JP2007304579A - Forming method of resist pattern and writing method of charged particle beam - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a pattern forming method by which high dimensional accuracy is realized by shortening the effective acid diffusion length of a chemical amplification type resist without decreasing throughput of a writing system, and to provide a writing method of a charged particle beam. <P>SOLUTION: The forming method of a resist pattern is characterized in that in order to shorten the effective acid diffusion length of a chemical amplification type resist, the amount of an acid diffusion inhibitor is increased, and that in order to prevent throughput of a writing system from decreasing thereby, current density is increased. Specifically the forming method includes; a step of applying a chemical amplification type resist on a substrate surface to be processed; a step of patternwise irradiating the substrate with a charged particle beam; a step of heat-treating the chemical amplification type resist; and a step of developing the patternwise irradiated chemical amplification type resist, wherein the amount of an acid diffusion inhibitor in the chemical amplification type resist is increased and current density for the irradiation with the charged particle beam is increased. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a method of forming a pattern on a resist, and more particularly to a method of forming a resist pattern using a charged particle beam resist and a charged particle beam drawing method.

  In recent years, with the improvement of the degree of integration of semiconductor devices, there is an increasing demand for improving the dimensional accuracy of patterns formed on substrates such as semiconductors. In order to meet this requirement, various attempts have been made such as shortening the wavelength of light used for exposure, charged particle beam exposure, improving resist materials, and optimizing lithography processes.

  In the manufacture of semiconductor devices, chemically amplified resists are widely used in lithography processes that form patterns on semiconductor substrates. In this chemically amplified resist, a photoacid generator is blended with the resist base polymer. The acid generated in the resist by exposure diffuses into the resist by heating after exposure, and this acid serves as a catalyst. Promotes resist solubilization or insolubilization reaction. The reaction between the acid catalyst and the resist generates an acid that acts as a catalyst for the solubilization or insolubilization reaction of the resist resin. Therefore, high-sensitivity and low-irradiation light or energy beam irradiation is expected to enable efficient lithography. be able to.

  As described above, in a pattern formation method using a chemically amplified resist, an acid is usually generated at a low dose, and in the subsequent heating step, the generated acid acts as a catalyst for solubilization or insolubilization of the resist resin. However, in the case of exposure with a low irradiation amount, the reaction site between the charged particles and the acid generator is sparse, so that the influence remains after the completion of the chemical amplification reaction, and the dimensional accuracy reaches its peak.

If the irradiation amount of the charged particle beam is increased, the probability of the reaction between the charged particle and the acid generator is improved, so that the dimensional accuracy can be improved. Increasing the irradiation time can be considered to increase the irradiation amount of the charged particle beam. However, increasing the irradiation time decreases the throughput of the drawing apparatus, and a solution to the problem has been demanded. .
JP 2003-140352 A

  The present invention has been made to solve the above-described problems in lithography using a charged particle beam, and shortens the effective diffusion distance of acid in a chemically amplified resist without increasing the throughput of the lithography apparatus. It is to provide a method capable of realizing dimensional accuracy.

  The first invention is to increase the amount of the acid diffusion inhibitor in order to shorten the effective acid diffusion distance in the chemically amplified resist, and to increase the current density in order to prevent a reduction in the throughput of the drawing apparatus due to this. It is characterized by.

  That is, the present invention includes a step of applying a chemically amplified resist on the surface of a substrate to be processed, a step of irradiating the substrate with a pattern using a charged particle beam, and a step of heat-treating the exposed chemically amplified resist. A resist pattern forming method comprising a step of developing the pattern-irradiated chemically amplified resist, wherein the chemically amplified resist contains an acid diffusion inhibitor.

  Further, the amount of the above acid diffusion inhibitor added is in the range of 0.01 to 30 mol% with respect to the photoacid generator (material that generates acid by light or charged particle beam irradiation) of the chemically amplified resist. It is preferable to obtain a pattern with high accuracy.

And in the above-mentioned charged particle beam irradiation process, it is preferable that the current density required to generate the charged particle beam to irradiate is in the range of 50 to 5000 A / cm ² .

  The charged particle beam is preferably an electron beam. Furthermore, it is preferable to use an alkaline developer in the developing step for developing the latent image formed on the resist.

  The second invention is a charged particle beam drawing method characterized in that mask drawing is performed using a chemically amplified resist containing an increased amount of acid diffusion inhibitor used in the first invention described above.

  According to the present invention, it is possible to form a pattern with high dimensional accuracy with a simple configuration without reducing the pattern formation throughput.

