WO2015195314A1

WO2015195314A1 - Enhancing the emissivity of a donor substrate for ion implantation

Info

Publication number: WO2015195314A1
Application number: PCT/US2015/033650
Authority: WO
Inventors: Joseph Gillespie; Aniruddha A. VENGURLEKAR
Original assignee: Gtat Corporation
Priority date: 2014-06-19
Filing date: 2015-06-02
Publication date: 2015-12-23
Also published as: TW201603193A

Abstract

The disclosed embodiments relate to techniques for enhancing the emissivity of a donor substrate for ion implantation. According to embodiments of the present disclosure, a donor substrate of crystalline material is provided having a front surface and a back surface, wherein an ion beam directed toward the front surface of the donor substrate is configured to implant ions into the donor substrate. An emissivity coating is applied to the back surface of the donor substrate that enhances an emissivity of the donor substrate. Further, according to embodiments of the present disclosure, a donor substrate of crystalline material is provided having a front surface and a back surface, and an emissivity coating is applied onto the back surface that enhances an emissivity of the donor substrate. An ion beam is generated and directed toward the front surface of the donor substrate, and an ion dosage is implanted into the donor substrate.

Description

TITLE

ENHANCING THE EMISSIVITY OF A DONOR SUBSTRATE FOR ION

IMPLANTATION

CROSS-REFERENCE TO RELATED APPLICATION

The present application claims the benefit of U.S. Patent Application No. 62/014,338 filed June 19, 2014, which is incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention.

[0001] The present invention relates to enhancing the emissivity of a donor substrate, particularly sapphire, for ion implantation.

2. Description of the Related Art.

[0002] Ion implantation is a materials engineering process by which ions of a source material are accelerated in an electrical field and impacted into a solid target substrate. This process is used to change the physical, chemical, or electrical properties of the solid. Ion implantation is often used in semiconductor device fabrication and in metal finishing, as well as various applications in materials science. Ion implantation equipment typically consists of an ion source, where ions of the desired element are produced, an accelerator, where the ions are accelerated to a specific energy, and a target chamber, where the ions impinge on a target, which is the material to be implanted. The energy of the ions, as well as the ion species and the composition of the target, determine the depth of penetration of the ions in the solid, i.e., the "range" of the ions.

[0003] There are various uses for ion implantation, such as the introduction of dopants (e.g., boron, phosphorus or arsenic) in a semiconductor. For instance, modification of semiconductors such as silicon wafers is often implemented by ion implanters, where a surface is uniformly irradiated by a beam of ions or molecules, of a specific species and prescribed energy. Another use for ion implantation is for cleaving (exfoliating) thin sheets (lamina) of hard crystalline materials such as silicon, sapphire, etc. As shown in FIG 1, generally, this process involves implanting light ions 20 into a donor substrate 10 where they will stop below the surface in a layer. The material may then be heated (for example), causing the material above the implanted layer to cleave off or exfoliate in a sheet or lamina 40.

[0004] In some cases, it is desirable to use a thicker "handle" substrate to provide mechanical support for the lamina, and bonding to the support can occur either before or after exfoliation. For example, a temporary bond may be created with the donor body (at the portion that will become lamina) before the cleaving, thereby forming a composite structure. When cleaving (exfoliating) the lamina from the donor body, both the lamina and the backing substrate/handle are cleaved from the donor body. Bonding before exfoliation is particularly advantageous for very thin, delicate lamina to assist in subsequent handling and processing steps.

[0005] Generally, producing quality exfoliation results depends upon maintaining a high level of temperature uniformity in the donor substrate during ion implantation. When implanting ions in a donor substrate made of sapphire, for example, the optimum implantation temperature occurs in an elevated temperature range where common active wafer cooling techniques are not suitable for achieving the desired temperature, while also maintaining excellent temperature uniformity. Consequently, cooling the substrate by radiation (e.g., cooling to the temperature of the surrounding environment) can often be the most practical manner of cooling that allows for the desired temperature and temperature uniformity.

