CN116913768B - Multiple pulse sub-melting excimer laser annealing method - Google Patents
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- 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
- H01L21/04—Manufacture or treatment of semiconductor devices or of parts thereof the devices having at least one potential-jump barrier or surface barrier, e.g. PN junction, depletion layer or carrier concentration layer
- H01L21/18—Manufacture or treatment of semiconductor devices or of parts thereof the devices having at least one potential-jump barrier or surface barrier, e.g. PN junction, depletion layer or carrier concentration layer the devices having semiconductor bodies comprising elements of Group IV of the Periodic System or AIIIBV compounds with or without impurities, e.g. doping materials
- H01L21/26—Bombardment with radiation
- H01L21/263—Bombardment with radiation with high-energy radiation
- H01L21/268—Bombardment with radiation with high-energy radiation using electromagnetic radiation, e.g. laser radiation
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- 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
- H01L21/02686—Pulsed laser beam
Abstract
The invention belongs to the technical field of semiconductors, and particularly relates to a multi-pulse sub-melting excimer laser annealing method, which comprises the following steps: ion implantation is carried out on the surface of the semiconductor crystal, and an amorphous doping area is formed on the surface of the semiconductor crystal; and carrying out pulse laser irradiation annealing for a plurality of times on the amorphous doped region so as to enable the amorphous doped region to be recrystallized in a sub-melting state and activate ions of the amorphous doped region. Meanwhile, the impurity segregation effect caused by surface ablation, evaporation effect and melt cooling regeneration is avoided, so that the doping atom loss in the recrystallization process is greatly reduced.
Description
Technical Field
The invention belongs to the technical field of semiconductors, and particularly relates to a multi-pulse sub-melting excimer laser annealing method.
Background
With the rapid development of semiconductor devices, the higher the requirements on the performance thereof, and thus, the more specific requirements are put on the processing technology thereof. For example, as the feature size of semiconductor chips is continuously reduced, the source and drain regions of transistors require lower resistance and ultra-shallow junction (USJ) to reduce short channel effects, i.e., shallower doping depths, and higher doping concentrations. Methods for forming shallow junctions by lowering the energy of the implanted ions have been appreciated in the art, while the preparation of highly active USJ has become a major challenge for modern doping processes, requiring extremely low ion implantation energies and ultra-high doping concentrations.
In the related art, in order to form a high-activation shallow junction profile, low-energy beam ion implantation techniques and immersion plasma implantation techniques are widely used in semiconductor wafers to introduce dopants. Flash annealing (flash lamp annealing, FLA) and spike-rapid thermal annealing (spike-RTA) are used after implantation is complete to eliminate implantation damage and activate dopants. However, FLA and spike-RTA are not suitable for forming ultra-shallow junctions with high activation levels due to long annealing times and limited impurity activation.
In the field of semiconductors, research on silicon-based efficient luminescent materials and devices is one of hot spots, and a preparation method of a direct band gap silicon-based luminescent material compatible with a silicon CMOS process has been proposed in the prior art, and an ion implantation technology is utilized to put inert atoms with concentration exceeding 1% into crystal germanium to promote lattice expansion of the crystal germanium to generate equivalent tensile strain, so that conversion from an indirect band gap to a direct band gap is realized, and efficient luminescence is realized. In addition, direct bandgap luminescence can also be achieved by electron doping with a specific concentration of germanium or tin atoms placed in the germanium to form a split [110] interstitial site. However, the equilibrium solid solubility in single crystal germanium is much less than 1% whether the inert gas atoms of the closed shell are doped or the germanium atoms and tin atoms of the isoelectron are doped, which can result in a large number of dopant atoms escaping from the surface when repairing lattice damage caused by doping.
Single pulse excimer laser annealing (Excimer Laser Annealing, ELA) techniques can recrystallize damaged semiconductor materials and activate the impurities. The nanosecond annealing period can greatly shorten the annealing time and improve the annealing temperature, so that the method has higher impurity activation efficiency, and the effective annealing depth can be accurately controlled by the laser energy density. Therefore, the single pulse excimer laser annealing technology has great application potential in the aspect of preparing the low-resistance ultra-shallow junction.
