JP4281469B2 - Electron beam drawing method, method for producing mold for molding using the method, die produced, and optical element molded with the die - Google Patents

Description

The present invention relates to an electron beam drawing method , a method for manufacturing a molding die using the method, a manufactured die, and an optical element molded with the die.

  Conventionally, optical recording media such as CDs and DVDs have been widely used as information recording media. Many optical elements are used in precision equipment such as an apparatus for recording / reproducing information on these recording media. For example, in an optical head device that records / reproduces information such as CDs and DVDs, a semiconductor laser having a wavelength of 790 nm and a semiconductor laser having a wavelength of 650 nm are arranged in one light source unit, and the same light is obtained without increasing the area of the light receiving surface. In order to obtain an optical head device capable of focusing on a detector, an optical element having a quasi-blazed diffraction grating for two wavelengths has been proposed (see Patent Document 1).

Optical elements used in these devices, such as optical lenses and optical aberration correction elements, are often made of resin rather than glass from the viewpoint of cost reduction and size reduction. Such resin-made optical elements are manufactured by general injection molding, and blazed gratings and the like are press-molded (see Patent Document 2), but these molds are formed by general cutting. Has been.
JP 2002-62415 A JP-A-10-72221

  In particular, when reading a high-density recording medium, such as a pickup device using a blue laser compatible with the next-generation DVD, it is necessary to further refine the pattern of the diffraction grating structure. The blazed diffraction structure having a pattern is also required to be miniaturized on the order of submicrons.

  When such processing is performed, there is a limit in conventional cutting processing and laser processing, so it is conceivable to use an electron beam drawing apparatus. In other words, by using an electron beam lithography system, the resin layer formed on the surface of the mold of the optical element is irradiated with an electron beam and scanned, and the scan dose is changed, thereby blazing various binary patterns. A diffractive structure is drawn on the resin layer. Thereafter, a diffractive structure is formed by development such as dry etching.

  However, since the minimum change amount that can be set by the electron beam dose amount of the electron beam lithography apparatus is determined by the minimum conversion time that can be set by the D / A converter, the dose amount in such an electron beam lithography apparatus is determined. The adjustment becomes remarkably stepwise, especially when drawing so as not to spend time at a high current value. For example, when drawing a blazed diffraction structure or the like, an attempt is made to form a gentle blazed inclined surface. However, the shape of the blaze inclined surface obtained after drawing / development becomes a step shape due to the restriction on the minimum change amount of the dose.

  Such a stepped shape of the blazed inclined surface causes a decrease in optical characteristics of an optical element such as an optical lens, particularly a decrease in diffraction efficiency. In addition, when considering the quality of the product, the product value is reduced. In order to improve the diffraction efficiency of the optical lens and the like, and to increase the product value, it is necessary to make the blaze inclined surface as gentle as possible.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to form a lens capable of forming an aberration-correcting diffraction structure on an optical lens without lowering diffraction efficiency or product value. An object of the present invention is to produce a mold, and further, an optical element molding die such as an optical aberration correction element by using drawing by an electron beam drawing apparatus.

The above object of the present invention is to
1) When drawing on a substrate by scanning with irradiation with an electron beam,
A first step of drawing by scanning the electron beam with a first dose;
A second step of drawing by scanning the electron beam with a second dose amount;
A third step of providing a region in which a portion drawn with the first dose amount and a portion drawn with the second dose amount are mixed;
Including an electron beam drawing method,
2) The difference between the first dose amount and the second dose amount is based on a minimum clock of a D / A converter for driving an electron gun of an electron beam lithography apparatus that irradiates the electron beam. 1) Electron beam drawing method which is the minimum adjustment unit (minimum displacement) of the dose,
3) A portion in which, in the third step, a region drawn with the first dose amount and a region drawn with the second dose amount are periodically and repeatedly provided in the electron beam scanning direction. 1) or 2) electron beam drawing method,
4) The electron beam drawing method according to 3), wherein an area to be drawn with the first dose amount is drawn at a position that substantially coincides between adjacent scanning lines.
5) The electron beam drawing method according to 3), wherein the region to be drawn with the first dose amount is drawn at different positions between adjacent scanning lines.
6) The electron beam drawing method according to 3), wherein a region to be drawn with the first dose is drawn in a staggered position between adjacent scanning lines.
7) Using the electron beam drawing method according to any one of 1) to 6),
A method for producing a molding die including a step of developing a substrate drawn with an electron beam and performing electroforming on the developed substrate;
8) The manufacturing method of the metal mold | die for a shaping | molding of 7) which electrocasts to the processed developed base material.
9) A mold manufactured by the manufacturing method of 7) or 8),
10) An optical element molded with the mold of 9),
Achieved by:

  That is, the present inventor, for example, when forming the inclined portion of the blazed diffraction grating on the base material for producing the mold of the optical element by electron beam drawing, the portion drawn with the first dose amount, Drawing with the second dose amount from the region to be drawn with the first dose amount after drawing based on the dose amount mixed region in which the portion to be drawn with the second dose amount that is larger by the minimum displacement of the dose amount is mixed The inclination obtained by developing after drawing is moderated by shifting the area drawn based on the mixed dose area due to the proximity effect etc. to an intermediate height. Invented.

  According to the present invention, a lens molding die capable of forming an aberration correcting diffraction structure on the light converging surface side of an optical lens without causing a decrease in diffraction efficiency or a product value, and an optical aberration correcting element An optical element mold such as the above can be produced by drawing with an electron beam drawing apparatus.

  Hereinafter, the present invention will be specifically described with reference to the drawings using embodiments, but the present invention is not limited thereto.

  First, a blazed diffraction grating is formed by drawing a circle on a prototype (in the present invention, including a resin layer, which is referred to as a base material) having a convex curved surface shape and coated with a resin layer. The case where the structure is formed concentrically will be described as an example. The substrate is not limited to this, and may be, for example, a concave curved surface or a flat surface, and the diffractive structure may be a binary pattern.

  FIG. 1 shows an example of a drawing pattern and details of the drawing shape. As shown in the figure, a blazed diffraction grating structure is formed on one surface of a base material 2 having a curved surface shape, and a plurality of blazes 3 are formed concentrically by enlarging part E. Yes. The blaze 3 forms an inclined portion 3b and a side wall portion 3a, and the side wall portion 3a is formed in a plurality of stages in a planar shape along the circumferential direction.

  More specifically, as shown in FIG. 2, on the base material 2, lattice strips are formed for each pitch L <b> 1 with respect to the original curved surface portion 2 a serving as a base, and at least one pitch L <b> 1 of the lattice strips, The side wall portion 3a rising from the curved surface portion 2a at the pitch break, the inclined portion 3b formed between the adjacent side wall portions 3a, and the boundary region between the side wall portion 3a and the inclined portion 3b. And a groove 3c.

  The inclined portion 3b constitutes an inclined surface with one end in contact with the base end of one side wall portion 3a and the other end in contact with the tip end of the other side wall portion 3a. The diffraction grating structure composed of a plurality of blazes 3 is formed by coating the curved surface portion 2a, drawing a resin layer formed by coating using an electron beam drawing apparatus described later, and developing the blaze. The inclined portion 3b 3 forms a gentle inclined surface by drawing using an electron beam drawing apparatus described later.

  3A and 3B are enlarged views of the dose distribution 300 for drawing the F portion which is a part of the inclined portion 3b. The dose difference h between the regions 301, 302, and 303 is a minimum dose adjustment unit (minimum displacement) based on the minimum clock of the D / A converter for driving an electron gun of an electron beam lithography apparatus described later. is there. Between each of the regions 301 and 302 that are changed stepwise by this minimum change amount of the dose amount, and between 302 and 303, a dose amount mixed region MIX in which both the dose amounts changed stepwise are mixed. ing.

  In the dose mixed region, the interval between each concave portion and the convex portion is constant as shown in FIG. 5A, or in the direction in which the height of the inclined portion 3b is lowered as shown in FIG. It is preferable that the distance is set so as to increase as it goes. However, in this case, what is important is the proximity effect of the electron beam that is drawn with the dose distribution in which the width of the drawing portion where the dose amount is set to be concave and the width of the drawing portion where the dose amount is set to be convex, respectively. It is configured to be smaller than the expected spread, and more preferably smaller than the diameter of the electron beam for drawing the portion.

  As shown in FIG. 3B, more specifically, when the dose is set so that the distance between the concavo-convex portions becomes wider as the height of the inclined portion 3b decreases, As shown in FIG. 4, the dose amount mixed region MIX is configured by a plurality of, for example, three (in practice, an appropriate number according to the inclination angle of the inclined surface) of convex portions BI1, BI2, and BI3. BI1 has a length T1, convex portion BI2 has a length T2, and convex portion BI3 has a length T3.

  In this dose distribution, the upper surfaces of the convex portions BI1, BI2, and BI3 are the “first dose amount” in the present invention, and the bottom surface of the concave portion between the convex portions BI1, BI2, and BI3 is the “second dose” in the present invention. The dose amount. The difference between the first dose amount and the second dose amount mentioned here is the minimum unit of the dose change amount that can be adjusted based on the minimum clock of the D / A converter of the electron beam lithography apparatus as described above. It has become.

