WO2016029072A1

WO2016029072A1 - Substrate-transporting ion beam exfoliation system

Info

Publication number: WO2016029072A1
Application number: PCT/US2015/046203
Authority: WO
Inventors: Adam Alexander BRAILOVE; Joseph Gillespie
Original assignee: Gtat Corporation
Priority date: 2014-08-22
Filing date: 2015-08-21
Publication date: 2016-02-25
Also published as: TW201608622A

Abstract

In one embodiment, a system for exfoliating a crystalline lamina from an implanted crystalline donor substrate comprises substrate supports attached to a transporting structure, where the supports are configured to support an implanted crystalline donor substrate by a vacuum (e.g., with an implanted surface in contact with the vacuum). The transporting structure is configured to sequentially transport the substrate supports from a loading station, through one or more heating modules and a cleaving module (where the crystalline lamina is thermally cleaved from the implanted crystalline donor substrate along a cleave plane while the lamina remains in contact with the vacuum), and then to an unloading station.

Description

SUBSTRATE-TRANSPORTING ION BEAM EXFOLIATION SYSTEM

CROSS-REFERENCE TO RELATED APPLICATION

The present application claims the benefit of U.S. Patent Application No. 62/040,558 filed August 22, 2014, which is incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention:

The present invention relates to a system for ion beam exfoliation, and, more particularly, to transporting substrates within an ion beam exfoliation system.

2. Description of the Related Art:

Ion implantation is a materials engineering process by which ions of a material are accelerated in an electrical field and impacted into a solid. 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 electrostatically accelerated to a high 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.

There are various uses for ion implantation, such as the introduction of dopants (e.g., boron, phosphorus or arsenic) into a semiconductor material such as silicon. Another use for ion implantation is for cleaving (exfoliating) thin sheets (lamina) of hard crystalline materials such as silicon, sapphire, etc. Generally, this process involves implanting light ions into the material 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.

The ion beam exfoliation process is often associated with various sensitivities, such as precise heating considerations, delicate lamina handling, and tightly managed quality control. However, current systems that manage these sensitivities are often low-throughput and cumbersome to manage, for example, requiring many different steps and/or transitions. For example, conventional systems are lengthy processes that result in cycles of heating and cooling, as well as up-and-down power usage.

SUMMARY OF THE INVENTION

The present invention relates to a system for ion beam exfoliation, and, more particularly, to transporting substrates within an ion beam exfoliation system. Specifically, in one

embodiment, a system for exfoliating a crystalline lamina from an implanted crystalline donor substrate comprises substrate supports attached to a transporting structure, where the supports are configured to support an implanted crystalline donor substrate by a vacuum. The transporting structure is configured to sequentially transport the substrate supports from a loading station, through one or more heating modules and a cleaving module, and then to an unloading station.

In one embodiment, the transporting structure is a rotating structure.

In one embodiment, the loading station is configured to position the implanted crystalline donor substrate on a respective substrate support with an implanted surface in contact with the vacuum.

In one embodiment, the one or more heating modules heat the implanted crystalline donor substrate supported on the respective substrate support, each heating module comprising a passage aperture providing access for the implanted crystalline donor substrate on the respective substrate support to pass into and through. In one embodiment, the cleaving module is configured to thermally cleave the crystalline lamina from the implanted crystalline donor substrate along the cleave plane forming a remaining donor substrate, while the lamina remains in contact with the vacuum. The cleaving module comprises a passage aperture providing access for the implanted crystalline donor substrate supported on the respective substrate support to pass into and egress for the crystalline lamina supported by that respective substrate support to pass through.

In one embodiment, the unloading station is configured to remove the crystalline lamina from the respective substrate support.

Further embodiments and details relating to the present invention are described below. 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

The embodiments herein may be better understood by referring to the following description in conjunction with the accompanying drawings in which like reference numerals indicate identically or functionally similar elements, of which:

FIG. 1 illustrates an example of ion implantation and exfoliation;

FIG. 2 illustrates an example of a substrate-transporting ion beam exfoliation system in accordance with one or more embodiments described herein;

FIG. 3 illustrates an example of a substrate support for use with a substrate-transporting ion beam exfoliation system in accordance with one or more embodiments described herein;

FIG. 4 illustrates an example of a heating module for use with a substrate-transporting ion beam exfoliation system in accordance with one or more embodiments described herein; FIG. 5 illustrates an example of shutters and heat shields for a heating module for use with a substrate-transporting ion beam exfoliation system in accordance with one or more embodiments described herein;

FIG. 6 illustrates an example of a resistance heater for use with a substrate-transporting ion beam exfoliation system in accordance with one or more embodiments described herein;

FIG. 7 illustrates an example of the substrate support holding a substrate from above for use with a substrate-transporting ion beam exfoliation system in accordance with one or more embodiments described herein;

FIG. 8 illustrates an example of a substrate support having top and bottom supporting surfaces for use with a substrate-transporting ion beam exfoliation system in accordance with one or more embodiments described herein;

FIG. 9 illustrates an example of a cleaving module with additional clamping devices for use with a substrate-transporting ion beam exfoliation system in accordance with one or more embodiments described herein;

FIG. 10 illustrates an example of a substrate temperature cycle according to a substrate- transporting ion beam exfoliation system in accordance with one or more embodiments described herein; and

FIG. 11 illustrates an example simplified procedure for exfoliating a crystalline lamina from an implanted crystalline donor substrate, particularly using a substrate-transporting ion beam exfoliation system in accordance with one or more embodiments described herein.

