JP2006023681A - Mask for charged particle ray exposure - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a mask form which can suppress the total mass of the mask and increase rigidity of the mask at a time in a mask to be used for projection electron beam lithography. <P>SOLUTION: A substrate is further bonded to a mask substrate for reinforcement, wherein the mask used has a beam structure so as to keep the required strength and rigidity as well as to suppress the mass of the mask. The strength of the mask per mass can be increased by constituting a honeycomb structure or a grid structure considering the loading direction for the beam structure of the substrate for reinforcement. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a charged particle beam exposure mask mask for pattern transfer used in charged particle beam lithography using a charged particle beam such as an electron beam.

  In pattern projection type electron beam lithography in which a charged particle beam source such as an electron beam is used as a light source and a transmitted beam image is projected onto a sample substrate using a mask, generally a thin film of several μm or less such as silicon or diamond Is used as a mask. For example, in the case of a mask using a silicon thin film, an SOI (Silicon On Insulator) substrate is used, and the silicon substrate and the insulating film are etched from the back side of the substrate only in the region where the projection pattern in the substrate is created (ie, the region used as a mask) A thin film used as a mask is formed by leaving only the silicon thin film. Depending on the material of the thin film used as a mask, a silicon substrate having a thin film other than silicon formed on the surface in addition to the SOI substrate may be used.

  FIG. 13 is a conceptual diagram of electron beam projection exposure (EPL). That is, after the electron beam 2 passes through the stencil mask 5 having the opening 3 and the thin film portion 4, the scattered electron beam 6 and the non-scattered electron beam 7 pass through the projection lens 8 and subsequently pass through the limiting aperture 9. Then, the resist 11 on the wafer 12 is exposed.

  FIG. 14 is a conceptual diagram of an electron beam projection exposure (LES) apparatus. That is, the electron beam emitted from the electron gun 13 passes through the three condenser lenses 14, passes through the mask 1 on the mask stage 16, then passes through the two projection lenses, and then passes through the wafer on the wafer stage 13. 12 is exposed.

  FIG. 15 is a schematic diagram showing a planar structure of a general mask for electron beam lithography. In the portion where the pattern is formed as a mask, the silicon of the substrate is removed leaving only the thin film. That is, as shown in the figure, in the mask 1, the square thin film regions 200 are arranged in an array on the substrate 100. Within each thin film region 200, there is a transfer pattern forming region.

FIG. 16 is a schematic view illustrating a cross-sectional structure taken along line AA in FIG.
As shown in the figure, the region 300 surrounding the thin film region 200 is left with silicon of the substrate, which is called “beam”. In general, if the pattern formation region is continuously thinned over the entire surface, the distortion and deflection of the mask increase and the accuracy required for the mask cannot be realized. Therefore, the pattern formation region is divided into small regions, and the substrate is formed between them. A beam-like portion (post) 300 is formed leaving silicon.

  FIG. 17 is a schematic view illustrating a perspective structure of a B portion in FIG. 1 of a general mask 1. As shown in the figure, square thin film regions 200 are arrayed vertically and horizontally on a substrate 100, and adjacent thin film regions 200 are partitioned by beams 300.

  However, in order to realize the exposure accuracy that has been required to be further improved in recent years using the substrate silicon as a supporting substrate, it is expected that the mask itself cannot be improved in accuracy. In order to improve the accuracy of the mask, it is important to increase the rigidity of the mask, and it is necessary to realize a mechanically stronger mask.

  In order to meet such a demand, for example, a proposal to increase the thickness of the support substrate has been made (for example, see Patent Document 1). A conventional SOI substrate has a thickness of less than 1 mm, but in order to make it even thicker as a support substrate, a method of attaching a substrate having a thickness of several mm to a mask has been proposed.

FIG. 18 is a schematic view illustrating the cross-sectional structure of a conventional mask.
FIG. 18A shows a cross section of a conventional general mask. That is, a thin film region 200 formed by etching the substrate 100 and a beam portion 300 where the substrate 100 is left are present on the substrate 100.

