JP2005144531A - Shape creation method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a shape creation method which makes it possible to obtain a shape of higher accuracy through electron beams lithography. <P>SOLUTION: Since post baking treatment is performed, a rupture occurs in a position of ≤20% of the maximum height in a three-dimensional shape of resist after development and the stress within the resist is released, the deformation of the resist is therefore suppressed and the highly accurate three-dimensional shape can be created. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a shape creation method, and more particularly to a shape creation method suitable for manufacturing a mother die for molding an optical element having a microstructure and an optical element molding die.

  For example, in the field of optical pickup devices that have been rapidly developed in recent years, optical elements such as extremely high-precision objective lenses are used. Molding can be said to be suitable for mass production because a uniform shaped product can be rapidly produced when such an optical element is molded using a mold made of plastic or glass. In general, such dies are often manufactured by cutting one by one using, for example, a single crystal diamond tool. However, since the mold is a consumable part that wears out in accordance with the number of uses, it is necessary to replace the mold periodically. Therefore, it is necessary to prepare a mold of the same shape in preparation for replacement, but when a mold is manufactured by cutting with a single crystal diamond tool or the like, it can be said that it is difficult to cut out a mold of the same shape, Therefore, there is a possibility that the shape of the optical element product may vary before and after the mold replacement, and there is a problem that the cost is high.

  On the other hand, there is an attempt to create a die by growing, for example, electroforming on a mother die having a mother optical surface corresponding to the optical surface of the optical element. According to such an attempt, even if the pattern formed on the mother optical surface of the mother die is fine, it can be transferred and formed with high accuracy.

  By the way, the master pattern used for such a purpose is obtained by applying a resist to the mother optical surface of the substrate to be drawn, forming a fine pattern by, for example, electron beam drawing, developing the resist, and then performing dry etching. Can do. After such a mother die is attached to a jig with an adhesive or the like, an electroformed member that becomes a die can be formed by growing electroforming so as to cover the mother optical surface of the mother die.

Here, electron beam drawing will be described. A conventional example of such electron beam drawing is disclosed in Patent Document 1.
JP-A-5-113503

  Since electron beam drawing forms a fine pattern, a beam running region (called a field) by a fine movement mechanism is extremely small, for example, 0.5 mm × 0.5 mm. On the other hand, an optical element such as an objective lens of the optical pickup device has a diameter of about 3 mm, and the mother optical surface of the drawing base is also sized accordingly. A fine pattern cannot be formed on the optical surface at once. Therefore, after drawing within one field of the electron beam, the electron beam irradiation source and the substrate to be drawn are moved relative to each other so that the next field can be drawn with the electron beam, and then the electron beam is drawn within the next field. A sequential drawing method has been devised. This is called a step-and-repeat method.

  Here, the inventors of the present invention have a problem at the boundary between the fields on the mother optical surface of the substrate to be drawn obtained by performing electron beam drawing by the step-and-repeat method and further developing. I discovered that. Such a problem will be described.

  FIG. 1 is a cross-sectional perspective view of a resist schematically showing an electron beam drawing process for creating a finely structured slope. FIG. 2 is a view of the resist in the electron beam drawing process as seen in the electron beam irradiation direction. In FIG. 1, a resist R is applied on a substrate S with a uniform thickness, and if an electron beam is irradiated to the resist R, the resist R changes in quality according to the dose amount. By developing the resist R, it is possible to form a fine structure having an inclined surface like a one-dot chain line.

  In the electron beam drawing process, as shown in FIG. 2, the electron beam B is traversed in the direction of the arrow indicated by the dotted line from the start end to the end of one field f11. The running is performed again from the start to the end, and as the slope to be formed becomes deeper, the running speed is reduced and the dose is increased so that the resist is removed to a deeper position during development. . When the electron beam drawing for one field f11 is completed, the process moves to the adjacent field f12, and the same electron beam drawing process is performed. Further, when the drawing of the columns (fields f11, f12,...) Is completed, the fields f21, f22,.

  Now, in the electron beam running, the boundary between the field f11 and the adjacent field f12 is the end of the electron beam running in the field f11, and at the same time, the boundary of the electron beam running in the adjacent field f12. It is the beginning. Further, the boundary between the field f11 and the field f21 (indicated by the broken line K in the figure, hereinafter referred to as the boundary K) is the boundary of the scanning region of the electron beam of one field.

