JP2006135251A - Laser crystallization equipment - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a crystallization equipment which carries out an initial crystallization which will not cause the breakage of peeling etc. near a phase-change material in an element preparing process, concerning the phase-change material for a phase-change non-volatile memory cell, and stabilizes its characteristics since the initiation of rewriting. <P>SOLUTION: A heating crystallization by a large output laser is carried out. The transfer of a silicon wafer 8 is basically to be a transfer in a single direction. A laser head 6 is made to reciprocate in a direction vertical to the transfer direction, and is irradiated by laser. In addition, rotational movement may be added. A start point positioning the wafer is located on a wafer-receiving circumference 9, and its part has a cutout where an operation portion lifting the wafer from the side enters. The laser spot area and irradiation interval are each to be within a predetermined range. A part of the equipment may be located inside a vacuum film forming apparatus. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a semiconductor manufacturing apparatus, and more particularly to a crystallization apparatus that performs initial crystallization of a phase change nonvolatile memory and a phase change transistor.

  The storage device (memory) surrounding the computing element (MPU) of the computer takes advantage of characteristics such as access speed, storage capacity (density), bit unit price, and commutability, and the target device becomes a system based on the design. Hierarchically arranged and configured. As individual characteristics, for example, SRAM and DRAM are capable of high-speed operation and are in a position to directly assist high-speed operation of the MPU, but are volatile so that stored data disappears if power supply is stopped. On the other hand, the EEPROM is relatively fast and is non-volatile so that the stored data will not be lost even if the power supply is stopped, but the bit unit price is very high. Hard disks and optical disks are non-volatile and have a low cost per bit, but have the respective characteristics that they cannot operate at high speed.

  Semiconductor memories such as FRAM (Ferroelectric RAM), PCRAM (Phase change RAM), and MRAM (Magnetoresistive RAM) are being researched and developed as next-generation memories that integrate the advantages of each memory. FRAM has already been commercialized.

  PCRAM is a phase change type non-volatile memory disclosed in, for example, Japanese Patent Publication No. 11-514150 and Japanese Patent Publication No. 2001-502848, and is also called OUM (Ovonic Unified Memory). PCRAM uses a phase change material for the memory holding part, and identifies and holds information by the difference in electric conductivity generated in each phase of the crystalline phase and the amorphous phase. As a feature, even if the phase change material is made relatively fine, the memory retention performance does not deteriorate. The electrical conductivity can vary by orders of magnitude, and intermediate levels, i.e. multivalued, are possible. It is possible to select a phase change material that is advantageous for high-speed switching, and it has the potential as an ideal memory such as non-volatility, high bit density, and high-speed access.

  According to the disclosed technology, PCRAM is a basic memory cell (1 bit) in which a MOS transistor is connected to a minute phase change material cell, and information recording and erasing is performed by passing a pulse current through the phase change material, This is done by self-heating due to the generated Joule heat. At the time of recording, a pulse current (set pulse) is applied so that the phase change material is heated to a temperature range where the phase change material is relatively low temperature and the crystallization speed is high, and the phase change material is crystallized. At the time of erasing, a pulse current (reset pulse) is applied so that the phase change material is rapidly cooled after high temperature, and the phase change material is made non-crystallized. The crystalline phase has a high electrical conductivity, and the amorphous phase has a relatively low electrical conductivity. During reproduction, information is read by applying a voltage to the phase change material and converting the flowing current to a voltage.

