WO2011034284A2 - Epi wafer and silicon single crystal ingot for the same and fabrication method thereof - Google Patents

Epi wafer and silicon single crystal ingot for the same and fabrication method thereof Download PDF

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WO2011034284A2
WO2011034284A2 PCT/KR2010/005306 KR2010005306W WO2011034284A2 WO 2011034284 A2 WO2011034284 A2 WO 2011034284A2 KR 2010005306 W KR2010005306 W KR 2010005306W WO 2011034284 A2 WO2011034284 A2 WO 2011034284A2
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Prior art keywords
single crystal
nitrogen
epi
silicon
epi wafer
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PCT/KR2010/005306
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French (fr)
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WO2011034284A3 (en
WO2011034284A4 (en
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Young-Kyu Choi
Hwa-Jin Jo
Hee-Bok Gang
Kwang-Salk Kim
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Siltron Inc.
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Publication of WO2011034284A4 publication Critical patent/WO2011034284A4/en

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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
    • H01L21/02367—Substrates
    • C—CHEMISTRY; METALLURGY
    • C30—CRYSTAL GROWTH
    • C30B—SINGLE-CRYSTAL GROWTH; UNIDIRECTIONAL SOLIDIFICATION OF EUTECTIC MATERIAL OR UNIDIRECTIONAL DEMIXING OF EUTECTOID MATERIAL; REFINING BY ZONE-MELTING OF MATERIAL; PRODUCTION OF A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; SINGLE CRYSTALS OR HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; AFTER-TREATMENT OF SINGLE CRYSTALS OR A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; APPARATUS THEREFOR
    • C30B15/00—Single-crystal growth by pulling from a melt, e.g. Czochralski method
    • C30B15/02—Single-crystal growth by pulling from a melt, e.g. Czochralski method adding crystallising materials or reactants forming it in situ to the melt
    • C30B15/04—Single-crystal growth by pulling from a melt, e.g. Czochralski method adding crystallising materials or reactants forming it in situ to the melt adding doping materials, e.g. for n-p-junction
    • C—CHEMISTRY; METALLURGY
    • C30—CRYSTAL GROWTH
    • C30B—SINGLE-CRYSTAL GROWTH; UNIDIRECTIONAL SOLIDIFICATION OF EUTECTIC MATERIAL OR UNIDIRECTIONAL DEMIXING OF EUTECTOID MATERIAL; REFINING BY ZONE-MELTING OF MATERIAL; PRODUCTION OF A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; SINGLE CRYSTALS OR HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; AFTER-TREATMENT OF SINGLE CRYSTALS OR A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; APPARATUS THEREFOR
    • C30B29/00—Single crystals or homogeneous polycrystalline material with defined structure characterised by the material or by their shape
    • C30B29/02—Elements
    • C30B29/06—Silicon
    • 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 potential barriers, e.g. a PN junction, depletion layer or carrier concentration layer
    • H01L21/18—Manufacture or treatment of semiconductor devices or of parts thereof the devices having potential barriers, e.g. a PN junction, depletion layer or carrier concentration layer the devices having semiconductor bodies comprising elements of Group IV of the Periodic Table or AIIIBV compounds with or without impurities, e.g. doping materials
    • H01L21/30—Treatment of semiconductor bodies using processes or apparatus not provided for in groups H01L21/20 - H01L21/26
    • H01L21/322—Treatment of semiconductor bodies using processes or apparatus not provided for in groups H01L21/20 - H01L21/26 to modify their internal properties, e.g. to produce internal imperfections
    • H01L21/3221—Treatment of semiconductor bodies using processes or apparatus not provided for in groups H01L21/20 - H01L21/26 to modify their internal properties, e.g. to produce internal imperfections of silicon bodies, e.g. for gettering
    • H01L21/3225—Thermally inducing defects using oxygen present in the silicon body for intrinsic gettering

Definitions

  • the present invention relates to an epitaxial (EPI) wafer, and more particularly, to an EPI wafer configured to prevent EPI stacking faults (ESFs) from occurring when forming bulk micro defects (BMDs) for suppressing contamination caused by metallic elements, and a silicon ingot for the same and a fabrication method thereof.
