JP4552326B2 - Fine pattern forming method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for forming a fine resist pattern in a photolithography process of a semiconductor manufacturing process.
[0002]
[Prior art]
In recent years, miniaturization of elements in various semiconductor devices has progressed, and further miniaturization is required for photolithography.
Therefore, as a miniaturization method that meets this demand, many proposals have been made for shortening the exposure wavelength, increasing the NA of the lens of the exposure apparatus, and optimizing the resist material.
As typical ones among them, for example, as described in JP-A-1-307228 and JP-A-7-45510, after formation of the unexposed portion resist pattern, a temperature equal to or higher than the resist softening point. Has been proposed (hereinafter referred to as a first conventional example) in which the pattern is refined by thermal flow of the resist.
Further, for example, as described in JP-A-6-250379, JP-A-7-13442, JP-A-10-73927, and JP-A-11-204399, the interface of the formed pattern is used. A method (hereinafter referred to as a second conventional example) has been proposed in which a frame size is reduced by chemical reaction.
[0003]
[Problems to be solved by the invention]
However, in the first conventional example described above, since all the resist patterns of the entire wafer are thermally flowed, there are problems such as shape distortion and poor dimensional controllability in an asymmetric pattern arrangement.
In particular, in a dense pattern with a narrow pitch, the volume of the resist material that flows relative to the unit volume of the resist material is smaller than that in the case of a sparsely arranged pattern, so that the amount of pattern deformation due to heat treatment is small.
That is, the deformation amount of the pattern due to the heat treatment varies due to the difference in density of the pattern, and it is difficult to control the reduction of the pattern size by the heat treatment, particularly in the case of the dense pattern.
[0004]
In the second conventional example described above, the chemical reaction at the interface, specifically, the acid remaining in the resist pattern is diffused by heat to cause a cross-linking reaction, thereby removing the unreacted portion, and by patterning the pattern. In order to reduce the size, the acid generation efficiency from the resist, the remaining amount, the diffusion efficiency, the crosslinking temperature, etc. vary depending on the type of resist material, that is, depending on the type of resist material, per unit interface area It is assumed that the acid concentration varies.
For this reason, the amount of size reduction differs depending on the area density of the pattern, and the finished size may vary, or there may be a reduction in size difference in the plane direction.
In any case, when forming a pattern such as a fine hole, groove, or ellipse, the above-described conventional method is effective in simply miniaturizing the pattern, but it is particularly effective in controlling the dimensions. There is a problem that a dimensional difference due to density dependence occurs.
[0005]
SUMMARY OF THE INVENTION An object of the present invention is to provide a fine pattern forming method capable of ensuring the controllability of pattern dimensions and controlling the pattern density dependency.
[0006]
[Means for Solving the Problems]
In order to achieve the above object, the present invention provides a first pattern comprising a repeated pattern or a plurality of patterns having different pattern densities by a photolithography technique using a photosensitive polymer material and a correction mask arranged on a substrate. And a second process for changing the pattern dimension to form a fine pattern with respect to the first pattern formed by the first process. .
[0007]
In the fine pattern forming method of the present invention, in the first process, a repetitive pattern or a plurality of patterns having different pattern densities are obtained by photolithography using a photosensitive polymer material and a correction mask arranged on a substrate. A first pattern made of a pattern is formed. The correction mask used in the first process is a mask having a mask pattern that takes into consideration the deformation characteristics of the fine pattern generated by the second process in advance. Next, in the second process, the pattern dimension is changed with respect to the first pattern formed by the first process to form a fine pattern. More specifically, the following first to fifth steps are performed. First, in the first step, a pattern made of a photosensitive polymer material is formed on the substrate by a photolithography technique using a mask before correction. Next, in the second step, an unreacted portion of the upper layer agent is removed after applying an upper layer agent containing a crosslinking agent on the substrate provided with the pattern formed in the first step and performing heat treatment. The frame is framed so as to narrow the opening width of the pattern. Further, in the third step, a correction mask in which the mask dimension is optimized based on the degree of deformation of the pattern by the frame formation in the second step is obtained. Next, in the fourth step, a pattern made of a photosensitive polymer material is formed on the substrate by a photolithography technique using the correction mask obtained in the third step. Thereafter, in the fifth step, by applying an upper layer agent containing a crosslinking agent on the substrate provided with the pattern formed in the fourth step and heat-treating the unreacted portion of the upper layer agent, The pattern is framed so as to narrow the opening width of the pattern. In the miniaturization process in the fourth step (corresponding to the second process) , deformations such as density dependency due to pattern arrangement and anisotropy of the dimensional reduction ratio due to pattern asymmetry occur, but the third step in advance . Since (corresponding to the first process) , the pattern (first pattern) is formed by the correction mask in consideration of the deformation characteristics due to such miniaturization. It is possible to obtain a fine pattern. Therefore, controllability of pattern dimensions can be ensured regardless of miniaturization, and density dependency can be controlled, and a more effective fine pattern can be obtained.
