EP3485505A1 - Procédé d'un substrat donneur soumis à une récupération - Google Patents

Procédé d'un substrat donneur soumis à une récupération

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Publication number
EP3485505A1
EP3485505A1 EP17755560.4A EP17755560A EP3485505A1 EP 3485505 A1 EP3485505 A1 EP 3485505A1 EP 17755560 A EP17755560 A EP 17755560A EP 3485505 A1 EP3485505 A1 EP 3485505A1
Authority
EP
European Patent Office
Prior art keywords
substrate
donor substrate
donor
gan
face
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP17755560.4A
Other languages
German (de)
English (en)
Inventor
Francois J. Henley
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Qmat Inc
Original Assignee
Qmat Inc
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Priority claimed from US15/643,370 external-priority patent/US20180019169A1/en
Priority claimed from US15/643,384 external-priority patent/US20180033609A1/en
Application filed by Qmat Inc filed Critical Qmat Inc
Priority claimed from PCT/IB2017/054209 external-priority patent/WO2018011731A1/fr
Publication of EP3485505A1 publication Critical patent/EP3485505A1/fr
Withdrawn legal-status Critical Current

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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
    • H01L21/02002—Preparing wafers
    • H01L21/02005—Preparing bulk and homogeneous wafers
    • H01L21/02032—Preparing bulk and homogeneous wafers by reclaiming or re-processing
    • 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
    • H01L21/70—Manufacture or treatment of devices consisting of a plurality of solid state components formed in or on a common substrate or of parts thereof; Manufacture of integrated circuit devices or of parts thereof
    • H01L21/71—Manufacture of specific parts of devices defined in group H01L21/70
    • H01L21/76—Making of isolation regions between components
    • H01L21/762—Dielectric regions, e.g. EPIC dielectric isolation, LOCOS; Trench refilling techniques, SOI technology, use of channel stoppers
    • H01L21/7624—Dielectric regions, e.g. EPIC dielectric isolation, LOCOS; Trench refilling techniques, SOI technology, use of channel stoppers using semiconductor on insulator [SOI] technology
    • H01L21/76251—Dielectric regions, e.g. EPIC dielectric isolation, LOCOS; Trench refilling techniques, SOI technology, use of channel stoppers using semiconductor on insulator [SOI] technology using bonding techniques
    • H01L21/76254—Dielectric regions, e.g. EPIC dielectric isolation, LOCOS; Trench refilling techniques, SOI technology, use of channel stoppers using semiconductor on insulator [SOI] technology using bonding techniques with separation/delamination along an ion implanted layer, e.g. Smart-cut, Unibond
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L33/00—Semiconductor devices having potential barriers specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
    • H01L33/005—Processes
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L33/00—Semiconductor devices having potential barriers specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
    • H01L33/005—Processes
    • H01L33/0093—Wafer bonding; Removal of the growth substrate
    • 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
    • H01L21/02538—Group 13/15 materials
    • H01L21/0254—Nitrides
    • 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
    • H01L21/02538—Group 13/15 materials
    • H01L21/02546—Arsenides
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L33/00—Semiconductor devices having potential barriers specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
    • H01L33/005—Processes
    • H01L33/0062—Processes for devices with an active region comprising only III-V compounds

Definitions

  • Conventional techniques for manufacturing electronic devices may involve the formation and manipulation of thin layers of materials.
  • One example of such manipulation is the transfer of a thin layer of material from a first (donor) substrate to a second (target) substrate. This may be accomplished by placing a face of the donor substrate against a face of the target substrate, and then cleaving the thin layer of material along a sub-surface cleave plane formed in the donor substrate.
  • the donor substrate may comprise valuable, high quality crystalline material that is expensive to produce. Thus, following such a layer transfer process, the donor substrate may be sought to be reclaimed for subsequent use in further layer transfer efforts. Accordingly, there is a need in the art for methods and apparatuses of processing a donor substrate to allow for its reclamation for subsequent layer transfer.
  • a donor substrate in a layer transfer process may be stabilized by attaching a backing substrate.
  • the backing substrate allows thermal and mechanical stabilization during high-power implant processes.
  • the backing substrate Upon cleaving the donor substrate to release a thin layer of material to a target, the backing substrate prevents uncontrolled release of internal stress leading to buckling/fracture of the donor substrate.
  • the internal stress may accumulate in the donor substrate due to processes such as cleave region formation, bonding to the target, and/or the cleaving process itself, with uncontrolled bow and warp potentially precluding reclamation/reuse of the donor substrate in subsequent layer transfer processes.
  • the backing substrate may exhibit a Coefficient of Thermal Expansion (CTE) substantially matching, or complementary to, that of the donor substrate.
  • the backing structure may include a feature such as a lip.
  • Embodiments relate to reclaiming a donor substrate that has previously supplied a thin film of material in a layer transfer process. Certain embodiments selectively perform annular grinding upon edge regions only of the donor substrate. This serves to remove residual material at the edge regions, with grind damage not impacting subsequent transfer of material from central regions of the donor substrate. Some embodiments accomplish reclamation by applying energy to the donor substrate after cleaving has occurred. The energy is calculated to interact with a cleave region (e.g., resulting from ion implantation) underlying the residual material, thereby allowing separation of that residual material at the cleave region.
