WO2008024211A2 - Mise en forme de profil de faisceau à axe fixe pour système de recuit à diodes laser haute puissance - Google Patents

Mise en forme de profil de faisceau à axe fixe pour système de recuit à diodes laser haute puissance Download PDF

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Publication number
WO2008024211A2
WO2008024211A2 PCT/US2007/017684 US2007017684W WO2008024211A2 WO 2008024211 A2 WO2008024211 A2 WO 2008024211A2 US 2007017684 W US2007017684 W US 2007017684W WO 2008024211 A2 WO2008024211 A2 WO 2008024211A2
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WIPO (PCT)
Prior art keywords
fast axis
emitters
rows
optical
deflection
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PCT/US2007/017684
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English (en)
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WO2008024211A3 (fr
Inventor
Dean Jennings
Abhilash Mayur
Timothy N. Thomas
Vijay Parihar
Vedapuram S. Achutharaman
Randhir P.S. Thakur
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Applied Materials, Inc.
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Publication of WO2008024211A2 publication Critical patent/WO2008024211A2/fr
Publication of WO2008024211A3 publication Critical patent/WO2008024211A3/fr

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Classifications

    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
    • H01S5/00—Semiconductor lasers
    • H01S5/40—Arrangement of two or more semiconductor lasers, not provided for in groups H01S5/02 - H01S5/30
    • H01S5/4025—Array arrangements, e.g. constituted by discrete laser diodes or laser bar
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
    • B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
    • B23K26/00—Working by laser beam, e.g. welding, cutting or boring
    • B23K26/02—Positioning or observing the workpiece, e.g. with respect to the point of impact; Aligning, aiming or focusing the laser beam
    • B23K26/06—Shaping the laser beam, e.g. by masks or multi-focusing
    • B23K26/0604—Shaping the laser beam, e.g. by masks or multi-focusing by a combination of beams
    • B23K26/0608—Shaping the laser beam, e.g. by masks or multi-focusing by a combination of beams in the same heat affected zone [HAZ]
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
    • B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
    • B23K26/00—Working by laser beam, e.g. welding, cutting or boring
    • B23K26/08—Devices involving relative movement between laser beam and workpiece
    • B23K26/082—Scanning systems, i.e. devices involving movement of the laser beam relative to the laser head
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L21/00—Processes or apparatus adapted for the manufacture or treatment of semiconductor or solid state devices or of parts thereof
    • H01L21/02—Manufacture or treatment of semiconductor devices or of parts thereof
    • H01L21/02104—Forming layers
    • H01L21/02365—Forming inorganic semiconducting materials on a substrate
    • H01L21/02656—Special treatments
    • H01L21/02664—Aftertreatments
    • H01L21/02667—Crystallisation or recrystallisation of non-monocrystalline semiconductor materials, e.g. regrowth
    • H01L21/02675—Crystallisation or recrystallisation of non-monocrystalline semiconductor materials, e.g. regrowth using laser beams
    • H01L21/02678—Beam shaping, e.g. using a mask
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L21/00—Processes or apparatus adapted for the manufacture or treatment of semiconductor or solid state devices or of parts thereof
    • H01L21/02—Manufacture or treatment of semiconductor devices or of parts thereof
    • H01L21/02104—Forming layers
    • H01L21/02365—Forming inorganic semiconducting materials on a substrate
    • H01L21/02656—Special treatments
    • H01L21/02664—Aftertreatments
    • H01L21/02667—Crystallisation or recrystallisation of non-monocrystalline semiconductor materials, e.g. regrowth
    • H01L21/02691—Scanning of a beam
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
    • H01S5/00—Semiconductor lasers
    • H01S5/005—Optical components external to the laser cavity, specially adapted therefor, e.g. for homogenisation or merging of the beams or for manipulating laser pulses, e.g. pulse shaping
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
    • H01S5/00—Semiconductor lasers
    • H01S5/40—Arrangement of two or more semiconductor lasers, not provided for in groups H01S5/02 - H01S5/30
    • H01S5/4012—Beam combining, e.g. by the use of fibres, gratings, polarisers, prisms

