JP3673625B2 - Method for forming fine pattern - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for forming a fine pattern on a sample by using a scanner typified by an electron beam drawing apparatus and a light reduction projection exposure apparatus typified by a stepper in combination.
[0002]
[Prior art]
In recent years, demands for higher density and higher integration of semiconductor integrated circuits are increasing. In particular, when aiming for a high degree of integration with a line width of 0.15 μm or less, conventional exposure apparatuses that use light (including X-rays) cannot be used, and drawing or exposure is performed with a scanner that draws using an electron beam or ion beam. It will be. However, such a scanner has a problem that the throughput is extremely low as compared with the optical exposure apparatus. Therefore, a method called mix-and-match (or hybrid lithography) has been proposed in which a light exposure apparatus is used for exposure of layers that allow a relatively low resolution, and only a layer that requires high resolution or high accuracy is exposed by a scanner. (Japanese Patent No. 2625124, Japanese Patent Laid-Open Nos. 62-58621, 62-149127, etc.).
[0003]
[Problems to be solved by the invention]
An object of the present invention is to improve the overlay accuracy in such a mix-and-match method without impairing the throughput performance.
[0004]
[Means for Solving the Problems]
In the present invention for achieving the above object, the carried a first device for drawing or exposure of the first region on the sample, the exposure of the second region which is a set of a plurality of said first region a method of forming a pattern on a sample by using a second device, the position information of the sample in a direction perpendicular to the sample surface at the measurement point of the first of each of the first area obtained by the device the basis, the steps of each draw or exposing the plurality of first regions using said first device, a plurality of position information in a direction perpendicular to the sample surface obtained in the first device , the position information of the sample in a direction perpendicular to the sample surface obtained by the second device in a small number of measurement points from the measurement point of the position information, the line alignment of the second area based on There Do, be exposed to the second area using the second device Characterized by a step.
[0005]
Here, the first apparatus is, for example, an electron beam drawing apparatus, and the second apparatus is, for example, a reduced projection exposure apparatus (stepper). Further, the alignment is intended to include the alignment of the tilt direction with respect to the mean pattern forming surface alignment perpendicular direction of the sample, the pattern forming surface as required.
[0006]
[Action]
The maximum drawing range (maximum deflection range) of the electron beam drawing apparatus is, for example, 5 mm □. On the other hand, the maximum exposure range of the reduction projection exposure apparatus is, for example, 20 mm □, and the scanning reduction projection exposure apparatus is, for example, 25 mm × 35 mm.
As an example, an electron beam lithography apparatus and a reduction projection exposure apparatus are used together, and an overlayer is formed on the pattern formed by matching each shot (exposure area) with the maximum exposure range of the reduction projection exposure apparatus. At the time of printing, the electron beam drawing apparatus divides the exposure range of 20 mm □ into small areas of 5 mm □ or less, for example, 4 mm □, and draws (exposures) while focusing (AF) for each small area. That is, the 1-chip and 20 mm □, an electron beam drawing apparatus if measures focus (AF), one point at a small region of 4 mm □, 1 information per chip 25 is obtained. On the other hand, the measurement point of the focus (AF) in the reduced projection exposure apparatus or a scanning reduction projection exposure apparatus is typically 2-5 points. Increasing the number of measurement points increases accuracy but decreases throughput. Conventionally, even if the drawing of the electron beam drawing apparatus is matched with the pattern formed by the reduction projection exposure apparatus, information is transmitted from the electron beam drawing apparatus to the reduction projection exposure apparatus, which is effective for the latter operation. I did not use it.
[0007]
When the present invention is applied to a mix-and-match of an electron beam drawing apparatus and a reduction projection exposure apparatus, a reduction projection exposure apparatus that executes subsequent processing on surface position (AF) information of an exposed surface detected during electron beam drawing. Effective use in etc. Thus, for example, even when exposure is performed by performing position (AF ) alignment with information on a small number of measurement points of 2 to 5 points per chip, the information on the small number of points obtained by the electron beam drawing apparatus is added to the information on the small number of measurement points. By adding information, more accurate misalignment detection and alignment can be performed without adversely affecting the throughput.
[0008]
【Example】
Embodiments of the present invention will be described below with reference to the drawings.
FIG. 1 shows a configuration of a reduction projection exposure apparatus (stepper) according to an embodiment of the present invention. In the figure, 6 is a reticle having a circuit pattern, 10 is an illumination beam for illuminating the reticle 6, and 7 is for positioning the reticle 6 placed by a conveying means (not shown) at a predetermined position below the illumination beam 10. A reticle stage, 8 is a reticle base that supports the reticle stage 7, 4 is a wafer for manufacturing a semiconductor device, 5 is a projection optical system that projects an image of the reticle 6 in the illumination area 9 by the illumination light beam 10 onto the wafer 4, and 1 A wafer base installed on a floor or the like, 2 is a wafer stage on which the wafer 4 is mounted and moves in a direction (XY direction) perpendicular to the optical axis of the projection optical system 5, and 3 is the optical axis direction of the projection optical system 5. It is a focus leveling stage that is driven around (Z direction), around the X axis (ωX) and around the Y axis (ωY).