  • a cleave region e.g., resulting from ion implantation
  • This reclamation approach can remove residual material in donor substrate central regions (e.g., resulting from a void), without requiring invasive grinding and post-grinding processing to remove grind damage.
  • Embodiments may apply energy in the form of a laser beam absorbed at the cleave region.
  • Figure 1 shows a simplified view of a fabrication process involving the reclamation of a GaN substrate.
  • Figure 1 A is a simplified view showing the Ga face and N face of a GaN substrate.
  • Figures 2A-2G show simplified views a GaN substrate undergoing reclamation according to one embodiment.
  • Figures 3A-3G show simplified views of a GaN substrate undergoing reclamation according to another embodiment.
  • Figure 4 illustrates a simplified flow diagram of a reclamation process according to an embodiment.
  • Figures 5A-5F show simplified cross-sectional views of a process flow according to an embodiment.
  • Figure 6 shows a simplified cross-sectional view of a possible donor substrate/backing substrate combination.
  • Figure 7 shows a simplified view of a fabrication process involving the reclamation of a GaN substrate.
  • Figure 8 illustrates a simplified flow diagram of a reclamation process according to an embodiment.
  • Figure 9 plots thermal conductivity versus gap.
  • HB-LED high-brightness light emitting diode
  • An optoelectronic device such as a HB-LED may rely upon materials exhibiting semiconductor properties, including but not limited to type III/V materials such as gallium nitride (GaN) or Aluminum Nitride (A1N) that is available in various degrees of crystalline order. However, these materials are often difficult to manufacture.
  • type III/V materials such as gallium nitride (GaN) or Aluminum Nitride (A1N) that is available in various degrees of crystalline order.
  • GaN gallium nitride
  • A1N Aluminum Nitride
  • FIG. 1 shows a simplified view of one fabrication process 100 to form a permanent substrate offering a template for the subsequent growth of high quality GaN for optoelectronic applications.
  • a donor substrate 102 comprises high-quality GaN material.
  • a cleave region 104 is located at a sub-surface region of the donor substrate. This cleave region may be formed, for example, by the energetic implantation 105 of particles such as hydrogen ions, into one face of the GaN donor substrate.
  • FIG. 1A is a simplified view illustrating the internal structure of a GaN substrate, showing the Ga face and the N face.
  • the implanted Ga face of the GaN substrate is bonded to a releasable substrate 106 bearing a release layer 108.
  • the material of the releasable substrate may be selected such that its Coefficient of Thermal Expansion (CTE) substantially matches that of the GaN.
  • the material of the releasable substrate may also be selected to be transparent to incident laser light as part of a Laser Lift Off (LLO) process.
  • LLO Laser Lift Off
  • a releasable substrate comprising glass may be used.
  • the release layer may comprise a variety of materials capable of later separation under controlled conditions.
  • candidate releasable materials can include those undergoing conversion from the solid phase to the liquid phase upon exposure to thermal energy within a selected range. Examples can include soldering systems, and systems for Thermal Lift Off (TLO).
  • the release system may comprise silicon oxide.
  • this bond-and-release system can be formed by exposing the workpieces to oxidizing conditions.
  • this bond-and-release system may be formed by the addition of oxide, e.g., as spin-on-glass (SOG), or other spin on material (e.g., XR-1541 hydrogen silsesquioxane electron beam spin-on resist available from Dow Corning), and/or Si02 formed by Plasma Enhanced Chemical Vapor Deposition (PECVD) techniques.
  • SOG spin-on-glass
  • PECVD Plasma Enhanced Chemical Vapor Deposition
  • Figure 1 shows a number of subsequent steps that are performed in order to create the template for high-quality GaN growth. These steps include surface preparation 114 of the separated GaN layer (e.g., the formation of an oxide), bonding 116 the separated GaN layer to a permanent substrate 118, and finally the removal of the releasable substrate utilizing the release layer (e.g., utilizing a LLO process 120), to result in the N face of the separated GaN layer being bonded to the permanent substrate.
  • steps include surface preparation 114 of the separated GaN layer (e.g., the formation of an oxide), bonding 116 the separated GaN layer to a permanent substrate 118, and finally the removal of the releasable substrate utilizing the release layer (e.g., utilizing a LLO process 120), to result in the N face of the separated GaN layer being bonded to the permanent substrate.
  • Ga face is exposed and available for growth of additional high quality GaN material under desired conditions.
  • Additional GaN may be formed by Metallo-Organic Chemical Vapor Deposition (MO-CVD), for example. That additional thickness of GaN material (with or without the accompanying substrate and/or dielectric material) may ultimately be incorporated into a larger optoelectronic device structure (such as a HB-LED).
  • MO-CVD Metallo-Organic Chemical Vapor Deposition
  • separation of the GaN film results in the valuable GaN donor substrate being available for re-use in order to create additional template structures for high quality GaN growth. This can be accomplished by performing additional implantation, and then bonding to a releasable substrate.
  • the GaN donor substrate may need to first be reclaimed so that it is suitable for the intended processing.
  • the Ga face of the donor substrate may exhibit properties such as surface roughness, defects, and/or non- planarity resulting from the previous cleaving step, that render it unsuitable for immediate implantation and bonding.
  • a donor substrate reclamation procedure is shown generally as step 130 in Figure 1.
