JP2004288810A - Electron beam exposure apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain a high precision exposure pattern in an electron beam exposure apparatus performing exposure by scanning a mask having a plurality of pattern regions with an electron beam. <P>SOLUTION: The electron beam exposure apparatus is provided with a mask 30 having a plurality of pattern regions 34A-34D sectioned by beams 36, and electron optics systems 12 and 20 for irradiating the mask with an electron beam 15 larger than the width of the beam and irradiating a sample with an electron beam shaped by the opening pattern of each pattern region 34A-34D. Shield mechanisms 70A-70D for preventing the electron beam from impinging on at least a part of the plurality of pattern regions are provided on the electron beam incident side of the mask 30. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an electron beam exposure apparatus that performs exposure by irradiating a sample with an electron beam that is shaped by passing through an opening pattern of a mask, and more particularly, to an electron beam using a mask having a plurality of pattern areas divided by beams. The present invention relates to an exposure apparatus.
[0002]
[Prior art]
At present, in a lithography technique for forming a pattern on a wafer in a semiconductor device (device) manufacturing process, optical lithography for reducing and exposing a pattern of a light exposure mask (photomask) on the wafer is mainly used. It is becoming difficult to miniaturize, and an electron beam exposure method capable of further miniaturization has attracted attention. There are various electron beam exposure methods. From the viewpoint of throughput, EPL (Electron Projection Lithography) and LEEPL (Low Energy Electron-beam Proximity Projection Lithography) are particularly attracting attention. The EPL uses a mask four times as large as the exposure pattern and performs exposure at a high acceleration voltage of 100 kV. On the other hand, LEEPL uses a same-size mask and performs exposure at a low acceleration voltage of about 2 kV. Both EPL and LEEPL use a stencil mask (apertured mask) having an opening pattern corresponding to the exposure pattern.
[0003]
FIG. 1 is a diagram showing a basic configuration of an electron beam proximity (LEEEPL) exposure apparatus 10 for performing exposure using a stencil mask of the same magnification. As shown, an electron gun 12 including an electron beam source 14 for generating an electron beam 15, a lens 16 for converting the electron beam 15 into a parallel beam, and a shaping aperture 18, a main deflector 22, 24 and a sub deflector 26, 28 And a scanning mechanism 20 that scans while holding the electron beam parallel to the optical axis, a mask 30, an electrostatic chuck 50 that holds a sample (wafer) 40, and a θXY stage 60. These parts are provided in a vacuum chamber. The mask is held by a mask holding mechanism (not shown), and is exchanged according to a pattern to be exposed.
[0004]
The mask 30 is arranged so as to be close to the wafer 40 attracted to the electrostatic chuck 50 (so that the gap between the mask 30 and the wafer 40 is, for example, 50 μm). In this state, when the mask 30 is irradiated with an electron beam vertically, the shaped electron beam that has passed through the mask pattern of the mask 30 is irradiated on the resist layer 42 on the wafer 40 to expose the pattern.
[0005]
Since it is difficult to generate a uniform electron beam covering the entire pattern area of the mask 30, the entire surface of the mask 30 is scanned with the electron beam 15 as shown in FIG. Exposure. The scanning mechanism 20 performs this scanning. In order to improve the uniformity of the exposure amount, it is desirable to perform scanning at a small scanning pitch using the large electron beam 15.
[0006]
The pattern of the stencil mask 30 is an opening (perforated) pattern, and the pattern formed there is a very fine pattern, and the pattern portion of the mask 30 needs to be a very thin membrane. May be distorted. The LEEPL exposure apparatus 10 performs exposure while correcting distortion using the sub deflectors 26 and 28. FIG. 3 is a diagram illustrating this correction principle. As shown in the figure, the electron beam 15 deflected to the scanning position by the main deflectors 22 and 24 and vertically incident on the mask 30 is deflected by an angle -α by the sub deflector 26 and doubled in the reverse direction by the sub deflector 28. Is deflected by the angle 2α. As a result, the electron beam 15 enters the predetermined deflection position at an angle α. Then, assuming that a gap (gap) between the mask 30 and the wafer 40 is G, exposure is performed at a position shifted by δ = αG. The distortion of the mask pattern is measured in advance, and the exposure position is shifted by changing the angle of incidence on the mask 30 according to the distortion to correct the distortion of the mask pattern.
[0007]
The mask used in the LEEPL exposure apparatus is a stencil mask having an opening pattern, and cannot have an annular pattern. Therefore, the annular pattern is divided into a plurality of mask patterns, and exposure is realized by combining the plurality of mask patterns. Even if the pattern is not an annular pattern, there is a pattern shape that is not suitable for the pattern of the stencil mask. In such a case, the exposure using a plurality of mask patterns is combined.
