JP2001135562A - Lithography system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve a problem of a conventional lithography system that a plurality of masks or reticles are aligned while being replaced when a plurality of patterns are exposure recorded while being superposed on a wafer and thereby the yield decreases due to superposition accuracy of the patterns to cause lowering of throughput of exposure recording. SOLUTION: In place of a reticle or a mask written over a plurality of sheets, one or a plurality of reflection spatial optical modulation elements indicating a brightness pattern equivalent to the pattern written on each reticle or mask is arranged. Selective reflection surface of the spatial optical modulation element is irradiated with light from the light source of a lithography system and the numerical aperture of irradiating light is matched with that of a projection lens for the reflection spatial optical modulation element. Furthermore, variation with time of the brightness pattern indicated by the reflection spatial optical modulation element is synchronized with the movement of a silicon wafer with regard to the conjugate ratio of the pattern on the silicon wafer and the projection lens.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a lithographic apparatus for projecting an optical pattern to form a fine pattern on a semiconductor wafer. The present invention relates to an apparatus applied to micron bulk micromachining.

[0002]

2. Description of the Related Art The ratio between a pattern projected on a silicon wafer and a pattern exposed and recorded on the silicon wafer is 1: 1:
A lithography apparatus used in bulk micromachining of 1 to 5: 1 includes, for example, monthly Semico.
nductor World Vol. 14 No. 2 (Press Journal, issued on January 20, 1995) p. 136 "Fig. 2 Proximity exposure method", Optics, Vol. 21, No. 10 (Japan Society of Applied Physics, Japan Optical Society, published October 10, 1994)
There is an apparatus described in p.610 “Exposure of a double mirror system with the same magnification by scanning an arc slit in FIG. 1”.

[0003] In any of these, a reticle or mask on which a pattern to be projected on a silicon wafer prepared by another apparatus is drawn is placed directly above the silicon wafer, or a projection lens is placed at a position conjugate with the silicon wafer. The reticle or mask pattern is projected onto the silicon wafer while moving both according to the conjugate ratio.

[0004]

However, when a complicated pattern is exposed and recorded on a silicon wafer by using a lithography apparatus according to the prior art, it is necessary to sequentially project while exchanging a reticle or mask which has been divided into a plurality of sheets and drawn. was there.

[0005] The number of reticles or masks can exceed ten and a few, and in order to accurately superimpose these patterns exposed and recorded on a silicon wafer, all the reticles or masks and the silicon wafer must be combined. The relative positioning accuracy had to be maintained at submicron.

For this reason, it is difficult to increase the exposure recording throughput.
There is a problem that it is difficult to increase the yield of the finished product of the exposure-recorded silicon wafer.

An object of the present invention is to provide a lithographic apparatus capable of increasing the throughput of exposure recording and increasing the yield of completed silicon wafers on which exposure recording has been performed.

[0008]

SUMMARY OF THE INVENTION The above problem arises when a complex pattern is exposed and recorded on a silicon wafer by using a reticle which is drawn on a plurality of sheets or by sequentially projecting while replacing a mask. It is obvious to do.

Therefore, in the present invention, instead of the reticle or the mask drawn separately on the plurality of sheets, one or more reflective spatial light modulators for displaying a light and dark pattern equivalent to the pattern drawn on each reticle or mask are provided. It was configured to arrange a plurality.

In addition, light from the same light source as that provided in the conventional lithographic apparatus is irradiated by an illumination lens onto the surface of the reflective spatial light modulator which selectively reflects light, and
The numerical aperture of the irradiation light was made substantially the same as the numerical aperture of the projection lens with respect to the reflective spatial light modulator.

Further, the temporal change of the light-dark pattern displayed by the reflection type spatial light modulator is synchronized with the movement of the silicon wafer with respect to the conjugate ratio between the pattern on the silicon wafer and the projection lens.

[0012]

FIG. 1 shows an embodiment of the present invention, and shows the main elements constituting a system to which the present invention is applied, their positional relationship and signal transmission relationship.

The silicon wafer 13 is fixed on a stage 14 so that its normal line is parallel to the optical axis of the projection lens 12. The stage 14 has a function of finely adjusting and fixing the optical axis (not shown) of the projection lens 12 so as to pass through the center of the silicon wafer 13. A function of moving the distribution pattern of light modulated by the reflective spatial light modulator 1 in a direction (arrow 601) at a constant speed, and a function of distributing the light modulated by the reflective spatial light modulator 1 Has a function of step-moving by a fixed distance in a direction (arrow 602) perpendicular to the direction in which. In this movement, the motors 21 and 24 are connected to the motor control device 22.
And 23 are controlled by the control computer 7.