[0006] When cooling only by radiation, however, the heat transfer rate (e.g., the exchange of thermal energy by dissipating heat) can be highly dependent on the emissivity (e.g., the ability of an object's surface to emit energy by radiation) of the body the heat is being emitted from, as well as the emissivity of the cooler surrounding environment that the heat is being absorbed into. Sapphire, for example, has a relatively low level of emissivity at high temperatures, thereby resulting in low heat transfer rates. Consequently, the ability to implant ions in a sapphire substrate using higher beam powers is limited in order to keep the substrate at the desired implantation temperature, which in turn limits the productivity of the ion implanter.

SUMMARY OF THE INVENTION

[0007] The disclosed embodiments relate to techniques for enhancing the emissivity of a donor substrate for ion implantation. In particular, an emissivity coating that enhances an emissivity of a donor substrate may be applied to a back surface of the donor substrate. Applying the emissivity coating for ion implantation may be particularly useful for substrates made of a crystalline material that has a low emissivity rate at a desired implantation temperature, such as sapphire.

[0008] According to embodiments of the present disclosure, a donor substrate of crystalline material is provided having a front surface and a back surface, wherein an ion beam directed toward the front surface of the donor substrate is configured to implant ions into the donor substrate. An emissivity coating is applied to the back surface of the donor substrate that enhances an emissivity of the donor substrate.

[0009] Further, according to embodiments of the present disclosure, a donor substrate of crystalline material is provided having a front surface and a back surface, and an emissivity coating is applied onto the back surface that enhances an emissivity of the donor substrate. An ion beam is generated and directed toward the front surface of the donor substrate, and an ion dosage is implanted into the donor substrate.

[0010] It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are intended to provide further explanation of the present invention, as claimed.

BRIEF DESCRIPTION OF THE DRAWINGS [0011] The foregoing and other objects, features, aspects and advantages of the embodiments disclosed herein will become more apparent from the following detailed description when taken in conjunction with the following accompanying drawings.

[0012] FIG. 1 illustrates a general ion implantation following by exfoliation.

[0013] FIG. 2 illustrates an example schematic representation of a substrate donor having an emissivity coating, and FIG 3 illustrates an example schematic representation of ion implantation into the substrate donor having an emissivity coating.

[0014] FIGS. 4A and 4B illustrate example schematic representations of emissivity levels in a standard substrate donor and the substrate donor having an emissivity coating, respectively.

[0015] FIG. 5 illustrates an example simplified procedure for applying an emissivity coating to a donor substrate.

[0016] FIG. 6 illustrates an example simplified procedure for implanting an ion dosage into a donor substrate having an emissivity coating.

[0017] It should be understood that the above-referenced drawings are not necessarily to scale, presenting a somewhat simplified representation of various preferred features illustrative of the basic principles of the disclosure. The specific design features of the present disclosure, including, for example, specific dimensions, orientations, locations, and shapes, will be determined in part by the particular intended application and use environment.

DETAILED DESCRIPTION OF THE INVENTION

[0018] The present invention relates to implantation and exfoliation of crystalline materials having an emissivity coating.

[0019] According to the present invention, the method comprises the step of providing a donor substrate of crystalline material having a front surface through which ions are to be implanted and a back surface comprising an emissivity coating, described in more detail below. The donor substrate can be any material, including, for example, sapphire, silicon, silicon carbide, gallium nitride, gallium arsenide, aluminum nitride, diamond, or germanium, and can be a material of any practical thickness (such as from about 100 microns to about 10 mm) as well as any size and shape, including square, rectangular, or round, depending on the desired size and shape of the resulting crystalline lamina. Preferably the donor substrate comprises sapphire.