Hereinafter, the principle of the present invention will be described with reference to the drawings.
FIG. 1 is a conceptual diagram showing the principle of the present invention, and schematically shows a reaction caused by charged particle beam irradiation in a chemically amplified resist layer formed on a substrate to be processed. FIG. 1A shows a reaction in a resist layer obtained by adding an acid diffusion inhibitor to a conventional chemically amplified resist. In FIG. 1A, nine acid diffusion inhibitors exist in the charged particle beam irradiation region. Within this region, charged particle beams or secondary electrons react with the acid generator to generate one acid. (The black circles in FIG. 1 (a) represent the acid generated). This acid diffuses in the direction of the arrow in FIG. 1 by the subsequent PEB (Post Exposure Bake), but collides with the acid diffusion inhibitor mixed in the resist, and the acid is deactivated. The average diffusion distance until an acid is generated by irradiation with a charged particle beam and deactivated by collision with an acid diffusion inhibitor is indicated by a dotted circle in FIG. On the other hand, when the amount of the acid diffusion inhibitor in the present invention is increased (FIG. 1 (b)), a larger number of acid diffusion inhibitors exist than in the case of FIG. 1 (a). Therefore, the average diffusion distance of the acid generated by charged particle beam irradiation is shortened.

  FIG. 2A schematically shows the state in the resist when drawn with a chemically amplified resist containing a conventional normal amount of acid diffusion inhibitor. The acid indicated by the black circles generated by charged particles or secondary electrons in the shot indicated by the solid rectangular region in FIG. 2A reacts with a dissolution inhibitor or a crosslinking agent within the diffusion distance. As a result, after developing this irradiation pattern, a pattern is obtained in which circles of average diffusion radii indicated by dotted lines in the figure are connected by an envelope. That is, a pattern as shown in FIG. 2B is formed. In FIG. 2B, the solid line schematically depicts the pattern edge portion. The outer periphery of a circle with a large diameter is connected by an envelope, and the width ΔW1 of the unevenness at the edge portion is relatively large.

On the other hand, in FIG. 3 (a), which is the case of the present invention in which the amount of acid diffusion inhibitor is increased from the example shown in FIG. 2 (a), the amount of acid diffusion inhibitor is increased. The average diffusion distance of the acid generated by particle beam irradiation is shorter than that in the case of FIG. In the present invention, the irradiation amount per unit time of the charged particle beam is increased. Therefore, the probability of collision between the charged particle and the acid generator is increased, so that the generated acid is higher than in the case of FIG. The amount of is increasing. Therefore, as shown in FIG. 3 (a), the resist insolubilization or solubilization reaction occurs more densely than in the case of FIG. 2 (a) due to the charged particle irradiation of the present invention. The edge portion of FIG. 3 has a shape in which the outer circumferences of the dotted circles in FIG. 3A are connected by an envelope, and has an edge shape closer to the rectangular shape of the shot as compared with the case of FIG.
As shown in FIG. 2 where the pattern is formed using the conventional chemically amplified resist as shown in FIG. 3 and FIG. 3 where the pattern is formed under the conditions of the present invention, the width of the unevenness at the pattern edge portion is shown. ΔW1 and ΔW2 have a relationship of ΔW1> ΔW2, and it can be seen that the accuracy of the pattern is further improved in the present invention.

Hereinafter, the pattern forming method of the present invention using charged particles will be described.
The pattern forming method of this embodiment includes at least a chemically amplified resist coating process, a charged particle beam irradiation process, a PEB (post exposure bake) process, and a development process. If desired, a pre-baking step of removing the organic solvent from the chemically amplified resist coating layer can be performed between the chemically amplified resist coating step and the charged particle beam irradiation step. In addition, before the chemically amplified resist layer is formed on a substrate such as a semiconductor, a substrate surface cleaning step or a reflective film forming step on the substrate surface can be performed.
Hereinafter, this pattern forming method will be described step by step.

Chemical amplification resist coating process:
This step is a step of applying a chemically amplified resist on a substrate to be processed such as a semiconductor, glass, or ceramic.
In this resist coating process, a known apparatus such as a spin coater, an applicator, a bar coater, a spinner, or a curtain flow coater can be used.

As the chemically amplified resist material used in this step, a base resin having a compound polymerization inhibitor having an acid-decomposable group dissolved in an organic solvent can be used.
Chemically amplified resists include a positive type in which the charged particle irradiated portion is solubilized in the developer and a negative type in which the charged particle irradiated portion is insolubilized. Depending on whether the base resin is a positive type or a negative type, The resin materials that can be used are different.
As a positive resist, PMMA (polymethyl methacrylate) developed with a mixed solvent of MIBK (methyl isobutyl ketone) and isopropyl alcohol (IPA) is well known. The use of processes that emphasize the reduction of the burden on the environment is increasing, and the use of an alkali-solubilized resin resist is being carried out.
As the resist containing the alkali-solubilizing resin, a phenol resin, a novolac resin, a substituted polystyrene, or the like can be used.

