JP2008277599A - Laser annealing method and laser anneal apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain the annealing time sufficient for recovering crystallinity of a part where ions are implanted and reducing the junction depth, without having to use many laser light sources, when forming a very shallow junction. <P>SOLUTION: A pulse laser beam 1 is oscillated in a pulse laser oscillator 12, a surface layer part where the ions are implanted is irradiated with the pulse laser beam 1, on the condition of not melting the surface layer, and the surface layer part is heated by an auxiliary heating means 19, at least until 1 microsecond elapses from the time of starting each irradiation, at every irradiation with the pulse laser beam 1 in parallel with the irradiation with the pulse laser beam 1. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a laser annealing method and a laser annealing apparatus, and more particularly to a technique effective for forming an ultra shallow junction of a MOS field effect transistor.

  In a MOS field effect transistor (hereinafter referred to as MOSFET), an impurity diffusion region adjacent to the source / drain region and having a shallow depth from the substrate surface is called an ultra-shallow junction (or extension region). The ultra-shallow junction serves to prevent a gate deterioration phenomenon due to generation of a high electric field when the FET is operated. In order to form the ultra-shallow junction of the MOSFET, an impurity implantation step of implanting impurities such as arsenic (As) ions, phosphorus (P) ions, boron (B) ions, etc. into the silicon wafer and electrically activating the impurities At the same time, a heat treatment step is required to recover the crystallinity of the portion into which the impurity is implanted. The latter heat treatment step is usually called activation annealing. In conventional activation annealing, an annealing method using a halogen lamp or a xenon flash lamp has been adopted.

In recent years, with the high integration of semiconductor integrated circuits due to the miniaturization of MOSFETs, the demand for ultra-shallow junctions of MOSFETs has become strict, and in order to put ultra-fine MOSFETs with technology nodes of 65 nm or less into practical use, low resistance, In addition, a technique for forming an extremely shallow junction with a junction depth of less than 20 nm is required.
However, since the annealing time (heating time) of the halogen lamp described above is several seconds and the annealing time of the xenon flash lamp is several milliseconds, both the annealing time is long and there is a problem that impurities are diffused to a deep region.

On the other hand, laser thermal annealing (LTP) and laser spike annealing (LSA) using a laser are promising as a technique for realizing the above-described ultrafine MOSFET (Non-patent Documents 1 and 2 below). reference).
In LTP, a pulse laser is used as a light source. The heating time is on the order of nanoseconds, and the surface layer part is locally melted by heating to a temperature higher than the melting point of silicon to re-grow crystals. The diffusion rate of impurities in molten silicon is several orders of magnitude higher than the diffusion rate in solid silicon. For this reason, the impurities are almost uniformly dispersed in the molten silicon. As a result, the impurity diffusion region can be made extremely shallow. However, LTP has problems such as generation of defects during crystal regrowth and the need for an amorphization process called PAI.

In LSA, a continuous wave (CW) laser is mainly used as a light source. Since the heating temperature is below the melting point of silicon, the surface of the silicon substrate does not melt. However, the CW laser has a problem in productivity because sufficient power is not realized in a wavelength band (visible to ultraviolet region) having a low absorption rate with respect to silicon.
On the other hand, the following Non-Patent Document 3, Patent Document 1, and Patent Document 2 propose a technique for performing LSA with a pulse laser in the ultraviolet and visible regions.

  It can be seen from Non-Patent Document 3 that if the pulse width is long, activation of impurities and recovery of crystallinity can be achieved without melting. This is because sufficient time is given for the activation of impurities and the recovery of crystallinity. Non-Patent Document 2 reports that microsecond order annealing is required in the non-melting process.

The techniques of Patent Documents 1 and 2 attempt to realize a microsecond annealing time by spatially synthesizing pulsed laser light from a solid-state laser light source to increase the effective pulse width.
However, in the spatial synthesis method of pulsed laser light disclosed in Patent Documents 1 and 2, in order to obtain an annealing time of the order of microseconds using a pulsed laser having a pulse width of 100 nanoseconds or less, a large number (for example, 10 Therefore, the feasibility is poor from the viewpoint of apparatus cost.

Nikkei Microdevice, November 2004, pp. 50-57 Solid State Technology, July, 2003 “Resers for thermal annealing” Thin Solid Films Volumes 453-454, 1 April 2004, pp. 145-149 Japanese Patent No. 3530484 JP 2006-156784 A

  The present invention has been made in view of the above-described problems. In forming an ultra-shallow junction, the crystallinity of the ion-implanted portion is recovered and the junction depth is reduced without using a large number of laser light sources. It is an object of the present invention to provide a laser annealing method and a laser annealing apparatus capable of obtaining an annealing time necessary and sufficient for the above.

