Board Retainer

Abstract

1. A retainer for holding a substrate during chemical vapor deposition, CVD, processing, the retainer comprising: - a first surface configured to form a counter surface for the exposed surface of the substrate; - a second surface arranged substantially parallel to the counter surface and at a distance d from the counter surface, the second surface being arranged to support a substrate; a third surface disposed at an angle relative to the second surface, the third surface forming an edge that constrains movement of the substrate; and A retainer having:

Description

[Technical Field]

[0001] The present invention relates to a substrate retainer, particularly a substrate retainer for supporting a substrate during chemical vapor deposition, CVD, processing, and a method for manufacturing such a retainer. The retainer is particularly suitable for low-pressure chemical vapor deposition, LP-CVD, of thin graphene films. [Background technology]

[0002]

[0002] Graphene has been ascribed particular properties, such as electrical and / or chemical properties, that make it extremely interesting for a wide range of applications, including electronics, lasers, biosensors, photonic switches, light-emitting diodes (LEDs), infrared sensors, protective coatings, hydrogen storage, and energy storage.

[0003] Chemical vapor deposition (CVD) has traditionally been used to produce graphene layers and thin films. In such known CVD processes, the surface of a metal substrate is exposed to a carbon-containing precursor gas, such as methane, ethane, ethylene, or benzene, which results in the adsorption of precursor gas molecules on the surface of the metal substrate. The adsorbed precursor gas molecules then decompose to form carbon, which remains on the surface of the metal substrate and forms graphene. This process may also involve decomposition of the precursor gas prior to adsorption on the surface and subsequent stacking of the resulting carbon atoms. Any volatile components are typically delivered by a vacuum pumping system. A particular method for making graphene films using CVD involves the use of a metal substrate formed from a metal, such as nickel or copper. This is at least in part because both nickel and copper allow graphene to grow epitaxially on specific crystalline facets on their surfaces.

[0004]

[0004] Graphene is traditionally produced by a chemical vapor deposition (CVD) process carried out at high temperatures and low pressures, known as low-pressure CVD (LP-CVD). It has been observed that in such processes, metal atoms, i.e., copper or nickel, tend to evaporate from the surface of the metal substrate. This results in an uneven substrate surface, which in turn can lead to wrinkled or incomplete formation of graphene at that surface, as the surface morphology of the substrate surface is incorporated into the graphene. This can prevent the formation of large domains of continuous graphene. Furthermore, subsequent transfer of a wrinkled and / or incomplete graphene layer to another substrate can cause the resulting graphene layer to be similarly wrinkled and / or subject to various strains throughout the layer. Such methods can also provide graphene layers with small grain sizes, which can be detrimental to carrier mobility, for example, because the crystal lattices of adjacent grains typically do not align. Small grain sizes can result, for example, from high and / or uneven nucleation densities during formation or poor crystal alignment during formation, or a combination thereof.

[0005]

[0005] Known solutions for addressing or at least reducing the above-described problems associated with evaporation of metal atoms from exposed metal substrates on which graphene layers are to be formed include using at least partially enclosed substrate holders and / or providing a counter surface opposite the exposed surface of the metal substrate to prevent or at least reduce net evaporation of metal atoms from the deposition region.

[0006]

[0006] Methods using a counter surface opposite the exposed substrate are described in WO 2014 / 033282 A1. These methods have been shown to effectively prevent net copper evaporation.

[0007] However, the above documents do not provide an efficient, highly accurate, and rapid method for achieving a well-defined distance between a metal substrate and a counter surface, and conventional retainers or substrate supports are not suitable for direct mounting in industrial manufacturing lines, for example, in semiconductor manufacturing plants. Summary of the Invention [Problem to be solved by the invention]

[0008] It is an object of the present invention to provide a substrate retainer that provides a well-defined distance between the exposed surface of the metal substrate and the counter surface.

[0009]

[0009] It is a further object to provide a substrate retainer that can be handled by conventional manufacturing line and / or semiconductor manufacturing factory systems, particularly for transporting the retainer through a manufacturing factory or manufacturing line and performing low-pressure chemical vapor deposition, LP-CVD, on a substrate carried by the retainer. [Means for solving the problem]

[0010]

[0010] This is achieved by the substrate retainer defined in claim 1.

[0011] According to a first aspect, there is provided a retainer for holding a substrate during chemical vapor deposition, CVD, processing, the retainer comprising: a first surface configured to form a counter surface to the exposed surface of the substrate; a second surface positioned substantially parallel to the counter surface and a distance d from the counter surface, the second surface being configured to support a substrate; a third surface disposed at an angle relative to the second surface, the third surface forming an edge for constraining movement of the substrate.

