GAS INJECTOR APPARATUS FOR CHEMICAL VAPOR DEPOSITION REACTORS

Abstract: A gas injector apparatus (10) for use in a single-substrate epitaxial chemical vapor deposition reactor. The gas injector (10) of the present invention is adapted to provide a predetermined shaped velocity gas flow profile for the reactant gas flow introduced into the reaction chamber. The gas is supplied through an input into a remote manifold (12), the remote manifold (12) creates a uniform gas flow velocity having a vertical directional vector which is communicated into a plenum chamber (54). The uniform velocity gas flow exiting the plenum chamber (54) communicates with an apertured plate (16) having shutters (22) associated with the apertures (38). The shutters (22) may be adjusted to provide varying sized apertures in the apertured plate (16). The apertures (38) in the apertured plate (16) are adjusted to shape the velocity profile of the uniform velocity gas flow as it passes through the shuttered apertures. The gas continues to flow with a vertical directional vector downwardly to main injector body (20). In the main injector body (20), the vertical directional vector of the shaped velocity profile gas flow is redirected to a horizontal directional vector so that the shaped velocity profile gas flow is directed horizontally into the reaction chamber.

Description: GAS INJECTOR APPARATUS FOR CHEMICAL VAPOR DEPOSITION REACTORS Background of the Invention The present invention relates generally to a gas injector apparatus for use in conjunction with chemical vapor deposition (hereinafter referred to as "CVD") reactors used in processing semiconductor wafers. More particularly, the present invention relates to a gas injector apparatus for use in a single-wafer epitaxial deposition system where stringent control over deposition kinetics and uniformity of the deposited layer is necessary. Conventional CVD reactors are typically classified according to the orientation of the gas flow with respect to the substrate surface. Comrifercial epitaxial deposition into the reaction chamber and flows substantially horizontally across the wafer surface. Finally, in horizontal CVD reactors the wafers are placed horizontally on a susceptor and the reactant gas stream flows horizontally across the wafer surface. Conventional horizontal CVD systems utilize a laminar gas flow to deposit the reactant species on the wafer. Typically, a reactive gas mixture bearing the material to be deposited is introduced into a pre-heated reaction chamber containing the semiconductor substrate on a heated susceptor. As the gas is introduced into the reaction chamber, the laminar gas flow transports the deposition material to the substrate. The deposition material is deposited onto the substrate and, concurrently, depleted from the reactant gas flow. This simultaneous deposition and depletion establishes a concentration gradient across the substrate surface. The depletion of the deposition material from the reactant gas flow invariably leads to non-uniform deposition across the wafer surface due to decreased concentrations of the deposition material in the reactive gas mixture as it flows across the substrate surface. Deposition reaction dynamics are critical to achieving a uniform deposition rate and deposition thickness. The deposition reaction is substantially temperature and flow dependent. Maintaining a uniform gas temperature and flow profile is important for achieving a substantially uniform deposition " rate onto the substrate surface. In conventional CVD reactors, reactant gas typically flows between the heated susceptor and wafers and the cold reactor wall. Deposition uniformity is determined by the resulting thermal and mass transport boundary layers in the gas. U.S. Patent No. 4,499,853 issued February 19, 1985 to Edward A. Miller discloses a gas distributor tube for a CVD apparatus which provides a gas stream substantially free of turbulence. As exemplified by U.S. Patent No. 4,499,853, those skilled in the art deem the provision of a uniform velocity gas flow is desirable to increase deposition uniformity. Thus, in conventional horizontal CVD systems the state of the art teaches uniformity of both temperature and flow velocity across the wafer surface. The present invention provides a gas injector apparatus which, shapes a uniform velocity gas flow in order to present substantially uniform concentration gradients of the reactive species in the gas flow to all areas of the wafer surface. Presentation of a shaped velocity gas flow to the curvilinear leading and trailing edges of the wafer increases thickness uniformity of the deposited material across the wafer surface. SUMMARY OF THE INVENTION Accordingly, it is a broad object of the present invention to provide a gas injector apparatus for improving deposition uniformity in single-wafer CVD epitaxial reactors. It is another object of the present invention to provide a gas injector apparatus which creates a uniform velocity flow of reactant gas within the apparatus. It is another object of the present invention to provide a gas injection