Definitions

  • the invention relates generally to thermal processing of semiconductor substrates.
  • the invention relates to laser thermal processing of semiconductor substrates.
  • Thermal processing is required in the fabrication of silicon and other semiconductor integrated circuits formed in silicon wafers or other substrates such as glass panels for displays.
  • the required temperatures may range from relatively low temperatures of less than 250 degrees C to greater than 1400 degrees C and may be used for a variety of processes such as dopant implant annealing, crystallization, oxidation, nitridation, silicidation, and chemical vapor deposition as well as others.
  • dopant implant annealing crystallization, oxidation, nitridation, silicidation, and chemical vapor deposition as well as others.
  • the thermal budget may be considered as the total time at high temperatures necessary to complete device fabrication. The time that the wafer needs to stay at the highest temperature can be very short.
  • Rapid thermal processing uses radiant lamps which can be very quickly turned on and off to heat only the wafer and not the rest of the chamber. Pulsed laser annealing using very short (about 20 ns) laser pulses is effective at heating only the surface layer and not the underlying wafer, thus allowing very short ramp up and ramp down rates.
  • DSA dynamic surface annealing
  • the thinness of the line beam ensures very short temperature rise and fall times and a short dwell time at the required temperature, e.g., 1300 degrees C, with respect to a fixed location on the wafer surface that is scanned once by the line beam.
  • the temperature of a fixed location on the wafer surface will increase from an ambient 450 degrees C to 1300 degrees C within 0.6 ms, assuming a scan rate within a range of about 50-300 mm/sec is employed.
  • the wafer surface spends an extremely short amount of time at lower or intermediate temperatures (e.g., 500- 900 degrees C) at which the higher silicon thermal conductivity promotes heating throughout the wafer and consequent diffusion and loss of underlying circuit feature definition. Instead, the wafer surface spends more time at the desired high temperature (e.g., 1300 degrees c) at which silicon thermal conductivity is lowest for minimum heating of the underlying features, and at which desired effects are maximum (e.g., annealing of implanted dopant impurities, annealing of pre-implant amorphization damage, etc.).
  • the thinness of the line beam corresponds to the minimum resolvable spot size R of the laser beam optical system, which is governed by the following approximate formula:
  • R ⁇ /2 NA, where ⁇ is the laser wavelength and NA is the numerical aperture of the optics.
  • Numerical aperture is defined as:
  • NA n sin ⁇ /2, where n is the index of refraction and ⁇ is the angle subtended by the beam between the aperture at the lens and the focal point in a simple or ideal system.
  • the wavelength is 810 nm and the angle ⁇ is less than 60 degrees and n is the index of refraction of air (about 1).
  • each fixed wafer surface location spends less than about 0.5 ms near the peak temperature (e.g., 1300 degrees C).
  • the required level of the wafer surface peak temperature (1300 degrees C) requires a power density of about 220 kiloWatts/cm 2 .
  • the DSA system employs a large number of 810 nm CW diode lasers focused on the same line beam image, as will be described later in this specification.
  • One problem recently encountered is that some annealing processes requires a longer time at or near the peak temperature (1300 degrees C), than the current dwell time of less than 0.5 ms . This dwell time may be sufficient to cause ion implanted dopant impurities to become substitutional in the semiconductor crystal lattice. However, it may be insufficient to completely cure pre-ion implantation amorphization defects. Pre-ion implantation amorphization is performed prior to ion implantation of dopant impurities to form shallow PN junctions to prevent channeling of the kinetic dopant ions through the crystal lattice below the desired junction depth.
  • Amorphization prevents such channeling by ion bombardment of the wafer with heavier atomic species (oxygen, nitrogen, carbon) , causing bombardment damage to at least partially convert the active semiconductor layer from a crystalline state to an amorphous state.
  • the defects in the crystal are cured provided each wafer surface location has a sufficiently long dwell time near 1300 degrees C. This may require a dwell time that is longer than the current 0.5 ms dwell time.
  • conversion of the amorphized region back to a crystalline state essentially forms an epitaxial crystalline layer over the bulk crystalline layer, giving rise to another class of defects, namely boundary defects at the interface between the bulk crystal and the re-crystallized surface.
  • Such boundary defects have been found to be more persistent than the other types of defects, and require a significantly longer dwell time to completely cure or remove, as long as 2 to 3 ms near 1300 degrees C.
  • the beam spot size In order to provide such a long dwell time, the beam spot size must be enlarged, which essentially broadens the Gaussian profile of the beam intensity along the direction of scan, hereinafter referred to as the "fast axis".
  • the Gaussian beam profile is widened by a given factor, then the slope of the leading edge of the Gaussian beam profile is reduced by approximately the same factor.
  • a dynamic surface anneal apparatus for annealing a semiconductor workpiece has a workpiece support for supporting a workpiece, an optical source and scanning apparatus for scanning the optical source and the workpiece support relative to one another along a fast axis.