In order to solve the above problems, the laser annealing method and laser annealing apparatus of the present invention employ the following means.
The present invention relates to a laser annealing method for irradiating and annealing a surface layer portion into which ions as impurities of a semiconductor substrate are implanted by irradiating a pulse laser beam, wherein the surface layer portion oscillates a pulse laser beam from a pulse laser oscillator. The surface layer portion is irradiated with the pulse laser light under a condition that does not melt, and in parallel with the irradiation of the pulse laser light, at least 1 microsecond has elapsed from the start of each irradiation of the pulse laser light. Meanwhile, the laser annealing method is characterized in that the surface layer portion is heated by auxiliary heating means.
Further, the present invention is a laser annealing apparatus that irradiates and anneals a surface layer portion into which ions as impurities of a semiconductor substrate are implanted, and has a pulse laser oscillator that oscillates the pulse laser light, A laser irradiation apparatus that irradiates the surface layer portion with the pulsed laser light; and an auxiliary heating unit that heats the surface layer portion of the semiconductor substrate. The surface layer portion oscillates the pulse laser light from the pulse laser oscillator. The surface layer portion is irradiated with the pulse laser light under a condition that does not melt, and in parallel with the irradiation of the pulse laser light, at least 1 microsecond has elapsed from the start of each irradiation of the pulse laser light. The laser annealing apparatus is characterized in that the surface layer portion is heated by auxiliary heating means.

  According to the above method and apparatus, while assisting the heating of the surface layer portion by the auxiliary heating means, the surface layer portion is irradiated with the pulsed laser light, so that the escape of heat in the thickness direction of the surface layer portion is suppressed, The rate of temperature decrease of the surface layer portion after irradiation with the pulse laser beam can be slowed. As a result, the effective annealing time can be extended to at least 1 microsecond or more. Therefore, it is necessary to restore the crystallinity of the ion-implanted portion and reduce the junction depth without using a large number of laser light sources by appropriately setting the heating temperature of the surface layer by the auxiliary heating means. Sufficient annealing time can be obtained.

The present invention also relates to a laser annealing method for annealing by irradiating a surface layer portion into which ions as impurities of a semiconductor substrate are implanted with pulsed laser light, wherein N is a natural number of 2 or more and N pulse lasers Pulse laser light is oscillated from an oscillator, pulse laser light from each pulse laser oscillator is synthesized on the same optical path, and n is a natural number less than N excluding 0, from oscillation of pulse laser light by the nth pulse laser oscillator Pulse laser light is oscillated from the (n + 1) -th pulse laser oscillator with a predetermined time difference, and the surface layer part is sequentially irradiated with the pulse laser light on the condition that the surface layer part does not melt, and in parallel with the irradiation of the pulse laser light At least 1 microsecond has elapsed from the start of each irradiation of the pulse laser beam from the first pulse laser oscillator. During the period, the surface layer portion is heated by the auxiliary heating means, and the temperature of the surface layer portion heated by the irradiation of the pulse laser beam from the nth pulse laser oscillator is determined by the auxiliary heating means. The laser annealing method is characterized in that the time difference does not decrease to the heating temperature of the surface layer portion.
The present invention is also a laser annealing apparatus for irradiating a surface layer portion into which ions as impurities of a semiconductor substrate are implanted by irradiating pulse laser light, and oscillating pulse laser light with N being a natural number of 2 or more. A laser irradiation apparatus for irradiating the surface layer portion with the pulse laser light, the laser irradiation apparatus having N pulse laser oscillators to be combined and a combining means for synthesizing the pulse laser light from each pulse laser oscillator on the same optical path; An auxiliary heating means for heating the surface layer portion, wherein (n + 1) -th pulse laser with a predetermined time difference from oscillation of pulse laser light by the n-th pulse laser oscillator, where n is a natural number less than N excluding 0 A pulsed laser beam is oscillated from an oscillator, and the surface layer part is sequentially irradiated with the pulsed laser beam on a condition that the surface layer part is not melted. In parallel with the irradiation, at least the surface layer portion is heated by the auxiliary heating means until 1 microsecond has elapsed since the start of each irradiation of the pulse laser beam from the first pulse laser oscillator. The predetermined time difference is a time difference at which the temperature of the surface layer portion heated by irradiation with pulse laser light from the nth pulse laser oscillator does not decrease to the temperature of heating of the surface layer portion by the auxiliary heating means. This is a laser annealing apparatus.

  According to the above method and apparatus, the pulsed laser beams from the plurality of pulse laser oscillators are sequentially irradiated with the above time difference while assisting the heating of the surface layer portion by the auxiliary heating means, so that the effective annealing time is further extended. Can do.

  Further, in the above method and apparatus, the auxiliary heating means performs intermittent heating, and the heating time per heating corresponds to a plurality of pulse intervals of the pulse laser beam. The heating temperature of the surface layer portion by the auxiliary heating means is set to a temperature range in which the diffusion rate of ions in the surface layer portion does not exceed a predetermined value depending on its own heating.

  When the auxiliary heating means performs intermittent heating, and the heating time per heating corresponds to a plurality of pulse intervals of the pulse laser beam, the temperature of the auxiliary heating is the diffusion of ions. If it is too high from the viewpoint of speed, ions diffuse to a deep region. Therefore, by setting the temperature of the auxiliary heating to a temperature range in which the diffusion rate of ions in the surface layer portion does not exceed a predetermined value depending on the heating of itself, it is possible to prevent ions from diffusing to a deep region.