However, further studies have found that single shot single pulse excimer laser annealing processes typically require a higher laser energy density to activate the dopant. This brings the surface of the material matrix in a molten state, and a high quality recycled layer is obtained by a liquid phase epitaxial crystallization mechanism in a rapid cooling process, and the high temperature melting-cooling crystallization mechanism has the inherent defects: on the one hand, the fused doped layer can cause the surface fluctuation of the substrate during the rapid solidification and crystallization, thereby leading to the coarsening or uneven fluctuation of the regenerated substrate surface, and being unfavorable for the device preparation. On the other hand, dopants are redistributed in the melt and partially lost during rapid cooling crystallization, thus facing serious dopant atom loss problems during annealing processes using single pulse excimer laser annealing techniques.
Therefore, an annealing technology is provided, which has far-reaching significance in the preparation of ultra-shallow junctions with low resistance and high activation and direct band gap silicon-based luminescent materials.
Disclosure of Invention
In view of the above, in order to solve at least one technical problem in the related art and other aspects, the present invention provides a multiple pulse sub-melting excimer laser annealing method, including: ion implantation is carried out on the surface of the semiconductor crystal, and an amorphous doping area is formed on the surface of the semiconductor crystal; and carrying out pulse laser irradiation annealing for a plurality of times on the amorphous doped region so as to enable the amorphous doped region to be recrystallized in a sub-melting state and activate ions of the amorphous doped region.
According to an embodiment of the present invention, the recrystallization process is a layer-by-layer recrystallization from the crystalline region to the amorphous doped region in a solid phase epitaxial crystallization.
According to an embodiment of the present invention, the energy density of the pulsed laser irradiation is 80% to 95% of the melting threshold of the semiconductor crystal.
According to an embodiment of the invention, the frequency of the pulsed laser irradiation is less than 20Hz.
According to an embodiment of the present invention, the pulsed laser includes one of an excimer nanosecond pulsed laser, a femtosecond pulsed laser, and a millisecond pulsed laser.
According to the embodiment of the invention, during the recrystallization process, the energy density of the pulse laser irradiation is gradually increased to compensate the influence of the reflectivity and the thermal absorption coefficient change of the amorphous doped region on the recrystallization rate.
According to an embodiment of the present invention, the semiconductor crystal includes one of an elemental semiconductor, a compound semiconductor, preferably one of silicon, germanium, silicon carbide, gallium nitride.
According to an embodiment of the present invention, the semiconductor crystal structure type includes a bulk structure or a thin film structure.
According to an embodiment of the present invention, the doping type of the amorphous doped region includesnDoping,pOne of type doping, isoelectron doping, and inert gas atom doping; preferably, the inert gas atoms are argon atoms.
According to an embodiment of the present invention, the ion implantation includes a beam-line ion implantation method or a plasma immersion ion implantation method.
According to an embodiment of the invention, the thickness of the amorphous doped region is less than 300nm.
According to the embodiment of the invention, the amorphous doped region subjected to ion implantation is always kept in a solid phase state in the recrystallization process by the multi-pulse sub-melting excimer laser annealing method, the extremely low diffusion rate in the solid phase enables the ion implantation distribution to be basically not influenced by thermal annealing, and the impurity segregation effect caused by surface ablation, evaporation effect and melt cooling regeneration is avoided, so that the doped atom loss in the recrystallization process is greatly reduced. Meanwhile, the amorphous doped region is in a sub-melting state, so that the phenomenon of substrate surface fluctuation and coarsening caused by melting fluctuation in the liquid phase epitaxy crystallization process is avoided, and the planar morphology characteristic similar to that of the initial implantation surface can be obtained after recrystallization.