  • Various embodiments of reclamation approaches are now described in connection with Figures 2A-2G and Figures 3 A-3G.
  • figures 2A-2G show simplified views a GaN substrate undergoing a reclamation procedure 200 according to one embodiment.
  • Figures 2A-2D summarize the first three steps of Figure 1.
  • Figure 2A shows the GaN donor substrate 102, including the cleave region 104 formed, e.g., by ion implantation.
  • Forming a cleave region may depend upon factors such as the target material, the crystal orientation of the target material, the nature of the implanted particle(s), the dose, energy, and temperature of implantation, and the direction of implantation.
  • Such implantation may share one or more characteristics described in detail in connection with the following patent applications, all of which are incorporated by reference in their entireties herein: U.S. Patent Application No. 12/789,361; U.S. Patent Application No. 12/730,113; U.S. Patent Application No. 11/935,197; U.S. Patent Application No.
  • Figure 2B shows the next step, wherein the releasable substrate is bonded to the Ga face of the GaN donor.
  • the releasable layer is omitted for clarity.
  • Figure 2B shows that the bound surfaces between the donor substrate and the releasable substrate are not exactly co-extensive. That is, an edge portion 102c (e.g., typically of about 1 mm in width) is not bound to the overlying releasable substrate, owing to a bevel in the side of that releasable substrate.
  • the size of the bevel is substantially exaggerated in Figure 2B for purposes of illustration.
  • the removed releasable substrate carries away with it, the detached thin GaN layer 112 from all but the edge portion of the donor with which the releasable substrate is not in contact. This leaves residual GaN material 230 present at edge portions of the donor substrate.
  • Figure 2D shows a perspective view of this configuration.
  • the residual GaN material remains at a height corresponding to the depth of the original cleave region. This creates substantial non-planarity in the donor GaN substrate. Because implant penetration depth is dependent upon the thickness of material, this non- planarity renders the GaN donor substrate unsuited for immediate implant and reuse.
  • Ga face of the GaN donor substrate that exhibits non-planarity.
  • This Ga face exhibits substantial hardness (e.g., -430 GPa), rendering it unsuited for removal except under relatively exacting conditions such as grinding.
  • Figure 2E shows annular grinding 232 directed to the edge portions only, leaving unaffected the central portion 234 resulting from prior removal of the cleaved GaN.
  • This focused, limited grinding may be facilitated by prior image processing (e.g., performed in Fig. 2D) identifying the precise extent and/or nature (e.g., thickness, roughness) of the edge portions.
  • Figure 2F shows the result of the localized annular grinding.
  • the raised GaN material at edge portions is removed.
  • the resulting edge surfaces may exhibit surface roughness 236 and/or defects 238 extending to a depth into the substrate, that result from the harsh conditions of the annular grinding.
  • the ongoing presence of surface roughness/defects confined to edge portions of the donor substrate is acceptable.
  • the subsequent donor reuse 240 involving ion implantation, bonding, and cleaving processes implicates only the central portion of the GaN donor, rather than the edge portions.
  • the edge portion (which now may contain subsurface defects which lower crystal quality and device performance) is limited to non-processed areas of the subsequent transfers. This is an acceptable compromise which help lower complexity and cost of the reclaim process.
  • gap(s) or void(s) 302 may be present in center portions of the GaN donor substrate 304. These gap(s) or void(s) may affect the nature of the cleaving that occurs in the cleave region.
  • Figure 3B shows the bonding of a releasable substrate 306 to the GaN donor including the void.
  • Figure 3C shows the resulting cleaving process. As with the embodiment of Figure 2C, this cleaving results in non-transferred material 308 remaining at the edge portion of the GaN donor. [0044] Moreover, this second embodiment shows that the existence of the void in the central portion also results in residual, non -transferred material 310 remaining in the central portion of the GaN donor following the cleaving.
  • Figures 3D-3G illustrate an alternative donor substrate reclamation procedure. Specifically, an optional image processing step 310 in Figure 3D, initially reveals the precise location of residual GaN, both at the edge and in central regions of the donor substrate.
  • the applied energy in this embodiment is laser energy tuned to be preferentially absorbed at the implant peak.
  • Examples of such applied energy are a 532nm doubled or 355nm tripled YAG Q-switched laser or a heat lamp.
  • This H-implant absorption effect is described in "Structures and optical properties of -implanted GaN epi-layers" by Li & al. Absorption coefficients exceeding 30,000 cm "1 occurs at proton doses of 5-8x10 16 cm "2 using a 532 nm laser.
  • This strong absorption contrast allows the laser to selectively remove non-cleaved or partially cleaved films at or near the desired cleave plane.
  • Tuning of the beam e.g., repetition rate, fluence, and pulse-pulse overlap
  • this applied energy may be the same as, or different from, the energy previously used to accomplish cleaving to release the thin layer of GaN material along the cleave region (e.g., as shown in Figure 3C).
  • the particular embodiment shown in Figure 3E indicates the specific application of energy only to (central, edge) locations of the remaining GaN material. Such precise, targeted application of energy may be afforded by an (optional) upstream image processing step.
  • alternative embodiments may instead apply the energy 320 in a global (rather than local) manner.