  • the optical source includes an array of laser emitters arranged generally in successive rows of the emitters, the rows being transverse to the fast axis. Plural collimating lenslets overlie respective ones of the rows of emitters and have a collimation direction along the fast axis .
  • the optical source further includes a fast axis optical deflection element associated with selected ones of the rows of emitters and having one or a succession of optical deflection angles corresponding to beam deflections along the fast axis for respective rows of emitters. Optics focus light from the array of laser emitters onto a surface of the workpiece to form a succession of line beams transverse to the fast axis spaced along the fast axis in accordance with the succession of deflection angles.
  • FIG. 1 is an orthographic representation of a thermal flux laser annealing apparatus employed in the present invention.
  • FIGS. 2 and 3 are orthographic views from different perspectives of optical components of the apparatus of FIG. 1.
  • FIG. 4 is an end plan view of a portion of a semiconductor laser array in the apparatus of FIG. 1.
  • FIG. 5 is an orthographic view of a homogenizing light pipe for the apparatus of FIG. 1.
  • FIG. 6 is a schematic diagram corresponding to FIGS. 2 and 3.
  • FIG. 7 is a perspective view of a portion of the beam source of an embodiment of the invention.
  • FIG. 8 is an end view corresponding to FIG. 7 and further illustrating a controller for varying the fast axis power density profile of the two line beams.
  • FIG. 9 is a graph depicting the fast-axis power density profile obtained with the apparatus of FIGS. 7 and 8.
  • FIG. 10 is a schematic diagram of another embodiment of the invention employing several displace Gaussian beams with a programmable fast-axis profile.
  • FIGS. HA through HE are graphs of different fast-axis power density profiles that can be selected with a programmable controller of the DSA apparatus of FIG. 10.
  • FIG. 12A is a graph depicting a preferred power density profile over time generated with the DSA apparatus of FIG. 10.
  • FIG. 12B is a graph contemporaneous with the graph of FIG..12A and depicting the time behavior of the temperature of a fixed spot on the wafer surface resulting from the power density profile of FIG. 12A.
  • FIG. 13 is a cut-away side view of a semiconductor device formed using the DSA apparatus of the invention .
  • FIG. 14 depicts a DSA process employing the apparatus of FIG. 10.
  • FIG. 15 is a schematic diagram depicting a first modification of the embodiment of FIG. 8 employing beam deflecting mirrors.
  • FIG. 16 is a schematic diagram depicting a second modification of the embodiment of FIG. 8 employing a single beam deflecting mirror.
  • FIGS. 17 and 18 depict a third modification of the embodiment of FIG. 8 in which selected ones of the fast-axis collimating cylindrical lenses are rotated through the desired beam-deflecting angle.
  • FIG. 19 is a schematic diagram depicting a first modification of the embodiment of FIG. 10 in which the prisms of successively greater beam deflection angles are replaced by rotating the corresponding fast-axis cylindrical lenses through successively greater angles.
  • FIG. 20 is a schematic diagram depicting a second modification of the embodiment of FIG. 10 in which the prisms of successively greater beam deflection angles are replaced by respective beam deflecting mirrors rotated through successively greater angles.
  • This displacement is preferably the width of the Gaussian profile of the line beam along the fast axis at an amplitude corresponding to half the peak amplitude of one of the two line beams.
  • Both line beams have the same highly focused image with the minimum resolvable spot size of about 0.07 mm as before.
  • the angle subtended between the optical paths of the two sets of lasers is less than one degree in order to achieve such a small displacement, and this angle depends upon the distance between the lasers and the wafer surface.
  • the net effect is the same extremely steep slope of the leading and trailing beam edges along the fast axis as with a single line beam, but with a dwell time at or near the peak temperature that is doubled from that of a single line beam.
  • One of the laser line beams is the leading beam while the other is the trailing beam.
  • the leading beam must raise the wafer surface temperature from about 400 degrees C to 1300 degrees C within 0.5 ms, and must therefore be of higher power density, while the trailing beam must simply maintain the wafer surface at the elevated temperature (without increasing the temperature) , and is therefore of a lesser power density.
  • the time-profile of the wafer surface temperature at each fixed location may be adjusted by adjusting the currents supplied to the two sets of lasers. Finer adjustment may be realized by providing a larger number of laser sets focused respectively on the corresponding number of line beams (e.g., four line beams) , and programming the four current levels supplied to the four laser sets.
  • a gantry structure 10 for two-dimensional scanning includes a pair of fixed parallel rails 12, 14.
  • Two parallel gantry beams 16, 18 are fixed together a set distance apart and supported on the fixed rails 12, 14 and are controlled by an unillustrated motor and drive mechanism to slide on rollers or ball bearings together along the fixed rails 12, 14.
  • a beam source 20 is slidably supported on the gantry beams 16, 18, and may be suspended below the beams 16, 18 which are controlled by unillustrated motors and drive mechanisms to slide along them.
  • a silicon wafer 22 or other substrate is stationarily supported below the gantry structure 10.