  FIGS. 18B and 18C show a cross-sectional structure of a mask formed by bonding a reinforcing substrate 150 to the mask. That is, in the example of FIG. 18B, the reinforcing substrate 150 is bonded to the surface of the substrate 100 where the thin film region 200 is not formed. The reinforcing plate 150 has a uniform plate shape. On the other hand, in the example of FIG. 18C, a reinforcing substrate 150 is bonded to the surface on which the thin film region 200 is formed. Also in this case, the reinforcing plate 150 has a uniform plate shape.

FIG. 19 is a schematic diagram showing a planar structure of a mask to which a reinforcing substrate is bonded.
As shown in the figure, in the mask, square thin film regions 200 are arranged in an array on a substrate 100 on which a reinforcing substrate 15 is bonded. The shape of the reinforcing substrate 150 to be bonded for reinforcement is as shown in FIG. 19 in the conventional method. That is, the support substrate is pasted over the entire area except for the region to be thinned for pattern formation.

The procedure for attaching the reinforcing substrate 150 includes the case where the original substrate 100 is etched after the back surface etching is completed and the thinned region 200 of the desired region is formed, and the case where the reinforcing substrate 150 is attached first. In some cases, the thinned region 200 may be formed by etching the substrate in a desired region. In the case of pasting together after thinning as in the former case, the reinforcing substrate to be pasted needs to be processed into a shape in which a portion overlapping the thin film portion has been removed in advance before the pasting.
JP 2003-158069 A

  The method of thickening the support substrate by attaching a reinforcing substrate to the original substrate as in the conventional method has the effect of increasing the mechanical strength of the support substrate, but it increases the mass of the mask itself. Problems arise. In actual exposure, the mask is moved by driving the mask stage of the exposure apparatus. In order to secure the same acceleration as the mass of the mask increases, it is necessary to increase the driving force of the mask stage, which requires a larger stage. For this reason, there is a conflicting demand for increasing the strength and rigidity of the mask and a conflicting desire for reducing the mass, and both are required.

  Further, in a mask in which the thickness of the support substrate is increased uniformly to increase the strength, there is a concern that the deformation tends to concentrate on a relatively weak thin film portion when an excessive deformation is applied.

  The present invention has been made on the basis of recognition of such problems, and an object of the present invention is to provide a charged particle beam exposure mask having a reinforcing structure that is lightweight and can ensure sufficient strength.

In order to achieve the above object, according to the present invention,
A thin film,
A first substrate forming a column supporting the thin film;
A second substrate for reinforcing the first substrate;
With
A charged particle beam exposure mask is provided in which the second substrate has a substantially lattice beam structure.

Here, the second substrate may have a honeycomb beam structure.
Alternatively, the second substrate includes a plurality of beams extending in a radial direction about a portion held at the time of charged particle beam exposure and a plurality of beams extending in a direction substantially orthogonal to the plurality of beams. And can have.

The second substrate may have a frame-like beam structure surrounding the exposure pattern formation region.
Further, the second substrate may be a continuous plate-like portion having a thickness of the beam without forming the beam structure at a portion held in the charged particle beam exposure. it can.

  By using a reinforcing substrate having a beam structure for reinforcing the mask substrate, the mass of the mask can be suppressed while ensuring the strength and rigidity required for the substrate. Further, the strength per mass of the mask can be increased by making the beam structure of the reinforcing substrate a honeycomb structure or a lattice structure taking the load direction into consideration.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a schematic view illustrating an enlarged plan structure of a mask according to an embodiment of the present invention.
As shown in the figure, in the mask 1 according to the embodiment of the present invention, a reinforcing substrate 15 is bonded to the substrate 10. A plurality of square thin film regions 20 are arranged vertically and horizontally in an array. In the mask according to the embodiment of the present invention, the reinforcing substrate 15 is processed into a lattice shape.

FIG. 2 is a schematic view illustrating two specific examples of the cross-sectional structure of the mask according to the embodiment of the invention. In the case of the specific example shown in FIG. 2A, a reinforcing substrate 15 is bonded to the surface of the substrate 10 where the thin film region 20 is not formed. On the other hand, in the specific example shown in FIG. 2B, a reinforcing substrate 15 is bonded to the surface on which the thin film region 20 is formed.
As can be seen from these cross-sectional views, in the present embodiment, the reinforcing substrate 15 has a beam structure for the supporting substrate portion in addition to the support structure in the thin film region 20. The spacing and width of the lattice beams are determined according to the strength required for the mask, and at the same time, considering the spacing and width of the struts of the thin film region 20 where the mask pattern is formed, the same spacing as the struts. Or selecting an interval that is an integral multiple or 1 / integer of the interval between struts of the thin film region 20.