[0009]
The light source 11, the incident optical system 12, the light receiving optical system 13, the photoelectric conversion element 14, the pattern plate 15, and the mirrors 16 and 17 cause a deviation between the imaging surface of the projection optical system 5 and the local exposure area surface of the wafer 4. A focus tilt sensor for measuring (AF measurement) is configured. The light flux from the light source 11 is separated into five light fluxes by the pattern plate 15, and through the incident optical system 12 and the mirror 16, as shown in FIG. 2, at the four corners and the center of the exposure area 18 on the wafer 4. 5 points are irradiated. The reflected light at these five points is incident on the photoelectric conversion element 14 via the mirror 17 and the light receiving optical system 13, and the positions of the five points in the Z direction are determined by the imaging positions of the five points on the photoelectric conversion element 14. Detected.
[0010]
FIG. 3 shows a schematic configuration of an electron beam exposure apparatus (hereinafter referred to as an EB apparatus) according to an embodiment of the present invention. In the figure, reference numeral 110 denotes an electron gun, and an electron beam emitted from the electron gun 110 is irradiated onto a wafer 104 via various electromagnetic lenses 105 and a deflecting plate 106 for blanking and scanning. The wafer 104 is placed on the wafer stage 102. The wafer stage 102 is driven on the wafer base 101 in the X direction (left and right direction on the paper surface) and the Y direction (front and back direction on the paper surface) by a drive unit (not shown), and the coordinate position is sequentially and precisely measured by a laser interferometer (not shown). The Reference numeral 103 denotes a focus leveling stage that drives the wafer in the Z direction (up and down direction on the paper), around the X axis (ωX), and around the Y axis (ωY).
[0011]
The maximum deflection range (exposure area) of the EB apparatus of FIG. 3 is much smaller than the exposure area 18 (FIG. 2) by the stepper of FIG. Therefore, in the EB apparatus of FIG. 3, as shown in FIG. 4, the exposure area 18 is divided into 6 parts vertically and horizontally to set 36 sub-areas (EB exposure areas) 118, and each sub-area is one. The exposure is performed by scanning with an electron beam one by one. At that time, alignment in the XY and Z directions is performed for each sub-area. FIG. 5 is an explanatory diagram showing a state of position measurement in the Z direction, that is, focus (AF) measurement. In the figure, 120 indicates the exposure order of the sub-area 118.
[0012]
In FIG. 3, a light source 111, an incident optical system 112, a light receiving optical system 113, a photoelectric conversion element 114, a pattern plate 115, and mirrors 116 and 117 measure the position of the electron beam irradiation position on the wafer 104 in the Z direction (AF measurement). ) Is a focus sensor. The light beam from the light source 111 is irradiated to the center of the EB exposure area 118 on the wafer 104 as shown in FIG. The reflected light from the center of the EB exposure area 118 is incident on the photoelectric conversion element 114 via the mirror 117 and the light receiving optical system 113, and the imaging position of the light spot at the center of the EB exposure area 118 in the photoelectric conversion element 114. Thus, the position (AF) in the Z direction of the center of the EB exposure area 118 is detected.
[0013]
The position (AA) in the XY direction of the EB exposure area 118 is determined by detecting a common alignment mark 119 (FIG. 4) used in the stepper of FIG. The position is detected, and the position of each EB exposure area 118 in the exposure area 18 is obtained by adding the distortion information of the exposure area 18 obtained in advance by a known method (for example, see Japanese Patent Application Laid-Open No. 62-58621). Further, based on the position (AA) information and the measurement value of the laser interferometer that measures the position of the wafer stage 102, the wafer stage 102 is driven to position each EB exposure area 118 with respect to the deflection center of the electron beam. Match.
[0014]
The position (AA) in the XY direction of the EB exposure area 118 is detected by detecting the shape of the actual element pattern in the EB exposure area 118 by the secondary electron detector, and this pattern is a predetermined target pattern (template) and pattern. It can also be detected by matching. In this case, as the target pattern, it is preferable to select an actual element pattern of a portion that requires the strictest alignment accuracy in the EB exposure area 118.
