Patent Description:
In chemical vapor deposition (CVD) processes, including epitaxial growth processes, uniformity in the thickness of a deposited film on a substrate is dependent on, among other factors, uniformity in the flow distribution of gasses within the process chamber. As the requirements for uniformity in film thickness become more stringent, the desire for more uniform flow rate distribution of gasses in the process chamber increases.

In conventional CVD devices, a source gas is introduced into the process chamber through a gas manifold and is directed between a gap defined between an upper window of the process chamber and a substrate positioned on a substrate support. The upper windows of conventional CVD devices do not direct a uniform gas flow distribution across the substrate surface in the processing chamber.

For example, some conventional upper windows include a curved surface spanning the process chamber and facing the substrate that may be convex, dipping towards the center of the substrate. However such conventional upper windows may produce a turbulent gas flow about the substrate resulting in dips or depressions in the epitaxy deposited on the substrate.

Additionally, some conventional CVD systems attempt to minimize the depth of the dips in the epitaxy thickness profile by operating at a decreased growth rate (e.g., at a lower deposition temperature within the processing chamber and/or at a reduced gas flow rate). However, such system of operation can result in longer process times with only moderate changes in the depth of the dips in the deposited epitaxy.

Accordingly, a need exists for an upper window capable of directing a more uniform flow distribution across the surface of a substrate within the processing chamber.

<CIT> describes a single wafer processing epitaxial growth method by which a single crystal substrate is placed in a reaction chamber with an upper wall having a downward convexity and an epitaxial layer is deposited on the single crystal substrate by introducing raw material gas and carrier gas into the reaction chamber through a gas feed port, in which, after any one of the radius of curvature of the upper wall of the reaction chamber and a difference between an upper end of the gas feed port and a lower end of the upper wall of the reaction chamber in the height direction or both are adjusted in accordance with the flow rate of the carrier gas which is introduced into the reaction chamber through the gas feed port, an epitaxial layer is deposited on the single crystal substrate.

<CIT> describes a semiconductor processing chamber wherein the inner surface of the window is substantially flat and parallel to the wafer to be processed. The window is thin in a center portion and thicker in a surrounding peripheral portion. The thickness increases in the radially outward direction, defined between the flat inner surface and a concave outer surface. The chamber employs multiple outlet ports for distributing gas laterally in a short length.

This Background section is intended to introduce the reader to various aspects of art that may be related to various aspects of the present disclosure, which are described and/or claimed below.

One aspect of the present invention is directed to a system for depositing a layer on a substrate. The system includes a processing chamber defining a gas inlet for introducing gas into the processing chamber and a gas outlet to allow the gas to exit the processing chamber. A substrate support is positioned within the processing chamber and is configured to receive a substrate. A transparent upper window includes a convex first face spaced from the substrate support to define an air gap therebetween. The upper window is positioned within the processing chamber to direct the gas from the gas inlet, through the air gap, and to the gas outlet. The first face includes a radially outer surface and a radially inner surface circumscribed within the outer surface. The outer surface has a first radius of curvature and the inner surface has a second radius of curvature that is different from the first radius of curvature.

Another aspect of the present disclosure is directed to a window for a substrate processing system. The window includes a frame for attaching the window to a processing chamber of the substrate processing system and a transparent body connected to the frame. The body extends between a convex first face and an opposed second face. The first face includes a radially outer surface and a radially inner surface circumscribed within the outer surface. The outer surface extends radially from the frame to the inner surface and the inner surface extends radially inward from the outer surface to a radial center of the window. The outer surface has a first radius of curvature and the inner surface has a second radius of curvature that is different from the first radius of curvature.

Yet another aspect of the present invention is directed to a method of depositing a layer on a substrate. The method includes providing a substrate on a substrate support within a processing chamber. The processing chamber includes a gas inlet and a gas outlet. The method further includes providing an upper window in the processing chamber. The upper window is transparent to enable radiant heating light to pass through the upper window. The upper window has a convex first face spaced from the substrate to define an air gap therebetween. The first face includes a radially outer surface and a radially inner surface circumscribed within the outer surface. The outer surface has a first radius of curvature and the inner surface has a second radius of curvature that is different from the first radius of curvature. The method further includes directing a gas flow through the gas inlet, into the air gap between the first face and the substrate, and to and to the gas outlet.

Various refinements exist of the features noted in relation to the above-mentioned aspects. Further features may also be incorporated in the above-mentioned aspects as well. These refinements and additional features may exist individually or in any combination. For instance, various features discussed below in relation to any of the illustrated embodiments may be incorporated into any of the above-described aspects, alone or in any combination.