  FIG. 3 shows an enlarged cross-sectional view (aspect ratio is different from the actual one) of the resist obtained by performing electron beam writing by step-and-repeat in this way and further developing. The present inventors paid attention to the phenomenon that the peak value in the vicinity of the boundary K is lower than the other peak values in the formed periodic sawtooth-shaped periodic pattern (see dotted line). Such a phenomenon is considered to be caused by the fact that the upper surfaces of the fields f11 and f21 are inclined toward the narrow groove across the boundary K, so that the sawtooth near the boundary K falls down. However, the upper surface of the resist is originally a portion that should be the basis of the mother optical surface, and when the sawtooth falls, light that does not contribute to image formation occurs in the light that has passed through the diffraction grating, and transmission efficiency and diffraction There is a risk of adversely affecting the optical characteristics such as reducing the efficiency.

  The present invention has been made in view of such a problem of the prior art, and an object thereof is to provide a shape creation method capable of obtaining a more accurate shape through electron beam drawing.

A shape creation method according to a first aspect of the present invention is a shape creation method for creating a three-dimensional shape by irradiating a resist applied on a substrate with an electron beam for each of a plurality of fields, and developing the resist.
The bond between the resist and the substrate is locally divided.

The shape creation method of the second aspect of the present invention is a shape creation method for creating a three-dimensional shape by irradiating a resist applied on a substrate with an electron beam for each of a plurality of fields, and developing the resist.
Rupture is caused at a predetermined position on the resist surface.

  The present inventors have conducted intensive research and have clarified why the upper surfaces of the fields f11 and f21 are inclined toward the narrow groove across the boundary B. Our hypothesis is as follows. First, a resist is uniformly coated on a substrate to be drawn, and then the resist is baked at Tg (about 100 ° C.) before electron beam drawing. However, when cooling is performed after baking, a difference in thermal expansion occurs between the substrate to be drawn and the resist, and electron beam drawing and development are performed on the portion remaining as internal stress. As a result, field f11, Since a narrow groove was formed between f21, the stress was released starting from this, and a slope inclined toward the narrow groove was formed.

  Based on this hypothesis, the present inventors have devised a method for releasing stress based on the difference in thermal expansion between the resist and the substrate. More specifically, the bond between the resist and the substrate is locally broken. That is, since the resist and the base material are tightly bonded, a difference in thermal expansion occurs. Therefore, if this is locally divided, the stress based on the difference in thermal expansion can be relieved and deformation of the resist can be prevented. Can do.

  However, there remains a problem of how the bond between the resist and the substrate can be locally broken. On the other hand, the present inventors have devised that the bond between the resist and the substrate can be locally broken by causing a tear at a predetermined position on the resist surface. Furthermore, it has been discovered that such tearing can be caused by baking the resist after electron beam writing, before or after development.

  FIG. 4 shows an enlarged cross-sectional view (aspect ratio is different from the actual one) of a resist obtained by performing electron beam writing, baking, and developing in the same step-and-repeat as in the prior art. As apparent from FIG. 4, according to the shape creation method according to the present invention, in the formed periodic sawtooth pattern, the peak value near the boundary K becomes equal to the other peak values, which is highly accurate. A microstructure can be formed.

  Therefore, it is preferable that the tearing is caused by baking the resist after the electron beam irradiation and before or after the development.

  The tearing is preferably caused by baking the resist after the electron beam irradiation and before the development.

  When the resist baking temperature is not lower than the softening point of the resist and not higher than the glass transition point, it is preferable to form appropriate tears.

  Furthermore, the present inventors have devised another method for locally breaking the bond between the resist and the substrate. More specifically, by performing development with a dose amount higher than usual, for example, a state in which the resist is removed to the base material after development, or a state in which a thin resist is attached to the base material can be generated. As a result, the bond between the resist and the substrate can be locally broken.

  The tear is preferably generated at a position of 20% or less of the maximum height in the three-dimensional shape of the resist after development.

  Preferably, the fracture is formed by irradiating the electron beam at a predetermined position on the resist surface with a dose amount more than twice the dose amount in the peripheral electron beam irradiation region.

  Preferably, at least one tear is provided in each field. Furthermore, it is more preferable that a plurality of the tears are provided in each field.

  ADVANTAGE OF THE INVENTION According to this invention, the shape creation method which can perform electron beam drawing so that a more highly accurate shape can be obtained can be provided.

  Hereinafter, an example of a preferred embodiment of the present invention will be specifically described with reference to the drawings. First, a drawing substrate to be drawn by an electron beam will be described with reference to FIGS. FIG. 5 discloses a drawing pattern drawn on the substrate and a drawing shape of the details thereof.

  As shown in the figure, as an example of a drawing pattern drawn on a drawing base material (hereinafter referred to as a base material) 2 of the present embodiment, a diffraction ring zone by circular drawing is disclosed. When the portion A which is a part of the drawing portion is enlarged, a diffraction zone composed of a plurality of blazes 3 is formed on the base material 2 as shown in FIG.