[0012] The retainer may be configured such that when the substrate is held by the retainer, a reaction cavity is formed between the exposed surface of the substrate and the counter surface.

[0013] That is, the substrate must be positioned upside down in the retainer with its exposed surface facing the counter surface, which is then positioned opposite the exposed surface of the substrate. The cavity thus formed forms the reaction cavity, or reaction space, where the chemical processes associated with chemical vapor deposition occur.

[0014] The retainer is configured to support the substrate while the substrate rests on the second surface under gravity, and therefore does not require the use of fastening means, such as screws, clamps, and / or glue, to maintain the substrate on the retainer.

[0015] Due to this reaction cavity, the net evaporation of metal atoms, for example copper, from the exposed surface of the substrate can be offset.

[0016] The distance d between the counter surface and the second surface is a predetermined distance, typically in the range of several hundred mm to several mm. For example, the distance d may be in the range of 25 to 250 μm, more preferably in the range of 100 to 200 μm. For example, the distance may be 100 μm or 200 μm. However, larger distances are also possible. For example, a distance of up to 5 mm may be used. This distance defines the cavity depth of the retainer. A larger distance, i.e., a deeper cavity, results in a thicker retainer, which in turn is heavier to be carried by a robot arm.

[0017]

[0017] The cavity dimensions, especially the distance between the exposed surface and the counter surface of the substrate, have been considered critical for the CVD process. This distance value has been considered to be able to prevent metal atoms, such as copper atoms, from escaping from the cavity, which would result in net evaporation. By setting a distance that is extremely small compared to the areas of the exposed and counter surfaces, most of the metal atoms are redeposited or reabsorbed on the exposed surface and are not lost. Some metal atoms are still lost due to evaporation through the open sides of the cavity. However, this loss has been considered negligible, or at least small enough, on the timescale of the LP-CVD process. The sides of the cavity are open to allow process gases to diffuse into the cavity to enable laminar growth.

[0018] Furthermore, the roughness of the counter surface is also believed to affect the chemical reactions that occur during the CVD process: surface roughness is believed to affect the outcome of collisions between precursor molecules and / or evaporated metal atoms, thereby affecting their mean free path in the cavity and the distance they travel before (re)absorption on the exposed surface.

[0019]

[0019] Thus, the distance between the exposed surface and the counter surface, and possibly also the roughness of the counter surface, influences the reaction during CVD and the resulting film formed.

[0020] The retainer may further include at least one inlet provided between the first and second surfaces, the inlet configured to introduce one or more process gases into the retainer. That is, the inlet allows for the introduction of precursor gases into the reaction cavity formed when the exposed substrate is positioned in the retainer. The inlet may be provided in the form of one or more openings.

[0021]

[0021] The retainer thus provides an inlet path for the precursor gas, and at the same time, as mentioned above, the dimensions of the cavity are designed to increase the probability that the metal atoms will sublime back to the exposed surface rather than leaking out of the cavity.

[0022]

[0022] The second surface may advantageously be formed by a plurality of ledges projecting from the body of the retainer, the body including the first surface. Preferably, three ledges are provided to provide stability for the substrate. Alternatively, other forms of support elements projecting from the body and forming a support surface for the substrate may be provided. What is important is that the second surface, which forms the support on which the substrate rests during CVD processing, is a well-defined distance from the counter surface. Preferably, the exposed surface of the substrate is substantially parallel to the counter surface.

[0023]

[0023] The third surface may be formed by an edge projecting from at least one of the ledge or the second surface. Preferably, the third surface may be formed by an edge projecting from each of the ledge or the second surface.

[0024]

[0024] At least one edge formed by the third surface prevents or restricts movement of the substrate, particularly in the horizontal direction, ie in a direction parallel to the counter surface.

[0025] The second and third surfaces, ie, the ledges and edges, are preferably substantially uniformly distributed around the periphery of the counter surface.

[0026] The retainer may include or be formed from quartz, and the counter surface may therefore be a quartz surface.

[0027]

[0027] Quartz is traditionally used in a variety of applications in semiconductor manufacturing and processing. Quartz has many advantages, including high availability and availability in semiconductor wafer shapes and sizes at relatively low cost. It is also relatively easy, or at least simple, to machine. For example, processes such as sandblasting can be used to remove bulk material to pre-shape the quartz body. Other processes, such as laser micromachining, can then be used to shape the retainer with high precision and / or to provide a smooth surface.

[0028] Furthermore, quartz has a low coefficient of thermal expansion, resulting in low stress and strain in the quartz body, even at the high temperatures encountered during LP-CVD processes. Quartz has been observed to be able to withstand numerous temperature cycles, e.g., up to temperatures used in graphene production by CVD, such as about 1000°C, followed by cooling to room temperature. As a result, the retainers presented herein can be reused through many cycles of CVD processing.

