Substrate holder

Abstract

A holder for holding a substrate during a chemical vapor deposition (CVD) process, the holder having:-a first surface configured to form an opposing surface for an exposed surface of the substrate; -a second surface substantially parallel to the opposing surface and arranged at a distance d from the opposing surface, the second surface being arranged for supporting the substrate; -a third surface arranged at an angle to the second surface, the third surface forming an edge limiting movement of the substrate.

Description

Technical Field

[0001] The present invention relates to a substrate holder, in particular to a substrate holder for supporting a substrate during a chemical vapor deposition (CVD) process, and to a method for manufacturing such a holder. The holder is particularly suitable for low-pressure chemical vapor deposition (LP-CVD) of thin graphene films. Background Art

[0002] Graphene has been observed to have specific properties, for example related to electrical and / or chemical properties, which make it very attractive 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) is conventionally used to produce graphene layers and films. In this known CVD process, the surface of a metal substrate is exposed to a carbon-containing precursor gas, such as methane, ethane, ethylene or benzene, which causes the precursor gas molecules to be adsorbed 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. The process can also involve the precursor gas decomposing before being adsorbed on the surface, and subsequently depositing the resulting carbon atoms. Any volatile components are typically pumped away by a vacuum pumping system. Certain methods of using CVD to manufacture graphene films involve the use of a metal substrate formed of a metal (such as nickel or copper). This is at least in part because both nickel and copper allow graphene to grow epitaxially on certain crystal facets on its surface.

[0004] Graphene is conventionally produced by a CVD process (so-called low-pressure CVD, LP-CVD) performed at high temperature and low pressure. It has been observed that in such a process, 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 may produce wrinkled or incompletely formed graphene on the surface, because the surface morphology of the substrate surface will be built into the graphene. This may hinder the formation of large-area continuous graphene. In addition, the subsequent transfer of wrinkled and / or incomplete graphene layers to another substrate will cause the resulting graphene layers to also wrinkle and / or experience varying strains throughout the layer. Such a method may also provide a graphene layer with a small grain size, which may be detrimental to carrier mobility, for example, because the lattices of adjacent grains are generally not aligned. Small grain size may be produced by, for example, high and / or uneven nucleation density when formed or poor crystal arrangement when formed, or a combination thereof.

[0005] Known measures for solving or at least reducing the above-mentioned problems associated with the evaporation of metal atoms from an exposed metal substrate on which a graphene layer is to be formed include using an at least partially closed substrate holder and / or providing an opposing surface opposite the exposed surface of the metal substrate in order to prevent or at least reduce the net evaporation of metal atoms from the deposition area.

[0006] Methods using an opposing surface opposite the exposed substrate are described in WO 2014 / 033282 A1. These methods have been found to be effective in preventing net copper evaporation.

[0007] However, the publications cited above do not provide an effective, highly accurate and fast way to achieve a well-defined distance between the metal substrate and the opposing surface. Furthermore, conventional holders or substrate supports are not suitable for direct implementation in industrial production lines, such as in semiconductor manufacturing plants. Summary of the Invention

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

[0009] Another object is to provide a substrate holder that can be handled by conventional production lines and / or semiconductor fab systems, in particular for transporting the holder through the fab or production line and performing low pressure chemical vapor deposition LP-CVD on a substrate carried by the holder.

[0010] This is achieved by a substrate holder as defined in claim 1 .

[0011] According to a first aspect, a holder for holding a substrate during a chemical vapor deposition (CVD) process, the holder comprising: a first surface configured to form an opposing surface relative to the exposed surface of the substrate; a second surface substantially parallel to the opposing surface and arranged at a distance d from the opposing surface, the second surface being arranged to support the substrate; A third surface is arranged at an angle to the second surface, the third surface forming an edge for limiting movement of the substrate.

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

[0013] That is, the substrate should be positioned upside down on the holder, with the exposed surface of the substrate facing the opposing surface. The opposing surface will then be positioned opposite the exposed surface of the substrate. The cavity thus formed forms the reaction cavity or reaction space in which the chemical processes involved in chemical vapor deposition occur.

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

[0015] Due to the reaction cavity, net evaporation of metal atoms (such as copper) from the exposed surface of the substrate can be counteracted.