DETAILED DESCRIPTION OF THE INVENTION

The present disclosure is directed to a system for exfoliating a crystalline lamina from an implanted crystalline donor substrate. In general, with reference to FIG. 1, the implanted crystalline donor substrate is used for providing a thin crystalline layer and may be formed by implanting a cleave plane into a hard crystalline materials, such as silicon, sapphire, silicon carbide, gallium nitride, gallium arsenide, aluminum nitride, diamond, and germanium.

Generally, as shown, this process involves implanting light ions 65 into a donor body material 60, where they will stop below the surface in a layer, forming the implanted crystalline donor substrate, and the resulting material may then be heated (for example), causing the material above the implanted layer to cleave off or exfoliate in a sheet or lamina 10. Specifically, a donor body of crystalline material 60 can be provided having a top surface, where an ion dosage 65 (e.g., hydrogen ions, helium ions, or both) is implanted through the top surface of the donor body to form a cleave plane beneath the top surface, from which the crystalline lamina 10 may be exfoliated along the cleave plane, using the system described in more detail below.

Implantation conditions can be varied as needed to produce a particular implanted crystalline donor substrate desired for preparing a lamina (e.g., sapphire lamina) having targeted properties, such as thickness and strength. For example, the ion dosage may be any dosage between about 1.0 x 10 14 and 1.0 x 1018 ions/cm 2 , such as 0.5-3.0 x 1017 ions/cm 2. The dosage energy can also be varied, such as between about 500 keV to about 3 MeV. In some

embodiments, the ion implantation temperature may be maintained between about 200 and 950°C, such as between 300 and 800°C or between 550 and 750°C. In some embodiments, the implant temperature may be adjusted depending upon the specific type of material and the orientation of the donor body. Other implantation conditions that may be adjusted may include initial process parameters such as implant dose and the ratio of implanted ions (such as H/He ion ratio). In other embodiments, implant conditions may be optimized in combination with exfoliation conditions such as those discussed in more detail below, including exfoliation temperature, exfoliation susceptor vacuum level, heating rate and/or exfoliation pressure. By adjusting implantation and exfoliation conditions, the area of the resulting lamina that is substantially free of physical defects can be maximized. The resulting exfoliated layer may be further processed if needed, such as to produce smooth final surfaces.

According to the present invention, a system for exfoliating a crystalline lamina in accordance with one or more embodiments described herein generally comprises a transporting structure configured to transport one or more substrate supports or "holders" through a sequence of heating modules or "zones". For example, in one particular embodiment as illustrated in FIG. 2, the system 200 comprises a rotary-type furnace having a plurality of substrate holders 300 mounted on the periphery of a rotatable wheel as the transporting structure 210. That is, the transporting structure 210 in one embodiment is a rotating structure configured to rotate and sequentially transport the one or more substrate supports 300 through one or more heating modules.

The one or more substrate supports 300 (e.g., a plurality of substrate supports) may be attached to the transporting structure, such as by extending away from the transporting structure, and are configured to support at least one implanted crystalline donor substrate, preferably by a vacuum. As described above, the implanted crystalline donor substrate has a top surface, a bottom surface, and a cleave plane within the crystalline donor substrate beneath the top surface. The transporting structure may then sequentially transport the one or more substrate supports through various process zones where the implanted crystalline donor substrate is heated and exfoliation occurs. For example, the implanted donor may be secured by vacuum to the substrate support at the loading station, and transported from there through one or more heating modules and/or a cleaving module, and to an unloading station where the lamina and the donor may be removed from the substrate support. A plurality of heating zones may comprise heater modules, such as wedge-shaped heater modules, that allow some control over the temperature profile seen by each substrate.

Illustratively, the system 200 comprises a loading station 220 (e.g., an un-heated station or location positioned either outside of or in advance of any heating modules) configured to position the implanted crystalline donor substrate with the "top" or implanted surface supported on a respective substrate support 300 by a vacuum. That is, the implanted/top surface is in contact with, and thus held in position by, the vacuum. In one embodiment, the loading station 220 is also the unloading station, where both loading of implanted substrates and un-loading of cleaved lamina may occur (e.g., automated or manually).

In one embodiment, to assist in bringing an implanted donor from room temperature to the temperature needed to cleave a lamina, one or more pre-heating modules 230 may be used (e.g., at 650 °C), which may be sequentially followed by a stabilizing module 240 (e.g., at 700 °C) prior to the implanted donor substrate entering a cleaving module 250 (e.g., at 850 °C). Within the cleaving module 250, the crystalline lamina may be exfoliated as described above, and then annealed within an annealing module 260 (e.g., at 1200 °C). Note that the annealing module may require a higher temperature, e.g., 1400 °C, to drive the cleaved lamina rapidly to the desired 1200 °C annealing temperature of the crystalline lamina.