[0029] The retainer may be of one-piece construction, i.e., the counter surface, second surface, and third surface may be formed by machining the quartz body and may be integrally formed from the quartz body.

[0030] Alternatively, the retainer may include: a body including a first surface, the first surface including a counter surface and a groove at least partially surrounding the counter surface; - a set of support elements configured to be positioned in the groove, the support elements forming a second surface and a third surface; and may include:

[0031] The support elements may be provided in a variety of sizes, thereby allowing substrates of various sizes to be supported by the retainer.

[0032]

[0032] Further alternatively, the retainer may include: a body including a first surface, at least a portion of the first surface forming a counter surface, a first set of notches and a second set of notches, the second notches being offset from the first notches; a set of first support elements configured to be positioned in the first notches, the first support elements defining a second surface; a set of second support elements configured to be positioned in the second notches, the second support elements defining a third surface; and may include:

[0033] The first and second support elements are preferably distributed substantially uniformly around the circumference of the counter surface.

[0034] The first and second support elements form separate support elements for supporting or carrying the exposed substrate and for bounding its lateral movement. By separating the two functions in embodiments in which the retainer is not formed as a unitary structure but is formed by separate support elements, manufacturing complexity and cost may be reduced compared to using the same support element for both functions.

[0035] The substrate may include a sapphire substrate provided with an epitaxial metal layer forming an exposed surface. The metal layer is generally a thin metal film. The metal may be selected from one or more of copper (Cu), nickel (Ni), nickel-copper (NiCu) alloy, platinum (Pt), and the like. The epitaxy of the metal film makes the exposed surface suitable for the growth of graphene thereon. This has been shown to provide a tractable substrate, allowing for the formation of large areas of high-quality graphene.

[0036] However, the thermal expansion coefficient of sapphire is different from that of the quartz, which is preferably used for the retainer. The substrate therefore experiences a different thermal expansion, i.e., expands more than the retainer. This can be explained by the design of the dimensions, ledges, and edge locations of the retainer, as explained in the next paragraph.

[0037]

[0037] Preferably, the retainer may include multiple edges positioned to allow the substrate to thermally expand during the CVD process while still providing a mechanical interface between the edges and the circumferential edge of the substrate.

[0038] The mechanical interface can be implemented as a distance between the edge of the substrate and the circumferential edge, i.e., as the distance between the edge of the substrate and the circumferential edge, which can also be called "play" or mechanical "play".

[0039] That is, the second and third surfaces are preferably positioned and dimensioned to allow for thermal expansion of the substrate during CVD processing without the substrate becoming clamped and / or fixed to the retainer. That is, the ledge or other support element forming the second surface is positioned and / or dimensioned so that a distance is achieved between the edge formed by the third surface and the lateral edges of the substrate. The distance, also referred to as play, may be designed or calculated to hold the substrate in the retainer during handling by, for example, a robot that moves the substrate-loaded retainer between different stations in a system such as a semiconductor fabrication facility, while allowing the substrate to thermally expand due to the high temperatures to which the substrate is subjected in the CVD process without being subjected to stresses or strains caused by mechanical clamping of the substrate.

[0040]

[0040] The positions and dimensions referred to herein above can be designed by designing the retainer to correspond to the dimensions of the substrate that it will hold.

[0041] The retainer may be scaled and / or otherwise configured to support substrates having dimensions corresponding to various known semiconductor wafer dimensions.

[0042] The retainer is particularly advantageous in low pressure chemical vapor deposition, LP-CVD, processes and systems.

[0043]

[0043] Thus, in summary, according to a first aspect, there is provided a substrate retainer that performs multiple functions, including transferring a substrate and forming a counter surface, and that allows for a simple method of implementing the retainer into a substrate CVD processing system for forming graphene layers and other types of semiconductor processing.

[0044] The retainer allows for easy and quick positioning of the substrate on the retainer at a well-defined and very precise distance from the counter surface.

[0045] Furthermore, the retainer may advantageously be shaped and dimensioned to permit its handling by conventional wafer handling robots used in semiconductor manufacturing. In particular, the retainer is configured to be held by the robot arm of a conventional wafer handling robot, for example, to fit into storage racks such as wafer cassettes, and to be positioned and raised and lowered by lift pins and other substrate positioning mechanisms provided in processing, transfer, and / or storage chambers in the (vacuum) systems of semiconductor manufacturing factories.

[0046]

[0046] According to a second aspect, a stack is provided that includes the retainer of the first aspect and a substrate having an exposed surface, wherein the retainer supports the substrate on the second surface with the exposed surface facing toward the counter surface.