[0015]
Next, the operation of the stepper of FIG. 1 will be described with reference to FIG. This stepper is assumed to be connected to the EB apparatus of FIG. 3 online or in-line. When the wafer 4 on which the pattern is formed using the EB apparatus of FIG. 3 is loaded onto the wafer stage 12 of the stepper of FIG. 1, the focus of the five points in the exposure area 18 shown in FIG. Measure. From this focus measurement value, an approximate plane including the focus (Z) and tilt (ωX, ωY) of the wafer 4 is calculated. Here, regarding the current exposure area, information previously measured or calculated by the EB apparatus is received. Then, a correction value for the approximate plane is calculated from information of the EB apparatus, the focus leveling stage 3 is driven so that the correction plane coincides with the image plane of the projection optical system 5, and then exposure is performed. Subsequently, it is determined whether or not the exposed area is the final exposure area, and if it is not the final exposure area, the operations from the focus measurement to the exposure and final exposure area determination are repeated for the next exposure area. On the other hand, if it is the final exposure area, the wafer 4 is unloaded.
[0016]
In the above-described embodiment, the stepper of FIG. 1 and the EB apparatus of FIG. 3 are connected on-line or in-line. However, the present invention can be applied even when off-line. In this case, alignment information in an apparatus that exposes a relatively small area may be previously loaded into an apparatus that exposes a relatively large area using a magnetic medium, an optical disk, or the like.
[0017]
【The invention's effect】
According to the present invention, a relatively small first region focus on a relatively large number of measurement points is detected at the time of exposure or drawing at (grid) (AF) information as electron beam drawing apparatus, then reduced When a relatively small number of measurement points are measured, aligned (AF ), and exposed in a relatively large second area (grid) as in a projection exposure apparatus, it is not detected in the second area by using it effectively. Positioning can be performed in consideration of point information, and positioning accuracy, that is, focusing (AF) accuracy can be improved. Further, in the apparatus for exposing the second area, it is not necessary to increase the alignment measurement points, and the throughput is extremely reduced.
[Brief description of the drawings]
FIG. 1 is a diagram showing a configuration of a reduction projection exposure apparatus according to an embodiment of the present invention.
FIG. 2 is an explanatory view showing a state of focus detection in the apparatus of FIG. 1;
FIG. 3 is a diagram showing a configuration of an electron beam drawing apparatus according to an embodiment of the present invention.
4 is an explanatory view showing the state of an exposure area by the apparatus of FIG. 3. FIG.
FIG. 5 is an explanatory diagram showing a state of focus detection in the apparatus of FIG. 3;
6 is a flowchart for explaining the operation of the apparatus shown in FIG.
[Explanation of symbols]
1: wafer base, 2: wafer stage, 3: focus leveling stage, 4: wafer, 5: projection optical system, 6: reticle, 7: reticle stage, 8: reticle base, 9: illumination area, 10: illumination light beam, 11: light source, 12: incident optical system, 13: light receiving optical system, 14: photoelectric conversion element, 15: pattern plate, 16, 17: mirror, 18: exposure area, 101: wafer base, 102: wafer stage, 103: Focus leveling stage, 104: wafer, 105: electromagnetic lens, 106: deflection plate, 110: electron gun, 111: light source, 112: incident optical system, 113: light receiving optical system, 114: photoelectric conversion element, 115: pattern plate, 116, 117: mirror, 118: EB exposure area, 119: alignment mark.

Claims (5)

A first device for drawing or exposure of the first region on the sample, Pa on a sample with a plurality of second performing exposure of the second region which is a set of the first region of the device In the method of forming a turn,
The plurality of first regions using the first device based on positional information of the sample in a direction perpendicular to the sample surface at measurement points in the first region obtained by the first device. Each drawing or exposing,
Perpendicular to the plurality of locations information direction perpendicular to the sample surface obtained in the first apparatus, the surface of the sample obtained by the second device in a small number of measurement points from the measurement point of the position information and exposing the position information of the direction of the sample, the alignment of the second region row stomach, the second area using the second device based on
The pattern formation method characterized by having .   The forming method according to claim 1, wherein the first apparatus is an electron beam drawing apparatus, and the second apparatus is a reduction projection exposure apparatus. Obtained the first position information in a direction perpendicular to the sample surface at the measurement points of each of said first region resulting in device detects the pattern of the actual device unit in one chip by a pattern matching method The forming method according to claim 1 or 2 , wherein 4. The formation according to claim 3, wherein the template pattern to be a target of the pattern matching is selected from patterns requiring the strictest alignment accuracy in the first region for each of the first regions. Method. A pattern of said pattern is a semiconductor device, and the first region is a smaller area than the one chip of the actual elements of the semiconductor device, wherein the second region includes one or more chips of the actual device forming method according to any one of claims 1-4 which is a region size.

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