JP2004029482A - Pattern formation method - Google Patents

Abstract

An object of the present invention is to provide a pattern forming method capable of obtaining a pattern having good line width accuracy with respect to a design value without depending on pattern density.
In a pattern forming method for performing pattern etching on a surface layer of a substrate 1 using a resist pattern as a mask, a pattern forming region on the surface of the substrate 1 is formed in a dense first region according to a pattern formation density. 2a and a sparse second area 2b. Thereafter, pattern etching using the resist pattern as a mask is performed on the first region 2a, and pattern etching using the resist pattern as a mask is performed on the second region 2b in a separate step.
[Selection diagram] Fig. 1

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a pattern forming method, and more particularly, to a pattern forming method suitable for manufacturing an exposure mask in which patterns are arranged with sparse and dense states.
[0002]
[Prior art]
2. Description of the Related Art In a manufacturing process of a semiconductor device, a microfabrication process for pattern-etching a substrate (semiconductor substrate) surface using a resist pattern as a mask is performed. Further, when the resist pattern is formed, pattern exposure using an exposure mask is performed, and when producing the exposure mask, fine processing of the surface of the substrate (mask substrate) using the resist pattern as a mask is also performed. A process is taking place.
[0003]
A microfabrication process using such a resist pattern as a mask is performed in the following procedure. First, a resist film is formed on a substrate, and pattern exposure (drawing exposure in the case of manufacturing an exposure mask) is performed on the resist film. After that, by performing a developing process on the resist film, only the exposed portions (or unexposed portions) are removed to obtain a resist pattern. Next, after performing the pattern etching of the substrate surface using this resist pattern as a mask, the resist pattern is peeled off, and the substrate is washed to complete the fine processing process.
[0004]
[Problems to be solved by the invention]
By the way, it is known that a pattern formed on a substrate surface by the above-described series of microfabrication processes varies in pattern line width depending on a pattern density on the substrate surface. FIG. 4 is a graph showing the pattern density dependence of the pattern line width, in which the pattern line width (vertical axis) is indicated by the amount of deviation from the design line width. Note that the pattern is a space-shaped punched pattern, and illustrates a case where a positive resist is used. As shown in this graph, the pattern formed on the substrate becomes thinner (shifts to the negative side) with respect to the design line width as the pattern density on the substrate becomes lower, while the pattern density on the substrate becomes denser. , There is a tendency that the width becomes larger (shifts to the + side) with respect to the design line width.
[0005]
The pattern density dependence of the pattern line width occurs due to a loading effect generated in a developing process and an etching process and a fogging (Fogging Effect) at the time of drawing exposure. Here, the loading effect means that the supply amount of the developing solution and the supply amount of the etching gas to each pattern forming portion differ depending on the pattern density, the dissolution rate of the resist in the developing process, and the etching in the pattern etching. This is a phenomenon in which the speed changes depending on the pattern density, thereby changing the pattern line width. This loading effect occurs in the range of several hundred μm to several cm. In addition, fogging is a phenomenon in which, at the time of writing using an electron beam, the amount of exposure changes due to the reflection of electrons at the interface of the resist film, and the line width increases particularly in a dense pattern area. The effect is in the range of cm.
[0006]
In recent years, the element structure of a semiconductor device has been miniaturized, and a fine pattern formation exceeding the resolution limit of exposure light has been required in the above-described fine processing process. For this reason, the line width variation as described above has an even greater effect on miniaturized patterns.
[0007]
In particular, when the fine pattern on the exposure mask has the line width variation as described above, exposure using this exposure mask makes it impossible to perform pattern exposure with good line width accuracy. As a result, in an exposed portion using a portion where the pattern line width is formed smaller than the design value, the exposure amount corresponding to this portion becomes insufficient, and the pattern formed on the substrate is likely to be disconnected. . On the other hand, in an exposed portion using a portion where the pattern line width is formed larger than the design value, a pattern having a line width larger than the design value is formed, so that a problem such as a short circuit between the patterns occurs. Easier to do.
