JP3516667B2 - Mask, method of manufacturing semiconductor device, and exposure apparatus - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pattern transfer mask used in a manufacturing process of a semiconductor device or a liquid crystal device, a semiconductor device manufactured using the mask, and an alignment mechanism for the mask. The present invention relates to a provided exposure apparatus.

[0002]

2. Description of the Related Art An electron beam (EB) exposure technique is a technique which has recently been attracting attention as one of semiconductor device manufacturing techniques. It is expected as a technique suitable for forming an ultrafine pattern because it is superior in resolution and depth of focus to the conventional light exposure. However, a so-called direct writing method of writing a pattern on a wafer with an electron beam has a low throughput and is not suitable for a mass production process in which productivity is important. Therefore, as in the case of light exposure, a method has been proposed in which an electron beam is selectively transmitted using a mask to transfer the mask pattern onto the wafer.

FIG. 4 is a diagram showing an outline of the partial batch method in electron beam exposure. As shown in the figure, an electron beam 7 emitted from an electron gun (not shown) is shaped into a rectangular beam by a shaping aperture 1 which is a first mask, and then a second beam is formed.
The stencil mask 2 which is the mask of No. 2 is irradiated, the wafer 3 is exposed by the electron beam 7 that has passed through the stencil mask 2, and the pattern 4 is transferred onto the wafer 3. The stencil mask 2 has a partial batch opening 5 and a variable shaping opening 6.
Are formed. The partial collective opening 5 is a hole having a shape of a pattern repeatedly appearing on the wafer, and the variable shaping opening 6 is an opening for directly drawing a pattern having a low appearance frequency. This method is intended to improve the throughput by transferring a part of the repetitive patterns at once.

A method that takes this idea one step further is an electron beam projection exposure (EPL).
hography) method. EPL is a method in which direct writing is not performed and all are transferred using a mask. In Figure 5, EP
3 shows a standard stencil mask for L. FIG. 5A is a plan view of the stencil mask 8 for EPL, and this mask is provided with two rectangular beam structure regions 9. FIG. 5B is an enlarged view of a part of the beam structure region 9. As shown in this figure, the beam structure region 9 is a region in which a plurality of exposure unit regions 10 are arranged in a grid pattern. The exposure unit area 10 is an area corresponding to one shot when the electron beam is irradiated. The range of exposure with one shot of the electron beam is usually a part of the inside of the exposure unit region 10 to prevent the influence of electron scattering around the beam. Exposure unit area 1
At 0, transmission regions 11 having various shapes corresponding to the pattern shape are formed as through holes. Also, FIG.
5C shows one exposure unit area 1 shown in FIG.
It is a figure of the cross section X of 0. As shown in the figure, when the stencil mask 8 is manufactured, it is preferable that the transmissive region 11 is formed after the region to be the exposure unit region 10 is previously etched to form a thin film. This is because when the film thickness of the exposure unit region is large, the dimensional accuracy of the pattern may be impaired due to the microloading effect in the dry etching process for forming the through hole (transmission region 11). In the stencil mask manufactured in this way, as shown in FIG. 5C, the exposure unit region 10 has a structure in which the periphery is supported by the beam 12 having a thickness corresponding to the film thickness of the mask.

As a mask used for electron beam exposure, in addition to the above-mentioned stencil mask in which a through hole is formed in a silicon wafer, a heavy metal material that scatters or absorbs an electron beam in a portion other than the transmission region on the thin film is used. There is also proposed a scalpel-type mask in which an electron beam is allowed to pass only through a transmission region by forming a film.