Japanese National Patent Publication No. 11-514150 JP-T-2001-502848

  FIG. 8 shows the basic structure of a PCRAM memory cell. The PCRAM has a structure in which a MOS transistor (not shown), a silicon oxide insulating layer 2, a lower electrode 4, a phase change material 1, and an upper electrode 3 are sequentially stacked on a silicon substrate (not shown). In the manufacturing process, the phase change material serving as the information holding unit is crystallized during the film formation by heating, or alternatively, after the film formation, the phase change material is heated and crystallized in an electric furnace. However, in the former substrate heating film formation, the substrate temperature at which the surface can be formed without roughening is limited to a narrow temperature range around 100 ° C., and the margin is very narrow and the temperature control is difficult. Further, in the latter post-film formation electric furnace heating, there is a problem that the adhesion with the adjacent laminated film is lowered and peeling is likely to occur. Furthermore, in both the substrate heating film formation and the post-film formation electric furnace heating, the crystallization state was different at the center and the edge of the substrate (silicon wafer) and lacked uniformity. In particular, the edge portion was poorly crystallized, and it was difficult to use because good electrical characteristics could not be obtained. In crystallization by substrate heating film formation and electric furnace heating after film formation, the crystal form is very different from the crystal form at the time of memory rewriting, and the specific resistance of the phase change film is small and stable from the first time when the number of rewrites is small. There was a problem that records could not be obtained.

  It is an object of the present invention to provide a phase change type nonvolatile memory crystallization apparatus that performs initial crystal without causing destruction such as peeling in the vicinity of a phase change material during an element manufacturing process and stabilizes characteristics from the beginning of rewriting. is there.

In order to achieve the above object, the phase change film is initially crystallized by irradiating the process substrate of the phase change memory at the stage where the phase change film is provided on the silicon substrate with laser light emitted from the high output laser. The area of the laser spot irradiated to the process substrate is 10 ⁻⁶ cm ² or more and 10 ⁻³ cm ² or less, and the substrate support portion and the substrate are arranged so that the laser irradiation time for each position on the process substrate is 0.1 μs or more and 1 ms or less. It is preferable to relatively drive the laser head. According to the laser initial crystallization apparatus of the present invention, high-density and appropriate irradiation energy can be applied to the phase change material of the phase change memory, and the entire phase change material of the phase change nonvolatile memory can be crystallized uniformly. It can be made. In addition, according to this apparatus, only the phase change material can be heated to the crystallization temperature in a short time, and the laminated film in the vicinity of the phase change material can be set in a set state without causing thermal damage due to volume change. The above-mentioned object can be achieved.

  If the irradiation conditions are changed concentrically depending on the distance from the center of the process substrate, it is possible to irradiate laser energy that is most suitable for each radial position in response to slight differences in the composition of the center and outer periphery of the substrate. In addition, good crystallization can be obtained on the entire surface without any positional difference between the central portion and the outer peripheral portion of the substrate, and local peeling can be prevented.

  Further, a mechanism for detecting crystallization by infrared light from the back surface of the substrate and means for controlling the laser output, the laser pulse frequency, the laser pulse duty, the transport speed of the substrate and the like based on the detection result may be provided. According to this configuration, it is possible to feedback-control the laser output and the substrate transport speed while actually measuring the temperature rise reaching the back surface of the substrate in real time, and a predetermined crystallization state can be obtained evenly over the entire surface of the silicon wafer. In addition, it is resistant to subtle changes in the surrounding environment and changes over time due to multiple operations, and stable crystallization can be obtained.

  Furthermore, when equipped with an autofocus control means that prevents the shape of the laser spot from changing on the silicon wafer surface, it is possible to irradiate laser light with a constant power density at any position on the silicon wafer surface as required. Crystallized state can be obtained.

  According to the present invention, a long and narrow crystal can be formed in the direction perpendicular to the film surface of the phase change material layer on the entire surface of the silicon wafer. Further, it is possible to prevent the silicon wafer from being scratched on the front and back surfaces. Furthermore, the irradiation conditions can be changed in response to concentric changes in film characteristics and adhesiveness after film formation, thereby preventing variations in element characteristics depending on the location on the silicon wafer and peeling of the peripheral portion.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

<Example 1>
FIG. 1 is a schematic view of an embodiment of a linear scanning laser crystallization apparatus according to the present invention.

