JP2007216263A - Laser beam machining device and machining method therefor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a laser beam machining device and a machining method therefor for forming a nano structure having a predetermined ultra-fine pattern on a workpiece, and evaluating the machined shape of the nano structure in a short period of time. <P>SOLUTION: The laser beam machining device includes a rotating mechanism 101 for placing and rotating the workpiece 102, and a moving mechanism movable straight in the radial direction of the workpiece 102, and a beam spot formed on the surface of the workpiece 102 by laser beams is moved while depicting the locus. By adjusting the intensity distribution of the laser beams of the beam spot, the ultra-fine pattern to be formed on the workpiece 102 is adjusted so as to be an intended shape. In order to set parameter values during the adjustment, the formed ultra-fine pattern is evaluated by evaluating the reflected light from the ultra-fine pattern. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a laser processing apparatus and a processing method thereof for irradiating a processing target made of a heat-reactive substrate with a laser beam and forming a predetermined ultrafine pattern on the surface of the processing target. Laser processing apparatus and processing method for manufacturing ultra fine pattern with nano unit size below beam spot diameter on processing target using semiconductor laser used for manufacture of semiconductor integrated circuit and ultra fine processing of optical component About.

  2. Description of the Related Art Conventionally, as a laser drawing apparatus for manufacturing photomasks and reticles used in integrated circuit manufacturing, etc., members to be processed placed on an XY table by driving two orthogonal sliders are moved in the X and Y directions. 2. Description of the Related Art An XY table type laser drawing apparatus that draws a pattern by focusing a laser beam on a member to be processed through an optical system while moving it and forming a beam spot on the member to be processed is well known.

  However, when a pattern is drawn by such a conventional XY table type laser drawing apparatus, there is a problem that if the number of pixels increases, the number of times the slider moves or accelerates in the XY direction increases and the drawing time becomes longer. . In addition, when painting the inside of the pattern, repeated motion increases, and when drawing at high speed, the linear motor is considerably loaded, and at the same time, the XY table reacts during acceleration / deceleration, causing itself to vibrate. There was a problem that the accuracy decreased. Furthermore, it is necessary to manufacture a plurality of photomasks, and alignment and exposure for the number of photomasks are also required in the exposure process, which increases the manufacturing time and significantly increases costs. It was.

  Therefore, in order to solve such problems, there has been proposed a laser drawing apparatus capable of reducing the drawing time for processing a pattern even when the number of pixels is large by combining a rotating body and an optical system, and capable of high-precision processing. ing. For example, Patent Document 1 proposes a laser drawing apparatus using a disk-type rotating body as the rotating body, and Patent Document 1 discloses a laser drawing apparatus using a drum-type rotating body as a rotating body. 2 is proposed.

  The laser drawing apparatus described in Patent Document 1 is an apparatus that performs high-speed drawing by moving a beam spot in the radial direction while rotating a disk-shaped substrate coated with a photoresist on a turntable. It is. In this device, the exposure amount (laser power) is changed for each pixel constituting the drawing pattern, and the fine pitch pattern in the deep direction is highly accurate by making the track pitch equal to the beam spot radius. It can be processed into. In addition, this laser drawing apparatus can record a predetermined two-dimensional pattern regardless of the rotational speed by synchronizing the rotational speed of the turntable and the control signal for light modulation.

  Further, a laser drawing apparatus using a drum-type rotating body described in Patent Document 2 winds a flexible long work around a rotating drum, and its center is adjacent to the outer periphery of the rotating drum. A guide mechanism extending in the axial direction is provided, and a moving mechanism including a laser array is provided so as to be movable along the guide mechanism. In this laser drawing apparatus, the laser array is moved while rotating a long workpiece, and the copper film formed on the workpiece is removed by laser light emitted from each laser light source of the laser array. Can be drawn with high accuracy. The laser drawing apparatus using the disk-type rotating body and the laser drawing apparatus using the drum-type rotating body are used depending on the application while taking into account the advantages of each.

JP 2001-133987 A JP 2001-20993 A

  However, the laser drawing apparatus described in Patent Document 1 or Patent Document 2 collects laser light on a quartz master disk coated with a photoresist or a work on which a copper film is formed, and moves the optical system. Since a predetermined pattern is drawn in the region, the diameter of each pattern cannot be made smaller than the beam spot diameter, and it is impossible to draw an ultrafine pattern.

  In other words, the laser drawing apparatuses described in Patent Document 1 and Patent Document 2 have the processing depth of each pattern because the diameter of the laser spot corresponds to the diameter of each pattern even if the amount of laser irradiation is changed. Although it could be changed, the diameter of each pattern could not be changed.

  Moreover, in the laser drawing apparatuses described in Patent Document 1 and Patent Document 2 described above, in order to determine the conditions for setting the optimum conditions for drawing, several conditions were changed and drawing was performed. After that, there was no method other than observing the shape of the processing pattern with a microscope or the like, and there was a problem that it took a long time to set the optimum conditions.

  The present invention has been made in view of such a problem, and an object of the present invention is to produce an ultrafine pattern having a diameter equal to or smaller than the diameter of the beam spot, and to set the size of the produced ultrafine pattern to the diameter of the beam spot. It is possible to provide a laser processing apparatus and a processing method thereof that can be adjusted to the following arbitrary sizes and that can evaluate the shape of the produced ultrafine pattern in a short time.