  Here, assuming that the pitch of the concave and convex portions is U1 = U2 = U3, the distances between the convex portions BI1, BI2, and BI3 are V1, V2, and V3, and U1 = T1 + V1, U2 = T2 + V2, and U3 = T3 + V3, for example, When T1> T2> T3 and V1 <V2 <V3, the duty ratio becomes (T1 / U1)> (T2 / U2)> (T3 / U3) and the height of the inclined portion 3b is reduced. The lengths T1, T2, and T3 of the convex portions BI1, BI2, and BI3, which are the first dose portions, can be reduced stepwise as they go to the second dose portion. be able to.

  As described above, when the distance between the projections and depressions of the dose mixed region MIX is constant, the duty ratio is (T1 / U1) = (T2 / U2) = (T3 / U3). Further, the number of irregularities set in the dose mixed region MIX may be changed according to the size of the blaze and the inclination angle. Therefore, for example, the blazing in the central region of the curved surface portion 2a may have a small number of unevenness settings, and the unevenness setting may be increased as the blazing occurs on the peripheral side. However, in any case, the range (U1 + U2 + U3) in which the unevenness of the dose amount mixed region MIX is set is within the blaze inclination angle (more specifically, the change amount of the dose amount when drawing the blaze). It will be decided accordingly.

  The circle drawing may be drawn by approximating with a plurality of straight line portions, and the substrate 2 is preferably formed in the shape of an optical element such as a pickup lens. The details of drawing the circle drawing by approximating the drawing with a plurality of straight line portions will be described in the description of the electron beam drawing apparatus (specific configuration of the control system) described later.

(Configuration of electron beam lithography system)
FIG. 5 shows the overall configuration of the electron beam drawing apparatus according to the present invention.

  The electron beam drawing apparatus 1 includes an electron gun 12 which is an electron beam generating means for generating an electron beam and irradiating the base material 2 with a beam, a slit 14 for passing the electron beam from the electron gun 12, and a slit An electron lens 16 for controlling the focal position of the electron beam passing through the substrate 2 with respect to the substrate 2, an aperture 18 disposed on a path through which the electron beam is emitted, and a target by deflecting the electron beam. A deflector 20 that controls the scanning position on the substrate 2 and a correction coil 22 that corrects the deflection are included. These parts are disposed in the lens barrel 10 and are in a vacuum state when the electron beam is emitted. Maintained.

  Further, the electron beam drawing apparatus 1 includes an XYZ stage 30 that is a placement table for placing the base material 2 to be drawn, and a transport for transporting the base material 2 to a placement position on the XYZ stage 30. A loader 40 as a means, a measuring device 80 as a measuring means for measuring a reference point of the surface of the base material 2 on the XYZ stage 30, and a stage driving means 50 as a driving means for driving the XYZ stage 30. A loader driving device 60 for driving the loader, a vacuum exhaust device 70 for exhausting the interior of the lens barrel 10 and the housing 11 including the XYZ stage 30 so as to be evacuated, and control means for controlling these And a control circuit 100.

  The electronic lens 16 is a device in which a plurality of electronic lenses are generated by the current values of the coils 17a, 17b, and 17c that are spaced apart from each other along a height direction. The focal position of the electron beam is controlled.

  The measuring device 80 includes a first laser length measuring device 82 that irradiates the base material 2 with a laser, and a base material of laser light (first irradiation light) emitted by the first laser length measuring device 82. 2, a second laser length measuring device 86 that performs irradiation from an irradiation angle different from that of the first laser length measuring device 82, and the second laser measurement time. And a second light receiving portion 88 that receives the reflected light of the laser light (second irradiation light) emitted from the length device 86 on the base material 2. The first laser length measuring device 82 and the first light receiving portion 84 constitute a “first optical system”, and the second laser length measuring device 86 and the second light receiving portion 88 constitute the “second optical system”. Optical system ”.

  The stage drive means 50 includes an X direction drive mechanism 52 that drives the XYZ stage 30 in the X direction, a Y direction drive mechanism 54 that drives the XYZ stage 30 in the Y direction, and a Z direction drive that drives the XYZ stage 30 in the Z direction. The mechanism 56 includes a θ-direction drive mechanism 58 that drives the XYZ stage 30 in the illustrated θ direction. Note that a drive mechanism that rotates in another direction may be provided so that the stage can be pitched, yawed, or rolled. As a result, the XYZ stage 30 can be operated three-dimensionally and alignment can be performed.

  The control circuit 100 includes an electron gun power supply unit 102 for supplying power to the electron gun 12, an electron gun control unit 104 for adjusting and controlling current and voltage in the electron gun power supply unit 102, and an electron lens 16 (multiple And a lens control unit 108 that adjusts and controls each current corresponding to each electronic lens in the lens power supply unit 106. The electron gun power supply unit 102 includes a D / A converter (not shown) for supplying power to the electron gun 12, and the electron gun control unit 104 is provided in the D / A converter (not shown). By adjusting and controlling current, voltage, etc., the dose amount of the electron beam emitted from the electron gun 12 is adjusted. Therefore, based on the minimum clock of the D / A converter, the dose amount (minimum change amount of the dose amount) of the minimum adjustment unit of the electron beam drawing apparatus is determined.

  Further, the control circuit 100 includes a coil control unit 110 for controlling the correction coil 22, a shaping deflection unit 112 a for deflecting in the molding direction by the deflector 20, and a deflection in the sub-scanning direction by the deflector 20. A sub-deflection unit 112b for performing the deflection, a main deflection unit 112c for performing deflection in the main scanning direction by the deflector 20, and a high-speed D / D that converts and controls a digital signal to an analog signal to control the shaping deflection unit 112a. A converter 114a, a high-speed D / A converter 114b that converts and converts a digital signal into an analog signal to control the sub-deflector 112b, and a digital signal that is converted to an analog signal to control the main deflector 112c High-precision D / A converter 114c.

  Further, the control circuit 100 supplies a position error correction signal for correcting a position error in the deflector 20 to each of the high-speed D / A converters 114a and 114b and the high-precision D / A converter 114c. A position error correction circuit 116 that performs position error correction by urging position error correction or supplying the signal to the coil control unit 110 by the correction coil 22, the position error correction circuit 116, and each high-speed D Electric field control circuit 118 which is an electric field control means for controlling the electric field of the electron beam by controlling the / A converters 114a and 114b and the high precision D / A converter 114c, and a drawing pattern and the like are generated for the substrate 2 And a pattern generation circuit 120 for performing the above operation.

  Further, the control circuit 100 includes a first laser drive control circuit 130 that controls the movement of the laser irradiation position and the laser irradiation angle by moving the first laser length measuring device 82 up and down, left and right, and the like. A second laser drive control circuit 132 that controls the drive of the laser irradiation position and the laser irradiation angle by moving the second laser length measuring device 86 up and down, left and right, and the first laser length measuring device In order to adjust and control the output of the laser irradiation light from the first laser output control circuit 134 for adjusting and controlling the output (laser light intensity) of the laser irradiation light at 82 and the second laser length measuring device 86 The second laser output control circuit 136, the first measurement calculation unit 140 for calculating the measurement result based on the light reception result of the first light receiving unit 84, and the second light receiving unit. Based upon the received results in 8, and a second measurement calculating section 142 for calculating the measurement results.

  Further, the control circuit 100 includes a stage control circuit 150 for controlling the stage driving means 50, a loader control circuit 152 for controlling the loader driving device 60, and the above-described first and second laser driving circuits 130, 132, A mechanism control circuit 154 for controlling the first and second laser output control circuits 134 and 136, the first and second measurement calculation units 140 and 142, the stage control circuit 150, and the loader control circuit 152; An evacuation control circuit 156 for controlling evacuation, a measurement information input unit 158 for inputting measurement information, a memory 160 which is a storage means for storing various pieces of input information and other plural information, A program memory 162 storing a control program for performing various controls, a control system 300 (described later in detail), and each of these units Responsible for controlling, for example, a and a control unit 170 formed by such CPU.

  Further, in the electron beam drawing apparatus 1 of the present embodiment, in the so-called “operation system” or “operation means” including the measurement information input unit 158, the analog scan method / digital scan method is selected and the basic shape is selected. Various command operations such as selection from a plurality of drawing patterns are possible.

  In the electron beam drawing apparatus 1 described above, when the base material 2 conveyed by the loader 40 is placed on the XYZ stage 30, the vacuum exhaust device 70 removes air, dust, and the like in the lens barrel 10 and the casing 11. After exhausting, an electron beam is irradiated from the electron gun 12.

  The electron beam irradiated from the electron gun 12 is deflected by the deflector 20 through the electron lens 16 and is deflected by the deflected electron beam B (hereinafter, only with respect to the electron beam whose deflection is controlled after passing through the electron lens 16, “ Drawing may be performed by irradiating the drawing position on the surface of the base material 2 on the XYZ stage 30, for example, the curved surface portion (curved surface) 2a.

  At this time, the drawing position on the substrate 2 (at least the height position among the drawing positions) or the position of a reference point as will be described later is measured by the measuring device 80, and the control circuit 100 is based on the measurement result. Then, the current values flowing through the coils 17a, 17b, and 17c of the electron lens 16 are adjusted and controlled to control the focal depth of the electron beam B, that is, the focal position, and the movement control is performed so that the focal position becomes the drawing position. To do.

  Alternatively, based on the measurement result, the control circuit 100 controls the stage driving unit 50 to move the XYZ stage 30 so that the focal position of the electron beam B becomes the drawing position. Note that either of the control of the electron beam and the control of the XYZ stage 30 may be used.

<Measurement device 80>
As shown in FIG. 6, the measuring device 80 includes a first laser length measuring device 82, a first light receiving portion 84, a second laser length measuring device 86, a second light receiving portion 88, and the like.

