101, and a pattern exposure to the formed resist film 102 is performed through a mask 103 by the first electron beam 104 having the accelerating voltage of 10 keV or lower. Then, the entire surface of the pattern exposed resist film 102 is irradiated with a second electron beam 105 having smaller accelerating voltage and electron energy than those of the first electron beam 104. Thereafter, a heating treatment (PEB) is performed to the resist film 102 irradiated with the first electron beam 104 and a second electron beam, and the resist pattern 102a is formed from the resist film 102 by developing. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a pattern forming method used in a manufacturing process of a semiconductor integrated circuit device.

  Along with the large integration of semiconductor integrated circuits and downsizing of semiconductor elements, acceleration of development of lithography technology is desired. At present, patterns are formed by optical lithography using a mercury lamp, KrF excimer laser, ArF excimer laser, or the like as exposure light, but lithography using electron beams is expected for further miniaturization in the future. Has been.

  Electron beam lithography can achieve higher resolution than conventional methods using light as a light source for exposure, but has a problem in that throughput is small. A method for solving this is a batch transfer method using a mask, and an electron beam using an electron beam having a low acceleration voltage, for example, 10 keV or less, so as to prevent degradation of resolution due to Coulomb repulsion of the electron beam. Lithography has been proposed (see, for example, Non-Patent Document 1). According to the electron beam lithography using the electron beam with the low acceleration voltage, it is possible to improve the throughput and form a good pattern.

  Hereinafter, a pattern forming method using an electron beam with a low acceleration voltage will be described with reference to FIGS. 9 (a) to 9 (d).

  First, a positive chemically amplified resist material having the following composition is prepared.

Poly ((1-ethoxyethylstyrene) (40mol%)-(hydroxystyrene) (60mol%)) (base polymer) ………………………………………………………… ……………… 2g
Triphenylsulfonium trifluoromethanesulfonic acid (acid generator) ... 0.1g
Propylene glycol monomethyl ether acetate (solvent) ……………… 20g
Next, as shown in FIG. 9A, the chemically amplified resist material is applied onto the substrate 1 to form a resist film having a thickness of 50 nm.

  Next, as shown in FIG. 9B, pattern exposure is performed by irradiating the resist film 2 with an electron beam 4 having an acceleration voltage of 2 keV through a mask 3 having a design pattern.

Next, as shown in FIG. 9C, the resist film 2 subjected to pattern exposure is heated for 60 seconds at a temperature of 100 ° C. with a hot plate, and then 2.38 wt% tetramethylammonium hydroxide. When development is performed with a side developer (alkaline developer), a resist pattern 2a composed of an unexposed portion of the resist film 2 is obtained as shown in FIG.
H. Nakano et al., "Imaging Capability of Low-Energy Electron-Beam Proximity-Projection Lithography Toward the 70nm Node", Proc.SPIE, Vol.4754, 827 (2002). JP-A-7-78756

  However, since the pattern forming method by electron beam lithography shown in Non-Patent Document 1 uses an electron beam having a low acceleration voltage, as shown in FIG. 9D, the obtained resist pattern 2a is There is a problem that the edge roughness of the line becomes large and the edge shape becomes defective.

  Specifically, the edge roughness of the line of the pattern 2a is as large as 12 nm (3σ: where σ is a standard deviation). This is considered to be due to the large forward scattering of the electron beam in the electron beam exposure using the electron beam 4 whose acceleration voltage is as low as 2 keV.

  When etching a film to be processed using a resist pattern having a large roughness, the shape of the roughness is reflected in the film to be processed, resulting in a defective pattern shape. There arises a problem that productivity and yield in the manufacturing process of the semiconductor device are lowered.

  In view of the above, an object of the present invention is to improve the shape of a resist pattern obtained by electron beam exposure with a low acceleration voltage.

  The inventors of the present application have repeatedly investigated the cause of the increase in edge roughness of the resist pattern obtained by electron beam exposure with a low acceleration voltage, and as a result, the electron beam with a low acceleration voltage has the number of electrons necessary for pattern resolution. Because of the tendency to be insufficient, the roughness at the edge of the resulting resist pattern increases, and the electrons irradiated with low energy collide with other atoms in the resist film, so that the propulsive force of the electrons has Since it is weakened relatively easily, it has been considered that the resist film cannot be diffused in a uniform state.