  The laser head 6 is collected by a high-power semiconductor laser 4 that is a light source, a collimator lens 5B, a PBS 5A, an objective lens 5 that condenses the laser light, an actuator 19 that drives the objective lens 5 in the direction of the optical axis 5C, and the objective lens 5. It is comprised by the focus detector 10 which detects the focused focus point position. A wafer tray 9 on which a disk-shaped silicon wafer (a phase change memory process substrate on which a phase change film is provided on a silicon substrate) 8 is mounted is cut out with a diameter slightly lower than the diameter of the silicon wafer 8. The laser beam passing through the objective lens 5 is arranged so as to be orthogonal to the optical axis 5C of the laser beam. The wafer tray 9 can be freely moved two-dimensionally in the X-axis direction and the Y-axis direction while maintaining the right angle.

  An infrared light sensor 17 is attached to the surface opposite to the laser head 6 with the wafer tray 9 at the center, and the infrared light amount around the condensed laser spot 7 can be measured. Can be measured. The infrared sensor may be a one-point measurement type, but is more preferably a camera type that can actually measure the entire periphery including the laser spot 7. Furthermore, a type that can detect the temporal temperature change of the silicon wafer 8 without delay is more preferable. The infrared light sensor 17 is integrated with the laser head 6 so that the relative positional relationship with the laser spot 7 does not change even if the silicon wafer 8 moves in the X-axis direction or the Y-axis direction. The temperature around the laser spot 7 can be detected. The silicon wafer being processed is provided with a number of places where infrared light generated by the phase change film is easily transmitted to the substrate surface. Further, the laser head 6 and the infrared light sensor 17 integrated therewith are also movable, so that the position of the laser spot 7 irradiated on the silicon wafer 8 can be moved by driving the laser head 6. It has become.

  The laser driving circuit 11 can emit pulses, and can perform laser pulse driving with a frequency of 1 Hz to 10 MHz and a pulse width of 100 ns to 1 s. DC drive is also possible. Furthermore, the top output 31C and the bottom output 31D of the laser pulse light 31 can be arbitrarily set (see FIG. 3). The focus control circuit 12 has a feedback control function for correcting the focus shift by driving the actuator 19 based on the focus shift signal detected by the focus detector 10. The XY table control circuit 14 can drive the wafer tray 9 on a two-dimensional plane in the X-axis direction and the Y-axis direction, and can perform arbitrary positioning and arbitrary positioning in the X and Y directions. ing.

  The signal processing circuit 18 calculates from the transmittance whether the crystallized region has spread over almost the entire thickness of the phase change film. When the infrared light sensor 17 is a camera type, it has a function of processing detected image data, and only predetermined information can be converted into data. The microprocessor (MPU) 13 is connected to each main part of the laser drive circuit 11, the XY table control circuit 14, the signal processing circuit 18, and the focus control circuit 12, and performs a pre-programmed operation. The main parts can be controlled collectively.

In this embodiment, focus control is performed. However, if there is no change in the laser spot shape 7 at any position of the silicon wafer 8, or if the laser spot shape 7 does not affect the crystallization state, the focus control is performed. There is no need. Further, when high laser power density is not required, parallel light may be used without focusing by an objective lens or the like. The light source is not limited to a semiconductor laser, but may be a solid laser such as a YAG laser or a CO ₂ laser, or a gas laser.

  The scanning method of the laser beam on the wafer will be described with reference to FIG. This figure is for an arbitrary time during crystallization, the laser spot 29A moves in the Y direction 29, the left half of the silicon wafer 8 is the crystallized portion 26, and the right half is the uncrystallized portion 27. . Initially, the laser spot 29 is at the 22 position.