[0016] The distance d between the opposing surface and the second surface is a predefined distance, typically in the range of a few hundredths of a mm to a few mm. For example, the distance d can be in the range of 25 μm to 250 μm, more preferably in the range of 100 μm to 200 μm. For example, the distance can be 100 μm or 200 μm. However, greater distances are also possible. For example, a distance of up to 5 mm can be used. This distance defines the cavity depth of the holder. A larger distance (i.e., cavity depth) will result in a thicker holder, which in turn causes the robot arm to carry more weight.

[0017] The size of the cavity, in particular the distance between the exposed surface and the opposing surface of the substrate, has been found to be important for the CVD process. The value of this distance has been found to prevent metal atoms (such as copper atoms) from escaping from the cavity, which could cause net evaporation. By setting the distance to be very small compared to the area of the exposed surface and the opposing surface, most of the metal atoms will be re-deposited or re-adsorbed onto the exposed surface without being lost. Some metal atoms may still be lost due to evaporation through the open sides of the cavity. However, on the time scale of the LP-CVD process, such losses are found to be negligible, or at least small enough. The side openings of the cavity allow process gases to diffuse into the cavity to allow graphene growth.

[0018] Furthermore, it is hypothesized that the roughness of the opposing surface influences the chemical reactions occurring during the CVD process. The roughness of the surface is hypothesized to influence 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)adsorption onto the exposed surface.

[0019] Therefore, the distance between the exposed surface and the opposing surface, and possibly also the roughness of the opposing surface, will affect the reaction during CVD and the resulting film formed.

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

[0021] Thus, the holder provides an inlet path for the precursor gas.At the same time, as described above, the size of the cavity is designed so that the metal atoms have a high probability of sublimating back to the exposed surface rather than escaping from the cavity.

[0022] The second surface can advantageously be formed by a plurality of bosses protruding from the main body of the holder, the main body including the first surface. Preferably, three bosses are provided, thereby providing stability to the substrate. Alternatively, other forms of support elements can be provided that protrude from the main body and form a support surface for the substrate. Importantly, the second surface forming the support on which the substrate rests during CVD processing is at a well-defined distance from the opposing surface. Preferably, the exposed surface of the substrate is substantially parallel to the opposing surface.

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

[0024] The at least one edge formed by the third surface prevents or limits movement of the substrate, in particular in a horizontal direction, ie in a direction parallel to the opposing surface.

[0025] The second and third surfaces (ie, the bosses and edges) are preferably substantially evenly distributed around the perimeter of the opposing surfaces.

[0026] The holder may comprise or be formed from quartz.Thus, the opposing surface may be a quartz surface.

[0027] Quartz is commonly used in a variety of applications in semiconductor manufacturing and processing. Quartz has many advantages, including high availability, available at relatively low cost in the form and size of semiconductor wafers. It is also relatively easy or at least simple to machine. Processing such as sandblasting can be used to remove material in batches, for example to preform a quartz body. Subsequently, other processes (such as laser micromachining) can be applied to form the holder with high precision and / or provide a smooth surface.

[0028] Furthermore, quartz has a low coefficient of thermal expansion, so even at the high temperatures applied during the LP-CVD process, stresses and strains in the quartz body will be low. It has been observed that quartz is able to withstand a high number of temperature cycles up to the temperatures used in graphene production by CVD, for example up to about 1000°C, followed by cooling to room temperature. Thus, the holder presented herein can be reused over many cycles of CVD processing.

[0029] The holder may be a unitary structure. That is, the opposing surface, the second surface, and the third surface may be formed by machining a quartz body and formed as a single piece from the quartz body.

[0030] Alternatively, the retainer may comprise: - a body comprising the first surface, wherein the first surface comprises the opposing surface and a groove at least partially surrounding the opposing surface; and - a set of support elements configured to be positioned in the groove, the support elements forming the second surface and the third surface.

[0031] The support elements may be provided in various sizes, allowing the holder to support substrates of different sizes.

[0032] Further alternatively, the retainer may comprise: a body comprising the first surface, wherein at least a portion of the first surface forms the opposing surface, a set of first cutouts, and a set of second cutouts offset from the first cutouts; and a set of first support elements configured to be positioned in the first cutouts, the first support elements defining the second surface; and A set of second support elements are configured to be positioned in the second cutouts, the second support elements defining the third surface.