  The present invention has been made in order to achieve such an object, and the invention according to claim 1 is directed to irradiating a processing object made of a heat-reactive substrate with a laser beam, so that the surface of the processing object is obtained. In the laser processing apparatus for forming a predetermined ultrafine pattern, the rotating means for rotating the object to be processed, and the laser beam irradiated toward the rotation surface of the object to be processed rotated by the rotating means, A moving means capable of linearly moving in a rotation direction at a position where the laser beam of the processing object is irradiated and a direction substantially perpendicular to the irradiation direction of the laser beam; and toward the processing object Irradiation means for emitting laser light, optical means including an objective lens for condensing the laser light from the irradiation means on the surface of the object to be processed to form a beam spot, and the object to be processed are irradiated The bee Light detection means for detecting reflected light from the surface of the spot, laser driving means capable of directly modulating the light intensity of the laser light, and adjusting the light intensity distribution of the beam spot collected by the optical means And a nanostructure having a predetermined ultrafine pattern not larger than the diameter of the beam spot on the object to be processed by a beam spot having a light intensity distribution adjusted by the adjusting means. And

  According to a second aspect of the present invention, in the first aspect of the present invention, the adjusting means receives at least a signal output by the autofocus function for driving the objective lens from the surface of the workpiece. Focus offset voltage applying means for applying a signal corresponding to an amount of shifting the focus of the laser light is provided.

  According to a third aspect of the present invention, in the first or second aspect of the present invention, the reproduction signal generated from the signal based on the reflected light output from the light detection means by irradiating the nanostructure with a laser beam. An evaluation means for evaluating the shape of the ultrafine pattern based on the above is provided.

  According to a fourth aspect of the present invention, in the third aspect of the present invention, the evaluation means is configured so that, based on the reproduction signal, the light amount of reflected light or the light amount ratio or reflected light of the reflected light from the ultrafine pattern. The shape of the ultrafine pattern is evaluated by detecting the polarization characteristic of light.

  According to a fifth aspect of the invention, in the invention of the third or fourth aspect, the parameter for setting an adjustment parameter value of the adjusting means for adjusting the light intensity distribution based on an evaluation result by the evaluating means. A value setting means is provided.

  The invention according to claim 6 is the laser processing method of irradiating a processing target made of a heat-reactive substrate with a laser beam to form a predetermined ultrafine pattern on the surface of the processing target. A rotation step for rotating the object by a rotating means, and a position at which the laser light of the object to be processed is irradiated with the laser light irradiated toward the rotating surface of the object to be processed rotated by the rotating means. A moving step of relatively moving in a direction substantially perpendicular to the rotation direction of the laser beam and the irradiation direction of the laser beam, an irradiation step of emitting the laser beam toward the workpiece by an irradiation unit, and the irradiation And forming the beam spot by condensing the laser beam from the means on the surface of the object to be processed by optical means including an objective lens, and irradiating the object to be processed A light detecting step for detecting reflected light from the surface of the beam spot by a light detecting means, a laser driving step for directly modulating the light intensity of the laser light by a laser driving means, and a light focused by the optical means. An adjusting step of adjusting the light intensity distribution of the beam spot by an adjusting unit, and the beam spot of the light intensity distribution adjusted by the adjusting unit has a predetermined spot smaller than the diameter of the beam spot on the workpiece. It is characterized by producing a nanostructure having an ultrafine pattern.

  According to a seventh aspect of the present invention, in the invention according to the sixth aspect, the adjustment step includes at least a signal output by the autofocus function for driving the objective lens from the surface of the workpiece. A focus offset voltage applying step for applying a signal corresponding to an amount of shifting the focus of the laser light is provided.

  The invention according to claim 8 is the reproduction signal generated from the signal based on the reflected light output from the light detection means by irradiating the nanostructure with laser light in the invention according to claim 6 or 7. And an evaluation step for evaluating the shape of the ultrafine pattern based on the above.

  The invention according to claim 9 is the invention according to claim 8, wherein the evaluation step is based on the reproduction signal, and the amount of reflected light or the ratio of reflected light or the reflected light from the ultrafine pattern. The shape of the ultrafine pattern is evaluated by detecting the polarization characteristic of light.

  According to a tenth aspect of the present invention, in the invention according to the eighth or ninth aspect, the parameter for setting the value of the adjustment parameter of the adjustment means for adjusting the light intensity distribution based on the evaluation result of the evaluation step. It has a value setting step.

  According to the present invention, the adjusting means for adjusting the light intensity distribution of the beam spot focused on the workpiece made of the heat-reactive substrate is provided, so that the light intensity distribution of the beam spot is adjusted by the adjusting means. Thus, the size of the ultrafine pattern produced on the workpiece can be made smaller than the diameter of the beam spot, and the size of the ultrafine pattern can be made arbitrarily smaller than the diameter of the beam spot. Can do.

  In addition, since the nanostructure is irradiated with laser light and provided with an evaluation means for evaluating the shape of the ultrafine pattern based on the reproduction signal generated from the signal based on the reflected light output from the light detection means, the ultrafine pattern is provided. The shape can be evaluated in a short time.

Embodiments of the present invention will be described below with reference to the drawings.
FIG. 1 is a configuration diagram for explaining a laser processing apparatus according to the present invention, and FIG. 2 is a configuration diagram of the optical processing head 103 shown in FIG. This laser processing apparatus irradiates a processing object 102 made of a heat-reactive substrate with laser light, and forms a predetermined ultrafine pattern on the surface of the processing object 102.

  This laser processing apparatus includes a turntable rotating mechanism 101 that places and rotates a workpiece 102 and an optical machining head 103 that is disposed toward the rotation surface of the workpiece 102 in the radial direction of the workpiece 102. And a moving mechanism composed of a sled motor 115 that can move relatively linearly, and is configured such that the laser beam moves while drawing a locus on the rotating surface of the workpiece 102.