apparatus for a chemical vapor deposition reactor capable of shaping the velocity profile of a uniform velocity flow of reactant gas as it flows across the substrate surface. It is another object of the present invention to provide a gas injector apparatus which creates a uniform gas flow, shapes the velocity profile of the gas flow and exposes the wafer surface area to substantially uniform concentration gradients of the reactant species in the gas flowχ It is still another object of the present invention to provtj.de a gas injector apparatus for a chemical vapor deposition reactor which provides a uniform and controlled co'iqentration of the deposited material. -. , * '!!;CThese and other objects, features and advantages of the- present invention will become more apparent from the following more detailed description of the preferred embodiments of the present invention with reference to the accompanying Figures in which like elements are identified by like reference numerals. Brief Description of the Drawings Figure 1 is a schematic representation of a top view of a prior art CVD reactor for injecting a uniform gas flow into a multi-substrate processing system. Figure 2 is a sectional top view illustrating disparate flow path distances across the substrate surface in a single substrate CVD reactor. Figure 3 is a sectional top view illustrating a gas injector for introducing reactant gas flow having a predetermined shaped velocity profile in a single substrate CVD epitaxial deposition reactor. Figure 4 is an exploded perspective view of the gas injector apparatus of the present invention. Figure 5 is a front elevational partial cross- sectional view of a base portion of the gas injector apparatus of the present invention. Figure 6 is a side elevational cross-sectional view taken along line 6-6 of Figure 5. Figure 7 is a top elevational view of the base portion of the gas injector apparatus of the present invention. Figure 8 is a side elevational partial cross-sectional view of a remote manifold portion of the gas injector apparatus of the present invention. Figure 9 is a side elevational partial cross-sectional view taken along line 9-9 of Figure 8. Detailed Description of the Preferred Embodiment Figure 1 represents a CVD system 11 for multi- substrate 23 processing. The reactor 11 includes a reactant gas input 13 which supplies reactant gases into a hollow interior 17 of the reactor 11. Gas flow 25 is injected into an input portion 13 of the reactor 11 and enters the hollow interior 17 at a substantially uniform velocity and with a substantially laminar profile. Gas flow 25 passes across susceptor 21 and substrates 23 with a uniform velocity and deposits the reactant species carried in the gas flow 25 upon the substrates 23. After deposition of the reactant species onto the substrates 23 and the depletion of the reactant species from the gas flow 25, the gas flow 25 is withdrawn from the hollow interior 17 of the reactor 11 by an exhaust port 15. The uniform velocity of gas flow 25 is diagram atically represented by equal length arrows represent uniform magnitudes of velocity across the width of the hollow interior 17 of reactor 11. Where there are multiple substrate, injecting the gas flow 25 into the hollow interior 17 and flowing the gas across the surface of each substrate has achieved relatively uniform deposition of the reactant species onto the substrates 23. In single-substrate epitaxial deposition reactors, however, injection of a uniform velocity gas flow fails to achieve acceptable uniformity of the deposited layers. The introduction of a uniform velocity gas flow 25 in a single- substrate reactor is illustrated in Figure 2. It will be appreciated, by those skilled in the art, that as the uniform velocity gas flow 25 passes over the generally circular substrate 33 it encounters different substrate surface areas across the width of the substrate. As represented by the designations "d.,* 1 , "d 2 ", and "d 3 " the curved profile of the substrate 33 requires the gas flow 25 to traverse varying distances. It will be observed that the gas flow 25 must pass over a greater distance "d_." at the central area of the substrate, whereas the gas flow 25 only passes over relatively shorter distances "d 2 π and "d 3 " toward the lateral edges of the substrate. The reactant gas flow 25 is, therefore, exposed to differing substrate surface areas which decrease toward the lateral surfaces of the substrate. Where the gas flow 25 is introduced into the hollow interior 15 with a uniform velocity profile, the gas flow 25 will pass through each of distances "d.,", "d 2 ", and "d 3 " within the same time interval. The greater central surface area "d," causes a more rapid depletion of the reactant species and establishes unequal concentration gradients of the reactant species in the gas flow across the horizontal aspect of substrate 33. The unequal concentration gradients cause, in turn, non-uniform deposition of the reactant species onto the substrate 33. After depletion of the reactant species from the gas flow 25, the spent gas is withdrawn