[0008]
Therefore, an object of the present invention is to provide a pattern forming method capable of obtaining a pattern with good line width accuracy with respect to a design line width without depending on pattern density.
[0009]
[Means for Solving the Problems]
The pattern forming method of the present invention for achieving the above object is a pattern forming method of performing pattern etching on a surface layer of a substrate using a resist pattern as a mask. The method is characterized in that the pattern is divided into a plurality of regions corresponding to the pattern formation density, and thereafter, pattern etching is performed on each of the plurality of divided regions having the same pattern formation density. In each pattern etching, a resist pattern having a pattern in a region to be subjected to pattern etching and covering another region is used as a mask.
[0010]
In such a pattern formation method, pattern etching is performed on a pattern formation region on the substrate surface for each region divided according to the pattern formation density. For this reason, pattern etching is performed on each region without being affected by the difference in pattern formation density of each region, that is, the pattern density, and line width variation is performed on each region of the substrate surface. Thus, pattern formation with less noise is performed.
[0011]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the pattern forming method of the present invention will be described in detail with reference to the drawings. Here, as an example, an embodiment in which the present invention is applied to manufacture of an exposure mask used for manufacturing a semiconductor device, a micro machine, or the like will be described.
[0012]
First, the pattern formation region on the substrate surface is divided into a plurality of regions according to the pattern formation density. Here, as shown in FIG. 1 (2), based on the design data of the pattern formation region 2 on the substrate 1, the pattern formation region 2 is divided into a first region 2a having a dense pattern formation density and a first region 2a. It is divided into a second region 2b having a lower pattern formation density than that of the second region 2b. For example, when the exposure mask formed here is an exposure mask for forming a semiconductor device in which a DRAM and a Logic are mounted, a first region 2a in which a DRAM is formed and a second region 2b in which a Logic is formed. The pattern formation region 2 is divided.
[0013]
In addition to such division, a predetermined value is set for the pattern formation density, a region where the pattern formation density is higher (dense) than this predetermined value is defined as the first region 2a, and the other regions are defined as the second region. It may be divided as the area 2b. Further, the number of divisions of the pattern formation region 2 is not limited to the two-stage region of the first region 2a and the second region 2b, but may be three stages, four stages,... good. Furthermore, depending on the design layout, the first region 2a and the second region 2b may be provided in a plurality of divided locations.
[0014]
As described above, after the pattern formation region 1 is divided into a plurality of regions 2a and 2b, each of the regions 2a and 2b is individually subjected to pattern etching using a resist pattern as a mask.
[0015]
In this case, for example, as shown in FIG. 1B, pattern etching is first performed on one region (for example, the first region 2a) on the surface of the substrate 1, and a pattern for element formation (not shown) is formed on the first region 2a. ) Is formed. Further, by this pattern etching, an alignment pattern 3 is formed in addition to the pattern for element formation. The alignment pattern 3 is provided at a position which does not affect the pattern formation for element formation in each of the regions 2a and 2b. For example, for example, near four sides of the substrate 1 outside the first region 2a and the second region 2b Shall be formed. However, the position may be within the regions 2a and 2b as long as the position does not affect the formation of the element forming pattern.
[0016]
After the first pattern etching is completed as described above, pattern etching is performed only on the second region 2b on the substrate surface as shown in FIG. This pattern etching is performed in a state where it is aligned with the pattern formed in the first region 2a by using the alignment pattern 3 formed by the first pattern etching. The procedure of the alignment using the alignment marks will be described in detail below with reference to FIG.
[0017]
When the pattern formation region 2 is further divided into regions of a plurality of stages, after the pattern etching of the second region 2b is completed, the pattern formation region 2 is sequentially moved to another region (third region, fourth region...). Pattern etching. By using the alignment pattern 3, these pattern etchings are performed in a state where they are aligned with the element formation patterns in the other regions that have already been formed.
[0018]
Hereinafter, the detailed procedure of the pattern etching shown in FIGS. 1 (2) and 1 (3) will be described with reference to FIGS.
