Source: http://patents.com/us-10017876.html
Timestamp: 2019-04-21 09:15:52
Document Index: 790054148

Matched Legal Cases: ['Application No. 102119218', 'Application No. 09831089', 'Application No. 201510494081', 'Application No. 201510494081', 'Application No. 61', 'Application No. 20060021574', 'Application No. 20080173735']

US Patent # 1,001,7876. Chemical vapor deposition flow inlet elements and methods - Patents.com
United States Patent 10,017,876
Belousov , et al. July 10, 2018
Belousov; Mikhail (Plainsboro, NJ), Mitrovic; Bojan (Somerset, NJ), Moy; Keng (Basking Ridge, NJ)
Family ID: 42231384
14/150,091
US 20140116330 A1 May 1, 2014
12631079 Nov 6, 2012 8303713
Current CPC Class: C23C 16/45574 (20130101); C23C 16/45578 (20130101); C30B 25/14 (20130101); C23C 16/4584 (20130101)
Current International Class: C30B 25/14 (20060101); C23C 16/455 (20060101); C23C 16/458 (20060101)
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This application is a divisional of U.S. patent application Ser. No. 13/606,130, filed on Sep. 7, 2012, which is a divisional of U.S. patent application Ser. No. 12/631,079, filed Dec. 4, 2009 and now U.S. Pat. No. 8,303,713, which application claims the benefit of the filing date of U.S. Provisional Patent Application No. 61/201,074, filed Dec. 4, 2008, the disclosures of which are hereby incorporated herein by reference.
1. A flow inlet element for a chemical vapor deposition reactor comprising: a plurality of elongated elements extending parallel to one another and mechanically attached to one another so that the elongated elements cooperatively define a plate having upstream and downstream sides, the plate having base inlet openings extending from the upstream side to the downstream side between adjacent ones of the elongated elements, at least some of the elongated elements defining one or more gas distribution channels; a structure defining one or more gas spaces upstream of the plate and communicating with the base inlet openings; additional gas inlets communicating with the gas distribution channels, the additional gas inlets being open to the downstream side of the plate; and elongated diffusers extending along at least some of the elongated elements and projecting downstream from the elongated elements, at least some of the additional gas inlets extending through the diffusers from the gas distribution channels to downstream edges of the diffusers remote from the gas distribution channels.
2. A flow inlet element as claimed in claim 1 wherein at least some of the elongated elements are tubular.
3. A flow inlet element as claimed in claim 2 further comprising one or more manifolds connected to the tubular elements at ends of the tubular elements and communicating with the gas distribution channels.
4. A chemical vapor deposition reactor comprising; (a) a reaction chamber having upstream and downstream directions; (b) a carrier support adapted to support a wafer carrier at a carrier location within the reaction chamber for rotation about an axis extending in the upstream and downstream directions; (c) a flow inlet element mounted to the chamber upstream of the carrier location, the inlet element having a gas distribution surface extending in horizontal directions perpendicular to the downstream direction, the flow inlet element having a plurality of elongated gas inlets for discharging gases into the chamber, the elongated gas inlets extending parallel to one another in a first one of the horizontal directions, the elongated gas inlets including a plurality of first gas inlets for discharging a first reactive gas, a plurality of second gas inlets for discharging a second reactive gas, and a plurality of third gas inlets for discharging a carrier gas substantially devoid of the first and second reactive gasses and substantially nonreactive with first and second reactive gasses, the gas inlets being spaced apart from one another in a second one of the horizontal directions perpendicular to the first horizontal direction and interspersed with one another so that at least some of the first and second gas inlets constitute pairs of adjacent inlets and at least some of the third gas inlets are disposed between the first and second gas inlets of at least some of the pairs, wherein the axis of rotation of the wafer carrier passes through the flow inlet element so that the first and second reactive gasses, once discharged from the first and second gas inlets to a point proximate the wafer carrier, are impelled into rotational flow and mixed with one another to deposit a substance on a wafer held by the wafer carrier, and wherein the flow inlet element includes elongated diffusers extending in the first horizontal direction and projecting downstream from the third gas inlets, and wherein the first and second gas inlets are disposed in the diffusers.
5. A reactor as claimed in claim 4 wherein a corresponding one of the third gas inlets is disposed between the first and second gas inlet of every one of the pairs of adjacent first and second gas inlets.