from gas outlet 15 via gate or port 29. Figure 3 illustrates the shaped velocity gas flow achieved by the present invention. Gas injector 2 7 supplies the reactant gas at input 13 of the reactor 11. A gas flow 37 is introduced into the hollow interior 17 of the reactor 11 having a predetermined shaped velocity profile, as represented by waveform envelope 35. As illustrated in Figure 3, gas flow 27 is represented by varying sized arrows representing different velocity magnitudes. It will be seen that the gas flow 37 is shaped to have a greater velocity toward the center of the envelope 35 and a lesser velocity toward the lateral edges of the substrate. The shaped velocity profile causes the gas flow 37 to pass over distances "d., 111 , "d 2 ,π , and t, d 3 I " in different time intervals. By selectively exposing area "d 1 '" and areas "d-" 1 and "d- j 1 " to differing gas flow velocities, the more rapid depletion of the reactant species in the central area "d 1 ,H is compensated for by the increased velocity of the gas flow in that area. Thus, the shaped velocity gas flow profile delivers greater quantities of the reactant species to the larger central surface area "d.'" of the substrate. The relative smaller areas "d 2 l!I and "d 3 IH are exposed to lesser gas flow velocities and, therefore, receive lesser quantities of the reactant species. After deposition, the spent gas exits outlet 15 via gate or port 29. The shaped velocity gas flow profile of the present invention is achieved by a gas injector apparatus as illustrated, in its preferred embodiment, in Figures 4-9. In accordance with the preferred embodiment of the present invention there is provide a gas injector apparatus 10 for use principally in single-substrate epitaxial chemical vapor deposition reactors. The gas injector apparatus 10 consists generally of a remote manifold 12, a straight- walled plenum chamber 54, a shuttered and apertured plate 16 and an main injector body 20. Remote manifold 12 and plenum chamber 54 cooperate to provide a uniform velocity gas flow having a vertical directional vector which exits plenum chamber 54 via slot 56. In order to create a uniform velocity gas flow within plenum chamber 54 of remote manifold 12, the reactant gas is introduced into remote manifold 12 through a hollow tubular member 14 which is coaxially disposed within a hollow baffle member 40. Hollow baffle member 40 is, in turn, coaxially disposed within an upper chamber 50 of remote manifold 12. According to the preferred embodiment of the present invention and as illustrated in Figures 4, 8 and 9, remote manifold 12 consists of plenum chamber 54, upper chamber 50 and slot 56. Upper chamber 50 extends laterally through an upper portion of remote manifold 12 and terminates at openings 51 at each of two side surfaces of the remote manifold 12. Hollow tubular member 14 , having a gas inlet aperture 34 passing therethrough, is removably coupled to an opening 51 in one side surface of remote manifold 12 and passes into upper chamber 50 so that gas inlet aperture 34 is disposed within upper chamber 50. Hollow baffle member 40, having a plurality of apertures 36 passing therethrough, is removably coupled to an opposing opening 53 in the opposing side surface of remote manifold 12. Hollow baffle member 40 extends coaxially within upper chamber 50 and coaxially surrounds hollow tubular member 14. Attachment of both hollow tubular member 14 and hollow baffle member 40 to the side surfaces of remote manifold 12 may be accomplished by means of a base plate 32, an o-ring 37 and bolts 35 which engage each side surface of the remote manifold 12. Gas input through the inner hollow tubular member 14 is passed through aperture 34 conducting gas from the inner hollow tubular member 14 to the outer hollow baffle member 40 and is re-distributed from outer hollow baffle member 40 through the plurality of apertures 36 into upper chamber 50. The gas flow into plenum chamber 54 has, as a result of the distribution within the manifold 12, a substantially uniform velocity profile. Plate 16 has a plurality of apertures 38 passing therethrough. Plate 16 is removably coupled to remote manifold 12 such that apertures 38 communicate with slot 56. Each of apertures 38 has an associated shutter 22 which may be adjusted to restrict desired portions of the gas flow exiting slot 56 of remote manifold 12. Shutters 22 are adjusted to " desired positions to expose various sized openings in apertures 38 and shape the velocity of the uniform gas flow received from plenum chamber 54 via slot 56 as it exits the opposing surface of plate 16. The vertical directional vector of the shaped velocity gas flow is maintained as the gas flow passes through plate 16. Main injector body 20 is configured to receive the shaped velocity vertical gas flow exiting the opposing surface of plate 16 and redirect the gas flow to a horizontal directional vector for introduction into the hollow interior 17 of the reactor 11. Main injector body 20 has a plurality of apertures 28 disposed in an upper surface 24 thereof. Plate 16 is removably coupled