  • EPFs EPI stacking faults
  • BMDs bulk micro defects
  • Silicon single crystals produced by a single crystal growth process such as Czochralski method are processed into thin-film type wafers through subsequent several processes.
  • EPI wafers are typically fabricated by growing crystals of a compound semiconductor material on the frontside through an epitaxy growth process depending on the use of devices.
  • FIG. 1 shows a cross-sectional view of a typical EPI wafer.
  • the EPI wafer comprises a backside 10, a bulk 20 and a frontside 30 arranged upstream, and the fronside 30 has an active layer 40, i.e. a part related to the operation of a device.
  • Devices to which the EPI wafer is applied, are high performance products such as, for example, microprocessor units (MPUs), logic, optic ICs, CMOS image sensors (CISs) and so on, and as these exemplary devices are sensitive to contamination caused by, in particular, metallic elements, attention should be given to control metal contamination in order to prevent a decrease in the yield of devices.
  • MPUs microprocessor units
  • CISs CMOS image sensors
  • contamination control during a device fabrication process is important, but first of all, it needs metal contamination control during an EPI wafer fabrication process.
  • the active layer serves as a main operating area of a device, and accordingly, it is important to minimize contamination of the active layer caused by metallic elements.
  • a process for imparting a gettering function on the EPI wafer is generally performed.
  • the gettering treatment process is a technique for controlling the metal contamination level of an active layer by forming high-energy sites on a portion of the frontside other than the active layer, the bulk or the backside, and migrating metallic elements existing in the active layer to the high-energy sites.
  • a single crystal ingot growth method which dopes a P-type silicon melt with nitrogen in the silicon single crystal fabrication. Nitrogen reacts with vacancy, oxygen, etc. within the silicon single crystal to improve the BMD density. BMDs act as gettering sites within the bulk of the EPI wafer to enhance the gettering performance.
  • COPs 1 in the bulk have an octahedral morphology, and an EPI layer 2 is grown on the open COPs 1 without any ESF.
  • COPs 1 have a needle- or rod-shaped morphology and are as small as several tens of nm, and a number of ESFs 4 occur if an EPI layer 2 is formed on such open COPs 1.
  • ESFs occur to a maximum of 54 ea/wafer, relative to a 300 mm-diameter wafer, after an EPI growth process.
  • the open COPs 1 of about 20 nm size existing on the surface of the wafer induce a lattice misfit 3 during the EPI growth process, and this appears as ESFs 4 on the surface of the EPI layer due to a lattice misfit.
  • Korean Patent Laid-open Publication No. 2005-0019845 suggests a nitrogen concentration between 1x10 13 and 1x10 14 atoms/cm 3 to obtain a silicon wafer in which the density of void defects having an opening size of 20 nm or lower is 0.02 ea/cm 2 or less.
  • thermal treatment may be used to improve the density of BMDs, but, in this case, addition of a new process causes a rise in manufacturing costs and an increase in process control points.
  • the present invention is designed to solve the problems of the prior art, and therefore it is an object of the present invention to provide an EPI wafer with reduced occurrence of ESFs through control over the morphology of crystal defects in the bulk, and a silicon ingot for the same and a fabrication method thereof.
  • the present invention discloses an EPI wafer, in which the bulk is doped with nitrogen for generating BMDs, and the morphology of crystal defects is controlled to reduce the occurrence of ESFs, and a silicon ingot for the same and a fabrication method thereof.
  • an EPI wafer according to the present invention comprises a single crystal substrate and an EPI layer grown on the single crystal substrate, wherein the single crystal substrate is doped with nitrogen, and crystal defects in the single crystal substrate have an octahedral or overlapping kite-shaped morphology.
  • the nitrogen concentration is between 1x10 12 and 5x10 13 atoms/cm 3 .
  • the single crystal substrate is co-doped with nitrogen and carbon.
  • the nitrogen concentration is 2x10 12 atoms/cm 3 or higher
  • the carbon concentration is 0.5 ppma or lower.
  • the single crystal substrate may use a P(-) or P(+) crystal.
  • the density of ESFs observed on the surface of the EPI layer is preferably 0.007 ea/cm 2 or less.
  • a silicon single crystal ingot for an EPI wafer grown by the Czochralski(Cz) method in which the single crystal is doped with nitrogen and crystal defects in the single crystal have an octahedral or overlapping kite-shaped morphology.
