JP5086149B2 - Microstructure fabrication method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a manufacturing method of a microstructure by which a high resolution is achieved without deteriorating flexibility. <P>SOLUTION: Firstly, a negative type resist 102 is applied to a substrate 101 as shown in Fig. 1(b). Next, the negative type resist 102 is irradiated with an electron beam (corresponding to an energy beam) 103 with a first pattern as shown in Fig. 1(c) (first exposure step). Subsequently the negative type resist 102 is developed so as to form a block-shaped resist 102A (corresponding to a first structure) as shown in Fig. 1(d) (first development step). Subsequently the block-shaped resist 102A is irradiated with the electron beam 103 with a second pattern different from the first pattern as shown in Fig. 1(e) (second exposure step). Finally, the block-shaped resist 102A is developed so as to form a resist 102B with a shape of three orthogonally-crossed nanowires (corresponding to a second structure) as shown in Fig. 1(f) (second development step). <P>COPYRIGHT: (C)2010,JPO&amp;INPIT

Description

  The present invention relates to a fine structure manufacturing method, and more particularly to a fine structure manufacturing method using a lithography technique used in the field of semiconductor manufacturing.

  Conventionally, a fine structure is produced using the following lithography technique. First, a resist sensitive to an energy beam is applied on the substrate. Next, the resist is irradiated with an energy beam in a desired pattern. Subsequently, it develops using a developing solution and obtains the fine structure of a resist. As the energy beam, various types such as light, ultraviolet ray, X-ray, electron beam, ion beam and the like are used. In the semiconductor manufacturing field, a semiconductor circuit is manufactured by transferring the manufactured microstructure to a substrate. For details, refer to Non-Patent Document 1, for example.

  In recent years, for the purpose of application to various nanotechnology fields including a nanoelectromechanical system (NEMS), a three-dimensional ultrafine structure (hereinafter referred to as “three-dimensional nanostructure”) using the above-described lithography technology. Production technology is attracting attention. For example, Non-Patent Documents 2 and 3 disclose techniques for producing a three-dimensional nanostructure by performing electron beam irradiation (exposure) on a positive resist from a plurality of directions and then developing the positive resist. . Further, it is described that a deep and fine structure can be produced by repeating exposure and development a plurality of times.

  With reference to FIG. 5, such a three-dimensional nanostructure fabrication method will be described. First, a positive resist 502 is applied on the substrate 501 ((b)). Next, a desired first pattern is drawn on the resist 502 using the electron beam 503 ((c)), and then development is performed ((d)). Next, a second pattern different from the first pattern is drawn on the resist 502A obtained by development ((e)) and developed to produce a resist 502B having a three-dimensional nanostructure. FIG. 6 is a cross-sectional view taken along the line VI-VI in FIG. Since the irradiation direction of the electron beam 503 is different between the first pattern and the second pattern, sufficient positional accuracy is required for drawing the pattern. This method is disclosed in detail in Patent Document 1, If it is a contractor, it is applicable.

JP 2005-85984 A Edited by Soichiro, “Semiconductor Lithography Technology”, Sangyo Tosho, 1984 Technical Digest of 17th International Conference on Micro Electro Mechanical Systems, IEEE, 2004, p. 609 Japanese Journal of Applied Physics, 2004, Vol. 43, p. L1111

  However, the conventional three-dimensional nanostructure fabrication method as described above has a problem in resolution. As is known as a proximity effect in the electron beam lithography technique, electrons are scattered in the resist and the substrate during electron beam writing. Therefore, when exposure and development are repeated when a positive resist is used, the positive resist is slightly exposed over a certain wide area, and the resolution is lowered. Although it is conceivable to reduce the number of drawing operations in order to maintain high resolution, this reduces the degree of freedom of the three-dimensional nanostructure that can be fabricated. In lithography using a positive resist, the minimum size of the structure (“residual resolution”) produced by the method of leaving the part not irradiated with the energy beam after development is reduced to the minimum size of the space to be removed after development (“extracted”). There is also a problem that it is generally very difficult to reduce the resolution compared to “resolution”).

  Also, in lithography technology using a negative resist, a method of repeating exposure and development to obtain a fine structure is not effective. This is because the portion remaining in the first exposure and development remains in the subsequent development due to the nature of the negative type. Therefore, when a negative resist is used, the degree of freedom of a three-dimensional nanostructure that can be manufactured is reduced.

  The present invention has been made in view of such problems, and an object of the present invention is to provide a method for manufacturing a fine structure that realizes high resolution without impairing the degree of freedom.