[0047] As described hereinabove, the retainer is advantageously sized and shaped to allow handling by conventional semiconductor wafer handling robots. The retainer is provided with elements that allow the retainer to be held and moved by the arms of such robots, as is known in the field of semiconductor manufacturing. This allows for the implementation and use of the stack formed by the retainer and substrates in existing processing systems and facilities, for example, semiconductor manufacturing plants.

[0048]

[0048] As described herein above in relation to the first aspect, the substrate may be a sapphire substrate provided with an epitaxial metal layer, the epitaxial metal layer forming the exposed surface. The substrate may have the dimensions of a semiconductor wafer.

[0049] According to a third aspect, there is provided a method of manufacturing a retainer for holding a substrate, the method comprising: - providing a body having a first surface; - forming a counter surface on the first surface; - forming a second surface substantially parallel to the counter surface and positioned a distance d from the counter surface, the second surface configured to support a substrate; forming a third surface disposed at an angle relative to the second surface to form an edge for constraining movement of the substrate; Includes The step of forming the counter surface comprises: a first processing step for forming a distance d between the second surface and the part of the first surface that will form the counter surface; a second processing step applied to the portion of the first surface, the second processing step including reducing the resulting roughness of the portion of the first surface after the first processing step; Includes.

[0050]

[0050] The first processing step may involve a material removal technique, for example sandblasting, whereby a cavity may be formed in the body.

[0051] The second processing step may include an abrasive process, for example laser patterning, for example laser micromachining.

[0052] In particular, the retainer formed by the method of the third aspect forms a unitary structure.

[0053] According to a fourth aspect, there is provided a method of manufacturing a retainer for holding a substrate, the method comprising: - providing a body having a first surface; - forming a counter surface on the first surface; - forming a second surface substantially parallel to and spaced apart from the counter surface, the second surface configured to support a substrate; forming a third surface disposed at an angle relative to the second surface to form an edge for constraining movement of the substrate; Including, The step of forming the counter surface comprises: - forming a groove at least partially surrounding a portion of the first surface; - placing a plurality of support elements in the groove, each of the support elements including a second surface and at least one of the support elements further including a third surface; and Includes.

[0054]

[0054] By the method of the fourth aspect, the countersurface may be formed from a substantially untreated surface of the quartz material without subjecting the first surface to material removal techniques on the portion of the first surface that will form the countersurface.

[0055]

[0055] Machining may only be required to form the grooves in which the support elements are positioned and / or attached, for example according to the first and finally second machining steps described in relation to the method of the third aspect.

[0056] The support elements may be permanently or removably positioned in the grooves. Different sized support elements may also be provided to facilitate the retainer being adaptable to substrates of different sizes.

[0057]

[0057] A retainer manufactured by either of the methods according to the third and fourth aspects may advantageously be a retainer according to various embodiments of the first aspect.

[0058]

[0058] Thus, in summary, the present invention relates to a retainer for holding graphene growth substrates for processing in a cassette-to-cassette automated CVD system. The system is designed to load wafers from a cassette into a load lock chamber and from the load lock chamber into a process chamber. In the process chamber, graphene is grown on these wafers by a CVD process at high temperatures. When Cu is used as the exposed surface, the temperature during CVD is typically between 800°C and 1088°C. When Ni is used as the exposed surface, the temperature is typically between 600°C and 1200°C. The wafers are then removed and placed into the load lock and subsequently into a cassette.

[0059]

[0059] Graphene is preferably grown on epitaxial sapphire substrates with 500-2000 nm of Cu layer on the sapphire. However, copper evaporates significantly at typical growth temperatures for graphene. Several approaches have been implemented in other systems (tube furnaces rather than cassette-to-cassette systems) to prevent Cu from evaporating from the surface, such as encasing the Cu foil, folding the copper foil, or providing a counter surface.

[0060] According to the present disclosure, the counter surface is simultaneously implemented with multiple functionalities, preferably as a quartz wafer machined to support an inverted sapphire / Cu substrate on three ledges machined to become the quartz substrate.

[0061] The quartz substrate may be a 200 mm quartz wafer that is compatible with the robot arm, cassette and lift pin mechanism, and heater in the process chamber. At the same time, the ledge structure prevents the wafers from shifting while the retainer wafer stack is moved on the robot. The distance between the exposed surface of the substrate and the counter surface is such that net evaporation from the epitaxial metal layer on the exposed surface is negligible. The distance, i.e., the cavity depth, prevents metal atoms, e.g., copper, from evaporating from the substrate, since most of the copper is redeposited and not lost.