[0006]

However, the structure of the stencil mask as described above has a problem that stress is concentrated on a part of the mask when a force is applied from the outside of the mask. For example, in the arrangement shown in FIG. 5A, since the beam structure region 9 has a shape having a right angle, stress is likely to concentrate on the four corners 13. As a result, the four corners 13 of the beam structure region 9 are
Therefore, there is a problem that the mask starts to deteriorate and cracks are easily generated in the mask. Furthermore, since the exposure unit regions 10 are arranged in a grid, there is a high possibility that the beam 12 supporting each exposure unit region will be distorted by external stress. That is, the exposure unit area and thus the transmission area may be deformed. Deformation of the mask not only shortens the mask life, but also reduces the yield if a semiconductor device is manufactured using the deformed mask. In particular,
In the EPL, the reduction rate at the time of transfer projection is set to 1/4 in order to include all patterns in one mask (two masks when a complementary mask is required). Therefore, the problem is more serious than in the case of the EB direct writing partial batch exposure in which the reduction ratio is about several tenths, and the deformation of the transmissive region causes the distortion of the pattern immediately transferred or the connection between the patterns. It appears as a gap.

Since the electron beam exposure apparatus normally repeats high speed movement and stopping of the mask, the acceleration of the mask reaches 5 g (g is gravitational acceleration). Stress corresponding to the acceleration is applied to the mask from the mask mounting portion of the exposure apparatus. It is expected that the stress applied to the mask will be further increased by increasing the acceleration in order to improve the throughput. This problem is not limited to a stencil mask having a through hole, and a scalpel-type mask having no hole may have a similar problem because only the exposure unit region has a thin film shape. Therefore, an urgent solution to the above problems is desired.

A first object of the present invention is to provide a new mask that solves the above problems. A second object is to provide a highly accurate semiconductor device by using this new mask. Furthermore, in order to use this new mask, an exposure apparatus corresponding to this mask is required, and therefore it is a third object to provide this exposure apparatus.

However, although the present invention has been made to solve the above three problems, it has been confirmed that various effects other than the achievement of these objects are obtained. That is, the technical scope of the present invention should not be limitedly interpreted by the above problem to be solved. Note that these effects will be described later together with the embodiments of the present invention.

[0010]

A mask of the present invention is a mask for pattern transfer, comprising a plurality of exposure unit regions and a beam formed at a boundary portion between exposure unit regions adjacent to each other. the shape of the exposure unit regions Ri hexagonal der, adjacent
A group of exposure unit areas arranged in a circle on the mask.
It is characterized in that it is arranged so as to form a beam-shaped structure region .

The "exposure unit area" is an area corresponding to one electron beam shot. However, the exposure range may be a partial range inside the exposure unit area in order to prevent electron scattering at the boundary. The "beam formed at the boundary portion" means that the region is divided into a plurality of exposure unit regions by a plurality of beams formed in a predetermined region of the mask. In other words, the boundary between the exposure unit regions is formed by the beam.

The "hexagon" is preferably a symmetrical hexagon having only obtuse angles, and a regular hexagon is most preferable. That is, it is preferable to select a hexagonal shape which is less likely to have stress concentrated on the corners, can be arranged side by side without a gap, and when so arranged, forms a so-called honeycomb structure.

It is preferable that the exposure unit area has a thin film structure. In other words, it is preferable to perform the etching process in advance so that the portion to be the exposure unit area has an appropriate film thickness. After that, each mask is completed by providing a transmission region having a predetermined shape for transmitting energy rays, that is, the same shape as the pattern to be transferred, in the exposure unit region. If the exposure unit region is etched in advance so as to have a thin film structure, it is possible to perform highly accurate processing when forming the transmission region. However, the "transmissive region" means a region provided on the mask and capable of selectively transmitting energy rays, and does not necessarily have to be a through hole.

Here, the "energy beam" means an electron beam,
It includes all irradiation rays used in exposure technology such as ion beams, X-rays, and ultraviolet rays. The “energy-sensitive substrate” allows a predetermined reaction to occur when an energy ray used as an irradiation ray is applied to distinguish the area where a pattern is to be formed from other areas (that is, the pattern). Is a substrate of a material that can transfer
The case where a layer of such a material is provided on the wafer is also included.