Optional cooling modules/stations 270 and 280 may also be provided to rapidly cool the substrate holders prior to the unloading station. In one embodiment, the one or more cooling modules comprise air jets, though other configurations are possible.

The unloading station may be configured to remove the crystalline lamina from the respective substrate support 300. In one embodiment as mentioned above, the loading station 220 is the same as the unloading station, where the cleaved crystalline lamina is removed, and a new donor substrate is placed on that substrate. In this embodiment, as described further below, an additional station 290 may be used to remove the remaining donor substrate, which may be re-implanted for further processing. In an alternative embodiment, however, the separate station 290 may comprise an unloading station, that is, where the unloading station and loading station are separate locations within the sequential processing path of the system 200.

In this configuration, the transporting structure 210 may either be sequentially indexed (i.e., periods of movement and stationary positioning), such as every 30 seconds (e.g., with 1- second index time), or else may be configured for continuous motion (e.g., 30 seconds within each module/station, but moving). Notably, at this pace (e.g., 30 seconds per lamina), the system 200 may exfoliate approximately 120 lamina in an hour (which meets or even exceeds current implanter throughput). In general, any suitable speed may be used based on the desired heating conditions and properties, and the times and temperatures shown herein are merely for illustration, and are not meant to limit the scope of the embodiments herein.

Also, while the embodiment of the system 200 is shown as a circular and rotating design (e.g., a carousel), other suitable shapes and configurations of sequential transport may be used in accordance with the techniques herein, such as linear systems, curves other than circular (e.g., a "racetrack" design).

With reference to FIG. 3, each substrate support 300 may preferably comprise a vacuum chuck for securing the lamina, and may provide a continuous vacuum throughout the processing sequence described above (with the exception of the unloading station in which vacuum may be suspended to remove the exfoliated lamina). Illustratively, the support 300 comprises a vacuum chuck having a supporting surface 310 that includes a series of vacuum holes 320 (e.g., micropores) connected to a vacuum source through the arm 330. The source may be located, for example, through the attached transport structure. The arm 330 that attaches the support surface 310 to the transport structure 210 includes a heat shield 340 that allows for thermal isolation of the chuck (i.e., such that each of the substrate supports are thermally isolated from each other), and can be made of a quartz or other suitable material.

The surface (e.g., vacuum chuck) 310 of the substrate support 300 may be made of a heat-resistant ceramic, such as aluminum nitride (AIN), that preferably has a substantially similar coefficients of thermal expansion (CTE) as the crystalline donor substrate, and is designed to allow the implanted face of the substrate to be secured against the vacuum chuck surface, thereby minimizing possible fracture of the delicate lamina. For instance, the surface may be polished and may have good lateral temperature uniformity, and the vacuum holes 320 may be laser drilled, and may have a size that is less than 10 um to provide sufficient suction while not deforming the lamina. As shown, in one embodiment, the vacuum chuck surface may be generally completely covered by the holes 320, though other arrangements, patterns, and configurations are possible. As can be seen, the surface 310 is smooth, and there are no pockets or lift pins, allowing for handling a correspondingly smooth lamina surface. Notably, while in one embodiment, a single implanted crystalline donor substrate may be placed on each substrate support 300, in another embodiment the supports and surface 310 may each individually support a plurality of implanted crystalline donor substrates by the vacuum.

Note further that securing the lamina directly to the surface 310 can occur in the case of bonding after exfoliation (BAE), in which the resulting exfoliated lamina is separately bonded to a carrier substrate as well as in the case of bonding before exfoliation (BBE) where the implanted donor substrate is bonded to another material prior to formation of the desired lamina. For BBE, the vacuum chuck may secure that bonded material, accordingly. For example, the top surface of the crystalline donor substrate may be bonded (temporarily or permanently) before cleaving to a handle substrate, and the substrate support may be configured to support the implanted crystalline donor substrate by the handle substrate. Moreover, while the substrate supports 300 are generally described in terms of a vacuum, the pressure applied to the substrate may be negative, positive, or zero (e.g., a controllable friction pressure of -15 psi to +15 psi). For example, the unloading station may be configured to suspend the vacuum while the crystalline lamina is removed, or else may provide a positive pressure to assist the removal.

FIG. 4 illustrates an example heating module 400 (shown in cutaway) that may be used for any of the heating modules mentioned above. In particular, in addition to heating elements such as resistance coils 410 on the inner walls 420 of the heater, the illustrative heating module 400 may generally consist of a "clamshell" shape, where a portion is designed as a passage aperture 430 providing access for the support substrate's arm 330. Notice from the cutaway view in FIG. 4 that the heat shield 340 extending from the support substrate substantially covers at least a portion of the passage aperture from the inside of the heater when a corresponding substrate support, thus preventing escape of heat (or radiation) from the heater module 400 while the support substrate is located within.