  The present invention has been made on the basis of the above-mentioned knowledge, and the acid necessary for resolving the pattern is replenished before or after pattern exposure, and the acid dissolved in the developer is sufficiently contained in the exposed portion of the resist film. The distribution of electrons that are generated and supplied to the exposed part before development is supplied to the pattern surface in a relatively uniform state even at the edge of the pattern, thereby making the pattern surface uneven, particularly at the edge part of the resist pattern. It is possible to reduce the edge roughness composed of steps generated in the shape. That is, since a relatively uniform amount of electrons is supplied to the end portion of the exposed portion, sufficient acid can be spread from the center portion to the end portion of the exposed portion during development. Specifically, it is realized by the following method.

  The pattern forming method according to the present invention includes a step of forming a resist film on a substrate, a step of performing pattern exposure on the resist film with a first electron beam having an acceleration voltage of 10 keV or less, and an entire surface of the resist film. A step of irradiating the second electron beam, and a first heat treatment for the first electron beam and the resist film irradiated with the second electron beam, and then developing the resist film to develop a resist from the resist film. And a step of forming a pattern.

  According to the pattern forming method of the present invention, the resist film is irradiated with the second electron beam on the entire surface of the resist film, in addition to performing pattern exposure with the first electron beam having an acceleration voltage of 10 keV or less. Since the electrons necessary for resolving the pattern are replenished by the irradiation of the electron beam of 2, the acid dissolved in the developer is sufficiently generated at the exposed portion of the resist film. As a result, the edge roughness of the resist pattern can be reduced, and the resulting resist pattern has a good shape.

  In the pattern forming method of the present invention, the step of irradiating the second electron beam can be performed after the step of performing pattern exposure with the first electron beam.

  In this case, in the pattern forming method of the present invention, the resist film is subjected to the second heat treatment after the step of performing pattern exposure with the first electron beam and before the step of irradiating the second electron beam. It is preferable to further include a step of performing. In this way, the degree of diffusion of the acid generated in the resist film in the resist film can be adjusted.

  In the pattern forming method of the present invention, the step of irradiating the second electron beam can be performed before the step of performing pattern exposure with the first electron beam.

  In this case, in the pattern forming method of the present invention, the second heating is performed on the resist film after the step of irradiating the second electron beam and before the step of performing the pattern exposure with the first electron beam. It is preferable to further include a process for performing the treatment. In this way, the degree of diffusion of the acid generated in the resist film in the resist film can be adjusted.

  In the pattern forming method of the present invention, the acceleration voltage of the second electron beam is preferably equal to or smaller than the acceleration voltage of the first electron beam.

  In the pattern forming method of the present invention, the energy of the second electron beam is preferably equal to or smaller than the energy of the first electron beam.

  According to the pattern forming method of the present invention, the edge roughness in the resist pattern obtained by electron beam exposure with a low acceleration voltage can be reduced, that is, the edge shape can be made good, and the resulting resist pattern has a good shape. As a result, a good fine pattern can be obtained.

(First embodiment)
A pattern forming method according to the first embodiment of the present invention will be described with reference to FIGS. 1 (a) to 1 (d) and FIG.

  First, a positive chemically amplified resist material having the following composition is prepared.

Poly ((1-ethoxyethylstyrene) (40mol%)-(hydroxystyrene) (60mol%)) (base polymer) ………………………………………………………… ……………… 2g
Triphenylsulfonium trifluoromethanesulfonic acid (acid generator) ... 0.1g
Propylene glycol monomethyl ether acetate (solvent) ……………… 20g
Next, as shown in FIG. 1A, the chemically amplified resist material is applied on the substrate 101 to form a resist film having a thickness of 50 nm.

Next, as shown in FIG. 1B, the first electron beam 104 having an acceleration voltage of 2 keV and energy of 0.8 μC / cm ² is applied to the resist film 102 through a mask 103 having a desired design pattern. Pattern exposure is performed by irradiation.

Next, as shown in FIG. 1C, the entire surface of the resist film 102 subjected to pattern exposure is irradiated with a second electron beam 105 having an acceleration voltage of 1.5 keV and an energy of 0.5 μC / cm ² . .

  Next, as shown in FIG. 1D, the resist film 102 subjected to pattern exposure with the first electron beam 104 and overall irradiation with the second electron beam 105 is heated at a temperature of 100 ° C. by a hot plate. And then developing with a 2.38 wt% tetramethylammonium hydroxide developer (alkaline developer), as shown in FIG. A resist pattern 102a having a line width of 09 μm and a good shape is obtained.

  According to the first embodiment, after performing pattern exposure with the first electron beam 104 having an acceleration voltage of 2 keV, the second electron beam 105 having an acceleration voltage of 1.5 keV is applied to the entire surface of the resist film 102. The resist film 102 is replenished with electrons necessary for pattern resolution by the entire irradiation of the second electron beam 105. For this reason, since the acid which melt | dissolves in a developing solution generate | occur | produces sufficiently in the exposure part in the resist film 102, the edge roughness of the resist pattern 102a can be made small. For example, the obtained resist pattern 102a has a favorable shape because the edge roughness of the line is as small as 3 nm (3σ).