  In addition, the optical processing head 103 includes a first semiconductor laser 201, a second semiconductor laser 215, a first photodiode (PD1) 214, a second photodiode (PD2) 206, and a third semiconductor laser 201. The photodiode (PD3) 225, the fourth photodiode (PD4) 220, the super-resolution optical element 207, and the objective lens 210 are included.

  The first semiconductor laser 201 emits laser light for producing an ultrafine pattern toward the workpiece 102. The second semiconductor laser 215 emits laser light for evaluating an ultrafine pattern toward the workpiece 102. The objective lens 210 converts the laser light from the first semiconductor laser 201 onto the surface of the workpiece 102 via an optical system such as the first collimating lens 202, the first anamorphic prism 203, and the dichroic mirror 221. The laser beam from the second semiconductor laser 215 is converted into an optical system such as a second collimating lens, a second anamorphic prism 217, and a beam splitter 218. The beam spot is formed by condensing on the surface of the workpiece 102. The first photodiode (PD1) 214 and the third photodiode (PD3) 225 detect reflected light from the workpiece 102.

  The super-resolution optical element 207 is an element for reducing the diameter of the beam spot formed on the surface of the workpiece 102. Specifically, an element that makes the cross section of the laser beam annular or a phase annular element or the like There is. As an element which makes the cross section of a laser beam ring-shaped, there are, for example, a donut-shaped light shielding plate and two axicons facing each other. The phase ring element is an optical element in which a light transmitting plate is stepped in the radial direction, and changes the phase in the radial direction of the cross section of the transmitted laser light.

  The semiconductor laser driving device includes a recording signal generation circuit 110, a laser power setting circuit 111, a laser driving circuit 112, and a clock signal generation circuit 119, and turns the pulse-like change in light intensity of the first semiconductor laser 201 into a turntable. It can be modulated according to the number of rotations of the rotation mechanism 101. Further, this semiconductor laser driving device adjusts the laser light intensity value at the high level of the laser light emitted in a pulse form from the first semiconductor laser 201 set in the laser power setting circuit 111 via the computer device 116. By doing so, the light intensity distribution of the beam spot can be adjusted.

  The laser power setting circuit 111 inputs a signal corresponding to the light intensity of the laser light output from the second photodiode (PD2) 206 as needed, and sets the intensity of the laser light emitted from the first semiconductor laser 201. This is a circuit for controlling the laser driving circuit 112 so as to have the intensity.

  Further, the optical system including the objective lens 210 is provided with a vibration compensation mechanism that compensates for the vertical vibration of the workpiece 102. This vibration compensation mechanism moves the objective lens 210 only in one direction of the focal direction. The shaft actuator 103a and an autofocus function using reflected light from the workpiece 102 are provided. The autofocus function includes a focus error signal generation circuit 105, an autofocus circuit 106, and a drive circuit 107.

  Note that the signal input to the focus error signal generation circuit 105 is a signal corresponding to the light intensity of the reflected light output from the first photodiode (PD1) 214 and the third photodiode (PD3) 225. It is the signal amplified by. The signal amplifying circuit 104 selects and inputs one of the signals output from the first photodiode (PD1) 214 and the third photodiode (PD3) 225 based on a command from the computer device 116. It is a circuit that amplifies at the amplification rate.

  Between the autofocus circuit 106 and the drive circuit 107 is a focus offset voltage application circuit 120 that applies a DC component voltage to a signal output from the autofocus circuit 106 via an adder 121. The DC component voltage (offset voltage) set in the focus offset voltage application circuit 120 can be set to an arbitrary value from the input device 118 via the computer device 116.

  By applying a DC component voltage (offset voltage) to the signal output from the autofocus circuit 106, the focal position of the laser beam almost on the surface of the workpiece 102 is moved in the vertical direction, and the surface of the workpiece 102 is moved. It is possible to change the light intensity distribution of the beam spot formed on the substrate. That is, by adjusting the offset voltage set in the focus offset voltage application circuit 120 by changing the value input from the input device 118, the light intensity distribution of the beam spot formed on the surface of the workpiece 102 is adjusted. Can do.

  When a predetermined ultrafine pattern is formed in the processing region of the processing target object 102 by the laser processing apparatus configured as described above, when the processing target object 102 is a heat-reactive material (for example, a platinum oxide film), The portion of the laser light that is irradiated with the laser beam is melted by a thermal reaction to form a concave pit, so that the light intensity distribution of the beam spot formed on the surface of the workpiece 102 is adjusted. By doing so, the shape of the pit can be adjusted.

  Further, as a function for evaluating the ultrafine pattern, a rotating polarizer 224 provided in front of the third photodiode (PD3) 225 in the optical processing head 103 and a rotating polarizer 224 attached to the optical processing head 103 are rotated. A rotation motor 103b to be rotated, a signal corresponding to the rotation position to the rotation motor 103b, a rotation polarizer control circuit 122 for controlling the rotation position of the rotation polarizer 224, and a signal output from the signal amplification circuit 104 And a signal level measurement circuit 109 that measures the level of the signal output from the reproduction signal generation circuit 108 and outputs the value as a digital signal to the computer device 116. .

  The rotating polarizer 224 is an element in which a polarizer that passes only light in one polarization direction rotates around the optical axis of reflected light. By rotating the rotary polarizer 224 and detecting the amount of light that has passed through each rotation angle, the polarization characteristics of the incident reflected light can be measured.