6. A chemical vapor deposition reactor comprising; (a) a reaction chamber having walls and upstream and downstream directions; (b) a carrier support adapted to support a wafer carrier at a carrier location within the reaction chamber for rotation about an axis extending in the upstream and downstream directions; (c) a flow inlet element mounted to the chamber upstream of the carrier location, the inlet element having a gas distribution surface extending in horizontal directions perpendicular to the downstream direction, the flow inlet element having a plurality of first gas inlets for discharging a first reactive gas, a plurality of second gas inlets for discharging a second reactive gas, and a plurality of third gas inlets for discharging a carrier gas substantially devoid of the first and second reactive gasses and substantially nonreactive with first and second reactive gasses, the first, second and third gas inlets extending to first, second and third radial distances from the axis, respectively, the third radial distance being greater than at least one of the first and second radial distances, the third gas inlets configured so that the carrier gas, once discharged from the third gas inlets, forms a curtain that is configured to keep at least one of the first and second reactive gasses isolated from the walls of the reaction chamber, wherein the axis of rotation of the wafer carrier passes through the flow inlet element so that the first and second reactive gasses, once discharged from the first and second gas inlets to a point proximate the wafer carrier, are impelled into rotational flow and mixed with one another to deposit a substance on a wafer held by the wafer carrier, and wherein the flow inlet element includes elongated diffusers projecting downstream from the gas distribution surface, and at least some of the first or second gas inlets are disposed in the diffusers.
7. A reactor as claimed in claim 6 wherein the first and second radial distances are substantially equal to one another.
Chemical vapor deposition involves directing one or more gases containing chemical species onto a surface of a substrate, typically a flat wafer, so that the chemical species react and form a deposit on the surface. For example, compound semiconductors can be formed by epitaxial growth of the semiconductor material on a crystalline wafer. Semiconductors referred to as III-V semiconductors commonly are formed using a source of a Group III metal such as gallium, indium, aluminum, and combinations thereof and a source of a Group V element such as one or more of the hydrides or of one or more of the Group V elements such as NH.sub.3, AsH.sub.3, or PH.sub.3, or an Sb metalorganic such as tetramethyl antimony. In these processes, the gases are reacted with one another at the surface of a wafer, such as a sapphire wafer, to form a III-V compound of the general formula In.sub.xGa.sub.yAl.sub.zN.sub.AAs.sub.BP.sub.CSb.sub.D where X+Y+Z=approximately 1, and A+B+C+D=approximately 1, and each of X, Y, Z, A, B, C and D can be between 0 and 1. In some instances, bismuth may be used in place of some or all of the other Group III metals.
In certain processes, commonly referred to as a "halide" or "chloride" process, the Group III metal source is a volatile halide of the metal or metals, most commonly a chloride such as GaCl.sub.2. In another process, commonly referred to as metalorganic chemical vapor deposition or "MOCVD," the Group III metal source is an organic compound of the Group III metal as, for example, a metal alkyl.
One form of apparatus which has been widely employed in chemical vapor deposition includes a disc-like wafer carrier mounted within the reaction chamber for rotation about a vertical axis. The wafers are held in the carrier so that surfaces of the wafers face in an upstream direction within the chamber. While the carrier is rotated about the axis, the reaction gases are introduced into the chamber from a flow inlet element upstream of the carrier. The flowing gases pass downstream toward the carrier and wafers, desirably in a laminar plug flow. As the gases approach the rotating carrier, viscous drag impels them into rotation around the axis, so that in a boundary region near the surface of the carrier, the gases flow around the axis and outwardly toward the periphery of the carrier. As the gases flow over the outer edge of the carrier, they flow downwardly toward exhaust ports disposed below the carrier. Most commonly, this process is performed with a succession of different gas compositions and, in some cases, different wafer temperatures, to deposit plural layers of semiconductor having differing compositions as required to form a desired semiconductor device. Merely by way of example, in formation of light emitting diodes ("LEDs") and diode lasers, a multiple quantum well ("MQW") structure can be formed by depositing layers of III-V semiconductor with different proportions of Ga and In. Each layer may be on the order of tens of Angstroms thick, i.e., a few atomic layers.