Additionally, and with reference also to FIG. 5 showing the outside of the heater module 400, the passage aperture 430 also provides access for the implanted crystalline donor substrate on the respective substrate support to pass into and through. In other words, these generally narrow openings are provided in the walls of each heating zone to allow the substrates (e.g., a wafer) on their respective substrate supports to pass through the heating zone(s). A similar configuration can be used for the cleaving module. In particular, for the cleaving module 250, which is configured to thermally cleave the crystalline lamina from the implanted crystalline donor substrate along the cleave plane to form a remaining donor substrate, the lamina remains in contact with the vacuum on the support 300, and the cleaving module's passage aperture 430 thus provides access for the implanted crystalline donor substrate supported on the respective substrate support to pass into the cleaving module, as well as providing egress for at least the crystalline lamina supported by that respective substrate support to pass through. (Cleaving module options are further described below.) The same may be true for the annealing module 260, which may have a passage aperture 430 that provides access for at least the crystalline lamina on a respective substrate support to pass into and through.

As also shown in FIG. 5, the system may further comprise insulating shutters between heaters that are open during transition/indexing of the substrate supports. That is, an ingress shutter 550 and an egress shutter 555 may be located on one or more of the heating modules 400, and are configured to close over at least a portion of the passage aperture 430 when the transporting structure 210 is not transporting the substrate supports, and to conversely open when the transporting structure is transporting the one or more substrate supports. Note that though shown separately on one heating module 400 in FIG. 5, an egress shutter of a particular heating module may also be an ingress shutter of a subsequent heating module, i.e., two adjacent heating modules may share a single shutter. Also, in one embodiment, the ingress shutter 550 and egress shutter 555 of a particular heating module 400 can be a single structure, which is configured to cover both sides (ingress and egress) of the heating module. In this particular embodiment, it is also possible to include a wraparound or "horseshoe" shaped shutter that also covers a portion of the small gap (the "clamshell opening") meant for the substrate support's arm 330 on the wall of the heating module facing the transporting structure 210.

Note that the one or more heating modules 400 can be generally wedge-shaped, to allow for a compact design when used with a carousel-type rotating transporting structure 210.

However, other embodiments may provide for differently shaped heating modules, accordingly.

Optionally, an inert purge gas such as nitrogen (N₂) may be supplied to the heating zones (e.g., provided by an inert gas purge apparatus) to prevent oxidation of any oxidizable parts (e.g., as a protective gas blanket). Also, the support substrates and interior components of the one or more heating modules and the cleaving module may be constructed of non-oxidizing material, such as high temperature ceramics. Note further that the inner walls 420 of at least some of the heating modules or the cleaving module may be constructed of non-particle- shedding material, such as quartz, ceramics, and silicon carbide. That is, the walls of the heaters may be lined (all or a portion of the inner walls) to prevent the heater walls from shedding particles on the substrates.

In one embodiment, as mentioned above, one or more of the heating modules 400 may comprise a resistance heater as the heating elements. For instance, an example resistance heater may have resistance coils 410 configured as shown in FIG. 6, where six zones (zones 1-6), e.g., 500W each, may be arranged in an overlapping or crossing pattern, such as zones 1-3 of a top surface of the heating module being transposed perpendicularly to zones 4-6 of a bottom surface of the heating module. Other suitable heating element arrangements are possible within the heating modules 400, and each heating module may be designed differently to achieve the desired heating result. As mentioned herein, some (e.g., all) of the one or more heating modules 400 may be maintained in a steady-state while the transporting structure transports the one or more substrate supports into and through them. That is, the heating elements may be powered to a single heat output and kept there, while the amount of the heat transferred to the substrate material is varied by the combination of the steady- state heating temperature within the module, and the length of time the substrate is kept within the module.

Note that while resistance heaters are generally shown and described, other types of heaters or heating elements may be used, such as lamp-heaters. In another alternative embodiment, at least the cleaving module may comprise a microwave heater. For instance, exfoliation may be achieved within the cleaving module 250 by microwave irradiation, which can effectively be used to produce exfoliated lamina at considerably lower temperatures without heating the implanted layer or subjecting a bond between a backing or handle substrate and the donor body surface to de -bonding temperatures. In this embodiment, pre-heating and stabilizing modules may not be necessary.

As generally shown above, the one or more substrate supports are configured to support the top (implanted) surface of the implanted crystalline donor substrate from beneath the top surface via gravity and the vacuum. That is, the donor material 60 may rest on top of the support substrate, and the lamina 10 would be left on the support substrate after cleaving, requiring removal of the remaining donor material 60 from above the lamina. However, in one

embodiment, such as shown in FIG. 7, the one or more substrate supports may instead be configured to support the top (implanted) surface of the crystalline donor substrate from above the top surface via the vacuum. In other words, in one embodiment, the substrate is suspended by a downward facing vacuum chuck 300 (on surface 310) such that when the donor 60 is cleaved from the lamina 10, the donor falls down and away from the lamina minimizing risk to the lamina from the donor movement. The donor may be captured by a capture mechanism 710 within the cleaving module configured to receive the remaining crystalline donor substrate 60 free-falling after thermal cleaving. For example, in one embodiment, the capture mechanism may be on an adjacent portion of the substrate holder (such as a set of fingers) and would thereby be moved through the process zones along with the lamina until the point of unloading. In another embodiment, the capture mechanism 710 may be specifically located within the cleave module only, such that the freed donor may fall free of the lamina and chuck and be collected and removed from the cleaving module 250 via a separate slot and/or mechanism in that zone (i.e., the cleaving module comprises a cavity to receive the remaining crystalline donor substrate after thermal cleaving). Other embodiments and configurations for separating the lamina from the donor are possible in accordance with the techniques here, such as turning a substrate support over to allow the donor to drop, etc.