to the upper surface 24 of the main injector body 20 such that each of the plurality of apertures 28 in the main injector body 20 correspond to an aperture 38 in plate 16. The shaped velocity gas flow exiting from apertures 38 in plate 6 is received by apertures 28 in the main injector body 20. Upon entering apertures 28 in the main injector body 20, the gas flow maintains a vertical directional vector. As illustrated in Figures 5 and 6, the interior chamber of main injector body 20 has a generally L-shaped cross- sectional configuration. It is to be noted that the inter- aperture web between apertures 28 in the main injector body extend from the upper surface 24 of main injector body 20 to the upper edge of gas injection slot 26. Within the interior chamber of main injector body 20, the direction of the gas flow is altered from a vertical directional vector to a horizontal directional vector and exits main injector body 20 through gas injection slot 26. As illustrated in Figure 4, it is preferable to couple the remote manifold 12, plate 16 and main injector body 2 0 by a plurality of bolts 30 which pass through an receiving apertures in remote manifold 12, through apertures in plate 16 and into main injector body 20. O-rings 41, to seal the coupled fittings, are interdisposed between plate 16 and remote manifold 12 as well as between plate 16 and main injector body 20 in groove 39 formed in upper surface 24 of main injector body 20. Another o-ring 39, for sealing the main injector body 20 and the CVD reactor (not shown) , is disposed in the front surface of main injector body 20 and surrounds gas injection slot 26. It will be appreciated, by those skilled in the art, that various materials may be employed, which are known to be compatible with CVD reactors and the reactant gases utilized in chemical vapor deposition processes. It has, therefore, been found advantageous to provide a gas injection apparatus having a remote manifold for creating a uniform velocity gas flow, shaping the uniform velocity gas flow to create a shaped-velocity gas flow profile and re-directing the vertical directional flow vector to a horizontal flow vector for introduction of the shaped-velocity gas flow into the hollow interior of the reactor. The nvention has been particularly described and illustrated with reference to certain embodiments thereof, but it is not intended that the invention be strictly limited to these embodiments. Those having ordinary skill in the art will recognize that variations and modifications differing from these embodiments, but falling within the spirit and scope of the invention, are possible. Other materials or configurations, for example, are contemplated by the present invention. All such variations and modifications as fall within the appended claims are therefore considered within the scope of the invention.

Claims: WHAT IS CLAIMED IS: 1. A gas injector apparatus for an epitaxial 5 deposition reactor, comprising: a remote manifold having an upper chamber, a plenum chamber and a outlet opening associated with said plenum chamber; a hollow tubular member having at least one aperture 0 passing therethrough, said hollow tubular member being connected to a source of gas and disposed coaxially within said upper chamber of said remote manifold; a hollow baffle member, having a plurality of apertures passing therethrough, coaxially surrounding said 15 hollow tubular member and coaxially disposed within said upper chamber of said remote manifold; a plate member having a plurality of openings passing therethrough, said plate member being coupled to said remote manifold such that said plurality of openings in 20. said plate member communicate with said outlet opening associated with said plenum chamber or said remote manifold; flow restriction means associated with each of said plurality of openings in said plate member, for regulating 25 a flow of gas through said each of said plurality of openings in said plate member; a main injector body having an upper surface and a front surface and an L-shaped chamber within said main injector body communicating with each of said upper surface 30 and said front surface, said main injector body being coupled to said plate member such that said plurality of openings in said plate member communicate with upper surface and said L-shaped chamber of said main injector body. 2. The gas injector apparatus according to Claim 1, wherein said plenum chamber of said remote manifold has parallel walls. 3. The gas injector apparatus according to Claim 1, wherein said plurality of openings in said plate member further comprises a plurality of elongated slot openings longitudinally disposed along a length of said plate member. 4. The gas injector apparatus according to Claim 3, wherein said flow restriction means further comprises a plurality of shutter members" operably coupled to each of said plurality of elongated slot openings to adjust the size of the opening of each of said elongated slot openings. 