[0020] The method further comprises the step of implanting at least one ion dosage through the top surface of the donor substrate to form a cleave plane beneath the top surface and within the donor substrate. The ion dosage can comprise, for example, hydrogen, helium, or a combination thereof. Overall implantation conditions can be varied as needed to produce the desired cleave plane at a depth required to provide a crystalline lamina of the desired thickness. For example, the total implant dosage may be any dosage between about 1.0 x 10¹⁴ and 1.0 x

10 18 H/cm 2 , such as 0.5 - 3.0 x 1017 H/cm 2. The total dosage energy can also be varied, such as greater than or equal to about 50 keV, including between about 500 keV to about 3 MeV. In some embodiments, the ion implantation temperature may be maintained between about 200°C and 950°C, such as between 300°C and 800°C or between 550°C and 750°C, and this can be adjusted depending upon the specific type of donor body. For example, when the donor substrate is sapphire, the ion implantation temperature may be between 500°C and 800°C.

[0021] As noted above, in the method of the present invention, the donor substrate further comprises an emissivity coating applied onto the back surface. Notably, the emissivity coating has been found to be particularly useful for donor substrates comprising crystalline material, such as sapphire, having a low emissivity level at a desired implantation temperature, which may be a high temperature due to high beam powers. That is, the crystalline material may take a long time to cool after being heated to the desired ion implantation temperature. For example, such materials may typically have an emissivity level below 0.6, approximately, at the desired implantation temperature. Along these lines, such materials may also be transparent to infrared light (e.g., used as an infrared window) and/or may be capable of transmitting long wavelengths. Further, the donor substrate may be single-side polished or double-side polished, which may have a further effect on the emissivity of the wafer.

[0022] FIG. 2 illustrates an example schematic representation of a substrate donor having an emissivity coating on its back surface. As shown in FIG. 2, an emissivity coating 50 can be applied to the donor substrate 50. The emissivity coating 50 enhances an emissivity of the donor substrate 10. That is, the emissivity coating 50 increases the relative ability of the surface of the donor substrate 10 to emit energy by radiation. By increasing the emissivity of the donor substrate 10, the heat transfer rate of the substrate 10 can also be increased. Thus, cooling methods that allow for excellent thermal uniformity of the substrate 10, such as cooling by radiation, can be utilized, even at high temperatures. Also, ion implantation can occur at a greater level of productivity (e.g., through the use of more powerful ion beams).

[0023] The emissivity coating can comprise a variety of substances and/or layers designed to significantly improve the thermal efficiency of the donor substrate. For example, the emissivity coating may comprise a carbonaceous substance, a graphitic substance, a metallic substance, and/or any combination thereof. Further, the emissivity coating may comprise an electroless nickel compound and/or a black electroless nickel compound. Even further, the emissivity coating may be oxidized so as to have a further beneficial effect on emissivity levels of the donor substrate.

[0024] The emissivity coating can be applied onto the donor substrate using any suitable deposition method. For example, the emissivity coating may be sputtered onto the donor substrate by ejecting the emissivity coating from a source (e.g., magnetron) onto the substrate. Various methods of sputtering of the emissivity coating are possible, such as RF sputtering, ion- beam sputtering, gas flow sputtering, and so forth. When sputtering the emissivity coating onto the donor substrate, an adhesive layer (not shown) may act as an intermediate layer between the donor substrate and the emissivity coating. To this point, the adhesive layer may be applied directly to the donor substrate in order to assist in bonding the emissivity coating to the substrate. Notably, the adhesive layer itself may affect the emissivity level of the donor substrate. That is, in addition to the emissivity coating, the adhesive layer may emit radiation and thus act as another emissivity coating. Therefore, the emissivity level of the donor substrate, which is enhanced by the emissivity coating, may be further altered when applying an adhesive layer to the substrate.

[0025] Further, the emissivity coating may be plated onto the donor substrate by covering the substrate with the coating and applying heat and pressure fuse the two together or by vapor deposition. Even further, the emissivity coating may be plated onto the donor substrate using evaporation techniques where the source material carrying the emissivity coating is evaporated in a vacuum, and the vacuum allows vapor particles to travel directly to the substrate, causing the particles to condense back to a solid state and the source material to transfer over the surface of the substrate, thus forming the coating. Yet even further, the emissivity coating may be painted onto the donor substrate using conventional painting techniques, including spraying the coating onto the substrate.