Drawings
FIG. 1 is a flow chart of a multiple pulse sub-melt excimer laser annealing method in accordance with an embodiment of the present invention;
FIG. 2 is a schematic diagram of recrystallization of a multiple pulse sub-melt excimer laser annealing process according to an embodiment of the present invention;
FIG. 3 is a flow chart of a multiple pulse sub-melting excimer laser annealing process after argon ion implantation onto the germanium substrate surface in accordance with one embodiment of the present invention; wherein, (a) is a schematic diagram of a matrix, (b) is a schematic diagram of argon atom injection, and (c) is a schematic diagram of multiple pulse sub-melting excimer laser annealing;
FIG. 4 is a high resolution transmission electron micrograph of the surface of a germanium substrate after argon ion implantation in accordance with an embodiment of the present invention;
FIG. 5 is a high resolution transmission electron micrograph of the surface of a germanium substrate after multipulse sub-fusion excimer pulse laser annealing in accordance with one embodiment of the present invention;
fig. 6 is a graph showing Ar atom doping profile after single-pulse liquid phase epitaxial crystallization and multipulse sub-melt solid phase epitaxial crystallization of a base germanium material according to an embodiment of the present invention.
Reference numerals
1. A base;
2. an amorphous doped region;
3. an amorphous doping interface;
4. multiple pulses of sub-melt excimer laser.
Detailed Description
The present invention will be further described in detail below with reference to specific embodiments and with reference to the accompanying drawings, in order to make the objects, technical solutions and advantages of the present invention more apparent.
The endpoints of the ranges and any values disclosed in the present invention are not limited to the precise range or value, and the range or value should be understood to include values close to the range or value. For numerical ranges, one or more new numerical ranges may be obtained in combination with each other between the endpoints of each range, between the endpoint of each range and the individual point value, and between the individual point values, and are to be considered as specifically disclosed in the present invention.
The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The terms "comprises," "comprising," and/or the like, as used herein, specify the presence of stated features, steps, operations, and/or components, but do not preclude the presence or addition of one or more other features, steps, operations, or components.
All terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art unless otherwise defined. It should be noted that the terms used herein should be construed to have meanings consistent with the context of the present specification and should not be construed in an idealized or overly formal manner.
Similarly, in the foregoing description of exemplary embodiments of the invention, various features of the invention are sometimes grouped together in a single embodiment, figure, or description thereof for the purpose of streamlining the disclosure and aiding in the understanding of one or more of the various disclosed aspects. The description of the terms "one embodiment," "some embodiments," "example," "specific examples," or "some examples," etc., means that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the invention. In this specification, schematic representations of the above terms do not necessarily refer to the same embodiments or examples. Furthermore, the particular features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.
In the conventional laser annealing process, three main factors causing the loss of doping atoms include a surface ablation effect when high-energy laser is irradiated, a surface evaporation effect when a substrate is melted, and an impurity segregation effect when the melt is cooled and regenerated. Under the combined action of the factors, the single pulse excimer laser annealing process enables the doping atoms which are remained in the semiconductor substrate after annealing and recrystallization and are effectively activated to be greatly reduced.
When the semiconductor matrix material is irradiated by nanosecond pulse laser energy which is higher than the melting threshold value, the surface of the semiconductor matrix material is molten, and the melting front rapidly penetrates into the semiconductor matrix material (10 m/s) until the irradiation is finished. The surface melt layer is then solidified and crystallized by releasing heat to the semiconductor substrate, the melting front is rapidly swept back to the surface again, and the entire process is completed in tens of nanoseconds, which is called unbalanced liquid phase epitaxial crystallization. The surface ablation effect caused by laser irradiation, the surface evaporation effect generated by high-temperature melt and the impurity segregation effect caused by melt cooling regeneration all cause doping atom loss in the whole melting-crystallization process.
To solve this problem, those skilled in the art have proposed depositing a dielectric protective layer of a specific thickness on the surface of the substrate prior to treatment by the single pulse excimer laser annealing (Excimer Laser Annealing, ELA) technique. However, subsequent studies have found that such protective layers, when subjected to high energy ELA treatment, introduce undesirable impurities into the substrate as a source of impurity contamination, through interaction with existing impuritiesnOr (B)pCombined with impuritiesAnd the latter is largely deactivated. Surface deposition of a dielectric layer is therefore not an ideal solution. Because no proper annealing scheme is found yet, the traditional single pulse excimer laser annealing has difficulty in playing its advantageous role in the preparation of low-resistance high-activation USJ and direct band gap silicon-based luminescent materials, so that the application of the single pulse excimer laser annealing in the technical fields of future front-edge microelectronics and optoelectronics is greatly limited.