  • energy could be applied globally to the surface of the GaN donor substrate (e.g., by scanned laser or heat lamp), in order to remove the residual GaN material.
  • the energy of Figure 3E is calculated to interact with the cleave region underlying the residual GaN, causing separation from the GaN donor substrate.
  • optical energy in the form of a laser beam is absorbed at the cleave region and converted to thermal form, resulting in the separation of GaN material at that depth.
  • An energy beam applied from a laser such as a 532nm (doubled- YAG) or 355nm (tripled- YAG) laser may be suited for this purpose.
  • Figure 3F The resulting separation of the residual GaN portions is depicted in Figure 3F.
  • Figure 3F also shows the impact on the center and edge regions of the GaN donor substrate, of the separation of residual GaN material by the application of energy.
  • GaN donor substrate surface locations corresponding to the formerly residual GaN material may exhibit roughness 322 or other features.
  • these surface roughness/features 322 do not extend deeply into the GaN donor substrate. Rather, as shown in Figure 3G they would be expected to impact only about a fraction of a micron of the donor substrate surface. Thus, they may be removed by the application of conditions significantly less severe than those encountered during grinding processes. Examples of such fine processing 324 can include but are not limited to, fine chemical-mechanical polishing, plasma exposure, and/or wet chemical exposure.
  • FIG. 4 is a simplified flow diagram illustrating a process 400 of substrate reclamation according to an embodiment.
  • a substrate comprising a cleave region and residual material is provided.
  • step 404 image processing of the surface of the substrate is performed.
  • a third step 406 energy is applied to the substrate in order to separate the residual material from the substrate at the cleave region.
  • a fourth step 408 the substrate is exposed to one or more fine processing techniques.
  • the substrate reclamation embodiments described in Figures 2A-2G and 3A-3G are not mutually exclusive. That is, it is possible to use annular edge grinding techniques to remove residual GaN material at edge regions, and then remove residual GaN material in central regions utilizing the application of energy. Alternatively, these steps may be performed in the reverse order. In such embodiments, image processing taking place between grinding/energy application steps could afford insight into the precise nature (e.g., height, roughness, dimensions) of the remaining GaN material and the conditions for its removal.
  • a donor substrate comprising GaN material
  • this is not required.
  • Alternative embodiments could feature donor substrates comprising other Group III/V materials, including but not limited to GaAs.
  • a donor such as GaAs may further include a backing substrate such as sapphire.
  • non-transferred materials can include but are not limited to high hardness materials such as silicon, silicon carbide, aluminum nitride, sapphire, as well as other materials whose hardness conventionally requires harsh grinding techniques for removal, followed by prolonged polishing to remove damage inflicted by grinding.
  • implantation followed by energy application could serve as a substitute for conventional harsh grinding techniques to prepare a high-hardness surface.
  • Such an approach could improve throughput by avoiding not only the grinding step itself, but also extensive/prolonged post-grinding processing to remove grind damage.
  • some applications may call for growth of GaN material from the N face, rather than from the Ga face.
  • Some applications e.g., power electronics
  • Incorporated by reference herein for all purposes are the following articles: Xun Li et al., "Properties of GaN layers grown on N-face free-standing GaN substrates", Journal of Crystal Growth 413, 81-85 (2015); A.R.A. Zauner et al, "Homo-epitaxial growth on the N-face of GaN single crystals: the influence of the misorientation on the surface morphology", Journal of Crystal Growth 240, 14-21 (2002).
  • template blank structures of some embodiments could feature a GaN layer having an N face that is exposed, rather than a Ga face.
  • an N face donor assembly could be used to fabricate a Ga face final substrate when bonded to a final substrate instead of a releasable transfer substrate as in Figure 1.
  • a method comprising:
  • a donor substrate comprising a cleave region between residual material and remaining portions of the donor substrate by a cleave region
  • the residual material is also located in an edge portion of the donor substrate.
  • the method further comprises performing annular grinding at the edge portion .
  • 16a A method as in clause la wherein:
  • the donor substrate comprises GaN
  • the energy is applied to a Ga face of the donor substrate.
  • the donor substrate comprises GaN
  • the energy is applied to a N face of the donor substrate.
  • Conventional techniques for manufacturing electronic devices may involve the formation and manipulation of thin layers of materials.
  • One example of such manipulation is the transfer of a thin layer of material from a first (donor) substrate to a second (target) substrate. This may be accomplished by placing a face of the donor substrate against a face of the target substrate, and then cleaving the thin layer of material along a sub-surface cleave plane formed in the donor substrate.
  • the donor substrate may comprise valuable, high quality crystalline material that is expensive to produce and may contain devices already processed onto a face. Thus, following such a layer transfer process, the donor substrate may be sought to be reclaimed for subsequent use in further layer transfer efforts. Accordingly, there is a need in the art for methods and apparatuses of processing a donor substrate to allow for its reclamation for subsequent layer transfer. There is also a need to mechanically and thermally stabilize a donor substrate to allow it to be subjected to high-power implant processes.
  • a donor substrate in a layer transfer process is stabilized by attaching a backing substrate.
  • the assembly (donor and backing substrate) has enhanced mechanical stability and thermal heat spreading capabilities to allow for optimized backside heat extraction through convection or conduction mechanisms.
