JP2002050566A - Method for exposing honeycomb lattice pattern - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a new method, capable of easily forming a photoresist honeycomb lattice pattern having a lattice point size equivalent to or smaller than that attained in a conventional exposure method, even when an optical exposure system used for general purposes is adopted. SOLUTION: The method for exposing the honeycomb lattice pattern comprises the steps of multiple exposing a resist layer for forming L/S patterns 14, 15 and 16 existing bright lines and dark lines in parallel with each other, in the longitudinal direction of bright lines at 60 deg. with each other, and retaining a non-exposure part 17 surrounded by bright lines of three directions, formed at 60 deg. from each other in a longitudinal direction in a method for exposing the pattern, so that an exposure amount of the bright line is an exposure amount exceeding an exposure threshold of the resist layer.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for exposing a photoresist, and more particularly, to a method for exposing a photoresist for forming a honeycomb lattice pattern.

[0002]

2. Description of the Related Art In lithography used in the manufacture of semiconductor devices, an organic film called a photoresist is formed on a substrate, and light or X-rays are usually passed through an exposure mask formed with a light-shielding substance by an exposure device called a stepper.
This is a technique of irradiating a line and removing the organic film only with the irradiated portion or only the portion not irradiated with the developing solution, and forming the same pattern as the exposure mask or its reduced pattern on the substrate. In addition, there is a method of irradiating the organic film on the substrate with an electron beam in a one-stroke manner and then developing the pattern to form a pattern. Here, the term “exposure” includes both light and X-ray irradiation and electron beam irradiation.

[0003] Using such lithography technology,
In some cases, it is desired to form a grid pattern in which fine patterns such as circles and squares are regularly arranged in a grid pattern on a substrate. In particular, there is a two-dimensional periodic structure photonic crystal as an optical element requiring a fine lattice pattern, which is formed by forming a dielectric column such as a submicron circle or square or an air column in the dielectric into a square lattice (FIG. 2). 1) and a triangular lattice (2) as shown in FIG. 3,
Alternatively, it has a structure arranged in a honeycomb lattice (4) as shown in FIG. 4, and these lattice-like photoresist patterns are required for its production.

In such a method of exposing a fine grid pattern, it is an important element to form a photoresist pattern having a submicron structure with high dimensional accuracy.

As a method of forming a lattice pattern of a photoresist, an optical exposure apparatus using a g-line (wavelength: 486 nm) or an i-line (wavelength: 356 nm), which is most often used in the field of semiconductor device manufacturing (here, the term "stepper") )
Is used, an exposure mask having an enlarged pattern of a desired lattice pattern is used, and the mask pattern is reduced-projection-exposed on a photoresist on a wafer to form a pattern on the photoresist.

When these optical exposure apparatuses are used, the minimum value of the lattice constant of a photoresist lattice pattern that can be patterned is “extraction” (meaning that the photoresist is removed after development) or “remaining” (photoresist after development). (Meaning that the resist remains) is limited by the wavelength of light used. As the wavelength of the light used is shorter, a lattice pattern with a smaller lattice constant can be formed, and a lattice pattern with a smaller lattice constant can be formed by using the i-line than by the g-line. Further, if a KrF excimer laser stepper having a wavelength of 249 nm, an ArF excimer laser stepper having a wavelength of 193 nm, an X-ray exposure apparatus, or an electron beam lithography apparatus can be used, a lattice pattern having a smaller lattice constant can be patterned.

However, the KrF excimer laser stepper, the ArF excimer laser stepper, the X-ray exposure apparatus, and the electron beam lithography apparatus are all smaller than the g-line stepper and the i-line stepper which are currently frequently used in the semiconductor manufacturing process. It is expensive, and there is a problem that the production cost naturally increases when products are manufactured by using them.