  Note that the irradiation amount (exposure amount) of the entire irradiation of the resist film 102 by the second electron beam 105 needs to be set to a level that does not exceed the dissolution threshold of the resist film 102 by the developer.

  In the first embodiment, the acceleration voltage of the first electron beam 104 for pattern exposure of the resist film 102 is preferably 10 keV or less. In this case, the second electron electron beam 104 is replenished with the second exposure electron. The acceleration voltage and electron energy in the electron beam 105 are preferably equal to or smaller than the acceleration voltage and electron energy in the first electron beam 104.

(Second Embodiment)
A pattern forming method according to the second embodiment of the present invention will be described with reference to FIGS. 3 (a) to 3 (d), 4 (a) and 4 (b).

  First, a positive chemically amplified resist material having the following composition is prepared.

Poly ((1-ethoxyethylstyrene) (40mol%)-(hydroxystyrene) (60mol%)) (base polymer) ………………………………………………………… ……………… 2g
Triphenylsulfonium trifluoromethanesulfonic acid (acid generator) ... 0.1g
Propylene glycol monomethyl ether acetate (solvent) ……………… 20g
Next, as shown in FIG. 3A, the chemically amplified resist material is applied on the substrate 201 to form a resist film having a thickness of 50 nm.

Next, as shown in FIG. 3B, the first electron beam 204 having an acceleration voltage of 2 keV and energy of 0.8 μC / cm ² is applied to the resist film 202 through a mask 203 having a desired design pattern. Pattern exposure is performed by irradiation.

  Next, as shown in FIG. 3C, the resist film 202 subjected to pattern exposure with the first electron beam 204 is subjected to a first heat treatment at a temperature of 100 ° C. for 60 seconds with a hot plate. Do.

Next, as shown in FIG. 3D, a second electron beam 205 having an acceleration voltage of 1.5 keV and energy of 0.5 μC / cm ² is formed on the entire surface of the resist film 202 subjected to the first heat treatment. Irradiate.

  Next, as shown in FIG. 4A, a second heat treatment is performed for 60 seconds at a temperature of 100 ° C. with a hot plate on the resist film 202 that has been irradiated with the second electron beam 205 over the entire surface. Thereafter, when development is performed with a 2.38 wt% tetramethylammonium hydroxide developer (alkaline developer), as shown in FIG. A resist pattern 202a having a line width of 09 μm and a good shape is obtained.

  According to the second embodiment, after performing pattern exposure with the first electron beam 204 having an acceleration voltage of 2 keV, the first post-exposure bake is performed, and then the acceleration voltage is 1.V over the entire surface of the resist film 202. A second electron beam 205 of 5 keV is irradiated, and a second post exposure bake is performed. For this reason, the resist film 202 is replenished with electrons necessary for pattern resolution by the entire irradiation of the second electron beam 205. For this reason, since the acid which melt | dissolves in a developing solution generate | occur | produces sufficiently in the exposure part in the resist film 202, the edge roughness of the resist pattern 202a can be made small. In addition, since post-exposure baking is performed each time the first and second electron beams 204 and 205 are irradiated, the degree of diffusion of the acid generated from the acid generator in the exposed portion of the resist film 202 in the resist film 202. Can be adjusted. As a result, the obtained resist pattern 202a is further reduced in edge roughness of the line to 2.5 nm (3σ) and has a good shape.

  Note that the irradiation amount (exposure amount) of the entire irradiation of the resist film 202 by the second electron beam 205 needs to be set to a level that does not exceed the dissolution threshold of the resist film 202 by the developer.

  In the second embodiment, the acceleration voltage of the first electron beam 204 for pattern exposure of the resist film 202 is preferably 10 keV or less. In this case, the second electron electron beam 204 is replenished with the second exposure electron. The acceleration voltage and electron energy in the electron beam 205 are preferably equal to or smaller than the acceleration voltage and electron energy in the first electron beam 204.

(Third embodiment)
A pattern forming method according to the third embodiment of the present invention will be described with reference to FIGS. 5 (a) to 5 (d) and FIG.

  First, a positive chemically amplified resist material having the following composition is prepared.

Poly ((1-ethoxyethylstyrene) (40mol%)-(hydroxystyrene) (60mol%)) (base polymer) ………………………………………………………… ……………… 2g
Triphenylsulfonium trifluoromethanesulfonic acid (acid generator) ... 0.1g
Propylene glycol monomethyl ether acetate (solvent) ……………… 20g
Next, as shown in FIG. 5A, the chemically amplified resist material is applied onto the substrate 301 to form a resist film having a thickness of 50 nm.