  The blaze 3 has a shape in which an inclined portion (slope) 3b and a side wall portion 3a are repeatedly connected. More specifically, as shown in FIG. 7, the base material 2 has a curved surface portion 2a (base optical surface of the base material) formed on at least one surface, and is formed for each pitch L1 by tilting the diffraction grating. , At least one pitch L1 of the diffraction grating, a side wall portion 3a rising from the curved surface portion 2a at the pitch break, a slope portion 3b formed between the adjacent side wall portions 3a and 3a ′, and a side wall A groove 3c formed in a boundary region between the portion 3a and the inclined portion 3b ′ is formed. In addition, it is preferable that this diffraction ring zone is formed by drawing the coating agent (resist) apply | coated on the curved-surface part 2a so that it may mention later.

  Here, a polymer resin material that is cured by heating or ultraviolet rays is used for the resist, and the bond between molecules is broken and decomposed in accordance with the amount of energy given by the electron beam ( The decomposed portion is removed by a developer described later).

  In the step-and-repeat method of the present invention, the area drawn on the base material shown in FIG. 5 is divided into a plurality of fields (drawing areas) as shown in FIG. 20 (top view of the base material). For each field, the beam drawing and the relative movement steps of the beam and the substrate are repeated, and a predetermined pattern (here, the diffraction ring zone) is drawn on the substrate.

  Specifically, each field is arranged concentrically according to the drawn diffraction zone, and each field has a fan shape. The fields arranged concentrically in this way are arranged continuously from the center of the concentric circle of the diffraction zone in the radial direction of the concentric circle (for example, the first drawing area A and the second drawing area B in FIG. 20). In this way, the drawing area on the substrate is divided into a plurality of drawing areas. As can be seen from the figure, the number of fields arranged in the radial direction varies depending on the size of the substrate to be drawn and the scannable distance of the beam.

  In the present embodiment, among the fields divided into a plurality of fields, the relationship between the field adjacent to the radial direction (for example, the first drawing area A and the second drawing area B in FIG. 20) and the pattern is determined in advance. Appropriate writing can be performed even if the beam shifts with time and the field interval changes.

  Moreover, it is preferable that the base material 2 is a matrix material for forming an optical element used in the optical pickup device, for example, a mold for forming an objective lens. Since a plurality of dies having the same shape are created from the mother die obtained by the above drawing, it is possible to prevent variation in the shape of the optical element product at the time of die replacement. In such an optical element, a diffraction ring zone is provided for aberration correction in an optical pickup device that achieves DVD / CD compatibility using information recording light of different wavelengths. Hereinafter, a specific configuration of an electron beam drawing apparatus which is a premise for forming such a base material will be described.

(Overall configuration of electron beam lithography system)
Next, the overall schematic configuration of the electron beam drawing apparatus will be described with reference to FIG. FIG. 8 is an explanatory diagram showing the overall configuration of the electron beam lithography apparatus of this example.

  As shown in FIG. 8, the electron beam drawing apparatus 1 of the present embodiment forms a high-resolution electron beam probe with a large current and scans the substrate 2 to be drawn at a high speed. An electron gun 12 as means, a slit 14 through which an electron beam from the electron gun 12 passes, an electron lens 16 for controlling the focal position of the electron beam passing through the slit 14 with respect to the substrate 2, and an electron beam An aperture 18 disposed on the path from which the light is emitted, a deflector 20 that controls a scanning position on the base material 2 that is a target by deflecting an electron beam, and a correction coil 22 that corrects the deflection. The high-resolution electron beam probe made of an electron beam is formed, and the target is irradiated with the beam by scanning the electron beam probe. These parts are arranged in the lens barrel 10 and maintained in a vacuum state when the electron beam is emitted.

  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 controlled by generating a plurality of electronic lenses according to the current values of the coils 17a, 17b, and 17c, which are spaced apart at a plurality of locations along the height direction. The focal position of the electron beam is controlled.

  The measuring device 80 emits light from the first laser length measuring device 82 that measures the position in the height direction of the base material 2 by irradiating the base material 2 with a laser, and the first laser length measuring device 82. Irradiation different from the first laser length measuring device 82 and the first light receiving portion 84 that receives the reflected light when the laser beam (first irradiation light) reflected from the flat portion of the substrate 2 is reflected. The second laser length measuring device 86 that irradiates from an angle and the laser light (second irradiation light) emitted by the second laser length measuring device 86 are excluded from the light blocked by the base material 2. And a second light receiving portion 88 that receives light.

  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 θ direction. As a result, the XYZ stage 30 can be operated three-dimensionally and alignment can be performed. That is, if the base material 2 is placed on the XYZ stage 30, the relative position with the electron gun 12 as a beam irradiation source can be arbitrarily changed, so that drawing can be performed by the above-described step-and-repeat method.