  The first optical system irradiates the first light beam S1 from the direction intersecting the electron beam by the first laser length measuring device 82, and receives the first light beam S1 transmitted through the substrate 2 as the first light reception. The first light intensity distribution is detected by receiving light by the unit 84. As shown in FIG. 6, the first light intensity distribution is based on the reflected light from the flat portion 2b of the base material 2 of the light beam S1 transmitted through the curved surface portion 2a of the base material 2. Height) position cannot be measured.

  Therefore, in this example, a second optical system is further provided, and the second laser beam length measuring device 86 irradiates the second light beam S2 from a direction substantially orthogonal to the electron beam, and transmits the second light beam S2. The second light intensity distribution is detected by receiving the second light beam S2 through the pinhole 89 included in the second light receiving unit 88.

  In this case, as shown in FIG. 6, since the second light beam S2 passes across the curved surface portion 2a, the (height) position on the curved surface portion 2a is determined based on the second intensity distribution. Measurement can be calculated.

  Specifically, when the second light beam S2 passes through a certain position on the curved surface portion 2a (the coordinate on the XY stage is (x ′, y)) parallel to the X axis, the light beam is at this position. Scattering due to reflection or refraction caused by S2 passing through the curved surface occurs, and the light intensity corresponding to the scattered light is weakened. Therefore, based on the light intensity of the light beam 2 detected by the second light receiving unit 88, the depth of the focal position (x, y) of the electron beam is set to the position (x ′, It can be calculated in correspondence with the height of y).

  That is, when the correlation between the signal output (referred to as Op) corresponding to the light intensity detected by the second light receiving unit 88 and the height of the substrate is obtained, a characteristic diagram as shown in FIG. 7 is obtained. By storing a correlation table indicating this characteristic, that is, a correlation, in advance in the memory 160 of the circuit 100, the base material of the focal position of the electron beam based on the signal output Op from the second light receiving unit 88. The height position inside can be calculated. Thus, the drawing is performed by adjusting the drawing position and the focal position of the electron beam.

<Outline of drawing position calculation method>
Next, an outline of a drawing position calculation method when the electron beam drawing apparatus 1 is used will be described.

  First, as shown in FIGS. 8A and 8B, the substrate 2 of the present embodiment has an optical element shape such as an optical lens, and has a flat portion 2b having a substantially flat cross section and a flat portion 2b. And a curved surface portion 2a that forms a curved surface that protrudes. The curved surface of the curved surface portion 2a is not limited to a spherical surface, but may be an aspherical surface or a free curved surface having changes in all height directions.

  First, before mounting on the XYZ stage 30, a plurality of, for example, three reference points P00, P01, P02 on the substrate 2 are determined in advance and their positions are measured (first measurement). . Thereby, for example, the X axis is defined by the reference points P00 and P01, the Y axis is defined by the reference points P00 and P02, and the first reference coordinate system in the three-dimensional coordinate system is calculated. Here, the height position in the first reference coordinate system is assumed to be Ho (x, y) (first height position). Thereby, the thickness distribution of the base material 2 can be calculated.

  On the other hand, similar processing is performed after the substrate 2 is placed on the XYZ stage 30. That is, as shown in FIG. 8A, a plurality of, for example, three reference points P10, P11, P12 on the substrate 2 are determined and their positions are measured (second measurement). Thereby, for example, the X axis is defined by the reference points P10 and P11, the Y axis is defined by the reference points P10 and P12, and the second reference coordinate system in the three-dimensional coordinate system is calculated.

  Further, a coordinate conversion matrix for converting the first reference coordinate system to the second reference coordinate system is calculated by using these reference points P00, P01, P02, P10, P11, and P12. The height position Hp (x, y) (second height position) corresponding to the Ho (x, y) in the second reference coordinate system is calculated, and this position is determined as the optimum focus position, In other words, the focus position of the electron beam is set as the drawing position. Thereby, correction of the thickness distribution of the above-mentioned base material 2 can be performed.

  In addition, the above-mentioned 2nd measurement can be measured using the measuring apparatus 80 which is a measuring means of the electron beam drawing apparatus 1. FIG. In addition, the first measurement is performed in advance using another measuring device in another place. As another measuring apparatus, a measuring apparatus 200 (not shown) having the same configuration as that of the above-described measuring apparatus 80 can be employed.

  In this case, the measurement result in the measurement apparatus 200 is input by, for example, the measurement information input unit 158 shown in FIG. 5 or is transferred through a network (not shown) connected to the control circuit 100. It is stored in the memory 160 or the like.

  As described above, the drawing position is calculated, and the focal position of the electron beam is controlled to perform drawing.

  Specifically, as shown in FIG. 8C, first, a unit space for drawing is set by a three-dimensional reference coordinate system, and the position of the focal depth FZ of the electron beam is set to one field (m = 1) Adjust and control the drawing position within. (This control is performed by either or both of the adjustment of the current value by the electron lens 16 and the drive control of the XYZ stage 30 as described above.) In this example, the height of one field is set. Although the field is set so as to be longer than the focal depth FZ, it is not limited to this.

  Here, as shown in FIG. 9, the depth of focus FZ indicates the height of a range in which the beam waist (the narrowest part of the beam diameter) BW is effective in the electron beam B irradiated through the electron lens 16. . In this embodiment, assuming that the width D of the electron lens 16 and the depth f from the electron lens 16 to the beam waist BW are D / f is about 0.01, and has a resolution of, for example, about 50 nm. The depth of focus is, for example, about several tens of μm.

  Then, as shown in FIG. 8C, for example, drawing in one field is performed by sequentially scanning in the X direction while shifting in one field in the Y direction. Further, if there is an undrawn area in one field, the area is also moved in the Z direction while controlling the above-described focal position, and the drawing process by the same scanning is performed.

  Next, after drawing in one field, drawing processing is performed while measuring and calculating the drawing position in other fields, for example, the field of m = 2 and the field of m = 3, as described above. It will be done in real time.

  In this way, when all the drawing is finished for the drawing area to be drawn, the drawing process on the surface of the substrate 2 is finished.

  In this example, the drawing region is a drawing layer, and a portion corresponding to the curved surface of the curved surface portion 2a in the drawing layer is a drawing surface. In addition, a processing program for performing processing such as various arithmetic processing, measurement processing, and control processing described above is assumed to be stored in advance in the program memory 162 as a control program.

<Drawing order>
The curved portion of the substrate 2 placed on the XYZ stage 30 in FIG. 3 is divided into a plurality of fields (drawing units) as shown in FIGS. 10A and 10B, and the electron beam in FIG. 3 is scanned. The fields are conveyed in a predetermined order within the maximum possible scanning area in the scanning space.

  The drawing pattern assigned to the field conveyed to the scanning area is drawn by scanning the electron beam in the X direction and Y direction as shown in FIG.

  When drawing of the drawing pattern assigned to the target field is completed, the adjacent field is set as the next drawing target field, and drawing is started. Thus, the drawing method of this embodiment is a step-and-repeat method in which drawing is performed for each field.

  In the field arrangement examples shown in FIGS. 10A and 10B, the fields are arranged concentrically, and each field has a fan shape. As the drawing order of the plurality of fields arranged concentrically in this way, for example, drawing is performed on the first group field located at the top of the center of the concentric circle, and then the lower order of the first group field. To draw the second group of fields on the same circumferential surface, and then to draw the third group of fields on the same circumferential surface located below the second group of fields, There is a method of performing drawing sequentially downward, but the method is not limited to this.

<Specific configuration of dose control system>
FIG. 11 is a functional block diagram of a control system of the electron beam drawing apparatus according to the present invention.

  The memory 160 of the electron beam drawing apparatus 1 has a shape memory table 161. In the shape memory table 161, for example, the curved portion 2a of the substrate 2 and the inclined portion 3b and the side wall portion 3a of the blaze 3 are as desired. In addition, an ideal dose distribution corresponding to a drawing position when forming each pitch L, a set dose distribution obtained by approximating the ideal dose distribution with a minimum dose displacement (change amount) of the electron beam drawing apparatus, or blaze 3 The dose distribution information 161a in which the dose distribution (the dose distribution related to the length of the convex portion and the distance between the convex portions) and the like relating to the uneven portion when forming the mixed dose inclined portion 3bb in the inclined portion 3b is stored. .

  Further, the memory 160 includes an ideal dose function f (n) representing an ideal dose distribution, a set dose function D (n) representing a set dose distribution, and a mixing constant w [%] for setting a range of a dose amount mixed region. The dose amount mixed region calculation information 161b that defines the correlation of the dose, the dose distribution correction calculation information 161c obtained by correcting the set dose function D (n) based on the dose amount mixed region calculation information 161b, and other information 161d are stored. Has been. The ideal dose function f (n) representing the ideal dose distribution referred to here is a function representing an ideal dose distribution for obtaining a desired blaze 3 shape, for example, as shown in FIG. The set dose function D (n) representing the set dose distribution referred to here is, for example, by approximating the ideal dose distribution with the minimum dose displacement of the electron beam lithography apparatus as shown in FIG. It is a function that represents the dose distribution obtained and actually set by the electron beam drawing apparatus. The present invention is characterized in that the original set dose distribution of the apparatus is corrected by the dose amount mixed area calculation information 161b. The dose distribution correction calculation information 161c referred to here is, for example, as shown in FIG. It is dose distribution information indicating a dose function after performing a correction calculation described later on the set dose function D (n) based on the dose amount mixed region calculation information 161b. 12 to 14 are modeled, and the dose function (dose distribution) represents a dose distribution for obtaining the same blazed shape, and the dose function (dose distribution) is The surface on which the blaze 3 of the substrate is formed is a flat surface, and the dose amount and the dose position (temporary coordinates set for illustrating the dose amount distribution) are shown as an example only.