The projection lens 12 is provided above the silicon wafer 13, and the reflective spatial light modulator 1 is provided further above the projection lens 12. At this time, the projection lens 12
Is determined by the ratio of the size of the distribution pattern of the light modulated by the reflective spatial light modulator 1 to the size of the pattern projected on the silicon wafer 13. For example, if the ratio is 1: 1, the opening of the projection lens 12 is positioned between the reflective spatial light modulator 1 and the silicon wafer 13. If the ratio is 5: 1, the opening of the projection lens 12 is positioned so as to internally divide the reflective spatial light modulator 1 and the silicon wafer 13 into 5: 1. In the present embodiment, description will be made using a case where the ratio is 1: 1.

The reflection type spatial light modulator 1 has a function of reflecting a part or all of a light beam incident thereon in a specific direction. In this embodiment, using this function,
The pattern which modulates the light incident on the reflective spatial light modulator 1 is a pattern corresponding to a mask or a reticle of a conventional lithographic apparatus, and is used as a pattern generating element.

In order for the reflection type spatial light modulator 1 to generate such a pattern, a pattern displayed on the display 8 of the control computer 7 is used as a signal from which the pattern is generated. That is, the signal transmitted from the control computer 7 to the display 8 is branched,
This signal is supplied to a digital row address generator 16, a digital column address generator 17, and a 1-bit D / A circuit 15.
To enter. Then, based on the signals obtained from the respective components, the spatial position (row position and column position) of the portion of the reflective spatial light modulator 1 that reflects the light and whether or not this portion reflects light is determined. . This process does not need to be synchronized with the display on the display 8 of the control computer, but is performed independently based on the signal of the synchronous frequency device 152. Furthermore, the signal on the display of the display 8 of the control computer is multi-valued with respect to luminance, but the illumination intensity on the resist on the silicon wafer in the lithographic apparatus does not need to be multi-valued. Therefore, the configuration is such that the reflection type spatial light modulator 1 is modulated via the 1-bit D / A circuit 15 based on the value set by the binary setting device 151.

As such a reflective spatial light modulator 1, for example, Texas Instruments (Texas Ins.)
Struments Inc.) Digital Micromirror Device
There is a chair (Digital Micromirror Device, hereinafter abbreviated as DMD). This element is described, for example, by Larry J. Hornbeck.
Digital Light Processing for High-Brightness, High
-Resolution Applications, Electronic Imaging, EI'97
Projection DisplayIII Co-Sponsored by IS & T and SP
As shown in IE An Invited Paper 1997, Page 4 left side, 16 μm square modulation mirrors are arranged at 17 μm pitch.
The reflection angle of the mirror can be tilted from its neutral position to elevation and depression angles by 10 degrees and 15 nanoseconds. This DMD
Since the element material and the structure are simple, the size of the mirror can be reduced to 10 μm square.

The reflection type spatial light modulator 1 includes an illumination lens 2
Is located at a position conjugate with the exit aperture of the light intensity equalizing optical system 3. Its normal is 20 with respect to the optical axis of the illumination lens 2.
Fixed at an angle. This 20 degrees is twice the maximum value of 10 degrees when the installation angle of the micromirror is changed in order to create a state of whether or not the reflective spatial light modulator 1 reflects light. The numerical aperture of the light that the illumination lens 2 illuminates the reflective spatial light modulator 1 is such that the light from the reflective spatial light modulator 1
Numerical aperture at the time of incidence was adjusted.

The light intensity equalizing optical system 3 is an optical system for equalizing the spatial light emission intensity distribution of the illumination light source 4 within the range of its exit aperture. It becomes uniform over the entire modulation region of the modulation element 1 and further over the surface of the silicon wafer 13.

As the illumination light source 4, a light source having an emission wavelength intensity distribution suitable for a resist applied on the silicon wafer 13 is selected. In this embodiment, a mercury lamp is used. The illumination light source 4 is controlled by a high-voltage power supply 6 and a circuit 5 for initializing and stabilizing the light emission. The timing of light emission is controlled by the control computer 7 in synchronization with the stationary or constant-speed movement of the silicon wafer 13.

The transmission of the control information of each element described above is as follows.
It is as follows.

A pattern to be exposed and recorded on the silicon wafer 13 is designed, a two-dimensional image of the pattern is captured as computer data, and then displayed on the display 8 of the control computer 7. This display data signal is sent to the digital row address generator 16 and the digital column address generator 17 and the 1-bit D / A circuit 15 at the same time, and the modulation spatial position (row and column position) of the reflection type spatial light modulator 1 is respectively obtained.
And the modulation signal are calculated and sent to the reflection type spatial light modulation device 1.