  • the nitrogen concentration is preferably between 1x10 12 and 5x10 13 atoms/cm 3 .
  • the silicon single crystal may be co-doped with nitrogen and carbon.
  • the nitrogen concentration is 2x10 12 atoms/cm 3 or higher
  • the carbon concentration is 0.5 ppma or lower.
  • a method for fabricating a silicon single crystal ingot by the Czochralski method which grows a silicon single crystal ingot at a solid-liquid interface by melting a polycrystalline silicon contained in a quartz crucible to produce a silicon melt, dipping a single crystal seed into the silicon melt and slowly pulling up the single crystal seed from the silicon melt while rotating the single crystal seed, the method comprising adding nitrogen to the silicon melt, and controlling the nitrogen concentration to obtain a single crystal with octahedral or overlapping kite-shaped morphology of crystal defects.
  • the nitrogen concentration is set between 1x10 12 and 5x10 13 atoms/cm 3 .
  • nitrogen and carbon co-doping may be carried out.
  • the nitrogen concentration is preferably set to 2x10 12 atoms/cm 3 or higher, and the carbon concentration is preferably set to 0.5 ppma or lower.
  • the present invention can reduce the occurrence of ESFs through control over the morphology of COPs in the bulk of an EPI wafer when doping with nitrogen to generate BMDs that act as gettering sites for preventing contamination caused by metallic elements.
  • the present invention sufficiently maintains the density of BMDs as well as reduces the occurrence of ESFs when doping with nitrogen, thereby improving the gettering performance.
  • FIG. 1 is a cross-sectional view of a typical EPI wafer.
  • FIG. 2 is a schematic view showing EPI layer growth structures of an undoped wafer and a wafer doped with nitrogen in the bulk.
  • FIG. 3 is an SEM image showing the COP morphology without control and under control over the morphology of COPs in the bulk of an EPI wafer according to a preferred embodiment of the present invention.
  • FIG. 4 is a Magics image showing ESFs observed before and after controlling the morphology of COPs according to a preferred embodiment of the present invention.
  • FIG. 5 is an SEM image showing the COP morphology in the case of a low carbon concentration and a high carbon concentration in carbon co-doping according to a preferred embodiment of the present invention.
  • An EPI wafer comprises a single crystal substrate and an EPI layer grown on the single crystal substrate, wherein the single crystal substrate is doped with nitrogen, and crystal originated particles (COPs), i.e. crystal defects have an octahedral or overlapping kite-shaped morphology. Since the basic internal structure of the EPI wafer is the same as previously described in FIG. 1, its detailed description is omitted herein.
  • COPs crystal originated particles
  • Nitrogen doped into the single crystal substrate generates BMDs in the bulk, and forms gettering sites for removal of metallic elements.
  • the nitrogen concentration is determined such that COPs have an octahedral or overlapping kite-shaped morphology as shown in FIG. 3(b).
  • the nitrogen concentration in the EPI wafer is preferably between 1x10 12 and 5x10 13 atoms/cm 3 . If the nitrogen concentration exceeds 5x10 13 atoms/cm 3 , COPs have a nearly needle- or rod-shaped morphology as shown in FIG. 3(a), resulting in occurrence of a large number of ESFs. In the contrast, if the nitrogen concentration is lower than 1x10 12 atoms/cm 3 , the BMD density is too low, resulting in insignificant gettering effect.
  • the nitrogen concentration is actually, for example, 2x10 14 atoms/cm 3
  • approximately 12 to 54 ea/wf of ESFs are observed on the surface of the EPI wafer relative to a 300 mm diameter wafer, as shown in FIG. 4(a).
  • COPs have a controlled morphology of an octahedral or overlapping kite-shaped structure by maintaining the nitrogen concentration in the range between 1x10 12 and 5x10 13 atoms/cm 3 , 5 ea/wf (0.007 ea/cm 2 , when converted into density) or les of ESFs are observed as shown in FIG. 4(b), which means an improvement in ESF suppression about 10 times, compared with the conventional art.
  • Controlling the morphology of COPs to an octahedral or overlapping kite-shaped structure reduces the generation of COPs having an opening size between 10 and 90 nm, thereby remarkably reducing the occurrence of ESFs.