[0033] The first support elements and the second support elements are preferably substantially evenly distributed along the circumference of the opposing surfaces.

[0034] The first support element and the second support element form a single support element for supporting or carrying the exposed substrate and for limiting lateral movement of the exposed substrate. In embodiments where the holder is not formed as a unitary structure but is formed from separate support elements, by separating these two functions, manufacturing complexity and cost can be reduced compared to a case where the same support element is used 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 typically 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 growing graphene thereon. This has been found to provide a substrate that is easily manipulated, enabling the formation of large-area, high-quality graphene.

[0036] However, the thermal expansion coefficient of sapphire differs from that of quartz, which is the preferred material for the holder. Therefore, the substrate will experience different thermal expansion than the holder, meaning the substrate will expand more. This can be addressed by adjusting the dimensions of the holder, particularly the position of the bosses and edges, as described in the following paragraphs.

[0037] Preferably, the holder may comprise edges, wherein the edges are positioned to allow thermal expansion of the substrate during the CVD process while still providing a mechanical interface between the edges and the circumferential edge of the substrate.

[0038] The mechanical interface relates to (ie can be implemented as) the distance between these edges and the circumferential edge of the substrate. It can also be called "play" or mechanical "play".

[0039] That is, the position and size of the second surface and the third surface are preferably determined to allow thermal expansion of the substrate during CVD processing without the substrate being clamped and / or fixed in the holder. That is, the position and / or size of the boss or other support element forming the second surface are determined so that a certain distance is achieved between the edge formed by the third surface and the lateral edge of the substrate. This distance (also known as clearance) can be designed or calculated so that the substrate is retained in the holder during manipulation (for example, by a robot moving the holder and the substrate thereon between different stations in a system (such as a semiconductor manufacturing plant)) while allowing the substrate to thermally expand due to exposure to high temperatures during the CVD process without being exposed to stress or strain caused by mechanical clamping of the substrate.

[0040] The positions and dimensions mentioned herein above may be set by designing the holder to correspond to the dimensions of the substrate(s) to be supported by the holder.

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

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

[0043] Thus, in summary, according to a first aspect, a substrate holder is provided that performs multiple functions, including supporting a substrate and forming an opposing surface. The holder facilitates a simple manner of implementing the holder in a substrate CVD processing system for forming a graphene layer, as well as in other types of semiconductor processing.

[0044] The holder enables an easy and quick positioning of the substrate on the holder at a well-defined and highly accurate distance from the counter surface.

[0045] Furthermore, the shape and size of the holder can be advantageously determined to allow it to be manipulated by a conventional wafer handling robot used in semiconductor manufacturing. In particular, the holder is formed to be held by a robot arm of a conventional wafer handling robot, to be assembled in a storage rack (such as a wafer cassette), and to be positioned and raised / lowered by lift pins and other substrate positioning mechanisms provided in a process chamber, transfer chamber, and / or storage chamber in a (vacuum) system of a semiconductor manufacturing plant.

[0046] According to a second aspect, there is provided a stack comprising a substrate comprising an exposed surface and the holder of the first aspect, the substrate being supported on the second surface by the holder, wherein the exposed surface faces the opposing surface.

[0047] As described herein above, the size and form of the holder are advantageously determined to allow manipulation by conventional semiconductor wafer handling robots. The holder can be provided with elements as are known in the art of semiconductor manufacturing, thereby allowing the holder to be held and moved by the arms of such robots. This enables the stack formed by the holder and substrate to be implemented and used in existing processing systems and facilities (such as semiconductor manufacturing plants).

[0048] As described above with respect 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 size of a semiconductor wafer.

[0049] According to a third aspect, there is provided a method of manufacturing a holder for holding a substrate, the method comprising: - providing a body having a first surface; - forming an opposing surface on the first surface; - forming a second surface, the second surface being substantially parallel to the counter surface and arranged at a distance d from the counter surface, the second surface being configured to support the substrate; - forming a third surface arranged at an angle to the second surface to form an edge for limiting movement of the substrate; The step of forming the opposing surface includes: a first machining step for forming a distance d between the second surface and the portion of the first surface that is to form the counter surface; - a second machining step applied to the portion of the first surface, the second machining step consisting in reducing the roughness of the portion of the first surface obtained after the first machining step.