FIG. 2A is an explanatory diagram of a scanning method for linearly scanning the wafer tray in the X direction while continuously reciprocating the laser beam in the direction perpendicular to the longitudinal direction of the spot 29A, that is, in the front and back directions of FIG. . At this time, the locus drawn by the midpoint of the laser spot 29A always intersects at the same angle. The shape of the laser spot 29A is oval. The laser spot 29A is turned back as soon as it reaches the end of the region to be crystallized on the wafer 8. However, since the inertia is large when the entire optical head is driven, the trajectory is not a shape in which a straight line is turned back at an acute angle. Is slightly rounded. The speed and turn-back position are determined so that the beam spot (range up to 1 / e ² of the maximum power) always passes through any point in the region to be crystallized on the wafer at least once. It is also effective to perform scanning by controlling the feed rate of the wafer tray so that the center interval of the laser spots 29A crossing the axis in the X direction passing through the center of the wafer is constant.

  FIG. 2B is a diagram showing a trajectory drawn by the midpoint of the laser spot in the scanning method in which the laser spot 29A is scanned on the wafer by alternately moving the laser head 6 and the wafer tray 9. FIG. In the figure of the silicon wafer 8 being crystallized as viewed from the laser head 6 side, the horizontal direction is the X axis and the vertical direction is the Y axis. Laser light is emitted at a predetermined pulse frequency and output, and focus control is performed. By moving the silicon wafer 8 in the Y direction, the laser spot is scanned while crystallizing the silicon wafer 8 in the 23 directions. When the laser spot reaches the edge of the silicon wafer 8, the movement in the Y direction is stopped and the silicon wafer 8 is moved in the X direction 24 by a distance shorter than the laser spot width 28. After that, the laser spot is moved in the Y direction 25. The entire surface of the silicon wafer 8 can be crystallized by repeating the above operation and scanning the laser spot from the left surface of the silicon wafer so as not to generate an uncrystallized gap.

In this example, the laser spot area is 10 ⁻⁶ cm ² or more and 10 ⁻³ cm ² or less, and the pulse width (passage time in the range of 1 / e ² of the maximum power of the spot) is from 100 ns to 1 s. I was able to confirm. That is, when the experiment was performed while changing the shape of the laser spot to be irradiated and the passage time of the laser spot, the following results were obtained. The spot area was an experiment including two types of light spots including defocus. As a small spot, an effect was obtained up to 10 ⁻⁶ cm ² at 100 μm × 1 μm of a laser having an output of 2 W, and as a large spot to a spot of 10 ⁻³ cm ² at 3.5 mm × 30 μm of an output of 60 W. In the case of 2 × 10 ⁻⁶ cm ² or more and 10 ⁻⁴ cm ² or less, the resistance value was stabilized from the first rewriting irrespective of the conditions of the aging treatment before shipment. Irradiation time (time to pass one point on the disk in a state where a high power is output in the range up to 1 / e ² of the peak intensity of the light spot (a pulse is emitted in the case of pulse irradiation)) is 0.1 μs. As described above, the effect was obtained if the irradiation power was optimum, but it was difficult to prevent partial peeling of the interface due to heat when the irradiation power was 1 s or longer. Good characteristics with particularly good reproducibility were obtained at 1 μs or more and 1 ms or less.

  The linear scanning laser crystallization apparatus described here is easy to prevent the wafer from being scratched and has good irradiation efficiency. Although the laser head 6 and the infrared light sensor 17 are moved in the Y direction and the silicon wafer 8 mounted on the wafer tray 9 is moved in the X direction, the laser head 9 and the infrared light sensor 17 are not limited to this. Is provided with a laser head XY plane moving mechanism (not shown) for moving both in the X-axis direction and the Y-axis direction, and the entire surface of the silicon wafer 8 may be crystallized in the same manner as the laser spot scanning described with reference to FIG. . Further, the laser head 6 and the infrared light sensor 17 are movable only in the X-axis direction, and the silicon wafer 8 mounted on the silicon tray 9 is movable only in the Y-axis direction, so that the entire surface of the silicon wafer is similar to the laser spot scanning described with reference to FIG. It is also possible to crystallize. It is also possible to move the light spot in a spiral by moving the optical head spirally from the center to the outside or from the outside to the center.