  • the backing substrate Upon cleaving the donor substrate to release a thin layer of material to a target, the backing substrate prevents uncontrolled release of internal stress leading to buckling/fracture of the donor substrate.
  • the internal stress may accumulate in the donor substrate due to processes such as cleave region formation, bonding to the target, and/or the cleaving process itself, with uncontrolled buckling/fracture potentially precluding reclamation/reuse of the donor substrate in subsequent layer transfer processes.
  • the backing substrate may exhibit a Coefficient of Thermal Expansion (CTE) substantially matching, or complementary to, that of the donor substrate.
  • CTE Coefficient of Thermal Expansion
  • the backing structure may include a feature such as a lip, constraining lateral expansion of the donor substrate (e.g., in response to the application of thermal energy) and allowing mechanical fixturing of the assembly onto equipment such as a polishing or implant tool.
  • the process of transferring thin layers of material from a donor substrate to a target may involve the formation of stress in the donor.
  • certain embodiments may employ bonding the donor substrate to a target, followed by controlled cleaving along a cleave region formed at a depth in the donor substrate.
  • Such a cleave region may result from the implantation of particles (e.g., hydrogen ions) into a face of the donor substrate.
  • the resulting controlled cleaving may call for the application of energy to the donor substrate to initiate and/or propagate cleaving along the cleave region, leaving a thin film of transferred material remaining bonded to the target.
  • Stress in the donor may arise from a variety of sources.
  • One possible source of stress may be formation of the cleave region.
  • the energetic implantation of particles into the donor substrate creates a subsurface cleave region different from the surrounding material. This may give rise to stress at surface and subsurface locations.
  • the cleave region itself may not be formed under uniform conditions, leading to internal stress.
  • edge/initiation portions of a cleave region may receive higher doses of implanted particles than other portions of the cleave region, leading to further stress within the donor substrate.
  • the donor substrate may be exposed to conditions such as elevated temperatures, reduced pressures, and/or external energies (e.g., plasma) in order to accomplish bonding the implanted face of the donor substrate to the target. These conditions can give rise to internal stress being created within the donor substrate.
  • Still other sources of possible stress in the donor substrate may arise from the cleaving process itself.
  • one or more forms of energy may be applied to the donor in order to release the thin layer along the cleave region.
  • energy can include but are not limited to thermal energy (e.g., an electron beam), optical energy (e.g., a laser), pneumatic energy (e.g., a pressurized gas jet), hydraulic energy (e.g., a pressurized water jet), and mechanical energy (e.g., application of a blade).
  • certain controlled cleaving processes may involve an initiation phase creating a cleave front, followed by a propagation phase to cause the cleave front to migrate across the substrate, ultimately resulting in the complete detachment of a thin layer of material from the donor substrate.
  • the same (or different) types of energy may be applied (at the same or different magnitudes) for cleave initiation, as are subsequently used to propagate a cleave front that has been formed.
  • cleaving processes may operate differently in certain portions of the substrate than others.
  • the existence of a bevel in the target substrate may preclude contact with edge regions of the donor substrate. Upon cleaving, this can result in edge portions of the donor remaining bound to the donor rather than being transferred to the target. This and other phenomena associated with cleaving, can introduce stress internal to the donor substrate.
  • FIGS. 5A-5F are simplified cross-sectional views of flow diagram showing an embodiment of this process.
  • Figure 5A shows the donor substrate 502. In this initial state, the donor substrate is relatively homogenous and substantially unaffected by previous external forces that might give rise to internal stresses.
  • Figure 5B shows attachment of the backing substrate 504 to the donor substrate.
  • this attachment may be accomplished utilizing reversible processes, wherein it is foreseen that the backing substrate will ultimately be released from the donor at some future point (e.g., following the transfer of several thin layers or after each transfer).
  • reversible processes can include but are not limited to reversible adhesives, solder, and lift off systems such as Laser Lift Off (LLO) or Thermal Lift Off (TLO).
  • attachment of the backing substrate to the donor may be accomplished under irreversible conditions. There, it is not foreseen that the backing substrate will be released from the donor. Examples of such generally irreversible processes can include but are not limited to permanent adhesives, thermo-compression bonding, Transient Liquid- Phase (TLP) bonding and frit-based ceramic bonding.
  • TLP Transient Liquid- Phase
  • Figure 5C shows a subsequent step, wherein a cleave region 506 is formed in the donor substrate.
  • this cleave region may be formed by the implantation of energetic particles 508 into the face 502a of the donor substrate that is not attached to the backing substrate.
  • the donor substrate/backing substrate assembly can allow for higher power density implants with less temperature excursion. These benefits occur by having a stiffer assembly that allows for more gas cooling backpressure and/or mechanical pressure to be applied on the backside for thermal heat dissipation. For example, at a 3x10 17 H+/cm 2 dose with about 100 pieces of 2-inch GaN substrates over a 4,000 cm 2 area scanned by a 150keV, 60mA proton beam, the areal power density will be about 2.25 W/cm . If a temperature rise of no more than 40°C temperature is desired from the assembly to implant cooling plate, a thermal conductance of 0.056 W/cm 2 -K is required.
  • the required thickness is less than the GaN substrate thickness which is typically 400-500 ⁇ .
  • the required backing plate thickness would dictate the required backing plate thickness.
  • a 1mm Mo plate would thus be sufficient to satisfy the implant conditions above.