  In order to achieve such an object, according to a first aspect of the present invention, in the fine structure manufacturing method using a negative resist, the negative resist is irradiated with an energy beam in a first pattern. An exposure step, a first developing step of developing the negative resist to form a negative resist of a first structure, and an energy beam applied to the first resist of the first structure A second exposure step of irradiating with a second pattern different from the above, and a second development step of developing the negative resist having the second structure by developing the negative resist having the first structure. It is characterized by that.

  According to a second aspect of the present invention, in the first aspect, the developing property of the development in the second developing step is adjusted to be higher than the developing property of the developing in the first developing step. Features.

  According to a third aspect of the present invention, in the first or second aspect, the energy absorption amount of the negative resist by irradiation of the first exposure step is the same as that of the second development step. The energy absorption amount that dissolves in development, and the energy absorption amount of the negative resist by irradiation in the second exposure step is the energy absorption amount that the negative resist remains in the development in the second development step. It is characterized by being.

  According to a fourth aspect of the present invention, in the second or third aspect, the developability of the first and second development steps is normalized by the total energy absorption amount of the negative resist on the horizontal axis and the vertical axis. The negative resist having the remaining film thickness has a total energy absorption region where the sensitivity curve is 1 and 0.

  According to a fifth aspect of the present invention, in any one of the first to fourth aspects, before the first exposure step, one or a plurality of sets of exposure and development are performed on the positive resist to form a positive type. The method further comprises the steps of: producing a resist mold; and applying the negative resist to be exposed in the first exposure step to the positive resist mold. The method for producing a microstructure according to any one of claims 1 to 4.

  According to a sixth aspect of the present invention, in the fifth aspect of the present invention, the positive resist mold is dissolved in the first structure before the second development step. The method further includes a step of removing from the negative resist.

  The invention described in claim 7 is characterized in that, in claim 2, the developability is adjusted by the strength of solubility of the developer in the resist or the length of the development time.

  The invention according to claim 8 is the invention according to claim 7, wherein the negative resist is hydrogenated silsesquioxane, and the developability is adjusted by the solubility of the developer in the resist, The developer in the first development step is an aqueous tetramethylammonium hydroxide solution, and the developer in the second development step is an aqueous potassium hydroxide solution.

  According to the present invention, by using the negative resist, the portion irradiated with the energy beam remains as a structure, so that the minimum dimension of the remaining fine structure can be made smaller than when the positive resist is used. In addition, since a plurality of exposures and developments are possible even using a negative resist, a high resolution can be realized without impairing the degree of freedom as compared with the conventional method.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
(Definition of terms)
As used herein, “resist” refers to a mixed material containing a polymer as a main component. It has photosensitivity to light, radiation, etc., and causes changes in physical properties due to chemical changes such as decomposition and crosslinking. It has etching resistance and is used for ultra-fine processing technology such as devices. The specific material composition differs depending on the radiation quality (ultraviolet ray, X-ray, electron beam, synchrotron radiation, ion beam, excimer laser, etc.) of the exposure source.

  The “negative resist” used in this specification refers to a resist having a characteristic that an exposed portion remains after development.

  Further, the “positive resist” used in the present specification refers to a resist having a characteristic that an exposed portion is dissolved and removed after development and an unexposed portion remains.

(Embodiment 1)
FIG. 1 is a diagram for explaining a fine structure manufacturing method according to Embodiment 1 of the present invention. First, as shown in FIG. 1B, a negative resist 102 is applied to the substrate 101. Next, as shown in FIG. 1C, the negative resist 102 is irradiated with an electron beam (corresponding to an energy beam) 103 in a first pattern (first exposure step). Next, as shown in FIG. 1D, the negative resist 102 is developed to form a block-like (corresponding to the first structure) resist 102A (first development step). Then, as shown in FIG. 1E, the block-shaped resist 102A is irradiated with the electron beam 103 in a second pattern different from the first pattern (second exposure step). Finally, as shown in FIG. 1F, the block-like resist 102A is developed to form three orthogonal nanowire-like (corresponding to the second structure) resists 102B (second development step). Since the irradiation direction of the electron beam 103 is different between the first pattern and the second pattern, sufficient positional accuracy is required for drawing the pattern. However, this method is disclosed in detail in Patent Document 1, If it is a contractor, it is applicable.

  As the negative resist 102, a hydrogenated silsesquioxane (hereinafter referred to as “HSQ”) resist or the like can be used.

  For the first development, a 2.38% tetramethylammonium hydroxide aqueous solution (hereinafter referred to as “TMAH aqueous solution”) or the like was used, and for the second development, a 20% potassium hydroxide aqueous solution (hereinafter referred to as “KOH aqueous solution”). Etc.) can be used. The developability of the first and second developments can be adjusted by adjusting the affinity (solubility) between the developer and the resist, or by adjusting the development time.