  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 A lens power supply unit 106 for operating each of the electronic lenses, and a lens control unit 108 for adjusting and controlling currents corresponding to the electronic lenses in the lens power supply unit 106. The

  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 And a high-precision D / A converter 114c.

  Further, the control circuit 100 corrects a position error in the deflector 20, and supplies a position error correction signal or the like to each of the high-speed D / A converters 114a and 114b and the high-precision D / A converter 114c. The position error correction circuit 116 that performs position error correction by the correction coil 22 by prompting the position error correction or supplying the signal to the coil control unit 110, the position error correction circuit 116, and each high-speed D / D An 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 this purpose.

  Still further, the control circuit 100 is a first laser drive control circuit for controlling the movement of the laser irradiation position and the angle of the laser irradiation angle by moving the first laser length measuring device 82 up and down and left and right. 130, a second laser drive control circuit 132 that controls the movement of the laser irradiation position and the angle of the laser irradiation angle by moving the second laser length measuring device 86 up, down, left, and right; The first laser output control circuit 134 for adjusting and controlling the output (laser light intensity) of the laser irradiation light in the laser length measuring device 82 and the output of the laser irradiation light in the second laser length measuring device 86 A second laser output control circuit 136 for adjusting and controlling a first measurement calculation unit 140 for calculating a measurement result based on a light reception result of the first light reception unit 84, a second reception unit Based on the light receiving result of the section 88 configured to include a second measuring calculation unit 142 for calculating the measurement results.

  Furthermore, 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 first and second laser driving circuits 130 and 132 described above. First and second laser output control circuits 134 and 136 First and second measurement calculation units 140 and 142 A stage control circuit 150 A mechanism control circuit 154 for controlling the loader control circuit 152, and a vacuum exhaust device 70 An evacuation control circuit 156 for controlling the evacuation of the gas, a measurement information input unit 158 for inputting measurement information, a memory 160 which is a storage means for storing inputted information and other plural information, It is formed by a program memory 162 that stores a control program for performing various controls, and for example, a CPU that controls these components. It is configured to include a control unit 170, a.

  In the electron beam drawing apparatus 1 having the above-described configuration, when the base material 2 transported by the loader 40 is placed on the XYZ stage 30, the air in the lens barrel 10 and the casing 11 is evacuated by the vacuum exhaust device 70. After exhausting dust and dust, 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. The position of the focal depth of the electron beam B, that is, the focal position is controlled by adjusting and controlling the respective current values flowing through the coils 17a, 17b, 17c, etc. of the electron lens 16, so that the focal position becomes the drawing position. The movement is controlled.

  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.

  In this example, the control may be performed by either one of the electron beam control and the XYZ stage 30 control, or by using both.

(measuring device)
Next, the measuring apparatus 80 will be described with reference to FIGS. More specifically, 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 as shown in FIG. Have.

  First light beam S1 is applied to the flat portion 2b of the substrate 2 from the direction intersecting the electron beam by the first laser length measuring device 82, and is reflected from the flat portion 2b of the substrate 2. The first light intensity distribution is detected by receiving the beam S1.

  At this time, as shown in FIG. 9, the first light beam S1 is reflected by the flat portion 2b of the base material 2, and therefore on the flat portion 2b of the base material 2 based on the first intensity distribution. The (height) position is measured and calculated. However, in this case, the (height) position on the curved surface portion 2a of the substrate 2 cannot be measured.

  Therefore, in this example, a second laser length measuring device 86 is further provided. In other words, the second laser length measuring device 86 irradiates the base material 2 with the second light beam S2 from a direction substantially orthogonal to the electron beam different from the first light beam S1, and the second light beam S2. The light except the light blocked by the base material 2 is received through the pinhole 89 included in the second light receiving unit 88, whereby the second light intensity distribution is detected.

  Specifically, when the second light beam S2 passes through a specific height at a certain position (x, y) on the curved surface portion 2a in the XY reference coordinate system, at this position (x, y), FIG. As shown in A) to (C), when the second light beam S2 hits the curved surface of the curved surface portion 2a, scattered light SS1 and SS2 are generated, and the light intensity of the scattered light is weakened. In this way, as shown in FIG. 10, the position is measured and calculated based on the second light intensity distribution detected by the second light receiving unit 88.

  In this calculation, as shown in FIG. 11, the signal output Op of the second light receiving unit 88 has a correlation with the height of the base material as shown in the characteristic diagram of FIG. By storing a correlation table indicating the characteristics, that is, the correlation in the memory 160 of 100 in advance, the height position of the base material is calculated based on the signal output Op in the second light receiving unit 88. Can do.

  Then, using the height position of the base material as a drawing position, for example, the focus position of the electron beam is adjusted and drawing is performed.