  • a slightly larger diameter of the backing plate would allow edge clamping of the assembly without contacting the 2" (50.8mm) GaN substrate.
  • the minimum backing plate thickness can be substantial to avoid excessive plate bending during backside gas application.
  • a deep (750 keV) proton implant at 60mA over 4 300mm silicon wafers would apply a thermal load of 45kW over 4,000 cm 2 area or about 11.2 W/cm . Assuming no more than 100°C temperature rise, a thermal conductance of 0.112 W/cm 2 -K is required. According to Figure 9, approximately 20T of backpressure is required and the gap cannot exceed about 20 ⁇ .
  • FIG. 5D shows the next step, wherein the implanted face 502a is bound to a target substrate 510. This bonding can take a variety of forms, including the use of a release layer as described further below in connection with Figure 7.
  • Figure 5E shows the cleaving process.
  • applied energy interacting with the cleave region results in a cleave 511 of the donor substrate material.
  • This cleave transfers the thin film of donor material 512 to the surface of the target substrate.
  • Figure 5F shows the post-cleaving state of the donor substrate.
  • the backing substrate remains attached, providing physical support to resist buckling/fracture of the donor substrate in order to release internal stress accumulated therein.
  • the exposed face of the donor substrate may exhibit some roughness 514, that roughness does not rise to the level of buckling or fractures that could render the donor substrate unsuited for reclamation.
  • the donor substrate supported by the backing substrate is now available for reclamation processes.
  • reclamation can include but are not limited to grinding, polishing, plasma exposure, wet chemical exposure, and/or thermal exposure.
  • the presence of the backing substrate supporting the donor substrate may further serve to stabilize the latter during such reclamation processing. That is, stress arising from the application of energy to prepare the donor substrate surface for subsequent implant, may be addressed by the backing substrate to prevent uncontrolled stress release giving rise to buckling, fracture, etc.
  • the backing substrate should be compatible with exposure to the conditions under which reclamation is to take place. For example, where reclamation involves exposure to a plasma, the use of certain kinds of metal for the backing substrate may be discouraged in order to avoid arcing. In another example, where the reclamation involves etching conditions, the backing substrate should not comprise a material susceptible to degradation by repeated exposure to the etching conditions, to the point that it is unable to perform its stabilizing function.
  • the backing substrate may comprise a material matching in thermal expansion coefficient over the temperature range of interest. This would limit deformations and temperature induced stresses that can lower yield and achievable specifications such as surface flatness.
  • Materials such as molybdenum, tungsten, aluminum nitride, Mullite and CTE-matched glasses could satisfy criteria to be used as a backing plate material. Apart from mechanical flatness, CTE-matching and stiffness, making the backing plate slightly larger in diameter can also have practical benefits. In some applications this may also be advantageous to choose a material which is electrically conductive.
  • a lip of backing material extending from the GaN edge would allow mechanical clamping. For most applications, a lip of millimeter scale would be sufficient.
  • a backing substrate for a donor is now given in connection with the fabrication of hetero-structure layers and 3D-IC semiconductor devices.
  • an InGaAs layer is transferred onto a silicon substrate to form a 3D monolithic integration assembly.
  • the implant energy in this application could be on the order of 50-300keV.
  • high-energy proton implantation of 300keV to lMeV and even 2MeV are used to position a cleave plane well below the device layers to allow cleaving and transfer of a device layer onto a target substrate which collects multiple layers to form a 3D-IC structure.
  • the use of a backing substrate would allow for high-power implantation and efficient manufacturing without overheating the donor substrate.
  • HB-LED high- brightness light emitting diode
  • An optoelectronic device such as a HB-LED may rely upon materials exhibiting semiconductor properties, including but not limited to type III/V materials such as gallium nitride (GaN) that is available in various degrees of crystalline order. However, these materials are often difficult to manufacture.
  • type III/V materials such as gallium nitride (GaN) that is available in various degrees of crystalline order.
  • GaN gallium nitride
  • Figure 6 shows a simplified example of a substrate combination 600 comprising a donor substrate 602 that is attached to a backing substrate 604.
  • the donor substrate 602 comprises high-quality GaN material, suitable for use in the fabrication of a HB-LED device.
  • the backing substrate 604 comprises a material that is compatible with the high-quality GaN material of the donor substrate.
  • the backing substrate may exhibit a Coefficient of Thermal Expansion (CTE) that substantially matches, or is complementary to, that of the donor substrate.
  • CTE Coefficient of Thermal Expansion
  • the backing substrate may exhibit properties that serve to accommodate and/or relieve internal stress arising in the donor substrate as a result of being subjected to one or more reclamation processes conducted in various environments.
  • reclamation processes can include but are not limited to, grinding, polishing, plasma or ion beam assisted etching, wet chemistry, thermal, vacuum, implantation, and others.
  • the backing structure may include a feature such as a lip 606.
  • a lip feature can serve to hold the donor/backing substrate assembly onto a platen or holder without contacting or covering the front face of the donor substrate.
  • the backing structure also has a thickness, selected to satisfy the larger of a minimum thickness requirement from implant or reclamation processes.
  • FIG. 7 shows a simplified view of one fabrication process 700 to form a permanent substrate offering a template for the subsequent growth of high quality GaN for opto-electronic applications.