[0008] Generally, to solve such problems,
In some cases, the resolution can be improved by using a super-resolution technique to improve the resolution of the pattern. For various methods of super-resolution technology, see, for example, Applied Physics Vol. 67, No. 5 (1998), p. P. 555-559, "Super-resolution technology in lithography". Among them, a method using a phase shift mask can improve the resolution only by changing the exposure mask. Other super-resolution techniques require modification of the stepper optics.

The phase shift mask is further classified into a spatial frequency modulation type (Levenson type) and an edge emphasis type, and the Levenson type phase shift mask provides the greatest improvement in resolution (up to twice). In other words, if a Levenson-type phase shift mask can be manufactured, a resolution twice as high as that obtained when a normal mask is used can be obtained, and the minimum lattice constant of a lattice pattern that can be resolved by the same stepper can be reduced to half.

For example, in the case of a two-dimensional photonic crystal,
The lattice constant (3) of the triangular lattice crystal of FIG. 3 used for near-infrared light having a wavelength of 1.55 μm is approximately 0.5 to 0.8 μm.
It is. The limit of the lattice constant that can be resolved by a normal exposure method without using the super-resolution technique is about twice the exposure wavelength, and about 0.8 μm for an i-line stepper. here,
If a Levenson-type phase shift mask can be manufactured, it is possible to cope with a lattice constant of about 0.4 μm, and the intended lattice constant of 0.5 to 0.8 μm can be sufficiently covered. In addition, the uniformity of the lattice pattern in the pattern plane or between the wafers is improved by the margin.

As described above, if the Levenson type phase shift mask can be manufactured, the problem of resolution and the problem of cost can be solved. However, unfortunately, this Levenson type phase shift mask has a line and space pattern (L / S).
Although the pattern is easy to fabricate, it cannot be fabricated with a two-dimensional lattice pattern useful as a lattice pattern for photonic crystals. As a method of solving this problem,
000-150340 (Japanese Patent Application No. 10-317698) discloses a method for exposing a lattice pattern.

A procedure for patterning a triangular lattice pattern (expressed as “hexagonal lattice” in the above-mentioned patent publication but having the same meaning) using this method will be described with reference to FIG. FIG. 5 is a diagram for explaining an example in which a triangular lattice pattern is transferred by triple exposure of an L / S pattern.

Three L / S patterns (7, 8, 9) having directions different from each other by 60 ° are subjected to triple exposure so that lines (L portions) for three patterns pass at all intersections. At this time, the exposure amount of each exposure is adjusted so that the exposure threshold value of the photoresist is exceeded only at the triple intersection (10) of the bright line portion (L portion) where the sum of the exposure amounts of the three times is maximum. I do. Upon exposure in this manner, after development of the photoresist, a triangular lattice pattern is obtained as an array of intersections of bright line portions. In this method, since the mask pattern becomes L / S, it can be manufactured as a Levenson-type phase shift mask, and as a result, the resolution can be doubled.

The honeycomb lattice pattern (4) of FIG. 4 is also a useful lattice pattern as a two-dimensional photonic crystal pattern, like the triangular lattice pattern (2) of FIG. In the case where the honeycomb lattice pattern (4) is applied to manufacture a photonic crystal using a 1.55 μm wavelength, the lattice constant (5) in FIG. At first glance, it seems that the exposure of the honeycomb lattice pattern is easier.
However, in practice, the closest lattice point interval (6) in the honeycomb lattice pattern of FIG. 4 is substantially the same as that of the triangular lattice pattern, that is, 0.5 to 0.8 μm. Therefore, even when the honeycomb lattice pattern is formed by lithography. The same resolution as that for forming a triangular lattice pattern is required.

The above-mentioned Japanese Patent Application Laid-Open No. 2000-150340 discloses a method of exposing a lattice pattern by extending the method of forming a triangular lattice pattern using an L / S pattern. Is disclosed. FIG. 6 is for explaining the method. L / S pattern (11, 12) divided into broken lines
Exposure is performed by using the method, and the lattice points of the honeycomb lattice (13)
To form According to this method, even in the case of a honeycomb lattice pattern, a Levenson-type phase shift mask can be used, and resolution can be achieved with the same margin as in the case of forming a triangular lattice pattern.