[0019]
First, as shown in FIG. 2A, a substrate (mask substrate) having a light-shielding film 1b made of chromium formed on a surface of, for example, a quartz substrate 1a is prepared as a substrate 1 for producing an exposure mask. Then, a positive resist film 5 is formed on the substrate 1. Then, drawing exposure for forming a functional pattern is performed on the resist film 5 on the first region 2a of the substrate 1 using, for example, an electron beam e. At this time, drawing exposure for irradiating an electron beam to a pattern formation portion is performed. Although illustration is omitted here, drawing for forming the alignment pattern described with reference to FIG. 1B is also performed in this drawing exposure.
[0020]
Next, as shown in FIG. 2B, the resist film 5 is subjected to a developing process to obtain a resist pattern 5a from which an electron beam irradiation portion has been removed. The resist pattern 5a has a space-shaped cutout pattern 5b on the first area 2a, has an alignment pattern forming pattern (not shown) around the areas 2a and 2b, and covers the second area 2b. It is formed into a shape.
[0021]
Next, as shown in FIG. 2C, pattern etching is performed on the light shielding film 1b constituting the surface layer of the substrate 1 by etching using the resist pattern 5a as a mask. As a result, a space-shaped cutout pattern P1 is formed in the light-shielding film 1b in the first region 2a, and an alignment pattern (not shown) is formed in the peripheral region.
[0022]
Thereafter, as shown in FIG. 2D, the resist pattern 5a is peeled off, and the substrate 1 is further washed to complete the first pattern etching.
[0023]
After the above, the steps described with reference to FIGS. 2A to 2D are repeatedly performed on the second region 2 b of the substrate 1.
[0024]
That is, first, as shown in FIG. 3A, a positive resist film 7 is formed on the substrate 1 on which the pattern P1 is formed in the first region 2a, and the positive resist film 7 is formed on the second region 2b of the substrate 1. Drawing exposure using, for example, an electron beam e is performed only on the resist film 7. Then, at the time of this drawing exposure, alignment using the above-described alignment pattern is performed. Here, by detecting an alignment pattern, a row is exposed at a predetermined position in the second area 2b while performing high-precision alignment with respect to the pattern P1 formed in the first area 2a. It is.
[0025]
Next, as shown in FIG. 3 (2), the resist film 7 is subjected to a developing process to obtain a resist pattern 7a from which an electron beam irradiation portion has been removed. The resist pattern 7a has a space-shaped cutout pattern 7b on the second region 2b and is formed in a shape that covers the first region 2a.
[0026]
Next, as shown in FIG. 3C, pattern etching is performed on the light shielding film 1b constituting the surface layer of the substrate 1 by etching using the resist pattern 7a as a mask. As a result, a space-shaped cutout pattern P2 is formed in the light shielding film 1b in the second region 2b.
[0027]
Thereafter, as shown in FIG. 4D, the resist pattern 7a is peeled off, and then the substrate 1 is washed to complete the second pattern etching. Thus, an exposure mask 10 having the pattern P1 in the first region 2a and the pattern P2 in the second region 2b is obtained.
[0028]
If the pattern formation region on the surface of the substrate 1 is further divided into a plurality of regions, after the pattern etching of the second region 2b is completed, other regions (third region, fourth region. 3), the steps described with reference to FIGS. 3A to 3D are repeatedly performed.
[0029]
In the pattern forming method of the embodiment described above, pattern etching is performed for each of the regions 2a and 2b divided according to the pattern formation density. Therefore, the pattern etching is performed on each of the regions 2a and 2b without being affected by the pattern formation density difference between the regions 2a and 2b, that is, the pattern density. It is possible to form a pattern with a small line width variation on the regions 2a and 2b.
[0030]
Therefore, even in a design layout in which pattern density exists, it is possible to obtain the exposure mask 10 in which the design line width is maintained with high accuracy in all regions without depending on the pattern density. As a result, using this exposure mask 10, it is possible to perform high-precision lithography without disconnection or short circuit of the pattern. Further, the yield of the exposure mask can be improved.