[0050] The first processing step may comprise a material removal technique, such as sandblasting, whereby a cavity may be formed in the body.

[0051] The second processing step may comprise a polishing process, for example laser patterning, such as 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 holder for holding a substrate, the method comprising: - providing a body having a first surface; - forming an opposing surface on the first surface; - forming a second surface, the second surface being substantially parallel to the counter surface and arranged at a distance d from the counter surface, the second surface being configured to support the substrate; - forming a third surface arranged at an angle to the second surface to form an edge for limiting movement of the substrate; The step of forming the opposing surface includes: - forming a groove at least partially surrounding the portion of the first surface; - placing a plurality of support elements in the groove, each of the support elements comprising the second surface, and at least one of the support elements further comprising the third surface.

[0054] By the method of the fourth aspect, the opposing surface may be formed from a substantially unmachined surface of the quartz material without applying a material removal technique to the portion of the first surface that forms the opposing surface.

[0055] Machining, for example according to the first machining step and finally the second machining step described in relation to the method of the third aspect, may only be required for forming the recess in which the support element is located and / or mounted.

[0056] The support element may be permanently or removably positioned in the groove.The support elements may be provided in different sizes to help the holder be able to accommodate substrates of different sizes.

[0057] The holder manufactured by any of the methods according to the third and fourth aspects may advantageously be the holder according to the various embodiments of the first aspect.

[0058] In summary, the present invention relates to a holder for holding graphene growth substrates processed 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 there into a processing chamber. In the processing chamber, graphene is grown on these wafers using a high-temperature CVD process. When using Cu as the exposed surface, the temperature during CVD is typically between 800°C and 1088°C. When using Ni as the exposed surface, the temperature is typically between 600°C and 1200°C. The wafers are then unloaded into a load lock and subsequently into a cassette.

[0059] Graphene is preferably grown on an epitaxial sapphire substrate, with between 500nm and 2000nm of Cu deposited onto the sapphire. However, copper undergoes significant evaporation at typical graphene growth temperatures. To prevent Cu evaporation from the surface, several methods have been implemented in other systems (tube furnaces, rather than box-to-box systems), such as placing the Cu foil in an enclosure, folding the copper foil, or providing an opposing surface.

[0060] According to the present disclosure, opposing surfaces having multiple functions simultaneously are implemented. This embodiment may preferably be a quartz wafer machined to support a sapphire / Cu substrate that sits upside down on three bosses machined into the quartz substrate.

[0061] The quartz substrate can be a 200 mm quartz wafer mounted on a robot arm, a cassette and lift pin mechanism, and a heater in the process chamber. Simultaneously, the structure of the boss prevents the wafer from shifting while the holder wafer stack moves on the robot. The distance between the exposed surface and the opposing surface of the substrate is such that net evaporation of the epitaxial metal layer from the exposed surface is negligible. This distance (i.e., the cavity depth) prevents metal atoms (such as copper) from evaporating from the substrate because most of the copper is redeposited without being lost.

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

[0063] The term "substrate" is understood to mean an element provided with a surface on which a graphene layer or film is to be formed. It may also be referred to as a wafer. BRIEF DESCRIPTION OF THE DRAWINGS

[0064] Further features and advantages of the present invention will become clear from the description of the present invention by way of non-limiting and non-exclusive embodiments. These embodiments should not be construed as limiting the scope of protection. Those skilled in the art will recognize that other alternatives and equivalent embodiments of the present invention may be conceived and put into practice without departing from the scope of the present invention. Embodiments of the present invention will be described with reference to the various figures in these drawings, in which like or identical reference numerals denote like, identical or corresponding parts, and in the drawings:

[0065] FIG. 1 a shows a schematic cross section of a holder for supporting a substrate according to a first embodiment;

[0066] FIG1 b shows a schematic top view of a holder according to a first embodiment;

[0067] FIG2 a shows a cross section of a holder according to a second embodiment;

[0068] FIG2 b shows a schematic top view of the main body of the holder of the second embodiment;

[0069] Figure 3 A cross section of a holder according to a third embodiment is shown.