  • the reduced occurrence of ESFs with the change of nitrogen concentration as mentioned above is caused by the fact that the open COPs on the surface of a single crystal substrate have a larger opening size at a relatively lower nitrogen concentration than a relatively higher nitrogen concentration, and finally, the occurrence of lattice misfits is reduced.
  • the nitrogen concentration is lower than 1x10 12 atoms/cm 3
  • COPs have a completely octahedral morphology, but the BMD density is 1x10 8 ea/cm 3 or less, which is not enough to obtain a sufficient gettering effect.
  • the single crystal substrate with nitrogen and carbon. It secures sufficient BMDs in P(-) or P(+) crystals while not modifying the COP morphology when co-doping with carbon. And, the use of carbon compensates for oxidation-induced stacking faults (OiSFs) that may occur at an edge area of a wafer due to nitrogen doping.
  • OxiSFs oxidation-induced stacking faults
  • FIG. 5(a) shows the COP morphology in the case of a relatively lower carbon concentration
  • FIG. 5(b) shows the COP morphology in the case of a relatively higher carbon concentration. It can be seen through FIG. 5 that the COP morphology is maintained as an octahedral or overlapping kite-shaped structure, even though the carbon concentration is changed from low to high level. This effect is apparent when the nitrogen concentration is 2x10 12 atoms/cm 3 or higher and the carbon concentration is 0.5 ppma or lower.
  • the EPI wafer of the above-mentioned configuration is fabricated in such a way that a silicon single crystal ingot is grown by the Czochralski method and cut into silicon single crystal wafers by a subsequent process such as slicing and so on, and an EPI layer is grown on the frontside of the silicon single crystal wafer.
  • a polycrystalline silicon raw material loaded in a quartz crucible is melt into a P-type silicon melt, and a single crystal seed is dipped in the silicon melt and then slowly pulled upwards and rotated at the same time, so that a single crystal is grown at a solid-liquid interface.
  • nitrogen or nitrogen/carbon is added to the silicon melt in order to control the COP morphology of the single crystal to an octahedral or overlapping kite-shaped structure.
  • the nitrogen concentration is preferably maintained in the range between 1x10 12 and 5x10 13 atoms/cm 3 , and in the case of co-doping with nitrogen and carbon, the nitrogen concentration is preferably maintained at 2x10 12 atoms/cm 2 or higher and the carbon concentration is maintained at 0.5 ppma or lower.
  • the silicon single crystal ingot fabricated by the above-mentioned process has a sufficient density of BMDs generated by nitrogen doping, which act as gettering sites for preventing contamination by metallic elements, and the COPs of an overlapping kite-shaped morphology, more preferably of an octahedral morphology, so that the density of ESFs can be maintained at 0.007 ea/cm 2 or less.
  • the present invention can reduce ESFs occurring when doping with nitrogen to generate BMDs, by controlling the morphology of COPs in an EPI wafer, resulting in improvement of quality of devices employing the EPI wafer.

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Abstract

An EPI wafer according to the present invention includes a single crystal substrate and an EPI layer grown on the single crystal substrate, wherein the single crystal substrate is doped with nitrogen, and crystal defects existing in the single crystal substrate have an octahedral or overlapping kite-shaped morphology.

Description

EPI WAFER AND SILICON SINGLE CRYSTAL INGOT FOR THE SAME AND FABRICATION METHOD THEREOF
The present invention relates to an epitaxial (EPI) wafer, and more particularly, to an EPI wafer configured to prevent EPI stacking faults (ESFs) from occurring when forming bulk micro defects (BMDs) for suppressing contamination caused by metallic elements, and a silicon ingot for the same and a fabrication method thereof.
<Cross-reference to related application>
This application claims priority to Korean Patent Application No. 10-2009-0086952 filed in Republic of Korea on September 15, 2009, the entire contents of which are incorporated herein by reference.
Silicon single crystals produced by a single crystal growth process such as Czochralski method are processed into thin-film type wafers through subsequent several processes. And, EPI wafers are typically fabricated by growing crystals of a compound semiconductor material on the frontside through an epitaxy growth process depending on the use of devices.
FIG. 1 shows a cross-sectional view of a typical EPI wafer. Referring to FIG. 1, the EPI wafer comprises a backside 10, a bulk 20 and a frontside 30 arranged upstream, and the fronside 30 has an active layer 40, i.e. a part related to the operation of a device.