  • the beam source 20 includes a laser light source and optics (described below) to produce two closely spaced downwardly directed fan-shaped beams 24 and 25 that strike the wafer 22 as leading and trailing line beams 26 and 27, respectively, extending generally parallel to the fixed rails 12, 14, in what is conveniently called the slow direction.
  • the second line beam 27 is parallel to the first line beam 26 and displaced from it by a distance corresponding to the minimum resolvable spot size of the optical system. How that is accomplished is discussed later in this specification.
  • the gantry structure further includes a Z-axis stage for moving the laser light source and optics in a direction generally parallel to the fan-shaped beam 24 to thereby controllably vary the distance between the beam source 20 and the wafer 22 and thus control the focusing of the line beam 26 on the wafer 22.
  • Exemplary dimensions of the line beam 26 include a length of 1 cm and a width of 66 microns with an exemplary power density of 220kW/cm 2 .
  • the beam source and associated optics may be stationary while the wafer is supported on a stage which scans it in two dimensions .
  • the gantry beams 16, 18 are set at a particular position along the fixed rails 12, 14 and the beam source 20 is moved at a uniform speed along the gantry beams 16, 18 to scan the line beams 26, 27 perpendicularly to its long dimension in a direction conveniently called the fast direction.
  • the two line beams 26, 27 are thereby scanned from one side of the wafer 22 to the other to irradiate a 1 cm swath of the wafer 22.
  • the line beams 26, 27 are sufficiently narrow and the scanning speed in the fast direction is sufficiently fast so that a particular area of the wafer is only momentarily exposed to the optical radiation of the line beams 26, 27 but the intensity at the peak of the line beam is sufficient to heat the surface region to very high temperatures.
  • the optics beam source 20 includes an array of lasers in order to realize the high optical power density (220kW/cm 2 ) required.
  • Each laser bar stack 32 includes 14 parallel bars 34, generally corresponding to a vertical p-n junction in a GaAs semiconductor structure, extending laterally about lcm and separated by about 0.9mm. Typically, water cooling layers are disposed between the bars 34.
  • each bar 34 are formed 49 emitters 36, each constituting a separate GaAs laser emitting respective beams having different divergence angles in orthogonal directions.
  • the illustrated bars 34 are positioned with their long dimension extending over multiple emitters 36 and aligned along the slow axis and their short dimension corresponding to the less than 1-micron p-n depletion layer aligned along the fast axis.
  • the small source size along the fast axis allows effective collimation along the fast axis.
  • the divergence angle is large along the fast axis and relatively small along the slow axis.
  • individual half- cylindrical lenslets 40 are positioned over individual laser bars 34 to collimate the laser light in a narrow beam along the fast axis.
  • the lensets 40 may be bonded with adhesive on the laser stacks 32 and aligned with the bars 34 to extend over the emitting areas 36. As will be described in more detail later in this specification, some of the laser bars 34 and their lenlets 40 are covered by prisms 44 that deflect the light by an angle less than 1 degree to form the second (trailing) line beam 27 depicted in FIG. 1.
  • the angle of the prisms 44 and the displacement between the two line beams 26, 27 are so infinitesimally small relative to the scale of the drawings of FIGS. 1-4 that their size in the drawings has been greatly exaggerated in order for them to be slightly visible in the drawings.
  • the optics beam source 20 can further include conventional optical elements.
  • Such conventional optical elements can include an interleaver and a polarization multiplexer, although the selection by the skilled worker of such elements is not limited to such an example.
  • the two sets of beams from the two bar stacks 32 are input to an interleaver 42, which has a multiple beam splitter type of structure and having specified coatings on two internal diagonal faces, e.g., reflective parallel bands, to selectively reflect and transmit light.
  • interleavers are commercially available from Research Electro Optics (REO) .
  • patterned metallic reflector bands are formed in angled surfaces for each set of beams from the two bar stacks 32 such that beams from bars 34 on one side of the stack 32 are alternatively reflected or transmitted and thereby interleaved with beams from bars 34 on the other side of the stack 32 which undergo corresponding selective transmission/reflection, thereby filling in the otherwise spaced radiation profile from the separated emitters 36.
  • a first set of interleaved beams is passed through a half-wave plate 48 to rotate its polarization relative to that of the second set of interleaved beams.
  • Both sets of interleaved beams are input to a polarization multiplexer (PMUX) 52 having a structure of a double polarization beam splitter.
  • PMUX polarization multiplexer
  • First and second diagonal interface layers 54, 56 cause the two sets of interleaved beams to be reflected along a common axis from their front faces.
  • the first interface 54 is typically implemented as a dielectric interference filter designed as a hard reflector (HR) while the second interface 56 is implemented as a dielectric interference filter designed as a polarization beam splitter (PBS) at the laser wavelength.
  • HR hard reflector
  • PBS polarization beam splitter
  • the interleaver 42, the half-wave plate 48, and the PMUX 52 and its interfaces 54, 56, as well as additional filters that may be attached to input and output faces are typically joined together by a plastic encapsulant, such as a UV curable epoxy, to provide a rigid optical system.
  • a plastic encapsulant such as a UV curable epoxy