  In the program memory 162, a processing program 163a for performing these processes (more specifically, for example, a series of processes from S101 to S117 in FIGS. 19 to 21 described later), the dose distribution information 161a, a dose amount, and the like. Based on information such as the mixed area calculation information 161b and the dose distribution correction calculation information 161c, the drawing line position to which the dose mixed area MIX is assigned to the inclined portion 3b of the blaze 3 and the formation position of the blaze 3 When the number of projections and depressions in the mixed dose amount region MIX is changed in accordance with the dose distribution correction calculation program 163b (such as FIG. 22 described later in detail). A series of processes from S301 to S313), other processing programs 163c, and the like. The “storage unit” can be configured by the memory 160 of the present embodiment, and the “control unit” can be configured by the program memory 162 and the control unit 170 of the present embodiment.

  The control means according to the present invention controls the drawing of the inclined portion 3b and the side wall portion 3a of the blaze 3 while calculating the dose amount based on the dose distribution. At this time, the control means performs control to adjust the current value of the electron lens based on the drawing position measured by the measuring means to change the focal position of the electron beam according to the drawing position. The position is controlled so as to draw the inclined portion 3b and the side wall portion 3a of the blaze 3 while calculating the dose amount based on the dose distribution.

  The dose distribution information 161a in the memory 160 includes information on the ideal dose distribution and the set dose distribution according to the shapes of the curved surface portion 2a of the base material 2, the inclined portion 3b of the blaze 3, the side wall portion 3a, and the like. Then, the dose distribution correction calculation program 163b performs a calculation for correcting the set dose distribution into a dose distribution (dose distribution correction calculation information 161c) in which a dose amount corresponding to the unevenness of the dose amount mixed region is mixed. . The dose distribution correction calculation program 163b and the control unit 170 can constitute the “calculation means” according to the present invention.

  Furthermore, the control means includes a setting means 181 for setting the ideal dose distribution and a dose amount mixed area (mix_w [%], which will be described later), and a display means 182 capable of displaying, for example, dose information for each line. I will do it.

  In the control means having such a configuration, when the control unit 170 reaches a routine for calculating the dose amount of the dose amount mixed area while executing a predetermined drawing algorithm by the processing program 163a, the control unit 170 executes the dose distribution correction calculation program 163b. In order to calculate the corrected dose distribution for setting the unevenness of the dose amount mixed area according to the drawing position with respect to the original set dose distribution, a certain amount of basic information, that is, the dose distribution The corresponding dose distribution correction calculation information 161c is calculated while referring to the information 161a or the table stored in the dose amount mixed region calculation information 161b, and then the calculated dose distribution correction calculation information 161c is stored in the memory 160. It is stored in a predetermined temporary storage area, and drawing is performed based on the dose distribution correction calculation information 161c. .

  Here, an example of a table stored in the dose mixed region calculation information 161b, specifically, a table related to the dose distribution of the unevenness of the dose mixed region will be described with reference to FIG. FIG. 15 discloses a specific example of the table 161e relating to the dose distribution corresponding to the drawing pattern of the dose amount mixed area in FIG. In the example of FIG. 15, the region 301 is configured with the dose amount 0 for the drawing lines 0 to 13, and the dose amount mixed region MIX is configured with the dose amounts 0 and 100 for the lines 14 to 25. Specifically, the 14th line, the 18th to 19th line, and the 22nd to 24th line constitute a recess with a dose amount of 100. Similarly, the 15-17 line, the 20-21 line, and the 25 line constitute a convex portion with a dose amount of 0. Further, the region 302 of the inclined portion is constituted by the dose amount 100 for the lines 26 to 38, and the dose mixed region MIX is constituted again by the dose amounts 100 and 150 for the lines 39 to 50. . Specifically, the 39 line, the 43-44 line, and the 47-49 line form a recess with a dose amount of 150. Similarly, 40 to 42 lines, 45 to 46 lines, and 50 lines constitute a convex portion with a dose amount of 100. Thereafter, a flat dose amount region and a dose amount mixed region are formed stepwise with a minimum dose displacement 50.

  In this example, for example, one line pitch is 10 nm to 30 nm, the minimum dose amount is 100, and the minimum dose displacement is 50.

  In this way, by using the table in which the dose distribution of the dose amount mixed region is prepared for each line, the correction calculation by the dose distribution correction calculation program 163b and the control unit 170 can be simplified, and the dose amount can be more easily performed. Drawing corresponding to the unevenness of the mixed area can be performed. Note that specific processing steps when the correction calculation is performed by a predetermined program without using such a table will be described later, taking a dose mixed region as shown in FIG. 3A as an example.

<Specific configuration of control system>
Here, as an example, a specific configuration of a control system for performing various processes for linearly drawing each drawing line by approximating a circle with a regular polygon in drawing a circle will be described with reference to FIG.

  As shown in FIG. 16, the control system 300 of the electron beam drawing apparatus according to the present invention is necessary for approximating a regular polygon (including an indefinite polygon) at the time of drawing a circle (according to the radius of the circle). Various data (for example, for a circle with a radius of kmm, each circle such as the division number n by the polygon, the coordinate information of the position of each side / point, the multiple of the number of clocks, and the position in the Z direction) ), And various data necessary for linear approximation when drawing various curves as well as circle drawing, various drawing patterns (rectangle, triangle, polygon, vertical line, horizontal line, diagonal line) A drawing pattern data memory 301 which is a drawing pattern storage means for storing data relating to discs, circles, triangles, arcs, sectors, ellipses, and the like.

  Further, the control system 300 includes a drawing condition calculation unit 310 that calculates a drawing condition based on the drawing pattern data in the drawing pattern data memory 301, and a (2n + 1) line ((n = 0) from the drawing condition calculation unit 310. , 1, 2,..., (2n + 1), but if (n = 1, 2,...), It may be (2n-1). (2n + 1) line drawing condition calculation means 311; (2n + 1) time constant setting circuit 312 for setting a time constant for one line based on line drawing condition calculation means 311; and (2n + 1) line drawing condition calculation means 311 based on A start / end voltage setting circuit 313 for setting a voltage at the electron gun power supply unit 102 regarding the start point and end point of one line, and (2n + 1) line drawing condition calculation means 311 A counter number setting circuit 314 for setting the number of line counters based on it, an enable signal generating circuit 315 for generating an enable signal based on the (2n + 1) line drawing condition calculation means 311, and a deflection signal for outputting odd lines And a deflection signal output circuit 320. Note that the line here refers to each side constituting a polygon.

  Further, the control system 300 is based on the (2n) line drawing condition calculating means 331 and (2n) line drawing condition calculating means 331 for calculating the drawing conditions of (2n) lines, that is, even lines from the drawing condition calculating means 310. A time constant setting circuit 332 for setting a time constant for one line, and (2n) start / end voltage setting for setting a voltage at the electron gun power supply unit 102 regarding the start point and end point of one line based on the line drawing condition calculation means 331 A counter number setting circuit 334 for setting the number of line counters based on the circuit 333, (2n) line drawing condition calculation means 331, and (2n) an enable signal for generating an enable signal based on the line drawing condition calculation means 331 A generation circuit 335, a deflection signal output circuit 340 for outputting an even-line deflection signal, and (2n) lines Based on the image condition calculation means 310, a blanking amplifier 350 that performs blanking when moving to the next contour line, the drawing conditions in the drawing condition calculation means 310, the deflection signal output circuit 320 for odd lines, and the even lines And a switching circuit 360 that switches between odd-numbered line processing and even-numbered line processing based on information from the deflection signal output circuit 340.

  The odd line deflection signal output circuit 320 is a counter that is a counting unit that performs counting processing based on the scanning clock CL1, the odd line count signal CL6 from the counter number setting circuit 314, and the enable signal of the enable signal generation circuit 315. The DA conversion circuit 322 that performs D / A conversion based on the circuit 321, the count timing from the counter circuit 321, and the odd line drawing condition signal CL 3 in the start / end voltage setting circuit 313, and the DA conversion circuit 322 And a smoothing circuit 323 that performs a process of smoothing the analog signal converted in step (a process such as removing a high-frequency component of the deflection signal).

  The even line deflection signal output circuit 340 is a counter that is a counting means that performs a counting process based on the scanning clock CL1, the even line count signal CL7 from the counter number setting circuit 334, and the enable signal of the enable signal generation circuit 335. A DA conversion circuit 342 that performs D / A conversion based on the circuit 341, the count timing from the counter circuit 341, and the even line drawing condition signal CL5 in the start / end voltage setting circuit 333, and the DA conversion circuit 342 And a smoothing circuit 343 that performs a process of smoothing the analog signal converted in step (b).

  It should be noted that each part constituting these control systems 300 can be controlled by the control part 170 shown in FIG. The control system 300 may be configured to form an X deflection control system and a Y deflection control system, respectively.