In another embodiment, such as shown in FIG. 8, a substrate support 300 may comprise a first surface 310b configured to support a first surface of the crystalline donor substrate from beneath the first surface via gravity and the vacuum and a second surface 310a configured to support a second surface of the crystalline donor substrate from above the second surface via the vacuum. Said differently, this embodiment uses a second vacuum chuck in contact with the donor surface (non-implanted surface) of the donor to lift and hold the donor away from the lamina, when cleaving occurs. (In one configuration, the first surface of the crystalline donor substrate is the top implanted surface and the second surface of the crystalline donor substrate is the bottom non-implanted surface. In another "flipped" configuration, the first surface of the crystalline donor substrate is the bottom surface and the second surface of the crystalline donor substrate is the top surface). In this embodiment, the two vacuum chucks 310a and 310b "sandwich" the implanted donor (with a handle, if applicable). Controllable compression force may be applied to the sandwich to stabilize the cleaving process and light tension (separation force) may also be applied to gently separate the two portions when cleaving occurs, i.e., the separation forces provide a separation gap between the crystalline lamina 10 and the remaining donor substrate 60 after thermal cleaving. Note that this "secondary" support setup may be present only within the cleaving module to support the remaining crystalline donor substrate 60 after thermal cleaving. Regardless of the particular configuration, the passage aperture 430 of the cleaving module 250 may be configured to provide egress for the remaining crystalline donor substrate 60, whether supported independently by the secondary substrate support or else when the remaining donor substrate and the crystalline lamina are separated by only a slight gap. Note that the view in FIG. 8 is simplified and is not meant to limit the scope of the embodiments herein. For instance, in addition to scale differences between the chucks 310a and 310b, while two arms are shown, a single arm may be used for both the chucks 310a and 310b. Further, a single heat shield 340 or individual heat shields may also be present.

In still another embodiment, as shown in FIG. 9, a clamping device 910/920 may be located within the cleaving module 250 to provide compressive force to both the top and bottom surfaces of the crystalline donor substrate during cleaving. For instance, ceramic jaws may prevent the donor from moving with a controllable clamping force from top and bottom clamping components 910 and 920, respectively. In one embodiment, one of the clamping components (e.g., the top 910) may be capable of vacuum suction or air bearing pressure, and may be configured to assist in the removal of the remaining donor 60.

Advantageously, the techniques described herein provide a substrate-transporting ion beam exfoliation system. In particular, the systems described herein provide a low-cost, simple, reliable, high-throughput system with a controllable temperature profile during a "pipelined" exfoliation process, while allowing direct mechanical service access to each substrate for vacuum chucking, temperature measurement, etc. Moreover, the system is flexible, where the number of substrate supports and the number and/or type of heating (or cooling) modules can be adjusted based on desired output and on refinement of exfoliation techniques and practices over time. Further, the system has a lower heated mass than many conventional systems and also a lower level of power consumption.

In addition, the system herein can maintain operation of the heating modules at substantially steady-state, while still achieving the desired heating effect on the donor substrate and cleaved lamina. For instance, with reference to FIG. 10, a graph is shown illustrating the example temperature profile of the donor substrate and lamina as it passes through the illustrative sequence outlined above, while each corresponding module/station is kept in substantially steady-state. That is, by keeping each module at steady state and merely passing the substrate supports through the various stages/stations, the pre-heat stage (pre-heating module 230) may quickly bring the donor temperature up from room temperature to 600°C, and the stabilize phase (stabilizing heater 240) keeps the substrate at a stable temperature, until entering the cleaving module 250 where the temperature can be raised toward 850°C, passing the exfoliation ("exfo") temperature of the lamina. The resulting exfoliated lamina can continue the sequential transport into an annealing module 250, which can then quickly raise the temperature of at least the exfoliated lamina to 1200°C, and then cooling stations "cool 1" (270) and "cool 2" (280) may bring the temperature of the lamina back down to handling temperatures at different rates.

FIG. 11 illustrates an example simplified procedure 1100 for exfoliating a crystalline lamina from an implanted crystalline donor substrate, particularly using a substrate-transporting ion beam exfoliation system in accordance with one or more embodiments described herein. The procedure 1100 may start at step 1105, and continues to step 1110, where, as described in greater detail above, an implanted crystalline donor substrate is placed, at a loading station 220, on a substrate support 300 that is attached to a transporting structure 210 and configured to support at least one implanted crystalline donor substrate by a vacuum, the implanted crystalline donor substrate comprising a top surface, a bottom surface, and a cleave plane within the crystalline donor substrate beneath the top surface, the top surface placed in contact with the vacuum. As mentioned above, the substrate support 300 may be configured to support the donor substrate from above or beneath, or both. In steps 1115-1125, the transporting structure 210 sequentially transports the attached substrate supports 300 (that are supporting the implanted crystalline donor substrate) through one or more heating modules and a cleaving module, which are configured to heat the implanted crystalline donor substrate supported on the substrate support. Note that pressure of the vacuum may be controlled for individual substrate supports according to the sequential indexing, and/or a continuous vacuum may be maintained while transporting the substrate support (other than at the unloading station).