5. The gas injector apparatus according to Claim 4, wherein said upper surface of said main injector body further comprises a plurality of elongated slot openings communicating with said plurality of elongated slot openings in said plate member and to said L-shaped chamber of said main injector body. 6. The gas injector apparatus according to Claim 3, wherein said front surface of said main injector body further comprises a horizontally disposed gas injection opening communicating with said L-shaped chamber of said main injector body. 7. The gas injector apparatus according to Claim 6, wherein said main injector body further comprises an inter- opening web interdisposed between each of said plurality of elongated slot openings and extending from said upper surface to said horizontally disposed gas injection opening in said main injector body. 8. In an epitaxial deposition system having a reaction chamber for single substrate processing, said reaction chamber having a reaction chamber input, an improved gas injector apparatus for injecting at least one of a reactant gas and a carrier gas into the input of the reaction chamber, said improved gas injector apparatus comprising: a gas injector body having a front panel, a rear panel, a pair of opposing edge portions, a closed bottom and an open top defining a substantially hollow chamber therein; elongated plate means adapted to be operatively disposed over said open top, said elongated plate means further having aperture means operatively disposed in said elongated plate means and flow restriction means, associated therewith, for shaping the velocity profile of said gas passing therethrough and for outputting a predetermined shaped velocity profile of said gas passing through said hollow interior and being supplied into the input of said reaction chamber through said aperture outlet means of said front panel; means for supplying a generally uniform velocity flow of said gas toward said aperture means of said elongated plate means; and aperture outlet means operatively disposed in said front panel for supplying said gas into said input of said reaction chamber. 9. The improved gas injector apparatus of Claim 8, wherein said hollow interior chamber of said gas injector body comprises an L-shaped chamber communicating with said front panel and said open top. 10. The improved gas injector apparatus of Claim 9, wherein said gas injector body further comprises a plurality of elongate slot openings longitudinally disposed in said open top and communicating with said aperture means of said elongated plate means. 11. The improved gas injector apparatus of Claim 10, wherein said flow restriction means further comprises a plurality of shutter members operably coupled to each of said plurality of elongated slot openings to adjust the size of the opening of each of said elongated slot openings. 12. The improved gas injector apparatus of Claim 11, wherein said means for supplying a generally uniform velocity gas flow further comprises: a remote manifold having an upper chamber, a plenum chamber and a outlet opening associated with said plenum chamber; a hollow tubular member having at least one aperture passing therethrough, said hollow tubular member being connected to a source of gas and disposed coaxially within said upper chamber of said remote manifold; and a hollow baffle member, having a plurality of apertures passing therethrough, coaxially surrounding said hollow tubular member and coaxially disposed within said upper chamber of said remote manifold. 13. A method for producing and injecting a gas flow having a shaped velocity profile in an epitaxial deposition reactor having a substantially hollow interior, a susceptor disposed within the interior of the reaction chamber, a gas input to the reaction chamber, a gas source, an injector having a plenum chamber, a downwardly disposed gas distribution passage, a flow-direction apparatus operatively disposed at a lower end of the gas distribution passage and an elongated output slot in a front surface of the reaction chamber, comprising the steps of: distributing a reactant gas vertically downward within the hollow interior of the plenum chamber; providing a plurality of selectively dimensioned openings in a plate means for separating the plenum chamber from the hollow interior of the gas injector; passing the reactant gas vertically downward through said dimensioned openings of said plate means thereby shaping a velocity profile of said gas flow; passing the shaped velocity profile gas flow vertically downward into the flow direction apparatus; redirecting said shaped velocity profile gas flow perpendicular to its vertically downward vector in said flow direction apparatus; and discharging said redirected shaped velocity profile gas flow through the discharge slot in the front panel of the gas injector thereby inputting a shaped velocity profile gas flow into the reaction chamber of the reactor.

Inventors: BARNETT LEWIS C, FERRO ARMAND PASQUALE, HAWKINS MARK RICHARD, BARNETT, LEWIS, C., FERRO, ARMAND, PASQUALE, HAWKINS, MARK, RICHARD
Applicants: ASM EPITAXY INC, ASM EPITAXY, INC.
Application year: 1988
Main classification: C23C16
IPC codes: C23C16, C30B25