  FIG. 2 is a diagram for explaining a sensitivity curve of a negative resist. When an HSQ resist having a thickness of 100 nm applied on a silicon substrate is developed with a TMAH aqueous solution or a KOH aqueous solution, the residual film thickness is normalized with the initial film thickness (hereinafter referred to as “residual film thickness”) and irradiation. It is a graph showing the relationship with the dose amount of an electron beam with an acceleration voltage of 70 kV, and is called a sensitivity curve. The horizontal axis may be the total energy absorption amount of the negative resist obtained from the dose amount of the electron beam and the acceleration voltage.

As can be seen from the graph, the developability of the aqueous KOH solution, which is the developer used in the second development, is higher than the developability at the same dose amount of the TMAH aqueous solution, which is the developer used in the first development. It can be seen that when the dose amount is in the range of about 1000 to 3000 μC / cm ² , the development with the aqueous KOH solution is completely developed (dissolved), but the development with the aqueous TMAH solution is not completely developed (dissolved). Therefore, in the first exposure, drawing is performed with a dose amount of 1000 to 3000 μC / cm ² , and in the second exposure, writing is performed with a higher dose amount (for example, 10,000 μC / cm ² ). A block-shaped resist is formed, and three orthogonal nanowire portions remain in the second development. That is, the developability and the dose amount are the energy absorption amount of the negative resist by the first exposure, the energy absorption amount by which the negative resist dissolves in the second development, and the energy of the negative resist by the second exposure. The amount of absorption may be such that the negative resist remains the amount of energy absorbed in the second development.

  In particular, the developability of the first and second developments is such that there is a region of the total energy absorption amount where the sensitivity curve of the negative resist becomes 0 and 1, so that the resist portion that is dissolved by the first development is dissolved. And the resist portion dissolved by the second development can be separated with high accuracy. Such development can be adjusted by using different developers for the first development and the second development, or by using the same developer and increasing the development time in the second development. it can.

  In the fine structure manufacturing method according to this embodiment, since the portion irradiated with the energy beam remains as a structure by using a negative resist, the minimum size of the remaining fine structure can be made smaller than when a positive resist is used. In addition, since a plurality of exposures and developments are possible even using a negative resist, a high resolution can be realized without impairing the degree of freedom as compared with the conventional method.

  Although an electron beam is used as the energy beam, other types of energy beams may be used. Moreover, although the case where a three-dimensional nanostructure was produced was shown, you may produce a two-dimensional structure. Moreover, although the case where the irradiation direction of the energy beam is only three directions (X, Y, Z directions) orthogonal to the substrate has been shown, various other directions may be used.

  The above description is merely an example, and various existing methods in lithography technology including the type of resist, the type of solution such as a developer, and the selection of the number of repetitions of energy beam irradiation and development, etc. According to the embodiment, a desired fine structure can be manufactured with high accuracy. A specific combination may be selected in accordance with the resolution of the target structure, the shape of the structure, the type of energy beam, and the like.

  Also, if the sensitivity curve is expressed such that the remaining film thickness is 1 or 0, it is not intended to be exactly 1 or 0, but for most purposes it is 5-10. It should be understood that there is no problem even if there is an error of about%, so that the accuracy is of this level.

(Embodiment 2)
The fine structure manufacturing method according to the second embodiment is different from the first embodiment in that a template is manufactured using a positive resist before applying a negative resist. A negative resist is filled in a positive resist mold, and the exposure and development described in the first embodiment are performed a plurality of times on the negative resist, thereby reducing the minimum dimension of the three-dimensional nanostructure without impairing the degree of freedom. The size can be reduced, that is, the resolution can be increased.

  A method for producing a positive resist mold will be described with reference to FIG. First, as shown in FIG. 3B, a positive resist 302 is applied to the substrate 301. Next, as shown in FIG. 3C, the positive resist 302 is irradiated with an electron beam 303 in a first pattern. Next, as shown in FIG. 3D, the positive resist 302 is developed to form a block-like resist 302A having fine holes. Then, as shown in FIG. 3E, the block-shaped resist 302A is irradiated with an electron beam 303 in a second pattern different from the first pattern. Finally, as shown in FIG. 3F, the block-shaped resist 302A is developed to form a resist 302B having a three-dimensional hole as a template.

  As the positive resist 302, a polymethyl methacrylate (hereinafter referred to as “PMMA”) resist can be used.

  The first and second developments can be performed using a developer obtained by diluting methyl isobutyl ketone with isopropyl alcohol.