Like reference symbols used in the various drawings indicate like elements.

A chemical vapor deposition (CVD) system, also referred to herein as a "substrate processing system," is indicated generally at <NUM> in <FIG>. The illustrated system is a single substrate system, however, the system and methods disclosed herein for providing a more uniform gas flow distribution are suitable for use in other system designs including, for example, multiple substrate systems. One example of a CVD system suitable for use in accordance with the present invention is the Applied Materials EPI Centura <NUM>.

The invention is detailed in the appended claims.

As used herein, the term "curvature" refers to an amount by which a curve of a surface and/or a face deviates from a plane and the phrase "radius of curvature" refers to the radius of a circle and/or sphere whose perimeter has a curvature matching the curvature of the surface and/or face. For example, a surface and/or face having a relatively large curvature includes a relatively high deviation from a plane at any point along the curve and a relatively short radius of curvature. Likewise a surface or face having a relatively small curvature will have a relatively low deviation from a plane at any point along the curve and a relatively large radius of curvature.

The CVD system <NUM> includes a reaction or processing chamber <NUM> for depositing and/or growing thin films on a substrate <NUM> (e.g., a semiconductor wafer), a gas injection port <NUM> disposed at one end of the processing chamber <NUM>, and a gas discharge port <NUM> disposed at an opposite end of the processing chamber <NUM>. A gas manifold <NUM> disposed between the gas injecting port <NUM> and the processing chamber <NUM> is used to direct incoming gas <NUM> into the processing chamber <NUM> enclosed by an upper window <NUM> and a lower window <NUM> through the gas injection port <NUM>. The gas manifold <NUM> includes an injector baffle or gas distribution plate disposed between the gas injecting port <NUM> and the processing chamber <NUM>, and an inject insert liner assembly <NUM> disposed adjacent to the baffle plate and upstream from the processing chamber <NUM>. In operation, an incoming process gas <NUM> flows through the gas manifold <NUM> and into the processing chamber <NUM> through gas inlet <NUM>. The gas <NUM> then flows over the substrate surface <NUM> and reacts with the substrate surface <NUM>, or precursors disposed thereon, to deposit a film on the substrate surface <NUM>. The gas <NUM> then flows out of the processing chamber <NUM> and through the gas discharge port <NUM>.

The substrate <NUM> upon which the film is deposited is supported by a susceptor <NUM> within the processing chamber <NUM>. The susceptor <NUM> is connected to a shaft <NUM> that is connected to a motor (not shown) of a rotation mechanism (not shown) for rotation of the shaft <NUM>, susceptor <NUM> and substrate <NUM> about a vertical axis X of the CVD system <NUM>. The outside edge <NUM> of the susceptor <NUM> and inside edge of a preheat ring <NUM> (for heating the incoming gas <NUM> prior to contact with the substrate <NUM>) are separated by a gap to allow rotation of the susceptor <NUM>. The substrate <NUM> is rotated to prevent an excess of material from being deposited on the wafer leading edge and provide a more uniform epitaxial layer.

Incoming gas <NUM> may be heated prior to contacting the substrate <NUM>. Both the preheat ring <NUM> and the susceptor <NUM> are generally opaque to absorb radiant heating light (e.g., infrared light) produced by high intensity radiant heating lamps <NUM> that may be located above and below the processing chamber <NUM>. Equipment other than high intensity lamps <NUM> may be used to provide heat to the processing chamber <NUM> such as, for example, resistance heaters and inductive heaters. Maintaining the preheat ring <NUM> and the susceptor <NUM> at a temperature above ambient allows the preheat ring <NUM> and the susceptor <NUM> to transfer heat to the incoming gas <NUM> as the gas <NUM> passes over the preheat ring <NUM> and the susceptor <NUM>. The diameter of the substrate <NUM> may be less than the diameter of the susceptor <NUM> to allow the susceptor <NUM> to heat incoming gas <NUM> before it contacts the substrate <NUM>. The preheat ring <NUM> and susceptor <NUM> may be constructed of opaque graphite coated with silicon carbide.

The upper and lower chamber walls <NUM>, <NUM> define the outer perimeter of the processing chamber <NUM>, and contact the gas injection port <NUM> and the gas discharge port <NUM>.

The CVD system <NUM> may include upper and lower liners <NUM>, <NUM> disposed within the processing chamber to prevent reactions between the gas <NUM> and the chamber walls <NUM>, <NUM> (which are typically fabricated from metallic materials, such as stainless steel). The liners <NUM>, <NUM> may be fabricated from suitably non-reactive materials, such as quartz.

