JPH11260714A - Position detection mark and detection method of mark position - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a position detection mark which can detect X- and Y- directional positions of an identical point with a high S/N ratio and with a small detection error. SOLUTION: The position detection mark is made up of groups of mark elements 1 to 40 which can detect positions of two directions (X- and Y- directions) substantially perpendicular to each other. These mark element groups are densely accommodated within a small area on a substrate. The mark element groups arranged in the X- and Y-directions are accommodated densely within the small area and a gravity of the X-directional mark element groups is not away from that of the Y-directional mark element groups, so that, even when an optical system has a nonlinear distortion therein, an abnormal error does not occur at the time of registration.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention
The present invention relates to a position detection mark and a mark position detection method suitable for registration and alignment when a fine high-density pattern of m or less is formed by transfer. in particular,
The present invention relates to a position detection mark and a mark position detection method capable of detecting a position in both X and Y directions at the same point with a high S / N ratio and having few erroneous detections.

[0002]

2. Description of the Related Art A cross mark or L is used as a position detection mark for registration at the time of exposure of a semiconductor device or the like.
Letter marks are known. Also, a mark in which a number of band-shaped mark elements are arranged in the X direction and the Y direction is known (USP).
5, 523, 576, specifically described later with reference to FIG. 5). Further, in the field of light exposure, concentric square marks are known (Japanese Patent Application Laid-Open No. 52-154369).

[0003]

Among the above-mentioned prior arts, the cross mark and the L-shaped mark substantially generate a signal because of a single linear small area. There is a problem that the S / N ratio is small in performing registration with a beam having a low density.

On the other hand, the marks of US Pat. No. 5,523,576 are shown in a plan view in FIG. 5, where the mark element groups 51 to 59 for the X direction and the mark element groups 60 to 67 for the Y direction are adjacent to each other. It is provided in. The center of gravity 68 of the mark element group for position detection in the X direction (nine bands 51 to 59), the center of gravity 69 of the mark element group for position detection in the Y direction (eight bands 60 to 67), and the center of gravity of the entire mark 70 are different from each other. Therefore, the evaluation point of the mark position in the X direction is slightly different from the evaluation point of the mark position in the Y direction, so that if nonlinear distortion occurs in the optical system, subsequent analysis becomes difficult. In addition, there is a problem in that a signal when the mark and the beam are shifted by one pitch is erroneously detected. Further, in the case of a concentric square mark, there is a problem that it is impossible to form the detection beam in such a shape in the case of a perforated reticle.

The present invention has been made in view of such problems, and is suitable for registration and alignment when a fine high-density pattern having a minimum line width of 0.1 μm or less is formed by transfer. An object of the present invention is to provide a position detection mark and a mark position detection method capable of detecting positions in both the X and Y directions with a high S / N ratio and having few erroneous detections.

[0006]

In order to solve the above-mentioned problems, a position detection mark of the present invention is a mark for receiving irradiation of a charged particle beam and detecting a relative positional relationship with the beam; A mark element group capable of measuring positions in two directions (X direction and Y direction) substantially orthogonal to each other, wherein the mark element group is closely housed in a limited small area on the base. And

Further, the mark position detecting method of the present invention comprises:
A method of irradiating a position detection mark with a beam and detecting a relative positional relationship between the beam and the mark; a mark element group capable of measuring positions in two directions (X direction and Y direction) substantially orthogonal to each other The position detection mark is formed by closely storing the position detection mark in a limited small area on the base, and the position detection mark and the detection beam are relatively scanned.

When the X- and Y-direction mark element groups are densely housed in a small area, and the center of gravity of the X-direction mark element group and the Y-direction mark element group do not separate so much, a nonlinear distortion is caused in the optical system. Also, no abnormal error occurs during registration. Also, the visual field distortion of the optical system can be correctly evaluated.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention is particularly effective when the above-mentioned beam is a charged particle beam such as an electron beam used for pattern transfer exposure. This is because it is desirable to make the area where the beam for mark detection exposes the resist as small as possible.

Hereinafter, description will be made with reference to the drawings. First,
An outline of an example of a transfer exposure apparatus using the position detection mark and the mark position detection method of the present invention will be described. FIG. 6 is a diagram showing an image forming relationship in the entire optical system of the electron beam exposure apparatus. The electron gun 101 emits an electron beam downward. Below the electron gun 101, two-stage condenser lenses 103 and 105 are provided.
The electron beam passes through these condenser lenses 103, 10
5 through a blanking aperture 107 to image a crossover.

Below the condenser lens 105, a rectangular opening 106 is provided. The rectangular aperture (sub-field limiting aperture) 106 allows only the electron beam illumination light for an area corresponding to one exposure unit area (sub-field) to pass. Specifically, the opening 106 forms the illumination light into a square having a dimension of slightly more than 1 mm square in reticle size conversion. The image of the opening 106 is formed on the reticle 110 by the lens 109.