  On the other hand, as an example of a negative resist, a compound that is cross-linked or polymerized by an acid and insolubilized in an alkaline developer can be used. Specifically, an alkyl etherified melamine resin, an alkyl etherified benzoguanamine resin, an alkyl Examples include etherified urea resins and alkyl ether group-containing phenolic compounds.

The types of acid generators include charged particle beam irradiation acid generators (usually known as photoacid generators (PAG)) that generate and separate acids by irradiation with charged particles, or generate acids by heating. Thermal acid generators are known. Examples of charged particle beam irradiation acid generators include bissulfoniudiazomethanes, nitrobenzyl derivatives, polyhydroxy compounds and aliphatic or aromatic sulfonates, onium salts, sulfonylcarbonylalkanes, sulfonylcarbonyldiazomethanes, halogens Compounds such as containing triazine compounds, oxime sulfonate compounds, phenylsulfonyloxyphthalimides can be used.
On the other hand, sulfonimide is known as a thermal acid generator. This sulfonimide produces an acid in the temperature range of 140-150 ° C.

  In the present invention, the acid generator is added in an amount of 0.1 to 30% by weight based on the total solid content of the resist. When the addition amount of the acid generator is below this range, the sensitivity of charged particle irradiation is lowered, and pattern formation becomes difficult. On the other hand, when the amount of the acid generator added exceeds this range, the attenuation of the charged particles becomes excessive, making it difficult to form a desired pattern.

  In the present invention, it is necessary to add an acid diffusion inhibitor to the chemically amplified resist material. An acid diffusion inhibitor prevents acid generated from an acid generator from excessively diffusing into a chemically amplified resist and deteriorating the pattern profile, and is usually an acid catalyst generated by charged particle beams. It is used by adding to a region that suppresses the action of. Specifically, when a resist coating film is irradiated with a charged particle beam, an acid diffusion inhibitor is used when excessive acid generation occurs at the resist / substrate interface due to reflection or scattering of the charged particle beam from the underlying substrate. Is used. In this case, since the catalytic action of the acid catalyst is inhibited by the addition of the acid diffusion inhibitor, the reaction between the resist and the substrate interface is lowered. Therefore, the addition amount of the acid diffusion inhibitor is determined in consideration of a pattern abnormality caused by charged particle beam irradiation when the acid diffusion inhibitor is not added.

  In the present invention, the addition amount of the conventional acid diffusion inhibitor is far beyond the range of addition amount. The addition amount in the present invention is preferably 2 to 10 times the normal use amount.

The addition amount of the acid diffusion inhibitor is preferably in the range of 0.01 to 30 mol% with respect to the photoacid generator of the chemically amplified resist.
In the present invention, as the acid diffusion inhibitor, an alkaline substance or a substance that generates an alkaline substance upon irradiation with a charged particle beam can be used.
Specific examples include tertiary amines, benzyl carbamates, benzoin carbamates, o-carbamoylhydroxyamines, o-carbamoyl oximes, dithiocarbamate quaternary ammonium salts and the like.

Pre-baking process:
Next, the substrate coated with the chemically amplified resist in the above step is pre-baked to remove volatile components such as a solvent present in the resist. Usually, it can be performed by heating at 80 to 140 ° C. for about 60 seconds for the wafer and about 10 minutes for the mask. Since the pH of the chemically amplified resist film affects the development characteristics of the chemically amplified resist, it is preferable that the environment atmosphere during the pre-bake treatment is an atmosphere that does not contain an acidic substance or an alkaline substance.

Charged particle beam irradiation process:
Next, a pattern is formed on the substrate using a charged particle exposure apparatus. The dissolution reaction or solidification reaction of the chemically amplified resist is caused by the acid generated by dissociation from the acid generator compounded in the chemically amplified resist by charged particles such as an electron beam (EB) irradiated to the chemically amplified resist. Arise. In the present invention, an example of an electron beam is described as the charged particle. However, in the present invention, the charged particle is not limited to the electron beam, but may cause a change in solubility in the chemically amplified resist material. For example, various ion beams may be used.

  As the charged particle beam irradiation apparatus, a known charged particle beam irradiation apparatus can be used as long as it can increase the current density of charged particles.

  Hereinafter, an irradiation apparatus using an electron beam as a charged particle beam, that is, an electron beam exposure apparatus will be schematically described with reference to the drawings.