(Outline of drawing position calculation principle)
Next, an outline of the principle in the case of performing drawing in the electron beam drawing apparatus 1 which is a feature of this example will be described.

  First, the base material 2 is preferably a base material for forming an optical element made of, for example, resin or the like, for example, a mold for forming an objective lens, and has a flat portion 2b having a substantially flat cross section and a protrusion from the flat portion 2b. And a curved surface portion 2a forming a curved surface. The curved surface of the curved surface portion 2a is not limited to a spherical surface, and may be a free curved surface having a change in any other height direction such as an aspherical surface.

  In such a base material 2, before placing the base material 2 on the XYZ stage 30, a plurality of, for example, three reference points P00, P01, P02 on the base material 2 are determined 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 (coordinate data indicating the three-dimensional shape of the base material) 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. 13A, a plurality of, for example, three reference points P10, P11, P12 on the base material 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.

  Note that the second measurement described above can be performed using the measurement device 80 which is the first measurement means of the electron beam drawing apparatus 1.

  The first measurement needs to be measured in advance at another location using another measurement device. As such a measuring apparatus for measuring the reference point in advance before placing the substrate 2 on the XYZ stage 30, a measuring apparatus (second measuring means) having the same configuration as the measuring apparatus 80 described above is used. ) Can be adopted.

  In this case, the measurement result from the measurement device is input by, for example, the measurement information input unit 158 shown in FIG. 8 or transferred via a network (not shown) connected to the control circuit 100 to the memory 160 or the like. Will be stored. Of course, there may be a case where this measuring apparatus is unnecessary.

  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. 13C, the focal position of the electron beam focal depth FZ (beam waist BW) is drawn in one field (m = 1) of the unit space in the three-dimensional reference coordinate system. The position is adjusted and controlled (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). The electron beam has a deep focal depth as shown in FIG. 14, and the electron beam narrowed down by the electron lens 16 forms a beam waist BW having a substantially constant thickness within the focal depth FZ. Here, the focal depth FZ refers to the length of the beam waist having a constant thickness in the electron beam traveling direction. Note that the above-mentioned focal position indicates the center position of the beam waist in the electron beam traveling direction. In the case of the electron beam B, as shown in FIG. 14, when the width D of the electron lens 16 and the depth f from the electron lens 16 to the beam waist (the narrowest part of the beam diameter) BW, D / f is The resolution is about 0.01, for example, has a resolution of about 50 nm, and the depth of focus is about several tens of μ, for example.

  Then, as shown in FIG. 13C, 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 in real time 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. Will be done. 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.

  Furthermore, a processing program for performing various arithmetic processes, measurement processes, control processes, and the like as described above is stored in the program memory 162 in advance as a control program.

(Dose distribution)
FIG. 15 is a functional block diagram of the control system of the electron beam lithography apparatus having the characteristic configuration of the present embodiment. As shown in the figure, the memory 160 of the electron beam drawing apparatus 1 has a shape storage table 161. In this shape storage table 161, for example, the diffraction grating is tilted on the curved surface portion 2a of the substrate 2 and each pitch is set. The dose distribution information 161a relating to the dose distribution characteristics that predefine the dose distribution with respect to the scanning position when forming each time, and the dose amount of the uneven portion when forming the surface reflection preventing unevenness for each pitch The dose distribution information 161b, the dose distribution correction calculation information 161c obtained by correcting the dose distribution, and other information 161d are stored. The dose distribution correction calculation information 161c is a table or calculation information that is a basis for calculating a dose amount and the like.

  The program memory 162 stores a dose at a predetermined inclination angle on the curved surface portion 2a based on information such as the processing program 163a for performing these processes, the dose distribution information 161a, 161b, and the dose distribution correction calculation information 161c. A dose distribution calculation program 163b and other processing programs 163c for calculating distribution characteristics and the like are included.

  In the control system having such a configuration, the dose distribution information is stored in advance in the shape storage table 161 of the memory 160, and the dose distribution information is extracted at the time of drawing based on the processing program 163a. Will be drawn.

  Alternatively, when the control unit 170 reaches a routine for calculating a dose amount while executing a predetermined drawing algorithm by the processing program 163a, the control unit 170 executes the dose distribution calculation program 163b to calculate a dose distribution according to the inclination angle. After calculating the corresponding dose distribution characteristic information while referring to the stored tables such as the dose distribution information 161a, 161b, the dose distribution correction calculation information 161c, etc., the calculated dose distribution characteristic information A method may be used in which the image is stored in a predetermined temporary storage area of the memory 160 and the drawing is performed by calculating the dose amount while referring to the dose distribution characteristic information.