[0031]
Note that, in the above-described embodiment, the case where a space-shaped cutout pattern is formed using a positive resist has been described, but the present invention is not limited to this.
[0032]
For example, in the case of forming a space-shaped punched pattern using a negative resist, the drawing exposure described with reference to FIGS. Is performed in the same manner as the above-described pattern forming procedure, except that exposure light such as an electron beam e is applied to all the portions.
[0033]
Further, when a convex residual pattern is formed by using a positive resist, only the first region 2a excluding the pattern forming portion is used in the drawing exposure described with reference to FIG. Exposure light such as an electron beam e is irradiated on the second region 2b except for the pattern forming portion during the drawing exposure described with reference to FIG. Except for irradiating exposure light, the same procedure as described above for pattern formation is performed.
[0034]
In the case where a convex residual pattern is formed using a negative resist, the pattern forming portion of the first region 2a and the second region 2b are formed in the drawing exposure described with reference to FIG. Is exposed to the exposure light such as the electron beam e, and the pattern exposure portion of the second region 2b and the entire first region 2a are formed at the time of the drawing exposure described with reference to FIG. Except for irradiating the region with exposure light such as an electron beam e, the procedure is the same as the above-described pattern formation procedure.
[0035]
Further, in the above-described embodiment, the embodiment in which the present invention is applied to the production of the exposure mask 10 in which the pattern of the light shielding film 1b made of chromium is provided on the quartz substrate 1a, that is, the so-called binary mask, has been described. However, the present invention is not limited to this, and Levenson-type phase shift masks, halftone-type phase shift masks, and even stencil masks and other patterns can be applied to the production of exposure masks. The effect of can be obtained. In particular, when the present invention is applied to the fabrication of a Levenson-type phase mask, variations in the etching depth of the quartz substrate due to the density of the pattern can be suppressed, so that the amount of phase shift in all regions is made uniform. be able to. However, when manufacturing a Levenson-type phase shift mask, pattern etching is performed twice on each of the regions 1a and 2b with different depths to shift the phase.
[0036]
In addition, the present invention is not limited to pattern formation for manufacturing an exposure mask, but is similarly applicable to a case where a pattern is formed on a silicon substrate, and similar effects can be obtained.
[0037]
【The invention's effect】
As described above, by adopting a configuration in which pattern etching is performed for each of the regions divided according to the pattern formation density, it is possible to form a pattern in which line width variation due to pattern density is suppressed. Therefore, it is possible to form a pattern in which the design line width is maintained with high accuracy in all regions without depending on the density of the pattern. As a result, in particular, by performing lithography using an exposure mask obtained by applying this pattern forming method, a fine pattern can be formed without causing disconnection or short circuit of the pattern.
[Brief description of the drawings]
FIG. 1 is a process chart showing a pattern forming method according to an embodiment.
FIG. 2 is a sectional process view (1) showing details of a pattern forming method of the embodiment.
FIG. 3 is a sectional process view (part 2) showing details of the pattern forming method of the embodiment;
FIG. 4 is a diagram showing a pattern formation density dependency of a line width variation of a pattern.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... board | substrate (mask substrate), 1a ... quartz substrate, 1b ... light shielding film, 2 ... pattern formation area, 2a ... 1st area (DRAM area), 2b ... 2nd area (Logic area), 5a, 7b resist pattern, P1, P2 ... pattern

Claims (3)

In a pattern forming method of performing pattern etching using a resist pattern as a mask on a surface layer of a substrate,
Dividing the pattern formation region on the substrate surface into a plurality of regions according to the pattern formation density;
A pattern forming method, characterized in that pattern etching is performed for each of regions having a similar pattern formation density among a plurality of divided regions. The pattern forming method according to claim 1,
A pattern forming method, wherein a pattern in an area to be subjected to pattern etching and a resist pattern covering another area are used as a mask at the time of each pattern etching. The pattern forming method according to claim 1,
A pattern forming method, wherein the substrate is a mask substrate used for pattern exposure.

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