FIG. 4 shows an example of an electron beam exposure apparatus that can be used in this embodiment. In FIG. 4, an electron beam exposure apparatus 10 includes an electron gun 12, a first lens 14 that shapes an electron beam emitted from the electron gun 12 into a desired shape, and a first shaping aperture (first aperture) 16. A second lens 18 and a second shaping aperture (second aperture) 20 for further shaping the electron beam, a reduction lens 22 for reducing the shape of the shaped electron beam, and an irradiation direction of the electron beam The electron beam is irradiated onto the substrate to be processed 26 through this deflector to form a pattern 30 on the resist layer on the surface.
Although not shown, the electron beam exposure apparatus 10 and the substrate to be processed 26 are accommodated in a casing that covers the whole, and the inside is kept in a vacuum. The operation of the entire apparatus is controlled by a control apparatus (not shown).
In this electron beam exposure apparatus, the current density is controlled by the electron gun 12 and the first lens 14.

In the present invention, an increased amount of an acid diffusion inhibitor is added as the chemically amplified resist. For this reason, diffusion of the acid generated by electron beam exposure is suppressed, so that the chemically amplified resist is dissolved or dissolved. Insolubilization reaction is inhibited. Therefore, in order to cause the desired dissolution or insolubilization reaction in the chemically amplified resist, it is necessary to increase the irradiation amount per unit area of the substrate to be processed.
By the way, the electron beam irradiation amount D is expressed as D = J · T, where J is the current density proportional to the electron beam amount, and T is the irradiation time T. Therefore, it can be seen that if the current density is increased, the irradiation dose can be improved without extending the irradiation time. Therefore, by increasing the current density for electron beam exposure from a predetermined setting value, the reaction can be achieved without increasing the irradiation time that affects the throughput of the pattern forming process.
The rate of increase in current density depends on the amount of acid diffusion inhibitor contained in the chemically amplified resist. If the amount of the acid diffusion inhibitor is an amount that halves the average diffusion distance of the acid, the current density is preferably about doubled.

PEB (Post Exposure Bake) process:
Next, post-exposure baking, which is a heat treatment after exposure, is performed. This step causes solubilization or insolubilization reaction of the chemically amplified resist. That is, the diffusion and catalytic action of the acid generated from the acid generator is manifested.
The baking temperature is preferably in the range of 70 ° C to 150 ° C. If the temperature is lower, the pattern shape deteriorates, which is inconvenient in that the resolution is insufficient.

Development process:
The development step is a step of developing the latent image formed on the resist on the substrate up to the previous step, and the resist layer is usually treated with an alkaline solution to remove the uncured portion of the resist. If the non-cured portion is a positive resist, it is a charged particle irradiated portion, and the resist in this portion becomes solvent-soluble and the resist is removed. On the other hand, in the case of a negative resist, on the contrary, the resist material in the irradiated portion is insolubilized due to a phenomenon such as cross-linking, and the resist in the non-irradiated portion is soluble.
As an ordinary developer, an alkaline solution such as tetramethylammonium hydroxide (TMAH) can be used.
Thereafter, the generated pattern can be dried to obtain a patterned substrate.

(Example 1)
A chromium layer film having a film thickness of 70 nm (700 mm) and a chromium oxide layer having a thickness of 30 nm (300 mm) were formed in this order on a glass substrate, thereby producing a 6-inch mask substrate.
90 parts by weight of a polyvinylphenol resin introduced with a substituent having a dissolution inhibiting effect on the side chain, 7 parts by weight of succinimidyl trifluoromethanesulfonate as an acid generator, and o-nitrobenzyl carbamate 6 as an acid diffusion inhibitor A part by weight was blended and dissolved in an organic solvent to form a chemically amplified resist.
The chemically amplified resist was applied to the surface of the substrate using a spin coater, and pre-baked at 110 ° C. for 600 seconds to form a resist layer having a thickness of 300 nm (3000 mm).
Next, using an electron beam exposure apparatus with an acceleration voltage of 50 kV, the pattern was exposed with an electron beam having a maximum beam size of 1 μm square. The irradiation amount was 20 μC / cm ² , and the current density was 100 A / cm ² . The pattern width was 500 nm and 100 nm.
Next, the substrate was placed on a hot plate, and the resist layer was heated at 120 ° C. for 900 seconds to form a latent image. Thereafter, development was performed for 60 seconds at a temperature of 23 ° C. using a 2.38 wt% aqueous solution of tetramethylammonium hydroxide (TMAH).

(Example 2)
Further, the amount of the acid diffusion inhibitor was increased to 12 parts by mass, and pattern formation was performed in the same manner as in Example 1.