Next, as shown in FIG. 5B, the entire surface of the formed resist film 302 is irradiated with a first electron beam 305 having an acceleration voltage of 1.5 keV and energy of 0.5 μC / cm ² .

Next, as shown in FIG. 5C, the second electron beam having an acceleration voltage of 2 keV and energy of 0.8 μC / cm ² is applied to the resist film 302 irradiated with the first electron beam 305 on the entire surface. Pattern exposure is performed by irradiating 304 through a mask 303 having a desired design pattern.

  Next, as shown in FIG. 5D, the resist film 302 subjected to the entire surface irradiation with the first electron beam 305 and the pattern exposure with the second electron beam 304 is heated at a temperature of 100 ° C. with a hot plate. And then developing with a 2.38 wt% tetramethylammonium hydroxide developer (alkaline developer), as shown in FIG. A resist pattern 302a having a line width of 09 μm and a good shape is obtained.

  According to the third embodiment, first, after irradiating the entire surface of the resist film 302 with the first electron beam 305 having an acceleration voltage of 1.5 keV, pattern exposure is performed with the second electron beam 304 having an acceleration voltage of 2 keV. Therefore, the resist film 302 is replenished with electrons necessary for pattern resolution by the entire irradiation of the first electron beam 305. For this reason, since the acid which melt | dissolves in a developing solution generate | occur | produces sufficiently in the exposure part in the resist film 302, the edge roughness of the resist pattern 302a can be made small. For example, the obtained resist pattern 302a has a favorable shape because the edge roughness of the line is as small as 3 nm (3σ).

  Note that the irradiation amount (exposure amount) of the entire irradiation of the resist film 302 by the first electron beam 305 needs to be set so as not to exceed the dissolution threshold value of the resist film 302 by the developer.

  In the third embodiment, the acceleration voltage of the second electron beam 304 for pattern exposure of the resist film 302 is preferably 10 keV or less. In this case, the first electron beam 304 supplemented with the exposure electrons of the second electron beam 304 is used. The acceleration voltage and electron energy in the electron beam 305 are preferably equal to or smaller than the acceleration voltage and electron energy in the second electron beam 304.

(Fourth embodiment)
A pattern forming method according to the fourth embodiment of the present invention will be described with reference to FIGS. 7 (a) to 7 (d), FIG. 8 (a), and FIG. 8 (b).

  First, a positive chemically amplified resist material having the following composition is prepared.

Poly ((1-ethoxyethylstyrene) (40mol%)-(hydroxystyrene) (60mol%)) (base polymer) ………………………………………………………… ……………… 2g
Triphenylsulfonium trifluoromethanesulfonic acid (acid generator) ... 0.1g
Propylene glycol monomethyl ether acetate (solvent) ……………… 20g
Next, as shown in FIG. 7A, the chemically amplified resist material is applied onto the substrate 401 to form a resist film having a thickness of 50 nm.

Next, as shown in FIG. 7B, the entire surface of the formed resist film 402 is irradiated with a first electron beam 405 having an acceleration voltage of 1.5 keV and energy of 0.5 μC / cm ² .

  Next, as shown in FIG. 7C, the first heat treatment is performed on the resist film 202 irradiated with the first electron beam 405 at a temperature of 100 ° C. for 60 seconds with a hot plate. Do.

Next, as shown in FIG. 7D, a second electron beam having an acceleration voltage of 2 keV and energy of 0.8 μC / cm ² is applied to the resist film 402 irradiated with the entire surface of the first electron beam 405. Pattern exposure is performed by irradiating 404 through a mask 403 having a desired design pattern.

  Next, as shown in FIG. 8A, the resist film 402 subjected to the entire surface irradiation with the first electron beam 405 and the pattern exposure with the second electron beam 404 is heated at a temperature of 100 ° C. by a hot plate. Then, after performing the second heat treatment for 60 seconds, development is performed with 2.38 wt% tetramethylammonium hydroxide developer (alkaline developer), as shown in FIG. A resist pattern 402a having a good shape and a line width of 0.09 μm is obtained.