In the invention, the amorphous doped region is irradiated continuously and repeatedly by pulse laser energy slightly lower than the melting threshold value of the amorphous doped region, so that the amorphous doped region is always in a solid phase in the recrystallization process, and the recrystallization growth is realized in a solid phase epitaxial crystallization mode. The doping atoms in the solid phase state have extremely low diffusion rate, so that the ion implantation distribution is basically not influenced by thermal annealing, and therefore, the surface ablation effect caused by irradiation, the surface evaporation effect of a melt and the impurity segregation effect caused by cooling and regeneration can be effectively inhibited.
FIG. 1 is a flow chart of a multiple pulse sub-melt excimer laser annealing method in accordance with an embodiment of the present invention.
The disclosure provides a multi-pulse sub-melting excimer laser annealing method, as shown in fig. 1, comprising the following steps S1 and S2.
Step S1: ion implantation is carried out on the surface of the semiconductor crystal, and an amorphous doping region is formed on the surface of the semiconductor crystal.
Step S2: and carrying out pulse laser irradiation annealing for a plurality of times on the amorphous doped region so as to enable the amorphous doped region to be recrystallized in a sub-melting state and activate ions of the amorphous doped region.
According to the embodiment of the invention, the amorphous doped region subjected to ion implantation is always kept in a solid phase state in the recrystallization process by the multi-pulse sub-melting excimer laser annealing method, the extremely low diffusion rate in the solid phase form enables ion implantation distribution to be basically not influenced by thermal annealing, and the impurity segregation effect caused by surface ablation, evaporation effect and melt cooling regeneration is avoided, so that the doped atom loss phenomenon in the recrystallization process is greatly reduced. Meanwhile, the amorphous doped region is in a sub-melting state, so that the phenomenon of substrate surface fluctuation and coarsening caused by melting fluctuation in the liquid phase epitaxy crystallization process is avoided, and the planar morphology characteristic similar to that of the initial implantation surface can be obtained after recrystallization.
FIG. 2 is a schematic diagram of recrystallization of a multiple pulse sub-melt excimer laser annealing process according to an embodiment of the present invention.
According to an embodiment of the present invention, as shown in fig. 2, as the amorphous doped region 2 is recrystallized, the amorphous doped interface 3 moves. According to the Arrhenius theory model, atoms at the amorphous doping interface 3 can only migrate a distance of a few atomic layers at each pulse, which means that the crystallization depth that each pulse can trigger is about a few atomic layers. Therefore, in order to completely complete recrystallization of the entire doped layer, the substrate needs to be subjected to multi-pulse continuous irradiation in a sub-melt crystallization mode.
According to the embodiment of the invention, the recrystallization thickness can be regulated by changing the pulse times.
According to an embodiment of the present invention, the recrystallization process is a layer-by-layer recrystallization from the crystalline region to the amorphous doped region 2 in a solid phase epitaxial crystallization manner.
According to the embodiment of the invention, the recrystallization direction of the amorphous doped region moves from the crystal region to the amorphous doped region 2 under the action of the multi-pulse sub-melting excimer laser annealing, i.e. the amorphous doped interface 3 moves from the crystal region to the amorphous doped region 2. The thickness of recrystallization is precisely controlled by the number of pulses to realize the crystallization effect of buried layers, thereby meeting the crystallization requirement of specific fields.
According to an embodiment of the present invention, when the amorphous doped region is irradiated with pulse laser energy below the melting threshold of the amorphous doped region, the surface thereof rapidly rises to a sub-melting state, and after each pulse is finished, the amorphous doped region is cooled by releasing heat to the bottom substrate, so that the recrystallization direction is from bottom to top (i.e., the crystal region moves toward the amorphous doped region).
According to an embodiment of the present invention, the energy density of the pulsed laser irradiation is 80% to 95%, for example, alternatively 80%, 83%, 85%, 90%, 93%, etc., preferably 90%, of the melting threshold of the semiconductor crystal.