[0016]

However, if a honeycomb lattice pattern is to be formed by the method disclosed in the above-mentioned Japanese Patent Laid-Open Publication No. 2000-150340, entitled "Exposure Method for Lattice Pattern," FIG. , L /
It is necessary to make the S pattern a broken line, and there is a drawback that it is difficult to design a mask pattern in practical use.

It is a primary object of the present invention to provide a method which overcomes these disadvantages of the prior art. In particular, a new method that can easily form a photoresist honeycomb lattice pattern having a lattice point size equal to or smaller than a dimension that cannot be achieved by a conventional exposure method, even when a general-purpose optical exposure apparatus is used. Is to provide.

[0018]

According to a first aspect of the present invention, a method for exposing a honeycomb lattice pattern according to the present invention comprises the steps of: exposing an exposure pattern having bright lines and dark lines in parallel so that the longitudinal directions of the bright lines are different; A pattern exposure method for performing multiple exposure on a layer and leaving a non-exposed portion surrounded by bright lines in three directions having different longitudinal directions, wherein the exposure amount of the bright line is set to an exposure threshold of the resist layer. It is characterized in that the exposure amount exceeds. In a second aspect, the method for exposing a honeycomb lattice pattern according to the present invention includes the steps of: exposing an exposure pattern in which a bright line and a dark line exist in parallel to a resist layer so that the bright line has a different longitudinal direction; Is a pattern exposure method for generating multiple exposure portions that are at least triple multiple exposure with bright lines in three different directions, wherein only the exposure amount of the multiple exposure portion exceeds the exposure threshold value of the resist layer. And performing multiple exposure so that the shape of the multiple exposure unit is a shape having three vertices.

In a third aspect, in the method for exposing a honeycomb lattice pattern according to the present invention, an exposure pattern in which bright lines and dark lines are present in parallel is subjected to multiple exposure on a resist layer such that the longitudinal directions of the bright lines are different. A pattern exposure method for generating a multiple exposure portion at least triple-exposed with bright lines in three directions having different longitudinal directions, wherein only the exposure amount of the multiple exposure portion exceeds an exposure threshold of the resist layer. The multiple exposure is performed so that the exposure amount is set, and the line connecting the centers of the three multiple exposure portions generated adjacently within one bright line region of the exposure pattern generates a triangle. Features. In a fourth aspect, a method for manufacturing a semiconductor device according to the present invention includes an exposure step of performing pattern exposure by the method for exposing a honeycomb lattice pattern according to the present invention.

[0020]

DESCRIPTION OF THE PREFERRED EMBODIMENTS As an exposure pattern used in the present invention, there is a pattern in which a plurality of bright lines and dark lines are present in parallel in the width direction thereof.
There is a line-and-space pattern (L / S pattern) as described in Japanese Patent Application Laid-Open Publication No. HEI 9-86, 1988. The bright and dark lines are
Each can be straight, but can be curved if desired. The width of each of the bright line and the dark line can be constant.

In the method of exposing the honeycomb lattice pattern from the first viewpoint, the shape of the non-exposed portion left on the surface of the resist layer is a three-line bright line having a different longitudinal direction, for example, three bright lines having different longitudinal directions. The vertices surrounded by can be formed into three shapes, for example, a triangle or a substantially triangle.
In the exposure method of the honeycomb lattice pattern from the first viewpoint, if necessary, at least one of the three bright lines having different longitudinal directions, for example, three bright lines having different longitudinal directions. At least one of the bright lines may be exposed in multiples of two or more.

[0022] In the method of exposing a honeycomb lattice pattern according to a second aspect, the shape of the multiple exposure portion is set to three vertices.
, Such as a triangle or a substantially triangle. In the exposure method of the honeycomb lattice pattern from the second and third viewpoints, if necessary, at least one of the three bright lines having different longitudinal directions, for example, three bright lines having different longitudinal directions. At least one of the bright lines may be exposed in multiples of two or more.

