JPH0562892A - Pattern forming equipment - Google Patents

Abstract

(57) [Abstract] [Purpose] The space charge effect is made approximately the same between the variable beam exposure beam and the reduced exposure beam, eliminating the need for the conventional focus adjustment each time the beam changes, and The beam size of the filled pattern with low area precision is increased to achieve high throughput. An electron gun 1 for generating a beam for exposure, first and second aperture masks 2, 4 for shaping the beam generated by the electron gun 1, a first aperture 8b for reduction exposure, and a variable beam Generated from the mask 8 provided with the second aperture 8a for exposure and the electron gun 1,
The beam whose shape and size are changed by the first and second aperture masks 2 and 4 is the first aperture 8b.
And deflectors 5a and 5b for deflecting the variable beam so that the variable beam is incident on either one of the second aperture 8a and the second aperture 8a, and the area of the reduction exposure beam emitted from the first aperture 8b is set to the second aperture. The maximum area of the variable beam exposure beam emitted from 8a is limited to 1.5 to 2.0 times.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention selects either the first aperture for reduction exposure or the second aperture for variable beam exposure, and exposes the exposure beam on the substrate through the selected aperture. The present invention relates to a pattern forming apparatus for forming a desired pattern by forming an image on the exposure area.

[0002]

2. Description of the Related Art For example, when a semiconductor memory is formed on a wafer, precision is required because a fine circuit pattern that requires repetition and has a high precision like a memory cell and a large area such as a dicing line and a bonding pad. It is necessary to print patterns that you do not need much. When a pattern of this kind is formed by an electron beam exposure apparatus, a pattern having a narrow line width can be printed as compared with a reduction projection exposure apparatus called a stepper.
Since the pattern is printed with a so-called one-stroke drawing, the throughput is poor. Then, for example, JP-A-61-2824
As disclosed in Japanese Patent Laid-Open No. 5 (1994), it has been attempted to improve the throughput by changing the size of the electron beam according to the pattern to be printed.

However, even with this method, the fine pattern is not much different from the one-stroke drawing, and the throughput does not reach that of the reduction projection exposure apparatus as represented by the stepper. Therefore, a pattern with a large area such as a dicing line or a bonding pad, or a random pattern that is fine but does not repeat is drawn with a variable-dimension beam as in the past (in the present specification, this is variable. On the other hand, in the case of repetitive patterns, on the other hand, an aperture corresponding to the shape of a pattern containing a plurality of basic patterns is created on a mask, and the apertures on the mask are sequentially irradiated with a beam of a predetermined size, and a reduction lens Attempts are being made to bring the throughput closer to that of a step-and-repeat type reduction projection exposure apparatus by sequentially printing (this is referred to as reduction exposure in this specification) on a wafer through the through.

[0004]

However, the space charge effect is considerably different between the beam used for variable beam exposure and the beam used for reduction exposure, and even at the time of reduction exposure, there is a high density (incident beam). The space charge effect is significantly different between a beam having a large filling factor indicating the ratio of the beam passage area to the area and a beam having a low density (small filling factor). The different space charge effects lead to different beam focusing conditions, so that the exposure beam is changed each time the exposure beam is used, that is, the first aperture for reduction exposure or the second aperture for variable beam exposure is selected. It is necessary to adjust the focus with an electronic lens, etc., and improvement in throughput cannot be expected.

Further, when the focus is adjusted by the electrostatic lens or the like, the position of the beam on the substrate is slightly changed. Therefore, if accuracy is required, it is necessary to correct the misalignment, but this misalignment changes depending on the height position of the substrate surface and the values of the main deflection and the sub-deflection. Is quite complicated. Therefore, the arithmetic device becomes complicated and the arithmetic time is required, and the throughput is lowered.

Further, a pattern having a large area, such as the above-mentioned dicing line and bonding pad, which does not require high accuracy, is 2 × 10 ⁶ μm ² per chip.
It has a size of about 2 × 10 ⁸ μm ^{2 for} 100 chips.
It becomes the area. When you paint with a beam of 1 μm × 1 μm,
It requires 2 × 10 ⁸ shots, and if one shot is 0.5 μs, it takes 100 seconds, which lowers the throughput.