According to the embodiment of the invention, the energy density of the pulse laser is slightly lower than the melting threshold of the amorphous doped region, so that the amorphous doped region is always in a sub-melting state under the irradiation effect. The more thoroughly the amorphous doped region is amorphized, the higher the defect content, the stronger the corresponding thermal absorption coefficient, and the lower the required laser energy density. In addition, the deeper the amorphous doped region, the higher the thermal penetration requirement for the laser, the higher the laser energy density required. Thus, for a particular matrix material, the optimized laser energy density depends on the implant depth and defect content.
According to an embodiment of the invention, the frequency of the pulsed laser irradiation is less than 20Hz, e.g. optionally 5Hz, 8Hz, 10Hz, 13Hz, 16Hz, 18Hz, etc.
According to embodiments of the present invention, during multiple pulse sub-melt excimer laser annealing, the effect of each pulse on the substrate should be independent, i.e., not affect each other between each pulse. However, since the thermal diffusion efficiency of the substrate is limited, the heat accumulation effect of the multi-pulse irradiation may cause the substrate to undergo surface melting phenomenon, and thus the pulse frequency should not be too high. On the other hand, in order to shorten the annealing time to meet the industrial application needs, the laser irradiation frequency should not be too low. After comprehensively considering the surface heat effect and the annealing time cost, the incidence frequency set in the invention is generally smaller than 20Hz, and the specific numerical value depends on factors such as the type of the matrix material, the injection damage degree, the incidence laser parameters and the like.
According to an embodiment of the present invention, the number of pulses of the multiple pulse sub-melt excimer laser anneal should be such that the amorphous doped regions are fully crystallized.
According to an embodiment of the present invention, the pulsed laser includes one of an excimer nanosecond pulsed laser, a femtosecond pulsed laser, and a millisecond pulsed laser.
According to the embodiment of the invention, the multi-pulse sub-melting excimer laser annealing method provided by the invention essentially belongs to solid phase epitaxial crystallization, but the ultra-fast heating and cooling rate caused by nanosecond pulse enables the multi-pulse sub-melting excimer laser annealing method to have unbalanced doping characteristics.
According to the embodiment of the invention, during the recrystallization process, the energy density of the pulse laser irradiation is gradually increased to compensate the influence of the reflectivity and the thermal absorption coefficient change of the amorphous doped region on the recrystallization rate.
According to the embodiment of the invention, as the recrystallization process is continuously carried out, the residual depth of the amorphous doped region is continuously thinned, the reflectivity of the substrate surface to the incident laser and the thermal absorption coefficient thereof are also continuously changed, and the crystallization rate is slightly reduced under the condition that the laser irradiation energy is unchanged. Therefore, in order to obtain a uniform recrystallization rate and to facilitate precise control of the recrystallization thickness, the laser irradiation energy density can be gradually increased during the annealing process, so as to compensate the influence of the change of the reflectivity and the heat absorption coefficient on the recrystallization rate.
According to an embodiment of the present invention, the semiconductor crystal includes one of an elemental semiconductor, a compound semiconductor, preferably one of silicon, germanium, silicon carbide, gallium nitride.
According to an embodiment of the present invention, the semiconductor crystal structure type includes a bulk structure or a thin film structure, wherein the thin film structure includes, but is not limited to, SOI (Silicon-On-Insulator) or GOI (Germanium-On-Insulator).
According to an embodiment of the present invention, the doping type of the amorphous doped region includes one of n-type doping, p-type doping, isoelectric doping, inert gas atomic doping; preferably, the inert gas atoms are selected to be argon atoms when applied to a silicon-based light emitting device.
According to embodiments of the present invention, to prevent the formation of bubble structures in the substrate by inert atom implantation, the inert atom implantation dose is generally less than 5×10 16 /cm 2 。
According to an embodiment of the present invention, the ion implantation includes a beam-line ion implantation method or a plasma immersion ion implantation method.
According to an embodiment of the invention, the thickness of the amorphous doped region is less than 300nm.