  FIG. 3 is a diagram for explaining an example of laser irradiation time control by the infrared light sensor 17. FIG. 3B shows the temporal change of the laser output P. In FIG. 3A, the horizontal axis represents the temperature T immediately below the laser spot detected from the back surface in the region where the infrared light of the silicon wafer transmits the infrared light of the silicon wafer at a predetermined timing with respect to the irradiation laser. The vertical axis represents the laser irradiation time τ during execution of crystallization. Here, the top output 31C and the pulse period 31A of the laser beam 31 output in a pulse manner are fixed to a predetermined value, and the scanning speed is also fixed to a predetermined value. The laser irradiation time τ is the pulse width 31B. A curve 30 is a curve set in advance in a memory (not shown). If the detected temperature exceeds a predetermined value, the pulse width is narrowed, and if it falls below, it is widened. Regarding the silicon wafer temperature on the horizontal axis, a detection temperature corresponding to the crystallization reaching the interface opposite to the laser beam incident side is actually obtained, and the laser irradiation time is determined from FIG. Instead of the pulse width 31B, that is, the laser pulse duty, the laser output and the laser pulse frequency may be changed, or the moving speed of the wafer tray and the moving speed of the laser head may be controlled.

  The MPU 13 recognizes the silicon wafer back surface temperature T just under the crystallization execution spot detected by the infrared light sensor 17 and instructs the laser drive circuit 11 of the pulse width 31B based on the curve 30 drawn from the memory. After that, the laser drive circuit 11 drives the laser according to the curve 30 under the instruction of the MPU 13. Eventually, the laser emission of the curve 30 becomes possible. The curve 30 changes depending on the thermal characteristics of the silicon wafer 8 and the easiness of crystallization, and the basic characteristics of the silicon wafer 8 can be acquired and determined so as to obtain a predetermined crystallization state.

  Here, the case of the laser irradiation time τ (31B) is shown as the control target. However, the top output 31C of the laser beam output in a pulse manner, the pulse period 31A, or the scanning speed may be set as the control target. However, the laser irradiation time τ (31B) of the laser beam output in a pulse form although it is plural, the top output 31C, the pulse period 31A, or plural scanning speeds may be controlled. In any case, in any combination, a target curve for obtaining a predetermined crystal state may be acquired and recorded in the memory in advance.

  Furthermore, the silicon wafer back surface temperature T immediately below the laser spot detected by the infrared light sensor 17 is not limited to one, and if a plurality of temperatures such as front and rear in the laser spot scanning direction including directly under the laser spot are detected, the temperature is further increased. Fine control is possible. In any case, by performing feedback control of laser output and silicon wafer conveyance while actually measuring the temperature T reaching the back surface of the silicon wafer in real time, a predetermined crystallization state can be obtained evenly on the entire surface of the silicon wafer. In addition, it is resistant to subtle changes in the surrounding environment and changes over time due to multiple operations, and stable crystallization can be obtained. It is more preferable to control laser output by adding not only the silicon wafer back surface temperature T but also laser spot position (XY position) information on the silicon wafer.

  Next, the wafer tray will be described in detail. FIG. 4 is a schematic view of a wafer tray that supports a silicon wafer. 4B is a view of the wafer tray 35 on which the silicon wafer 8 is mounted as viewed from the laser irradiation side, that is, the laser head side, and FIG. 4A is a cross-sectional view taken along the line AB.