[0008]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of a fine pattern forming method according to the present invention will be described.
In the fine pattern forming method according to the present embodiment, after the first pattern is formed by the first process using the photolithography technique, the pattern placement is performed when the second process for further reducing the pattern dimension is performed. By forming the first pattern through the correction mask in which the difference in reduction size due to the density difference, asymmetry, and irregularity is added to the mask dimension in advance, the target dimension can be obtained regardless of the pattern density. Miniaturization is possible.
[0009]
In addition, as a second process, a heat treatment is performed on the formed pattern to flow, or a resin composition containing a cross-linking agent is applied to the formed pattern, and the chemical at the interface between the pattern and the upper layer film is applied. Adopt a process of framing by reaction.
Further, when the latter process of the second process is adopted, the acid contained in the resist pattern is diffused and the chemical reaction is utilized. Here, as a method for optimally quenching (removing) the excessively diffused acid, an additive for controlling the amount of acid generated due to the difference in pattern density and the diffusion length is used in the second process. It shall be included in the object beforehand.
Thereby, it is possible to reduce the variation in the size reduction amount regardless of the pattern arrangement or the asymmetric pattern.
[0010]
Specific examples of additives used in this embodiment include basic compounds, that is, ammonium compounds such as tetramethylammonium hydroxide, and amines such as n-hexylamine and aniline.
Moreover, one or more kinds of additives can be used in combination as these additives.
The selection and addition amount of such an additive may be appropriately determined according to the type, strength, diffusion length, and amount of acid generated from the formed resist pattern.
In addition, the pattern shape of the fine pattern is not limited to the hole shape (circular shape), and can correspond to various shapes such as an elliptical shape, a groove shape, or a different-diameter hole shape composed of a plurality of line segments. It is.
[0011]
Hereinafter, specific embodiments of the present invention will be described with reference to the drawings.
It should be noted that the contents shown in the drawings described below schematically show the dimensions, shapes, and arrangement relationships of the constituent components to the extent that the present invention can be understood, and are described in the following examples. The contents, for example, the material used, the amount used, the device used, the film thickness, the temperature, the time, and the like show one example of the present invention, and the present invention is not limited to these in a range not exceeding the gist.
Further, in the following examples, unless otherwise specified, it is assumed that handling of the photoresist solution after microfiltration and the process of execution contents are performed in a clean room of a yellow room where temperature and humidity are controlled.
[0012]
FIG. 1 is a flowchart showing an outline of a process flow in one embodiment of the present invention.
First, a procedure for creating a correction mask used in an actual process will be described.
In this operation, similarly to the actual process, a process for forming a first pattern by a photolithography technique or the like (first process) and a process for miniaturizing the first pattern (second process) are performed. Then, the deformation of the pattern accompanying the miniaturization is analyzed from the pattern obtained as a result, and a correction mask is created from the analysis result.
First, in the first process (step S1), a resist is applied to a substrate to be processed with a film thickness of 0.73 μm. Although a positive chemically amplified resist for KrF (acetal type) is used here, the present invention is not limited to this. That is, any resist material that causes heat flow or a chemically amplified resist can be used, and the exposure wavelength is not limited to KrF. Moreover, the baking temperature, heating temperature, and time which will be described later are not limited thereto. For resist application and development, for example, ACT8 manufactured by Tokyo Electron Limited is used.