  By providing the reinforcing substrate 15 with the above-described structure, the mass of the member (reinforcing substrate 15) can be reduced, and the strength per unit mass can be increased against bending of the substrate. it can.

  FIG. 3 is a schematic diagram for explaining a bending moment of a mask according to an embodiment of the present invention and a conventional mask. That is, FIGS. 4A and 4B are cross-sectional views of two arbitrary positions in the conventional mask, and FIG. 4C is a vertical cross-sectional view of the beam portion of the substrate 15 in the mask of the present invention. FIG. 4D is a cross-sectional view of the beam portion of the substrate 15 in the mask of the present invention. Here, in the mask of the present invention, the thickness of the reinforcing substrate 15 is doubled and half of the area is removed.

When the strengths of the masks shown in FIGS. 3A and 3B and the masks shown in FIGS. 3C and 3D are compared, the mass of the reinforcing substrate 15 is the same, but the thickness of the bending strength of the substrate is the same. Is doubled and the surface area is halved (FIGS. 3 (c) and 3 (d)) are stronger against external forces such as "bending". That is, the mask strength (rigidity) per mass can be increased by processing the reinforcing substrate 15 into a lattice structure as in the present invention.
Further, in the structure of the conventional reinforcing substrate illustrated in FIG. 19, the rigidity of the substrate is extremely different between the thin film region 20 in which the support has a lattice structure and the region of the reinforcing substrate portion where the substrate is left on the entire surface, There was a concern that deformation caused by external force or the like is more likely to concentrate on the thin film portion. On the other hand, according to the present invention, since the reinforcing substrate also has a beam structure, the difference in rigidity between the reinforcing substrate portion and the thin film region is reduced, and the effect of reducing the concentration of deformation in the thin film region is also achieved. can get.

  Hereinafter, embodiments of the present invention will be described in more detail with reference to examples.

  FIG. 4 is a schematic view illustrating the planar structure of the mask according to the first embodiment of the invention. As shown in the figure, in the mask 1 according to the embodiment of the present invention, a reinforcing substrate 15 is bonded to the substrate 10. A plurality of square-shaped thin film regions 20 are arranged in rows and columns. In the mask according to the first embodiment of the present invention, the reinforcing substrate 15 is processed into a honeycomb shape.

  The honeycomb structure is generally configured to obtain the maximum strength with the minimum material, and the mass can be reduced by obtaining the same rigidity as the above-described lattice structure with respect to bending of the mask surface, external force in the surface direction, bending, and the like. There is an effect, or a mask having higher rigidity can be produced with the same mass as the lattice structure. That is, the same effect as the mask obtained by processing the reinforcing substrate into a lattice shape can be obtained.

Next, a second embodiment of the present invention will be described.
FIG. 5 is a schematic view illustrating the planar structure of a mask according to the second embodiment of the invention. As shown in the figure, in the mask 1 according to the embodiment of the present invention, a reinforcing substrate 15 is bonded to the substrate 10. A plurality of square-shaped thin film regions 20 are arranged in rows and columns. In the mask according to the second embodiment of the present invention, the reinforcing substrate 15 is left as it is in the region 40 where the mask is attracted and held by a vacuum chuck, an electrostatic chuck or the like among the reinforcing substrate 15, and the rest The region excluding the thin film region has a lattice beam structure. By leaving the reinforcing substrate 15 of the portion to be chucked as it is, it becomes possible to suppress deformation at the time of chucking.

  FIG. 6 shows a region where the mask 1 is attracted and held by a vacuum chuck, an electrostatic chuck or the like when the exposure apparatus or measurement apparatus holds the mask 1. That is, the area other than the square inscribed in the circular mask 1 becomes the area 40 occupied to attract and hold the mask 1 with a vacuum chuck or an electrostatic chuck. If the reinforcing substrate 15 in this portion has the above-described lattice-like or honeycomb-like structure, there is a concern that the adsorptive power is reduced. In order to solve this problem, it is effective to eliminate the beam structure of the reinforcing substrate in the region 40 where the apparatus sucks the mask.