An object of the present invention is to make the space charge effect substantially the same between the variable beam exposure beam and the reduced exposure beam, thereby eliminating the need for the conventional focus adjustment each time the beam changes, and further It is an object of the present invention to provide a pattern forming apparatus that achieves high throughput by increasing the beam size of a filled pattern with low area accuracy.

[0008]

SUMMARY OF THE INVENTION According to the present invention, a beam generating means for generating an exposure beam, a beam shaping means for shaping a beam generated by the beam generating means, and a first aperture for reduction exposure are variable. A mask provided with a second aperture for beam exposure and a beam generated by the beam generating means and shaped by the beam shaping means are incident on either one of the first aperture and the second aperture. The present invention is applied to a pattern forming apparatus having a deflecting means for deflecting a variable beam. Then, the area of the reduction exposure beam emitted from the first aperture is
The above-mentioned object is achieved by limiting the maximum area of the variable beam exposure beam emitted from the second aperture to 1.5 to 2.0 times. In the pattern forming apparatus according to claim 2, the maximum area of the variable beam exposure beam is 4
The mask is provided with a third aperture for filling having an area equal to or more than twice, and the variable beam is made incident on the third aperture by the deflecting means at the time of the fill exposure.
The exposure beam is imaged on the substrate through the aperture.

[0009]

When the beam areas emitted from the first and second apertures are the same and therefore the beam currents are also the same, the beam image transmitted through the first aperture during reduction exposure is generally concentrated at one place. The spatial charge effect of the beam during the reduction exposure is smaller than the spatial charge effect of the beam during the variable beam exposure because the spatial charge effect is not distributed. Therefore, in order to make the space charge effects of both beams almost equal, the beam area emitted from the first aperture during the reduction exposure is set to the second area during the variable beam exposure.
It can be made larger than the beam area emitted from the aperture. In the present invention, the area of the exposure beam emitted from the first aperture during reduction exposure is limited to about 1.5 to 2.0 times the area of the exposure beam emitted from the second aperture during variable beam exposure. As a result, the space charge effect of the beam is made substantially equal during the variable beam exposure and the reduction exposure, and it becomes unnecessary to adjust the focus each time the beam is changed. Further, according to claim 2, a pattern having a large area and requiring less accuracy is exposed by using a third aperture having an area which is four times or more the size of the beam for variable beam exposure incident on the second aperture. To be done. Therefore, the throughput is improved.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A pattern forming apparatus according to the present invention will be described with reference to FIGS. FIG. 1 shows a schematic configuration of the pattern forming apparatus. In FIG. 1, the electron beam output from the electron gun 1 is shaped into a rectangular beam by a first aperture mask 2 having a square opening 2a as shown in FIG. 2 (a). This rectangular beam is imaged on the second aperture mask 4 by the condenser lens 3.

The second aperture mask 4 is shown in FIG.
As shown in (b), 16 rectangular openings are provided. In this embodiment, one of the openings 4a is a small rectangular opening for variable beam exposure, and 14 openings 4b are for reduced exposure. Is a large rectangular opening, and the remaining one opening 4c is a large rectangular opening for solid exposure.

The rectangular aperture 4a for variable beam exposure is set so that its area is ¼ of the area of the rectangular aperture 4b for reduced exposure. As a result, the beam travels from the second aperture mask 4 to the mask 8 to be described later, as compared with the conventional case where the area of the variable beam exposure beam is set to a large area similar to the rectangular opening 4b of the reduced exposure beam. The space charge effect during the operation can be reduced to 1/4.

An aperture selection deflector 5 is arranged between the first aperture mask 2 and the second aperture mask 4.
a and 5b are provided, and the deflectors 5a and 5b provide the first
The rectangular beam passing through the aperture mask 2 of 1 is deflected to select any one opening on the second aperture mask 4. The crossover image 51 is deflected.
The sensitivity ratios of the deflectors 5a and 5b are set so that does not move.