  The rotation polarizer control circuit 122 receives a signal corresponding to the rotation angle of the rotation polarizer 224 from the computer device 116, and the rotation polarizer control circuit 122 calculates the rotation position of the rotation motor 103b from the input rotation angle. A signal corresponding to the calculated rotational position is supplied to the rotary motor 103b.

  The reproduction signal generation circuit 108 amplifies and outputs the signals output from the respective divided portions of the third photodiode (PD3) divided by the signal amplification circuit 104 into at least four parts. This is a circuit that inputs all the amplified signals, generates a sum of signals as a reproduction signal, and outputs it to the signal level measurement circuit 109.

  The signal level measurement circuit 109 passes the input reproduction signal through a low-pass filter to make the signal level a substantially constant signal, and then captures the peak value of the signal as a digital signal at a predetermined interval, and captures the plurality of captured peak values. It is a circuit that averages and supplies a digital signal of this average value to the computer device 116.

  Next, based on FIG.1 and FIG.2, operation | movement of the laser processing apparatus of this invention is demonstrated. First, the values of the laser light intensity and the focus offset voltage are input from the input device 118. The input values are set in the laser power setting circuit 111 and the focus offset voltage application circuit 120 via the computer device 116, respectively. This value is a value that seems to be an optimum value for producing a predetermined ultrafine pattern on the workpiece 102, but this value is appropriately changed by evaluation of the ultrafine pattern described later. Next, the workpiece 102 is set on the turntable rotating mechanism 101 and the turntable rotating mechanism 101 is rotated. The rotation speed of the turntable rotating mechanism 101 is controlled by a spindle motor control circuit 113.

  The spindle motor control circuit 113 receives a pulse signal having a frequency corresponding to the rotation speed from an encoder 101 a in the spindle motor of the turntable rotation mechanism 101, and the calculated rotation speed is set in the spindle motor control circuit 113. The number of rotations of the turntable rotation mechanism 101 is controlled so that the number of rotations becomes the same. The rotation speed in the spindle motor control circuit 113 is set via the computer device 116 by inputting the rotation speed from the input device 118.

  Next, the radial position where the laser beam is first irradiated is input from the input device 118. As a result, the sled motor 115 operates, and the turntable rotating mechanism 101 moves in the radial direction and stops at the input radial position. The turntable rotating mechanism 101 is connected to a moving mechanism including a sled motor 115, and is moved in the radial direction by the rotation of the sled motor 115.

  Next, a radius position at which laser processing is to be ended is input from the input device 118. This value is stored in the computer device 116, and the computer device 116 calculates the radial position of the laser irradiation from time to time from the pulse signal from the encoder 115a of the thread motor 115 that is input as needed. When the position reaches the radial position at which laser processing is completed, the laser beam irradiation is stopped, and the driving of the sled motor 115 and the autofocus function are stopped.

  Regardless of this, if the recording signal input from the computer device 116 to the recording signal generation circuit 110 is finite, the signal output from the recording signal generation circuit 110 ceases or the laser light irradiation stops. Therefore, the driving of the sled motor 115 and the autofocus function may be stopped when the laser beam irradiation is stopped.

  Next, the radial interval of the workpiece 102 in each pattern (pit) of the ultrafine pattern is input from the input device 118. This value is used by the computer device 116 to set the rotation speed of the thread motor 115 in the thread motor control circuit 114 as will be described later.

  Next, the start of laser beam irradiation is instructed from the input device 118. As a result, all the circuits except the signal level measuring circuit 109 are operated, and the thread motor 115 has a predetermined interval in the radial direction of the workpiece 102 in each pattern (pit) of the ultrafine pattern. The laser light irradiation position rotates in such a manner that the laser beam irradiation position moves in the radial direction when viewed from the processing object 102, thereby producing an ultrafine pattern on the surface of the processing object 102.

  When the workpiece 102 is moved in the radial direction by the sled motor 115, the sled motor 115 is controlled by the sled motor control circuit 114 in its rotational position and number of revolutions. The thread motor control circuit 114 receives a pulse signal having a frequency corresponding to the number of rotations from an encoder 115 a in the thread motor 115, and the thread motor 115 until the calculated radial position becomes the radial position input from the input device 118. Rotate. The sled motor control circuit 114 controls the rotation speed of the sled motor 115 so that the rotation speed calculated from the pulse signal becomes the rotation speed set in the sled motor control circuit 114.

  The rotational speed in the thread motor control circuit 114 is the same as the rotational speed of the turntable rotating mechanism 101 input from the input device 118, but is the radial interval between the individual patterns (pits) of the ultrafine pattern input from the input device 118. Is calculated and set by the computer 116. The thread motor control circuit 114 controls the rotational position when the radial position is input from the input device 118, and controls the rotational speed after the rotation of the turntable rotating mechanism 101 and the laser light irradiation are started. I do.

  Laser light emitted from the first semiconductor laser 201 is converted into a parallel light beam by the collimator lens 202. Further, the first anamorphic prism 203 performs shaping so that the cross-sectional shape of the laser light is a perfect circle. The light beam that has passed through the first anamorphic prism 203 is polarized and separated by a PBS (polarization beam splitter) 204, and most of the light beam goes to the workpiece 102.

  A part of the light polarized and separated by the PBS 204 is condensed through the first convex lens 205 and is detected by the second photodiode (PD2) 206. The laser power setting circuit 111 and the laser driving circuit 112 use the signal corresponding to the detected light amount output from the second photodiode (PD2) 206 when the laser light emitted from the semiconductor laser 201 is at a high level. Auto power control with constant light intensity.

  The light beam that has passed through the PBS 204 passes through the super-resolution optical element 207. By passing this super-resolution optical element 207, the diameter of the beam spot formed on the surface of the workpiece 102 by the objective lens (OL) 210 can be reduced.