[0008]
When a plurality of such patterns are formed on different masks, it is necessary to exchange the masks to expose one pattern, which lowers the throughput. Therefore, JP-A-2002-369885 and JP-A-2002-373845 disclose a single mask provided with a plurality of mask patterns, forming a pattern constituting a complementary pattern on each mask pattern, and forming one mask. A LEEPL exposure method and apparatus that can be used to expose all of one pattern is disclosed.
[0009]
From the viewpoint of throughput, it is desirable to be able to expose as wide a range as possible with one exposure. For example, JP-A-2002-368885 and JP-A-2002-373845 disclose that one mask pattern is one chip (die). Are disclosed which have a size corresponding to the entire region.
[0010]
In particular, Japanese Patent Application Laid-Open No. 2002-373845 discloses that a plurality of mask patterns are arranged corresponding to the arrangement of dies on a wafer, and after alignment, the plurality of mask patterns are exposed, and the position is adjusted by the size of the mask pattern. An exposure method and apparatus for exposing a plurality of dies in a single alignment by performing the next exposure with the alignment shifted are disclosed.
[0011]
FIG. 4 is a view for explaining an arrangement of a mask pattern and an exposure method in a mask disclosed in JP-A-2002-373845. As shown in FIG. 4A, on the mask 30, four mask patterns 34 are arranged in two rows and two columns (2 × 2) as shown. Beams 36 between the mask patterns are thicker than the membrane of the mask pattern 34. As shown in FIG. 4B, the dies 46 formed on the wafer 40 are arranged at the same pitch as the arrangement of the mask patterns 34 on the mask 30. Exposure of four mask patterns is performed by aligning the mask pattern 34 with the position of each die 46, and then exposure is performed while shifting the arrangement pitch of the die and the mask pattern. Therefore, each die is synthesized by exposure using the four mask patterns. Through such an exposure method, the throughput is greatly improved. Here, an example in which four mask patterns are provided on the mask has been described. However, if only a complementary pattern is exposed, two mask patterns may be provided. Further, Japanese Patent Application Laid-Open No. 2002-368885 discloses that a plurality of groups of two or three patterns obtained by dividing a complementary pattern in one mask are provided, and an exposure amount is divided to reduce the influence of a defect or the like. Discloses a configuration in which exposure can be continued without exchanging a mask even when a defect or the like occurs. In this case, many mask patterns are formed on one mask.
[0012]
[Patent Document 1]
JP 2002-368885 A (whole)
[Patent Document 2]
JP 2002-373845 A (Overall)
[0013]
[Problems to be solved by the invention]
As described with reference to FIG. 2, in the LEEPL exposure apparatus, the uniformity of exposure is improved by scanning the mask pattern with the electron beam 15, and the electron beam 15 is preferably large in order to improve the throughput. .
[0014]
Further, as shown in FIG. 4, when a plurality of mask patterns 34 are arranged on the mask 30 at the arrangement pitch of the die and the plurality of mask patterns are exposed by one alignment, the beams 36 between the mask patterns are exposed. The width is equal to the die spacing. The distance between the dies is required to be able to form dicing grooves for dividing the dies after the process is completed, and the minimum width is determined from the dicing relationship. Then, in order to use the wafer efficiently, it is desirable to make the interval between the dies as small as possible, and the value is set to a value close to the above-mentioned minimum width.
[0015]
FIG. 5 is a diagram showing a state in which the four mask patterns 34A to 34D formed on the mask are scanned by the electron beam 15. As described above, the beam 36 is set to have a certain width, and the electron beam 15 needs to be larger than a certain size, and the diameter of the electron beam 15 may be larger than the width of the beam 36. In this case, if there is no need to correct the distortion of the mask pattern, no particular problem occurs. However, as described with reference to FIG. 3, when adjusting the incident angle of the electron beam 15 to the mask 30, the distortion is adjusted. Occurs. FIG. 5B illustrates this problem. When the diameter of the electron beam 15 is larger than the width of the beam 36, the electron beam 15 is simultaneously applied to the left portion of the adjacent mask pattern 34A, the right portion of the mask pattern 34B, and the beam 36 therebetween. In order to remove the distortion of the left mask pattern 34A, it is necessary to make the electron beam 15 be inclined to the right as shown by the solid line and to enter the electron beam 15. To remove the distortion of the right mask pattern 34B, as shown by the broken line. When the electron beam 15 needs to be incident on the left side, the left side portion of the mask pattern 34A is combined with the electron beam incident on the left side and the electron beam incident on the left side, Since there is a shift in the exposure position, the exposure pattern deteriorates. This is the same for the right portion of the mask pattern 34B.