[0070] 4a, 4b and 4c schematically illustrate features of a retainer according to a fourth embodiment;

[0071] Figure 5 A schematic diagram of a system for chemical vapor deposition is shown. DETAILED DESCRIPTION

[0072] Figure 1A and Figure 1B A non-limiting embodiment of a holder according to a first embodiment is shown. Figure 1A A cross section of a stack formed by a holder 1 carrying a substrate 2 is shown. Figure 1B A top view of the holder 1 is shown, wherein the substrate 2 is indicated by a dashed line.

[0073] According to a first embodiment, the holder 1 is formed of a monolithic structure. As described above, the holder 1 can be formed from a monolithic quartz body. A recess is machined into the quartz body, thereby forming a second surface 5 that forms a boss or support surface for the substrate 2. When the substrate 2 is supported by the holder, a cavity 4 is formed.

[0074] although Figure 1A It might be suggested that the boss 5 and edge 6 are positioned 180° relative to each other, but this is shown primarily to illustrate the concept and preferably the bosses and edges are arranged 120° apart as preferably three of them are provided.

[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 has been formed. The metal film 3 is provided to form an exposed surface having surface properties (such as an atomic lattice) suitable for graphene growth.

[0076] In the cavity, a first surface is formed, thereby forming an opposing surface 8, which is located at a distance d from the second surface formed by the boss 5. The distance d can be formed with high accuracy.

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

[0078] Figure 1B Schematic illustration of a holder according to a first embodiment as seen from above is shown. Figure 1B As can be seen in the figure, preferably three bosses 5 and edges 6 are provided, which are substantially evenly distributed around the opposing surfaces. It can also be seen that one or more inlets 10 are provided for introducing a precursor gas into the cavity 4. Such a precursor gas may typically include methane CH4, ethane C2H6, or other carbon-containing gases.

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

[0080] Advantageously, the holder is dimensioned so that the diameter d of the imaginary circle defined by the edge 6 is e The dimensions are such that even when the substrate undergoes its maximum thermal expansion during the CVD process, there will be a distance (also called clearance or interface) p between the edge of the substrate and the edge 6 .

[0081] Figure 2A and Figure 2B FIG2 shows a holder 20 according to a second embodiment. In contrast to the holder 1 according to the first embodiment, the holder 20 according to the second embodiment is not a unitary structure, but includes a main body 21 and a plurality of support elements 29 arranged in grooves 31 formed in a surface 21s of the main body. The support elements 29 include a plurality of support elements 29 arranged in a groove 31 formed in a surface 21s of the main body. Figure 1A and Figure 1B The second surface or boss 25 and the third surface or edge 26 of the holder 1 are shown corresponding to the boss 5 and the edge 6. The substrate 2 having the epitaxial layer 3 (indicated by the dotted line) is provided to Figure 1A and Figure 1B The holder 1 shown is supported by the holder 20 in a similar manner.

[0082] Figure 2BA schematic top view of the body 21 of the holder is shown. As can be seen, grooves 31 are machined into the surface 21s of the body. Figure 2B The groove 31 is shown as a complete circle around the opposing surface 28 , but the groove 31 is not necessarily provided as a complete circle. Alternatively, the groove 31 may be formed as a plurality of (eg, at least three) semicircles evenly distributed around the opposing surface 28 .

[0083] According to the second embodiment, the opposing surface 28 can be formed as part of the surface 21s of the quartz body without removing material. This can result in a smoother opposing surface 28 than the opposing surface 8 of the first embodiment, which is formed by material removal techniques. It is expected that the smoothness of the opposing surfaces 8, 28 may affect the behavior of atoms and / or molecules present in the cavities 4, 24, particularly the behavior of the atoms and / or molecules when colliding with the opposing surface and the behavior resulting from the collision with the opposing surface.

[0084] A plurality of support elements 29 may be provided with different dimensions, for example different dimensions of the second surface area 25 , thereby enabling substrates of different sizes to be accommodated on the holder.