[0026] The emissivity coating should be evenly deposited onto the donor substrate so as to ensure even conductivity and overall thermal performance. The thickness of the deposited emissivity coating may vary according to the composition of the coating, as well as the crystalline material making up the substrate. Preferably, the emissivity coating may applied onto the back surface of the substrate such that the coating layer is thick enough to be optically opaque.

[0027] FIG. 3 illustrates an example schematic representation of ion implantation into the substrate donor having an emissivity coating. As shown in FIG. 3, an ion beam 20 may be directed toward the front surface of the donor substrate 10 to implant ions 30 into the donor substrate 10. Conversely, the emissivity coating 50 may be applied onto the opposite surface of the donor substrate 10, e.g., the back surface of the substrate 10. Applying the emissivity coating 50 onto the backside of the donor substrate 10 can increase the radiation heat transfer rate during ion implantation. In other words, heat is transferred from the donor substrate 10 at a higher rate, thus allowing the substrate 10 to be cooled by radiation, which further allows for a greater level of thermal uniformity in the wafer.

[0028] During the ion implantation, the donor substrate 10 may be housed within a housing (not shown). The ion beam 20 may be generated by an ion beam generator (i.e., ion source), and an ion beam controller may be configured to control the ion beam generation so as to implant the ions 30 into the donor substrate 10. The ion dosage may comprise hydrogen ions, helium ions, or both. Moreover, the donor substrate 10 may include a cleave plane beneath the front surface thereof, and the cleave plane may also comprise an implanted ion dosage.

[0029] FIGS. 4A and 4B illustrate example schematic representations of emissivity levels in a standard substrate donor and the substrate donor having an emissivity coating, respectively. As shown in FIGS. 4A and 4B, thermal radiation 60 occurs through the front and back surfaces of the donor substrate 10. As explained in detail above, the emissivity coating 50 enhances an emissivity of the donor substrate 10. That is, the emissivity coating 50 increases the amount of radiative energy emitted by the surfaces of the donor substrate 10, thereby increasing the heat transfer rate of the substrate 10. As an example, where the donor substrate 10 is sapphire, which has a low emissivity level at high temperatures, relatively low amounts of thermal radiation 60 are emitted from the surface of the wafer when the emissivity coating 50 is not applied, as shown in FIG. 4A. In contrast, when the emissivity coating 50 is applied to the back surface of the sapphire donor substrate 10, as shown in FIG. 4B, relatively high amounts of thermal radiation 60 are emitted from the surface of the wafer. That is, the thermal productivity of the donor substrate 10 is greatly increased, as the wafer is able to cool more quickly, particularly at higher temperatures. Notably, depositing the emissivity coating 50 onto the donor substrate 10 can result in substrate temperature drops consistent with an increase in emissivity of up to three to four times.

[0030] FIG. 5 illustrates an example simplified procedure for applying an emissivity coating to a donor substrate. As shown in FIG. 5, the procedure 500 may start at step 505, continue to step 510, and so forth. Although FIG. 5 depicts steps in a particular order, it should be understood that the depicted embodiment is not limiting, and the particular order is depicted merely for illustration purposes.

[0031] At step 510, a donor substrate of crystalline material is provided having a front surface and a back surface. Because the donor substrate is intended to undergo ion implantation, an ion beam directed toward the front surface of the donor substrate is configured to implant ions into the donor substrate. Then, at step 515, an emissivity coating that enhances an emissivity of the donor substrate is applied to the back surface of the donor substrate. As such, the emissivity coating increases the amount of radiative energy emitted by the surfaces of the donor substrate, thereby increasing the heat transfer rate of the substrate. The process illustratively ends at step 520.