  The wafer tray 35 has a ring shape. The laser head side of the inner diameter portion is slightly larger than the silicon wafer 8, and the side farther from the laser head is slightly smaller than the silicon wafer 8, and is entirely tapered. Even when the silicon wafer 8 is mounted, it is supported by a part 40 of the tapered inner diameter portion and has a bottom surface. In addition, an infrared light sensor can be installed on the surface opposite to the laser head, that is, on the back surface of the silicon wafer, and the silicon wafer back surface temperature can be measured. The material of the wafer tray 35 is preferably made of Teflon. If it is made of Teflon, it has excellent mechanical shock mitigation, heat insulation and insulation properties, and an effect that does not adversely affect the silicon wafer 8 can be obtained, and heat radiation due to wafer tray contact can also be avoided at the edge 40 of the silicon wafer. A crystallization state equivalent to that of the silicon wafer central portion can be obtained. The material of the wafer tray 35 may not be all made of Teflon, and at least the portion 40 in contact with the silicon wafer 8 may be made of Teflon.

  On the laser tray side of the wafer tray 35, three notches 37, 38, 39 are provided at intervals of 120 degrees. The notch has a depth that allows at least the mounted silicon wafer 8 to be confirmed from the side. By providing three notches, for example, if a silicon wafer operating mechanism with three claws is used, the silicon wafer 8 can be sandwiched from the edge to the center, and the silicon wafer 8 can be detached from the wafer tray 35 and conveyed. It becomes. The silicon wafer 8 can be easily carried in and out without contacting the front and back surfaces of the silicon wafer. The number of cutouts is not limited to three and may be other than that. In FIG. 5, the entire circumference of the outer periphery of the silicon wafer 8 is in contact with the wafer tray 35 with a line. 8 can also be supported. Further, the number of protrusions is not limited to three and may be other than that. In this embodiment, a circular silicon wafer is used. However, the wafer tray must match each shape. Although the risk of dropping increases, the wafer tray may not be provided and the wafer may be supported and conveyed at three points so as to be supported by a fingertip.

  The scanning of the laser spot is not limited to a straight line, and may be rotational scanning. Hereinafter, the rotational scanning will be described in detail. FIG. 5 is a schematic view of a rotary scanning laser crystallization apparatus. The laser head 6, the infrared light sensor 17, the laser drive circuit 11, the focus control circuit 12, the signal processing circuit 18, and the MPU 13 are the same as those described in FIG.

  The wafer tray 46 is circular and has a structure that can rotate around the center of the wafer tray 46 as a rotation center 48C. A rotation driving motor 51 is attached to the outer peripheral portion of the wafer tray 46, and the outer peripheral portion 53 of the wafer tray 46 can be driven by the rotating portion 52, so that the wafer tray 46 can be rotated. The rotation driving motor 51 can be rotated at an arbitrary number of rotations by a motor control circuit 48B. Further, the motor control circuit 48B is connected to the MPU 13 and performs rotation control in real time. The laser head 6 can move on the diameter of the wafer tray 46 as indicated by an arrow 50, and the laser spot 48 can freely move on a straight line 54 passing through the rotation center 48 </ b> C of the wafer tray 46. The infrared light sensor 17 moves as indicated by an arrow 49 in conjunction with the movement of the laser head 6 and always captures the back surface of the silicon wafer 8 on which the laser spot 48 is formed. The MPU 13 can move the laser spot 48 at an arbitrary speed and position it at an arbitrary position via a head driving circuit (not shown). MPU can control each main part at once. The wafer tray is supported by three radial arms from a rotation axis passing through the central axis 48C. Infrared light is temporarily interrupted when passing through the arm, but it does not matter because it is a short time.

  FIG. 6 is an explanatory diagram of rotational scanning. Here, it is assumed that the rotation center of the wafer tray 46 and the center 66 of the circular silicon wafer 8 coincide. While rotating around the center 66 of the silicon wafer 8, the laser beam is emitted at a predetermined pulse frequency and output, and the focus control of the laser spot 61 is performed, and the arrow is directed from the outer periphery to the inner periphery of the silicon wafer 8. Move as shown. The laser spot 61 can be crystallized from the outer periphery of the silicon wafer 8 while drawing a spiral. At this time, the rotational speed of the silicon wafer 8 and the speed of the laser spot 61 are controlled in conjunction so that an uncrystallized gap does not occur. A crystallized portion 63 is shown on the outer periphery of the silicon wafer, and an uncrystallized portion 62 is shown on the inner periphery of the silicon wafer.