  • a donor substrate 702 comprises high-quality GaN material.
  • a backing substrate 703 is attached to the donor substrate.
  • a cleave region 704 is located at a sub-surface region of the donor substrate. This cleave region may be formed, for example, by the energetic implantation 705 of particles such as hydrogen ions, into one face of the GaN donor substrate.
  • FIG. 7A is a simplified view illustrating the internal structure of a GaN substrate, showing the Ga face and the N face.
  • the implanted Ga face of the GaN substrate is bonded to a releasable substrate 706 bearing a release layer 708.
  • the material of the releasable substrate may be selected such that its Coefficient of Thermal Expansion (CTE) substantially matches that of the GaN.
  • the material of the releasable substrate may also be selected to be transparent to incident laser light as part of a Laser Lift Off (LLO) process.
  • LLO Laser Lift Off
  • a releasable substrate comprising glass may be used.
  • the release layer may comprise a variety of materials capable of later separation under controlled conditions.
  • candidate releasable materials can include those undergoing conversion from the solid phase to the liquid phase upon exposure to thermal energy within a selected range. Examples can include soldering systems, and systems for Thermal Lift Off (TLO).
  • the release system may comprise silicon oxide.
  • this bond-and-release system can be formed by exposing the workpieces to oxidizing conditions.
  • this bond-and-release system may be formed by the addition of oxide, e.g., as spin-on-glass (SOG), or other spin on material (e.g., XR-1541 hydrogen silsesquioxane electron beam spin-on resist available from Dow Corning), and/or Si0 2 formed by sputtering or Plasma Enhanced Chemical Vapor Deposition (PECVD) techniques.
  • SOG spin-on-glass
  • PECVD Plasma Enhanced Chemical Vapor Deposition
  • These steps include surface preparation 714 of the separated GaN layer (e.g., the formation of an oxide), bonding 716 the separated GaN layer to a permanent substrate 718, and finally the removal of the releasable substrate utilizing the release layer (e.g., utilizing a LLO process 720), to result in the N face of the separated GaN layer being bonded to the permanent substrate.
  • surface preparation 714 of the separated GaN layer e.g., the formation of an oxide
  • bonding 716 the separated GaN layer to a permanent substrate 718 e.g., the formation of an oxide
  • the release layer e.g., utilizing a LLO process 720
  • Ga face is exposed and available for growth of additional high quality GaN material under desired conditions.
  • Additional GaN may be formed by Metallo-Organic Chemical Vapor Deposition (MO-CVD), for example. That additional thickness of GaN material (with or without the accompanying substrate and/or dielectric material) may ultimately be incorporated into a larger optoelectronic device structure (such as a HB-LED).
  • MO-CVD Metallo-Organic Chemical Vapor Deposition
  • separation of the GaN film results in the valuable GaN donor substrate comprising high quality GaN material, being available for re-use in order to create additional template structures for growth of additional high quality GaN.
  • the donor substrate can be exposed to additional implantation, and then bonding to another releasable substrate.
  • the GaN donor substrate may need to first be reclaimed so that it is suitable for the intended processing.
  • the Ga face of the donor substrate may exhibit properties such as surface roughness, defects, and/or non- planarity resulting from the previous cleaving step, that render it unsuitable for immediate implantation and bonding.
  • Donor substrate reclamation procedures may comprise exposure to one or more of the following environments: grinding, polishing, plasma or ion beam assisted etching, wet chemistry, thermal, vacuum, and others.
  • FIG. 8 is a simplified flow diagram illustrating a process 800 according to an embodiment.
  • a donor substrate is provided in a first step 802.
  • a backing substrate is attached to the donor substrate.
  • the donor substrate attached to the backing substrate is exposed to conditions giving rise to internal stress. The presence of the backing substrate serves to stabilize the donor substrate under these conditions, thereby allowing reclamation of the donor substrate in connection with subsequent processing.
  • Such a reclamation is shown as step 808 in Figure 8. As shown by the loop, that reclamation may be followed in rum by processing giving rise to internal stress in the donor substrate (e.g., implantation, bonding, cleaving, etc.).
  • processing giving rise to internal stress in the donor substrate (e.g., implantation, bonding, cleaving, etc.).
  • the donor assembly (backing and donor substrates) may need to meet flatness and stiffness requirements.
  • a donor substrate could exhibit excessive bow and warp that can result in non-uniform reclamation of the donor surface.
  • the donor surface is stabilized in flatness and can be reclaimed in a manner that meets surface specifications.
  • a 2" diameter GaN substrate of 470um thickness was modeled using finite element analysis. The GaN substrate was given an initial bow value of 74um (center to edge bow across the principal face).
  • This level of bow is representative of a stress level of approximately 700MPa extending 5um into the GaN substrate from the top surface. This represents a stress state of the GaN substrate that must be removed through reclaim. Attaching a backing substrate can allow uniform lapping, polishing and CMP processes to remove this stress layer by lowering the bow value to about the same order as the target layer removal value (in this case about 5um). When bonded to a 3mm Mo backing substrate, the bow is reduced from 74um to 3.9um. A 5mm Mo backing substrate would reduce the bow to 1.6um. Bow reduction of this magnitude would make the reclamation processes uniform and predictable.