[0032] FIG. 6 illustrates an example simplified procedure for implanting an ion dosage into a donor substrate having an emissivity coating. As shown in FIG. 6, the procedure 600 may start at step 605, continue to step 610, and so forth. Although FIG. 6 depicts steps in a particular order, it should be understood that the depicted embodiment is not limiting, and the particular order is depicted merely for illustration purposes.

[0033] At step 610, a donor substrate of crystalline material is provided having a front surface, a back surface, and an emissivity coating applied onto the back surface that enhances an emissivity of the donor substrate. Then, at step 615, an ion beam directed toward the front surface of the donor substrate is generated, e.g., via an ion beam generator. The ion beam generation may be controlled by an ion beam controller. At step 620, an ion dosage is implanted into the donor substrate. The process illustratively ends at step 625.

[0034] The method of the present invention may further comprise the step of exfoliating the crystalline lamina from the donor substrate. Any method known in the art can be used to cleave or exfoliate the lamina, including thermal cleaving or mechanical cleaving, and specific cleaving conditions, such as exfoliation temperature, heating rate, exposure time, and exfoliation pressure, can be varied depending, for example, on the lamina thickness as well as on the implant conditions used. For example, the crystalline lamina of sapphire having a thickness of less than 100 microns, such as less than 50 microns, less than 30 microns, less than 25 microns, and less than 15 microns, can be thermally exfoliated from the donor body using temperatures from about 400°C to about 1200°C, such as from about 600°C to about 1000°C, and for a time between about 1 minute to about 60 minutes, such as from about 5 minutes to about 30 minutes. Higher exfoliation temperatures would generally require less time. In addition, a thermal temperature ramp up can be used in order to shorten the amount of time spent at the exfoliation temperature. By adjusting implantation and exfoliation conditions, the area of the resulting lamina that is substantially free of physical defects can be maximized. Optionally, the donor body may undergo thermal treatment prior to exfoliation. For example, the donor body may be heated below the exfoliation temperature in order to cause damage evolution in the cleave layer, such as by Oswalt ripening. Heat treatment may reduce the time and temperature needed for exfoliation of a full lamina and may produce a smoother cleave surface. An additional or alternative short duration thermal treatment can also be optionally used after exfoliation to anneal the crystalline lamina if desired in order remove or reduce any damage potentially caused by implantation. [0035] For thin crystalline lamina, such as a lamina having a thickness of less than 50 microns, it may be desirable to bond a backing substrate, such as glass or plastic, to the implanted donor body prior to exfoliation, in order to improve handling of the resulting lamina. Any bonding technique may be used to bond the two materials together, temporarily or permanently, in order to form a bonded composite, including the use of various adhesives for bonding the lamina to the backing substrate, such as, for example, glass frit, polymer adhesives, anodic bonding, and atomic (fusion) bonding. Notably, a temporary bond may be created with the donor substrate (at the portion that will become lamina) before the cleaving, thereby forming a composite structure. When cleaving (exfoliating) the lamina from the donor substrate, both the lamina and the backing substrate/handle are cleaved from the donor substrate. The remaining donor substrate can be reused for a subsequent implantation sequence or of other purposes, as desired. The backing substrate may be used to optionally further process the cleaved lamina, such as to polish the cleaved surface or to apply additional coatings or layers to the lamina, and is then removed to produce a free-standing lamina. Alternatively, the backing substrate may be permanently attached, which may be advantageous for various applications of the cleaved lamina. For example, the backing substrate may be a transparent material, such as glass, which remains permanently bonded to the exfoliated lamina, and the resulting multilayer composite may be used as a screen for an electronic device. Non-transparent substrates may be useful in applications such as adding a protective layer to decorative glass or plastic.

[0036] The present invention further relates to a thin, crystalline lamina (or film), or also to a composite material formed by adhering a crystalline lamina to a substrate, such as glass or plastic. Such a lamina or composite material may be transparent and used for screens (cover glasses) for consumer goods, such as watches, mobile phones, and other various electronics, as well as for other purposes.