By adopting the structure described above, it is possible to avoid the problem of reducing the attractive force for holding the mask and to secure the necessary rigidity while reducing the mass of the mask.
FIG. 7 is a schematic view illustrating the planar structure of the mask according to the second embodiment of the invention. As shown in the figure, in the mask 1 according to the embodiment of the present invention, a reinforcing substrate 15 is bonded to the substrate 10. A plurality of square-shaped thin film regions 20 are arranged in rows and columns. In the mask according to the second embodiment of the present invention, the reinforcing substrate 15 is left as it is in the region 40 where the mask is attracted and held by a vacuum chuck, an electrostatic chuck or the like among the reinforcing substrate 15, and the rest The region except the thin film region has a honeycomb-like beam structure.

Next, a third embodiment of the present invention will be described.
FIG. 8 is a schematic view illustrating the planar structure of a mask according to the third embodiment of the invention. As shown in the figure, in the mask 1 according to the embodiment of the present invention, a reinforcing substrate 15 is bonded to the substrate 10. A plurality of square-shaped thin film regions 20 are arranged in rows and columns. The mask reinforcing substrate 15 according to the third embodiment of the present invention has a beam radially extending from an area adsorbed when the exposure apparatus or measurement apparatus holds the mask, and a perpendicular to the beam. A beam structure is formed by beams that intersect in the direction. The thin film region 20 and other regions to be sucked and held are connected by beams extending radially from each of the regions 40 for sucking and holding the mask, and the beams are also passed in a direction orthogonal to the radially extending beams. The beam structure is formed.

  It is known that the grid-like beam structure is the strongest against the force acting in the beam running direction. Considering the area that the device will hold by suction when actually measuring and exposing the mask, its holding area By arranging the beams in a direction extending radially from the mask, the mask can be made stronger against an external force applied to the mask when the mask is held.

Next, a fourth embodiment of the present invention will be described.
FIG. 9 is a schematic view illustrating the planar structure of a mask according to the fourth embodiment of the invention. As shown in the figure, in the mask 1 according to the embodiment of the present invention, a reinforcing substrate 15 is bonded to the substrate 10. A plurality of square-shaped thin film regions 20 are arranged in rows and columns. The mask according to the fourth embodiment of the present invention is a reinforcing substrate structure in the case where a thick beam is formed in a region surrounding the periphery of the thin film region 20 based on the reinforcing substrate 15 having a honeycomb structure formed in the supporting substrate portion. FIG. That is, the square area inscribed in the circular mask 1 in the reinforcing substrate 15 has a honeycomb structure, and the other area 40 (area where the mask 1 is attracted and held by a vacuum chuck or an electrostatic chuck) is a hole. Of the thin film region 20 is a thick beam.
In the mask, the region where the rigidity is particularly desired to be increased and the deformation due to external force or gravity is minimized is the thin film region 20 for forming the exposure pattern. It is an effective means to further increase the rigidity of the thin film portion, and at the same time, it is also an effective means to release the distortion and deformation of the mask to areas other than the thin film portion by relatively reducing the rigidity of other portions. It is. Therefore, there is an aim to increase the rigidity of the thin film portion by surrounding the thin film portion with a thick beam.
FIG. 10 is a schematic view illustrating the planar structure of a mask according to the fourth embodiment of the invention. That is, it is a conceptual diagram showing the structure of the reinforcing substrate 15 when a thick beam surrounding the periphery of the thin film region 20 is formed on the reinforcing substrate 15 similarly using a radial beam structure.

  The thick beam formed so as to surround the thin film portion in this way can increase the rigidity of the thin film portion, and reduce the influence of external force on the thin film portion when the exposure apparatus or measurement device holds the mask. Can do. In order to further reduce the influence of external force, it is effective to lower the rigidity of the area between the thin film part and the suction holding part. It is possible to further reduce the number of beams in this area or make the beams thinner. It is also an effective means.

  FIG. 11 is a schematic diagram illustrating a modification of the present embodiment. That is, as a typical example of actively reducing the rigidity of the region between the thin film region 20 and the suction holding region 40, all the beams of the reinforcing substrate in the region between the thin film region 20 and the suction holding region 40 are used. It has been removed. In this case, the suction holding part and the thin film part are held only by the original mask substrate.

