Classifications

• • 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
  • H01L21/02612—Formation types
  • H01L21/02617—Deposition types
  • H01L21/02636—Selective deposition, e.g. simultaneous growth of mono- and non-monocrystalline semiconductor materials
• • 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
  • H01L21/22—Diffusion of impurity materials, e.g. doping materials, electrode materials, into or out of a semiconductor body, or between semiconductor regions; Interactions between two or more impurities; Redistribution of impurities
  • H01L21/2205—Diffusion of impurity materials, e.g. doping materials, electrode materials, into or out of a semiconductor body, or between semiconductor regions; Interactions between two or more impurities; Redistribution of impurities from the substrate during epitaxy, e.g. autodoping; Preventing or using autodoping
• • 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
  • H01L21/0237—Materials
  • H01L21/02373—Group 14 semiconducting materials
  • H01L21/02381—Silicon, silicon germanium, germanium
• • 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
  • H01L21/02518—Deposited layers
  • H01L21/02521—Materials
  • H01L21/02524—Group 14 semiconducting materials
  • H01L21/02532—Silicon, silicon germanium, germanium
• • 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
  • H01L21/02518—Deposited layers
  • H01L21/0257—Doping during depositing
  • H01L21/02584—Delta-doping
• • 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
  • H01L21/02694—Controlling the interface between substrate and epitaxial layer, e.g. by ion implantation followed by annealing
• • H—ELECTRICITY
  • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
  • H10D—INORGANIC ELECTRIC SEMICONDUCTOR DEVICES
  • H10D30/00—Field-effect transistors [FET]
  • H10D30/60—Insulated-gate field-effect transistors [IGFET]
  • H10D30/64—Double-diffused metal-oxide semiconductor [DMOS] FETs
  • H10D30/66—Vertical DMOS [VDMOS] FETs
  • H10D30/668—Vertical DMOS [VDMOS] FETs having trench gate electrodes, e.g. UMOS transistors
• • H—ELECTRICITY
  • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
  • H10D—INORGANIC ELECTRIC SEMICONDUCTOR DEVICES
  • H10D62/00—Semiconductor bodies, or regions thereof, of devices having potential barriers
  • H10D62/60—Impurity distributions or concentrations
  • H10D62/605—Planar doped, e.g. atomic-plane doped or delta-doped
• • H—ELECTRICITY
  • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
  • H10D—INORGANIC ELECTRIC SEMICONDUCTOR DEVICES
  • H10D62/00—Semiconductor bodies, or regions thereof, of devices having potential barriers
  • H10D62/80—Semiconductor bodies, or regions thereof, of devices having potential barriers characterised by the materials
  • H10D62/83—Semiconductor bodies, or regions thereof, of devices having potential barriers characterised by the materials being Group IV materials, e.g. B-doped Si or undoped Ge

Definitions

• Embodiments of the present invention relate to the fields of design and manufacture of semiconductors, and more particularly to systems and methods for substrate wafer back side and edge cross section seals.
• Epitaxy is a process by which a single crystal, for example Silicon, is grown on or deposited on a single crystal substrate.
• exemplary processes include chemical vapor deposition (CVD), wherein gas phase Silicon sources, such as silicon tetrachloride (SiCl 4 ), trichlorosilane (S1HCI3), dichlorosilane (S1H2CI2) and/or silane (S1H4) in a hydrogen carrier gas, are passed over a silicon substrate at a high temperature, e.g., about 700° C to 1200° C, resulting in an epitaxial growth process. It is appreciated that epitaxial processes may grow non-Silicon materials as well.
• Epitaxy is commonly used in the fabrication of power semiconductor devices, such as those used in computer power supplies, pacemakers, vending machine controllers, automobile computers, and the like.
• Figure 1A illustrates one well known deleterious side effect of epitaxial growth, known as "auto-doping.”
• Auto doping is a process by which dopants originating from the substrate 110 migrate into the epitaxial layer 120, deleteriously changing the doping profile of the epitaxial layers. It is appreciated that dopant migration may take a variety of paths from a substrate to an epitaxial layer, including, for example, liberation into the process gas(ses). In general, auto doping may lead to numerous adverse effects, including, for example, reduced breakdown voltage of the epitaxial layer. Additionally, the auto doping process is generally neither controlled nor predictable. Thus, auto doping leads to numerous detrimental effects.
• a wafer may have an optional oxide seal 125 on the back side.
• Oxide seal 125 is generally intended to reduce auto-doping. However, oxide seal 125 may corrode and be subject to "pin-hole" defects during multiple cleaning processes between multiple epitaxial layer growth processes. When oxide seal 125 is subject to such corrosion, the oxide seal 125 fails to prevent auto doping.
• this writing discloses a system and method for substrate wafer back side and edge cross section seals.
• Systems and methods for substrate wafer back side and edge cross section seals are desired.
• systems and methods of forming multiple epitaxial layers without the accumulation of deleterious side effects is desired.
• systems and methods of forming multiple epitaxial layers with vertical trenches and/or vertical doped columns are desired.
• systems and methods for substrate wafer back side and edge cross section seals that are compatible and complementary with conventional wafer processing systems are desired.