According to the embodiment of the invention, in order to rapidly judge whether the amorphous doped region is completely recrystallized after multiple pulse sub-melting excimer laser annealing in an industrial line, online nondestructive Raman (Raman), X-ray diffraction (XRD) or photoinduced spectrum (PL) test analysis can be directly carried out on a sample, and the sample is compared with a high-quality single crystal matrix result collected in advance under the same test condition, and whether high-quality epitaxial crystallization is realized is judged by utilizing the corresponding characteristic peak half-width or intensity change.
It should be noted that the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, other embodiments that may be obtained by those of ordinary skill in the art without making any inventive effort are within the scope of the present invention.
Examples:
in this example, a multiple pulse sub-melt excimer laser annealing process of inert atom Ar doped amorphous base germanium material is schematically illustrated.
FIG. 3 is a flow chart of a multiple pulse sub-melting excimer laser annealing process after argon ion implantation onto a germanium substrate surface in accordance with one embodiment of the present invention.
Step S101: as the base 1, semiconductor bulk germanium was prepared as shown in fig. 3 (a). Wherein the size of the matrix 1 is 2 inches, the resistance is 0.01-0.05Ω -cm, and the crystal phase is<110>The melting threshold of fully amorphized germanium is about 350mJ/cm 2 。
Step S102: an inert atom Ar injection is performed on one side of the substrate 1 to form a layer of Ar atom amorphous doped region 2 of a specific depth, as shown in (b) of FIG. 3. Wherein Ar atoms are injected into the substrate 1 by adopting an immersion type plasma ion injection technology, the injection energy is 5kV, and the injection dosage is 1 multiplied by 10 16 /cm 2 The working pressure of Ar gas in the injection cavity is 10 -3 Pa, the discharge power was 500W, the pulse width of the rectangular voltage for discharge was 10. Mu.s, and the pulse frequency was 1kHz.
Fig. 4 is a high resolution transmission electron micrograph of the surface of a germanium substrate after argon ion implantation in accordance with an embodiment of the invention.
As shown in fig. 4, the surface of the substrate 1 is completely amorphized to a depth of about 15nm, and the underlying lattice in contact with the substrate is well arranged with a clear transition interface therebetween.
Step S103: the amorphous doped region 2 is subjected to multi-pulse sub-melting irradiation by using an excimer nanosecond pulse laser, and the amorphous doped interface 3 moves from bottom to top to be completely recrystallized, as shown in (c) of fig. 3. Wherein, the XeCl excimer nanosecond pulse laser annealing system is provided with a beam homogenizer, the size of the beam cross section is 5mm multiplied by 5mm, and the energy distribution is uniform. The wavelength of XeCl excimer nanosecond pulse laser is 308nm, the pulse period is 28ns, and the energy density of the adopted laser is 300mJ/cm 2 The pulse frequency was 8Hz and the number of pulses was 500.
Fig. 5 is a high resolution transmission electron micrograph of the surface of a germanium substrate after multipulse sub-fusion excimer pulse laser annealing in accordance with one embodiment of the present invention.
As shown in fig. 5, after the multi-pulse sub-melting laser irradiation treatment, the amorphous doped region on the germanium surface of the substrate 1 completely disappears, the germanium lattice arrangement is effectively recovered, and no residual lattice defect exists, which means that the amorphous doped region realizes high-quality epitaxial crystallization under the sub-melting multi-pulse laser annealing effect.
To confirm the Ar atom doping content distribution in the matrix before and after the use of the multiple pulse sub-melting excimer laser annealing method in this example, a doping element analysis was performed using a Secondary Ion Mass Spectrometer (SIMS).
In contrast, the ion-implanted sample was subjected to liquid phase epitaxial crystallization by single pulse high energy excimer nanosecond pulse laser annealing with a laser energy density of 800mJ/cm 2 . Under the condition of pulse laser irradiation, the amorphous doped region is completely melted, and after the irradiation is finished, the melted layer takes the monocrystalline matrix as seed crystal to realize liquid phase epitaxy regeneration. The Ar atom doping profile after liquid phase epitaxial crystallization was also analyzed by SIMS technique, and the results are shown in fig. 6.
Fig. 6 is a graph showing Ar atom doping profile after single-pulse liquid phase epitaxial crystallization and multipulse sub-melt solid phase epitaxial crystallization of a base germanium material according to an embodiment of the present invention.