In the exposure method of the present invention, the same exposure pattern can be subjected to multiple exposure while changing its direction. Further, at least one of the multiple exposure patterns is different from other exposure patterns (for example, exposure patterns having different shapes, dimensions, etc.) according to the remaining pattern of the resist layer to be left after development. Pattern).

As the resist of the resist layer, a resist in which a portion other than the exposed portion exposing the exposure amount exceeding the exposure threshold value is removed by a developing solution, or an exposed portion exposing the exposure amount exceeding the exposure threshold value is used. A resist that is removed with a developer can be used.

Referring to FIG. 1, an embodiment of the present invention will be described. The method of exposing a honeycomb lattice pattern according to the present invention is different from the method of exposing a lattice pattern using an optical exposure apparatus, in that L is not a broken line but a straight line. / S pattern (1
4, 15 and 16) are performed, and the individual exposure amount is set to be equal to or larger than the exposure threshold value of the photoresist each time to obtain a honeycomb lattice pattern as a pattern of the non-exposed portion (17). .

Alternatively, in the above method, the light and dark portions of the L / S are interchanged, and the exposure amount for each exposure can be selected so that only the portions irradiated three times with the exposure light exceed the exposure threshold value of the photoresist. For example, a honeycomb lattice pattern can be obtained as a pattern of the triple light irradiation part.

Further, according to the present invention, a fine pattern resolution characteristic exceeding the resolution limit of the ordinary optical exposure method can be obtained at the same time as the high speed of the optical exposure method characterized by the high-speed exposure as compared with the electron beam exposure method. Can be

As described above, in the method of exposing a honeycomb lattice pattern according to the present invention, a set of fine lattice points of the honeycomb lattice is defined as a triple intersection of a dark portion or a bright portion of three L / S patterns. When the lattice points are defined by L / S patterns, the period of each L / S pattern is the same as the lattice constant, that is, 0.8 to 1.4 μm. If an i-line stepper is used, an L / S pattern with a period of 0.7 μm or more can be resolved, so an L / S pattern with a period of 0.8 to 1.4 μm, and consequently a lattice constant of 0.8 to 1.4 μm Can be resolved with a margin without using a Levenson-type phase shift mask.

[0029]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In order to explain the present invention in more detail, embodiments of the present invention will be described below with reference to the drawings.

[First Embodiment] A first embodiment of the present invention will be described. The honeycomb lattice pattern exposure method of the present invention is basically the same as the exposure method of a triangular lattice pattern (instead of a honeycomb lattice pattern) disclosed in JP-A-2000-150340, entitled "Exposure method of lattice pattern". Step on. The point that the present invention differs from the prior art is the exposure amount.

The procedure of the embodiment of the honeycomb lattice pattern exposure method of the present invention will be described below with reference to the drawings. Prepare a wafer coated with photoresist, and as shown in FIG.
Three L / S patterns (14,
15 and 16) are subjected to triple exposure so that the lines (L portions) of the bright portions of the three patterns pass at all the intersections. At this time, adjustment is made so that the exposure amount in the exposure of each L / S pattern exceeds the exposure threshold value of the photoresist.

With such exposure, after developing the photoresist, a honeycomb lattice pattern can be obtained as an array of dark portions (17) to which no light has been irradiated, ie, triple intersections of the dark portions. If the photoresist is of a positive type, a honeycomb lattice pattern of the remaining pattern (a pattern in which the photoresist remains at lattice points) is obtained. In addition, if the photoresist is a negative type, a honeycomb lattice pattern (a pattern in which holes are opened at lattice points) of a punched pattern can be obtained.

When confirmed again, Japanese Patent Application Laid-Open No. 2000-150
In the method of exposing a triangular lattice pattern (not the honeycomb lattice pattern) disclosed in Japanese Patent Publication No. 340, “Lattice pattern exposure method”, as shown in FIG. 7, 8, 9) are subjected to triple exposure so that lines (L portions) for three patterns pass at all intersections. At this time, the exposure amount of each exposure is adjusted so that the exposure threshold value of the photoresist is exceeded only at the triple intersection (10) of the bright line portion (L portion) where the sum of the exposure amounts of the three exposures is maximum. I do. In this way, a triangular lattice pattern is obtained.