The upper and lower windows <NUM>, <NUM> each comprise a generally annular body <NUM> made of a transparent material, such as quartz, to allow radiant heating light to pass into the processing chamber <NUM> and onto the preheat ring <NUM>, the susceptor <NUM>, and the substrate <NUM>. The windows <NUM>, <NUM> may be planar, or, as shown in <FIG>, the windows <NUM>, <NUM> may have a generally dome-shaped configuration and/or inwardly concave configuration. In particular, referring to the embodiment shown in <FIG>, the lower window <NUM> has a generally dome-shaped configuration and the upper window has an inwardly concave configuration. The upper and lower windows <NUM>, <NUM> are each coupled or connected (terms used interchangeable herein) to the upper and lower chamber walls <NUM>, <NUM> of the processing chamber <NUM>, respectively. In particular, the upper window <NUM> includes a rim <NUM>, or more broadly, a frame, attached to the upper chamber wall <NUM>. Alternatively, the upper window <NUM> does not include the rim <NUM> and may be coupled to the upper chamber wall <NUM> in any manner that enables the upper window <NUM> to function as described herein.

The upper window <NUM> further includes the transparent body <NUM>, which is attached, or optionally connected, to the rim <NUM> and extends between an upper concave face <NUM> and a lower convex face <NUM> of the upper window <NUM>. The upper face <NUM> and the lower face <NUM> are each circumscribed within the rim <NUM>. The upper face <NUM> is oriented to face away from the substrate <NUM>. The lower face <NUM> is oriented to face the substrate <NUM>. As shown in <FIG>, the upper face <NUM> is curved substantially in correspondence with the lower face <NUM>. Alternatively, the upper concave face <NUM> is shaped in any manner that enables the upper window <NUM> to function as described herein. For example, in some alternative embodiments, the upper face <NUM> may have a generally planar and/or dome shaped configuration.

The lower face <NUM> of the upper window <NUM> and the susceptor <NUM> may define a longitudinal gap, indicated generally at <NUM>, therebetween. The gap <NUM> is sized to direct incoming gas <NUM> from the gas inlet <NUM>, along the substrate surface <NUM> to the gas outlet <NUM>, when the substrate is positioned within the susceptor. In the exemplary embodiment, the gap <NUM> is approximately <NUM> millimeters at its narrowest point. In other embodiments, the gap is any size that enables the CVD system to operate as described herein. As described in greater detail below, the lower face <NUM> is shaped to direct the process gas <NUM> over the substrate during operation of the CVD system to provide a substantially uniform vapor deposition on the substrate <NUM>.

<FIG> shows an enlarged view of portions of the CVD system <NUM> and <FIG> shows a bottom view of the upper window <NUM>. <FIG> is an enlarged cross-section of a portion of the upper window <NUM> shown in <FIG>. Referring now to <FIG>, wherein portions of the CVD system <NUM> have been removed for illustration, the shape of the upper window <NUM> is shown in greater detail. It will be understood that the dimensions of the upper window <NUM> are not drawn to scale in <FIG> and, more particularly, that the curvatures of the upper window <NUM> are exaggerated for purposes of illustration.

As shown in <FIG>, the lower face <NUM> defines a lowermost point, indicated generally at <NUM>. In particular, as described herein, the lowermost point <NUM> of the lower face <NUM> is the point wherein the gap <NUM> defined between the lower face <NUM> and the substrate surface <NUM> is at its most narrow. For example, as shown in <FIG>, the lowermost point <NUM> is spaced a gap distance, indicated at G<NUM>, from the substrate <NUM>. As shown in <FIG>, the lowermost point <NUM> of the lower face <NUM> is also be located at the radial center of the lower face <NUM>, or, more generally, at the radial center of the upper window <NUM>. Alternatively, the upper window <NUM> may be shaped such that the lowermost point of the upper window <NUM> is spaced from the radial center of the upper window <NUM>. Moreover, as shown in <FIG>, the lowermost point <NUM> may be vertically aligned with a radial center of the substrate <NUM>.

The lower face <NUM> of the upper window <NUM> includes a radially outer surface <NUM> and a radially inner surface <NUM> circumscribed within the outer surface <NUM>. More specifically, as shown in the embodiment of <FIG>, the outer surface <NUM> extends a first radial distance, indicated at R<NUM>, radially inward from the rim <NUM> to the inner surface <NUM>. The outer surface <NUM> is curved such that the outer surface also extends a height, indicated generally at H<NUM>, from the rim <NUM> to the inner surface <NUM>. More specifically, in the example embodiment, the outer surface <NUM> of the lower face <NUM> has a constant curvature between the rim <NUM> and the inner surface <NUM>. Alternatively, the outer surface <NUM> may include multiple surfaces having varied curvatures from one another.