  Moreover, in the said method and apparatus, the heating temperature of the said surface layer part by the said auxiliary heating means shall be 600 degrees C or less.

  Thus, by setting the temperature of auxiliary heating by the auxiliary heating means to 600 ° C. or less, the diffusion rate of ions in the surface layer portion by auxiliary heating substantially contributes to annealing for crystallinity recovery and ion activation. Therefore, an extremely shallow junction with a shallow junction depth can be formed.

  According to the present invention, when forming an ultra-shallow junction, an annealing time necessary and sufficient to recover the crystallinity of the portion where the impurity is implanted and to reduce the junction depth without using a large number of laser light sources. An excellent effect that it can be obtained.

  Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. In addition, the same code | symbol is attached | subjected to the common part in each figure, and the overlapping description is abbreviate | omitted.

[First Embodiment]
FIG. 1 is a diagram showing an overall schematic configuration of a laser annealing apparatus 10A according to the first embodiment of the present invention.
As shown in FIG. 1, the laser annealing apparatus 10 </ b> A is an apparatus for irradiating the surface layer portion into which the impurity of the semiconductor substrate 3 is implanted with the pulsed laser light 1 and annealing, and a pulse for oscillating the pulsed laser light 1. A laser irradiation device 11 having a laser oscillator 12 and irradiating the surface layer portion with the pulse laser beam 1 and an auxiliary heating means 19 for heating the surface layer portion of the semiconductor substrate 3 are provided.

The semiconductor substrate 3 is, for example, a silicon wafer, and the impurities are, for example, arsenic (As) ions, phosphorus (P) ions, boron (B) ions, and the like.
The pulse laser oscillator 12 is not particularly limited as long as it can oscillate the pulse laser beam 1. Examples of such a pulse laser oscillator 12 include excimer lasers, solid lasers such as YAG, YLF, and YVO ₄ , semiconductor lasers, and CO ₂ lasers. More specifically, an excimer laser having a wavelength of 248 nm or 308 nm, a YAG laser having a wavelength of 1064 nm, 532 nm or 355 nm, a semiconductor laser (laser diode) having a wavelength of 600 nm to 1000 nm, and a CO ₂ laser having a wavelength of 10.6 μm are exemplified. In particular, solid-state lasers such as YAG laser, YLF laser, and YVO ₄ laser have less variation in laser output than excimer lasers that are gas lasers, and are solid and easy to handle and maintain, and have high reliability. And so on.

The laser irradiation apparatus 11 further includes a beam shaping optical system 20 that shapes the pulsed laser light 1 into a beam having a cross-sectional shape on the surface of the semiconductor substrate 3 (hereinafter referred to as “linear beam”). The dimension of the linear beam in the short axis direction is, for example, several tens of micrometers to several hundreds of micrometers, and the dimension in the long axis direction is, for example, 50 mm to 100 mm.
The laser irradiation apparatus 11 does not melt the surface layer portion of the semiconductor substrate 3, activates the ions implanted into the surface layer portion, and applies the linear beam to the surface layer under conditions necessary to restore crystallinity. Irradiate the part.

The semiconductor substrate 3 is held by the substrate stage 5 and conveyed in the short axis direction of the linear beam. By moving the substrate stage 5, the pulse laser beam 1 shaped into a linear beam can be scanned relative to the semiconductor substrate 3 in the minor axis direction. In contrast to the above, scanning of the pulse laser beam 1 may be performed by fixing the position of the semiconductor substrate 3 and moving the irradiation position of the pulse laser beam 1.
Moreover, it is preferable that the substrate stage 5 is installed in a chamber that can be filled with a vacuum state or an inert gas from the viewpoint of dust prevention and prevention of oxide film generation on the substrate surface. Or the system which sprays an inert gas on the irradiation part of the pulsed laser beam 1 may be used.

  The auxiliary heating means 19 is not particularly limited as long as the surface layer portion of the semiconductor substrate 3 can be heated to a desired temperature. For example, a flash lamp (such as a xenon flash lamp) is suitable. Since the flash lamp radiates heat rays intermittently, the flash lamp can be appropriately heated within a range in which the temperature of the surface layer portion of the semiconductor substrate 3 does not rise excessively.

  The laser annealing apparatus 10 </ b> A includes a control device 18 for controlling the pulse laser oscillator 12, the substrate stage 5, and the auxiliary heating unit 19. The control device 18 controls the oscillation timing of the pulse laser beam 1, the timing of heating by the auxiliary heating means 19, and the movement of the substrate stage 5.

FIG. 2 shows the oscillation timing (upper diagram) of the pulse laser beam 1 and the heating timing (lower diagram) of the auxiliary heating means 19 in the first embodiment. In FIG. 2, the vertical axis is the output axis, and the horizontal axis is the time axis. The symbol a indicates the pulse width of the pulsed laser beam 1 and is, for example, several nanoseconds to several tens of nanoseconds. The symbol b indicates the pulse interval of the pulsed laser beam 1 and is, for example, several hundred nanoseconds or more. Symbol c indicates a continuous heating time per time when the auxiliary heating means 19 is a flash lamp. The flash lamp performs heating intermittently, and the heating time per heating corresponds to a plurality of times (for example, several tens of times) of the pulse interval b of the pulsed laser light 1, and one of them. The continuous heating time per time is, for example, several milliseconds or more.
However, as will be described later, the auxiliary heating means 19 may be any means as long as it heats the surface layer part at least until 1 microsecond elapses from the start of each irradiation of the pulse laser beam 1.