  The “calculation unit” can be configured by the control system 300 including the drawing pattern data memory 310 and the drawing condition calculation unit 311 according to the present embodiment. This "calculation means" is a function for computing at least two positions corresponding to a distance corresponding to an integral multiple of the minimum conversion time (minimum time resolution) of the DA converter on the scanned scanning line. Have In the present embodiment, the control unit 170 performs control so that each position calculated by the calculation unit is scanned almost linearly by the electron beam. Similarly, in the “arithmetic means” of another aspect of the present invention, the time is an integral multiple of the minimum time resolution defined by the number of clocks of the DA converter on the scanning line scanned in a substantially circular shape. It has a function of calculating each vertex position of a polygon having a corresponding distance as one side. Similarly, the control means scans between the positions calculated by the calculation means almost linearly by the electron beam.

  The control system 300 having the above configuration generally operates as follows. That is, when the drawing condition calculation unit 310 acquires information necessary for scanning (drawing) by linear approximation from the drawing pattern data memory 301, a calculation process of predetermined drawing conditions is performed. Information about the first side and odd-numbered lines among the sides when approximated to each side is (2n + 1) to the line drawing condition calculation means 311. Information about the next side and even-numbered lines is (2n). Each is transmitted to the line drawing condition calculation means 331.

  Thereby, for example, the (2n + 1) line drawing condition calculation means 311 generates drawing conditions regarding odd lines, and from the deflection signal output circuit 320 based on the scanning clock CL1 and the generated odd line drawing condition generation signal CL2. An odd line deflection signal CL9 is output.

  On the other hand, for example, the (2n) line drawing condition calculation unit 331 generates drawing conditions regarding even lines, and outputs an even number from the deflection signal output circuit 340 based on the scanning clock CL1 and the generated even line drawing condition generation signal CL4. The line deflection signal CL10 is output.

  The outputs of the odd line deflection signal CL9 and the even line deflection signal CL10 are alternately switched by the switching circuit 360 under the drawing condition calculation means 310. Therefore, when one side is approximated to a regular polygon and each side is calculated, one side, odd-numbered side is drawn, the next side, even-numbered side is drawn, Further, each side is alternately drawn (scanned) linearly, such that the next side and the odd-numbered side are drawn.

  Then, when drawing for a certain circle is completed, the drawing condition calculation unit 310 transmits a message to that effect to the blanking amplifier 350, and performs processing for prompting drawing of another next circle. In this way, drawing that approximates each circle with a polygon is performed.

(About the shape of the substrate)
Next, description will be made on the fact that a blaze inclined surface after development is formed smoothly by drawing a dose mixed region on the blaze inclined portion.

  FIGS. 13 and 17 show a set dose distribution in conventional electron beam drawing, and a cross-sectional shape of the substrate after drawing / development measured by a scanning probe microscope, while FIG. 14 and FIG. 18 shows a set dose distribution in electron beam writing according to the present invention and the cross-sectional shape of the substrate after drawing / development measured by a scanning probe microscope. The dose distributions shown in FIGS. 13 and 14 correspond to the same blazed shape, and these dose distributions show a case where one surface on which the blazed 3 of the diffractive structure is formed is a plane, and the dose amount thereof. In addition, the dose position is merely an example.

  As shown in FIGS. 17 and 18, the blazes 3 ′ and 3 have side wall portions 3 ′ a and 3 a and inclined portions 3 ′ b and 3 b, and the side wall portions 3 ′ a and 3 a and the inclined portion 3 are provided. Grooves 3'c and 3c are provided between 'b and 3b. In these drawings, the horizontal axis indicates the position along the cross-sectional direction of the blaze of the diffraction grating structure (unit: μm), and the vertical axis indicates the position along the height direction of the blaze of the diffraction grating structure. (Unit: nm).

  As shown in FIG. 13, in conventional electron beam drawing, a set dose distribution obtained by approximating an ideal dose distribution with the minimum dose resolution (minimum dose) of the apparatus, that is, a set dose function D (n). The substrate is drawn based on the above. Then, the shape of the side wall portion 3'a and the inclined portion 3'b of the blaze 3 'obtained after the drawing / development is such that the minimum dose of the electron beam drawing apparatus is in the inclined portion 3'b as shown in FIG. A plurality of steps due to the resolution are formed.

  On the other hand, as shown in FIG. 14, in the electron beam drawing according to the present invention, a correction calculation to be described later based on a table stored in the dose mixed area calculation information 161b for the set dose function D (n). The base material is drawn based on the dose distribution correction calculation information 161c after performing the above. At this time, the flat dose amount region and the dose amount mixed region are drawn on the inclined portion 3 b of the blaze 3. The dose mixed region is composed of a plurality of irregularities. The shape of the side wall portion 3a and the inclined portion 3b of the blaze 3 obtained after the drawing / development is such that the inclined portion 3b is an inclined portion 3 ′ of the blaze 3 ′ shown in FIG. 17, as shown in FIG. Compared with b, it is formed gently.

  Here, it will be described in detail that the inclined portion 3b shown in FIG. 18 is gently formed as compared with the 3 ′ inclined portion 3′b shown in FIG.

  In general, when an electron beam is irradiated onto a substrate, there is a considerable amount of electron beam diffusion inside the substrate, and the area as if it was drawn with an electron beam has an effect. Will be. In the present invention, this is called “proximity effect” by the electron beam. By the way, in the present invention, even when drawing is performed on the inclined portion 3b of the blaze 3 by the electron beam based on the dose amount mixed region, the electron beam is diffused in the inclined portion 3b of the blaze 3, and the first dose amount is obtained. The “proximity effect” is generated by the electron beam between the scanned region and the region scanned with the second dose. Therefore, when this is developed, both areas do not actually have a concavo-convex shape. Further, as described above, the scan width based on the first dose amount and the scan width based on the second dose amount that are scanned in the dose amount mixed region are each configured to be smaller than the diameter of the electron beam that draws the region. For this reason, when this is drawn with an electron beam, a portion to be drawn a plurality of times (for example, 2 to 3 times) is generated in both areas due to overlapping of the drawing areas by the electron beam. The region drawn by the dose mixed region results in an inclined surface having an intermediate height.

  That is, as a result, the step between the regions corresponding to the adjacent flat dose amounts of the inclined portion 3b of the blaze 3 is formed by scanning the intermediate-level inclined surface by the dose amount mixed region. As compared with the case where the inclined portion 3 ′ b of the conventional blaze 3 ′ has a step, a more gentle inclined surface is formed.

  As described above, when the duty ratio of the first dose amount portion constituting the dose amount mixed region with respect to the mixed region is decreased as the height of the inclined portion 3b is decreased, it becomes more gentle. An inclined surface can be formed.

(Processing procedure)
Next, an example of a processing procedure in the case of using an electron beam drawing apparatus to form a blaze concentrically on a base material for producing a mold for forming an aspherical optical lens, and by approximating the circle with a polygon. Will be described with reference to the flowcharts shown in FIGS.

  First, concentric marks are processed at the same time when an aspheric surface is processed by SPDT (Single Point Diamond Turning) in a base material (original) (step, hereinafter “S” 101). At this time, it is preferable that a shape having a detection accuracy of, for example, ± 1 μm is formed with an optical microscope.

  Next, alignment marks are attached to, for example, three locations by FIB (Focused Ion Beam) (S102). Here, the cross-shaped alignment mark preferably has a detection accuracy within ± 20 nm in the electron beam drawing apparatus.

  Further, the relative position of the alignment mark to the concentric circle mark is observed and measured with an optical microscope, and the position of the alignment mark with respect to the center of the aspherical structure is measured and recorded in a database (DB) (or memory (hereinafter the same)). (S103). The measurement accuracy is preferably within ± 1 μm, and the positions of the three alignment marks, x1y1, x2y2, and x3y3, which are the center reference, are registered in the database (DB).

  Further, the height of each part of the base material formed by applying a resist to the original mold and baking and coating with a resin and the position (Xn, Yn, Zn) of the alignment mark are measured (S104). Here, the base material corrected by the center reference: the position table Tbl1 (OX, OY, OZ) and the alignment mark: OA (Xn, Yn, Zn) (all 3 * 3 matrix) are registered in the database (DB). .

  Next, in order to detect the height of the focal position, various other preparatory processes such as aligning the position of the measurement beam of the second optical system and focusing the beam of the electron beam are performed (S105).

  At this time, the measurement beam of the second optical system is projected onto a needle-shaped (50 nm level) calibrator for EB (electron beam) focus mounted on the stage, and in the SEM (Scanning Electron Microscope) mode of the electron beam drawing apparatus. Observe and focus.

  Next, the substrate is set in the electron beam drawing apparatus, the alignment mark is read (XXn, YYn, ZZn), the coordinate transformation matrix Ma is calculated, and the position of each part of the substrate in the electron beam drawing apparatus is obtained (S106). ). At this time, each value as shown in S106 is registered in the database (DB) in the electron beam drawing apparatus.

  Further, an optimum field position is determined from the shape of the substrate (S107). Note that the fields are distributed in concentric fan shapes. Also, the fields are slightly overlapped. Further, a field that does not cover the first ring zone in the center is not allocated.

  Then, for each field, the connection address of the adjacent field is calculated (S108). This calculation is performed as a plane. Note that one line segment of the polygon is stored in the same field. Here, the “polygon” means at least one drawing line when a circle drawing is approximated by a predetermined n-gon as described in the item of the control system.

  Next, the depth of focus area is segmented for the target field. The same depth of focus area is divided so that the same line falls within the same section, and the center of the field is set to the height center of the depth of focus section (S109). Here, the height within 50 μm is divided into about one to several places as the same focal depth range.