Below the opening 106, the above-described blanking opening 107 is provided at a position where a crossover is formed. The sub-field-of-view selection deflector 108 is disposed below the sub-field selection deflector 108. This sub-field selection deflector sequentially scans the illumination light mainly in the X direction (lateral direction) in FIG. 6 to illuminate all the sub-fields in the optical field including deflection on the reticle.
A condenser lens 109 is arranged below the sub-field selection deflector 108. The condenser lens 109 is
The electron beam is converted into a parallel beam and hits the reticle 110,
The aperture 106 is imaged on the reticle 110.

The reticle 110 is shown in FIG.
Although only the exposure unit area (sub-field) is shown, it actually extends in the direction perpendicular to the optical axis (X-Y direction) and has many sub-fields. When illuminating and exposing each sub-field in the field of view of the optical system in the X direction, as described above, the sub-field selection deflector 1
At 08, the electron beam is deflected.

The reticle 110 is mounted on a reticle stage 111 movable in the X and Y directions. The wafer 114, which is a material to be exposed, is also placed on a wafer stage 115 that can move in the X and Y directions. By scanning these reticle stage 111 and wafer stage 115 in the Y direction opposite to each other, exposure is sequentially performed also in the Y direction. Further, by scanning both stages 111 and 115 intermittently in the X direction, a wider area can be exposed. Note that both stages 111, 1
15 is equipped with an accurate position measurement system using a laser interferometer, and the respective sub-field images are accurately joined on the wafer 114 by adjusting a separate alignment means and each deflector.

A projection lens 11 is provided below the reticle 110.
2 and 113 (objective lens) and a deflector 131 are provided. Then, one sub-field of the reticle 110 is irradiated with an electron beam, and the electron beam patterned by the reticle 110 is reduced and deflected by the projection lenses 112 and 113 to form an image at a predetermined position on the wafer 114. . An appropriate resist is applied on the wafer 114, and a dose of an electron beam is given to the resist, so that a reduced pattern of a reticle image is transferred onto the wafer 114. The wafer 114 is mounted on the wafer stage 115 movable in the direction perpendicular to the optical axis as described above.

Reference numeral 133 above the wafer 114 is an electron beam detector. The electron beam detector 133 is connected to the wafer 11
Detects the electron beam or secondary electron reflected from 4,
Mark (not shown) arranged on wafer 114
Get location information for. The scanning of the mark with the electron beam is performed by using the exposure deflection deflector 131 in or near the projection lens shown in FIG. 6 or by using the mark scanning deflector (reference numeral 131 'in FIG. 6, in this example, electrostatic deflection). Equipment).

Next, the position detection mark will be described.
FIG. 1 is a plan view of a position detection mark according to one embodiment of the present invention. This mark has a whole (small area) size smaller than one sub-field of view, an outer shape of a square, and 20 bands 1 to 10 and 11 to 11 extending in the Y direction.
20 and an X-direction mark element group consisting of
A Y direction mark element group including zero bands 21 to 30 and 31 to 40 is stored. Each mark element group is located in a triangle separated by two square diagonal lines (not shown).

Regarding the mark element group consisting of the bands 1 to 10, the width of each band is constant, and the width of the space between the bands is the same at any point. On the other hand, when it comes to the length, the outermost band 1 is the longest, gradually decreases at a constant ratio toward the inside, and the innermost band 10 is the shortest. The dimensions of the band are an example.
0 μm. Obi 11-20, 21-30, 31-40
Is similar. In addition, between each band group (for example, bands 1, 2
There is a space between (1, 1, 31). This is to avoid the donut phenomenon (stencil problem) when this mark is formed on a stencil reticle. Each band may be formed in the form of a film of a heavy metal such as W or Au or an etching groove dug in a wafer.

FIG. 2 is a plan view showing the shape of a beam for irradiating the position detection mark of FIG. The beam (beamlet) of FIG. 2 except that the width of each band 1'-40 'is narrow (0.1 .mu.m in one example) and the space between the zones is wide.
Has the same shape as the mark in FIG. The reason why the width of each band is narrowed is the same reason that when detecting a mark with a point beam, performing mark detection with a narrow beam can perform high-precision mark detection. A beam position evaluation pattern (bands 1-2) of the mark of FIG. 1 and the mark of FIG.
0) The center of gravity of the group and the center of gravity of the beam position evaluation patterns (bands 21 to 40) in the Y direction are both at the center of the square and coincide with each other. Therefore, when mark detection is performed using the mark in FIG. 1 and the beam in FIG. 2, the X and Y coordinates of the position of the center of gravity are measured, and registration can be performed easily. Further, since the entire length of the mark group is sufficiently long due to the beamlet, the S / N ratio can be sufficiently increased.