(Specific configuration of control system)
Next, a specific configuration of a control system for performing various processes when the circle drawing is approximated by a regular polygon and linearly scanned will be described with reference to FIG. FIG. 16 discloses a detailed configuration of a control system of the electron beam drawing apparatus according to the present embodiment.

  As shown in FIG. 16, the control system 300 of the electron beam drawing apparatus performs various data (according to the radius of the circle) necessary to approximate a regular polygon (including an indefinite polygon) at the time of drawing a circle, for example. For example, for a circle with a radius of kmm, information corresponding to each circle, such as the number of divisions n by the polygon, the coordinate information of the position of each side, the multiple of the number of clocks, and the position in the Z direction Etc., and not only circle drawing but also various data necessary for linear approximation when drawing various curves, various drawing patterns (rectangle, triangle, polygon, vertical line, horizontal line, diagonal line, disk, A drawing pattern data memory 301 which is a drawing pattern storage means for storing data relating to a circle, a triangle, a circular arc, a sector, an ellipse, and the like.

  In addition, 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 (2k + 1) line ((k = 0) from the drawing condition calculation unit 310. , 1, 2,..., (2k + 1), but if (k = 1, 2,...), It may be (2k-1). (2k + 1) line drawing condition calculation means 311; (2k + 1) time constant setting circuit 312 for setting a time constant for one line based on line drawing condition calculation means 311; and (2k + 1) line drawing condition calculation means 311 based on The number of counters is set based on the start / end point voltage setting circuit 313 for setting the start and end voltages of one line and the (2k + 1) line drawing condition calculation means 311. A counter number setting circuit 314; an enable signal generation circuit 315 for generating an enable signal based on the (2k + 1) line drawing condition calculation means 311; and a deflection signal output circuit 320 for outputting a deflection signal for odd lines. It consists of

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

  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. Based on the count timing from the circuit 321, the counter circuit 321, and the odd line drawing condition signal CL 3 in the start / end voltage setting circuit 313, the DA conversion circuit 322 that performs DA conversion, and the DA conversion circuit 322 And a smoothing circuit 323 that performs a process of smoothing the converted analog signal (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 DA 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 converted analog signal.

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

  In addition, the “calculation unit” can be configured by the control system 300 including the drawing pattern data memory 301 and the drawing condition calculation unit 310 according to the present embodiment. This "calculation means" has a function of calculating at least two positions corresponding to a distance corresponding to a time that is an integral multiple of the minimum time resolution of the DA converter on the scanned scanning line. In this case, the “control unit” of 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, a distance corresponding to a time that is an integral multiple of the minimum time resolution of the DA converter is defined as one side on a scanning line scanned in a substantially circular shape. A function of calculating the position of each vertex of the polygon. 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 a predetermined drawing condition is performed, for example, a regular polygon for one circle. Information about the first and odd-numbered lines of each side when approximated to each side is (2k + 1) to the line drawing condition calculation means 311. Information about the next side and even-numbered lines is (2k). Each is transmitted to the line drawing condition calculation means 331.

  Thereby, for example, the (2k + 1) line drawing condition calculation means 311 generates drawing conditions for 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 (2k) line drawing condition calculation means 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 the drawing for a certain circle is completed, the drawing condition calculation means 310 transmits a message to that effect to the blanking amplifier 350, and performs a process for prompting the drawing of another next circle. In this way, drawing that approximates each circle with a polygon is performed.

  Next, a process of forming a mother die using the above-described electron beam drawing and forming an optical element molding die from the mother die will be described. FIG. 17 is a flowchart showing a mold manufacturing method according to the present embodiment. 18 is a cross-sectional view showing a substrate to be processed in the main process shown in FIG.

  First, in step S101 of FIG. 17, after the resin material is heated and melted, the resin material is injected into the spaces in the original molds K1 and K2, and the base material 2 is injection-molded. At this time, an annular zone is not formed on the transfer surface K1a of the master mold K1, but since it has an aspherical shape corresponding to the optical surface of the optical element, the mother optical surface of the injection-molded substrate 2 ( That is, the non-planar portion 2d) is transferred with an aspheric shape with high accuracy. In addition, the base material 2 may be cut out from silicon by cutting.

  Subsequently, in step S102, the base material 2 is set on a spin coater (not shown), and in step S103, a press pin is performed while the resist L is allowed to flow onto the base material 2, and then in step S104, the speed is higher than that of the press pin. Then, the resist spin film is formed by carrying out the main spin rotating in the direction (see FIG. 18B). The reason why the press pin and the main spin are separated is that the resist L having a uniform thickness is coated on the base optical surface 2d of the base material, which is a complicated curved surface such as an aspherical shape. It is also possible to coat the base optical surface 2d of the base material by spraying the resist L onto the base material 2. The softening point temperature of the resist resin used here is 70 ° C. to 80 ° C., and a glass transition temperature around 110 ° C. is used.