[0013]
Next, a desired portion of the resist is selectively removed by a photolithography process to form a first pattern. At this time, the following steps are performed in this example.
First, after the above-described resist coating, the coated substrate is placed on a hot plate and prebaked for 1 minute at a heating temperature of 90 ° C. Next, for example, the exposure is performed at an exposure amount of 40 mJ / cm ² through a contact hole pattern mask by a KrF scanner (NSR-202A) manufactured by Nikon Corporation.
[0014]
Next, in the first process (step S2), a pattern is formed using a mask before correction (herein referred to as mask A).
FIG. 2A shows a specific example of a pattern using the mask A.
This mask A is a quadruple mask for hole formation, and the dimension on the mask is in the range of 0.48 to 1.2 μm, and the 16-row pattern with a pitch of 1: 0.5, 1: 1, 1: 2. A halftone mask having an array. The pattern shape on the mask is a square cut pattern.
Next, the substrate exposed through the mask A described above is placed on a hot plate, and a post-exposure bake treatment is performed at a heating temperature of 100 ° C. for 1 minute. Then, development is performed with a 2.38% tetramethylammonium hydroxide aqueous solution, and further rinse with pure water is performed to form a first pattern.
[0015]
Next, the process proceeds to the second process (step S3). This second process is a process of applying a heat treatment to the first pattern formed as described above (Step S4), or applying a resin composition containing a cross-linking agent to the formed pattern, A process (step S5) in which a frame is formed by a chemical reaction at the interface between the upper layer film and the upper layer film can be employed. Here, a case where both are performed in combination will be described.
In this process, first, as a heat treatment, the developed substrate is placed on a hot plate, and a post-bake treatment is performed at a heating temperature of 110 ° C. for 1 minute.
[0016]
In a normal case, for example, a resist pattern with a hole of 220 nm is formed for a design of 1 to 2 pitch corresponding to 260 nm. In this example, this pattern is set as sample 1 as a sample for judging the effect of the present invention.
Next, an upper layer agent of the water-soluble resin composition is further applied to the hole pattern as described above, and heat treatment is performed at soft baking at 85 ° C. for 70 seconds and mixing base at 90 ° C. for 90 seconds. Subsequently, for the purpose of removing the unreacted portion of the upper layer agent, rinsing is performed for 50 seconds using an aqueous rinse solution. Thereafter, post baking is performed at 100 ° C. for 90 seconds. In this way, a fine pattern is formed (step S6). The sample formed here is referred to as Sample 2.
FIG. 2B shows a specific example of a pattern obtained by such a second process.
[0017]
Next, the length measurement is performed by paying attention to the one-to-one finished pattern corresponding to 260 nm with the mask of sample 2.
Thereby, for example, it is assumed that the hole shape at both ends in 16 rows has been transformed into a vertically long ellipse. Further, it is assumed that the shape is changed from an ellipse to a circle as it enters from the end to the inside, and the circular diameter is finished at 140 nm for 1: 1 and 120 nm for 1: 1.
Therefore, optimization of mask dimension correction is performed based on such hole deformation degree and simulation studies. For example, a correction mask is obtained by applying necessary correction amounts to the mask A for each of the 16 end columns, the second column from the end, the remaining 12 central portions, and the 1: 1 and 1: 2 pitches. This is referred to as a mask B.
The correction method is not limited to the above procedure. If necessary, it can be further finely corrected, and the degree of correction may be small depending on the type of resist forming the first pattern.
[0018]
Next, using the correction mask B obtained as described above, first and second processes shown in steps S1 to S6 are performed. Note that the process of creating the first pattern using the correction mask B is the same as the process using the mask A described above, and a description thereof will be omitted.
A first pattern formed using such a correction mask B is referred to as sample 3.