  • the source beam 58 is passed through a set of cylindrical lenses 62, 64, 66 to focus the source beam 58 along the slow axis.
  • a one-dimensional light pipe 70 homogenizes the source beam along the slow axis.
  • the source beam focused by the cylindrical lenses 62, 64, 66, enters the light pipe 70 with a finite convergence angle along the slow axis but substantially collimated along the fast axis.
  • the light pipe 70 acts as a beam homogenizer to reduce the beam structure along the slow axis introduced by the multiple emitters 36 in the bar stack 32 spaced apart on the slow axis.
  • the light pipe 70 may be implemented as a rectangular slab 72 of optical glass having a sufficiently high index of refraction to produce total internal reflection. It has a short dimension along the slow axis and a longer dimension along the fast axis.
  • the slab 72 extends a substantial distance along an axis 74 of the source beam 58 converging along the slow axis on an input face 76.
  • the source beam 58 is internally reflected several times from the top and bottom surfaces of the slab 72, thereby removing much of the texturing along the slow axis and homogenizing the beam along the slow axis when it exits on an output face 78.
  • the source beam 58 is already well collimated along the fast axis (by the cylindrical lenslets 40) and the slab 72 is wide enough that the source beam 58 is not internally reflected on the side surfaces of the slab 72 but maintains its collimation along the fast axis.
  • the light pipe 70 may be tapered along its axial direction to control the entrance and exit apertures and beam convergence and divergence.
  • the one-dimensional light pipe can alternatively be implemented as two parallel reflective surfaces corresponding generally to the upper and lower faces of the slab 72 with the source beam passing between them.
  • the source beam output by the light pipe 70 is generally uniform.
  • anamorphic lens set or optics 80, 82 expands the output beam in the slow axis and includes a generally spherical lens to project the desired line beam 26 on the wafer 22.
  • the anamorphic optics 80, 82 shape the source beam in two dimensions to produce a narrow line beam of limited length.
  • the output optics In the direction of the fast axis, the output optics have an infinite conjugate for the source at the output of the light pipe (although systems may be designed with a finite source conjugate) and a finite conjugate at the image plane of the wafer 22 while, in the direction of the slow axis, the output optics has a finite conjugate at the source at the output of the light pipe 70 and a finite conjugate at the image plane. Further, in the direction of the slow axis, the nonuniform radiation from the multiple laser diodes of the laser bars is homogenized by the light pipe 70. The ability of the light pipe 70 to homogenize strongly depends on the number of times the light is reflected traversing the light pipe 70.
  • This number is determined by the length of the light pipe 70, the direction of the taper if any, the size of the entrance and exit apertures as well as the launch angle into the light pipe 70. Further anamorphic optics focus the source beam into the line beam of desired dimensions on the surface of the wafer 22.
  • one group of laser bars 34 radiate through corresponding cylindrical lenslets 40 to the optics 42, 52, etc.
  • the remaining ones of the lasers bars 34 radiate through corresponding cylindrical lenslets 40 and through individual prisms 44 overlying respective ones of the lenslets 40.
  • Each prism 44 deflects the beam by an angle (A) less than 1 degree through an angle of rotation about an axis parallel with the fast axis to produce a beam deflection perpendicular to the fast axis.
  • the first group of laser bars 34 whose beams are undeflected generate the leading beam 24.
  • the second group of laser bars 34 whose beams are deflected by the respective prisms 44 generate the trailing beam 25.
  • FIG. 7 shows two of the laser bars 34 forming two parallel rows of emitters 36, both covered by respective cylindrical lenslets 40, and one of the lenslets 40 being covered by a prism 44.
  • FIG. 8 illustrates how the power densities of the leading and trailing beams 24, 25 are independently governed by a profile controller 100 controlling current supplies 102, 104 that drive the emitters 36 of alternate laser bars 34.
  • the first current supply 102 is the front beam current supply because it is coupled to each of the laser bars not covered by any of the prisms 40.
  • the second current supply 104 is the trailing beam current supply because it is coupled to each of the laser bars covered by a prism 44. Each prism 44 deflects the corresponding laser beam to form the trailing beam 25.
  • the two line beams 26, 27 (FIG. 1) imaged on the wafer 22 by the leading and trailing beams 24, 25 are separated by a displacement determined by the deflection angle of the prisms 44.
  • the terms "front” and “trailing” apply to an embodiment in which the beam is scanned across the wafer in a particular direction. If this direction is reversed, then the beams deflected by the prisms 44 form the leading or "front” beam 26 while the undeflected beams form the trailing beam 27.
  • the invention may be carried out in either mode, and therefore the terms such as "front” and “trailing", for example, are employed interchangeably with respect to the embodiment of FIG. 6.
  • the power density of the trailing line beam 27 may be significantly less than that of the front line beam 26. This is because the front line beam 26 must have sufficient power density to raise the temperature of the wafer surface rapidly through the lower temperature ranges where the higher thermal conductivity of the wafer makes it more difficult to heat the surface, until the wafer surface reaches the peak temperature.