The inner surface <NUM> of the lower face <NUM> extends a second radial distance in a plane tangential to the lowermost point <NUM> (also a "radial center" of the upper window in the example embodiment), indicated at R<NUM>, between the outer surface <NUM> and the lowermost point <NUM> of the upper window <NUM>. The radius R<NUM> of the inner surface <NUM> may be between <NUM> millimeters and <NUM> millimeters, between <NUM> millimeters and <NUM> millimeters, between <NUM> millimeters and <NUM> millimeters, or between <NUM> millimeters and <NUM> millimeters. In the embodiment of <FIG>, the radius R<NUM> of the inner surface <NUM> is approximately <NUM> millimeters. The inner surface <NUM> may also be curved such that the inner surface <NUM> also extends a height, indicated at H<NUM> between the outer surface <NUM> and the lowermost point <NUM> (i.e., the radial center) of the upper window <NUM>. As shown in the embodiment of <FIG>, the inner surface <NUM> has a constant curvature from the outer surface <NUM> to the lowermost point <NUM> and from the lowermost point <NUM> to a diametrically opposed portion of the outer surface <NUM>. Alternatively, the inner surface <NUM> may include multiple surfaces having varied curvatures from one another.

The lower face <NUM> extends an overall height, indicated at H<NUM> from the rim <NUM> to the lowermost point <NUM>. More specifically, in the embodiment shown in <FIG>, the overall height H<NUM> is equal to the sum total of the height H<NUM> of the outer surface <NUM> and the height H<NUM> of the inner surface <NUM>. The overall height H<NUM> may be between <NUM> millimeters and <NUM> millimeters, <NUM> millimeters and <NUM> millimeters, or <NUM> millimeters and <NUM> millimeters. In the embodiment of <FIG>, the overall height H<NUM> of the lower face <NUM> is approximately <NUM> millimeters.

As shown in <FIG> and <FIG>, in the example embodiment, the outer surface <NUM> has a greater curvature than the inner surface <NUM> such that the inner surface <NUM> has a greater radius of curvature than the outer surface <NUM>. As a result, as shown in <FIG> and <FIG>, the lower face <NUM> defines a curve boundary <NUM> extending circumferentially around the lower face <NUM> at the intersection of the inner surface <NUM> and the outer surface <NUM>. The outer surface <NUM> may have a radius of curvature that is at least double the radius of curvature of the inner surface <NUM>. The radius of curvature of the outer surface <NUM> is suitably between <NUM> millimeters and <NUM>,<NUM> millimeters, between <NUM> and <NUM>,<NUM> millimeters, or between <NUM> millimeters and <NUM> millimeters. In the embodiment shown in <FIG>, the radius of curvature of the outer surface <NUM> is <NUM>,<NUM> millimeters. The radius of curvature of the inner surface <NUM> is suitably between <NUM>,<NUM> millimeters and <NUM>,<NUM> millimeters, between <NUM>,<NUM> millimeters and <NUM>,<NUM> millimeters, or between <NUM>,<NUM> millimeters and <NUM>,<NUM> millimeters. In the embodiment shown in <FIG>, the radius of curvature of the inner surface <NUM> is <NUM>,<NUM> millimeters. A ratio of the radius of curvature of the inner surface <NUM> to the radius of curvature of the outer surface <NUM> is suitably between <NUM>:<NUM> and <NUM>:<NUM>, between <NUM>:<NUM> and <NUM>:<NUM>, between <NUM>:<NUM> and <NUM>:<NUM>, or between <NUM>:<NUM> and <NUM>:<NUM>. In the embodiment shown in <FIG>, the ratio of the radius of curvature of the inner surface <NUM> to the radius of curvature of the outer surface <NUM> is about <NUM>:<NUM>.

Upper window <NUM> is suitably sized such that at least a portion of the outer surface <NUM> and at least a portion of the inner surface <NUM> vertically cover (i.e., are vertically aligned with) the substrate surface <NUM>. In particular, a ratio of the radius of the substrate <NUM> to the radius R<NUM> of the inner surface <NUM> may be between <NUM>:<NUM> and. <NUM>:<NUM>, between <NUM>:<NUM> and <NUM>:<NUM>, or between <NUM>:<NUM> and <NUM>:<NUM>. In the embodiment shown in <FIG>, a ratio of the radius of the substrate <NUM> to the radius R<NUM> of the inner surface <NUM> is approximately <NUM>:<NUM>. More specifically, the radius R<NUM> of the inner surface <NUM> is approximately <NUM> millimeters and the radius of the substrate <NUM> is approximately <NUM> millimeters. In one alternative embodiment, the radius R<NUM> of the inner surface <NUM> is approximately <NUM> millimeters the radius of the substrate <NUM> is approximately <NUM> millimeters. In alternative embodiments, the upper window <NUM> may be sized such that the outer surface <NUM> is radially spaced from the substrate <NUM> and only the inner surface <NUM> vertically covers the substrate surface <NUM>.