As shown in fig. 6, the Ar atom content in the matrix after high energy single-pulse liquid phase epitaxial crystallization is greatly reduced, especially near the doped surface region. However, for solid phase epitaxy crystallization induced by the multi-pulse sub-melting mode, the doping loss phenomenon is greatly suppressed, and especially in a surface high-concentration amorphous doping region, the Ar content loss degree is lower.
As previously mentioned, this is associated with a low diffusion rate of inert atoms in the solid phase matrix and an ultra high crystallization rate, i.e. a large number of Ar atoms in the amorphous layer do not have enough time to escape from the matrix to be trapped by the crystallization interface moving from bottom to top during the multipulse ultrafast solid phase epitaxial crystallization. Due to the presence of atoms of a relatively inert gas, conventionalnA kind of electronic device with a display unit、pThe electron-type or isoelectron-type doping atoms can form a bond with the matrix stably, and can be captured by the regenerated matrix to enter lattice substitution sites in the recrystallization process.
Therefore, impurity loss can be further reduced when the multi-pulse sub-melting mode crystallization is adopted for the doping atoms of the type, thereby being beneficial to realizing the doping with ultrahigh solid solubility.
In the invention, the ion implantation technology and the multipulse sub-melting laser annealing technology are compatible with the CMOS technology and can be used in the existing semiconductor technology industry on a large scale, so the novel annealing technology becomes an advantageous scheme for preparing low-resistance USJ and novel direct band gap luminescent silicon-based materials in the future.
The foregoing description of the embodiments has been provided for the purpose of illustrating the general principles of the invention, and is not meant to limit the invention thereto, but to limit the invention thereto, and any modifications, equivalents, improvements and equivalents thereof may be made without departing from the spirit and principles of the invention.
Claims (9)
1. A multiple pulse sub-melt excimer laser annealing method, comprising:
ion implantation is carried out on the surface of the semiconductor crystal, and an amorphous doping area is formed on the surface of the semiconductor crystal;
performing pulse laser irradiation annealing for a plurality of times on the amorphous doped region so as to enable the amorphous doped region to be recrystallized in a sub-melting state and activate ions of the amorphous doped region; wherein,
the doping type of the amorphous doping region comprises one of n-type doping, p-type doping, isoelectric doping and inert gas atom doping;
the energy density of the pulse laser irradiation is 80% -95% of the melting threshold of the semiconductor crystal; the frequency of the pulse laser irradiation is less than 20Hz;
and in the recrystallization process, gradually increasing the energy density of the pulse laser irradiation so as to compensate the influence of the reflectivity and the thermal absorption coefficient change of the amorphous doped region on the recrystallization rate.
2. The multiple pulse sub-fusion excimer laser annealing process of claim 1, wherein the recrystallization process is a layer-by-layer recrystallization from a crystalline region to the amorphous doped region in a solid phase epitaxial crystallization.
3. The multiple pulse sub-melt excimer laser annealing method of claim 1, wherein the pulsed laser comprises one of an excimer nanosecond pulsed laser, a femtosecond pulsed laser, and a millisecond pulsed laser.
4. The multiple pulse sub-fusion excimer laser annealing method of claim 1, wherein the semiconductor crystal comprises one of an elemental semiconductor and a compound semiconductor.
5. The multiple pulse sub-melt excimer laser annealing process of claim 4, wherein the semiconductor crystal comprises one of silicon, germanium, silicon carbide, gallium nitride.
6. The multiple pulse sub-melt excimer laser annealing process of claim 1, wherein the semiconductor crystal structure type comprises a bulk structure or a thin film structure.
7. The multiple pulse sub-fusion excimer laser annealing process of claim 1, wherein the inert gas atoms doping the amorphous doped regions are argon atoms.
8. The multiple pulse sub-fusion excimer laser annealing process of claim 1, wherein the ion implantation comprises a beam-line ion implantation process or a plasma immersion ion implantation process.
9. The multiple pulse sub-melt excimer laser annealing process of claim 1, wherein the amorphous doped region has a thickness of less than 300nm.
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