The reflection type spatial light modulator 1 transmits a part or all of the light from the mercury lamp through the projection lens 12 in the modulation area in accordance with the distribution of the mask portion or the unmask portion indicated by the data. The individual elements are modulated to irradiate the silicon wafer. Light that does not irradiate the silicon wafer enters the beam stopper 512 and attenuates its intensity. At this time, the adjustment of the exposure time due to the difference in the resist does not directly turn on or off the illumination light source 4 but adjusts the modulation of the reflective spatial light modulator 1. As a result, it is possible to eliminate the fluctuation of the light source light amount generated at the time of turning on or off. Further, since the adjustment time is as short as 15 nanoseconds, the throughput for exposure can be increased.

According to the above embodiment, the silicon wafer 1
Since the pattern to be exposed and recorded on the mask 3 is not printed on the mask in advance and is not replaced one after another, the alignment between the silicon wafer 13 and the mask required for each replacement is not required. As a result, a pattern printing error due to alignment does not occur, so that the yield can be increased.

Further, since the pattern to be exposed and recorded on the silicon wafer 13 can be transferred to the reflection type spatial light modulator 1 in the form of digital information, even if the number of patterns to be exposed and recorded becomes as large as several tens, the exposure and recording can be performed. High throughput can be maintained.

Further, in the correction of the proximity effect for preventing the pattern edge to be exposed and recorded on the silicon wafer 13 from being deteriorated by the influence of light diffraction, a correction pattern is generated at the time of exposure and recording for a previously designed pattern. Therefore, a high-quality pattern can be exposed and recorded while maintaining a high exposure recording throughput.

FIG. 2 shows another embodiment of the present invention, in which only parts different from FIG. 1 among the main elements constituting the system to which the present invention is applied are shown.

In FIG. 2, the projection lens 121 sets the ratio of the distribution pattern of the light modulated by the reflective spatial light modulators 101, 102 and 103 to the pattern projected on the silicon wafer 13 to 5: 1. The reflective spatial light modulators 101, 102 and 1
The modulation region No. 03 and the silicon wafer 13 were placed at a position internally dividing 5: 1.

The reflection type spatial light modulators 101, 102 and 1
Numerals 03 are arranged in a horizontal line, and the gap between adjacent elements is the same as the modulation mirror arrangement pitch in each reflection type spatial light modulation element. These reflective spatial light modulators 101, 102, and 103 are respectively illuminated by separate illumination lenses 104, 105, and 106, via illumination light equalizing optical systems 107, 108, and 109, and illumination light sources 110 and 11 respectively.
The lights of 1 and 112 are reflected by the reflective spatial light modulators 101 and 10.
The normal to the plane where 2 and 103 are located is 20
It is illuminated at an angle of degrees. Of the illumination light, light that is modulated by the reflective spatial light modulators 101, 102, and 103 but does not irradiate the silicon wafer is a beam stopper 1
13 and 114, 115 to attenuate the intensity.

The illumination light sources 110, 111 and 112 are all driven by the same circuit 5 for light emission initialization and light emission stabilization and the high voltage power supply 6. At this time, the illumination light sources 110 and 11
If there is a variation in the emission intensity between 1 and 112, the amount of exposure to the resist applied on the silicon wafer can be made uniform by adjusting the spatial modulation speed by the reflective spatial light modulators 101, 102 and 103. can do.

FIG. 3 is a schematic diagram of a light pattern modulated by the reflection type spatial light modulators 101, 102 and 103 in FIG. 2. FIG. 3 (a) changes to FIG. 3 (b) and further to FIG. Indicates a state of continuous change. The originally designed exposure recording pattern is (d), in which a mask area 130 and an unmask area 131 are drawn. In the reflection type spatial light modulators 101, 102, and 103, each of them modulates to reflect illumination light. Modulation without reflection.

3 (a) to 3 (c), the modulation content changes so as to scroll a part of (d) in the modulation area of the reflective spatial light modulators 101, 102 and 103. This scrolling can be performed by scrolling a part of the pattern shown in FIG. 3D displayed on the display 8 of the control computer 7. The stage 14 to which the silicon wafer 13 is fixed moves at a constant speed in the scroll direction opposite to the scroll direction (arrow 603) in synchronization with the scroll. The moving speed at this time is set to be the reflection type spatial light modulator
3 is a speed obtained by multiplying the scroll speed of the light pattern to be modulated by the reduction ratio 5: 1 of the projection lens 121.

According to the above embodiment, the projection lens 121
Of the reflection type spatial light modulator 101 so that
Since the light distribution pattern modulated by the light emitting elements 102 and 103 is reduced and exposed on the silicon wafer 13, a pattern with higher definition than the reflective spatial light modulator can be recorded. In addition, since the light distribution pattern modulated by the plurality of reflective spatial light modulators arranged is generated, the exposure recording pattern area on the silicon wafer is not reduced, and the exposure recording throughput is kept high. Can be.