[0085] Figure 3 FIG. 4 shows a schematic cross section of a retainer 40 according to a third embodiment. Figure 2A and Figure 2B The holder of the second embodiment shown has many similarities and therefore will not be described in full detail herein. Similar to the holder 20 of the second embodiment, the holder 40 is not monolithic but is formed by 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. an edge and a boss. The at least one support element 49 is arranged in a groove 51 formed in the surface 41s of the body. Thus, the edge 46 of the support element 49 forms an edge that limits the lateral movement of the substrate 2. In addition, additional support elements 52 are provided, thereby forming a second surface on which the substrate 2 rests. Although Figure 3 It is indicated that the holder 40 comprises one support element 46 and three additional support elements 52, but these support elements can be provided in a different number, as long as the substrate rests on the holder by means of gravity and a well-defined, highly accurate distance is formed between the exposed surface 3 of the substrate and the counter surface 48.

[0086] Figure 4A 、 Figure 4B and Figure 4C FIG. 2 shows a schematic diagram of a holder 200 according to a fourth embodiment. Figure 2A and Figure 2BThe concept of the second embodiment shown mainly differs in that the function of (horizontally) supporting the exposed substrate 2 and the function of constraining the lateral movement or displacement of the substrate 2 are separated and implemented by two different types of support elements: a first support element 241 and a second support element 242, respectively.

[0087] Figure 4A There is shown a schematic top view of the holder body 210. As can be seen, the holder body is provided with three cutouts 310 formed in its upper surface for receiving the first support element 241 and three additional cutouts 320 also formed in its upper surface for receiving the second support element 242.

[0088] As can be seen, the first and second cutouts 310, 320 are all substantially evenly distributed around the circumference of the opposing surfaces.Preferably, the first and second cutouts, and hence the first and second support elements 241, 242, are offset relative to each other.

[0089] exist Figure 4A In the illustrated embodiment, the holder is configured to support an exposed substrate 2 having a diameter corresponding to (i.e., identical to) the diameter of the holder's body 210. This means that the portion of the second support element 242 that fits into the second cutout 320 will protrude laterally outside the holder's body 210 with its thicker portion 242-1. However, the second support element can be positioned so as not to interfere with robotic manipulation of the holder 200.

[0090] Figure 4B A side view of a first support element 241 is schematically shown. The first support element 241, which may be formed as a rectangular or cubic block, is positioned within a cutout 310 provided in the holder body 210. The height of the first support element 241, combined with the depth of the cutout 310, defines a distance d between an opposing surface 280 formed by the upper surface of the body 210 and an upper surface 250 of the first support element, which forms the second surface. Thus, when carrying an exposed substrate, the first support element 241, together with the first cutout 310, defines the cavity depth of the reaction cavity formed in the holder.

[0091] Because the first support element 241 and the first notch 310 together define the cavity depth (i.e., the distance between the exposed surface and the opposing surface), the first support element and the first notch should be manufactured with high precision. In particular, their horizontal surfaces should be smooth, for example, to provide a surface with low roughness. The first support element can advantageously be machined using material removal or polishing techniques (e.g., laser micromachining).

[0092] Figure 4CSecond support element 242 is schematically shown in a side view. The second support element can be formed substantially in an L-shape, with the thicker portion 242-1 defining a third surface 260 configured to delimit or limit lateral movement of exposed substrate 2 in the same manner as described above with respect to the first and second embodiments. The thickness of thicker portion 242-1 of each second support element 242 (defining the vertical dimension of third surface 246) is high enough to adequately limit lateral movement of exposed substrate 2. The depth of second cutout 320, together with the thickness of thinner portion 242-2 of support element 242, is such that the distance between the upper surface of portion 242-2 and opposing surface 280 is preferably less than the distance d between second surface 250 and opposing surface 280, such that exposed substrate 2 is fully supported by second surface 250 and, therefore, the exposed surface is a well-defined distance from opposing surface 280. At most, it can be flush with second surface 250.

[0093] Therefore, the second support element 242 is not responsible for setting the cavity distance. Therefore, the second support element can be manufactured with lower accuracy than the first support element, as the dimensional accuracy of the second support element, in particular the requirements for low surface roughness of the second support element, is lower than that of the first support element. Therefore, the second support element 242 can be manufactured using material removal techniques (such as sandblasting).

[0094] Therefore, separating the function of supporting the substrate and the function of limiting lateral displacement of the substrate can make the process of manufacturing the holder less complicated.