Next, a method of manufacturing a semiconductor device according to the present invention will be described.
A circle or ellipse for each exposure unit area on such a mask
Irradiated without forming the shape of the energy beam, by applying an energy beam passing through the transmissive region to a predetermined energy sensitive substrate, further comprising the step of transferring a pattern of the predetermined shape in the energy sensitive substrate In a characteristic way
It

In the exposure apparatus of the present invention, such a mask is irradiated with energy rays for each exposure unit area, and the energy rays passing through the transmission area are applied to a predetermined energy sensitive substrate to form a pattern of a predetermined shape. Is an exposure apparatus that transfers the laser beam onto the energy-sensitive substrate, and is an exposure apparatus that includes a positioning unit for aligning the position of the mask with respect to the energy-sensitive substrate to a desired position. Since the mask of the present invention is different from the conventional mask in the arrangement or shape of the exposure unit areas, the exposure apparatus is provided with a corresponding alignment mechanism.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below with reference to the drawings.

First, an embodiment of the mask of the present invention will be shown. FIG. 1 is a diagram showing a stencil mask 14 in the present embodiment. FIG. 1A is a plan view of the stencil mask 14, in which a circular beam structure region 15 is provided on the 8-inch mask. Here, the beam structure region 15 is a region in which a group of exposure unit regions 16 are arranged adjacent to each other. The exposure unit area 16 is an area that serves as a unit when the electron beam is irradiated, that is, an area corresponding to one shot of the electron beam. In the present embodiment, the beam structure region 15 is a circular region because sufficient strength can be obtained without any particular reinforcement, but the shape may be a polygon (for example, a hexagon), There is no particular limitation. Further, the exposure unit area 16 may be arranged in one beam structure area 15 as in the present embodiment, or 2
There may be the above beam structure region 15. For example, a plurality of circular beam structure regions may be arranged on the stencil mask 14. FIG. 1B is an enlarged view of a part of the beam structure region 15. As shown in this figure, the beam structure region 15
A plurality of hexagonal exposure unit regions 16 are arranged therein so as to have a honeycomb structure.

In the present embodiment, each exposure unit area 16 is a regular hexagon having a size that can fit within a circle having a diameter of 1 mm. Beams 18 are formed at boundaries between adjacent exposure unit regions, and each exposure unit region 16 has a structure surrounded by six beams 18. When the electron beam is irradiated, in order to prevent the influence of electron scattering around the beam 18, the electron beam is irradiated to a part of the exposure area 23 inside the exposure unit region 16. In the exposure area 23, transmission regions 17 of various shapes corresponding to the pattern shape are formed as through holes.
Further, FIG. 1C is a diagram of a cross section Y of one exposure unit area 16 shown in FIG. As shown in FIG. 1C, the stencil mask 14 has a structure in which an exposure unit region 16 of a thin film structure is supported by a beam 18 on the periphery. In the present embodiment, the mask having such a structure is
It is manufactured as follows. First, the silicon substrate 20
A SiO ₂ oxide film 21 and a silicon layer 22 are formed thereon. The silicon substrate having such a structure can be easily formed by using a technique such as wafer bonding. Next, Si
The silicon substrate 20 is etched by using the O ₂ oxide film 21 as a stopper to thin the portion to be the exposure unit region 16. Further, the silicon layer 22 is dry-etched from the opposite direction to form the transmissive region 17.

FIG. 2 is a diagram showing an outline of EPL using the mask of FIG. The electron beam 7 emitted from the electron gun is sequentially irradiated to each exposure area 23 of each exposure unit area 16 of the stencil mask 14. Further, the wafer 3 is exposed by the electron beam 7 that has passed through the transmission region 17 formed in the exposure area 23, and the pattern 4 is transferred onto the wafer 3 at a reduction rate of 1/4. That is, a hexagonal exposure unit area that fits within a circle with a diameter of 1 mm has a diameter of 250 mm on the wafer 3.
It corresponds to a hexagonal area that fits within a circle of μm.

The effects obtained by making the exposure unit area 16 hexagonal will be described below.

First, in the case of a hexagon formed by only obtuse angles such as a regular hexagon, there is no problem that stress is extremely concentrated at the corners like a quadrangle. Therefore, even if the masks are arranged in two rectangular regions as in FIG. 5, the problem of mask cracking is unlikely to occur.