  In the laser annealing apparatus 10A configured as described above, this surface layer portion is oscillated under the condition that the pulse laser beam 1 is oscillated from the pulse laser oscillator 12 under the control of the control device 18 and the surface layer portion into which ions are implanted does not melt. Is irradiated with the pulse laser beam 1, and in parallel with the irradiation of the pulse laser beam 1, at least one microsecond has elapsed from the start of each irradiation of the pulse laser beam 1 by the auxiliary heating means 19. Heat the part. Here, the laser annealing method performed by the laser annealing apparatus 10A of the first embodiment is the first laser annealing method of the present invention.

In FIG. 3, the thermal analysis result about the influence which the auxiliary heating temperature by the auxiliary heating means 19 has on heating time in 1st Embodiment is shown.
From FIG. 3, in the case of auxiliary heating (B: 300 ° C. and C: 600 ° C.), the escape of heat in the thickness direction of the surface layer is suppressed compared to the case of no auxiliary heating (A: 20 ° C.). As a result, the rate of decrease in the temperature of the surface layer portion after irradiation with the pulsed laser beam 1 is slowed, and the heating time within a certain temperature range from the peak temperature can be extended. As a result, the annealing time at an effective annealing temperature can be extended. In FIG. 3, by setting the auxiliary heating temperature to 600 ° C., an annealing time of 1 microsecond or more at 800 ° C. or higher is achieved. In this way, by appropriately setting the heating temperature of the surface layer portion by the auxiliary heating means 19, an annealing time sufficient to recover the crystallinity of the surface layer portion can be obtained.

Here, when a flash lamp is used as the auxiliary heating means 19, the continuous heating time per one time is on the order of several milliseconds, and is a length corresponding to a plurality of pulse intervals of the pulsed laser beam 1. If the temperature is too high from the viewpoint of the diffusion rate of ions, the ions are diffused to a deep region by the auxiliary heating itself even when the pulse laser beam 1 is not irradiated.
Therefore, it is preferable that the temperature of the auxiliary heating is set to a temperature range in which the diffusion rate of ions in the surface layer portion does not exceed a predetermined value depending on the heating of the auxiliary heating. Thus, by appropriately setting the temperature of the auxiliary heating, it is possible to prevent ions from diffusing to a deep region.

  FIG. 4 shows the results of calculating the temperature and boron atom diffusion length for a time of 100 milliseconds. From FIG. 4, diffusion of about 10 nm occurs at about 800 ° C. Therefore, in the auxiliary heating at 800 ° C., the diffusion rate is too high to form an ultra-shallow junction of 20 nm or less required at a technology node of 65 nm or less. it is conceivable that. From this point of view, when a heating time corresponding to a plurality of pulse intervals of the pulse laser beam 1 is used as the auxiliary heating means 19 such as a flash lamp, the surface layer by the auxiliary heating means 19 is used. The heating temperature of the part is preferably set to 600 ° C. or lower. By controlling the temperature of auxiliary heating to 600 ° C. or lower, the diffusion rate of ions in the surface layer portion by auxiliary heating is suppressed to a level that does not substantially contribute to annealing for crystallinity recovery and ion activation. Therefore, an ultra-shallow junction having a shallow junction depth can be formed.

  As is apparent from the above description, according to the present embodiment, when forming an ultra-shallow junction, the crystallinity of the ion-implanted portion is recovered and the junction depth is reduced without using a large number of laser light sources. An annealing time necessary and sufficient for this can be obtained.

  In the laser annealing apparatus 10A of the present embodiment shown in FIG. 1, the laser beam is scanned with respect to the semiconductor substrate 3 by moving the substrate stage 5 in the minor axis direction of the linear beam. In consideration of the pulse interval (symbol b in FIG. 2), the substrate stage 5 is moved so that the irradiation position of the pulse laser beam 1 is shifted by the length in the short axis direction of the linear beam. The entire surface layer portion can be annealed. Alternatively, the shift amount of the irradiation position of the pulse laser beam 1 is set to be less than the length of the linear beam in the minor axis direction, and the substrate stage 5 is moved so that the number of irradiation times of the pulse laser beam 1 per unit region becomes plural times. You may let them.

[Second Embodiment]
FIG. 5 is a diagram showing an overall schematic configuration of a laser annealing apparatus 10B according to the second embodiment of the present invention.
The present embodiment is significantly different from the first embodiment in that the laser irradiation device 11 has a plurality of pulse laser oscillators 12A and 12B and pulse laser beams 1A and 1B from the pulse laser oscillators 12A and 12B on the same optical path. It is the point which has the synthetic | combination means 14 to synthesize | combine. Hereinafter, this embodiment will be specifically described. In the description of the present embodiment, items not mentioned are the same as in the first embodiment.