[0062]

[0062] In this application, the term "retainer" is to be understood as a structure that holds a substrate during, and preferably before and / or after, a CVD process, which may also be called a substrate holder, a substrate carrier, or a substrate susceptor.

[0063]

[0063] The term "substrate" is to be understood as an element provided with a surface on which a graphene layer or film will be formed, which may also be called a wafer.

[0064]

[0064] Further features and advantages of the present invention will become apparent from the description of the invention by means of non-limiting and non-exclusive embodiments. These embodiments are not to be construed as limiting the scope of protection. Those skilled in the art will recognize that other alternatives and equivalent embodiments of the invention may be conceived and may be put into practice without departing from the scope of the invention. Embodiments of the present invention will be described with reference to the accompanying drawings, in which similar or identical reference numerals indicate the same or corresponding parts. [Brief explanation of the drawings]

[0065] [Figure 1a]

[0065] A schematic cross section of a retainer support substrate according to the first embodiment is shown. [Figure 1b]

[0066] 1 shows a schematic top view of a retainer according to a first embodiment. [Figure 2a]

[0067] 10 shows a cross section of a retainer according to a second embodiment. [Figure 2b]

[0068] FIG. 10 is a schematic top view of a main body of the retainer according to the second embodiment. [Figure 3]

[0069] 10 shows a cross section of a retainer according to a third embodiment. [Figures 4a-4c]

[0070] 10A and 10B schematically illustrate features of a retainer according to a fourth embodiment. [Figure 5]

[0071] 1 shows a schematic diagram of a system for chemical vapor deposition. DETAILED DESCRIPTION OF THE INVENTION

[0066]

[0072] 1A and 1B show non-limiting embodiments of a retainer according to a first embodiment. Fig. 1A shows a cross section of a stack formed by a retainer 1 carrying a substrate 2. Fig. 1B shows a top view of the retainer 1, with the substrate 2 shown in dashed lines.

[0067]

[0073] According to a first embodiment, the retainer 1 is formed in a single piece. As described above, the retainer 1 may be formed of a single piece quartz body. A recess is machined in the quartz body to form a second surface 5 that forms a ledge or support surface for the substrate 2. When the substrate 2 is held by the retainer, a cavity 4 is formed.

[0068]

[0074] While FIG. 1A may suggest that the ledges 5 and edges 6 are located 180° opposite each other, this is shown as such primarily for illustrative purposes of the concept, while preferably the ledges and edges are positioned 120° apart, as three of them are preferably provided.

[0069]

[0075] To produce graphene in an LP-CVD process, a substrate 2 is typically provided with a metal film 3. For example, the substrate 2 may be a sapphire substrate on which an epitaxial copper film is formed. The metal film 3 is provided to provide an exposed surface with surface properties, such as an atomic lattice, suitable for graphene growth.

[0070]

[0076] In the cavity, a first surface forming the counter surface 8 is formed, which is located a distance d from a second surface formed by the ledge 5. The distance d can be formed with high precision.

[0071]

[0077] The cavity 4 forms a reaction cavity in which a CVD process occurs to form a graphene film 7.

[0072]

[0078] 1B shows a schematic diagram of a retainer according to a first embodiment, viewed from above. As shown in FIG. 1B, preferably three ledges 5 and edges 6 are provided, which are substantially uniformly distributed around the counter surface. Also shown, one or more inlets 10 are provided for introducing precursor gases into the cavity 4. Such precursor gases may typically include methane, CH, ethane, C2H6, or other carbon containing gases.

[0073]

[0079] The retainer is further dimensioned relative to the dimensions of the substrate 2, which advantageously has the dimensions of a conventional semiconductor wafer, to allow the substrate with the copper film 3 to thermally expand due to the temperatures applied during the CVD process.

[0074]

[0080] Advantageously, the retainer has a diameter d of an imaginary circle defined by the edge 6. e is dimensioned so that there is a play, or distance also called interface p, between the edge of the substrate and edge 6 even when the substrate is undergoing its maximum thermal expansion during the CVD process.

[0075]

[0081] 2A and 2B show a retainer 20 according to a second embodiment. In contrast to the retainer 1 according to the first embodiment, the retainer 20 according to the second embodiment is not a unitary structure, but includes a body 21 and a plurality of support elements 29 disposed in grooves 31 formed in a surface 21s of the body. The support elements 29 include a second surface or ledge 25 and a third surface or edge 26 that functionally correspond to the ledge 5 and edge 6 of the retainer 1 shown in FIGS. 1A and 1B. A substrate 2 provided with an epitaxial layer 3, shown by a dashed line, is held by the retainer 20 in a manner similar to that of the retainer 1 shown in FIGS. 1A and 1B.