[0037] In one specific embodiment, the present invention may be used to prepare a cover plate of an electronic device. For example, there are many types of mobile electronic devices currently available which include a display window assembly that is at least partially transparent. These include, for example, handheld electronic devices such media players, mobile telephones (cell phones), personal data assistants (PDAs), pagers, and laptop computers and notebooks. The display screen assembly may include multiple component layers, such as, for example, a visual display layer such as a liquid crystal display (LCD), a touch sensitive layer for user input, and at least one outer cover layer used to protect the visual display. Each of these layers are typically laminated or bonded together.

[0038] Many of the mobile electronic devices used today are subjected to excessive mechanical and/or chemical damage, particularly from careless handling and/or dropping, from contact of the screen with items such as keys in a user's pocket or purse, or from frequent touch screen usage. For example, the touch screen surface and interfaces of smartphones and PDAs can become damaged by abrasions that scratch and pit the physical user interface, and these imperfections can act as stress concentration sites making the screen and/or underlying components more susceptible to fracture in the event of mechanical or other shock. Additionally, oil from the use's skin or other debris can coat the surface and may further facilitate the degradation of the device. Such abrasion and chemical action can cause a reduction in the visual clarity of the underlying electronic display components, thus potentially impeding the use and enjoyment of the device and limiting its lifetime.

[0039] Accordingly, a composite material described herein may comprise a plastic or glass backing substrate (e.g., transparent) bonded to a thin lamina (e.g., also transparent) of a hard crystalline material (e.g., sapphire) having a thickness of less than 100 microns, such as less than 100 microns, less than 50 microns, less than 30 microns, less than 25 microns, and less than 15 microns. The lamina is produced using the multi-phase implantation method described above.

[0040] It should be understood that the steps shown in FIGS. 5 and 6 are merely examples for illustration, and certain steps may be included or excluded as desired. Further, while a particular order of the steps is shown, this ordering is merely illustrative, and any suitable arrangement of the steps may be utilized without departing from the scope of the embodiments herein. Even further, the steps shown in FIGS. 5 and 6 may be interchanged, and the procedures may be partially or fully combined.

[0041] The components, arrangements, and techniques described herein, therefore, provide for enhancing the emissivity of a donor substrate, particularly sapphire lamina, for ion implantation. As noted above, applying the emissivity coating to a donor substrate permits higher radiation heat transfer rates while maintaining excellent substrate temperature uniformity. Consequently, higher beam currents are permitted, thus resulting in increased ion implanter throughput.

[0042] The foregoing description of preferred embodiments of the present disclosure has been presented for the purposes of illustration and description. It is not intended to be exhaustive or to limit the embodiments to the precise form disclosed. Modifications and variations are possible in light of the above teachings, or may be acquired from practice of the disclosed embodiments. For example, a method for increasing a heat transfer rate during ion implantation and a method for implanting an ion dosage into a donor substrate are contemplated, as well as a system for implanting an ion dosage into a donor substrate and a sapphire donor substrate. The embodiments were chosen and described in order to explain the principles of the invention and its practical application to enable one skilled in the art to utilize the invention in various embodiments and with various modifications as are suited to the particular use contemplated. It is intended that the scope of the invention be defined by the claims appended hereto, and their equivalents.

[0043] What is claimed is:

Claims

1. A method for increasing a heat transfer rate during ion implantation, the method comprising:

providing a donor substrate of crystalline material having a front surface and a back surface, wherein an ion beam directed toward the front surface of the donor substrate is configured to implant ions into the donor substrate; and

applying an emissivity coating to the back surface of the donor substrate that enhances an emissivity of the donor substrate.

2. The method as in claim 1, wherein the crystalline material is sapphire, silicon, silicon carbide, gallium nitride, gallium arsenide, aluminum nitride, diamond, or germanium.

3. The method as in claim 1, wherein the emissivity coating is applied to the donor substrate by sputtering, painting, plating, or evaporating onto the back surface of the donor substrate.