(Comparative example)
As a comparative example, pattern formation was performed in the same manner as in the above example except that the amount of the acid diffusion inhibitor was 3 parts by weight.

(Evaluation)
With respect to the patterns obtained in Examples 1 and 2 and the comparative example, LCD (3σ) accuracy indicating the degree of variation in pattern dimensions was measured within a range of several tens of μm.
Similarly, the LER accuracy representing the degree of unevenness of the pattern edge was measured for one pattern.
The results are shown in Table 1.

FIG. 5 shows cross-sectional photographs of the resist patterns obtained by the above-described Example 1, Example 2, and Comparative Example.
The photomicrograph (a) shown in FIG. 5 is the cross section of the 500 nm pattern obtained in the comparative example, the photo (b) is the cross section of the 500 nm pattern obtained in Example 1, and the photo (c) is the example. The cross section of the 500 nm pattern obtained in Step 2, the photograph (d) is the cross section of the 100 nm pattern obtained in the comparative example, the photograph (e) is the cross section of the 100 nm pattern obtained in Example 1, and the photograph. (F) is a cross section of the 100 nm pattern obtained in Example 2.
As is apparent from the results of FIG. 5, as the amount of the acid diffusion inhibitor increases, the corner shape of the resist top becomes sharper, the trailing edge of the resist-substrate interface becomes smaller, and the constriction at the center of the resist is further reduced. Was found to be reduced. As a result, the fine pattern did not collapse in the pattern of the example, whereas the fine pattern of the comparative example had fallen.

  Thus, it became clear that the LCD accuracy and the LER accuracy were improved and the resist cross-sectional shape was improved as the amount of the diffusion inhibitor increased. Since the irradiation amount is increased by increasing the current density, it is clear that the pattern accuracy is improved without reducing the throughput of the drawing apparatus, and that the present invention has an excellent effect. is there.

It is a conceptual diagram which shows the principle of this invention. It is the conceptual diagram which represented typically the mode of reaction in the resist at the time of drawing with the conventional chemical amplification type resist. It is the conceptual diagram which represented typically the mode of reaction in the resist at the time of drawing with the chemically amplified resist of this invention. It is the schematic which shows an example of the electron beam exposure apparatus which can be used in this Embodiment. It is a cross-sectional shape shown in the microscope picture obtained by this invention Example and the comparative example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... EB exposure apparatus 12 ... Electron gun 14 ... 1st lens 16 ... 1st shaping | molding diaphragm (1st aperture)
18 ... second lens 20 ... second molded diaphragm (first aperture)
22 ... Reduction lens 24 ... Deflector 26 ... Substrate 28 ... Electron beam 30 ... Pattern

Claims (10)

Applying a chemically amplified resist to the substrate surface;
Irradiating the chemically amplified resist layer on the surface of the substrate to be processed with a charged particle beam;
Heat-treating the chemically amplified resist layer irradiated with the charged particle beam;
A resist pattern forming method comprising a step of patterning by performing development processing on the chemically amplified resist,
The method of forming a resist pattern, wherein the chemically amplified resist contains an acid diffusion inhibitor.   2. The resist pattern forming method according to claim 1, wherein the addition amount of the acid diffusion inhibitor is in the range of 0.01 to 30 mol% with respect to the acid generator of the chemically amplified resist. ^2. The resist pattern forming method according to claim 1, wherein a current density required to generate a charged particle beam to be irradiated in the charged particle beam irradiation step is in a range of 50 to 5000 A / cm ² .   The method for forming a resist pattern according to claim 1, wherein the amount of the acid generator added is in the range of 0.1 to 30 parts by weight with respect to the total solid content.   The acid diffusion inhibitor is selected from the group consisting of tertiary amines, benzyl carbamates, benzoin carbamates, o-carbamoyl hydroxyamines, o-carbamoyl oximes, and dithiocarbamate quaternary ammonium salts. The resist pattern forming method according to claim 1, wherein the resist pattern is formed.   2. The method of forming a resist pattern according to claim 1, wherein an alkaline developer is used in the developing step of developing the latent image formed on the resist.   A method of forming a resist pattern, wherein the step of irradiating the charged particle beam is performed using a charged particle beam exposure apparatus.   The method of forming a resist pattern according to claim 1, wherein the charged particle beam is an electron beam.   8. The method for forming a resist pattern according to claim 7, wherein the charged particle beam exposure apparatus is an apparatus capable of increasing a current density of an electron beam.     A charged particle beam drawing method, wherein mask drawing is performed using the chemically amplified resist according to claim 1.