  FIG. 7 is a diagram showing laser irradiation and silicon wafer rotation speed depending on the radius from the silicon wafer rotation center. When the rotation speed of the silicon wafer is constant (CAV), it is preferable that the laser output is larger as the laser spot is positioned on the outer periphery as shown in FIG. The control target may be the laser pulse period 31A or the laser pulse width 31B. When the laser output is constant, as the laser spot is positioned on the outer periphery as shown in FIG.

  When it is necessary to change the irradiation conditions and linear velocity according to the radius, rotational scanning is effective.Especially, when there is a concentric non-uniformity depending on the radius of the silicon wafer, each radius value is Crystallization can be performed under optimum conditions, and as a result, the entire silicon wafer can be crystallized uniformly. However, this method may cause damage to the back surface and side surface of the silicon wafer as compared to linear wafer feeding in the horizontal uniaxial direction. As described with reference to FIG. 1, if the laser output is feedback controlled while measuring in real time whether or not crystallization has reached the backside of the silicon wafer by the infrared light sensor 17, a predetermined crystallization state is formed on the entire surface of the silicon wafer. Obtained without bias. In addition, it is resistant to subtle changes in the surrounding environment and changes over time due to multiple operations, and stable crystallization can be obtained. In this case, if it is difficult to provide only a layer that transmits infrared light between the silicon wafer and the phase-changing chalcogenide material layer, the accuracy of slight reflectance from the chalcogenide layer surface side The determination may be made based on a high measured value, an ultrasonic reflectance, or a measured value of electrical resistance.

  In the embodiment shown in FIGS. 1 and 5, the laser head 6 is disposed above the silicon wafer 8, that is, at a position higher than the silicon wafer 8 when the vertical direction is used as a reference. It is preferable that the laser head 6 be disposed below the silicon wafer 8. Further, the gap between the silicon wafer 8 and the laser head 6 and the gap between the silicon wafer 8 and the infrared light sensor 17 may be partitioned by a transparent plate. Furthermore, the entire silicon wafer and wafer tray, or the laser head, silicon wafer, wafer tray, and infrared light sensor may be installed in a vacuum film-forming apparatus, or installed in a container containing a specific gas. May be.

  After laser crystallization as described above, the phase change material of the silicon wafer was observed with a transmission electron microscope. As a result, a vertically long crystal having a width smaller than 100 nm and a width of about 20 to 50 nm was observed. In this case, since the maximum width of the lower electrode was smaller than about 80 nm, the device characteristics were not varied depending on the relative positional relationship between the crystal and the lower electrode, and a good device was obtained.

<Example 2>
The configuration of the apparatus is the same as that of Example 1, but the silicon wafer and the transport mechanism were housed in one chamber of a sputtering film forming apparatus having a plurality of vacuum chambers. The optical head was outside the vacuum chamber and irradiated with laser light through a glass window that could change the beam spot position. The optical head may be placed in a vacuum, and a power cable and a cooling water pipe may be connected from outside the vacuum.

  FIG. 9 is a schematic view of a sputtering apparatus having a laser irradiation chamber. The disk is set in the center of the sputtering chamber during film formation and rotated. Depending on the sputtering chamber, film formation can be performed from two or three targets. When the film formation is finished, the disk is opened one by one in the direction of the arrow by opening a partition wall in the middle. One chamber of the sputtering apparatus is a dedicated chamber for laser irradiation, and laser light is irradiated from outside the vacuum through an irradiation window.

1 is a schematic diagram of a linear scanning laser crystallization apparatus. The figure explaining linear scanning. The figure explaining laser irradiation time control by an infrared-light sensor. Schematic of the tray which supports a silicon wafer. 1 is a schematic view of a rotary scanning laser crystallization apparatus. Explanatory drawing of rotation scanning. The figure explaining the laser irradiation and silicon wafer rotation speed depending on the radius from a silicon wafer rotation center. The basic structure figure of the memory cell of PCRAM. Schematic of a sputtering apparatus having a laser irradiation chamber.