[0016]
In addition, when arranging a plurality of mask patterns on one mask, when it is required not to expose a defective mask pattern or a spare mask pattern, or when exposing a complementary mask, the above-described method is used. If the diameter of the electron beam 15 is larger than the width of the beam 36, a part of the mask pattern that does not need to be exposed when exposing an adjacent mask pattern is exposed, thereby causing exposure unevenness and degrading the exposure pattern. Problem arises.
[0017]
In order to prevent such a problem from occurring, it is conceivable to make the width of the beam wider than the diameter of the electron beam. However, in this case, the number of dies that can be formed on one wafer decreases and the cost increases. The problem arises. It is also conceivable to make the diameter of the electron beam smaller than the width of the beam. However, if the beam current is increased to increase the throughput, the beam diameter increases due to the Coulomb effect or the like, so that the beam diameter cannot be set to an arbitrary value, and it is difficult to make the diameter of the electron beam smaller than the beam width.
[0018]
An object of the present invention is to solve such a problem and to realize an electron beam exposure apparatus capable of obtaining a highly accurate exposure pattern.
[0019]
[Means for Solving the Problems]
In order to achieve the above object, the electron beam exposure apparatus of the present invention is provided with a shielding mechanism for shielding at least a part of the plurality of pattern regions (mask patterns) so that the electron beam does not enter.
[0020]
That is, the electron beam exposure apparatus of the present invention includes a mask having a plurality of pattern regions divided by beams, and irradiating the mask with an electron beam having a width larger than the width of the beams. An electron beam exposure apparatus comprising: an electron optical system that irradiates the sample with the shaped electron beam, provided on the incident side of the electron beam of the mask, at least a part of the plurality of pattern regions. It is characterized by comprising a shielding mechanism for shielding the region so that the electron beam does not enter.
[0021]
FIG. 6 is a view for explaining the principle of the electron beam exposure apparatus of the present invention. As shown in the figure, the mask is provided with a plurality of pattern regions (mask patterns) 34A-34D of at least one chip, and a movable shielding plate 70A- is provided on the electron beam incident side of each pattern region. 70D is provided. The shielding plate of the pattern area used for exposure moves to a position where the area is not shielded, and the shielding plate of the pattern area not used for exposure moves so as to shield the area.
[0022]
According to the present invention, even if the diameter of the electron beam is larger than that of the beam, the pattern area not used for exposure can be shielded, so that the exposure pattern does not deteriorate. If the angle of incidence on the mask to correct the distortion is different in the adjacent pattern area, one of the pattern areas is shielded, the other is exposed, and then the other is shielded. One pattern area is exposed. As a result, the processing time is lengthened by the time required to change the shielding state, but the mask does not need to be replaced, and no significant reduction in throughput occurs.
[0023]
The shielding mechanism includes a shielding plate that blocks an electron beam from entering the pattern area. This shield plate is desirably a grounded conductor because the electron beam is irradiated.
[0024]
BEST MODE FOR CARRYING OUT THE INVENTION
The electron beam exposure apparatus according to the first embodiment of the present invention irradiates a sample (wafer) with an electron beam shaped by passing through a stencil mask (perforated mask) such as an EPL exposure apparatus or a LEEPL exposure apparatus. An apparatus in which a plurality of mask patterns are formed on a mask, and a beam between adjacent mask patterns is smaller than the diameter of the electron beam. The present invention is characterized by a mask shielding mechanism, and the other parts have been described so far and are well known, so that detailed description is omitted here.
[0025]
FIG. 7 is a view showing a mask shielding mechanism of the electron beam exposure apparatus according to the first embodiment, which realizes the configuration shown in FIG. As shown in FIG. 7A, the shielding plate 70A is movable along the guide 72A, and sets the mask pattern 34A in a shielding state and a non-shielding state. Similarly, the shielding plates 70B, 70C, and 70D are movable along the guides 72B, 72C, and 72D, and bring the mask patterns 34B, 34C, and 34D into a shielding state and a non-shielding state. The guides 72A to 72D are provided so as to extend in different directions by 90 °. Each of the shielding plates 70A-70D is made of a conductor, and is connected to the ground (grounded).
[0026]
FIG. 7B illustrates a moving mechanism. As shown, a first arm 93 is fixed to a rotation shaft 92 of a motor 91, and the first arm 93 rotates with the rotation of the motor 91. A second arm 95 is engaged with the distal end of the first arm 93 via a free rotation shaft 94. The tip of the second arm 95 is engaged with a free rotation shaft 96 provided on the shielding plate 70. The movement direction of the shield plate 70 is regulated by the guide 72. When the motor 91 rotates and the first arm 93 rotates, the second arm 95 rotates and the shield plate 70 moves.
[0027]
In the shielding mechanism of the first embodiment, the four mask patterns 34A to 34D can be shielded independently of each other.