Specifically, in step 1115, the sequential transport may pass the substrate support (and supported donor substrate) through a pre-heating module 230, and then in step 1120 through a stabilizing module 240 prior to entering a cleaving module 240 in step 1125, which is configured to thermally cleave the crystalline lamina from the implanted crystalline donor substrate along the cleave plane and forming a remaining donor substrate, the lamina remaining in contact with the vacuum. Notably, in step 1125, first and second surfaces of the substrate supports or else clamping mechanisms may provide compressive forces and separation forces to the respective surfaces of the crystalline donor substrate. In step 1130, the transporting structure may also pass the substrate support through an annealing module 260 to anneal the crystalline lamina. Note that at least one of the heating modules or cleaving module may be maintained in a steady-state while the transporting structure transports the one or more substrate supports. As also described above, an ingress shutter 550 and an egress shutter 555 on each of the one or more heating modules and cleaving module may be closed over at least a portion of the passage aperture when the transporting structure is not transporting (or while the support is within the corresponding heating module, such as in continuous motion mode), while otherwise opening the ingress shutter and the egress shutter on each of the one or more heating modules and cleaving module when the transporting structure is transporting the substrate supports, accordingly.

In addition, as mentioned above, in step 1135 the system 200 may also pass the substrate supports through one or more cooling modules 270/280 sequentially prior to transporting the crystalline lamina supported by the substrate support to an unloading station 290 (or 220) in step 1140. In step 1140, the crystalline lamina may be removed from the substrate support (e.g., suspending the vacuum at the unloading station while the crystalline lamina is removed).

The procedure 1100 may then end in step 1145. Though this ends the procedure 1100 for one donor/lamina (e.g., one particular substrate support 300), the process essentially repeats at this point for another donor/lamina using that same substrate support. Moreover, it should be noted that while certain steps within procedure 1100 may be optional as described above, the steps shown in FIG. 11 are merely examples for illustration, and certain other 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.

Note that the present invention may be used to prepare a cover plate of an electronic device. In a specific embodiment, the method comprises the steps of providing a donor body, such as sapphire, implanting through the top surface of the donor body with an ion dosage to form a cleave plane beneath the top surface, exfoliating the layer from the donor body along the cleave plane using the system described above, and forming the cover plate comprising this layer, which has a thickness of 10 to 150 microns. Preferably, the ion dosage comprises hydrogen or helium ions.

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.

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.

Various methods and materials have been used in order to increase the durability of the display windows of mobile electronic devices. For example, polymeric coatings or layers can be applied to the touch screen surface in order to provide a barrier against degradation. However, such layers can interfere with the visual clarity of the underlying electronic display as well as interfere with the touch screen sensitivity. Furthermore, as the coating materials are often also soft, they can themselves become easily damaged, requiring periodic replacement or limiting the lifetime of the device.

Another common approach is to use more highly chemically and scratch resistant materials as the outer surface of the display window. For example, touch sensitive screens of some mobile devices may include a layer of chemically- strengthened alkali aluminosilicate glass, with potassium ions replacing sodium ions for enhanced hardness, such as the material referred to as "gorilla glass" available from Corning. However, even this type of glass can be scratched by many harder materials, and, further, as a glass, is prone to brittle failure or shattering.

Sapphire has also been suggested and used as a material for either the outer layer of the display assembly or as a separate protective sheet to be applied over the display window. However, sapphire is relatively expensive, particularly at the currently available thicknesses, and is not readily available as an ultrathin layer.

Accordingly, use of the techniques herein may provide be used for the exfoliation of one or more crystalline lamina (such as sapphire) having a thickness of less than 150 microns, such as less than 50 microns, less than 30 microns, less than 25 microns, and less than 15 microns. The foregoing description of preferred embodiments of the present invention has been presented for the purposes of illustration and description. It is not intended to be exhaustive or to limit the invention to the precise form disclosed. Modifications and variations are possible in light of the above teachings, or may be acquired from practice of the invention. 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. For example, while a certain configuration and/or shape of the components herein, other particular configurations and/or shapes may be used without departing from the scope of the systems and techniques described herein. It is thus intended that the scope of the invention be defined by the claims appended hereto, and their equivalents.

Claims

CLAIMS What is claimed is:

1. A system for exfoliating a crystalline lamina from an implanted crystalline donor substrate, the system comprising: a transporting structure; one or more substrate supports attached to the transporting structure and configured to support at least one implanted crystalline donor substrate by a vacuum, the implanted crystalline donor substrate comprising a top surface, a bottom surface, and a cleave plane within the implanted crystalline donor substrate beneath the top surface; a loading station configured to position the implanted crystalline donor substrate on a respective substrate support, the top surface in contact with the vacuum; one or more heating modules configured to heat the implanted crystalline donor substrate supported on the respective substrate support, each heating module comprising a passage aperture providing access for the implanted crystalline donor substrate on the respective substrate support to pass into and through; a cleaving module configured to thermally cleave the crystalline lamina from the implanted crystalline donor substrate along the cleave plane and forming a remaining donor substrate, the lamina remaining in contact with the vacuum and the cleaving module comprising a passage aperture providing access for the implanted crystalline donor substrate supported on the respective substrate support to pass into and egress for the crystalline lamina supported by that respective substrate support to pass through; and an unloading station configured to remove the crystalline lamina from the respective substrate support, wherein the transporting structure is configured to sequentially transport the one or more substrate supports from the loading station, through the one or more heating modules and the cleaving module, and to the unloading station.