At the time of scanning, the maximum signal is obtained when the mark group and the beam group are completely overlapped, and if there is a shift in the X direction by one pitch, the signals from the bands 1 and 20 disappear. Also, belt 11
19 are equivalent to the total length of the mark group being shortened by a total of 11 lengths because the dimensions of the overlapping beam elements are gradually reduced. And 2 have disappeared. Therefore, the signal amount is 80 when all match.
%, And can be sufficiently separated from the intensity of 100%, so that the position shifted by one pitch is not erroneously detected as the mark center.
On the other hand, when ten patterns of the same length are arranged, even if the pattern is shifted by one pitch, the signal amount is reduced to only 90%, so that there is a great possibility of erroneous detection.

FIG. 3 is a plan view showing an example of a mark suitable for a case where the range for searching for the mark position is wide and there is a beam scanning prohibited area 201 near the mark. The mark 200 is composed of eleven X-direction mark element groups and twelve Y-direction mark element groups. The overall shape is a rectangle that is long (length L _Y ) in the Y direction. In this case, it is assumed that the position of the mark in the X direction is completely unknown, and the position in the Y direction is roughly known, but there is an uncertainty of 100 μm. In this case, contact the beam if the length of L _Y above 50μm always mark if we scanned from sufficiently far away in the X direction to the left in the figure,
There is no risk of scanning the hatched prohibited area 201.

FIG. 4 is a plan view showing an example of a mark suitable for a case where the mark has a rotation error. This mark 30
0 is composed of 20 X-direction mark element groups and 20 Y-direction mark element groups. The overall shape is almost circular. Assuming that the diameter of the circle is 10 μm in the figure, the longest mark element (band) has a length of 7 μm. Here, assuming that the rotation error between the beam and the mark is Δθ and that the deterioration of the rise of the signal waveform due to the rotation error between the beam and the mark is allowed to be 10 nm, the following is obtained. However, the beam shape has the same pitch and length as the mark element, and only the width is about half that of the mark. .DELTA..theta..multidot.7 .mu.m.ltoreq.10 nm As a result, .DELTA..theta..ltoreq.1.43 mrad, and the mark can be detected even if there is a rotation error of 1.43 mrad using the mark of this example.

[0023]

As is clear from the above description, according to the present invention, when a fine high-density pattern having a minimum line width of 0.1 μm or less is formed by transfer, the registration, the field distortion, the beam resolution, etc. Also suitable for beam evaluation, it is possible to detect positions in both X and Y directions at the same point with a high S / N ratio, and it is possible to provide a position detection mark and mark position detection method with less erroneous detection.

[Brief description of the drawings]

FIG. 1 is a plan view of a position detection mark (square) according to one embodiment of the present invention.

FIG. 2 is a plan view showing a shape of a beam for irradiating the position detection mark of FIG.

FIG. 3 is a plan view of a position detection mark (rectangle) according to another embodiment of the present invention.

FIG. 4 is a plan view of a position detection mark (circle) according to another embodiment of the present invention.

FIG. 5 is a plan view of a position detection mark described in US Pat. No. 5,523,576.

FIG. 6 is a diagram illustrating an image forming relationship in the entire optical system of the electron beam exposure apparatus.

[Explanation of symbols]

1 to 10, 11 to 20 X direction position measurement mark element (band) 21 to 30, 31 to 40 Y direction position measurement mark element (band) 51 to 59 X direction position evaluation mark element 60 to 67 Y direction position Evaluation mark element 68 Center of gravity of X-direction position measurement mark 69 Center of gravity of Y-direction position measurement mark 70 Center of gravity of X-direction and Y-direction beam position measurement mark 201 Beam scanning prohibited area

Claims (7)

[Claims] 1. A mark for receiving a charged particle beam and detecting a relative positional relationship with the beam; measuring a position in two substantially orthogonal directions (X direction and Y direction). A position detection mark comprising a group of possible mark elements, wherein the group of mark elements is densely housed in a limited small area on a base. 2. The position detection mark according to claim 1, wherein the small region has a substantially circular outer shape. 3. The position detection mark according to claim 1, wherein an outer shape of said small area is substantially square. 4. The position detection mark according to claim 1, wherein an outer shape of said small area is substantially rectangular. 5. The position detection mark according to claim 1, wherein the center of gravity of the mark element group in the X direction substantially coincides with the center of gravity of the mark element group in the Y direction. 6. A method for irradiating a position detection mark with a beam and detecting a relative positional relationship between the beam and the mark; measuring positions in two directions (X direction and Y direction) substantially orthogonal to each other. A mark, wherein the position detection mark is formed by closely storing a group of possible mark elements in a limited small area on the base, and the position detection mark and the detection beam are relatively scanned. Position detection method. 7. A mark position detecting method according to claim 6, wherein said detection beam is constituted by a group of beam elements having a length substantially equal to a mark element of said detection mark and a narrow width.