• Embodiments in accordance with the present invention provide for these needs.
• a silicon wafer of a first conductivity type is accessed.
• An epitaxial layer of the first conductivity type is grown on a front surface of the silicon wafer.
• the epitaxial layer is implanted to form a region of an opposite conductivity type.
• the growing and implanting are repeated to form a vertical column of the opposite conductivity type.
• the wafer may also be implanted to form a region of the opposite conductivity type vertically aligned with the vertical column.
• a layer of silicon oxide is deposited on all surfaces and edges of the silicon wafer.
• the silicon oxide is removed from a front surface of the silicon wafer.
• a layer of poly silicon is deposited on a back surface of the silicon wafer, over the silicon oxide.
• a layer of epitaxial silicon is grown on the front side of the silicon wafer. Auto doping of the layer of epitaxial silicon may be reduced relative to auto doping occurring during epitaxial silicon growth on a wafer without the layer of silicon oxide.
• a semiconductor device includes a silicon substrate including bulk silicon, and a plurality of stacked epitaxial silicon layers disposed on a front side of the substrate.
• Each of the plurality of epitaxial silicon layers includes a doped region forming in aggregate a vertical doped column in the semiconductor device.
• Figure 1A (conventional art) illustrates one well known
• Figure IB illustrates an irregular silicon "bump" or nodule that has formed the back or opposite side of a wafer due to exposure to process gasses.
• Figures 2A, 2B and 2C illustrate a process of sealing a wafer substrate to prevent auto doping and/or back side nodule growth, in accordance with embodiments of the present invention.
• Figure 3A illustrates epitaxial growth on a sealed wafer, in accordance with embodiments of the present invention.
• Figure 3B illustrates non-uniform, e.g., selective, epitaxial growth of an epitaxial layer on the front/top surface of an epitaxial layer, in accordance with embodiments of the present invention.
• Figure 3C illustrates repetitive doping of a plurality of epitaxial layers, in accordance with embodiments of the present invention.
• Figure 4 illustrates a final semiconductor wafer substrate after further processing, in accordance with embodiments of the present invention.
• Figures 2A - 2C illustrate a process of sealing a wafer substrate to prevent auto doping and/or back side nodule growth, in accordance with embodiments of the present invention.
• a silicon substrate 210 is uniformly coated with Silicon oxide 220 to a thickness of about 800 to 1200 angstroms, e.g., about 1000 angstroms.
• Item 210 may also comprise an oxide seal, e.g., oxide seal 125 of Figure 1A, on its back side, in an embodiment.
• Silicon oxide 220 is deposited on the front, back and edges of wafer 210.
• the top portion of Silicon oxide coating 220 e.g., that portion of Silicon oxide 220 above the top or front of wafer 210, is removed, e.g., by polishing. It is appreciated that a small amount of the top side of wafer 210 may be removed as well.
• a layer 230 of poly Silicon is deposited on the back side of wafer 210 over the Silicon oxide 220.
• the Silicon oxide 220 is against wafer 210
• the poly silicon 230 is against the Silicon oxide 220.
• the poly Silicon 230 has a thickness of about 8000 to 9000 angstroms, e.g., about 8500 angstroms.
• the poly Silicon 230 is deposited in such a manner that it is only deposited on the back side of the wafer, in an embodiment.
• One suitable process is deposition via chemical vapor deposition on a silicon carbide susceptor in a sealed wafer environment.
• Silicon oxide coating 220 prevents auto doping during epitaxial growth. For example, Silicon oxide coating 220 prevents migration of dopants from wafer
• the poly Silicon 230 prevents the growth of non-uniform nodules on the back side of wafer 210.
• the poly Silicon 230 provides uniform nucleation for epitaxial Silicon growth.
• epitaxial material may still grow on the back side of wafer 210, such growth is substantially uniform, e.g., it forms a smooth layer, in contrast to the deleterious non-uniform nodules that may form directly on the back side of an uncoated wafer, as shown in Figure IB, as may occur under the conventional art.
• Figure 3A illustrates epitaxial growth on a sealed wafer, in accordance with embodiments of the present invention.
• Wafer 210 is coated on the bottom and edges with Silicon oxide 220.
• the bottom of wafer 210 is coated with poly Silicon 230, deposited over a portion of Silicon oxide 220.
• Epitaxial layer 310 has been grown on the front/top surface of wafer 210.
• epitaxial layer 320 has been grown on the top surface of epitaxial layer 310. It is appreciated that epitaxial layer 320 may have a different thickness and/or doping composition from that of epitaxial layer 310. Due to the sealing effects of Silicon oxide 220, no deleterious auto doping has occurred during the epitaxial growth process(es), and the epitaxial layer(s) 310, 320, beneficially have the desired doping characteristics.
• Figure 3A further illustrates a substantially uniform layer of epitaxy 330 on the bottom side of wafer 210.
• Layer 330 is formed during the growth of layers 310 and/or 320. Layer 330 does not subject the wafer 210 to the deleterious handling effects of non-uniform silicon nodules, e.g., as shown by nodule 130 of Figure IB.