[0028]
FIG. 8 is a view showing a shielding mechanism of the electron beam exposure apparatus according to the second embodiment of the present invention. The shielding mechanism of the second embodiment attaches a shielding plate 34A-34D to the tip of an arm 76A-76D that rotates about a rotation axis 74A-74D, and rotates the shielding plate 34A-34D to thereby rotate the mask pattern 34A. -34D is in a shielded state and a non-shielded state. The shielding mechanism of the second embodiment can also shield the four mask patterns 34A-34D independently of each other.
[0029]
FIG. 9 is a view showing a shielding mechanism of the electron beam exposure apparatus according to the third embodiment of the present invention. As shown in FIG. 9A, the shielding mechanism of the third embodiment includes a shielding plate 80 having a large opening 82 capable of keeping all four mask patterns 34A-34D in a non-shielding state, and using the shielding plate 80 as a mask. And a moving mechanism (not shown) that moves in two axial directions in parallel. When the four mask patterns 34A-34D are all set to the non-shielding state, the shielding plate 80 is moved to the state shown in FIG. 9A, and when only the mask pattern 34A is set to the non-shielding state, the shielding plate 80 is moved to the state shown in FIG. When the mask plate 34B is moved to the state of FIG. 9B and only the mask pattern 34B is set in the non-shielding state, the shielding plate 80 is moved to the state of FIG. 9C and only the mask pattern 34C is set in the non-shielding state. The shielding plate 80 is moved to the state shown in FIG. The same applies when only the mask pattern 34D is set in the non-shielding state. When the mask patterns 34A and 34B are in the non-shielding state and the mask patterns 34C and 34D are in the shielding state, the shielding plate 80 is moved to the state of FIG. 9E, and the mask patterns 34B and 34C are in the non-shielding state. When setting the mask patterns 34A and 34D in the shielding state, the shielding plate 80 is moved to the state shown in FIG. The same applies to the case where a set of adjacent mask patterns is set to the unshielded state and another set of adjacent mask patterns is set to the shielded state.
[0030]
【The invention's effect】
As described above, according to the present invention, a highly accurate exposure pattern can be obtained in an electron beam exposure apparatus that performs exposure by scanning a mask having a plurality of pattern regions (mask patterns) with an electron beam.
[Brief description of the drawings]
FIG. 1 is a diagram showing a basic configuration of a proximity exposure (LEEEPL) electron beam exposure apparatus.
FIG. 2 is a diagram showing scanning of a mask by an electron beam.
FIG. 3 is a diagram illustrating distortion correction using a sub deflector in a proximity exposure type electron beam exposure apparatus.
FIG. 4 is a diagram illustrating an exposure method disclosed in Japanese Patent Application Laid-Open No. 2002-373845 using a mask in which a plurality of mask patterns are arranged in accordance with the arrangement of dies on a wafer.
FIG. 5 is a diagram for explaining a problem caused by performing distortion correction by adjusting an incident angle on a mask when a width of a beam between mask patterns is smaller than an electron beam.
FIG. 6 is a diagram illustrating the principle of the present invention.
FIG. 7 is a view showing a shielding mechanism according to the first embodiment of the present invention.
FIG. 8 is a view showing a shielding mechanism according to a second embodiment of the present invention.
FIG. 9 is a view showing a shielding mechanism according to a third embodiment of the present invention.
[Explanation of symbols]
12 electron gun 15 electron beam 20 scanning means 30 mask 34, 34A-34D pattern area (mask pattern)
40 ... Sample (wafer)
50: electrostatic chuck 60: θXY stage 70, 70A-70D: shielding plate

Claims (6)

A mask having a plurality of pattern regions separated by beams,
An electron optical system for irradiating the mask with an electron beam having a diameter larger than the width of the beam, shaping the electron beam with an opening pattern in each pattern region, and irradiating the sample with the shaped electron beam. And
An electron beam exposure apparatus, comprising: a shielding mechanism provided on an incident side of the electron beam of the mask to shield at least a part of the plurality of pattern regions so that the electron beam does not enter. The electron beam exposure apparatus according to claim 1,
An electron beam exposure apparatus, wherein the shielding plate of the shielding mechanism is a grounded conductor. The electron beam exposure apparatus according to claim 1 or 2,
An electron beam exposure apparatus, wherein the electron optical system includes a scanning mechanism that scans the mask with the electron beam. The electron beam exposure apparatus according to any one of claims 1 to 3,
An electron beam exposure apparatus, wherein the mask is arranged close to the sample, and the sample is directly irradiated with the shaped electron beam passing through the plurality of pattern regions. The electron beam exposure apparatus according to any one of claims 1 to 4,
The size of each pattern region is an electron beam exposure apparatus having a pattern region for at least one chip of a plurality of semiconductor devices formed on the sample. The electron beam exposure apparatus according to claim 5,
An electron beam exposure apparatus, wherein the plurality of pattern areas have mutually complementary patterns in different pattern areas.

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