  3A and 3B are diagrams showing the light intensity distribution in the radial direction of the beam spot formed by the objective lens 210. FIG. FIG. 3A shows a case where the super-resolution optical element 207 is not provided, and FIG. 3B shows a case where the super-resolution optical element 207 is provided. As can be seen from this, when there is the super-resolution optical element 207, the light intensity distribution in the radial direction of the beam spot is narrowed (that is, the diameter is small). Therefore, further fine processing can be performed by passing the laser light through the super-resolution optical element 207.

  4 (a) and 4 (b) are diagrams showing a processing state of a pattern having a size equal to or smaller than the diameter of the beam spot with respect to the heat-reactive material processing object, and FIG. 4 (a) is a super-resolution optical element. FIG. 4B shows a case where the super-resolution optical element 207 is present. 4A and 4B show an embodiment in which a dot pattern is produced. As shown in FIG. 4A, as compared with the case where the super-resolution optical element 207 is not used, As shown in FIG. 4B, it can be seen that when the super-resolution optical element 207 is used, not only the dot pattern can be made minute but also it can be produced uniformly.

  The light beam that has passed through the super-resolution optical element 207 passes through the quarter-wave plate 208, is converted into circularly polarized light, and is irradiated onto the workpiece 102 through the rising mirror 209 and the objective lens (OL) 210. . The reflected light from the workpiece 102 is linearly polarized light whose polarization direction is 90 degrees different from that of the light beam that has passed through the quarter-wave plate 208 and the super-resolution optical element 207 via the objective lens (OL) 210. , Passes through the super-resolution optical element 207, and is reflected by the PBS 204 toward the reflection mirror 211.

  The light beam reflected by the reflecting mirror 211 is detected by the first photodiode (PD1) 214 via the second convex lens 212 and the cylindrical lens 213. A signal corresponding to the detected amount of light is output from the first photodiode (PD1) 214 to the signal amplifier circuit 104. The signal amplifier circuit 104, the focus error signal generation circuit 105, the autofocus circuit 106, and the drive circuit The single-axis actuator 103a is driven and controlled by the operation of 107, and the laser beam condensed on the surface of the workpiece 102 by the objective lens (OL) 210 is controlled so that the focal position follows the surface of the workpiece 102. Is done. The reflected light detection mechanism for performing the focus control is not limited to the astigmatism method using the second convex lens 212 and the cylindrical lens 213, and many methods such as a knife edge method can be employed.

  With the autofocus function, as shown in FIG. 5, it is possible to process even if the object to be processed is not a flat surface, and it is possible to directly process a free curved surface that has been difficult to process.

  The focus offset voltage application circuit 120 applies a DC component voltage (offset voltage) to the signal output from the autofocus circuit 106 via the adder 121. As described above, by changing the offset voltage, the position where the laser beam is focus-controlled near the surface of the workpiece 102 is changed in the vertical direction, and the light intensity of the beam spot formed on the workpiece 102 is changed. The distribution can be changed.

  The first semiconductor laser 201 emits laser light based on the signal waveform output from the laser driving circuit 112. The signal output from the laser drive circuit 112 is generated from the high level and low level pulse signals output from the recording signal generation circuit 110 and the signal corresponding to the laser light intensity at the high level output from the laser power setting circuit 111. The signal having a signal waveform is synchronized with the clock signal output from the clock signal generation circuit 119.

  Then, the laser drive circuit 112 starts outputting a signal when it detects an index signal (a signal generated every rotation) output from the encoder 101a. Since a signal output from a recording signal generation circuit 110, which will be described later, is a signal divided for each rotation, the laser driving circuit 112 detects an index signal output from the encoder 101a for each rotation. The signal output starts when

  The recording signal generation circuit 110 applies an arbitrary recording signal set by the computer device 116 to high-level and low-level pulses corresponding to the production portion and the non-production portion of the ultrafine pattern in the traveling direction of the beam spot of the workpiece 102. It is a circuit that converts it into a signal. The recording signal generation circuit 110 divides the pulse signal for each rotation and supplies the pulse signal to the laser driving circuit 112.

  The clock signal generation circuit 119 is a circuit that generates and outputs a signal in which a predetermined number of pulse signals output from the encoder 101a are one pulse. That is, the clock signal generation circuit 119 is a circuit that outputs a pulse signal that repeats a high level and a low level for each predetermined rotation angle of the turntable rotation mechanism 101.

  As a result, the laser light emitted from the first semiconductor laser 201 has a pulse waveform synchronized with the rotation of the turntable rotating mechanism 101, and is the same ultrafine as the workpiece 102 regardless of the rotation speed of the turntable rotating mechanism 101. A pattern can be produced.

  In addition, since the production of the ultrafine pattern is started after the index signal output from the encoder 101a is generated for each rotation, as shown in FIG. 6, the leading pattern (pit) is generated for each rotation. Can be aligned with high accuracy.

  When the radial position at which laser processing is finished or when the signal output from the recording signal generation circuit 110 is stopped, the computer device 116 includes a laser driving circuit 112, a recording signal generation circuit 110, a laser power setting circuit 111, and a thread motor control circuit. 115, the autofocus circuit 106, and the focus offset voltage application circuit 120 are stopped. Thereby, the laser beam irradiation is stopped, and the movement of the workpiece 102 in the radial direction is stopped.