2. The system as in claim 1, wherein the vacuum is a continuous vacuum.

3. The system as in claim 1, wherein the substrate support is attached to extend away from the transporting structure.

4. The system as in claim 1, wherein the transporting structure is a rotating structure configured to sequentially transport the one or more substrate supports by rotating.

5. The system as in claim 1, comprising a plurality of substrate supports.

6. The system as in claim 5, wherein the plurality of substrate supports are thermally isolated from each other.

7. The system as in claim 1, wherein the one or more substrate supports are configured to individually support a plurality of implanted crystalline donor substrates by the vacuum.

8. The system as in claim 1, wherein the one or more heating modules comprise a preheating module.

9. The system as in claim 8, wherein the one or more heating modules comprise a stabilizing module sequentially after the pre-heating module and before the cleaving module.

10. The system as in claim 1, further comprising: an annealing module sequentially after the cleaving module and before the unloading station, the annealing module configured to anneal the crystalline lamina, the annealing module comprising a passage aperture providing access for the crystalline lamina on a respective substrate support to pass into and through.

11. The system as in claim 1, further comprising: an ingress shutter and an egress shutter on each of the one or more heating modules and cleaving module, the ingress and egress shutters configured to close over at least a portion of the passage aperture when the transporting structure is not transporting the one or more substrate supports, and to open when the transporting structure is transporting the one or more substrate supports.

12. The system as in claim 11, wherein an egress shutter of a particular heating module is also an ingress shutter of a subsequent heating module or cleaving module.

13. The system as in claim 11, wherein an ingress shutter and an egress shutter of a particular heating module or cleaving module are a single structure, the single structure also configured to cover at least a portion of the passage aperture when closed.

14. The system as in claim 1, further comprising: a heat shield extending from each of the one or more substrate supports and configured to cover at least a portion of the passage aperture when a corresponding substrate support is located within a respective heating module or the cleaving module.

15. The system as in claim 1, further comprising: one or more cooling modules sequentially prior to the unloading station.

16. The system as in claim 15, wherein the one or more cooling modules comprise air jets.

17. The system as in claim 1, wherein the one or more substrate supports are configured to support the top surface of the implanted crystalline donor substrate from above the top surface via the vacuum.

18. The system as in claim 1, wherein the one or more substrate supports are configured to support the top surface of the implanted crystalline donor substrate from beneath the top surface via gravity and the vacuum.

19. The system as in claim 18, further comprising: a secondary support at least within the cleaving module configured to support the remaining crystalline donor substrate after thermal cleaving.

20. The system as in claim 19, wherein the passage aperture of the cleaving module provides egress for the remaining crystalline donor substrate supported by the secondary substrate support.

21. The system as in claim 18, further comprising: a capture mechanism within the cleaving module configured to receive the remaining crystalline donor substrate free-falling after thermal cleaving.

22. The system as in claim 18, wherein the cleaving module further comprises a cavity to receive the remaining crystalline donor substrate after thermal cleaving.

23. The system as in claim 1, wherein the one or more substrate supports comprise: a first surface configured to support a first surface of the implanted crystalline donor substrate from beneath the first surface via gravity and the vacuum; and a second surface configured to support a second surface of the implanted crystalline donor substrate from above the second surface via the vacuum.

24. The system as in claim 23, wherein the first and second surfaces of the one or more substrate supports are further configured to provide compressive forces and separation forces to the first and second surfaces of the implanted crystalline donor substrate, respectively.

25. The system as in claim 24, wherein the separation forces provide a separation gap between the crystalline lamina and the remaining donor substrate after thermal cleaving, and wherein the passage aperture of the cleaving module provides egress for the remaining donor substrate and the crystalline lamina separated by the gap.

26. The system as in claim 23, wherein the first surface of the implanted crystalline donor substrate is the top surface and wherein the second surface of the crystalline donor substrate is the bottom surface.

27. The system as in claim 23, wherein the first surface of the implanted crystalline donor substrate is the bottom surface and wherein the second surface of the implanted crystalline donor substrate is the top surface.

28. The system as in claim 1, further comprising: a clamping device located within the cleaving module to provide compressive force to both the top and bottom surfaces of the implanted crystalline donor substrate during cleaving.

29. The system as in claim 1, wherein the unloading station is configured to suspend the vacuum while the crystalline lamina is removed.

30. The system as in claim 1, further comprising: an inert gas purge apparatus configured to provide inert gas to at least one of the one or more heating modules or the cleaving module.

31. The system as in claim 1, wherein the one or more support substrates and interior components of the one or more heating modules and the cleaving module are constructed of non- oxidizing material.