Secondly, when the hexagonal exposure unit regions are arranged side by side without any gap so that each side is adjacent to each side of another exposure unit region, the structure becomes a honeycomb structure. In this structure, unlike the structure shown in FIG. 5, the beams of the adjacent exposure unit regions do not line up in the same direction on a straight line, so that the stress is dispersed even if an external force is applied to the mask. Therefore, the problem that the beam is easily distorted does not occur. Further, since this structure is symmetrical in three directions, it can be said that the structure is relatively strong against external force from any direction. Therefore, the degree of influence of the external force does not change depending on the orientation when the mask is installed, and the degree of freedom in the mask installation direction and the fixed position is high.

As described above, by making the exposure unit area hexagonal, it is possible to prevent the mask from being deteriorated or deformed by stress. Further, making the exposure unit area hexagonal has the following advantages.

One is that they can be efficiently arranged without creating an empty area, that is, they can be spread over a plane. For example, when the shape of the exposure unit area is an octagon, the problem of stress can be solved, but the exposure unit areas cannot be arranged without a gap.
Further, since the stress is less likely to be generated in the corner portion as compared with the quadrangle, the exposure unit region can be arranged near the end portion of the mask as shown in FIG. Further, since it is structurally strong, the beam can be made thin so that the exposure unit regions can be closer to each other. That is, more exposure unit regions can be arranged on one mask, and the mask can be effectively used.

When the exposure unit area has a hexagonal shape, the beam shaping by the shaping aperture 1 shown in FIG. 4 can be omitted. Conventionally, since the shape of the chip to be manufactured is rectangular, it has been common knowledge that the shape of the exposure unit area is also the same and the electron beam is shaped into a rectangular shape. If an electron beam with a circular or elliptical cross section is used to irradiate a rectangular exposure unit area, it may irradiate a part of the adjacent exposure unit area together. (Area) must be thick. On the other hand, if the radius of the circular or elliptical electron beam is reduced so that the electron beam is not irradiated to the outside of the rectangular exposure unit region, the four corners of the rectangular exposure unit region are not irradiated with the electron beam at all. In this case, the range in which the transmissive region can be formed is limited, and the exposure unit region cannot be effectively utilized. That is,
Conventionally, the electron beam had to be shaped into a rectangle.
However, if the exposure unit area is hexagonal, even if the entire exposure unit area is irradiated with a circular or elliptical electron beam, it is possible that a part of the adjacent exposure unit area is irradiated. It is obviously lower than when the area is rectangular. Even if the radius of the circular or elliptical electron beam is reduced, the electron beam is irradiated to most of the hexagonal exposure unit area as shown in FIG. 2, so the hexagonal area is effective. Can be utilized to form a transparent region. Therefore, it is not necessary to shape the cross section of the electron beam into a hexagon, and it is possible to directly irradiate the electron beam with a circular or elliptical shape. As a result, the structure of the exposure apparatus can be simplified. However,
Needless to say, the electron beam may be shaped into a hexagon according to the shape of the exposure unit area, as in the conventional case.

Although the mask described in the above embodiment is a stencil mask manufactured by using a silicon wafer, the mask of the present invention is not limited to the stencil mask and can be applied to a scalpel type mask. . Further, the case where the structure of the exposure unit region is a thin film structure supported by a beam has been described as an example, but as described above, the present invention not only solves the problem of mask deformation due to stress but also exhibits other various effects. Therefore, it is applicable to a mask having a thicker film thickness.

[0028] Using the mask of the present invention when performing pattern transfer in the manufacturing process of semiconductor devices, good accuracy of pattern processing, it is possible to ensure a high quality in comparison with the conventional semiconductor device. Moreover, since the problem of mask deformation is unlikely to occur, the yield of the manufacturing process can be improved.

Next, the exposure apparatus of the present invention will be described. The exposure apparatus is not limited to the exposure apparatus of the present invention, and the exposure apparatus is provided with a mechanism for accurately adjusting the position where the pattern is transferred. As described above, the electron beam exposure transfers the entire pattern by sequentially transferring and connecting partial patterns, so that the mask position shift appears as a shift of the pattern bonding portion, This is because the yield will be reduced.

In this embodiment, a mark (alignment mark) for alignment which is formed on the mask.
Are formed at three points of a hexagon as shown in FIG. However,
It goes without saying that other alignment marks may be arranged.