[0095] Figure 5 A schematic top view of an LP-CVD system is shown, which can be any conventional LP-CVD system. The system includes a load lock 52 (also known as a transfer chamber and / or parking chamber) that enables wafers to be transferred between a wafer cassette 54 and a CVD process chamber 56 via the load lock 52. Wafers can be moved between the cassette, an intermediate location in the load lock, and the process chamber by a robot 58 (also known as a wafer handling robot).

[0096] The process 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, a gas inlet, a vacuum pump, etc. Such components are described in WO 2014 / 033282 A1.

[0097] As can be understood from the above, the holders according to the various embodiments described herein above have dimensions corresponding to semiconductor wafers and can therefore be positioned in a wafer box 54, lifted and moved by a robot 58, and positioned on lift pins and / or other wafer carrier devices known in the art that are provided in a processing chamber 56.

[0098] Thus, it can be seen from the above that the holder according to the present disclosure forms a robust passive support for a substrate to be exposed to an LP-CVD process, in particular for forming a graphene layer, wherein the design of the holder provides a well-defined distance between the exposed surface of the substrate and the opposing surface of the holder. Thus, net evaporation of metal atoms (e.g., copper) from the exposed surface can be prevented or at least limited. Furthermore, the holder has a shape, weight, and dimensions similar to conventional semiconductor wafers and wafer carriers, thereby enabling the stack formed by the holder and substrate to be used in existing low-pressure chemical vapor deposition (LP-CVD) systems and other semiconductor manufacturing facilities without substantial modification or alteration.

[0099] Therefore, the present invention provides a passive way to prevent Cu evaporation by creating an opposing surface (herein referred to as an opposing surface) at a defined distance from the surface of the epitaxial metal layer of the substrate.

[0100] One could envision mechanically approaching a movable counter surface to the wafer surface before heating the surface, but this would mean designing a system with movable parts and micron precision capable of functioning in thermal cycles around 1000° C. By doing this in a passive manner as described herein, the inventors circumvent having to address this problem.

[0101] At the same time, the structure of the holder has been machined into the quartz wafer, which allows the stack (quartz holder + sapphire / Cu) to be handled in a conventional manner on a robot arm and stored in a cassette. The cassette can be a commercially available cassette of the type selected with slots of a size that allows handling the stack formed by the holder and substrate.

[0102] The retainer structure is designed to accommodate the difference in thermal expansion between quartz and sapphire. Since sapphire expands more than quartz, space is built into the quartz structure to allow for expansion of the sapphire substrate. At the same time, the sapphire cannot move beyond the required amount to accommodate thermal expansion, maintaining its proper position. If the fit is too precise, the sapphire could crack due to thermal expansion.

[0103] Quartz is a preferred material because it has a low coefficient of thermal expansion (CTE). Therefore, thermal cycling of quartz at 1000°C does not induce significant stress in the material, and the material is more tolerant to variations in thermal uniformity, which can induce additional stress that can lead to material cracking. Quartz does not interfere with the graphene growth process. Furthermore, it is readily and inexpensively available in high-purity wafer form.

[0104] It will be clear to those skilled in the art that the scope of the present invention is not limited to the examples discussed above, but that several modifications and variations may be made thereto without departing from the scope of the invention as defined in the appended drawings. Although the present invention has been illustrated and described in detail in the drawings and the specification, such illustration and description are to be considered illustrative or exemplary and not restrictive. The present invention is not limited to the disclosed embodiments, but encompasses any combination of the disclosed embodiments that may provide advantages.

[0105] For example, although not described in detail above, the holder can be configured to support more than one substrate. That is, according to the embodiments described herein, the holder can be provided with multiple substrate support regions, each substrate support region including a cavity, an opposing surface, a second surface, and a third surface, or a boss and an edge. In other words, from a top view, the multiple substrates supported by the holder can be arranged to form part of a hexagonal surface lattice arrangement or an FCC surface lattice structure.

[0106] By studying the drawings, the description and the appended claims, those skilled in the art can understand and implement variations of the disclosed embodiments when practicing the claimed invention. In the description and the claims, the word "comprising" does not exclude other elements, and the indefinite article "a" or "an" does not exclude a plurality. In fact, it should be interpreted as meaning "at least one". The mere fact that certain features are listed in dependent claims that are different from each other does not indicate that a combination of these features cannot be used to advantage. All reference signs in the claims should not be interpreted as limiting the scope of the invention. The features of the above-mentioned embodiments and aspects can be combined unless their combination leads to obvious technical conflicts.