[0076]

[0082] 2B shows a schematic top view of the body 21 of the retainer. As shown, groove 31 is machined into the surface 21s of the body. While FIG. 2B shows groove 31 as a full circumference surrounding counter surface 28, it is not necessary for groove 31 to be provided as a full circumference. Alternatively, groove 31 may be formed as multiple, e.g., at least three, semicircles evenly distributed around counter surface 28.

[0077]

[0083] According to the second embodiment, the counter surface 28 may be formed as part of the surface 21s of the quartz body without the need for material removal. This may result in a smoother counter surface 28 than the counter surface 8 of the first embodiment, which was formed through material removal techniques. It is expected that the smoothness of the counter surface 8, 28 may affect the behavior of atoms and / or molecules present within the cavity 4, 24, particularly their behavior upon and resulting from collision with the counter surface.

[0078]

[0084] The support elements 29 may be provided with different dimensions, for example different dimensions of the second surface area 25, to allow the retainer to accommodate substrates of different sizes.

[0079]

[0085] FIG. 3 shows a schematic cross-sectional view of a retainer 40 according to a third embodiment. The retainer of the third embodiment has many similarities to the retainer of the second embodiment shown in FIGS. 2A and 2B , and therefore will not be described in full detail herein. Like the retainer 20 of the second embodiment, the retainer 40 is not a unitary structure, but is formed of a body 41, at least one support element 49, and a plurality of additional support elements 52. The at least one support element 49 provides a second surface 45 and a third surface 46, i.e., edges and ledges. The at least one support element 49 is disposed in a groove 51 formed in the surface 41s of the body. The edge 46 of the support element 49 thus forms an edge that constrains lateral movement of the substrate 2. Additionally, an additional support element 52 is provided that forms a second surface on which the substrate 2 rests. Although FIG. 3 shows that the retainer 40 includes one support element 46 and three additional support elements 52, these may be provided in different numbers, so long as the substrate rests on the retainer to create a well-defined and very precise distance between the exposed surface 3 of the substrate and the counter surface 48.

[0080]

[0086] Figures 4A, 4B and 4C show schematic diagrams of a retainer 200 according to a fourth embodiment. The concept is similar to that of the second embodiment shown in Figures 2A and 2B, with the main difference being that the functions of supporting the exposed substrate 2 (horizontally) and constraining the lateral movement or displacement of the substrate 2 are separated and achieved by two different types of support elements, namely a first support element 241 and a second support element 242, respectively.

[0081]

[0087] 4A shows a schematic top view of retainer body 210. As shown, it is provided with three notches 310 formed in its top surface for receiving first support elements 241, and three additional notches 320 also formed in its top surface for receiving second support elements 242.

[0082]

[0088] As shown, all of the first and second notches 310 and 320 are substantially uniformly distributed around the circumference of the counter surface. Preferably, the first and second notches, and thus the first and second support elements 241 and 242, are offset relative to one another.

[0083]

[0089] 4A, the retainer is configured to support an exposed substrate 2 having a diameter corresponding to, i.e., the same as, the diameter of the retainer body 210. This means that the portions of the second support elements 242 that fit into the second cutouts 320 protrude with their thicker portions 242-1 laterally outward from the retainer body 210. However, the second support elements can be positioned so as not to interfere with, for example, robotic handling of the retainer 200.

[0084]

[0090] 4B shows a schematic side view of the first support element 241. The first support element 241, which may be formed as a rectangular or cubic block, is positioned within a notch 310 provided in the retainer body 210. The height of the first support element 241 in combination with the depth of the notch 310 defines the distance d between the counter surface 280 formed by the top surface of the body 210 and the top surface 250 of the first support element, which forms the second surface. Thus, the first support element 241, together with the first notch 310, defines the cavity depth of the reaction cavity formed in the retainer when it carries an exposed substrate.

[0085]

[0091] Since the first support element 241 together with the first cutout 310 defines the cavity depth, i.e., the distance between the exposed surface and the counter surface, the first support element and the first cutout must be manufactured with high precision. In particular, their horizontal surfaces must be smooth, for example, providing a surface with low roughness. The first support element can advantageously be machined through material removal or abrasive techniques, for example, laser micromachining.

[0086]

[0092] 4C shows the second support elements 242 schematically in a side view. The second support elements may be formed substantially L-shaped, with the thicker portions 242-1 defining a third surface 260 configured to bound or restrain lateral movement of the exposed substrate 2 in the same manner as described herein above with respect to the first and second embodiments. The thickness of the thicker portions 242-1 of each second support element 242, which defines the vertical dimension of the third surface 246, is high enough to restrain lateral movement of the exposed substrate 2. The depth of the second notch 320, together with the thickness of the thinner portions 242-2 of the support elements 242, is such that the distance between the upper surface of the portions 242-2 and the counter surface 280 is preferably less than the distance d between the second surface 250 and the counter surface 280, such that the exposed substrate 2 is fully supported by the second surface 250, and thus the exposed surface is at a well-defined distance from the counter surface 280. At most, it may be flush with the second surface 250 .