  Thereafter, in step S105, the substrate 2 is removed from the spin coater, and in step S106, a baking process is performed at an atmospheric temperature of 180 ° C. for 20 minutes to cure and stabilize the resist L film. Here, when a sufficient film thickness cannot be obtained by a single coating process of the resist L, the processes of steps S102 to S106 are repeated to form a sufficient film thickness by laminating the resist L film. Incidentally (step S107), in step S108, an electron beam drawing process is performed on the resist L on the mother optical surface 2d of the substrate 2 using the electron beam B irradiated from an electron beam drawing apparatus (not shown) (FIG. 18). (See (c)).

  After the electron beam drawing process, a post-baking process is performed in step S108A. More specifically, the resist is baked above the softening point of the resist and below the glass transition point. Note that the resist may be baked after development. An example of a post-baking process is shown. As for the heating conditions, the set temperature is 100 ° C., and baking is performed by heating for about 20 minutes in the case of oven heating and for about 5 minutes in the case of hot plate heating. After that, in step S109, the base material 2 is subjected to development processing and rinsing processing (see FIG. 18D), and unnecessary resist is removed to obtain a ring-shaped resist L. Here, since the removal amount of the resist L increases in accordance with the dose amount, the resist L can be left so as to form a blazed diffraction ring zone. According to this embodiment, since post-baking is performed, tearing occurs at a position of 20% or less of the maximum height in the three-dimensional shape of the resist after development, and stress in the resist is released. It is possible to create a highly accurate three-dimensional shape by suppressing the deformation of.

  As described above, when post-baking after the electron beam drawing process and before the development process, at the time of the electron beam drawing process, in the portion irradiated with the electron beam, the interatomic bonds in the resin molecules of the resist resin are broken, A phenomenon occurs in which the molecular weight of the resin molecule is reduced. In a portion where the amount of electron beam irradiation is large, the molecular weight becomes smaller and the strength of the resin decreases. In this state, when post baking is performed at a resist softening point or more and a glass transition point or less, the entire resist resin is softened, so that the interatomic bond extending to a deep region in the thickness direction of the resist is cut, and the resin molecular weight becomes smaller and the strength is increased. The weakened portion can not resist the stress inside the resist, that is, the force to shrink, and tears. Thereby, a desired tear can be produced. When post-baking after development, the resist remaining after development is formed with a thick portion and a thin portion of the resist. When post-baking is performed in this state, the thinned portion of the resist remaining by softening the entire resist resin is torn without being able to resist the internal stress of the resist, that is, the force to shrink. . In any case, since the heating is performed at a set temperature not higher than the glass point of the resist, a desired tear can be obtained without destroying the three-dimensional shape of the entire resist.

  In step S110, the surface of the base optical surface 2d of the substrate 2 is engraved by dry etching using a plasma shower to form a blazed diffraction zone 3 (exaggerated from the actual drawing) (see FIG. 18 (e)). Further, in step S111, the base material 2 is bonded to a cylindrical jig (not shown). Thereafter, a backing member is disposed on the base material 2, and in step S112, the base material 2 whose surface is activated in a nickel sulfamate bath is immersed to grow electroforming to obtain an electroformed member. Further, in step S113, the electroformed member is cut, and in step S114, the base material 2 and the electroformed member are removed. The removed electroformed member is machined in step S115, incorporated into a molding apparatus as an optical element molding die, and used for molding an optical element.

  FIG. 19 is a schematic diagram of an optical pickup device including an objective lens as an example of an optical element formed by the beam drawing method according to the present embodiment. In FIG. 19, an optical pickup device 400 includes a semiconductor laser 401, a collimator lens 402, a separation prism 403, an objective lens 404, a magneto-optical disk 405 (a magneto-optical recording medium) such as a DVD and a CD, a half-wave plate 406, a polarization A separation element 407, a condenser lens 408, a cylindrical lens 409, and a split photodetector 410 are included.

  In the optical pickup device 400 having the above-described configuration, the laser light from the semiconductor laser 1 is converted into parallel light by the collimator lens 402, reflected by the separation prism 403 toward the objective lens 404, and collected by the objective lens 404 to the diffraction limit. Light is applied to the magneto-optical disk 405 (a magneto-optical recording medium).

  The laser reflected light from the magneto-optical disk 405 enters the objective lens 404 and becomes parallel light again, passes through the separation prism 403, further passes through the half-wave plate 406, and rotates the polarization direction by 45 degrees. Then, the light is incident on the polarization separation element 407, and is separated into two light fluxes composed of both P and S polarizations whose optical paths are close to each other. The P- and S-polarized light beams are condensed by a condensing lens 408 and a cylindrical lens 409, respectively, to form respective spots in a separate light receiving region (light receiving element) of the split photodetector 410.