Considerable effort has been devoted in the art heretofore to development of flow inlet elements for use in apparatus of this type. Commonly, the flow inlet element has inlets for the reactive gases dispersed over an active, gas-emitting area approximately equal in size to the wafer carrier. Some of these flow inlet elements carry the first reactive gas, such as a mixture of a Group V hydride, whereas others carry the second reactive gas, such as a mixture of a metal alkyl and a carrier gas. These inlets may be formed as tubes extending parallel to the axis of rotation, the inlets are distributed over the downwardly-facing or downstream surface of the flow inlet element. Considerable effort has been devoted in the art heretofore to arranging the inlets in symmetrical patterns. Typically, the first gas inlets are provided in a pattern which has radial symmetry about the axis of rotation of the wafer carrier, or which has at least two perpendicular planes of symmetry crossing one another at the axis of rotation. The second gas inlets have been provided in a similarly symmetrical pattern, interspersed with the first gas inlets. The flow inlet element commonly incorporates complex channel structures for routing the gases to the tubular inlets. Moreover, because the wafers typically are maintained at a high temperature as, for example, about 500.degree. C. to about 1200.degree. C., the flow inlet element must be provided with coolant channels. The coolant channels carry a circulating flow of water or other liquid and thus maintain the temperature of the flow inlet element relatively low, so as to limit or preclude premature reaction of the gases. As disclosed, for example, in U.S. Published Patent Application No. 20060021574 A1, the disclosure of which is hereby incorporated by reference herein, a flow inlet element may be provided with additional structures for discharging flows of a carrier gas devoid of reactive species.
The carrier gas flows isolate the reactive gas flows from one another while the gases are in the vicinity of the flow inlet element. The gases do not mix with one another until they are remote from the flow inlet element. Moreover, discharging the carrier gas flows limits or prevents recirculation of the reactive gases as they exit from the flow inlet element. Thus, the reactive gases do not tend to form undesired deposits on the flow inlet element. As described, for example, in commonly assigned U.S. Published Patent Application No. 20080173735 (now U.S. Pat. No. 8,152,923), the disclosure of which is hereby incorporated by reference herein, recirculation of the discharged gases in the vicinity of the flow inlet element may be reduced by providing blade-like diffusers projecting downstream from the surface of the flow inlet element to guide the gas flows.
One aspect of the invention provides a chemical vapor deposition reactor. The reactor according to this aspect of the invention desirably includes a reaction chamber having upstream and downstream directions, and also desirably includes a carrier support adapted to support a wafer carrier at a carrier location within the reaction chamber for rotation about an axis extending in the upstream and downstream directions. The reactor according to this aspect of the invention preferably has a flow inlet element mounted to the chamber upstream of the carrier location, the inlet element having a gas distribution surface extending in X and Y horizontal directions perpendicular to one another and perpendicular to the downstream direction.
The foregoing features of the apparatus may be similar to those used in reactors sold under the trademarks "TurboDisc" and "Ganzilla" by Veeco Instruments, Inc. of Plainview, N.Y.
A flow inlet element 22 is provided at the upstream end of the reaction chamber. A downstream surface 24 of the flow inlet element faces in the downstream direction, toward the wafer carrier and wafers. The flow inlet element is connected to a source of a first reactive gas 30, such as a Group V hydride, typically in admixture with a carrier gas such as N.sub.2 or H.sub.2. The flow inlet element is also connected to a source 26 of a second reactive gas, such as a metal alkyl, also typically in admixture with a carrier gas. Additionally, the flow inlet element is connected to a source 32 of a carrier gas such as N.sub.2 or H.sub.2, which is not admixed with any reactive gas, and to a coolant circulation device 33.
A gas distribution plate 60 is disposed downstream from the top plate 40 so that plates 60 and 40 cooperatively define a gas distribution chamber 62 between them. The gas distribution chamber 62 communicates with the carrier gas source 32 (FIG. 1), but does not communicate with the first or second gas sections of the manifold. In one embodiment, the flow inlet element 22 comprises a structure defining one or more gas spaces 62 upstream of the gas distribution plate 60 and communicating with the base inlet openings 104.
As best seen in FIG. 4, plate 60 is formed from numerous elongated tubular gas distribution elements 64 and 66 extending parallel to one another. The direction of elongation of the elongated elements 64 and 66 is arbitrarily referred to as the "+X" direction. This direction is a direction perpendicular to the upstream and downstream directions, and perpendicular to the axis 16 of the chamber (FIG. 1). The elongated elements are offset from one another in a "+Y" direction, which is also perpendicular to axis 16 and perpendicular to the +X direction.