• the epitaxial growth on the front/top surface of wafer 210 need not be uniform.
• Figure 3B illustrates non-uniform, e.g., selective, epitaxial growth of epitaxial layer 321 on the front/top surface of epitaxial layer 310, in accordance with embodiments of the present invention.
• the lack of epitaxial growth in a region has formed a trench 325.
• the formation of layer 321 is well suited to a variety of well known processes for selective epitaxial growth.
• a region on an underlying area, e.g., epitaxial layer 310 or substrate 210, in the region of trench 325 may be masked by a dielectric film, e.g., silicon dioxide or silicon nitride, prior to epitaxial growth.
• a plurality of epitaxial layers may be growth, either uniformly, as illustrated by layers 310 and 320, or non-uniformly, as illustrated by layers 321 and 322.
• features such as trench 325 may be constructed by a lack of formation of material, in contrast to processes that form such features via the removal of material. It is appreciated that the dopant concentration of each epitaxial layer may be different, so as to form a desirable doping profile. It is to be further
• trench 325 may terminate at a substrate, e.g., substrate 220, or within one of a plurality of epitaxial layers, e.g., 310, 321, 322, and the like.
• embodiments in accordance with the present invention may be combined with other methods of trench formation, e.g., methods that remove material, to form trenches that terminate within a substrate, e.g., within substrate 220.
• Figure 3C illustrates repetitive doping of a plurality of epitaxial layers, in accordance with embodiments of the present invention.
• epitaxial layer 341 is grown, in a similar manner as illustrated by layer 320 ( Figure 3A).
• a portion of layer 341, e.g., in region 345 is doped by well known processes.
• epitaxial layer 342 is grown over layer 341, and a portion of layer 342, e.g., in region 345, is doped by well known processes.
• epitaxial layers 310, 341, 342 may be n-type epitaxial layers. Regions 345 may be doped with p-type dopants.
• a vertical column or well of a dopant type e.g., p-type, may be created. Since each layer is individually grown and doped, the layer thickness, depth of doping, doping concentration, doping species and the like may differ with each layer growth and doping processes.
• such a column or well may have characteristics, e.g., depth and/or doping levels and/or doping profiles, that are difficult or impossible to obtain via other doping methods, e.g., conventional well implantation from above a surface.
• Figure 4 illustrates a final semiconductor wafer substrate after further processing, in accordance with embodiments of the present invention.
• the depositions on the back side of wafer 210 e.g., epitaxy 330, poly Silicon 230 and the back side portion of Silicon oxide 220, may be removed, e.g., via grinding or back-lapping or other well known processes, such that wafer 210 has a desired thickness.
• the side/edge portions of Silicon oxide 220 may also be removed.
• the edges of a wafer are generally not used for a final semiconductor device, and thus removal of such edge portions of Silicon oxide 220 may not be required.
• Figure 4 further illustrates optional vertical trench 325, formed by gaps in a plurality of epitaxial layers, e.g., epitaxial layers 360, 370.
• Figure 4 illustrates an optional doped column 345, formed by repeating a cycle of growing a layer of epitaxial material and then doping such layer.
• Embodiments in accordance with the present invention are well suited to the formation of semiconductor devices utilizing multiple epitaxial layers.
• a trench as utilized by well known trench
• MOSFET trench metal oxide semiconductor field effect transistor
• Non-Silicon epitaxial layers may include, for example, Gallium nitride (GaN), Silicon Carbide (SiC), sapphire, Germanium (Ge), Gallium arsenide (GaAs), Indium antimonide (InSb), Lead sulfide (PbS), Lead selenide
• one or more buffer layers are generally first grown on top of a Silicon substrate, forming a buffer between the Silicon substrate and the non-Silicon epitaxial layer(s).
• Such buffer layers are generally intended to mitigate problems between silicon substrates and non-Silicon epitaxial layers such as seeding, lattice mismatching, stress relief, cracking free, etc.
• Exemplary buffer layers may comprise Aluminum nitride (A1N), Patterned Sapphire (PS), Hafnium nitride (HfN), Barium fluoride (BaF2), and the like.
• Embodiments in accordance with the present invention may form a seal to reduce and/or prevent such outgasing from the back and edges of a substrate during buffer layer growth.
• high quality buffer layer(s) may be obtained, advantageously enabling high quality non-Silicon epitaxial layers to be grown on silicon substrates.
• embodiments of the present invention provide systems and methods for substrate wafer back side and edge cross section seals.
• systems and methods of forming multiple epitaxial layers without the accumulation of deleterious side effects are provided.
• systems and methods of forming multiple epitaxial layers with vertical trenches and/or vertical doped columns are provided. Still further,
• a method of forming a semiconductor comprising: accessing a silicon wafer of a first conductivity type;
• a method of growing epitaxial silicon on a silicon wafer comprising:
• a semiconductor device comprising:
• a silicon substrate comprising bulk silicon
• each of said plurality of epitaxial silicon layers comprises a doped region forming in aggregate a vertical doped column in said
• Concept 17 The semiconductor device of Concept 16 comprising at least six stacked epitaxial layers.
• a silicon wafer comprising:
• a method comprising:

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• 2010
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