Crystalline wafers and process for forming crystalline wafers

Abstract

A method for forming a crystalline wafer or film, such as a diamond wafer or film, is disclosed. Such a method may include the step of creating a damage layer on a seed wafer at a depth from the top surface of the seed wafer. The seed wafer may include a diamond crystalline structure. The method may further include the step of growing a diamond epitaxial layer on the top surface of the seed wafer through a chemical vapor deposition (CVD) process. The growth temperature of the CVD process may convert the damage layer into a graphitized interface between the seed wafer and the diamond epitaxial layer. The method may further include the step of applying light from a laser to the graphitized interface to separate the diamond epitaxial layer from the seed wafer and obtain the diamond wafer.

Description

Background Technology

[0001] Single-crystal diamond wafers can be grown using a chemical vapor deposition (CVD) process. Such a process can successfully grow relatively thick wafers (e.g., 10 mm). However, conventional slicing techniques, such as sawing, laser sawing, and / or etching, prove problematic. For example, conventional slicing techniques can result in significant cutting losses. Conventional etching techniques can be too time-consuming to be economically viable (e.g., an etching period of several days).

[0002] What is illustrated and / or described in connection with at least one of the drawings and more fully described in the claims is, among other things, a process comprising the steps of: creating a damaged layer under the upper surface of a seed wafer; annealing the damaged layer to form a graphitized interface under the upper surface of the seed wafer; and laser splitting the seed wafer along the graphitized interface to separate the diamond film or diamond wafer from the seed wafer. Such a technique may provide less cutting loss, may be more time-efficient, or may have other advantages over conventional techniques.

[0003] These and other advantages, aspects, and novel features of the present disclosure, as well as details of the exemplified embodiments of the present disclosure, will be more fully understood from the following description and drawings. Brief explanation of the drawing

[0004] The various features and advantages of the present disclosure can be more easily understood by referring to the following detailed description taken together with the accompanying drawings, and similar reference numerals indicate similar structural elements. FIG. 1 illustrates a flowchart of a process for forming a diamond wafer or a film from a seed wafer according to various embodiments of the present disclosure. Figure 2 provides cross-sectional views of a seed wafer at various stages of the process of Figure 1. FIG. 3 provides a perspective view of a seed wafer at various stages of the process of FIG. 1. Figure 4 illustrates the respective energy range, dosage range, and depth at the ion species and the illustrated maximum and minimum dosages. Figure 5 illustrates the respective energy ranges, dosage ranges, and damage in vacancy at the ion species and the maximum dose shown. Specific details for implementing the invention

[0005] The following discussion provides various examples of providing diamond wafers or films. Such examples are non-limiting, and the scope of the appended claims should not be limited to the specific examples disclosed. In the following discussion, the terms "examples" and "for instance" are non-limiting.

[0006] To illustrate general configurations and to avoid unnecessarily obscuring the present disclosure, descriptions and details of well-known features and techniques may be omitted. Additionally, elements in the drawings are not necessarily drawn to scale. For example, to help improve understanding of the examples discussed in the present disclosure, the dimensions of some elements in the drawings may be exaggerated compared to others. Identical reference numbers in different drawings indicate identical elements.

[0007] The term "and / or" means any one or more of the items in the list combined by "and / or". For example, "x and / or y" means any element of the set of three elements {(x), (y), (x, y)}. As another example, "x, y and / or z" means any element of the set of seven elements {(x), (y), (z), (x, y), (x, z), (y, z), (x, y, z)}.

[0008] The terms "comprise," "comprising," "include," and / or "including" are "open" terms that specify the existence of the specified feature but do not exclude the existence or addition of one or more other features.

[0009] Terms such as "first," "second," etc., may be used herein to describe various elements, and such elements should not be limited by these terms. These terms are used solely to distinguish one element from another. Accordingly, for example, a first element discussed in this disclosure may be referred to as a second element without departing from the teachings of this disclosure.

[0010] Unless otherwise specified, the term "coupled" may be used to describe two elements in direct contact with each other, or two elements connected indirectly by one or more other elements. For example, if element A is coupled to element B, element A may be in direct contact with element B, or may be connected indirectly to element B by an intermediate element C. Similarly, the terms "over" or "on" may be used to describe two elements in direct contact with each other, or two elements connected indirectly by one or more other elements.