  The laser annealing apparatus 10B of the present embodiment is an apparatus that irradiates the surface layer portion into which ions as impurities of the semiconductor substrate 3 are implanted by irradiating the pulse laser beam 1, and includes two pulse laser oscillators 12A and 12B. A laser irradiation apparatus 11 that irradiates the surface layer portion with the combined pulse laser beam 1AB, and a semiconductor substrate 3 having a combining unit 14 that combines the pulse laser beams 1A and 1B from the pulse laser oscillators 12A and 12B on the same optical path; Auxiliary heating means 19 for heating the surface layer portion. Further, the laser annealing apparatus includes the beam shaping optical system 20, the substrate stage 5, and the control device 18 as in the first embodiment.

  The above two pulse laser oscillators (hereinafter referred to as “first laser oscillator 12A” and “second laser oscillator 12B”) can oscillate pulse laser beams 1A and 1B at the same pulse frequency. The oscillation timing of the control device 18 is such that the pulse laser beam 1B is oscillated from the second laser oscillator 12B at a predetermined time difference (symbol d in FIG. 6) from the oscillation of the pulse laser beam 1A by the first laser oscillator 12A. Be controlled.

The synthesizing unit 14 includes a half-wave plate 17, a mirror 15, and a polarization beam splitter 16.
The half-wave plate 17 rotates the polarization direction of the pulse laser beam 1B from the second laser oscillator 12B by 90 degrees and passes it. Specifically, the polarization plane of the pulse laser beam 1B is rotated from P-polarized light to S-polarized light.
The mirror 15 reflects the pulse laser beam 1 </ b> B in the direction of the polarization beam splitter 16.
The polarization beam splitter 16 passes the P-polarized pulsed laser light 1A from the first laser oscillator 12A and reflects the S-polarized pulsed laser light 1B from the second laser oscillator 12B, whereby two pulsed laser lights 1A and 1B are reflected. Are combined on the same optical path.

FIG. 6 shows the oscillation timing (upper diagram) of the pulsed laser beams 1A and 1B and the heating timing (lower diagram) by the auxiliary heating means 19 in the present embodiment. The meanings of the vertical axis, horizontal axis, and symbols a, b, and c in FIG. 6 are the same as those in FIG.
In the upper diagram of FIG. 6, several sets of two adjacent pulse outputs are shown, but the pulse output preceding in time in each set corresponds to the pulse laser beam 1A from the first laser oscillator 12A. The pulse output output with a delay time of the time difference d corresponds to the pulse laser beam 1B from the second laser oscillator 12B.
The predetermined time difference d is a time difference at which the temperature of the surface layer portion heated by the irradiation of the pulse laser beam 1A from the first laser oscillator 12A does not decrease to the temperature of the surface layer portion heated by the auxiliary heating means 19.

  In the laser annealing apparatus 10B configured as described above, pulse laser beams 1A and 1B are oscillated from the first laser oscillator 12A and the second laser oscillator 12B under the control of the control apparatus 18, and the laser oscillators 12A and 12B The pulsed laser beams 1A and 1B are synthesized on the same optical path, and the pulsed laser beam 1B is oscillated from the second laser oscillator 12B at a predetermined time difference d from the oscillation of the pulsed laser beam 1A by the first laser oscillator 12A. The surface layer portion is sequentially irradiated with the pulse laser beams 1A and 1B under the condition that the surface layer portion does not melt, and in parallel with the irradiation of the pulse laser beams 1A and 1B, at least the pulse laser beam 1A from the first laser oscillator 12A is irradiated. Until the 1 microsecond has elapsed from the start of each irradiation for each irradiation, the auxiliary heating means 19 heats the surface layer part, Serial of a predetermined time difference d, the temperature of the surface layer portion heated by irradiation of the pulsed laser beam 1A from the first laser oscillator 12A is a time difference does not decrease until the temperature of the heating of the surface layer portion by the auxiliary heating means 19. Here, the laser annealing method performed by the laser annealing apparatus 10B of the second embodiment is the second laser annealing method of the present invention.

In FIG. 7, the thermal analysis result about the influence which the auxiliary heating temperature by the auxiliary heating means 19 has on heating time in this embodiment is shown.
In FIG. 7, A, B, and C each have two peaks. The first peak indicates a temperature rise due to the irradiation of the pulse laser beam 1A from the first laser oscillator 12A, and the second peak is the first peak. 2 shows the temperature rise due to the irradiation of the pulse laser beam 1B from the two-laser oscillator 12B.

  According to the present embodiment, while assisting the heating of the surface layer portion by the auxiliary heating means 19, the pulse laser beams 1 from a plurality (two in this embodiment) of the pulse laser oscillators 12A and 12B are subjected to the predetermined time difference. Since irradiation is performed sequentially with d, the effective annealing time can be further extended. Other effects obtained by this embodiment are the same as those of the first embodiment described above.