32. The system as in claim 1, further comprising: interior walls of at least one of the one or more heating modules or the cleaving module that are constructed of non-particle-shedding material.

33. The system as in claim 32, wherein the non-particle- shedding material is selected from a group consisting of: quartz, ceramics, and silicon carbide.

34. The system as in claim 1, wherein the crystalline donor substrate and one or more substrate supports have substantially similar coefficients of thermal expansion.

35. The system as in claim 1, wherein the implanted crystalline donor substrate is selected from a group consisting of: sapphire, silicon, silicon carbide, gallium nitride, gallium arsenide, aluminum nitride, diamond, and germanium.

36. The system as in claim 1, wherein the one or more heating modules and the cleaving module are wedge-shaped.

37. The system as in claim 1, wherein at least one of the one or more heating modules or cleaving module comprises a resistance heater.

38. The system as in claim 1, wherein the cleaving module comprises a microwave heater.

39. The system as in claim 1, wherein at least one of the one or more heating modules or cleaving module is maintained in a steady-state while the transporting structure transports the one or more substrate supports.

40. The system as in claim 1, wherein the top surface of the implanted crystalline donor substrate is bonded before cleaving to a handle substrate, and wherein the one or more substrate supports are configured to support the implanted crystalline donor substrate by the handle substrate.

41. A method for exfoliating a crystalline lamina from an implanted crystalline donor substrate, the method comprising: placing, at a loading station, an implanted crystalline donor substrate on a substrate support that is attached to a transporting structure and configured to support at least one implanted crystalline donor substrate by a vacuum, the implanted crystalline donor substrate comprising a top surface, a bottom surface, and a cleave plane within the implanted crystalline donor substrate beneath the top surface, the top surface placed in contact with the vacuum; sequentially transporting the substrate support attached to the transporting structure and supporting the implanted crystalline donor substrate through one or more heating modules and a cleaving module, wherein the one or more heating modules are configured to heat the implanted crystalline donor substrate supported on the substrate support, each heating module comprising a passage aperture providing access for the implanted crystalline donor substrate on the substrate support to pass into and through, and wherein the cleaving module is configured to thermally cleave the crystalline lamina from the implanted crystalline donor substrate along the cleave plane and forming a remaining donor substrate, the lamina remaining in contact with the vacuum and the cleaving module comprising a passage aperture providing access for the implanted crystalline donor substrate supported on the substrate support to pass into and egress for the crystalline lamina supported by that substrate support to pass through; and sequentially transporting the crystalline lamina supported by the substrate support attached to the transporting structure to an unloading station.

42. The method as in claim 41, wherein the implanted crystalline donor substrate is placed on a particular substrate support of one or more substrate supports attached to the transporting structure.

43. The method as in claim 42, further comprising: controlling pressure of the vacuum for individual substrate supports of the one or more substrate supports according to the sequential transporting.

44. The method as in claim 41, wherein the transporting structure is a rotating structure configured to sequentially transport the substrate support by rotating.

45. The method as in claim 41, wherein the one or more heating modules comprise a preheating module.

46. The method as in claim 45, wherein the one or more heating modules comprise a stabilizing module sequentially after the pre-heating module and before the cleaving module.

47. The method as in claim 41, further comprising: sequentially transporting the substrate support to pass through an annealing module sequentially after the cleaving module and before the unloading station, the annealing module configured to anneal the crystalline lamina, the annealing module comprising a passage aperture providing access for the crystalline lamina on the substrate support to pass into and through.

48. The method as in claim 41, further comprising: closing an ingress shutter and an egress shutter on each of the one or more heating modules and cleaving module over at least a portion of the passage aperture when the transporting structure is not transporting the substrate support; and opening the ingress shutter and the egress shutter on each of the one or more heating modules and cleaving module when the transporting structure is transporting the substrate support.

49. The method as in claim 48, wherein an egress shutter of a particular heating module is also an ingress shutter of a subsequent heating module or cleaving module.

50. The method as in claim 48, wherein an ingress shutter and an egress shutter of a particular heating module or cleaving module are a single structure, the single structure also configured to cover at least a portion of the passage aperture when closed.

51. The method as in claim 41, further comprising: sequentially transporting the substrate support to pass through one or more cooling modules sequentially prior to the unloading station.

52. The method as in claim 41, wherein the substrate support comprises: a first surface configured to support a first surface of the implanted crystalline donor substrate from beneath the first surface via gravity and the vacuum; and a second surface configured to support a second surface of the implanted crystalline donor substrate from above the second surface via the vacuum.

53. The method as in claim 52, further comprising: providing, by the first and second surfaces of the substrate supports, compressive forces and separation forces to the first and second surfaces of the implanted crystalline donor substrate, respectively.

54. The method as in claim 41, further comprising: maintaining a continuous vacuum while transporting the substrate support.

55. The method as in claim 41, further comprising: suspending the vacuum at the unloading station and removing the crystalline lamina from the substrate support at the unloading station.

56. The method as in claim 41, further comprising: maintaining at least one of the one or more heating modules or cleaving module in a steady-state while the transporting structure transports the one or more substrate supports.