  Next, the produced ultrafine pattern is evaluated to confirm whether the intended laser processing is performed. First, a radius position for evaluation is input from the input device 118. As a result, as described above, the sled motor is driven, and the turntable rotating mechanism 101 moves to a radial position where laser irradiation is performed. Then, laser irradiation for evaluation is instructed from the input device 118. Thereby, the computer device 116 starts the operation of the laser driving circuit 123 and the laser power setting circuit 124, and the laser light is emitted from the second semiconductor laser 215.

  Next, the signal amplification circuit 104 switches the signal to be selected for amplification to the signal from the third photodiode (PD3) 225, starts the operation of the signal level measurement circuit 109, and sends the reproduction signal to the computer device 116. Enter the signal level value. Further, the operation of the thread motor control circuit 114 is started, the workpiece 102 is moved in the radial direction by the thread motor 115 at a speed equivalent to that during laser processing, the operation of the autofocus circuit 106 is started, and laser processing is performed. Similarly, focus control is performed so that the focal position of the laser beam follows the surface of the workpiece 102.

  The fourth photodiode (PD4) 220 passes through the fourth convex lens 219 so that the intensity of the laser light emitted from the second semiconductor laser 215 becomes the laser intensity set in the laser power setting circuit 124. Although it is controlled by auto power control using the detected light intensity, this laser light has a constant laser light intensity and a laser light intensity at which the workpiece 102 is not subjected to laser processing. In addition, the laser beam emitted from the second semiconductor laser 215 is reflected by the dichroic mirror 221 so that the optical axis coincides with the laser beam at the time of laser processing. Are different.

  In this state, the input device 118 instructs to rotate the rotating polarizer 224. As a result, the computer device 116 activates the rotating polarizer control circuit 122 and sends a signal corresponding to the rotation angle to the rotating polarizer control circuit 122 at predetermined time intervals. Since the rotation polarizer control circuit 122 rotates the rotation motor 103b so as to have the instructed rotation angle, the rotation angle of the rotation polarizer 224 changes at predetermined time intervals and is input from the signal level measurement circuit 109 to the computer device 116. The signal level value of the reproduction signal to be changed varies depending on the rotation angle of the rotating polarizer 224.

  The signal level value of the reproduction signal input to the computer device 116 is a value corresponding to the amount of reflected light. The computer device 116 stores in advance the signal level value of the reproduction signal when the workpiece 102 is changed to a mirror or an object having a high reflectance for each rotation angle of the rotating polarizer 224. The signal level ratio obtained by dividing the level value by the stored signal level value is the same value as the light amount ratio of the reflected light. Since the light passing through the rotating polarizer 224 is only light having a polarization direction of one direction, the signal level value of the reproduction signal for each rotation angle of the rotating polarizer 224 is the polarization level of the reflected light in each polarization direction. This corresponds to the magnitude (that is, the vector value of each polarization direction).

  The computer device 116 displays the input signal level value and signal level ratio (amount ratio of reflected light) on the display device 117 for each rotation angle of the rotating polarizer 224. Based on this displayed value, the size of individual patterns (pits) of the ultrafine pattern and the width of pits in the radial direction of the workpiece 102 of the pattern are evaluated based on data obtained by experiments in advance.

  FIG. 8 is a diagram showing the relationship between the light quantity ratio of the reflected light whose polarization direction is the tangential direction of the object to be processed and the diameters of the individual patterns (pits) of the ultrafine pattern. As can be seen from FIG. 8, as the pattern (pit) diameter increases, the light quantity ratio decreases, and at one rotation angle of the rotating polarizer 224 displayed on the display device 117 (that is, one reflected light) From the light quantity ratio (in the polarization direction), the diameter of the pattern (pit) can be specified.

  FIG. 9 is a diagram showing a difference in signal level ratio (light quantity ratio) between two polarized lights having different polarization directions with respect to the pit width in the radial direction of the ultrafine pattern. As can be seen from FIG. 9, as the pit width increases, the difference in the light quantity ratio between the two polarization directions increases, and the rotational polarizer 224 displayed on the display device 117 has two rotational angles (ie, If the difference is calculated from the respective light quantity ratios (in the two polarization directions of the reflected light), the width of the pit in the radial direction of the workpiece 102 can be specified.

  As a result of evaluating individual patterns (pits) of the ultrafine pattern and confirming whether the intended laser processing is performed or not, if there is a deviation from the intended laser processing size, the laser power setting circuit The laser intensity value and the offset voltage value set in 112 and the focus offset voltage application circuit 120 are changed to values that can be used for intended laser processing, and the laser processing is performed again after returning to the beginning. If necessary, the number of rotations set in the spindle motor control circuit 113, the number of encoder pulses corresponding to one pulse of the clock signal set in the clock signal generation circuit 119, and the high level signal and low level set in the recording signal generation circuit 110 Change the duty ratio of the level signal.

  At this time, values to be set in the laser power setting circuit 112 and the focus offset voltage application circuit 120 are assumed based on data obtained through experiments.

  FIG. 10 is a diagram showing the relationship between the laser light intensity and the area of each pattern (pit) of the produced ultrafine pattern and the signal level based on the amount of reflected light. As can be seen from FIG. 10, when the laser beam intensity at the time of laser processing is increased, the signal level obtained in the ultrafine pattern evaluation is rapidly reduced to a certain laser beam intensity, but more slowly than that, at a certain level. It is constant. In addition, the areas of individual patterns (pits) of the ultrafine pattern have a reverse relationship. Therefore, since the laser beam intensity for making the individual patterns (pits) of the ultrafine pattern desired size can be known from this data, the result of the evaluation of the ultrafine pattern and the pits having the desired size can be obtained using this data. Therefore, the laser beam intensity can be assumed.