The position measurement by the alignment mark detection is performed, for example, by irradiating the mask with a laser beam and detecting the light diffracted / scattered by the alignment mark with a sensor to measure the LSA (Laser Step Alignment). This is performed by a known method such as FIA (Field Image Alignment) for detecting the position of the upper alignment mark. On the other hand, for the alignment based on the measurement result, a control program that assumes that the exposure unit area has a hexagonal shape and has a honeycomb structure must be incorporated in the exposure apparatus. The moving direction of the mask at the time of alignment also depends on the order in which the patterns are transferred. In the conventional arrangement of the exposure unit areas, it is general to move the mask in the X direction or the Y direction for alignment, but in the case of a hexagon, the adjacent exposure unit areas are in six directions. Various movement methods are possible. That is, since the degree of freedom in moving the mask is high, there is room for various measures to improve throughput.

[0032]

As described above, in the mask of the present invention, by making the exposure unit area a hexagon, deterioration and deformation of the mask due to external stress can be prevented, and as a result, a precise Pattern transfer is realized to improve the yield of the manufacturing process. Furthermore, because of its structure, more exposure unit areas can be arranged on the mask.
It is possible to effectively utilize one mask.

If the exposure unit area has a thin film structure supported by beams, a highly accurate mask can be realized. Further, since the thin film structure is easily affected by external stress, the effect of the present invention is particularly great.

Further, the semiconductor device manufactured through the exposure process using the mask of the present invention has a good yield because the pattern accuracy does not decrease due to the mask deformation.
High quality can be provided.

Further, when the mask of the present invention is used for exposure, if the mask aligning mechanism dedicated to the mask is provided in the exposure apparatus, accurate alignment can be realized, and the displacement of the joint between the partial patterns can be realized. It is possible to carry out a highly accurate pattern transfer without any error.

[Brief description of drawings]

FIG. 1 is a diagram showing a mask according to an embodiment of the present invention.

2 is a diagram showing an outline of an EPL using the mask of FIG.

FIG. 3 is a diagram showing an example of mark positions for alignment.

FIG. 4 is a diagram showing an outline of electron beam exposure.

FIG. 5 is a view showing a conventional EPL stencil mask.

[Explanation of symbols]

1 shaping aperture, 2 stencil mask, 3
Wafer, 4 patterns, 5 partial batch openings, 6
Variable shaping opening, 7 electron beam, 8 stencil mask, 9 beam structure area, 10 exposure unit area, 1
1 transmissive area, 12 beams, 13 four corners, 14 stencil mask, 15 beam structure area, 16 exposure unit area, 17 transmissive area, 18 beam, 19 mark,
20, 22 Silicon, 21 Oxide film, 23 Exposure range

Claims (5)

(57) [Claims] 1. A mask for pattern transfer, comprising a plurality of exposure unit regions and a beam formed at a boundary between adjacent exposure unit regions, wherein the exposure unit regions have a hexagonal shape. , A group of exposure unit areas arranged adjacent to each other
Are arranged so as to form a circular beam structure region on the mask.
A mask characterized by being placed . 2. The mask according to claim 1, wherein the exposure unit region has a thin film structure. 3. The mask according to claim 1, wherein the exposure unit area has a transmission area having a predetermined shape for transmitting energy rays. 4. The mask according to claim 3 is irradiated with a circular or elliptical energy beam without being shaped for each exposure unit region, and the energy beam passing through the transmission region is subjected to a predetermined energy response. A method for manufacturing a semiconductor device , comprising the step of applying the pattern having the predetermined shape onto a substrate and then transferring the pattern onto the energy sensitive substrate. 5. The mask according to claim 3 is irradiated with energy rays in each of the exposure unit areas, and the energy rays passing through the transmission areas are applied to a predetermined energy sensitive substrate,
An exposure apparatus for transferring a pattern of the predetermined shape onto the energy-sensitive substrate, the exposure apparatus comprising alignment means for aligning the position of the mask with respect to the energy-sensitive substrate to a desired position. apparatus.