4. The method as in claim 1, wherein the emissivity coating comprises a carbonaceous substance, a graphitic substance, a metallic substance, or combinations thereof.

5. The method as in claim 1, wherein the emissivity coating comprises an electroless nickel compound or a black electroless nickel compound.

6. The method as in claim 1, wherein the emissivity coating is oxidized.

7. The method as in claim 1, wherein the emissivity coating enhances the emissivity of the donor substrate during a process in which the donor substrate is cooled by radiation.

8. A method of implanting an ion dosage into a donor substrate, the method comprising: providing a donor substrate of crystalline material having a front surface, a back surface, and an emissivity coating applied onto the back surface that enhances an emissivity of the donor substrate;

generating an ion beam directed toward the front surface of the donor substrate; and implanting an ion dosage into the donor substrate.

9. The method as in claim 8, wherein the crystalline material is sapphire, silicon, silicon carbide, gallium nitride, gallium arsenide, aluminum nitride, diamond, or germanium.

10. The method as in claim 8, wherein the emissivity coating is applied to the donor substrate by sputtering, painting, plating, or evaporating onto the back surface of the donor substrate.

11. The method as in claim 8, wherein the emissivity coating comprises a carbonaceous substance, a graphitic substance, a metallic substance, or combinations thereof.

12. The method as in claim 8, wherein the emissivity coating comprises an electroless nickel compound or a black electroless nickel compound.

13. The method as in claim 8, wherein the emissivity coating is oxidized.

14. The method as in claim 8, wherein the emissivity coating enhances the emissivity of the donor substrate during a process in which the donor substrate is cooled by radiation.

15. A system for implanting an ion dosage into a donor substrate, the system comprising: a housing configured to house a donor substrate of crystalline material having a front surface, a back surface, and an emissivity coating applied onto the back surface that enhances an emissivity of the donor substrate;

an ion beam generator configured to generate an ion beam directed toward the front surface of the donor substrate; and an ion beam controller configured to control the ion beam generation so as to implant ions into the donor substrate.

16. The system as in claim 15, wherein the crystalline material is sapphire, silicon, silicon carbide, gallium nitride, gallium arsenide, aluminum nitride, diamond, or germanium.

17. The system as in claim 15, wherein the emissivity coating is applied to the donor substrate by sputtering, painting, plating, or evaporating onto the back surface of the donor substrate.

18. The system as in claim 15, wherein the emissivity coating comprises a carbonaceous substance, a graphitic substance, a metallic substance, or combinations thereof.

19. The system as in claim 15, wherein the emissivity coating comprises an electroless nickel compound or a black electroless nickel compound.

20. The system as in claim 15, wherein the emissivity coating is oxidized.

21. The system as in claim 15, wherein the emissivity coating enhances the emissivity of the donor substrate during a process in which the donor substrate is cooled by radiation.

22. A sapphire donor substrate, comprising:

a donor substrate made of sapphire material having a front surface and a back surface; and

an emissivity coating applied onto the back surface that enhances an emissivity of the donor substrate.

23. The substrate as in claim 22, wherein the emissivity coating is applied to the donor substrate by sputtering, painting, plating, or evaporating to the back surface of the donor substrate.

24. The substrate as in claim 22, wherein the emissivity coating comprises a carbonaceous substance, a graphitic substance, a metallic substance, or combinations thereof.

25. The substrate as in claim 22, wherein the emissivity coating comprises an electroless nickel compound or a black electroless nickel compound.

26. The substrate as in claim 22, wherein the emissivity coating is oxidized.

27. The substrate as in claim 22, wherein the emissivity coating enhances the emissivity of the donor substrate during a process in which the donor substrate is cooled by radiation.

28. The substrate as in claim 22, further comprising a cleave plane within the donor body beneath the front surface.

29. The substrate as in claim 22, wherein the cleave plane comprises an implanted ion dosage.

30. The substrate as in claim 22, wherein the ion dosage comprises hydrogen ions, helium ions, or both.