Here, as shown in FIG. 2B, the opening size of the rectangular opening 4b of the second aperture mask 4 is a,
When the pitch is b, the openings 2 of the first aperture mask 2 formed on the second aperture mask 4 are formed.
The size of the opening 2a of the first aperture mask 2 is determined so that the size of the image 2a 'of a becomes a + b.
Therefore, when exposing the substrate, the deflectors 5a, 5b are
It is not necessary to wait for the exposure until the applied voltage of the second aperture mask 4 is set to the correct value, and the image 2a ′ on the second aperture mask 4 is
The exposure operation can be started if the positional accuracy of the above is within the range of ± b / 2.

The beam reshaped by the second aperture mask 4 is imaged on the mask 8 by the pair of shaping lenses 6 and 7. In FIG. 2C, reference numeral 8a is a variable beam exposure opening corresponding to the opening 4a of the second aperture mask 4 and is used when exposing a non-repeating pattern. Reference numeral 8c is a pattern filling opening for a pattern having a large area and requiring less accuracy, and is used when exposing a pattern having a relatively large area such as a dicing line.

In FIG. 2 (c), 14 areas 8b shown by dotted lines are stencil mask formable areas used during reduction exposure, such as contact holes.
In order to expose a pattern having a small filling factor (the ratio of the beam passing area to the incident beam area), an exposure aperture is provided in almost the entire area of the maximum area indicated by the dotted line. On the other hand, like a fine circuit pattern
To expose a pattern with a large filling factor,
An aperture corresponding to a fine pattern is provided in a relatively small area in the center of the area having the maximum area shown by a dotted line.

The area of the mask formable region 8b in which the fine pattern is provided is set to be approximately equal to the maximum area of the variable beam when the filling factor is 70% or more, and is variable when the filling factor is 10% or less. It is preferably set to about twice the maximum area of the beam. Therefore, naturally, when the filling factor is 70% or more, a reduction exposure beam having an area substantially equal to the maximum area of the variable beam is made incident on the corresponding aperture of the mask 8, and when the filling factor is 10% or less. A reduction exposure beam having an area about twice the maximum area of the variable beam is made incident on the corresponding aperture of the mask 8. By doing so, the space charge effect of the beam can always be made substantially constant irrespective of the density of the beam at the time of reduction exposure, and whether the reduction exposure or the variable beam exposure is performed.

The size of the opening 4b of the second aperture mask 4 is determined as follows. That is, when the dimension of the region 8b on the mask 8 where the stencil mask is provided is A and the interval between these regions is B, the mask 8 of the opening 4b is formed.
The size of the opening 4b is determined so that the size of the image 4b 'above is A + B. Therefore, as described above, as long as the position of the image on the mask 8 is within the range of ± B / 2, even if the shaping lens pair 6 and 7 has a current fluctuation,
There is no problem even if the applied voltage to the deflectors 5a and 5b is not sufficiently settled.

Here, the mask 8 is located at a position optically conjugate with the second aperture mask 4, and the deflectors 5a and 5b.
When any one of the apertures of the second aperture mask 4 is selected by controlling the voltage applied to the first aperture mask 4, any one of the stensis masks is automatically selected based on the imaging relationship between the two aperture masks.
Incidentally. Reference numeral 9 denotes a variable beam deflector provided at the crossover image position, which can independently change the beam dimensions in the x and y directions.

The pair of shaping lenses 6 and 7 is a crossover image 10.
Are provided in point symmetry with respect to each other, and the exciting currents are applied with equal values so that the directions of the magnetic fields are opposite to each other. Under such conditions, distortion between the surface of the aperture 4 and the surface of the mask 8 is suppressed to a minimum, and there is no problem even if 4 × 4 or 5 × 5 stencil masks are provided.