In this sample 3, paying attention to the finished pattern of 1 to 1 and 1 to 2 corresponding to 260 nm, the length measurement was performed. As a result, in 1 to 1 and 1 to 2, all of the 16 rows were circular with 140 nm. It was found that a pattern was formed.
[0019]
Next, the above-described second process (steps S3 to S6) is performed through the correction mask B. And when performing this series of processes, what added the trace amount tetramethylammonium hydroxide is used for the upper layer agent of the water-soluble resin composition used by the process of step S5. This is for optimally quenching (removing) the acid that has diffused excessively among the acids contained in the resist material as described above.
A pattern obtained by such a second process is designated as sample 4.
[0020]
FIG. 3 is an explanatory diagram showing a dimensional comparison table for each of the samples 1 to 4 described above. FIG. 3A shows the dimensions when the mask A is used, and FIG. 3B uses the corrected mask B. Shows the case. In the figure, the horizontal axis indicates the position (first to 16th) from the left of each mask, and the vertical axis indicates the measured value (nm) of the finished dimension.
The solid line a shown in FIG. 3A is the measurement value of the sample 1, the broken line b is the measurement value of the sample 2 having a one-to-one pitch at the end of the second process, and the broken line c is 1 at the end of the second process. The measured value of sample 2 with 1 pitch is shown.
Also, the broken line d shown in FIG. 3B is a measured value of the sample 3 having a one-to-one pitch at the end of the second process, and a broken line e is a measured value of the sample 3 having a one-to-two pitch at the end of the second process. The solid line f indicates the measured value of Sample 4.
As shown in the drawing, when the correction mask B is used as compared with the case where the mask A is used, a fine pattern with small variations can be obtained without depending on the pattern density or the like.
That is, according to the fine pattern forming method according to the present embodiment, it is possible to form a fine pattern with reduced density dependency and the like. In particular, it is possible to realize the formation of holes in which a plurality of arrangement patterns having different densities, which are difficult to be miniaturized, exist in the same layer, and to realize the manufacture of a VLSI using photolithography.
[0021]
【The invention's effect】
As described above, in the fine pattern forming method of the present invention, a repetitive pattern or a plurality of patterns having different pattern densities are obtained by photolithography using a photosensitive polymer material and a correction mask arranged on a substrate. A first process for forming a first pattern, and a second process for changing a pattern dimension to form a fine pattern with respect to the first pattern formed by the first process.
Therefore, according to the present invention, when pattern miniaturization is performed, the controllability of pattern dimensions can be ensured, and the dependency on density can be controlled, and a more effective fine pattern can be obtained. Can do.
[Brief description of the drawings]
FIG. 1 is a flowchart showing an outline of a process flow in an embodiment of the present invention.
FIG. 2 is a schematic plan view showing an example of a pattern arrangement used in the process shown in FIG.
FIG. 3 is an explanatory diagram showing a dimension comparison table of each sample in each process when the process shown in FIG. 1 is applied.

Claims (3)

A first step of forming a pattern made of a photosensitive polymer material on a substrate by a photolithography technique using a mask before correction;
By applying an upper layer agent containing a crosslinking agent on the substrate provided with the pattern formed in the first step and performing heat treatment, the unreacted portion of the upper layer agent is removed, thereby narrowing the opening width of the pattern. A second step of framing the pattern,
A third step of obtaining a correction mask in which a mask dimension is optimized based on the degree of deformation of the pattern by the frame formation in the second step;
A fourth step of forming a pattern made of a photosensitive polymer material on the substrate by a photolithography technique using the correction mask obtained in the third step;
By applying an upper layer agent containing a crosslinking agent on the substrate provided with the pattern formed in the fourth step and performing heat treatment, the unreacted portion of the upper layer agent is removed, thereby narrowing the opening width of the pattern. And the fifth step of framing the pattern
A method for forming a fine pattern. The heat treatment in the second step is one time or a plurality of times of heat treatment.
The fine pattern forming method according to claim 1 . In the photolithography techniques of the first step and the fourth step, a positive chemically amplified resist is used as the photosensitive polymer material.
The method for forming a fine pattern according to claim 1 or 2.

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