On the other hand, in the exposure method of the present invention, the difference is that the exposure amount is selected so as to exceed the exposure threshold value of the photoresist not only at the triple intersection but also at all bright portions. By selecting the amount of exposure in this manner, a honeycomb lattice pattern more complicated than a triangular lattice pattern can be formed in substantially the same procedure. Moreover, the closest lattice point interval (6) of the honeycomb lattice of 0.5 to 0.8 μm is set to a period of 0.8 to 0.8 μm.
The resolution can be achieved by using the 1.4 μm L / S pattern, so that a resolution with a margin can be achieved without using the Levenson type phase shift mask.

It is to be noted that the resolution is best performed after the multiple exposure in the developing process, but a developing process or a baking process may be inserted between the multiple exposures. Next, a second embodiment of the present invention will be described.

[Second Embodiment] In the first embodiment of the present invention, a method in which the light portion and the dark portion of the L / S pattern are exchanged is also possible. That is, a wafer coated with a photoresist is prepared, and three L's having directions different from each other by 60 ° in FIG. 1 are prepared.
/ S pattern (14, 15, 16) at all intersections
Triple exposure is performed so that the dark portion line (S portion) of the pattern passes. At that time, the exposure amount for each exposure is adjusted so that only the exposure amount in the triple-irradiated portion exceeds the exposure threshold value of the photoresist.

With such exposure, after developing the photoresist, a honeycomb lattice pattern can be obtained as an array of lighted portions (17) irradiated with light three times. If the photoresist is a positive type, a honeycomb lattice pattern (a pattern having holes at lattice points) of a punched pattern can be obtained.
If the photoresist is a negative type, a honeycomb lattice pattern of the remaining pattern (a pattern in which the photoresist remains at the lattice points) is obtained. It is apparent that the present invention can be appropriately modified within the scope of the technical idea of the present invention.

[Effects of Embodiment] In the present lattice pattern exposure method, a set of fine lattice points of a honeycomb lattice is defined as a triple intersection of a dark part or a light part of three L / S patterns.
When this lattice point is defined by the L / S pattern, each L
The period of the / S pattern is the same as the lattice constant, that is, 0.8 to
It is 1.4 μm. If an i-line stepper is used, an L / S pattern with a period of 0.7 μm or more can be resolved, so an L / S pattern with a period of 0.8 to 1.4 μm, and consequently a lattice constant of 0.8 to 1.4 μm Can be resolved with a margin without using a Levenson-type phase shift mask.

Further, according to the present invention, based on the basic structure of performing the multiple exposure of the L / S pattern three times, the honeycomb lattice having both the high speed of the optical exposure method and the fine pattern drawing characteristics of the electron beam exposure method. A method of exposing a pattern is provided.

[0040]

The first effect of the method of exposing a honeycomb lattice pattern according to the first to third aspects of the present invention is that a honeycomb lattice-like exposure pattern having an extremely small lattice point interval is simply exposed to the surface of a resist layer. That you can do it. The first reason is that the exposure method of the honeycomb lattice pattern according to the first aspect of the present invention is such that an exposure pattern in which bright lines and dark lines exist in parallel is multiplexed on a resist layer so that the longitudinal direction of the bright lines is different. A pattern exposure method comprising: exposing a non-exposed portion surrounded by bright lines in three directions having different longitudinal directions, wherein the exposure amount of the bright line exceeds an exposure threshold value of the resist layer. Because it is.