  • GaN material may call for growth of GaN material from the N face, rather than from the Ga face.
  • Some applications e.g., power electronics
  • Incorporated by reference herein for all purposes are the following articles: Xun Li et al., "Properties of GaN layers grown on N-face free-standing GaN substrates", Journal of Crystal Growth 413, 81-85 (2015); A.R.A. Zauner et al, "Homo-epitaxial growth on the N-face of GaN single crystals: the influence of the misorientation on the surface morphology", Journal of Crystal Growth 240, 14-21 (2002).
  • template blank structures of some embodiments could feature a GaN layer having an N face that is exposed, rather than a Ga face.
  • an N face donor assembly could be used to fabricate a Ga face final substrate when bonded to a final substrate instead of a releasable transfer substrate as in Figure 6.
  • Such embodiments could be particularly amenable to the use of a backing substrate to stabilize the donor substrate after cleaving.
  • the N-face of a GaN crystal is more chemically reactive compared to the Ga-face. Accordingly, the presence of a backing substrate could serve to flatten the assembly and reduce undesired enhanced etching of surfaces due to bow and warp high areas acting upon the CMP processes.
  • a backing substrate for GaN transfer processes While the above discussion has focused upon the use of a backing substrate for GaN transfer processes, embodiments are not limited to such approaches. Certain embodiments may employ a backing substrate for fabrication processes involving a different Group III/V material such as GaAs. In particular embodiments, sapphire may be particularly suited to serve as a backing substrate for the transfer of GaAs material from a donor.
  • a donor substrate comprising a first face and a second face

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  • Engineering & Computer Science (AREA)
  • Manufacturing & Machinery (AREA)
  • Computer Hardware Design (AREA)
  • Microelectronics & Electronic Packaging (AREA)
  • Power Engineering (AREA)
  • Physics & Mathematics (AREA)
  • Condensed Matter Physics & Semiconductors (AREA)
  • General Physics & Mathematics (AREA)
  • Crystals, And After-Treatments Of Crystals (AREA)
  • Mechanical Treatment Of Semiconductor (AREA)
  • Led Devices (AREA)
  • Recrystallisation Techniques (AREA)

Abstract

Un substrat donneur (502 ; 602 ; 702) dans un procédé de transfert de couche est stabilisé par fixation d'un substrat de support (504 ; 604 ; 703). Le substrat de support (504 ; 604 ; 703) permet une stabilisation thermique et mécanique pendant des processus d'implant à haute puissance. Lors du clivage du substrat donneur (502 ; 602 ; 702) pour libérer une couche mince de matériau sur un substrat cible (510), le substrat de support (504 ; 604 ; 703) empêche une libération non contrôlée de la contrainte interne conduisant à la déformation/fracture du substrat donneur (502 ; 602 ; 702). La contrainte interne peut s'accumuler dans le substrat donneur (502 ; 602 ; 702) en raison de processus tels que la formation de la région de clivage (506 ; 704), la liaison au substrat cible (510), et/ou le processus de clivage lui-même, avec une courbure et une déformation non contrôlées empêchant potentiellement la récupération/réutilisation du substrat donneur (502 ; 602 ; 702) dans les processus de transfert de couche subséquents. Selon certains modes de réalisation, le substrat de support (504 ; 604 ; 703) peut présenter un coefficient de dilatation thermique (CTE) correspondant sensiblement ou complémentaire à celui du substrat donneur (502 ; 602 ; 702). Selon certains modes de réalisation, le substrat de support (504 ; 604 ; 703) peut comprendre une caractéristique telle qu'une lèvre (606).
EP17755560.4A 2016-07-12 2017-07-12 Procédé d'un substrat donneur soumis à une récupération Withdrawn EP3485505A1 (fr)

Applications Claiming Priority (5)

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US201662361468P 2016-07-12 2016-07-12
US201662367911P 2016-07-28 2016-07-28
US15/643,370 US20180019169A1 (en) 2016-07-12 2017-07-06 Backing substrate stabilizing donor substrate for implant or reclamation
US15/643,384 US20180033609A1 (en) 2016-07-28 2017-07-06 Removal of non-cleaved/non-transferred material from donor substrate
PCT/IB2017/054209 WO2018011731A1 (fr) 2016-07-12 2017-07-12 Procédé d'un substrat donneur soumis à une récupération

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CN115803851B (zh) * 2021-01-21 2023-06-30 信越工程株式会社 工件分离装置及工件分离方法
JP7475503B2 (ja) 2021-02-04 2024-04-26 三菱電機株式会社 半導体基板の製造方法および半導体装置の製造方法
JP7484773B2 (ja) * 2021-03-04 2024-05-16 信越半導体株式会社 紫外線発光素子用エピタキシャルウェーハの製造方法、紫外線発光素子用基板の製造方法及び紫外線発光素子用エピタキシャルウェーハ

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US8679942B2 (en) * 2008-11-26 2014-03-25 Soitec Strain engineered composite semiconductor substrates and methods of forming same
JP2014157979A (ja) * 2013-02-18 2014-08-28 Sumitomo Electric Ind Ltd Ｉｉｉ族窒化物複合基板およびその製造方法、積層ｉｉｉ族窒化物複合基板、ならびにｉｉｉ族窒化物半導体デバイスおよびその製造方法
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