  Next, for the target field, the beam deflection amount is calculated by the conversion matrix (Xc, Yc) of the (x, y) address within the same focal depth region (S110). Xc and Yc are as shown in the equation (16). Here, Wd is a work distance, and d is a Z direction deviation from the center of the corresponding depth of focus section.

  Further, for the target field, the next connecting address is converted (S111). Here, the connection position calculated in S108 is converted using Equation (16) of S110.

  Then, with respect to the target field, the XYZ stage is moved to the center, and the height is set to the focus position of EB (electron beam) (S112). That is, it is set at the center of the field on the XYZ stage. Further, while detecting the signal of the measuring device 80, the XYZ stage is moved and the height position is read.

  Further, the target field is adjusted to the focus position of the electron beam (EB) at the height center of the outermost (m-th) same focal depth region (S113).

  Next, the dose amount of the outermost (n-th) line and the coordinates of the start point and end point of the polygon are calculated for the target same focal depth region. Note that the start (start point) and end (end point) are connection points with adjacent fields (S114). At this time, the start point and end point are integers. In general, the dose is expressed by multiplying the maximum dose determined by the radial position (incident angle) and the coefficient determined by the position of the grating by the maximum dose.

  Thereafter, S113 to S115 are performed a prescribed number of times (S115).

  Here, the determination method of the dose amount of each drawing line in the above-described S113 to S115 according to the present invention will be described using the flowchart shown in FIG. In the following description, as shown in FIG. 3A, the inclined portion 3b has a constant dose amount between the scanning region at the first dose amount and the scanning region at the second dose amount. A case where a mixed region is formed will be described.

  Here, various parameters are defined as follows.

Ideal dose function: f (n)
Dose minimum displacement: min_dose
Drawing dose setting value: Dn (integer)
Rounding value of n: Round (n)
First, the setting unit 181 inputs w [%] of the dose amount mixed region area: mix_w [%] (S301). Note that “w [%]” here refers to the value of m / M in FIG. 23, and “dose amount mixed region: mix_w [%]” herein refers to, for example, U1 + U2 + U3 in FIG. Specifically, as shown in FIG. 23, when the ideal dose function f (n) and the set dose function D (n) are overlapped at the same drawing position, the ideal dose function f (n) When a horizontal line is drawn from a point corresponding to the distance m from the intersection point P with the set dose function D (n), and a vertical line is further drawn from a point Q where the ideal dose function f (n) intersects, the set dose function D ( n) indicates a region between a point R intersecting with n) and a start point O of each dose setting value.

  By defining the dose mixed region: mix_w [%] in this way, the range in which the dose mixed region is provided can be determined according to the gradient of the ideal dose function f (n). Even when the angle of the surface changes in accordance with the drawing position, it is possible to appropriately cope with this.

  When the control unit 170 reaches a routine for calculating the dose amount in the dose amount mixed area while executing a predetermined drawing algorithm by the processing program 163a, the control unit 170 executes the dose distribution correction calculation program 163b, and sets the dose distribution set by the apparatus. Then, a corrected dose distribution for setting a mixed dose amount region corresponding to the drawing position is calculated.

  Specifically, first, a drawing position (for example, U1) based on one step of unevenness is set to n = 0 to k (k: outermost drawing position), a drawing position n = 0, and a dose displacement is 1 above and below. And an initial setting value N = 1 defined by -1 (S302), a value obtained by dividing the ideal dose function f (n) at the drawing position n by the minimum dose displacement (minimum dose resolution) and the decimal point of the value A difference R (x) from a value obtained by rounding off the following is calculated (S303).

R (x) = f (n) / min_dose−Round (f (n) / min_dose) (Equation 1)
Next, w / 100> 1- (0.5-R (x) × 2) (Formula 2)
Is determined (S304), and if YES is determined, it is next determined whether N = 1 (S307).

Naturally, since the initial setting value N = 1, the dose setting value (setting dose amount) Dn at the drawing position n = 0 is
Dn = Round (f (n) / min_dose) is set (S309).

If it is determined No in S304, then
mix_w / 100 <(0.5−R (x) × 2)
Is determined (S305), and if YES is determined, then N = 1 is determined (S308).
Naturally, since the initial setting value N = 1, the dose setting value (setting dose amount) Dn at the drawing position n = 0 is
Dn = Round (f (n) / min_dose) −1 is set (S310).

  If it is determined No in S305, the dose setting value (set dose amount) Dn at the drawing position n is set to Dn = Round (f (n) / min_dose) (S306).

  Subsequent to S309 or S310, the dose setting value Dn at the drawing position n is stored in the memory 160 as dose distribution correction calculation information 161c (S311).

  Next, n = k is determined (S312).

  Naturally, since n = 0, it is determined No, and n = n + 1 and N = −1 are set (S313).

  Thereafter, after setting n = n + 1 and N = −N (the sign of N is inverted every time it is added to n), S303 to S312 are repeated a predetermined number of times until it is determined that n = k in S312. These are corrections for the drawing lines in the field.

  Subsequently, the above flow is repeated at the drawing position based on the subsequent uneven dose amount, and drawing is performed based on the determined dose setting value Dn. For example, the unevenness of the dose amount mixed region as shown in FIG. Can be drawn based on.

  Then, returning to the flow of FIG. 21, preparation for moving the XYZ stage and drawing the next field is performed (S116). At this time, the field number, time, temperature, etc. are registered in the database (DB).

  Thereafter, by performing S109 to S116 a prescribed number of times (S117), the inclined portion 3b of each blaze 3 can be formed with a dose amount distribution as shown in FIG.

Note that, for example, as shown in FIG. 3B, the distance between the projections and depressions in the dose amount mixed region is configured to increase as the height of the inclined portion 3b decreases. For example, by using a table in which a dose distribution as shown in FIG. 15 is prepared for each line, a correction operation can be easily performed and drawn.
(Another embodiment of the mixed dose region)
Next, another embodiment of the present invention will be described with reference to FIGS. In the following description, description of the configuration substantially the same as that of the above-described embodiment will be omitted, and only different portions will be described.

  In the above-mentioned embodiment, the case where the area | region drawn by the fixed dose amount and the area | region drawn based on the unevenness | corrugation of a dose amount mixed area | region are illustrated in the cross-sectional direction (inclination direction) of the inclination part 3b of the blaze 3 is illustrated. However, in the present embodiment, a case will be described in which drawing is performed based on the unevenness of the dose mixed region in the electron beam scanning direction (the arrow direction in FIG. 1B).

  In other words, the present embodiment is characterized in that a blanking section is provided for drawing a drawing line (line in the scanning direction) scanned by an electron beam based on the concave portion of the dose mixed region, and the line drawing portion is defined as the dose line. The drawing is based on the convex portion of the quantity mixed region.

  FIG. 24 schematically shows a dose distribution for drawing an inclined portion of a blaze formed by providing a blanking section of the present embodiment.

  As shown in FIG. 24, the dose distribution 200 for drawing the slant portion of the blaze according to the present embodiment includes drawing lines drawn with the first dose amount 201 and the second dose amount 202 in the cross-sectional direction. (FIG. 24B), but the first dose amount and the second dose amount in the electron beam scanning direction (vertical direction in the figure) (where the second dose amount> the first dose amount, the second dose amount). The dose amount mixed region MIX in which the dose amount-first dose amount = minimum dose displacement is mixed is the blanking interval BK corresponding to the recess (drawing with the second dose amount) and the other intervals (first (Drawing with a dose amount). Note that the hatched area in FIG. 6A corresponds to the bottom surfaces of the recesses BJ1 to BJ3 in FIG.

  As described above, the widths of the concave portions and the convex portions of the dose mixed region MIX are configured to be smaller than the diameter of the electron beam to be drawn based on the concave and convex portions.

  As described above, even when the uneven portion of the dose amount mixed region is formed in the dose distribution in the scanning direction of the electron beam, in the same manner as in the above-described embodiment, when writing with the electron beam corresponding to this, Electron beam diffusion occurs in the slanted portion, and a “proximity effect” is produced by the electron beam between the region drawn based on each concave portion and the region drawn based on the convex portion in the dose mixed region. Therefore, when this is developed, it does not actually have a strict binary shape. Further, as described above, the width of the region drawn based on each concave portion of the dose mixed region and the region drawn based on the convex portion are each configured to be smaller than the diameter of the electron beam that draws the region. Therefore, when this is drawn with an electron beam, a portion to be drawn a plurality of times (for example, 2 to 3 times) is generated due to overlapping of drawing regions by the electron beam. It becomes an inclined surface having a certain height.

  As a result, the level difference between the region drawn with the adjacent first dose amount and the region drawn with the second dose amount of the blaze formed on the substrate has a height intermediate between these. The area drawn based on the mixed quantity area constitutes a more gentle inclined surface as compared with the step between the inclined parts of the conventional blaze.

  As described above, when the duty ratio of the convex portion with respect to the concave and convex portion of the dose mixed region MIX is reduced as the height of the inclined portion 200 decreases, it is based on the convex portion of the dose mixed region. Since the height of the drawn area can be lowered stepwise, a more gentle inclined surface can be formed.

<Control system configuration with blanking section>
Next, a specific control system configuration for performing drawing with the first dose amount and the second dose amount according to each region of the drawing line in order to form the blanking section as described above. This will be described with reference to FIG.