  • the trailing line beam merely maintains this temperature, which requires less power density, to avoid raising the wafer surface temperature beyond the maximum desired temperature (1300 degrees C) . Therefore, as indicated in FIG. 9, the trailing line beam has a fast axis profile whose peak power density is significantly lower than that of the leading line beam. The difference between the peak power density levels of the two beams is set by the profile controller 100 of FIG. 8.
  • FIG. 10 depicts an embodiment providing several (i.e., four) trailing beams in succession, each one with an independently adjustable power density.
  • the laser bars 34 are divided into four groups.
  • the one group of laser bars 34-0 produce laser radiation that is undeflected, to form the front beam.
  • Another group of laser bars 34-1 produce radiation that is deflected by prisms 44-1 through a small angle Al to produce the first trailing beam.
  • a further group of laser bars 34-2 produce radiation that is deflected by prisms 44-2 through an angle A2 that is greater than Al.
  • Another group of laser bars 34-3 produce radiation that is deflected by prisms 44-3 through an angle A3 that is greater than A2.
  • the four line beams 26-1, 26-2, 26-3, 26-4 are focused by the optics (42, 52, etc. of FIGS. 2-6) on the wafer surface.
  • their power density profiles along the fast axis are of identical Gaussian shapes, but are shifted from one another along the fast axis by the same peak-to-peak displacement, as depicted in FIG. 11A. This displacement is determined by the succession of deflection angles Al, A2 , A3 imposed by the prisms 44-1, 44-2, 44-3.
  • the angles Al, A2, A3 are selected so that the peak-to-peak displacement between neighboring line beams is at least approximately (if not exactly) equal to the half-maximum beam width (depicted in FIG. 9) of a single line beam (e.g., of the front beam). EquivalentIy, the displacement may correspond to the minimum resolvable spot size of the beam, discussed previously in this specification.
  • the deflection angles are all less than 1 degree and in reality would not be detectable in the drawing of FIG. 10. These angles have been exaggerated in FIG. 10 for the sake of illustration.
  • the power density levels produced by the different groups of laser bars 34-0, 34-1, 34-2, 34-3 are independently adjustable by a laser power controller 110 that furnishes independent supply currents 10, II, 12, 13 to the respective laser bars 34-0, 34-1, 34-2, 34-3.
  • the laser power controller 110 therefore controls the fast axis power density profile produced by the array of lasers. While their power densities may be the same (corresponding to the power density profile of FIG. HA) , it is preferable for the power densities of the trailing line beams to be less than that of the front or leading line beam, in accordance with the various power density profiles of FIGS. HB, HC or HD.
  • the successive line beam supply current levels 10, H, 12, 13 may be adjusted by the controller 110 to produce a staircase profile of successively decreasing power density levels as in FIG. HB, or the single staircase of FIG. HC, or the gradual staircase of FIG. HD.
  • the amplitude profile may fall after the front or leading line beam and then increase from the third to last line beam, as depicted in FIG. HE.
  • the profile may be further adjusted to produce an ascending staircase pattern instead of the descending staircase profiles of FIGS. 11B-11D.
  • FIG. 12A depicts the power density incident upon a particular spot on the wafer surface as a function of time. (If FIG. 12A were converted to depict power density distribution along the fast axis at a fixed instant in time, then the graph would remain unchanged, depending upon the units chosen.)
  • the leading line beam 26-1 has the highest peak power density, while the successive trailing line beams 26-2, 26-3, 26-4 have a lesser peak power density, which is the same for each of them.
  • the strong leading beam 26-1 of FIG. 12A has sufficient power density to overcome the high silicon thermal conductivity to rapidly heat the wafer surface spot to 1300 degrees C.
  • FIG. 12B depicts the temperature behavior over time of the same wafer surface spot that results from the beam profile of FIG. 12A.
  • the temperature rises rapidly from 400 degrees C to 1300 degrees C with the leading edge of the front beam.
  • the temperature of the spot then remains at about 1300 degrees C for 3 ms, with slight undulations in the temperature corresponding with the peaks of the successive beams. After about 3 ms, the temperature falls rapidly to 400 degrees C with the trailing edge of the last line beam.
  • FIG. 12B indicates the succession of effects of the laser radiation in a post-ion implantation DSA annealing process using the beam profile of FIG. 12A.
  • Tl an initial time interval
  • ion bombardment damage in the semiconductor material incurred during a pre-implant amorphization process is annealed to convert the semiconductor material from a partially amorphous state to a crystalline state.
  • T2 the implanted dopant impurities are rendered substitutional in the semiconductor crystal lattice.
  • T3 boundary defects formed at the interface between the bulk crystal and the re-crystallized zone are cured.
  • FIG. 13 illustrates the location of such boundary defects.
  • the boundary defects arise when the amorphized semiconductor surface layer is re-crystallized to form an epitaxial crystal layer over the bulk crystal.
  • the two crystal zones may not align perfectly at the boundary between them, giving rise to misalignments that are defects.
  • Such defects may require as long as 3 ms at 1300 degrees C (i.e., the entire duration of the multiple line beams of FIG. 12A) to completely anneal or cure.