  Next, with reference to FIG. 4, a method for manufacturing a microstructure using a mold will be described. First, as shown in FIG. 4A, a negative resist 402 is applied to a substrate 301 and filled with a mold 302B. Next, as shown in FIG. 4C, the negative resist 402 is irradiated with an electron beam 403 in a first pattern. The first pattern is preferably in the vicinity of the region where the mold 302B exists. Next, as shown in FIG. 4C, the negative resist 402 is developed to form a resist 402A that is buried in a three-dimensional hole of the mold 302B. Then, as shown in FIG. 4D, the resist 402A is irradiated with an electron beam 403 in a second pattern different from the first pattern. Here, the second pattern does not need to match the position of the hole in the mold 302B, and may be designed according to a desired structure. Next, as shown in FIG. 4E, after the laminated substrate 404 is laminated, the mold 302B is dissolved using a positive resist developer (such as a solvent obtained by diluting methyl isobutyl ketone with isopropyl alcohol). However, the substrate 301 is removed from the negative resist 402A. The negative resist 402A having the structure shown in FIG. 4F is obtained in this way. Finally, the resist 402A is developed for the second time to dissolve unnecessary portions, thereby forming a negative resist 402B having a three-dimensional nanostructure. This is a structure in which only the portion subjected to the second exposure (see FIG. 4D) remains.

  As the negative resist 402, an HSQ resist or the like can be used. When an HSQ resist is used, methyl isobutyl ketone is preferably used as the solvent. Since this solvent has excellent wettability with respect to a positive resist such as a PMMA resist, it is well filled in the three-dimensional hole of the mold 302B.

  As described in the first embodiment, the developability of the negative resist is adjusted by adjusting the affinity (solubility) between the developer and the resist or the length of the development time.

6 is a diagram for explaining a manufacturing method of a microstructure according to Embodiment 1. FIG. It is a figure for demonstrating the sensitivity curve of a negative resist. 6 is a view for explaining a method for producing a positive resist mold according to Embodiment 2. FIG. 6 is a diagram for explaining a method for manufacturing a microstructure using a mold according to Embodiment 2. FIG. It is a figure for demonstrating the conventional three-dimensional nanostructure preparation method. It is a figure for demonstrating the conventional three-dimensional nanostructure preparation method.

Explanation of symbols

101 Substrate 102 Negative resist 102A First structure negative resist 102B Second structure negative resist 103 Electron beam (corresponding to energy beam)
301 Substrate 302 Positive resist 302A First structure positive resist 302B Second structure positive resist (corresponding to mold)
303 Electron beam (corresponding to energy beam)
402 Negative resist 402A First type negative resist 402B Second structure negative resist 403 Electron beam (corresponding to energy beam)
404 Bonded substrate

Claims (8)

In a method for producing a fine structure using a negative resist,
A first exposure step of irradiating a negative resist with an energy beam in a first pattern;
A first developing step of developing the negative resist to form a negative resist of a first structure;
A second exposure step of irradiating the negative resist having the first structure with an energy beam in a second pattern different from the first pattern;
And a second developing step of developing the negative resist of the first structure to form a negative resist of the second structure.   The method for producing a microstructure according to claim 1, wherein the developability of the development in the second development step is adjusted to be higher than the developability of the development in the first development step. The energy absorption amount of the negative resist due to the irradiation in the first exposure step is an energy absorption amount at which the negative resist is dissolved in the development of the second development step,
2. The energy absorption amount of the negative resist due to irradiation in the second exposure step is an energy absorption amount remaining in the development of the second development step. 3. A method for producing a microstructure according to 2.   The developability of the first and second development steps is such that the negative resist has a sensitivity curve of 1 and the horizontal axis represents the total energy absorption amount of the negative resist and the vertical axis represents the normalized residual film thickness. 4. The method for producing a fine structure according to claim 2, wherein a region having a total energy absorption amount of 0 exists. Before the first exposure step,
Performing one or more sets of exposure and development on the positive resist to produce a positive resist mold;
5. The fabrication of a fine structure according to claim 1, further comprising: applying the negative resist that is exposed in the first exposure step to the positive resist mold. Method. Before the second development step,
6. The method for producing a microstructure according to claim 5, further comprising the step of dissolving the positive resist template to remove the positive resist template from the negative resist of the first structure. .   The method for producing a microstructure according to claim 2, wherein the developability is adjusted by the strength of solubility of the developer in the resist or the length of the development time. The negative resist is silsesquioxane hydride,
The developability is adjusted by the strength of solubility of the developer in the resist,
The developer in the first development step is a tetramethylammonium hydroxide aqueous solution,
The method for producing a microstructure according to claim 7, wherein the developer in the second development step is an aqueous potassium hydroxide solution.

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