  The control system 700 in the present embodiment is incorporated, for example, in the control circuit 100 of FIG. 5 in the previous embodiment, and periodically performs line drawing when performing line drawing based on the dose amount mixed region of the dose distribution. Two modes (for example, a first mode in which line drawing is performed with a first dose amount and a blanking operation in order to provide a ranking) (drawing based on irregularities at predetermined intervals of a dose distribution in a dose amount mixed region) Mode switching control using a second mode in which line drawing is performed with a dose amount of 2), as shown in FIG. 25, in order to scan the surface of the substrate with an electron beam. A scan DAC 702 that is a DA converter that converts a digital signal into an analog signal based on a predetermined clock (signal), and an analog signal converted by the scan DAC 702 Accordingly, a beam deflection signal output circuit 703 for generating and outputting a beam deflection signal, a counter 711 for counting (counting) the clock (signal), and a first register 713 storing information on the dose pattern period n1. When the blanking period for forming the blanking interval is n3-n2 (where n1> n3, n3> n2 as indicated by reference numeral 720), the second register 715 storing information on n2 , N3, the first register 717 capable of resetting the counter 711 by comparing the count value counted by the counter 711 with the information stored in the first register 713. And the count value counted by the counter 711 and the information stored in the second register 715 are compared. A comparator 714, a third comparator 716 that compares the count value counted by the counter 711 and the information stored in the third register 717, a comparison result compared by the second comparator 714, A logic gate 718 that calculates a logical product of the comparison results compared by the three comparators 717, and blanking that is blanked off (first mode) for a predetermined period based on the result output from the logic gate 718. And a blanking off signal output circuit 719 for generating and outputting an off signal.

  The above-described scan DAC 702 and beam deflection signal output circuit 703 can constitute a “beam deflection control system”, which includes a counter 711, a first comparator 712, a first register 713, a second comparator 714, a second register 715, The third comparator 716, the third register 717, the logic gate 718, and the blanking off output circuit 719 can constitute a “blanking control system as mode switching means”.

  In the control system 700 having the above-described configuration, a specific drawing line (drawing line) is drawn by the deflection signal from the beam deflection signal output circuit 703 based on the clock.

  At this time, when the count value of n2 satisfying n3> n2 is reached based on the clock and the counter 711 outputs the count value, the second comparator 714 changes the output signal from “L” level to “H” level, for example, An “H” level signal is output and input to one input of the logic gate 718.

  Next, when n3> n2 is reached based on the clock and the counter 711 outputs the count value, the third comparator 716 changes the output signal from “L” level to “H” level, for example, An “H” level signal is output and input to the other input of the logic gate 718.

  During this time, if one input of the logic gate 718 is at “L” level and the other input is at “L” level, or one input is at “H” level and the other input is at “L” level, the logic gate Since 718 outputs “H”, “blanking on (second mode period)” is set, and line drawing is performed with the second dose.

  On the other hand, when one input of the logic gate 718 is at “H” level and the other input is at “H” level, or one input is at “L” level and the other input is at “H” level, Since 718 outputs “L”, “Blanking is OFF” during this period, and line drawing is performed with the first dose.

  On the other hand, when the counter value 711 reaches the count value n1, where n1> n3> n2 based on the clock, and the counter 711 outputs the count value, the first comparator 712 outputs a signal and resets the counter 711.

  In this way, the above “blanking off” and “blanking on” are repeated every n1 cycles. For example, as shown in FIG. A binary pattern in the drawing line direction can be formed by the area drawn with the dose amount and the area drawn with the second dose amount.

In the present embodiment, the blanking interval BK is constant. For example, the blanking interval may be changed for each drawing line.
(Third embodiment of a dose mixed region)
Next, a third embodiment of the dose mixed region according to the present invention will be described with reference to FIG. In the following, description of the configuration substantially the same as that of each of the above-described embodiments will be omitted, and only different parts will be described.

  In the first embodiment, an example in which a region drawn with a constant dose amount in the cross-sectional direction (inclination direction) of the inclined portion 3b of the blaze 3 and a region drawn based on the unevenness of the dose amount mixed region are illustrated. In addition, in the second embodiment, the case where the region to be drawn based on the unevenness of the dose mixed region is formed in the scanning direction of the electron beam is exemplified, but in the present embodiment, these are combined, An area drawn with a constant dose amount in the cross-sectional direction (inclination direction) of the blaze inclined portion and an area drawn based on the unevenness of the dose amount mixed region are formed, and the convex portion of this dose amount mixed region A case will be described in which a region to be drawn based on the unevenness of the dose distribution is formed also in the electron beam scanning direction in the region to be drawn based on the above.

  More specifically, an area drawn with a constant dose amount in the cross-sectional direction (inclination direction) of the inclined portion of the blaze and an area drawn based on the unevenness of the dose amount mixed area are formed, and this dose amount is further formed. In the area drawn based on the convex portion of the mixed area, a blanking section is provided for drawing a drawing line (line in the scanning direction) scanned by the electron beam, and this blanking section is set in the dose amount mixed area. The region drawn based on the concave portion in the region drawn based on the convex portion is set as the region drawn, and the line drawing portion is set as the region drawn based on the convex portion of the dose amount mixed region.

  Specifically, as shown in FIG. 26, the dose distribution 400 for drawing the inclined portion of the blaze according to the present embodiment draws the inclined portion 3b of the blaze 3 according to the first embodiment when viewed from the cross-sectional direction. There is a drawing line that is not particularly different from the dose distribution.

  However, when viewed from the electron beam scanning direction, the first dose amount and the second dose amount in the electron beam scanning direction (vertical direction in the drawing) in the dose amount mixed region MIX of the inclined portion dose distribution 400 (see FIG. However, the region drawn with the second dose amount> the first dose amount, the second dose amount-the first dose amount = the minimum dose unit) is a dose amount mixed region in the cross-sectional direction of the inclined portion of the blaze. It is formed in the area | region drawn based on this convex part.

  On the other hand, in the dose distribution of other regions drawn with a constant dose amount, the first dose amount 401 and the second dose amount 402 are formed as usual, and in the drawing in the cross-sectional direction of the inclined portion, An inclined surface is formed in a staircase shape.

  Similarly, a dose amount mixed region MIX and a region having a constant dose amount are also formed for the dose distribution 400 of the inclined portion of the blaze at other positions.

  As described above, the width of the region drawn by each concave portion and the region drawn by the convex portion of the dose mixed region is configured to be smaller than the diameter of the electron beam drawn based on the concave and convex portions. Shall.

  As described above, even when the region to be drawn is formed in the scanning direction of the electron beam based on the uneven portion of the dose amount mixed region, this is the same as the base material in the first embodiment and the second embodiment. In the case of drawing with an electron beam, the electron beam is diffused in the slanted portion of the blaze, and this electron beam is drawn between the region drawn based on each concave portion and the region drawn based on the convex portion. As a result, the “proximity effect” is generated, and when this is developed, it does not have a strict binary shape. Further, as described above, the width of the region drawn based on each concave portion of the dose mixed region and the region drawn based on the convex portion are each configured to be smaller than the diameter of the electron beam that draws the region. Therefore, when this is drawn by an electron beam, a portion drawn by a plurality of times (for example, 2 to 3 times) is generated due to the overlap of the drawing area by the electron beam. It becomes an inclined surface having a certain height.

  As a result, the step between adjacent regions drawn with a certain dose amount is a step between the inclined portions of the conventional blaze due to the region drawn based on the mixed dose region having an intermediate height. Compared to the above, a gentler inclined surface is formed.

As described above, when the duty ratio of the convex portion with respect to the concave and convex portion of the dose distribution region in the dose amount mixed region is reduced as it goes to the side where the height of the inclined portion decreases, the drawing is performed based on the convex portion. Since the height of the region can be lowered stepwise, a more gentle inclined surface can be configured.
(Fourth Embodiment of Dose Amount Mixed Area)
In the present embodiment, based on FIG. 27, blanking sections of various patterns are provided in the drawing line in the scanning direction of the electron beam in the region drawn based on the convex portion of the dose amount mixed region of the inclined portion of the blaze. The case will be described.

  For example, in the region 801 drawn based on the convex portions of the dose amount mixed region shown in FIG. 27A, the blanking section 801a is configured to be positioned in an oblique direction.

  In the region 802 drawn based on the projections of the dose mixed region shown in FIG. 27B, the blanking sections 802a and 802a are arranged in a staggered manner between adjacent drawing lines and are not adjacent to each other. It is configured as follows.

  In the region 803 drawn based on the convex portion of the dose amount mixed region shown in FIG. 27C, the length of 803b drawn based on the convex portion differs depending on the location.

  In the region 804 drawn based on the convex portion of the dose mixed region shown in FIG. 27D, when the blanking section 804a is formed to be inclined, the inclination direction is changed with a certain line group. It is configured.

  An area 805 drawn based on the projections of the dose amount mixed area shown in FIG. 27E is configured to change the position of the blanking section 805a for each of a plurality of line groups.

  Even in the configuration in which the blanking section is provided in the various drawing patterns as described above, when this is drawn by an electron beam, the electron beam is diffused in the blaze inclined portion as in the above-described embodiments. Since the "proximity effect" due to this electron beam occurs between the region drawn based on each concave portion and the region drawn based on the convex portion constituting this, when this is developed, It is not an exact binary shape. Further, as described above, the width of the region drawn based on each concave portion and the region drawn based on the convex portion of the dose mixed region is configured to be smaller than the diameter of the electron beam that draws the region. Therefore, when this is drawn by an electron beam, a portion drawn by a plurality of times (for example, 2 to 3 times) is generated due to the overlap of the drawing area by the electron beam. It becomes an inclined surface having a certain height.