Devices, to which the EPI wafer is applied, are high performance products such as, for example, microprocessor units (MPUs), logic, optic ICs, CMOS image sensors (CISs) and so on, and as these exemplary devices are sensitive to contamination caused by, in particular, metallic elements, attention should be given to control metal contamination in order to prevent a decrease in the yield of devices. For this purpose, contamination control during a device fabrication process is important, but first of all, it needs metal contamination control during an EPI wafer fabrication process.
In the EPI wafer, particularly the active layer serves as a main operating area of a device, and accordingly, it is important to minimize contamination of the active layer caused by metallic elements. For this purpose, a process for imparting a gettering function on the EPI wafer is generally performed. The gettering treatment process is a technique for controlling the metal contamination level of an active layer by forming high-energy sites on a portion of the frontside other than the active layer, the bulk or the backside, and migrating metallic elements existing in the active layer to the high-energy sites.
To provide an intrinsic gettering effect, one of gettering effects, a single crystal ingot growth method is widely used, which dopes a P-type silicon melt with nitrogen in the silicon single crystal fabrication. Nitrogen reacts with vacancy, oxygen, etc. within the silicon single crystal to improve the BMD density. BMDs act as gettering sites within the bulk of the EPI wafer to enhance the gettering performance.
However, on the other hand, nitrogen disadvantageously changes the morphology of crystal originated particles (COPs) within the bulk, which causes misfit dislocations during an EPI growth process, thereby resulting in EPI stacking faults (ESFs). In the context, EPI stacking structures without nitrogen doping (a) and with nitrogen doping (b) are shown in FIG. 2.
In FIG. 2(a), COPs 1 in the bulk have an octahedral morphology, and an EPI layer 2 is grown on the open COPs 1 without any ESF.
Meanwhile, in FIG. 2(b), as the bulk is doped with a high concentration of nitrogen, COPs 1 have a needle- or rod-shaped morphology and are as small as several tens of nm, and a number of ESFs 4 occur if an EPI layer 2 is formed on such open COPs 1. Generally, in the case of a wafer with a nitrogen concentration of 2x1014 atoms/cm3, ESFs occur to a maximum of 54 ea/wafer, relative to a 300 mm-diameter wafer, after an EPI growth process. According to analysis, the open COPs 1 of about 20 nm size existing on the surface of the wafer induce a lattice misfit 3 during the EPI growth process, and this appears as ESFs 4 on the surface of the EPI layer due to a lattice misfit.
Meanwhile, it may be envisioned to lower the nitrogen concentration so as to remove ESFs. In the context, Korean Patent Laid-open Publication No. 2005-0019845 suggests a nitrogen concentration between 1x1013 and 1x1014 atoms/cm3 to obtain a silicon wafer in which the density of void defects having an opening size of 20 nm or lower is 0.02 ea/cm2 or less.
However, simply decreasing the nitrogen concentration fails to ensure a sufficient density of BMDs, resulting in lower gettering effect, and consequently, deterioration in device performance. To overcome the problem, thermal treatment may be used to improve the density of BMDs, but, in this case, addition of a new process causes a rise in manufacturing costs and an increase in process control points.
The present invention is designed to solve the problems of the prior art, and therefore it is an object of the present invention to provide an EPI wafer with reduced occurrence of ESFs through control over the morphology of crystal defects in the bulk, and a silicon ingot for the same and a fabrication method thereof.
It is another object of the present invention to provide an EPI wafer with reduced occurrence of ESFs while sufficiently maintaining the density of BMDs that act as gettering sites, and a silicon ingot for the same and a fabrication method thereof.
To achieve the objects, the present invention discloses an EPI wafer, in which the bulk is doped with nitrogen for generating BMDs, and the morphology of crystal defects is controlled to reduce the occurrence of ESFs, and a silicon ingot for the same and a fabrication method thereof.
That is, an EPI wafer according to the present invention comprises a single crystal substrate and an EPI layer grown on the single crystal substrate, wherein the single crystal substrate is doped with nitrogen, and crystal defects in the single crystal substrate have an octahedral or overlapping kite-shaped morphology.
Preferably, the nitrogen concentration is between 1x1012 and 5x1013 atoms/cm3.