  In the second embodiment described above, two pulse laser oscillators are used. However, three or more pulse laser oscillators may be used within a practical range. In this case, N is a natural number of 2 or more, pulse laser light 1 is oscillated from N number of pulse laser oscillators, pulse laser light from each pulse laser oscillator is synthesized on the same optical path, and n is less than N except 0 As a natural number, a pulse laser beam is oscillated from the (n + 1) th pulse laser oscillator at a predetermined time difference from the oscillation of the pulse laser beam 1 by the nth pulse laser oscillator, and the surface layer portion is pulsed under the condition that the surface layer portion does not melt. Sequentially irradiating with laser light, in parallel with the irradiation of pulsed laser light, at least until 1 microsecond has elapsed since the start of each irradiation of the pulsed laser light from the first pulsed laser oscillator, The surface layer portion is heated by auxiliary heating means, and the predetermined time difference is heated by irradiation of pulse laser light from the nth pulse laser oscillator. The temperature of the surface layer portion, a time difference does not decrease until the temperature of the heating of the surface layer portion by the auxiliary heating means.

Next, some configuration examples of the beam shaping optical system 20 in the first embodiment and the second embodiment described above will be described. However, the beam shaping optical system 20 is not limited to the following configuration example.
In the following description, the pulse laser beams 1 and 1AB are simply referred to as “laser beam 1”.

[First Configuration Example of Beam Shaping Optical System 20]
8A and 8B are diagrams showing the configuration of the beam shaping optical system 20 according to the first configuration example.
In FIG. 8A, an optical system acting in the major axis direction of the linear beam is shown, and an optical system acting only in the minor axis direction is indicated by an imaginary line (broken line).
In FIG. 8B, an optical system acting in the minor axis direction of the linear beam is shown, and an optical system acting only in the major axis direction is indicated by an imaginary line (broken line).

  The beam shaping optical system 20 includes a beam expander 21 that linearly expands the laser light 1 oscillated from the pulse laser oscillator 12 (or the first laser oscillator 12A and the second laser oscillator 12B) in the major axis direction and the minor axis direction. A long-axis homogenizer 22 that equalizes the energy distribution in the long-axis direction of the beam and a short-axis homogenizer 25 that equalizes the energy distribution in the short-axis direction of the linear beam are provided.

  The beam expander 21 shown as an example of the configuration is composed of a concave spherical lens 21a and a convex spherical lens 21b, and the incident laser light 1 is expanded in diameter by the concave spherical lens 21a and is converted into parallel light by the convex spherical lens 21b.

  As shown in FIG. 8A, the long-axis homogenizer 22 includes a long-axis cylindrical lens array 23 that divides an incident laser beam 1 into a plurality of pieces in the long-axis direction, and a laser beam 1 that is divided into a plurality of pieces in the long-axis direction. The long-axis condenser lens 24 is superposed in the long-axis direction.

  Further, as shown in FIG. 8A, a long-axis direction interference reducing optical system 31 is disposed between the beam expander 21 and the long-axis cylindrical lens array 23. The long-axis-direction interference reducing optical system 31 is configured by connecting a plurality of transparent glass plates 31a having the same width as each cylindrical lens constituting the long-axis cylindrical lens array 23 in the long-axis direction. In addition, an optical path difference of a distance longer than the coherent length is given to the laser light 1 passing through each transparent glass plate 31a to reduce the interference action in the major axis direction.

  As shown in FIG. 8B, the short-axis homogenizer 25 includes a short-axis cylindrical lens array 26 that divides incident laser light 1 into a plurality of short-axis directions, and a pulsed laser light 1 that is divided into a plurality of short-axis directions. Are arranged in the minor axis direction, and a projection lens 30 that projects the light emitted from the minor axis condenser lens 29 on the surface of the semiconductor substrate 3 is reduced.

  Further, as shown in FIG. 8B, a short-axis direction interference reducing optical system 32 is disposed between the beam expander 21 and the short-axis cylindrical lens array 26. The short-axis-direction interference reducing optical system 32 is configured by connecting a plurality of transparent glass plates 32a having the same width as each cylindrical lens constituting the short-axis cylindrical lens array 26 in the short-axis direction. In addition, an optical path difference of a distance longer than the coherent length is given to the laser light 1 passing through each transparent glass plate 32a to reduce the interference action in the short axis direction.

By the beam shaping optical system 20 configured as described above, the laser beam 1 oscillated from the pulse laser oscillator 12 (or the first laser oscillator 12A and the second laser oscillator 12B) is shaped into a linear beam, and the semiconductor substrate 3 Is irradiated.
In the laser beam 1, the energy distribution in the long axis direction of the linear beam is made uniform by the long axis homogenizer 22, and the energy distribution in the short axis direction of the linear beam is made uniform by the short axis homogenizer 25. The short axis cylindrical lens array 26 may be omitted, and only the energy distribution in the long axis direction may be made uniform.

[Second Configuration Example of Beam Shaping Optical System 20]
9A and 9B are diagrams showing a configuration of the beam shaping optical system 20 according to the second configuration example.
In FIG. 9A, an optical system acting in the major axis direction of the linear beam is shown, and an optical system acting only in the minor axis direction is indicated by an imaginary line (broken line).
In FIG. 9B, an optical system acting in the minor axis direction of the linear beam is shown, and an optical system acting only in the major axis direction is indicated by an imaginary line (broken line).