Claims

1. A holder for holding a substrate during a chemical vapor deposition (CVD) process, the holder comprising: - a first surface configured to form an opposing surface relative to the exposed surface of the substrate; a second surface substantially parallel to the counter surface and arranged at a distance d from the counter surface, the second surface being arranged to support the substrate; - a third surface arranged at an angle to the second surface, the third surface forming an edge for limiting the movement of the substrate. 2 . The holder according to claim 1 , the holder being configured such that when the substrate is supported by the holder, a reaction cavity is formed between the exposed surface of the substrate and the opposing surface.

3. A holder according to any one of the preceding claims, wherein At least one inlet is disposed between the first surface and the second surface, the inlet configured for introducing one or more precursor gases into the holder.

4. A holder according to any one of the preceding claims, wherein The second surface is formed by a plurality of bosses protruding from a main body of the holder, the main body including the first surface.

5. The holder according to claim 4, wherein The edge protrudes from at least one of the bosses.

6. A holder according to any one of the preceding claims, wherein The holder comprises quartz.

7. A holder according to any one of the preceding claims, wherein The retainer is a one-piece structure.

8. The holder according to any one of claims 1 to 6, wherein: The retainer includes: - a body comprising the first surface, wherein the first surface comprises the opposing surface and a groove at least partially surrounding the opposing surface; - a set of support elements configured to be positioned in the groove, the support elements forming the second surface and the third surface.

9. The holder according to any one of claims 1 to 6, wherein: The retainer includes: - a body comprising the first surface, wherein at least a portion of the first surface forms the opposing surface, a set of first cutouts and a set of second cutouts, the second cutouts being offset from the first cutouts; and - a set of first support elements configured to be positioned in the first cutouts, the first support elements defining the second surface; and - a set of second support elements configured to be positioned in the second cutouts, the second support elements defining the third surface.

10. A holder according to any one of the preceding claims, wherein The distance d is in the range of 50 μm to 250 μm, preferably in the range of 100 μm to 200 μm.

11. A holder according to any one of the preceding claims, comprising a plurality of edges, wherein The edges are positioned to allow thermal expansion of the substrate during the CVD process while still providing a mechanical interface between the edges and the circumferential edge of the substrate.

12. A stack comprising a substrate comprising an exposed surface and a holder according to any one of the preceding claims, the substrate comprising an exposed surface, the holder supporting the substrate on the second surface, wherein the exposed surface faces the opposing surface.

13. The stack according to claim 12, wherein: The substrate is a sapphire substrate provided with an epitaxial metal layer, and the epitaxial metal layer forms the exposed surface.

14. The stack according to claim 12 or 13, wherein: The substrate has the size of a semiconductor wafer.

15. A method for manufacturing a holder for holding a substrate, the method comprising: - providing a body having a first surface; - forming an opposing surface on the first surface; - forming a second surface, the second surface being substantially parallel to the counter surface and arranged at a distance d from the counter surface, the second surface being configured to support the substrate; - forming a third surface, the third surface being arranged at a certain angle to the second surface, the third surface forming an edge for limiting movement of the substrate; The step of forming the opposing surface includes: a first machining step for forming a distance d between the second surface and the portion of the first surface that is to form the counter surface; - a second machining step applied to the portion of the first surface, the second machining step consisting in reducing the roughness of the portion of the first surface obtained after the first machining step.

16. A method for manufacturing a holder for holding a substrate, the method comprising: - providing a body having a first surface; - forming an opposing surface on the first surface; - forming a second surface, the second surface being substantially parallel to the counter surface and arranged at a distance d from the counter surface, the second surface being configured to support the substrate; - forming a third surface, the third surface being arranged at a certain angle to the second surface, the third surface forming an edge for limiting movement of the substrate; The step of forming the opposing surface includes: - forming a groove at least partially around the portion of the first surface that is to form the opposing surface; - placing a plurality of support elements in the groove, each of the support elements comprising the second surface, and at least one of the support elements further comprising the third surface.

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