In this embodiment, by scrolling the pattern in the modulation area such as the reflection type spatial modulation element 101, the reflection type spatial modulation element 101 is formed as shown in the exposure recording pattern shown in FIG. Even if a pattern is drawn over an area larger than the modulation area such as, the stage 14 on which the silicon wafer 13 is fixed is synchronously scanned without moving the reflection-type spatial modulation element 101 and the like.
Exposure recording can be performed on the silicon wafer 13. Accordingly, in the conventional method, a plurality of masks are exchanged, and an overlay error does not occur as in the case of performing recording while moving the stage 14 stepwise, thereby increasing the yield. Further, since there is no need to exchange a plurality of masks, the throughput of exposure recording can be increased.

FIG. 4 shows another embodiment of the present invention. FIG.
FIG. 2 shows only those parts of the main elements constituting the system to which the present invention is applied, which are different from those of FIG. 1 or FIG.

In FIG. 4, the reflective spatial light modulator 20
1, 202, 203, 204, and 205 correspond to 101 in FIG.
2 and 103 are installed at the same place as in FIG. 2, but not in a horizontal line as shown in FIG. 2, but in FIG. They are arranged so as to be sequentially shifted so as to include all the required pattern regions 206 on the system mask.

In the conventional “exposure of two-mirror system of the same magnification by scanning an arc slit in FIG.
Required an optical system for selectively illuminating the light. But,
In the present embodiment to which the present invention is applied, only the portion corresponding to the pattern region 206 is selectively modulated in the modulation regions of the reflective spatial light modulators 201, 202, 203, 204, and 205. It only needs to be operated, and the cost of the lithographic apparatus can be reduced without requiring any special illumination optics.

Further, the size of the above-mentioned pattern area 206 depends on the degree of the resolving power of the exposure recording, and the size of the conventional pattern area shown in FIG.
This is different for each optical system of "exposure of two-mirror system using an arc slit scan". Conventionally, it was necessary to selectively change the size depending on the accuracy of a pattern to be exposed and recorded. However, in the embodiment of the present invention, since the size of the pattern area 206 can be changed even during exposure recording, more stable exposure can be performed with respect to the resolution of the recording pattern.

It should be noted that the second and third embodiments are not limited to the reduction ratio of the projection lens 121 being 5: 1, but can be implemented even when the reduction ratio is 1: 1. At this time, even for exposure recording of a large area such as a liquid crystal panel, a high yield and a high throughput, which are the rectum of the present invention, can be realized.

[0040]

As described above, the means and operation according to the present invention eliminates the problem of the prior art that the reticle or mask drawn in a plurality of sheets is sequentially projected while replacing the reticle or mask. It is possible to increase the yield of finished products of the wafers on which exposure recording has been performed.

In addition, even if a large number of patterns are required to create a complicated pattern, the pattern can be created only by directly transferring data for creating the pattern to the reflective spatial light modulator. Costs can be kept low.

[Brief description of the drawings]

FIG. 1 is a perspective view showing a first embodiment of the present invention.

FIG. 2 is a perspective view showing a second embodiment of the present invention,
FIG. 3 is a diagram illustrating a positional relationship and operation of a reflective spatial light modulator, an illumination optical system, a silicon wafer, and a stage.

FIG. 3 is a diagram illustrating a change in a modulation pattern by a reflective spatial light modulator in FIG. 2;

FIG. 4 is a perspective view showing a third embodiment of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Reflection type spatial modulation element, 2 ... Illumination lens, 3 ... Light intensity equalizing optical system, 4 ... Illumination light source, 5 ... Emission initialization and emission stabilization circuit, 6 ... High voltage power supply, 7 ... Control Computer, 8 display, 9 keyboard, 10 mouse, 12 projection lens (1: 1), 13 silicon wafer, 14 stage, 15 1-bit D / A circuit, 16
... Digital row address generator, 17 ... Digital column address generator, 21 ... Motor, 22 ... Motor, 23 ... Driver, 24 ... Driver.

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) H01L 21/30 515F (72) Inventor Akira Koide 502 Kandate-cho, Tsuchiura-shi, Ibaraki Pref. In the laboratory (72) Inventor Akiomi Kono 502 Kandachi-cho, Tsuchiura-shi, Ibaraki F-term in the Machine Research Laboratory, Hitachi, Ltd.

Claims (3)

[Claims] 1. A lithographic apparatus comprising: a reflection type spatial light modulator as a device for generating a pattern to be projected on a silicon wafer at a position conjugate to a wafer with respect to a projection lens. 2. The lithographic apparatus according to claim 1, wherein one or a plurality of said reflective spatial light modulators are arranged. 3. The lithographic apparatus according to claim 1, wherein a temporal change of a pattern displayed by the reflective spatial light modulator is caused by a movement of the silicon wafer with respect to a conjugate ratio between the pattern on the silicon wafer and the projection lens. A lithographic apparatus characterized in that: