JP5035962B2 - Processing method of diffractive optical element mold - Google Patents

Description

  The present invention relates to a processing method for processing a diffraction pattern of a diffractive optical element in a diffractive optical element molding die, and can increase the accuracy of the relative positional relationship between the alignment mark and the processed diffraction pattern. In addition, the processing effort can be reduced.

As a method of processing a mark for detecting a position on a diffractive optical element, there is one described in Japanese Patent Laid-Open No. 2000-56114.
In the above prior art, when both the diffraction pattern and the position detection mark are processed by lithography, the alignment mark and the diffraction pattern can be processed in the same process, so that the accurate alignment is possible. However, when the diffraction pattern is formed by cutting, the alignment mark is formed by a different process from the diffraction pattern. There is a problem that the positional relationship accuracy cannot be increased.

FIG. 1 shows a diffractive optical element in which the diffraction pattern p formed on the diffraction surface is circular when viewed from the direction of the optical axis 2, and includes the optical axis 2 of this diffractive optical element and is parallel to the optical axis. The cross-sectional shape in a simple cross-section is the staircase shape shown in FIG.
As shown in FIG. 2, the diffraction pattern p viewed from the optical axis 2 has a concentric shape (FIG. 2 (a)), an elliptical shape (FIG. 2 (b)), and a rectangular shape. ((C) of FIG. 2). Each of the cross-sectional shapes includes a step shape as shown in FIG. 3A and a relief shape as shown in FIG.

As a method of processing the diffraction pattern p having a straight cross-sectional shape as shown in FIG. 3, there is a processing method of cutting by relatively moving the cutting tool and the diffractive optical element molding die. FIG. 4 shows a state in which the diffraction pattern shown in FIG. 2C (a diffraction pattern having a rectangular shape when viewed from the optical axis) is cut into the diffractive optical element molding die 11. In other words, the diffraction pattern p is cut by moving the cutting tool 12 relative to the diffractive optical element molding die 11 in the Y-axis direction.
FIG. 5 shows a state of cutting the concentric circular shape of FIG. 2A and the elliptical diffraction pattern of FIG. 2B when viewed from the optical axis direction. In the figure, the diffractive optical element molding die 11 is rotated by the C-axis of the processing machine, and cutting is performed with the cutting tool 12. When the diffraction pattern is circular, the X coordinate position of the cutting tool 12 remains constant while processing one ring zone of the diffraction pattern p, but when processing an elliptical shape, one ring zone is processed. In doing so, cutting is performed while changing the X-coordinate position of the cutting tool 12 according to the shape of the ellipse.

Further, when the planar shape (the shape viewed from the optical axis direction) of the diffraction pattern p is an elliptical shape and the cross-sectional shape is a relief shape as shown in FIG. 3B, the B axis is set according to the inclination angle. Cutting is performed while changing the coordinate position.
In order to evaluate whether the diffraction pattern p of the diffractive optical element formed using the diffractive optical element molding die 11 has a desired shape, the pitch accuracy of the diffraction pattern p of the diffractive optical element is measured.

The measurement of the pitch accuracy of the diffraction pattern p is performed using a device capable of measuring the cross-sectional shape of the diffraction pattern p, such as a confocal microscope or a stylus shape measuring instrument.
When measuring the cross-sectional shape of the diffraction pattern p, the pitch can be accurately measured by measuring the shape of the cross-section including the optical axis of the diffraction pattern p (AA ′ cross-section) as shown in FIG. As shown in FIG. 6B, when the measurement is performed with a cross section (BB ′ cross section) that does not pass through the optical axis, the pitch cannot be measured accurately.

  Further, when measuring the cross-sectional shape of the diffraction pattern p, as a method of positioning the measuring device at a position where the accurate cross-sectional shape can be measured, the measurement alignment mark is used as the diffraction pattern p or the diffraction pattern p. There is a method of forming in adjacent regions.

In the case of the above prior art, the alignment mark is formed by lithography. When the diffraction pattern p is processed by lithography, the alignment mark can be formed by the same processing method, so that the alignment mark can be created at an accurate position. However, when the diffraction pattern p is formed by cutting, the accuracy of the relative positional relationship between the alignment mark and the diffraction pattern is deteriorated because the diffraction pattern processing and the alignment mark processing are performed in different processing steps. And there is a problem that processing time becomes long.
JP 2000-56114 A

  The present invention provides a processing method for forming a diffraction pattern on a diffractive optical element molding die, which has a high accuracy of the relative positional relationship between the alignment mark and the diffraction pattern, and devise a processing method that can reduce the processing effort. Is the issue.

Means for solving the above problems is a diffraction pattern in which a cross-sectional shape of a cross section including an optical axis and parallel to the optical axis is a plurality of linear shapes, and a planar shape viewed from the optical axis direction is circular or elliptical The following is a premise of a processing method of a diffractive optical element molding die for cutting a rectangular diffraction pattern by a turning or drawing method.
In the same way as cutting a diffraction pattern on a molding die formed by transferring a diffraction pattern to the diffraction surface of a diffractive optical element, at the same position, while performing relative movement when processing the diffraction surface, By performing a relative movement consisting of components in the normal direction of the cutting surface, the alignment mark is formed around the outside of the optical surface of the diffractive optical element or the effective area of the optical surface of the diffractive optical element , In the case of a circular or elliptical diffraction pattern, the alignment mark coincides with a part of a line segment passing through the diffraction surface from the optical axis, and from the optical axis in the case of a rectangular diffraction pattern. A plurality of lines are provided symmetrically with respect to the optical axis so as to coincide with a part of a line segment passing through the diffraction surface and orthogonal to the diffraction pattern of the diffraction surface .

And in the processing method of the diffractive optical element molding die in the above solution, the formed mark is used as an alignment mark when measuring the diffraction pattern.
When using this solution, a tool for cutting the transfer surface (transfer surface provided with the diffraction pattern) of the molding die for transfer-molding the diffraction surface of the diffractive optical element (surface on which the diffraction pattern is formed), Since the alignment mark can be formed in the same process as cutting the diffraction surface, the positional deviation between the alignment mark and the diffraction pattern can be extremely reduced, and the alignment pattern can be easily formed. .
Further, by forming a plurality of the above alignment marks, the inclination between the measuring direction of the measuring instrument and the cross section to be measured can be adjusted using these alignment marks .

(Inventions of Claims 3 to 6 )
In addition, as the shape of the alignment mark in the solving means, there are a mountain shape having a sharp top, a mountain shape having a flat portion on the top, a groove shape having a sharp valley, a groove shape having a flat portion, etc. These can be appropriately selected according to the characteristics of the measuring instrument to be measured and the characteristics of the processing machine.

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(Invention of Claim 7)
Further, when cutting the diffraction pattern having a circular shape when viewed from the optical axis direction, four orthogonal alignment marks are cut at 90 degree intervals around the optical axis, thereby obtaining two orthogonal directions. It becomes possible to accurately measure the cross-sectional shape.

(Invention of Claim 8)
Furthermore, in the diffraction pattern processing method of the diffractive optical element molding die of the above solution, when the shape of the diffraction pattern viewed from the optical axis direction is an elliptical shape, two points each in the major axis and minor axis directions of the elliptical shape By forming the alignment marks one by one, the cross-sectional shapes in the major axis direction and the minor axis direction can be accurately measured.

(Invention of Claim 9)
Furthermore, by the processing method of the diffractive optical element molding die according to the present invention, the above molding die having high positional accuracy between the diffraction pattern and the alignment mark can be obtained.

(Invention of Claim 10)
Further, a diffractive optical element with high accuracy is manufactured by molding the diffractive optical element with the diffractive optical element molding die according to the present invention.

The effects of the present invention are summarized as follows for each invention of each claim.
1. Inventions of Claims 1 and 2
The inventions of claims 1 and 2 are tools for cutting a diffraction pattern in a diffractive optical element molding die, and the alignment mark is formed in the same process as cutting the diffraction pattern. The positional deviation between the marks for use is extremely small, and the marks for alignment can be easily formed.
Since the alignment mark is formed in the effective area of the diffractive optical element or an area close to the effective area, the distance between the alignment mark and the diffraction pattern to be measured can be minimized, and the position with less error. Detection can be performed.
In addition, since there are a plurality of alignment marks, the inclination angle between the direction of the cross section to be measured and the measurement direction of the measuring instrument can be calculated by using the relative positional relationship of the alignment marks. The inclination between the scanning direction and the cross section to be measured can be adjusted .

2. Invention of Claims 3-6
The inventions of claims 3 to 6 are characterized in that the alignment mark has a peak shape with a sharp top, a peak shape with a flat portion on the top, a groove shape with a sharp valley, and a groove shape with a flat portion. It is possible to select an optimum one according to the characteristics of the measuring instrument to be measured and the characteristics of the processing machine. Therefore, more accurate measurement can be performed on the diffraction pattern of the diffractive optical element.

( Delete )

3. Invention of Claim 7 In the invention of Claim 7, four alignment marks are processed at intervals of 90 degrees around the optical axis of the diffraction pattern, and by using these marks, two orthogonal directions of the circular diffraction grating are used. It is possible to accurately measure the cross-sectional shape.

4). The invention of claim 8 According to the invention of claim 8, in the processing method of the diffractive optical element molding die of claim 1, in the case of a diffraction pattern having an elliptical shape when viewed from the optical axis direction, By forming alignment marks at two locations in the major axis and minor axis directions, the cross-sectional shapes of the diffraction pattern in the major axis direction and the minor axis direction can be accurately measured.

5). Invention of Claim 9 The diffractive optical element molding die produced by the invention of Claim 9 has high positional accuracy between the diffraction pattern and the alignment mark.

6). Invention of Claim 10 If the diffractive optical element shaping | molding die processed by this invention is used, a diffractive optical element with a high positional accuracy of a diffraction pattern and the alignment mark can be shape | molded.

Next, an embodiment will be described with reference to FIGS.
In a processing machine (FIG. 7) for cutting a diffraction pattern, 11 is a diffractive optical element molding die, 12 is a cutting tool, 13 is a C-axis rotation axis, 14 is an X-axis stage, 15 is a Y-axis stage, and 16 is Z Axis stage, 17 is a C-axis stage, 18 is a B-axis stage, and 19 is a processing machine main body. This processing machine has a 5-axis configuration including three linear axes of XYZ and two rotation axes of BC.

The linear 3-axis positioning resolution is 1 nm, and the BC 2-axis angular resolution is 1 / 100,000 degrees. The diffractive optical element molding die 11 is a mold metal material (for example, Ni-P plated on a stainless steel surface) that can be cut.
The diffractive optical element molding die 11 is clamped on the C-axis stage 17 with the surface to be processed (transfer surface of the die) facing upward. The cutting edge of the cutting tool 12 for cutting the diffraction pattern p and the alignment mark 3 is composed of a single crystal diamond tool.

  The tip of the cutting edge of the cutting tool 12 is positioned at a predetermined position in the XZ plane, the Z-axis slide and the Y-axis slide are lowered, and the control in each of the above-described axial directions is performed, and a diffraction pattern p as shown in FIGS. Is cut on the upper surface (transfer surface) of the mold 11, and after the diffraction pattern p is cut, the alignment mark 3 is cut.

FIG. 8 shows a state where the alignment mark 3 is being cut.
Cutting of the alignment mark 3 is performed in the order of (a) → (b) → (c) → (d) in FIG. 8A shows a state in which the upper surface (transfer surface) of the diffractive optical element molding die 11 is cut to form the alignment mark 3, and the diffractive optical element molding die 11 is cut into a cutting tool. 12 is moved relative to the surface in the Y direction to cut the surface. Further, in FIG. 5B, the cutting tool 12 is moved relative to the diffractive optical element molding die 11 in the Y direction and also moved in the Z axis direction. Due to the relative movement in the YZ2 axis direction, the left upward slope of the alignment mark 3 (right slope in the figure) is processed.

After the processing of the slope on one side of the alignment mark 3 is completed, the cutting tool 12 is moved in the direction opposite to the Z-axis direction as shown in FIG. Also in this case, since the relative movement simultaneously occurs in the YZ2 axis direction, a slope that rises to the right (left slope in the figure) is processed. After the required two slopes have been processed in this way, the same processing as the processing of the normal diffraction surface (the surface having the diffraction pattern p) is performed ((d) in FIG. 8).
FIG. 9A shows the alignment mark 3 processed by the cutting tool on the diffractive optical element molding die 11 as viewed from the positive direction of the Z-axis, and FIG. Shows the alignment mark 3 viewed from the positive direction of the X axis.

  FIG. 10 shows various examples of the shape of the alignment mark 3. The alignment mark 3a in FIG. 10A has a mountain shape with a sharp top, the alignment mark 3b in FIG. 10B has a trapezoidal shape with a flat top, and the alignment mark in FIG. 3c is a groove shape having a sharp valley, and the alignment mark 3d in (d) is a groove shape having a flat portion in the valley. Since these have V-shaped cross sections, they can be molded by controlling the cutting tool 12 and the diffractive optical element molding die 11 in the YZ direction. Then, according to the type of the measuring instrument, it is possible to select the most suitable one from among these alignment marks for accurate measurement.

  For example, when the type of measuring instrument is a confocal microscope, any pattern may be used, but when the type of measuring instrument is a stylus type shape measuring instrument, when the shape is (a) or (c), Since either the mold or the molded product has a valley shape with a sharp tip, the needle does not enter the valley portion, and accurate measurement cannot be performed. Therefore, when the measuring instrument is a stylus shape measuring instrument, it is preferable that the measuring instrument has the shape (b) or (d).

FIG. 11 shows an example in which the cross-sectional shape of the processed alignment mark 3 of type a (type (a) in FIG. 10) is measured with a confocal microscope, and FIG. 12 shows diffraction pattern measurement. The measuring instrument for is shown.
In FIG. 12, 1 is a diffractive optical element or a diffractive optical element molding die to be measured, 122 is a confocal microscope, 124 is an X-axis moving stage, 125 is a Y-axis moving stage, 126 Is a Z-axis moving stage, 127 is a C-axis direction rotary table, and 128 is a measuring instrument main body.
12 uses a confocal microscope 122 for measuring the cross-sectional shape of the measuring object 1 . However, a stylus type measuring instrument can be used instead of the confocal microscope 122.

A measurement object 1 which is a diffractive optical element or a diffractive optical element molding die is attached to a measuring instrument, and then the cross-sectional shape of the measurement object 1 is measured by scanning the measurement object 1 with the confocal microscope 122. When performing this measurement, the alignment error of the measuring object 1 is measured using the alignment mark 3 so that the confocal microscope 122 accurately scans the cross section of the position to be measured, and the measured error is measured. Based on the above, the measuring object 1 is aligned using the moving stage (X-axis moving stage 124 , Y-axis moving stage 125 , Z-axis moving stage 126 ) and rotating stage (C-axis direction rotating table 127 ) of the measuring instrument. After that, the cross section is measured.

FIG. 13 shows a state in which the measuring object 1 is aligned using the alignment mark 3. FIG. 13A shows a state in which the measuring object 1 is placed on the measuring instrument. In this state, the confocal microscope 122 of FIG. 12 scans in the Y-axis direction to measure two positions of the alignment mark 3. By this measurement, the inclination angle θ between the X axis of the measuring instrument and the alignment mark 3 is measured, and the inclination is adjusted using the C axis direction rotary table of the measuring instrument based on the measured value. The X axis and the alignment mark 3 are made parallel ((b) of FIG. 13). Then, the alignment mark 3 is measured at two positions on the left and right sides, and the X and Y coordinates of the center position of the diffractive optical element 1 after being rotated by the angle θ are also measured in order to measure the position in the X-axis direction. A value can be calculated. Based on the coordinate values obtained by performing a measurement by setting to match the cross section to be measured scanning position location 8 of the confocal microscope, it is possible to perform accurate measurement (in Fig. 13 (c )).

FIG. 14 shows another example. In this example, the diffraction pattern p viewed from the optical axis direction has a circular shape in the diffractive optical element 1 at 90 ° intervals with the optical axis of the optical element as the center. Four alignment marks 3 are formed.
In the alignment in this example, the processing shown in FIG. 13 is performed for each alignment mark, and the cross-sectional shape at each alignment mark is measured.

FIG. 15 shows a diffractive optical element 1 having an elliptical diffraction pattern p as viewed from the optical axis direction, and two in each of the major axis and the minor axis direction of the elliptical diffraction pattern p. This is an example in which the alignment mark 3 is formed.
In the case of this example, the process shown in FIG. 13 is performed for the long axis and short axis alignment marks , and the cross-sectional shape is measured.

FIG. 16 shows an example in which two alignment marks 3 are formed on a diffractive optical element 1 having a rectangular diffraction pattern p viewed from the optical axis direction.
Even when the pattern is rectangular, measurement is performed by using the alignment mark and setting the scanning position of the confocal microscope so as to coincide with the cross section to be measured, as in FIG.

The diffraction pattern of the diffraction surface viewed from the direction of the optical axis 2 is circular, the cross section of the diffraction pattern including the optical axis 2 and in a cross section parallel to the optical axis is the staircase shape shown in FIG. It is a perspective view of a thing. These are top views which show the example of the shape of the diffraction element seen from the optical axis 2, a figure (a) is a concentric thing, a figure (b) is an elliptical figure, and a figure (c) is a rectangular thing. It is a top view. These are sectional drawings which show the example of the cross-sectional shape of a diffraction element, A figure (a) is a step-shaped thing, A figure (b) is sectional drawing of a relief shape. These are perspective views which show a mode that it cuts into the transfer surface of the diffraction optical element shaping | molding die whose shape of the diffraction pattern seen from the optical axis is a rectangle like FIG.2 (c). These are the perspective views which showed a mode that the shape seen from the optical axis direction cuts the diffraction pattern which is the concentric circle of (a) of FIG. 2, and the ellipse of (b). These are the reference drawings for demonstrating the relationship between the cross-sectional shape of the scanning line of a diffraction pattern in the case of measuring cross-sectional shape, and the measurement precision of the pitch of a diffraction pattern, (a) is the diffraction in an AA 'cross section. Explanatory drawing which shows the cross-sectional shape of a pattern, (b) is explanatory drawing which shows the cross-sectional shape of the diffraction pattern in a BB 'cross section. These are perspective views of the processing machine which cuts a diffraction optical element shaping die. FIG. 9 is an explanatory view schematically showing a state in which the alignment mark 3 is being cut; FIGS. 8A, 8B, 8C, and 8D are diffractive optical element molding dies. The transfer surface is cut to form the alignment mark 3 respectively. (A) is a plan view of the alignment mark 3 formed by cutting as viewed from the positive direction of the Z axis, and (b) is a front view of the alignment mark 3 as viewed from the positive direction of the X axis. FIG. (A), (b), (c), (d) is sectional drawing of the various examples of the alignment mark. These are explanatory drawings which show the example which measured the cross-sectional shape of the alignment mark 3 of the a type (type shown to Fig.10 (a)) shape | molded by the confocal microscope. FIG. 3 is a perspective view of a measuring instrument for measuring a diffraction pattern . These are explanatory drawings which perform alignment of a diffractive optical element using an alignment mark, and (a), (b), and (c) of the same figure are plan views of the diffractive optical element showing a work procedure. . FIG. 5 is a plan view of an example in which four alignment marks 3 are formed at intervals of 90 degrees around the optical axis in a diffractive optical element whose diffraction pattern viewed from the optical axis direction is circular. FIG. 4 is a plan view of an example in which alignment marks are formed at a total of four locations on the diffractive optical element having an elliptical diffraction pattern viewed from the optical axis direction in two locations in the major axis and minor axis directions. FIG. 5 is a plan view of an example in which two alignment marks are formed on a diffractive optical element having a rectangular diffraction pattern viewed from the optical axis direction.

1: diffractive optical element 2: optical axis 3: alignment mark 3a: mountain-shaped alignment mark 3b with a sharp top, trapezoidal alignment mark 3c with a flat top: groove with a sharp valley Shape alignment mark 3d: groove-shaped alignment mark having a flat portion in the valley
11: Diffraction optical element molding die 12: Cutting tool 13: C-axis rotating shaft 14: X-axis stage 15: Y-axis stage 16: Z-axis stage 17: C-axis stage 18: B-axis stage 19: Processing machine body 122: Confocal microscope
124: X-axis moving stage 125: Y-axis moving stage 126: Z-axis moving stage 127: C-axis direction rotary table
128: Measuring instrument body p: Diffraction pattern

Claims (10)

A method of processing a molding die for a diffractive optical element having a diffraction pattern in which a cross-sectional shape in a cross section including an optical axis and parallel to the optical axis has a plurality of linear shapes, and the shape viewed from the optical axis direction is circular in or diffractive optical element molding die machining method of forming a diffraction pattern to be elliptical cut cutting to,
Using the tool cutting the diffraction pattern, while relatively moving the switching cutting tool and the workpiece, at a particular location, when the relative movement when a diffraction surface is formed at the same time, the normal direction of the cutting plane By performing the relative movement consisting of the components of cutting, the alignment mark is formed around the outer surface of the optical surface of the diffractive optical element or the effective area of the optical surface of the diffractive optical element ,
A method for processing a diffractive optical element molding die, wherein a plurality of the alignment marks are provided symmetrically with respect to the optical axis so as to coincide with a part of a line segment passing from the optical axis through the diffraction surface . A method for processing a molding die of a diffractive optical element having a diffraction pattern in which a cross-sectional shape in a cross section including an optical axis and parallel to the optical axis has a plurality of linear shapes, and the shape viewed from the optical axis direction is rectangular In the diffractive optical element molding die processing method for cutting and forming the diffraction pattern to be
Using the tool for cutting the diffraction pattern, while moving the cutting tool and the workpiece relative to each other, the relative movement when machining the diffractive surface at a specific position is performed simultaneously with the normal direction of the cutting surface. By performing relative movement consisting of components and cutting, an alignment mark is formed around the outer surface of the effective surface of the optical surface of the diffractive optical element or the optical surface of the diffractive optical element ,
A plurality of the alignment marks are provided symmetrically with respect to the optical axis so as to coincide with a part of a line segment passing through the diffraction surface from the optical axis and orthogonal to the diffraction pattern of the diffraction surface. Method of processing a diffractive optical element molding die. 3. The diffractive optical element molding die according to claim 1, wherein a cross-sectional shape of the alignment mark to be created is a mountain shape having a sharp top. Processing method. 3. The diffractive optical element molding die according to claim 1, wherein a cross-sectional shape of the alignment mark to be created is a mountain shape having a flat portion on the top. Mold processing method. 3. The diffractive optical element molding die according to claim 1, wherein a cross-sectional shape of the alignment mark to be formed is a groove shape having a sharp valley. Processing method. The diffractive optical element molding die according to claim 1 or 2 , wherein the cross-sectional shape of the alignment mark to be created is a groove shape having a flat portion in a valley. Mold processing method.   2. The processing method for a diffractive optical element molding die according to claim 1, wherein when processing a diffraction pattern having a circular shape when viewed from the optical axis direction, the positioning is performed at intervals of 90 degrees about the optical axis of the element. A method of processing a diffractive optical element molding die, wherein four marks are processed.   2. The processing method of a diffractive optical element molding die according to claim 1, wherein when processing the diffraction pattern having an elliptical shape when viewed from the optical axis direction, two each in the major axis and minor axis directions of the diffraction pattern. A method of processing a diffractive optical element molding die, wherein the positioning mark is processed. A molding die produced by the processing method of the diffractive optical element molding die according to claim 1 .   A diffractive optical element molded with the molding die according to claim 9.

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