Explanation of symbols

4: semiconductor laser, 5: objective lens, 6: laser head, 7: laser spot, 8: silicon wafer (process substrate of the phase change memory at the stage where the phase change film is provided on the silicon substrate), 9: wafer tray, 17: Infrared light sensor, 19: Actuator, 51: Motor for rotation drive

Claims (11)

A laser light source;
A substrate support for holding a process substrate of a phase change memory at a stage where a phase change film is provided on the silicon substrate;
A laser head that converges and irradiates a laser beam emitted from the laser light source on a phase change film on a silicon substrate held by the substrate support;
An initial laser crystallization apparatus, wherein the phase change film is initially crystallized by laser irradiation. 2. The laser initial crystallization apparatus according to claim 1, wherein the laser light emitted from the laser head to the process substrate held on the substrate support has a spot area of 10 ⁻⁶ cm ² or more and 10 ⁻³ cm ² or less. An initial laser crystallization apparatus characterized in that the substrate support and the laser head are driven relatively so that the laser irradiation time for each position on the process substrate is 0.1 μs or more and 1 ms or less.   3. The laser initial crystallization apparatus according to claim 2, further comprising an autofocus mechanism that prevents the shape of the laser spot from changing on the process substrate held by the substrate support.   2. The laser initial crystallization apparatus according to claim 1, wherein the substrate support portion includes a substrate receiving portion into which a claw of a wafer operation mechanism for attaching and detaching a process substrate can be inserted.   2. The laser initial crystallization apparatus according to claim 1, further comprising a film forming apparatus having a vacuum chamber having a transparent window, wherein the substrate support portion is provided in the vacuum chamber, and the laser head is provided outside the vacuum chamber. A laser initial crystallization apparatus characterized by the above. A laser light source;
A substrate support for holding a process substrate of a phase change memory at a stage where a phase change film is provided on the silicon substrate;
A laser head that converges and irradiates a laser beam emitted from the laser light source on a phase change film on a process substrate held by the substrate support;
A relative driving means for relatively driving the substrate support portion and the laser head;
An initial laser crystallization apparatus, wherein the phase change film is initially crystallized by laser irradiation.   7. The laser initial crystallization apparatus according to claim 6, wherein the relative drive means includes means for driving the substrate support portion in one direction and means for reciprocating the laser head in a direction intersecting the drive direction of the substrate support portion. A laser initial crystallization apparatus comprising:   7. The laser initial crystallization apparatus according to claim 6, wherein the relative driving means includes means for rotationally driving the substrate support portion and means for driving the laser head in the direction of the rotation center of the substrate support portion. Laser initial crystallization equipment.   9. The laser initial crystallization apparatus according to claim 8, wherein the irradiation condition of the laser beam is changed concentrically depending on the distance from the center of the process substrate held by the substrate support. A laser light source;
A substrate support for holding a process substrate of a phase change memory at a stage where a phase change film is provided on the silicon substrate;
A laser head that converges and irradiates a laser beam emitted from the laser light source on a phase change film on a process substrate held by the substrate support;
Relative driving means for relatively driving the substrate support and the laser head;
An infrared light sensor aiming at the back side of the laser beam irradiation position of the process substrate on the opposite side of the laser head with respect to the substrate support portion;
A control unit that controls the output of the laser light source, the laser pulse frequency, the laser pulse duty, and / or the driving speed of the substrate support unit or the laser head by the relative driving unit based on the output of the infrared light sensor. ,
An initial laser crystallization apparatus, wherein the phase change film is initially crystallized by laser irradiation.   11. The laser initial crystallization apparatus according to claim 10, further comprising a memory storing a relationship between an output of the infrared light sensor and a control amount by the control unit.

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