The second reason is that the method of exposing a honeycomb lattice pattern according to the second aspect of the present invention employs a method of exposing an exposure pattern in which a bright line and a dark line exist in parallel so that the longitudinal direction of the bright line is different. A pattern exposure method for performing multiple exposure on a layer to generate a multiple exposure portion that is at least triple multiple exposure with bright lines in three directions having different longitudinal directions, wherein only the exposure amount of the multiple exposure portion is different from that of the resist layer. This is because multiple exposure is performed so that the exposure amount exceeds the exposure threshold value and the shape of the multiple exposure unit is a shape having three vertices. The third reason is the third reason of the present invention.
In the method of exposing a honeycomb lattice pattern from the viewpoint of the above, the exposure pattern in which the bright line and the dark line exist in parallel is subjected to multiple exposure on the resist layer so that the longitudinal direction of the bright line is different, and the light is exposed in three directions having different longitudinal directions. A pattern exposure method for generating a multiple exposure portion that is at least triple multiple exposure with a line,
Three multiple exposure portions generated so that only the exposure amount of the multiple exposure portion exceeds the exposure threshold value of the resist layer, and adjacently within one bright line region of the exposure pattern This is because multiple exposure is performed such that a line segment connecting the centers of the triangles forms a triangle.

The second effect of the honeycomb lattice pattern exposure method according to the first to third aspects of the present invention is that a honeycomb lattice exposure pattern is formed on the surface of the resist layer by using an easily designed exposure mask pattern. This means that exposure can be easily performed. The reason is the same as the first to third reasons.

[Brief description of the drawings]

FIG. 1 is a schematic diagram illustrating an exposure method of the present invention.

FIG. 2 is a schematic diagram illustrating a square lattice.

FIG. 3 is a schematic diagram showing a triangular lattice.

FIG. 4 is a schematic view showing a honeycomb lattice.

FIG. 5 is a schematic diagram illustrating a conventional multiple exposure method using a triangular lattice.

FIG. 6 is a schematic diagram illustrating a conventional exposure method of a honeycomb lattice.

[Explanation of symbols]

Reference Signs List 1 square lattice 2 triangular lattice 3 lattice constant of triangular lattice 4 honeycomb lattice 5 lattice constant of honeycomb lattice 6 nearest lattice point interval of honeycomb lattice 7, 8, 9, 11, 12, 13 L / S pattern 10 L / S pattern Triple intersection of bright part 17 Triple intersection of L / S pattern dark part in the first embodiment or triple intersection of bright part in the second embodiment

Claims (4)

[Claims] An exposure pattern in which a bright line and a dark line exist in parallel is subjected to multiple exposure on a resist layer so that the longitudinal direction of the bright line is different, and a non-enclosed pattern surrounded by bright lines in three directions having different longitudinal directions. A pattern exposure method for leaving exposed portions, wherein the exposure amount of the bright line is an exposure amount exceeding an exposure threshold value of the resist layer. 2. An exposure pattern in which a bright line and a dark line are present in parallel is subjected to multiple exposure on a resist layer so that the longitudinal direction of the bright line is different, and the resist pattern is at least tripled with bright lines in three different longitudinal directions. A pattern exposure method for generating a multiple exposure portion subjected to multiple exposure, such that only the exposure amount of the multiple exposure portion exceeds an exposure threshold value of the resist layer, and the shape of the multiple exposure portion Exposure method for a honeycomb lattice pattern, wherein multiple exposure is performed so that the number of vertices is three. 3. A resist pattern in which a bright line and a dark line are present in parallel is subjected to multiple exposure on a resist layer so that the longitudinal directions of the bright lines are different from each other, and the resist pattern is at least tripled with bright lines in three different longitudinal directions. A pattern exposure method for generating a multiple exposure portion subjected to multiple exposure, such that only the exposure amount of the multiple exposure portion exceeds an exposure threshold value of the resist layer, and one of the exposure patterns A plurality of exposures, wherein a line segment connecting the centers of three multiple exposure portions generated adjacent to each other in a bright line region forms a triangle. 4. A method of manufacturing a semiconductor device, comprising an exposure step of performing pattern exposure by the method of exposing a honeycomb lattice pattern according to claim 1.