The exposure beam finally shaped by the mask 8 is reduced to about 1/40 by the reduction lens 11 and the objective lens 12, and is incident on a predetermined exposure region on the substrate 13 by the deflector 14. Further, 15a and 15b are electrostatic deflectors, which perform a blanking operation for turning the beam on and off at high speed. The beam is deflected using the mask 8 as a deflection fulcrum so that the beam image does not move on the substrate 13 during the blanking transition. At the time of exposure, the sub deflector 16 deflects the beam at a high speed to draw a pattern in a predetermined exposure area on the wafer 13. As shown in FIG. 3, the printing pattern 61 formed by the reduction exposure beam is formed on the wafer 13 at a predetermined distance from the drawing region 62 formed by the variable beam exposure beam.

The embodiment constructed as described above has the following effects. The area of the reduction exposure beam emitted from the reduction exposure aperture area 8b of the mask 8 is limited to 1.5 to 2.0 times the maximum area of the variable beam exposure beam emitted from the variable beam exposure aperture area 8a. Therefore, the blur due to the space charge effect of the exposure beam image at the time of reduction exposure can be made almost the same as that of the exposure beam image at the time of variable beam exposure, and the pattern formation with high accuracy becomes possible. As a result, there is less variation in the in-focus state during variable beam exposure and reduced exposure, and there is no need to adjust the focus each time switching between reduced exposure and variable beam exposure is performed. Position correction calculation is not necessary because of no occurrence of, and thus throughput is improved.

Further, since the area of the variable beam exposure opening 4a on the second aperture mask 4 is set to 1/4 of the reduction exposure opening 4b, the beam is formed between the second aperture mask 4 and the mask 8. The space charge effect during traveling can be reduced, the beam blur during variable beam exposure can be reduced, and highly accurate pattern formation can be performed.

Further, since the masking 8 is provided with the filling opening 8c and the area thereof is set to about four times the maximum area of the variable beam that can be used during the variable beam exposure, the accuracy can be improved in a large area such as a dicing line or a bonding pad. Unnecessary patterns can be formed in a shorter time than before, and throughput is improved.

[0025]

As described above in detail, according to the present invention, the size of the exposure beam emitted from the first aperture during the reduction exposure is about 1.5 as compared with the size of the exposure beam during the variable beam exposure. Since it is limited to about 2.0 times, the space charge effect of the beam is almost the same during variable beam exposure and reduction exposure, and there is no need to adjust the focus each time the beam is changed. No correction calculation is required, and the throughput is improved. In addition, claim 2
According to the method, a pattern having a large area and requiring less accuracy is exposed by using a third aperture having an area which is four times or more the area of the variable beam exposure beam emitted from the second aperture. Therefore, the throughput is improved.

[Brief description of drawings]

FIG. 1 is a diagram showing a schematic configuration of an example of a pattern forming apparatus according to the present invention.

FIG. 2 is a diagram illustrating openings of first and second aperture masks 2 and 4 and a mask 8;

FIG. 3 is a diagram showing a variable beam exposure region and a reduction exposure region on a substrate.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Electron gun 2 1st aperture mask 4 2nd aperture mask 4a Variable beam exposure aperture 4b Reduction exposure aperture 5a, 5b Aperture selection deflector 8 Mask 8a Variable beam exposure aperture 8b Reduction exposure aperture formation region 8c Filling Opening

Claims (2)

[Claims] 1. A beam generating means for generating an exposure beam, a beam shaping means for shaping a beam generated by the beam generating means, a first aperture for reduction exposure and a second aperture for variable beam exposure. And a beam generated by the beam generating means and shaped by the beam shaping means, the first aperture and the second
And a deflection means for deflecting the variable beam so as to be incident on one of the two apertures, the area of the reduction exposure beam emitted from the first aperture is emitted from the second aperture. The pattern forming apparatus is characterized in that the maximum area of the variable beam exposure beam is limited to 1.5 to 2.0 times. 2. The pattern forming apparatus according to claim 1, wherein a third aperture for filling having an area which is four times or more of a maximum area of the beam for variable beam exposure is provided in the mask, and the deflecting means is used at the time of filling exposure. The variable beam is incident on the third aperture by means of, and the exposure beam is imaged on the substrate via the third aperture.