The single crystal substrate is co-doped with nitrogen and carbon. At this time, the nitrogen concentration is 2x1012 atoms/cm3 or higher, and the carbon concentration is 0.5 ppma or lower.
The single crystal substrate may use a P(-) or P(+) crystal.
In the EPI wafer, the density of ESFs observed on the surface of the EPI layer is preferably 0.007 ea/cm2 or less.
According to another aspect of the present invention, a silicon single crystal ingot for an EPI wafer grown by the Czochralski(Cz) method is provided, in which the single crystal is doped with nitrogen and crystal defects in the single crystal have an octahedral or overlapping kite-shaped morphology.
In the silicon single crystal ingot for an EPI wafer, the nitrogen concentration is preferably between 1x1012 and 5x1013 atoms/cm3.
The silicon single crystal may be co-doped with nitrogen and carbon. At this time, the nitrogen concentration is 2x1012 atoms/cm3 or higher, and the carbon concentration is 0.5 ppma or lower.
According to still another aspect of the present invention, provided is a method for fabricating a silicon single crystal ingot by the Czochralski method, which grows a silicon single crystal ingot at a solid-liquid interface by melting a polycrystalline silicon contained in a quartz crucible to produce a silicon melt, dipping a single crystal seed into the silicon melt and slowly pulling up the single crystal seed from the silicon melt while rotating the single crystal seed, the method comprising adding nitrogen to the silicon melt, and controlling the nitrogen concentration to obtain a single crystal with octahedral or overlapping kite-shaped morphology of crystal defects.
Preferably, the nitrogen concentration is set between 1x1012 and 5x1013 atoms/cm3.
In the step of adding nitrogen to the silicon melt, nitrogen and carbon co-doping may be carried out. At this time, the nitrogen concentration is preferably set to 2x1012 atoms/cm3 or higher, and the carbon concentration is preferably set to 0.5 ppma or lower.
According to the present invention, it can reduce the occurrence of ESFs through control over the morphology of COPs in the bulk of an EPI wafer when doping with nitrogen to generate BMDs that act as gettering sites for preventing contamination caused by metallic elements.
And, according to the present invention, it sufficiently maintains the density of BMDs as well as reduces the occurrence of ESFs when doping with nitrogen, thereby improving the gettering performance.
The accompanying drawings illustrate the preferred embodiments of the present invention and are included to provide a further understanding of the spirit of the present invention together with the detailed description of the invention, and accordingly, the present invention should not be limitedly interpreted to the matters shown in the drawings.
FIG. 1 is a cross-sectional view of a typical EPI wafer.
FIG. 2 is a schematic view showing EPI layer growth structures of an undoped wafer and a wafer doped with nitrogen in the bulk.
FIG. 3 is an SEM image showing the COP morphology without control and under control over the morphology of COPs in the bulk of an EPI wafer according to a preferred embodiment of the present invention.
FIG. 4 is a Magics image showing ESFs observed before and after controlling the morphology of COPs according to a preferred embodiment of the present invention.
FIG. 5 is an SEM image showing the COP morphology in the case of a low carbon concentration and a high carbon concentration in carbon co-doping according to a preferred embodiment of the present invention.
Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. Prior to the description, it should be understood that the terms used in the specification and the appended claims should not be construed as limited to general and dictionary meanings, but interpreted based on the meanings and concepts corresponding to technical aspects of the present invention on the basis of the principle that the inventor is allowed to define terms appropriately for the best explanation. Therefore, the description proposed herein is just a preferable example for the purpose of illustrations only, not intended to limit the scope of the invention, so it should be understood that other equivalents and modifications could be made thereto without departing from the spirit and scope of the invention.
An EPI wafer according to a preferred embodiment of the present invention comprises a single crystal substrate and an EPI layer grown on the single crystal substrate, wherein the single crystal substrate is doped with nitrogen, and crystal originated particles (COPs), i.e. crystal defects have an octahedral or overlapping kite-shaped morphology. Since the basic internal structure of the EPI wafer is the same as previously described in FIG. 1, its detailed description is omitted herein.