Directions perpendicular to the axis 16, including the X and Y directions, are referred to herein as "horizontal" directions inasmuch as axis 16 normally (although not necessarily) extends vertically in the normal gravitational plane of reference. Also, planes which are perpendicular to the axis are referred to herein as horizontal planes. Thus, both top plate 40 and distribution plate 60 extend in horizontal planes. Also, the horizontal direction opposite to the +X direction is referred to herein as the -X direction, and the direction opposite to the +Y direction is referred to herein as the -Y direction, in the conventional manner of a Cartesian coordinate system. The upstream and downstream directions U and D, parallel to axis 16 constitute the third or Z direction of the Cartesian coordinate system.
As seen in FIG. 4, the first and second gas distribution elements 64 and 66 are arranged side by side and are mechanically attached to one another as by welds 102 extending between the sidewalls 94 and 70 of mutually adjacent elements. The upstream walls 94 and 68 of the elements cooperatively define an upstream surface of the plate 60, whereas the downstream walls 72 and 86 cooperatively define the downstream surface of the plate. The welds 102 are arranged only at spaced-apart locations along the lengths of the elements. Thus, slot-like inlet openings 104, referred to herein as "base" inlets, extend through the plate from its upstream surface to its downstream surface, between the adjacent gas distribution elements 64 and 66. The upstream surface of the gas distribution plate 60 confronts the space 62 between plate 60 and top plate 40.
As best seen in FIG. 2, each of the individual gas distribution elements 64 and 66 extends in the X direction across the medial plane 52 which extends perpendicular to the X direction. The elongated inlets defined by the individual gas distribution elements also extend across medial plane 52. In this embodiment, each gas distribution element, and the elongated inlets defined by each gas distribution element, extends across substantially the entire span of the active gas distribution region of the flow inlet element. The first and second gas distribution elements 64 and 66 are not arranged symmetrically with respect to the medial plane 108 extending in the X direction. Rather, the first and second gas distribution elements 64, 66 are arranged within an antisymmetrical or negative-symmetry pattern with respect to medial plane 108. That is, for each first gas distribution element 64 arranged at a positive or +Y difference from medial plane 108, there is a second gas distribution element 66 arranged at the corresponding -Y distance from medial plane 108. For example, first gas distribution element 64a is disposed at distance +Y.sub.a from medial plane 108. Second gas distribution element 66a is disposed at the corresponding, negative distance -Y.sub.a of equal magnitude from the same medial plane. The distance to each gas distribution element is measured to the longitudinal center line of the inlets defined by such element as, for example, the longitudinal center line of slot-like inlets 84 (FIG. 6) or the longitudinal center line of the rows of holes 92 (FIG. 6). In the depiction of FIG. 2, the spaces or base gas inlets 104 between the gas distribution elements are omitted for clarity of illustration.
In operation, a first reactive gas such as a mixture of ammonia or other Group V hydride in admixture with one or more carrier gases such as H.sub.2, N.sub.2 or both is supplied through the first gas section 48 of the manifold and passes into the longitudinal bores 74 (FIG. 5) of the first gas distribution elements 64. The first reactive gas thus issues as a series of elongated, curtain-like streams of gas 111 (FIG. 4) from the inlets 34 defined by the first gas distribution elements 64 and associated diffusers 78. Similarly, a second reactive gas, such as a metal alkyl in admixture with a carrier gas, is supplied through the second gas section 50 (FIG. 2) of the manifold and passes through the interior bore 98 (FIG. 6) of the second gas distribution element 66. The second gas thus issues as rows of streams 113 (FIG. 4) from the inlets 92 defined by the second gas distribution elements and the associated diffusers. These rows of gas streams 113 are interspersed between the streams 111 of the first gas. A carrier gas such as H.sub.2, N.sub.2 or a mixture thereof is introduced into the carrier gas space 62 and passes through the spaces or base openings 104 defined between the gas distribution elements 64 and 66 constituting the plate. The carrier gas thus issues as curtain-like streams 115 interposed between each stream 111 of the first reactive gas and the adjacent rows of streams 113 of the second reactive gas. The streams of gases travel downstream to the vicinity of the wafer carrier 14 and the wafers 18, where they are swept into rotational flow by the rotational motion of the wafer carrier and wafers. The first and second reactive gases react with one another at the wafer surface to form a deposit as, for example, a III-V semiconductor.