  FIG. 12 is a schematic diagram showing still another modification of the present embodiment. That is, from the viewpoint of reinforcing only the thin film portion, the structure of the reinforcing substrate may be as shown in FIG. In this case, the reinforcing substrate is only the pillar of the thin film portion and the thick beam surrounding the thin film portion, and the region other than the thin film portion is not reinforced.

  The embodiments of the present invention have been described above with reference to specific examples. However, the present invention is not limited to these specific examples.

  For example, regarding the specific shape, structure, material, size, etc. of each element such as the substrate constituting the charged particle beam exposure mask and the reinforcing substrate, those appropriately designed by those skilled in the art other than those described above, As long as the gist of the present invention is included, it is included in the scope of the present invention.

Further, as a specific example, the structure, number, and arrangement relationship of the thin film regions are merely examples.
In addition, all charged particle beam exposure masks that include the elements of the present invention and that can be appropriately modified by those skilled in the art are included in the scope of the present invention.

It is a schematic diagram which expands and illustrates the planar structure of the mask concerning embodiment of this invention. It is a schematic diagram which illustrates the cross-section of the mask concerning embodiment of this invention. It is the schematic diagram which compares and illustrates the bending moment of the mask which concerns on the Example of this invention, and the conventional mask. It is a schematic diagram which illustrates the planar structure of the mask concerning the 1st Example of this invention. It is a schematic diagram which illustrates the planar structure of the mask concerning the 2nd Example of this invention. An area in which the mask 1 is attracted and held by a vacuum chuck, an electrostatic chuck or the like when the exposure apparatus or measurement apparatus holds the mask 1 is shown. It is a schematic diagram which illustrates the planar structure of the mask concerning the 2nd Example of this invention. It is a schematic diagram which illustrates the planar structure of the mask concerning the 3rd Example of this invention. It is a schematic diagram which illustrates the planar structure of the mask concerning the 4th Example of this invention. It is a schematic diagram which illustrates the planar structure of the mask concerning the 4th Example of this invention. It is a schematic diagram showing the modification of 4th Example. It is a schematic diagram showing the further another modification of 4th Example. It is a conceptual diagram of electron beam projection exposure (Electron Projection Lithography (EPL)). It is a conceptual diagram of an electron beam projection exposure (LES) apparatus. It is a schematic diagram showing the planar structure of the mask for general electron beam lithography. It is a schematic diagram which illustrates the cross-section in the AA in FIG. FIG. 2 is a schematic view illustrating a perspective structure of a B portion in FIG. 1 of a general mask 1. It is a schematic diagram which illustrates the cross-sectional structure of the conventional mask. It is a schematic diagram showing the planar structure of the mask which has bonded the board | substrate for reinforcement.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Mask 2 Electron beam 3 Opening part 4 Thin film part 5 Stencil mask 6 Scattered electron beam 7 Non-scattered electron beam 8 Projection lens 9 Limiting aperture 10 Substrate 11 Resist 12 Wafer 13 Electron gun 14 Capacitor lens 15 Reinforcing substrate 16 Wafer stage 20 Thin film Area 40 Adsorption holding area 100 Substrate 150 Reinforcing plate 200 Thin film area 300 Beam

Claims (5)

A thin film,
A first substrate forming a column supporting the thin film;
A second substrate for reinforcing the first substrate;
With
The charged particle beam exposure mask, wherein the second substrate has a substantially lattice beam structure.   2. The charged particle beam exposure mask according to claim 1, wherein the second substrate has a honeycomb-shaped beam structure.   The second substrate includes a plurality of beams extending in a radial direction about a portion held at the time of charged particle beam exposure, and a plurality of beams extending in a direction substantially orthogonal to the plurality of beams. The charged particle beam exposure mask according to claim 1, comprising:   The charged particle beam exposure mask according to claim 1, wherein the second substrate has a frame-like beam structure surrounding an exposure pattern formation region. The said 2nd board | substrate is a continuous plate-shaped part which does not form the said beam structure in the site | part hold | maintained in the case of the said charged particle beam exposure, and has the thickness of the said beam. The charged particle beam exposure mask according to any one of 1 to 4.