Nitrogen doped into the single crystal substrate generates BMDs in the bulk, and forms gettering sites for removal of metallic elements. In consideration of ESFs, the nitrogen concentration is determined such that COPs have an octahedral or overlapping kite-shaped morphology as shown in FIG. 3(b). For this purpose, the nitrogen concentration in the EPI wafer is preferably between 1x1012 and 5x1013 atoms/cm3. If the nitrogen concentration exceeds 5x1013 atoms/cm3, COPs have a nearly needle- or rod-shaped morphology as shown in FIG. 3(a), resulting in occurrence of a large number of ESFs. In the contrast, if the nitrogen concentration is lower than 1x1012 atoms/cm3, the BMD density is too low, resulting in insignificant gettering effect.
Specifically, in case that the nitrogen concentration is actually, for example, 2x1014 atoms/cm3, approximately 12 to 54 ea/wf of ESFs are observed on the surface of the EPI wafer relative to a 300 mm diameter wafer, as shown in FIG. 4(a). Meanwhile, in case that COPs have a controlled morphology of an octahedral or overlapping kite-shaped structure by maintaining the nitrogen concentration in the range between 1x1012 and 5x1013 atoms/cm3, 5 ea/wf (0.007 ea/cm2, when converted into density) or les of ESFs are observed as shown in FIG. 4(b), which means an improvement in ESF suppression about 10 times, compared with the conventional art.
Controlling the morphology of COPs to an octahedral or overlapping kite-shaped structure reduces the generation of COPs having an opening size between 10 and 90 nm, thereby remarkably reducing the occurrence of ESFs.
The reduced occurrence of ESFs with the change of nitrogen concentration as mentioned above is caused by the fact that the open COPs on the surface of a single crystal substrate have a larger opening size at a relatively lower nitrogen concentration than a relatively higher nitrogen concentration, and finally, the occurrence of lattice misfits is reduced. In case that the nitrogen concentration is lower than 1x1012 atoms/cm3, COPs have a completely octahedral morphology, but the BMD density is 1x108 ea/cm3 or less, which is not enough to obtain a sufficient gettering effect.
To ensure a sufficient density of BMDs in the EPI wafer, it is preferred to co-dope the single crystal substrate with nitrogen and carbon. It secures sufficient BMDs in P(-) or P(+) crystals while not modifying the COP morphology when co-doping with carbon. And, the use of carbon compensates for oxidation-induced stacking faults (OiSFs) that may occur at an edge area of a wafer due to nitrogen doping.
FIG. 5(a) shows the COP morphology in the case of a relatively lower carbon concentration, and FIG. 5(b) shows the COP morphology in the case of a relatively higher carbon concentration. It can be seen through FIG. 5 that the COP morphology is maintained as an octahedral or overlapping kite-shaped structure, even though the carbon concentration is changed from low to high level. This effect is apparent when the nitrogen concentration is 2x1012 atoms/cm3 or higher and the carbon concentration is 0.5 ppma or lower.
The EPI wafer of the above-mentioned configuration is fabricated in such a way that a silicon single crystal ingot is grown by the Czochralski method and cut into silicon single crystal wafers by a subsequent process such as slicing and so on, and an EPI layer is grown on the frontside of the silicon single crystal wafer.
In the process for growing the silicon single crystal ingot, a polycrystalline silicon raw material loaded in a quartz crucible is melt into a P-type silicon melt, and a single crystal seed is dipped in the silicon melt and then slowly pulled upwards and rotated at the same time, so that a single crystal is grown at a solid-liquid interface.
In the process for growing the silicon single crystal ingot according to a preferred embodiment of the present invention, nitrogen or nitrogen/carbon is added to the silicon melt in order to control the COP morphology of the single crystal to an octahedral or overlapping kite-shaped structure. At this time, the nitrogen concentration is preferably maintained in the range between 1x1012 and 5x1013 atoms/cm3, and in the case of co-doping with nitrogen and carbon, the nitrogen concentration is preferably maintained at 2x1012 atoms/cm2 or higher and the carbon concentration is maintained at 0.5 ppma or lower.
The silicon single crystal ingot fabricated by the above-mentioned process has a sufficient density of BMDs generated by nitrogen doping, which act as gettering sites for preventing contamination by metallic elements, and the COPs of an overlapping kite-shaped morphology, more preferably of an octahedral morphology, so that the density of ESFs can be maintained at 0.007 ea/cm2 or less.