The flows of first and second gases are not symmetrical about the medial plane 108 extending in the X direction. If the wafer carrier and wafers were static, this would result in nonuniform exposure of the wafer carrier and wafers to the first and second reactive gases. For example, as schematically depicted in FIG. 7, a wafer carrier 14 is shown with a marker 120 on the carrier provided for purposes of illustration pointing in the +X direction, to the right in FIG. 7. If the wafer carrier were to remain in this orientation, the region shown as dark stripes would be heavily impacted by the first reactive gas, whereas the region shown as light stripes would be more heavily impacted by the second reactive gas. The same pattern of impact areas is shown in FIG. 8, but with the wafer carrier 14 rotated 180.degree. about the central axis 16, so that the indicator 120 points in the opposite or -X direction. The pattern of light and dark stripes in FIG. 8 is the reverse of the pattern in FIG. 7. Thus, as the wafer carrier rotates, the regions which were heavily exposed to the first gas in one orientation of the wafer carrier will be heavily exposed to the second gas in the opposite orientation of the wafer carrier. With continual rotation of the wafer carrier, the exposure pattern becomes uniform as shown in FIG. 9.
In the embodiments discussed above, each elongated gas inlet provides the same mass flow rate of a reactive gas per unit length along its entire length. In a variant, the mass flow rate of the reactive gas per unit length may vary progressively along the length of the elongated gas inlet. This may occur, for example, where a particular elongated gas distribution element receives a gas mixture at only one end, and has appreciable resistance to flow along its length. FIG. 15 schematically depicts the impact pattern 601a of a first reactive gas flowing from such an elongated inlet. In this case, the mass flow rate of the reactive gas from the particular inlet diminishes progressively in the +X direction along the length of the inlet. Thus, the breadth of the area on the wafer carrier impacted by the gas is shown as diminishing in the +X direction. In the arrangement of FIG. 15, the second reactive gas inlets 606 have mass flow rates which diminish in opposite, -X direction. Rotation of the wafer about the central axis will cancel out the differences in the impact patterns. For example, a portion of the wafer which is aligned with portion 603 of impact pattern 601a will be aligned with portion 605 when the wafer carrier rotates one half turn. In yet another arrangement, alternate ones of the first gas inlets may have mass flow rates, and hence impact patterns, which diminish in opposite X directions. The second gas inlets may have a similar arrangement.
The first gas inlets extend only within a region of the gas distribution surface having a first radius R.sub.1 from the central axis 716. Stated another way, the first gas outlets extend to a first radius R.sub.1 from the central axis. The second gas outlets extend to a second radius R.sub.2 from the central axis, which in this embodiment is equal to the first radius R.sub.1. The third gas inlets extend to a radius R.sub.3 which is greater than the first and second radii, and hence greater than R.sub.1 and R.sub.2. In the particular example depicted, the radius R.sub.3 is equal to, or just slightly less than, the interior radius of the reaction chamber at the gas distribution surface. The first and second radii R.sub.1 and R.sub.2 may be approximately equal to the radius of the wafer carrier.
In operation, the gasses issuing from the first and second gas inlets will pass downstream (in the direction along axis 716 toward the viewer in FIG. 16) to the wafer carrier and participate in chemical vapor deposition reactions or other treatment of the wafers carried on the carrier. In the region within first and second radii R.sub.1 and R.sub.2, the carrier gas issuing from the third gas inlets passes downstream between the streams of first and second gasses, and maintains separation between these streams for at least part of the distance from the flow inlet element to the wafer as discussed above. In the gap region G outside of the region occupied by the first and second gas inlets, the carrier gas issuing from the third gas inlets forms a curtain which keeps the reactive first and second gasses isolated from the wall of chamber 710. This minimizes deposition of reaction products on the chamber walls. In particular, recirculation of gases can occur at the upstream end of the chamber where the flow inlet element 722 joins the reactor wall. With the arrangement shown in FIG. 16, any recirculating gases will be composed essentially of the carrier gas, and therefore will not tend to form deposits on the reactor walls or flow inlet element.
The arrangement shown in FIG. 16 may be varied. For example, the first and second radii R.sub.1 and R.sub.2 may differ from one another. One of these radii may be as large as, or even greater than, the third radius R.sub.3. In such an arrangement, the curtain of gas adjacent the reactor wall would include the carrier gas and only one of the reactant gases. Such a curtain would still be effective to suppress deposition at the chamber wall. It is not essential to provide third gas inlets between the first and second gas inlets. For example, the third gas inlets may be provided only in the gap region G. Also, the gas inlets are shown in FIG. 16 as disposed in parallel rows, but other configurations can be used. For example, the first gas inlets can be in the form of a "field" or continuous area, whereas the second gas inlets can be in the form of one or more radial rows.
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