[0087]

[0093] The second support elements 242 are not responsible for setting the cavity distance. Therefore, the second support elements may be manufactured with less precision than the first support elements because of the lower requirements for their dimensional precision, especially the low roughness of their surfaces. Therefore, the second support elements 242 may be manufactured using material removal techniques such as sandblasting.

[0088]

[0094] Therefore, separating the function of supporting the substrate and the function of restraining its lateral displacement may result in a less complex retainer manufacturing process.

[0089]

[0095] 5 shows a schematic top view of an LP-CVD system, which can be any conventional LP-CVD system. The system includes a load lock 52, also called a transition chamber and / or parking chamber, through which wafers can be moved between a wafer cassette 54 and a CVD processing chamber 56. Wafers can be moved between the cassette, intermediate positions in the load lock, and processing chambers by a robot 58, also called a wafer handling robot.

[0090]

[0096] The processing chamber 56 may include various components known in the art of (low-pressure) chemical vapor deposition, such as one or more heaters for heating the substrate, gas inlets, vacuum pumps, etc. Such components are described in WO 2014 / 033282 A1.

[0091]

[0097] As can be appreciated from the above, the retainers according to the different embodiments described hereinabove have dimensions that correspond to semiconductor wafers and therefore can be positioned in a wafer cassette 54, lifted and moved by a robot 58, or positioned on lift pins and / or wafer carrying means provided in a processing chamber 56 and known in the art.

[0092]

[0098] Thus, as described above, the retainer according to the present disclosure provides a robust, passive support for substrates to be exposed to LP-CVD processes, particularly for forming graphene layers, and through the design of the retainer, a well-defined distance is formed between the exposed surface of the substrate and the counter surface of the retainer, thereby preventing or at least limiting net evaporation of metal atoms, such as copper, from the exposed surface. Furthermore, the retainer is of a shape, weight, and dimensions similar to conventional semiconductor wafers and wafer carriers, thereby allowing the stack formed by the retainer and substrate to be used in existing low-pressure chemical vapor deposition (LP-CVD) systems and other semiconductor manufacturing facilities without substantial modification or adaptation.

[0093]

[0099] The present invention therefore provides a passive method of preventing Cu evaporation by creating a facing surface, referred to herein as the counter surface, at a defined distance from the surface of the substrate's epitaxial metal layer.

[0094]

[0100] One could imagine a movable counter surface that could be mechanically brought close to the wafer surface prior to heating the surface, but this would mean designing a system with moving parts and micron precision that could function in thermal cycles up and down 1000° C. By doing this in a passive manner as described herein, the inventors avoid having to solve that problem.

[0095]

[0101] At the same time, the structure of the retainer can be machined into the quartz wafers, which allows for the use of conventional methods of handling the stack (quartz retainer + sapphire / Cu) with a robotic arm and storing it in a cassette, which can be a commercially available cassette selected to be of the type having slots sized to allow handling of the stack formed by the retainer and substrate.

[0096]

[0102] The structure of the retainer is designed to accommodate differences in thermal expansion between the quartz and the sapphire. Because sapphire expands more than quartz, space is taken up within the quartz structure to accommodate the expansion of the sapphire substrate. At the same time, the sapphire cannot move more than required to accommodate thermal expansion to keep it in place. If a precise fit is achieved, the sapphire may break during thermal expansion.

[0097]

[0103] Quartz is preferably used as the material because it has a low coefficient of thermal expansion (CTE). Therefore, thermal cycling quartz through 1000°C cycles does not result in significant stress in the material, and the material is more tolerant to variations in thermal uniformity that can cause additional stresses that lead to material failure. Quartz as a material does not interfere with the graphene growth process. Additionally, it is readily and inexpensively available in the form of high-purity wafers.

[0098]

[0104] The scope of the present invention is not limited to the examples discussed above, but it will be apparent to those skilled in the art that certain amendments and modifications thereof are possible without departing from the scope of the present invention as defined in the appended claims. While the present invention has been illustrated and described in detail in the drawings and description, such illustration and description are to be considered merely for purposes of illustration or example and not for purposes of limitation. The present invention is not limited to the disclosed embodiments, but includes any combination of the disclosed embodiments that may be advantageous.