  • FIG. 14 depicts an ion implantation process for forming ultra-shallow PN junctions such as source-drain extension implants in the surface of a silicon wafer.
  • the structure to be formed is depicted in FIG. 13, in which ion implanted source-drain extensions 200, 205 are implanted between deep source-drain contact regions 210, 215 and a semiconductor channel region 220 underlying a gate electrode 225 insulated from the channel region 220 by a thin gate dielectric layer 230.
  • FIG. 13 depicts an ion implantation process for forming ultra-shallow PN junctions such as source-drain extension implants in the surface of a silicon wafer.
  • the structure to be formed is depicted in FIG. 13, in which ion implanted source-drain extensions 200, 205 are implanted between deep source-drain contact regions 210, 215 and a semiconductor channel region 220 underlying a gate electrode 225 insulated from the channel region 220 by a thin gate dielectric layer 230.
  • the surface region extending from the top surface 235 of the wafer to the horizontal dashed line 240 is converted from a pure crystalline state to an at least partially amorphous state by ion bombarding the wafer with heavy ions (e.g., oxygen, nitrogen, carbon, germanium) to break the crystal bonds.
  • This ion bombardment is carried out at an energy level at which the distribution of ions in the wafer extends down to the dashed line 240 and is virtually cut-off below that line.
  • the purpose of this amorphization step is to prevent channeling of dopant impurity ions that are to be implanted in the next step of the process.
  • the next step is to implant a dopant impurity to form, for example, the source drain extensions 210, 215.
  • the dopant impurity may be As, P, B or other species. This step may be preceded by masking steps to shield areas of the wafer that are not to be implanted in this step.
  • the ion energy is selected so that the implanted ion distribution does not extend below the desired depth, such as the ultra-shallow depth of the source drain extensions 210, 215 for example.
  • an optical absorber layer may be deposited on the wafer surface (block 260 of FIG. 14) .
  • This step may be carried out in accordance with the low-temperature plasma process and apparatus described in U.S. Patent Application Serial No. 11/131,904, filed May 17, 2005, entitled A SEMICONDUCTOR JUNCTION FORMATION PROCESS INCLUDING LOW TEMPERATURE PLASMA DEPOSITION OF AN OPTICAL ABSORPTION LAYER AND HIGH SPEED OPTICAL ANNEALING by Kartik Ramaswamy, et al. and assigned to the present assignee.
  • the optical absorber layer may be amorphous carbon, for example.
  • the next step is to perform the scanning laser DSA process using multiple line beams with a configurable beam profile.
  • a first sub-step (block 271) of this step is to rapidly raise the temperature of a newly encountered wafer surface spot (or line of spots) from an ambient temperature of 400-450 degrees C up to 1300 degrees C using the steep leading edge of the front beam 26-1 (FIG. 12A) .
  • the next sub-step (block 272) is to maintain the wafer temperature at about 1300 degrees C for a sufficient time (e.g., 3 ms) to (a) re-crystallize the amorphized surface region, (b) render the implanted dopant impurities subsitutional in the re-crystallized lattice and (c) cure the defects at the boundary between the re- crystallized zone and the underlying bulk crystal.
  • the final sub-step (block 273) is to rapidly reduce the spot surface temperature in accordance using the steep trailing edge of the last trailing beam 26-4 (FIG. 12A) .
  • FIG. 15 depicts a modification of the embodiment of FIG.
  • each mirror 121, 122, 123 deflects the beams from alternate laser bars 34 in the same manner that the prisms 44 deflected the beams in the embodiment of FIG. 8. If the beam deflection angle is A, then the angle of each mirror 121, 122, 123 relative to the beam direction emerging from each laser bar 34 is A/2.
  • FIG. 16 depicts a simpler version of the embodiment of FIG. 15, in which a single optical element 120, which may be a mirror or a prism, deflects the beams from a succession of lasers bars 34-1, 34-2, 34-3, etc., to produce the trailing line beam, while the beams from the other laser bars 34-4, 34-5, 34-6 are undeflected to form the leading line beam.
  • the optical element 120 of FIG. 16 is a mirror rather than a prism
  • the angle of the optical element 120 relative to the beam direction emerging from each laser bar 34 is A/2, as in the embodiment of FIG. 15.
  • FIGS. 17 and 18 depict a modification of the embodiment of FIGS. 7 and 8, in which the prisms 44 are eliminated and, instead, different (i.e., alternate) ones of the half-cylindrical lenses 40 are rotated through the angle A. Rotating the selected cylindrical lenses 40 produces the same beam deflection as did the prisms 44 of FIGS. 7 and 8.
  • the half-cylindrical lenses 40 are mounted on the respective laser bars 34 and aligned to produce the desired beam direction and then bonded to the laser bars, preferably with UV curable epoxy.
  • half the lenses (40-1, 40-3, 40-5) are aligned to provide a beam direction deflected by the angle A, while the remaining lenses 40-2, 40-4, 40-6 are aligned to provide an undeflected beam direction.
  • FIG. 19 depicts a modification of the embodiment of FIG. 10 in which the prisms 44-1, 44-2, 44-3 of successively greater beam angles are eliminated and their beam deflection functions are provided instead by rotating corresponding ones of the half-cylindrical lenses (40-1, 40-2, 40-3) through successively greater angles Al, A2, A3.
  • the lens 40-0 remains unrotated, to provide four successive beam angles of 0, Al, A2 and A3. This is identical to the succession of beam angles provided to the optics 42, 52, in the embodiment of FIG. 10.
  • FIG. 20 depicts a modification of the embodiment of FIG.