  The beam shaping optical system 20 of the second configuration example includes a beam extract that expands the laser beam 1 oscillated from the pulse laser oscillator 12 (or the first laser oscillator 12A and the second laser oscillator 12B) in the major axis direction and the minor axis direction. A panda 21, a long axis homogenizer 22 that equalizes the energy distribution in the long axis direction of the linear beam, and a short axis homogenizer 25 that equalizes the energy distribution in the short axis direction of the linear beam are provided. Here, the beam expander 21 shown as one configuration example is the same as the first configuration example described above.

As shown in FIG. 9A, the long-axis homogenizer 22 condenses the incident laser beam 1 into a plurality of waveguides 36 that divide the laser beam 1 in the long-axis direction and the laser beam 1 divided in the long-axis direction. It consists of two cylindrical lenses 39 and 40 that form an image by superimposing on the surface of the semiconductor substrate 3. Here, the two cylindrical lenses 39 and 40 constitute a long-axis-direction end-face transfer optical system. The waveguide 36 is also a constituent element of the short axis homogenizer 25.
An incident lens 34 that guides the laser beam 1 to the waveguide 36 is disposed between the beam expander 21 and the waveguide 36.
Further, a long-axis direction interference reducing optical system 42 is disposed between the two cylindrical lenses 39 and 40, and an optical path difference is given to the laser light 1 divided into a plurality of parts in the long-axis direction to cause an interference action. Reduced.

As shown in FIG. 9B, the short axis homogenizer 25 condenses the incident laser light 1 into a plurality of waveguides 36 that divide the laser light 1 in the short axis direction and the laser light 1 divided in the short axis direction in the short axis direction. And two cylindrical lenses 45 and 46 which are superposed on the surface of the semiconductor substrate 3 to form an image. Here, the two cylindrical lenses 45 and 46 constitute a short-axis direction end face transfer optical system.
Further, a short-axis direction interference reducing optical system 48 is disposed between the two cylindrical lenses 45 and 46, and an optical path difference is given to the laser light 1 divided into a plurality in the short-axis direction so as to cause an interference action. Reduced.

The laser beam 1 oscillated from the pulse laser oscillator 12 (or the first laser oscillator 12A and the second laser oscillator 12B) is shaped into a linear beam by the beam shaping optical system 20 of the second configuration example configured as described above. Then, the semiconductor substrate 3 is irradiated.
In the laser beam 1, the energy distribution in the long axis direction of the linear beam is made uniform by the long axis homogenizer 22, and the energy distribution in the short axis direction of the linear beam is made uniform by the short axis homogenizer 25.

  The long-axis homogenizer 22 and the short-axis homogenizer 25 are not limited to those described in the first configuration example and the second configuration example described above, and are other means for equalizing the energy distribution using a known optical system. There may be. For example, the long axis homogenizer 22 and / or the short axis homogenizer 25 may be an optical system including a diffractive optical element. Although a detailed description of the diffractive optical element is omitted, it is disclosed in, for example, Japanese Patent Application Laid-Open No. 2005-217209. In a diffractive optical element, a fine step is formed on a substrate such as quartz by a photoetching process or the like, and a diffraction pattern formed by laser light transmitted through each step portion has a desired energy distribution on the imaging surface (substrate surface). Prepare as obtained.

  Although the embodiments of the present invention have been described above, the embodiments of the present invention disclosed above are merely examples, and the scope of the present invention is not limited to these embodiments. The scope of the present invention is indicated by the description of the scope of claims, and further includes meanings equivalent to the description of the scope of claims and all modifications within the scope.

1 is a diagram illustrating an overall schematic configuration of a laser annealing apparatus according to a first embodiment of the present invention. It is a figure which shows the oscillation timing (upper figure) and the timing (lower figure) of the heating by an auxiliary heating means in 1st Embodiment. It is a figure which shows the thermal analysis result about the influence which the auxiliary heating temperature by the auxiliary heating means has on heating time in 1st Embodiment. It is a figure which shows the result of having calculated the temperature and the diffusion length of a boron atom with respect to time of 100 milliseconds. It is a figure which shows the whole schematic structure of the laser annealing apparatus concerning 2nd Embodiment of this invention. It is a figure which shows the oscillation timing (upper figure) and the timing (lower figure) of the heating by an auxiliary heating means in 2nd Embodiment. It is a figure which shows the thermal analysis result about the influence which the auxiliary heating temperature by the auxiliary heating means has on heating time in 2nd Embodiment. It is a figure which shows the structure of the beam shaping optical system concerning the 1st structural example. It is another figure which shows the structure of the beam shaping optical system concerning the 1st structural example. It is a figure which shows the structure of the beam shaping optical system concerning the 2nd structural example. It is another figure which shows the structure of the beam shaping optical system concerning a 2nd structural example.