As a result, the level difference between the areas drawn with a constant dose amount adjacent to the blaze is compared with the conventional level difference due to the area drawn based on the dose amount mixed area having an intermediate height. Therefore, a gentler inclined surface is formed.
(Mold making method)
Next, a method for producing a mold according to the present invention will be described with reference to FIGS. In addition, the metal mold | die which concerns on this invention is for manufacturing optical elements, such as an optical lens, by injection molding, for example.

  First, a prototype 500 in which, for example, the optical surface shape of an optical lens is formed by machining (FIG. 28A).

  Next, a resist RE such as a thermosetting resin is applied to the surface of the prototype 500 by spin coating or the like, and prebaked or the like to cover the resin layer (FIG. 28B).

  Then, for example, a blazed diffraction grating structure of a binary pattern is drawn on the resin layer covering the prototype 500 using the electron beam drawing apparatus according to the present invention (FIG. 28C).

  Resin (resist) layer development process (removing irradiated part by using different solubility in developing solution between electron beam irradiated part and non-irradiated part, or adhesion weakened by cohesive failure by electron beam irradiation The portion is removed using suction or a release layer) to obtain a diffraction grating structure as shown in FIG. 28D (development process).

  Next, the diffraction grating structure is evaluated by SEM observation or a film thickness measuring instrument, and the diffraction grating structure is prepared by an etching process such as dry etching.

  When the D portion of the diffraction grating structure 502 is enlarged, the diffraction grating structure is formed by a plurality of blazes composed of the inclined portions 502b and the side wall portions 502a. In this blaze, the angle of the diffraction grating surface becomes steep as it goes to the periphery, so that the dose mixed region of the dose distribution may be changed according to the change in the angle of the diffraction grating surface.

  Further, a surface treatment is performed on the master mold 500 covered with the resin layer having the diffraction grating structure, and then, as shown in FIG. 29A, for example, after the mold electroforming pretreatment, the electroforming treatment is performed, and FIG. As shown to B), the process which peels the original mold 500 and the metal mold | die 504 is performed. Then, a surface treatment is performed on the peeled mold 504 (mold surface treatment process).

  When a molded product is created by injection molding using the mold 504 (FIG. 29C), a diffraction grating structure 511 composed of a plurality of blazes is formed on the injection molded product 510, and the C portion is shown enlarged. A blaze is formed in which one pitch of the diffraction grating is composed of the side wall portion 512a and the inclined portion 512b.

  According to this embodiment, when an optical element (for example, an optical lens) is manufactured, first, when a diffraction grating is drawn on a substrate by an electron beam drawing apparatus, the first dose amount is set on the inclined portion of the blaze. A dose amount mixed region composed of a region to be drawn and a region to be drawn with the second dose amount is drawn, and after performing a predetermined surface treatment and the like, an etching process is performed by dry etching or the like The die is obtained by electroforming, and the diffraction grating formed on the surface of the base material is transferred to the die, and the optical element is injection-molded using this die. Therefore, the cost for manufacturing the optical element can be reduced.

  In each of the above-described embodiments, the procedure for drawing the blaze sloped portion and the side wall portion and the drawing based on the uneven portion of the dose amount mixed region by a series of scans has been described. First, after drawing the blaze, the drawing based on the concavo-convex portion of the dose amount mixed region may be performed.

  In addition, the apparatus is not limited to the electron beam drawing apparatus described above, and may be an apparatus configured to be capable of multiple drawing independently by a plurality of electron beams.

  Further, the processing program used in the electron beam drawing apparatus of each of the above-described embodiments, the processing to be executed, the data in the memory (various tables, etc.) or all the units may be recorded on an information recording medium. . As the information recording medium, for example, a semiconductor memory such as a ROM, a RAM, a flash memory, and an integrated circuit may be used. Further, the information may be recorded on another medium such as a hard disk.

It is a figure which shows one example of a drawing pattern, and the drawing shape of the detail. It is a figure for demonstrating in detail the drawing pattern of FIG. It is explanatory drawing which shows the dose distribution which draws the inclination part of a blaze. It is explanatory drawing which shows in detail the dose amount mixing area | region of the dose distribution which draws an inclination part. 1 is a diagram showing an overall configuration of an electron beam drawing apparatus according to the present invention. It is a figure which shows the structure of the apparatus which measures the base material on the stage of an electron beam drawing apparatus. It is a characteristic view which shows the correlation with the signal output corresponding to detected light intensity, and the height of a base material. It is a figure which shows the optical element shape base material used by embodiment. It is a figure explaining the focal depth of the electron beam irradiated. It is a figure which shows the base material divided into the some field (drawing unit) like a model. It is a functional block diagram of the control system of the electron beam drawing apparatus which concerns on this invention. It is explanatory drawing for demonstrating the ideal dose function showing the ideal dose distribution for obtaining a desired blaze shape. It is explanatory drawing for demonstrating the setting dose function showing the dose distribution set in the conventional electron beam drawing apparatus in order to obtain a desired blaze shape. It is explanatory drawing for demonstrating the setting dose function showing the dose distribution set in the electron beam drawing apparatus which concerns on this invention in order to obtain a desired blaze shape. It is explanatory drawing which shows an example of dose amount distribution for forming a dose mixed inclination part. It is a control system block diagram of the electron beam drawing apparatus which concerns on this invention. It is a figure which shows the cross-sectional shape after image development of the base material drawn with the conventional electron beam drawing apparatus. It is a figure which shows the cross-sectional shape after image development of the base material drawn with the electron beam drawing apparatus which concerns on this invention. It is a flowchart which shows an example of the process sequence in the case of using a base material which produces the formation type | mold of an aspherical optical lens using an electron beam drawing apparatus, forming several blazes concentrically and making it a diffraction structure. It is a flowchart following FIG. It is a flowchart following FIG. It is a flowchart which shows an example of the process sequence in the case of drawing on a base material based on a dose amount mixing area | region with the electron beam drawing apparatus which concerns on this invention. It is explanatory drawing for demonstrating the method of determining the formation range of a dose amount mixing area | region. It is a figure which shows the dose distribution which draws the inclination part of the blaze formed by providing a blanking area in model. It is a functional block diagram which shows the detailed structure of the control system for performing the line drawing which provided the blanking area in the electron beam drawing apparatus which concerns on this invention. It is explanatory drawing which shows in detail the example of 1 structure which sets a dose amount mixing area | region to the dose distribution which draws the inclination part of the blaze which concerns on this invention. It is explanatory drawing which shows in detail the various structural examples which set the dose amount mixing area | region which draws the inclination part of the blaze which concerns on this invention. It is a figure explaining the manufacturing method of the metal mold | die which concerns on this invention. It is a figure explaining the manufacturing method of the metal mold | die which concerns on this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Electron beam drawing apparatus 2 Base material 2a Curved surface part 3 Blaze 3a Side wall part 3b Inclination part 10 Lens tube 12 Electron gun 14 Slit 16 Electron lens 18 Aperture 20 Deflector 22 Correction coil 30 XYZ stage 40 Loader 50 Stage drive means 60 Loader Drive device 70 Vacuum exhaust device 80 Measuring device 82 First laser length measuring device 84 First light receiving portion 86 Second laser length measuring device 88 Second light receiving portion 100 Control circuit 110 Coil control portion 112a Molding deflection portion 112b Sub Deflection unit 112c Main deflection unit 116 Position error correction circuit 118 Electric field control circuit 120 Pattern generation circuit 130 First laser drive control circuit 132 Second laser drive control circuit 134 First laser output control circuit 136 Second laser output control Circuit 140 First measurement calculation unit 42 second measurement calculating section 150 stage control circuit 152 loader control circuit 154 mechanism control circuit 156 evacuation control circuit 158 measurement information input section 160 memory 162 a program memory 170 the control unit 300 control system

Claims (10)

When drawing on a substrate by scanning with irradiation with an electron beam,
A first step of drawing by scanning the electron beam with a first dose;
A second step of drawing by scanning the electron beam with a second dose amount;
A third step of providing a region in which a portion drawn with the first dose amount and a portion drawn with the second dose amount are mixed;
An electron beam drawing method comprising: The difference between the first dose amount and the second dose amount is a dose amount based on a minimum clock of a D / A converter for driving an electron gun of an electron beam lithography apparatus that irradiates the electron beam. The electron beam drawing method according to claim 1, wherein the minimum adjustment unit (minimum displacement) is set. In the third step, a portion is provided in which the region drawn with the first dose amount and the region drawn with the second dose amount are periodically and repeatedly provided in the electron beam scanning direction. The electron beam drawing method according to claim 1 or 2, wherein 4. The electron beam drawing method according to claim 3, wherein the drawing is performed by providing an area to be drawn with the first dose amount at a position that substantially coincides between adjacent scanning lines. The electron beam drawing method according to claim 3, wherein the drawing is performed by providing the region to be drawn with the first dose amount at different positions between adjacent scanning lines. The electron beam drawing method according to claim 3, wherein the drawing is performed by providing a region to be drawn with the first dose amount in a staggered position between adjacent scanning lines. Using the electron beam drawing method according to any one of claims 1 to 6,
The manufacturing method of the metal mold | die for shaping | molding characterized by including the process of developing the base material drawn with the electron beam, and performing electroforming with the developed base material. 8. The method for producing a molding die according to claim 7, wherein electroforming is performed on the developed base material subjected to the etching treatment. A mold manufactured by the manufacturing method according to claim 7 or 8. An optical element formed by the mold according to claim 9.

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