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  • Physics & Mathematics (AREA)
  • Optics & Photonics (AREA)
  • Engineering & Computer Science (AREA)
  • Plasma & Fusion (AREA)
  • Mechanical Engineering (AREA)
  • Condensed Matter Physics & Semiconductors (AREA)
  • General Physics & Mathematics (AREA)
  • Electromagnetism (AREA)
  • Recrystallisation Techniques (AREA)

Abstract

L'invention porte sur un appareil de recuit à surface dynamique qui permet d'effectuer le recuit d'une pièce à semiconducteur, lequel appareil comprend : un support de pièce destiné à soutenir une pièce; une source optique et un appareil de balayage destiné à faire balayer le support de pièce par la source optique le long d'un axe fixe. La source optique comprend un réseau d'émetteurs laser généralement agencés en rangées successives, les rangées étant transversales par rapport à l'axe rapide. De multiples lentilles de collimation de petite taille sont superposées à des rangées respectives d'émetteurs et possèdent un sens de collimation qui s'étend le long de l'axe rapide. La source optique comprend en outre un élément de déflexion optique d'axe rapide associé à des rangées choisies d'émetteurs, qui possède un angle ou une succession d'angles de déflexion optique correspondant aux déflexions de faisceau le long de l'axe rapide pour des rangées respectives d'émetteurs. Une optique focalise la lumière en provenance du réseau d'émetteurs laser sur une surface de la pièce afin de former une succession de faisceaux linéaires transversaux par rapport à l'axe rapide, espacés le long de l'axe rapide conformément à la succession d'angles de déflexion.
PCT/US2007/017684 2006-08-23 2007-08-08 Mise en forme de profil de faisceau à axe fixe pour système de recuit à diodes laser haute puissance WO2008024211A2 (fr)

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FR3012264A1 (fr) * 2013-10-21 2015-04-24 Saint Gobain Appareil laser modulaire
US10811286B2 (en) * 2016-09-28 2020-10-20 Sakai Display Products Corporation Laser annealing device and laser annealing method

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US6556352B2 (en) * 2000-08-23 2003-04-29 Apollo Instruments Inc. Optical coupling system
US6771686B1 (en) * 1999-08-21 2004-08-03 Laserline Gesellschaft Fur Entwicklung Und Vertrieb Optical arrangement for the use during a laser diode arrangement as well as laser diode arrangement with such an optical arrangement
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US4710911A (en) * 1984-04-27 1987-12-01 Matsushita Electric Industrial Co., Ltd. Method for recording, reproducing and erasing optical information
US6044096A (en) * 1997-11-03 2000-03-28 Sdl, Inc. Packaged laser diode array system and method with reduced asymmetry
US6771686B1 (en) * 1999-08-21 2004-08-03 Laserline Gesellschaft Fur Entwicklung Und Vertrieb Optical arrangement for the use during a laser diode arrangement as well as laser diode arrangement with such an optical arrangement
US6556352B2 (en) * 2000-08-23 2003-04-29 Apollo Instruments Inc. Optical coupling system
US20060262408A1 (en) * 2005-05-23 2006-11-23 Fuji Photo Film Co., Ltd. Linear light beam generating optical system

Cited By (9)

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Publication number Priority date Publication date Assignee Title
FR3012264A1 (fr) * 2013-10-21 2015-04-24 Saint Gobain Appareil laser modulaire
WO2015059388A1 (fr) * 2013-10-21 2015-04-30 Saint-Gobain Glass France Appareil laser modulaire
CN105658371A (zh) * 2013-10-21 2016-06-08 法国圣戈班玻璃厂 模块化激光装置
KR20160073376A (ko) * 2013-10-21 2016-06-24 쌩-고벵 글래스 프랑스 모듈형 레이저 장치
US9753290B2 (en) 2013-10-21 2017-09-05 Saint Gobain Glass France Modular laser apparatus
EA030536B1 (ru) * 2013-10-21 2018-08-31 Сэн-Гобэн Гласс Франс Модульный лазерный аппарат
TWI635533B (zh) * 2013-10-21 2018-09-11 法國聖戈本玻璃公司 模組化雷射設備
KR102229320B1 (ko) 2013-10-21 2021-03-19 쌩-고벵 글래스 프랑스 모듈형 레이저 장치
US10811286B2 (en) * 2016-09-28 2020-10-20 Sakai Display Products Corporation Laser annealing device and laser annealing method

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TW200816321A (en) 2008-04-01

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