Explanation of symbols

1, 1A, 1B, 1AB Pulse laser light 3 Semiconductor substrate 5 Substrate stage 10A, 10B Laser annealing device 11 Laser irradiation device 12 Pulse laser oscillator 12A First laser oscillator 12B Second laser oscillator 18 Controller 19 Auxiliary heating means 20 Beam shaping Optical System 21 Beam Expander 21a Concave Spherical Lens 21b Convex Spherical Lens 22 Long Axis Homogenizer 23 Long Axis Cylindrical Lens Array 24 Long Axis Condenser Lens 25 Short Axis Homogenizer 26 Short Axis Cylindrical Lens Array 29 Short Axis Condenser Lens 30 Projection lenses 31, 42 Long axis direction interference reduction optical system 32, 48 Short axis direction interference reduction optical system 34 Incident lens 36 Waveguides 39, 40, 45, 46 Cylindrical lens

Claims (8)

A laser annealing method for annealing by irradiating a surface layer portion into which ions as impurities of a semiconductor substrate are implanted with pulsed laser light,
Pulse laser light is oscillated from a pulse laser oscillator, and the surface layer portion is irradiated with the pulse laser light under the condition that the surface layer portion does not melt, and at least the pulse laser light is irradiated in parallel with the irradiation of the pulse laser light. A laser annealing method, wherein the surface layer portion is heated by auxiliary heating means until 1 microsecond has elapsed since the start of each irradiation. A laser annealing method for annealing by irradiating a surface layer portion into which ions as impurities of a semiconductor substrate are implanted with pulsed laser light,
N is a natural number of 2 or more, pulse laser light is oscillated from N pulse laser oscillators, pulse laser light from each pulse laser oscillator is synthesized on the same optical path, and n is a natural number less than N except 0, A pulse laser beam is oscillated from the (n + 1) th pulse laser oscillator with a predetermined time difference from the oscillation of the pulse laser beam by the nth pulse laser oscillator, and the pulse laser beam is applied to the surface layer portion under the condition that the surface layer portion does not melt. Are irradiated sequentially,
In parallel with the irradiation of the pulse laser beam, at least the surface layer is provided by the auxiliary heating means until one microsecond has elapsed from the start of each irradiation of the pulse laser beam from the first pulse laser oscillator. Heating the part,
The predetermined time difference is a time difference at which the temperature of the surface layer portion heated by the irradiation of the pulse laser beam from the nth pulse laser oscillator does not decrease to the temperature of the surface layer portion heated by the auxiliary heating means. A laser annealing method characterized by the above. The auxiliary heating means intermittently performs heating, and the heating time per heating corresponds to a plurality of pulse intervals of the pulse laser beam,
3. The laser annealing method according to claim 1, wherein the heating temperature of the surface layer portion by the auxiliary heating means is set to a temperature range in which the diffusion rate of ions in the surface layer portion does not exceed a predetermined value depending on the heating of the surface layer portion.   The laser annealing method according to claim 3, wherein a heating temperature of the surface layer portion by the auxiliary heating means is 600 ° C. or less. A laser annealing apparatus for annealing by irradiating a surface layer portion into which ions as impurities of a semiconductor substrate are implanted with pulsed laser light,
A laser irradiation apparatus having a pulse laser oscillator for oscillating a pulse laser beam, and irradiating the surface layer portion with the pulse laser beam;
An auxiliary heating means for heating the surface layer portion of the semiconductor substrate,
Pulse laser light is oscillated from the pulse laser oscillator, and the surface layer portion is irradiated with the pulse laser light under a condition that the surface layer portion does not melt, and in parallel with the irradiation of the pulse laser light, at least the pulse laser light A laser annealing apparatus, wherein the surface layer portion is heated by auxiliary heating means until 1 microsecond elapses from the start of each irradiation for each irradiation. A laser annealing apparatus for annealing by irradiating a surface layer portion into which ions as impurities of a semiconductor substrate are implanted with pulsed laser light,
N is a natural number equal to or greater than 2, and N pulse laser oscillators that oscillate pulse laser light and combining means for synthesizing the pulse laser light from each pulse laser oscillator on the same optical path, A laser irradiation device for irradiating the surface layer part;
An auxiliary heating means for heating the surface layer portion of the semiconductor substrate,
Assuming that n is a natural number less than N excluding 0, the (n + 1) th pulse laser oscillator oscillates with a predetermined time difference from the oscillation of the pulse laser beam by the nth pulse laser oscillator, and the surface layer portion melts. Without irradiating the pulsed laser beam sequentially on the surface layer part under the conditions that do not
In parallel with the irradiation of the pulsed laser beam, at least until 1 microsecond has elapsed from the start of each irradiation of the pulsed laser beam from the first pulsed laser oscillator, the auxiliary heating means Heating the surface layer,
The predetermined time difference is a time difference at which the temperature of the surface layer portion heated by the irradiation of the pulse laser beam from the nth pulse laser oscillator does not decrease to the temperature of the surface layer portion heated by the auxiliary heating means. A laser annealing apparatus characterized by the above. The auxiliary heating means intermittently performs heating, and the heating time per heating corresponds to a plurality of pulse intervals of the pulse laser beam,
The laser annealing apparatus according to claim 5 or 6, wherein the heating temperature of the surface layer portion by the auxiliary heating means is set to a temperature range in which the diffusion rate of ions in the surface layer portion does not exceed a predetermined value depending on the heating of the surface layer portion.   The laser annealing apparatus according to claim 7, wherein a heating temperature of the surface layer portion by the auxiliary heating unit is set to 600 ° C. or less.

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