[0011] Generally, aspects of the present disclosure relate to a process for forming a crystalline wafer or film. Such a process may include the steps of creating a damaged layer on a seed wafer at a depth from the top surface of the seed wafer, and forming a crystalline structure on the top surface of the seed wafer. The method further includes the step of applying light from a laser to the damaged layer to separate the formed crystalline structure from the seed wafer and obtain the wafer. More specifically, the seed wafer may include a diamond crystalline structure. The step of forming the crystalline structure may include growing a diamond epitaxial layer on the top surface of the seed wafer through a chemical vapor deposition (CVD) process. The growth temperature of the CVD process may convert the damaged layer into a graphitized interface between the seed wafer and the diamond epitaxial layer. Applying light from a laser may separate the diamond epitaxial layer from the seed wafer to obtain the diamond wafer.

[0012] Now, referring to FIGS. 1 through 3, a process (100) for forming a diamond wafer or film is illustrated. While the process (100) is specifically illustrated and described below in relation to forming a diamond wafer or film, the process (100) may be used to form a wafer or film of a crystalline material other than diamond. In step (110), a seed wafer (10) is prepared for ion implantation. The seed wafer (10) may include a seed wafer top surface (12), a seed wafer bottom surface (14), and a seed wafer side (16) between the seed wafer top surface (12) and the seed wafer bottom surface (14). In step (110), the seed wafer top surface (12) may be polished to remove surface defects in the diamond crystalline structure of the seed wafer (10).

[0013] In step (120), a damaged layer (20) may be created below the upper surface (12) of the seed wafer. To this end, ions (22) may be injected through the upper surface (12) of the seed wafer to a desired depth (D) in the seed wafer (10). Such injection may damage the diamond crystalline structure and create bonded vacities in the diamond crystalline structure of the seed wafer (10). Various ion species may be injected. In particular, hydrogen, helium, and / or carbon ions may be injected through the upper surface (12) of the seed wafer to a depth below the upper surface (12) of the seed wafer, depending on the ion species and the injection energy.

[0014] As shown in the table of FIG. 4, hydrogen ions can be injected using an injection energy in the range of 20 keV (kiloelectronvolt) to 525 keV, which corresponds to peak concentration injection depths between 0.1 μm (micron) and 3.0 μm into the diamond crystalline structure of the seed wafer (10), respectively. Similarly, helium ions can be injected using an injection energy in the range of 20 keV to 1220 keV, which corresponds to peak concentration injection depths between 0.2 μm and 2.0 μm into the diamond crystalline structure of the seed wafer (10), respectively. Additionally, carbon ions can be injected using an injection energy in the range of 80 keV to 1220 keV, which corresponds to peak concentration injection depths between 0.1 μm and 1.6 μm into the diamond crystalline structure of the seed wafer (10), respectively.

[0015] Figure 4 also provides a first graph of the concentration versus depth of hydrogen, helium, and carbon ion species at their respective maximum ion implantation energies and maximum doses listed in the table. Figure 4 also provides a second graph of the concentration versus depth of hydrogen, helium, and carbon ion species at their respective minimum ion implantation energies and minimum doses listed in the table. The graphs are based on simulation data.

[0016] As further illustrated in Fig. 5, the concentration of vacancy bonds at the injection depth depends on the injection dosage of various ion species. In particular, hydrogen ions are 1 e14 ions / cm² 2 and 1.2e17 ions / cm 2 It can be injected at a dosage in the range between. Helium ions are 1 e13 ions / cm 2 and 1.2e17 ions / cm 2 It can be injected at a dosage in the range between. Carbon ions are 1 e12 ions / cm² 2 and 2.0e16 ions / cm 2 It can be injected at a dosage range between these. The graph in Fig. 5 illustrates the vacancy versus injection depth for carbon ions and helium ions at their respective listed maximum injection energies and dosages. As shown, the injection energy and dosage can result in a peak vacancy of approximately 2.5e23 per cubic centimeter. Again, the graph is based on simulation data.

[0017] In step (130), the process (100) grows an epitaxial layer (30) on a seed wafer (10). To do this, the process (100) may use a crystal growth process suitable for growing an epitaxial layer (30) of diamond on the upper surface (12) of the seed wafer. Such growth may result in the formation of particles in which the crystalline structure aligns with the crystalline structure of the seed wafer (10) and continues the crystalline structure beyond the upper surface (12) of the seed wafer.

[0018] In various embodiments, a chemical vapor deposition (CVD) process may be used to grow the epitaxial layer (30). Such a CVD process may be performed at a growth temperature (e.g., 1100 to 1150 °C) sufficient to anneale the damaged layer (20) and convert the damaged layer (20) into graphite. Such conversion to graphite effectively provides a graphitized interface (24) between the diamond crystalline structure of the seed wafer (10) and the diamond crystalline structure of the epitaxial layer (30).