[0099]

[0105] For example, although not described in detail above, the retainer may be configured to support two or more substrates. That is, the retainer may be provided with multiple substrate support regions, each including a cavity, a counter surface, second and third surfaces, or ledges and edges according to the embodiments described herein above. That is, when viewed from a top view, multiple substrates supported by the retainer may be arranged to form part of a hexagonal surface lattice arrangement or an fcc surface lattice structure.

[0100]

[0106] Variations to the disclosed embodiments can be understood and effected by those skilled in the art in practicing the claimed invention, from a study of the figures, the description, and the appended claims. In the description and claims, the term "comprising" does not exclude other elements, and the indefinite articles "a" or "an" do not exclude a plurality. In fact, it is interpreted as meaning "at least one." The mere fact that certain features are recited in mutually different dependent claims does not indicate that a combination of these features cannot be used to advantage. Any reference signs in the claims should not be construed as limiting the scope of the invention. Features of the above-described embodiments and aspects may be combined unless such combination results in an obvious technical contradiction.

Claims

1. 1. A retainer for holding a substrate during chemical vapor deposition, CVD, processing, said retainer comprising: a first surface configured to form a counter surface to the exposed surface of the substrate; a second surface substantially parallel to said counter surface and arranged at a distance d from said counter surface, said second surface being arranged to support said substrate; a third surface disposed at an angle to said second surface, said third surface forming an edge for constraining movement of said substrate; A retainer including:

2. The retainer of claim 1 , configured such that a reaction cavity is formed between the exposed surface of the substrate and the counter surface when the substrate is held by the retainer.

3. The retainer of claim 1 or 2, wherein at least one inlet is provided between the first surface and the second surface, the inlet configured to introduce one or more precursor gases into the retainer.

4. The retainer of any one of claims 1 to 3, wherein the second surface is formed by a plurality of ledges projecting from a body of the retainer, the body including the first surface.

5. The retainer of claim 4 , wherein the edge projects from at least one of the ledges.

6. The retainer of any one of claims 1 to 5, wherein the retainer comprises quartz.

7. The retainer of any one of claims 1 to 6, wherein the retainer is of unitary construction.

8. The retainer is a body including said first surface, said first surface including said counter surface and a groove at least partially surrounding said counter surface; a set of support elements configured to be positioned in said grooves, said support elements forming said second surface and said third surface; The retainer according to any one of claims 1 to 6, comprising:

9. The retainer is a body including said first surface, at least a portion of said first surface forming said counter surface, a first set of notches and a second set of notches, said second notches being offset from said first notches; a set of first support elements configured to be positioned in said first cutouts, said first support elements defining said second surface; a second set of support elements configured to be positioned in said second cutouts, said second support elements defining said third surface; The retainer according to any one of claims 1 to 6, comprising:

10. The retainer according to any one of claims 1 to 9, wherein the distance d is in the range of 50 to 250 µm, preferably 100 to 200 µm.

11. 11. The retainer of claim 1, wherein the retainer includes a plurality of edges positioned to allow the substrate to thermally expand during the CVD process while still providing a mechanical interface between the edges and a circumferential edge of the substrate.

12. A stack comprising the retainer of any one of claims 1 to 11 and a substrate including an exposed surface, wherein the retainer supports the substrate on the second surface with the exposed surface facing the counter surface.

13. 13. The stack of claim 12, wherein the substrate is a sapphire substrate having an epitaxial metal layer thereon, the epitaxial metal layer forming the exposed surface.

14. Stack according to claim 12 or 13, wherein the substrate has the dimensions of a semiconductor wafer.

15. 1. A method for manufacturing a retainer for holding a substrate, the method comprising: - providing a body having a first surface; - forming a counter surface on said first surface; - forming a second surface substantially parallel to the counter surface and spaced a distance d from the counter surface, the second surface being configured to support the substrate; forming a third surface disposed at an angle to the second surface, the third surface forming an edge for constraining movement of the substrate; Including, forming the counter surface comprises: a first processing step for forming said distance d between said second surface and the part of said first surface that will form said counter surface; a second processing step applied to said portion of said first surface, said second processing step comprising reducing the resulting roughness of said portion of said first surface after said first processing step; A method comprising:

16. 1. A method for manufacturing a retainer for holding a substrate, the method comprising: - providing a body having a first surface; - forming a counter surface on said first surface; - forming a second surface substantially parallel to the counter surface and spaced a distance d from the counter surface, the second surface being configured to support the substrate; forming a third surface disposed at an angle to the second surface, the third surface forming an edge for constraining movement of the substrate; Including, forming a counter surface; forming a groove at least partially around the portion of said first surface that will form said counter surface; placing a plurality of support elements in said groove, each of said support elements including said second surface and at least one of said support elements further including said third surface; A method comprising:

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