  Then, after laser processing is performed again, the evaluation laser beam is irradiated as described above to evaluate the ultrafine pattern again to check whether the intended laser processing is performed. By repeating this, the laser light intensity value and the offset voltage value set in the laser power setting circuit 112 and the focus offset voltage application circuit 120 can be optimized at the time of laser processing, and intended laser processing can be performed.

  In this way, if the processing object 102 is processed using the laser processing apparatus of the present invention and then the evaluation is repeated, an ultrafine pattern structure having a size equal to or smaller than the diameter of the beam spot can be obtained. Can be produced.

  The implementation of the present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the object of the present invention.

  In the above embodiment, the present invention is applied to a laser processing apparatus having a turntable (disk rotation type) rotation mechanism as shown in FIG. 7A. However, a drum as shown in FIG. The present invention can also be applied to a laser processing apparatus having a rotary type rotating mechanism.

  In the case of the disk rotation type, the thermal reaction type substrate mounted on the rotation mechanism is a flat disk, and in the case of the drum rotation type, it is a long substrate wound around the drum. These are properly used according to the usage pattern of the ultrafine pattern.

  In the above embodiment, in order to move the beam spot in the radial direction of the workpiece 102, the turntable rotating mechanism 101 is attached to a moving mechanism including the sled motor 115, and the workpiece 102 is radiused by this moving mechanism. However, the present invention is not limited to this as long as the beam spot can be moved in the radial direction of the workpiece 102. A moving mechanism including a thread motor 115 may be attached to the optical processing head 103, and the optical processing head 103 may be configured to move in the radial direction of the workpiece 102. Also by this, the same effect as the above embodiment can be expected.

  Moreover, in the said embodiment, the part used when evaluating the ultrafine pattern produced by carrying out the laser processing of the process target object 102 and the part used when the process target object 102 is laser-processed in the optical processing head 103 And the objective lens (OL) 210 is configured to be used in common by matching the optical axes of the irradiation laser beams in the two cases by the dichroic mirror 221, but the workpiece 102 is laser-processed, and the workpiece is processed. The present invention is not limited to this as long as an ultrafine pattern produced by laser processing 102 can be evaluated. The laser processing head 103 may be provided with objective lenses for laser processing and evaluation, respectively, and the laser processing portion and the evaluation portion may be completely independent, or the laser processing and evaluation optical heads. May be provided. Also by this, the same effect as the above embodiment can be expected.

  Further, in the above embodiment, as means for adjusting the light intensity distribution of the beam spot formed on the surface of the workpiece 102, two adjustments of the laser light intensity and the focus offset voltage are specifically performed. However, the present invention is not limited to this as long as the light intensity distribution of the beam spot can be adjusted. For example, when two axicons opposed to each other are used as the super-resolution optical element 207, the inner diameter of the annular zone in the cross section of the laser beam can be changed by changing the distance between the axicons. The diameter of the beam spot formed on the surface, that is, the light intensity distribution can be changed. In addition, a plurality of objective lenses having different numerical apertures (NA) are prepared in the optical processing head 103, and even if one of them can be selected, the diameter of the beam spot, that is, the light intensity distribution can be changed. . If these are added to the above embodiment, the means for adjusting the light intensity distribution of the beam spot is further increased, and a more optimal light intensity distribution of the beam spot can be set.

  In the above embodiment, the evaluation value of the ultrafine pattern produced on the workpiece is a signal level value, a signal level ratio (a ratio of the amount of reflected light), and a signal level ratio for each rotation angle of the rotating polarizer 224 ( In other words, the polarization characteristics of the reflected light are specifically described, but the invention is not limited to this as long as the ultrafine pattern can be appropriately evaluated. For example, an optical processing head with another configuration may be prepared, and the phase difference in the polarization direction of the reflected light may be detected so that the phase difference in the polarization direction can be used as an evaluation value, or the reflected light can interfere with the reference light. Then, the interference fringes may be detected, the wavefront aberration of the reflected light may be calculated, and this wavefront aberration may be used as an evaluation value. If these are added to the evaluation values of the above embodiment, it is possible to appropriately evaluate the ultrafine pattern.

It is a block diagram for demonstrating the laser processing apparatus of this invention. FIG. 2 is a block diagram of the optical processing head shown in FIG. It is a figure which shows the light intensity distribution of the radial direction of the beam spot formed with an objective lens, (a) shows the case where there is no super-resolution optical element, (b) shows the case where there exists a super-resolution optical element. Yes. It is a figure which shows the processing state of the pattern of the size below the diameter of the beam spot with respect to the workpiece of a heat reaction type material, (a) shows the case where there is no super-resolution optical element, (b) is a super-resolution optical element Shows when there is. It is a figure which shows the autofocus mechanism with respect to a free-form surface. It is a figure for demonstrating producing the same ultrafine pattern in a workpiece regardless of the rotation speed of a turntable rotation mechanism. (A), (b) is a figure which shows the example of the optical processing apparatus using a rotation mechanism, (a) is a turntable type | mold (disk rotation type), (b) has shown the drum rotation type. It is the figure which showed the relationship between the light quantity ratio of the light whose polarization direction is a tangent direction of a process target object among reflected light, and the diameter of each pattern (pit) of an ultrafine pattern. It is the figure which showed the difference of the signal level ratio (light quantity ratio) of two polarization | polarized-lights from which the polarization direction differs with respect to the width | variety of the pit of the radial direction of an ultrafine pattern. It is the figure which showed the relationship between the laser beam intensity | strength, the relationship of the area of each pattern (pit) of the produced ultrafine pattern, and the signal level based on the light quantity of reflected light.