[0019] After forming the epitaxial layer (30) and the graphitized interface (24), the process (100) in step (140) can separate the epitaxial layer (30) from the seed wafer (10). To this end, the process (100) may include the step of focusing light emitted from the laser (50) onto the graphitized interface (24) to break the bonds of the graphitized interface (24) and separate the epitaxial layer (30) from the seed wafer (10). In various embodiments, the graphitized interface (24) provides an opaque layer to an otherwise transparent structure. Due to the opaque nature of the graphitized interface (24), the laser (50) can be absorbed by the graphitized interface (24) and can break the bonds of the graphitized interface (24). In this way, the effect of the laser (50) can be localized to the graphitized interface (24), thus avoiding further damage to the crystalline structure of the epitaxial layer (30) and / or seed wafer (10).

[0020] In step (150), the process (100) can output a new diamond wafer or film by completing the processing of the separated epitaxial layer (30). In particular, the process (100) can polish and / or etch the lower side of the separated epitaxial layer (30) to remove residues of the graphitized interface (24). Such polishing and / or etching can also remove and / or reduce defects along the graphitized interface (24).

[0021] As shown in FIGS. 2 and 3, the process (100) can be repeated, and the seed wafer (10) can be reused.

[0022] While the present disclosure includes references to specific examples, those skilled in the art will understand that various modifications may be made and equivalents substituted without departing from the scope of the present disclosure. Additionally, modifications to the disclosed examples may be made without departing from the scope of the present disclosure. Accordingly, the present disclosure is not limited to the disclosed examples but is intended to include all examples falling within the scope of the appended claims.

Claims

Claim 1 A method for forming a wafer comprises the steps of: forming a damaged layer on a seed wafer at a depth from the upper surface of the seed wafer; forming a crystalline structure on the upper surface of the seed wafer; and applying light from a laser to the damaged layer to separate the formed crystalline structure from the seed wafer and obtaining the wafer, wherein the step of forming the crystalline structure includes using a chemical vapor deposition (CVD) process to grow an epitaxial layer, and the growth temperature of the CVD process is such that the damaged layer is converted into graphite. Claim 2 A method for forming a wafer according to claim 1, wherein the growth temperature of the CVD process forms a damaged layer into a graphitized interface. Claim 3 A method for forming a wafer according to claim 1, wherein the step of creating the damage layer includes the step of implanting ions into the seed wafer through the upper surface of the seed wafer. Claim 4 A method for forming a wafer according to claim 1, wherein the step of creating the damage layer includes the step of injecting helium ions into the seed wafer through the upper surface of the seed wafer. Claim 5 A method for forming a wafer according to claim 1, wherein the step of creating the damage layer includes the step of injecting hydrogen ions into the seed wafer through the upper surface of the seed wafer. Claim 6 A method for forming a wafer according to claim 1, wherein the step of creating the damage layer includes the step of implanting carbon ions into the seed wafer through the upper surface of the seed wafer. Claim 7 A method for forming a wafer according to claim 1, wherein the growth temperature of the CVD process is annealing the damaged layer. Claim 8 A method for forming a wafer according to claim 1, comprising the step of removing the residue of the damaged layer from the wafer. Claim 9 A method for forming a wafer according to claim 1, comprising the step of polishing the lower surface of the wafer. Claim 10 A method for forming a wafer according to claim 1, comprising the step of etching the lower surface of the wafer. Claim 11 A method for forming a wafer according to claim 1, comprising the step of reusing the seed wafer to form another wafer after separating the wafer from the seed wafer. Claim 12 A method for forming a wafer according to claim 1, wherein the seed wafer comprises a diamond crystalline structure; and the wafer separated from the seed wafer comprises a diamond crystalline structure. Claim 13 A method for forming a diamond wafer, comprising the steps of: creating a damaged layer on a seed wafer at a depth from the upper surface of the seed wafer, wherein the seed wafer comprises a diamond crystalline structure; growing a diamond epitaxial layer on the upper surface of the seed wafer through a chemical vapor deposition (CVD) process, wherein the growth temperature of the CVD process converts the damaged layer into a graphitized interface; and applying light from a laser to the graphitized interface to separate the diamond epitaxial layer from the seed wafer and obtain the diamond wafer. Claim 14 A method for forming a diamond wafer according to claim 13, wherein the step of creating the damage layer comprises the step of implanting ions into the seed wafer through the upper surface of the seed wafer. Claim 15 A method for forming a diamond wafer according to claim 14, wherein the ions include at least one of helium, hydrogen, and carbon ions. Claim 16 A method for forming a diamond wafer according to claim 13, comprising the step of removing the residue of the graphitized interface from the diamond wafer. Claim 17 A method for forming a diamond wafer according to claim 13, comprising the step of polishing the lower surface of the diamond wafer. Claim 18 A method for forming a diamond wafer according to claim 13, comprising the step of etching the lower surface of the diamond wafer. Claim 19 delete Claim 20 delete

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