  According to the fourth embodiment, first, the first electron beam 405 having an acceleration voltage of 1.5 keV is irradiated over the entire surface of the resist film 402, and then the first post-exposure baking is performed. Pattern exposure with the first electron beam 204 of 2 keV is performed, and second post-exposure baking is performed. For this reason, the resist film 402 is supplemented with electrons necessary for pattern resolution by the entire irradiation of the first electron beam 405. For this reason, since the acid which melt | dissolves in a developing solution generate | occur | produces sufficiently in the exposure part in the resist film 402, the edge roughness of the resist pattern 402a can be made small. Moreover, since post-exposure baking is performed each time the first and second electron beams 405 and 404 are irradiated, the degree of diffusion of the acid generated from the acid generator in the exposed portion of the resist film 402 in the resist film 402. Can be adjusted. As a result, the obtained resist pattern 402a has an edge roughness of the line as small as 3 nm (3σ), and has a good shape.

  Note that the irradiation amount (exposure amount) of the entire irradiation of the resist film 402 by the first electron beam 405 needs to be set to a level that does not exceed the dissolution threshold of the resist film 402 by the developer.

  In the fourth embodiment, the acceleration voltage of the second electron beam 404 that pattern-exposes the resist film 402 is preferably 10 keV or less, and in this case, the first electron beam 404 is supplemented with the exposure electrons. The acceleration voltage and electron energy in the electron beam 405 are preferably equal to or smaller than the acceleration voltage and electron energy in the second electron beam 404.

  In each of the first to fourth embodiments, a positive chemically amplified resist material is used for the resist film, but the present invention is not limited to this.

  In addition, even in the case of a negative resist material in which the exposed portion of the resist film becomes insoluble in the developer due to a crosslinking reaction or the like by an electron beam, electrons are replenished in the exposed portion other than during pattern exposure. Since a crosslinking reaction or the like occurs sufficiently, the shape of the resist pattern formed of the exposed portion of the resist film can be improved.

  The pattern forming method according to the present invention has the effect that the edge roughness in the resist pattern obtained by electron beam exposure with a low acceleration voltage can be reduced and the edge shape can be improved, and in the manufacturing process of the semiconductor integrated circuit device This is useful as a pattern forming method to be used.

(A)-(d) is sectional drawing which shows each process of the pattern formation method which concerns on the 1st Embodiment of this invention. It is sectional drawing which shows 1 process of the pattern formation method which concerns on the 1st Embodiment of this invention. (A)-(d) is sectional drawing which shows each process of the pattern formation method which concerns on the 2nd Embodiment of this invention. (A) And (b) is sectional drawing which shows each process of the pattern formation method which concerns on the 2nd Embodiment of this invention. (A)-(d) is sectional drawing which shows each process of the pattern formation method which concerns on the 3rd Embodiment of this invention. It is sectional drawing which shows 1 process of the pattern formation method which concerns on the 3rd Embodiment of this invention. (A)-(d) is sectional drawing which shows each process of the pattern formation method which concerns on the 4th Embodiment of this invention. (A) And (b) is sectional drawing which shows each process of the pattern formation method which concerns on the 4th Embodiment of this invention. (A)-(d) is sectional drawing which shows each process of the conventional pattern formation method.

Explanation of symbols

101 substrate 102 resist film 102a resist pattern 103 mask 104 first electron beam 105 second electron beam 201 substrate 202 resist film 202a resist pattern 203 mask 204 first electron beam 205 second electron beam 301 substrate 302 resist film 302a Resist pattern 303 Mask 304 Second electron beam 305 First electron beam 401 Substrate 402 Resist film 402a Resist pattern 403 Mask 404 Second electron beam 405 First electron beam

Claims (7)

Forming a resist film on the substrate;
Performing a pattern exposure on the resist film with a first electron beam having an acceleration voltage of 10 keV or less;
Irradiating the entire surface of the resist film with a second electron beam;
Forming a resist pattern from the resist film by performing development after performing a first heat treatment on the resist film irradiated with the first electron beam and the second electron beam; A pattern forming method comprising:   2. The pattern forming method according to claim 1, wherein the step of irradiating the second electron beam is performed after the step of performing pattern exposure with the first electron beam.   The method further includes the step of performing a second heat treatment on the resist film after the step of performing pattern exposure with the first electron beam and before the step of irradiating the second electron beam. The pattern forming method according to claim 2, wherein:   2. The pattern forming method according to claim 1, wherein the step of irradiating the second electron beam is performed before the step of performing pattern exposure with the first electron beam.   The method further includes a step of performing a second heat treatment on the resist film after the step of irradiating the second electron beam and before the step of performing pattern exposure with the first electron beam. The pattern forming method according to claim 4.   The pattern forming method according to claim 1, wherein an acceleration voltage of the second electron beam is equal to or smaller than an acceleration voltage of the first electron beam. The pattern forming method according to claim 1, wherein the energy of the second electron beam is equal to or smaller than the energy of the first electron beam.

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