Explanation of symbols

DESCRIPTION OF SYMBOLS 101 Turntable rotating mechanism 102 Processing object 103 Optical processing head 103a Single axis actuator 103b Rotating motor 104 Signal amplification circuit 105 Focus error signal generation circuit 106 Auto focus circuit 107 Drive circuit 108 Reproduction signal generation circuit 109 Signal level measurement circuit 110 Recording signal Generation circuit 111 Laser power setting circuit 112 Laser drive circuit 113 Spindle motor control circuit 114 Thread motor control circuit 115 Thread motor 116 Computer device 117 Display device 118 Input device 119 Clock signal generation circuit 120 Focus offset voltage application circuit 121 Adder 122 Rotating polarization Child control circuit 123 Laser drive circuit 124 Laser power setting circuit 201 First semiconductor laser 202 First collimator lens 203 First anamorphic prism 204 PBS
205 First convex lens 206 Second photodiode (PD2)
207 Super-resolution optical element 208 1/4 wavelength plate 209 Rising mirror 210 Objective lens 211 Reflecting mirror 212 Second convex lens 213 Cylindrical lens 214 First photodiode (PD1)
215 Second semiconductor laser 216 Second collimating lens 217 Second anamorphic prism 218 Beam splitter 219 Fourth convex lens 220 Fourth photodiode (PD4)
221 Dichroic mirror 222 Third convex lens 223 Cylindrical lens 224 Rotating polarizer 225 Third photodiode (PD3)

Claims (10)

In a laser processing apparatus for irradiating a processing target made of a heat-reactive substrate with laser light and forming a predetermined ultrafine pattern on the surface of the processing target,
Rotating means for rotating the workpiece;
The laser light emitted toward the rotation surface of the workpiece to be rotated by the rotating means is applied to the rotation direction of the workpiece to be irradiated with the laser light and the irradiation direction of the laser light. Moving means capable of relatively linear movement in a substantially vertical direction;
Irradiating means for emitting the laser beam toward the workpiece;
Optical means including an objective lens for condensing the laser light from the irradiation means on the surface of the object to be processed to form a beam spot;
Light detecting means for detecting reflected light from the surface of the beam spot irradiated on the workpiece;
Laser driving means capable of directly modulating the light intensity of the laser light;
Adjusting means for adjusting the light intensity distribution of the beam spot collected by the optical means,
A laser processing apparatus, wherein a nanostructure having a predetermined ultrafine pattern having a diameter equal to or smaller than the diameter of the beam spot is formed on the object to be processed by a beam spot having a light intensity distribution adjusted by the adjusting means.   The adjusting means includes a focus offset voltage applying means for applying a signal corresponding to an amount of shifting the focus of the laser beam from the surface of the object to be processed to at least a signal output by the autofocus function for driving the objective lens. The laser processing apparatus according to claim 1, further comprising:   It comprises an evaluation means for irradiating the nanostructure with a laser beam and evaluating the shape of the ultrafine pattern based on a reproduction signal generated from a signal based on reflected light output from the light detection means. The laser processing apparatus according to claim 1 or 2.   The evaluation means evaluates the shape of the ultrafine pattern by detecting the amount of reflected light from the ultrafine pattern, the light quantity ratio of reflected light, or the polarization characteristics of the reflected light based on the reproduction signal. The laser processing apparatus according to claim 3.   5. The laser processing according to claim 3, further comprising parameter value setting means for setting an adjustment parameter value of the adjusting means for adjusting the light intensity distribution based on an evaluation result by the evaluating means. apparatus. In a laser processing method of irradiating a processing target made of a heat-reactive substrate with a laser beam and forming a predetermined ultrafine pattern on the surface of the processing target,
A rotating step of rotating the workpiece by a rotating means;
The laser beam emitted toward the rotation surface of the workpiece to be rotated by the rotating means is applied to the rotation direction of the workpiece to be irradiated with the laser beam and the irradiation direction of the laser beam. A moving step for relatively linear movement in a substantially vertical direction,
An irradiation step of emitting the laser beam toward the workpiece by an irradiation unit;
A step of forming the beam spot by condensing the laser beam from the irradiation unit on the surface of the object to be processed by an optical unit including an objective lens;
A light detection step of detecting reflected light from the surface of the beam spot irradiated on the workpiece by a light detection means;
A laser driving step for directly modulating the light intensity of the laser light by a laser driving means;
An adjustment step of adjusting the light intensity distribution of the beam spot collected by the optical means by an adjustment means;
A laser processing method, wherein a nanostructure having a predetermined ultrafine pattern not more than the diameter of the beam spot is formed on the processing object by a beam spot having a light intensity distribution adjusted by the adjusting means.   The adjustment step includes a focus offset voltage application step of applying a signal corresponding to an amount of shifting the focal point of the laser beam from the surface of the workpiece to at least a signal output by the autofocus function for driving the objective lens. The laser processing method according to claim 6, further comprising:   The method further comprises an evaluation step of irradiating the nanostructure with laser light and evaluating the shape of the ultrafine pattern based on a reproduction signal generated from a signal based on reflected light output from the light detection means. Item 8. The laser processing method according to Item 6 or 7.   In the evaluation step, the shape of the ultrafine pattern is evaluated by detecting a light amount of reflected light from the ultrafine pattern, a light amount ratio of reflected light, or a polarization characteristic of reflected light based on the reproduction signal. The laser processing method according to claim 8. 10. The laser processing method according to claim 8, further comprising a parameter value setting step of setting an adjustment parameter value of the adjusting unit that adjusts the light intensity distribution based on an evaluation result of the evaluation step.

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