Although the present invention has been described hereinabove, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.
According to the present invention, it can reduce ESFs occurring when doping with nitrogen to generate BMDs, by controlling the morphology of COPs in an EPI wafer, resulting in improvement of quality of devices employing the EPI wafer.

Claims (14)

  1. An epitaxial (EPI) wafer, comprising: a single crystal substrate and an EPI layer grown on the single crystal substrate,
    wherein the single crystal substrate is doped with nitrogen, and crystal defects existing in the single crystal substrate have an octahedral or overlapping kite-shaped morphology.
  2. The EPI wafer according to claim 1,
    wherein the nitrogen concentration is between 1x1012 and 5x1013 atoms/cm3.
  3. The EPI wafer according to claim 1,
    wherein the single crystal substrate is co-doped with nitrogen and carbon.
  4. The EPI wafer according to claim 3,
    wherein the nitrogen concentration is 2x1012 atoms/cm3 or higher and the carbon concentration is 0.5 ppma or lower.
  5. The EPI wafer according to claim 3,
    wherein the single crystal substrate is a P(-) or P(+) crystal.
  6. The EPI wafer according to any one of claims 1 through 5,
    wherein the density of ESFs observed on the surface of the EPI layer is 0.007 ea/cm2 or less.
  7. A silicon single crystal ingot for an EPI wafer, grown by the Czochralski method,
    wherein a single crystal is doped with nitrogen, and crystal defects existing in the single crystal have an octahedral or overlapping kite-shaped morphology.
  8. The silicon single crystal ingot for an EPI wafer according to claim 7,
    wherein the nitrogen concentration is between 1x1012 and 5x1013 atoms/cm3.
  9. The silicon single crystal ingot for an EPI wafer according to claim 7,
    wherein the single crystal is co-doped with nitrogen and carbon.
  10. The silicon single crystal ingot for an EPI wafer according to claim 9,
    wherein the nitrogen concentration is 2x1012 atoms/cm3 or higher and the carbon concentration is 0.5 ppma or lower.
  11. A method for fabricating a silicon single crystal ingot by the Czochralski method that grows a single crystal ingot at a solid-liquid interface by melting a polycrystalline silicon contained in a quartz crucible into a silicon melt, and dipping a single crystal seed into the silicon melt and slowly pulling up the single crystal seed from the silicon melt, the method comprising:
    adding nitrogen to the silicon melt; and
    controlling the nitrogen concentration to obtain a single crystal with octahedral or overlapping kite-shaped morphology of crystal defects.
  12. The method for fabricating a silicon single crystal ingot according to claim 11,
    wherein the nitrogen concentration is between 1x1012 and 5x1013 atoms/cm3.
  13. The method for fabricating a silicon single crystal ingot according to claim 11,
    wherein nitrogen and carbon co-doping is carried out.
  14. The method for fabricating a silicon single crystal ingot according to claim 13,
    wherein the nitrogen concentration is 2x1012 atoms/cm3 or higher and the carbon concentration is 0.5 ppma or lower.
PCT/KR2010/005306 2009-09-15 2010-08-12 Epi wafer and silicon single crystal ingot for the same and fabrication method thereof WO2011034284A2 (en)

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Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
KR20020019077A (en) * 2000-04-14 2002-03-09 와다 다다시 Silicon wafer, silicon epitaxial wafer, anneal wafer and method for producing them
JP2003100760A (en) * 2001-09-19 2003-04-04 Wacker Nsce Corp Epitaxial silicon wafer and method for manufacturing the same
KR20070047376A (en) * 2000-09-19 2007-05-04 엠이엠씨 일렉트로닉 머티리얼즈 인코포레이티드 Nitrogen-doped silicon substantially free of oxidation induced stacking faults

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
KR20020019077A (en) * 2000-04-14 2002-03-09 와다 다다시 Silicon wafer, silicon epitaxial wafer, anneal wafer and method for producing them
KR20070047376A (en) * 2000-09-19 2007-05-04 엠이엠씨 일렉트로닉 머티리얼즈 인코포레이티드 Nitrogen-doped silicon substantially free of oxidation induced stacking faults
JP2003100760A (en) * 2001-09-19 2003-04-04 Wacker Nsce Corp Epitaxial silicon wafer and method for manufacturing the same

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