  The present invention has been described above with reference to the embodiments. However, the present invention should not be construed as being limited to the above-described embodiments, and can be modified or improved as appropriate. For example, as shown in FIG. 21, the surface of the substrate S is irradiated by irradiating the electron beam to a position between adjacent saw teeth at a dose amount that is twice or more the dose amount in the irradiation region of the surrounding electron beam. The internal stress of the resist R can also be released by forming a tear G that exposes. Specifically, the resist R having a film thickness of about 1 μm to 3 μm has a dose amount (incident electron amount) of 300 μC / cm 2 at a maximum with respect to a normal irradiation region, and the irradiation for forming the above-mentioned tear G. The region is irradiated with an electron beam at twice or more, specifically, at a dose of 600 μC / cm 2 or more. For example, the electron beam irradiation to the region where the tear G is formed preferably has a dose amount of 3000 μC / cm 2 to 6000 μC / cm 2 when the acceleration voltage of the electron beam is about 50 kV. The present invention can be applied not only to a mold for molding an optical element but also to various drawing processes.

It is the cross-sectional perspective view of the resist which showed typically the electron beam drawing process for creating the inclined surface of a fine structure. It is the figure which looked at the resist in an electron beam drawing process in the irradiation direction of the electron beam. It is an expanded sectional view of the resist obtained by performing electron beam drawing by the conventional method, and developing further. It is an expanded sectional view of the resist obtained by performing electron beam drawing by the method of the present invention, and developing further. It is explanatory drawing which shows an example of schematic structure of the base material of this invention. It is explanatory drawing which shows the principal part of the base material of FIG. 5 in detail. It is a schematic sectional drawing of a diffraction ring zone. It is explanatory drawing which shows the schematic structure of the whole beam drawing apparatus of this invention. It is explanatory drawing for demonstrating the principle of a measuring apparatus. The same figure (A)-(C) is explanatory drawing for demonstrating the method of measuring the surface height of a base material. It is explanatory drawing which shows the relationship between the light projection and light reception of a measuring apparatus. It is a characteristic view which shows the relationship between a signal output and the height of a base material. FIGS. 6A and 6B are explanatory views showing a base material drawn by the electron beam drawing apparatus of FIG. 6, and FIGS. 6C are explanatory views for explaining the drawing principle. It is explanatory drawing for demonstrating the beam waist in an electron beam drawing apparatus. It is a functional block diagram showing details of a control system for performing drawing with a predetermined dose distribution in an electron beam drawing apparatus. It is a functional block diagram which shows the structure of the more detailed control system of an electron beam drawing apparatus. It is a flowchart which shows the manufacturing method of the metal mold | die concerning this Embodiment. FIG. 18 is a cross-sectional view showing a matrix (base material) to be processed in the main process shown in FIG. 17. It is explanatory drawing which shows the outline of an optical pick-up apparatus. It is a top view of the base material which shows a drawing area | region typically. It is sectional drawing which shows the resist on a base material.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Electron beam drawing apparatus 2 Base material (drawing base material)
DESCRIPTION OF SYMBOLS 3 Diffraction ring zone 3a Side wall part 3b Inclination part 3c Groove part 10 Lens barrel 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 apparatus 70 Vacuum exhaust apparatus 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 portion 112c Main deflection portion 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 142 Second measurement calculation unit 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 (8)

A shape creation method for creating a three-dimensional shape by irradiating a resist applied on a substrate with an electron beam for each of a plurality of fields and performing development,
A shape creation method characterized by locally breaking the bond between the resist and the substrate. A shape creation method for creating a three-dimensional shape by irradiating a resist applied on a substrate with an electron beam for each of a plurality of fields and performing development,
A shape generating method, wherein a tear is generated at a predetermined position on the surface of the resist.   The shape creation method according to claim 2, wherein the tearing occurs by baking the resist after the electron beam irradiation and before or after the development.   4. The shape creation method according to claim 2, wherein the tearing is caused by baking the resist after the electron beam irradiation and before the development.   The shape creation method according to claim 3 or 4, wherein a baking temperature of the resist is not less than a softening point of the resist and not more than a glass transition point.   The shape creation method according to claim 2, wherein the tearing occurs at a position of 20% or less of a maximum height in the three-dimensional shape of the resist after development.   3. The fracture is formed by irradiating an electron beam at a predetermined position on the surface of the resist at a dose amount more than twice a dose amount in a peripheral electron beam irradiation region. The shape creation method described. The shape creation method according to claim 1, wherein at least one of the tears is provided in each field.

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