In operation, the gas <NUM> is introduced into the CVD system <NUM> from the gas injecting port at a selected flow rate. The gas may then flow into the air gap <NUM> defined between the lower face <NUM> and the susceptor <NUM> and/or the substrate <NUM>. More specifically, at least a portion of the gas may flow along the outer surface <NUM> of the lower face <NUM> and to the inner surface <NUM>. The gas <NUM> may then flow into a narrower portion of the gap <NUM> between the inner surface and the substrate <NUM>. At least in part due to the configuration of the outer surface <NUM> and the inner surface <NUM>, the gap <NUM> may be narrow at a center of the substrate <NUM> while the curvature of the inner surface <NUM> may be relatively small (i.e., the radius of curvature of the inner surface <NUM> may be relatively large) compared to at least some conventional upper windows. The narrow gap <NUM> at the center of the substrate in combination with the relatively small curvature of the upper window <NUM> proximate the center of the substrate <NUM> facilitates providing a laminar gas flow around the center of the substrate <NUM> and inhibits the formation of "dips" or depressions in the epitaxial deposition surrounding the center of the substrate <NUM>.

The windows for a CVD system of the present invention are further illustrated by the following Examples. These Examples should not be viewed in a limiting sense. Only systems with dual curvature windows are the subject-matter of the invention, and the related deposition method, such as mentioned in the appended claims. The examples hereunder do thus contain also comparative configurations, thus all the ones referring to not double curved.

In a first example, thickness profiles of epitaxy deposition on substrates were measured for different upper windows having different lower faces. In particular, a large curvature window, a small curvature window, and two windows having a dual curvature lower face were tested in a CVD system. More specifically, each of the windows were tested in an Applied Materials EPI Centura <NUM> system. The CVD system was controlled to deposit an epitaxy film on a cylindrical substrate having a diameter of <NUM> millimeters. In particular, the CVD system was controlled to deposit the film on the substrates at a growth rate of approximately <NUM>/min (microns per minute) for each of the test windows. Thickness change values were measured by determining the difference between the greatest thickness and the lowest thickness over radial ranges of the substrate. For example, radial ranges of the substrate included -<NUM> millimeters to -<NUM> millimeters, -<NUM> millimeters to <NUM> millimeters, <NUM> millimeters to <NUM> millimeters, and <NUM> millimeters to <NUM> millimeters, where the <NUM> millimeter position indicated the radial center of the substrate. A typical dip value for each of the tests was calculated by averaging the thickness change values for each of the substrate diameter ranges.

As shown in Table <NUM>, provided below, the large curvature window had a lower face having a single radius of curvature of <NUM>,<NUM> millimeters, the small curvature window had a lower face having a single radius of curvature of <NUM>,<NUM> millimeters, the first dual curvature window had a lower face with an outer surface having a radius of curvature of <NUM>,<NUM> millimeters and an inner face having a radius of curvature of <NUM>,<NUM> millimeters. The second dual curvature window had a lower face with an outer surface having a radius of curvature of <NUM> millimeters and an inner face having a radius of curvature of <NUM>,<NUM> millimeters. The inner surface of the first dual curvature window had a radius of <NUM> millimeters and the inner surface of the second dual curvature window had a radius of <NUM> millimeters.

The large curvature window was positioned in the CVD system such that a gap between the large curvature window and the substrate (e.g., similar to gap <NUM> described above with respect to <FIG>) was approximately <NUM> millimeters at its narrowest point. In other words, the distance between the lowest point of the upper window (e.g., similar to point <NUM> described above with respect <FIG> and <FIG>) and the substrate was approximately <NUM> millimeters. The first dual curvature window and the second dual curvature window were positioned in substantially the same manner as the large curvature. Due to the larger curvature outer surfaces of the dual curvature windows, the gap between the substrate and the each of the dual curvature windows was approximately <NUM> millimeters at their narrowest points. The small curvature window was also positioned such that the gap between the substrate and the windows was approximately <NUM> millimeters at its narrowest point.

As shown in Table <NUM>, provided above, the first dual curvature window and the second dual curvature window each resulted in a lower relative thickness variation (i.e., improved thickness uniformity) than both the large curvature window and the small curvature window. Moreover, the first dual curvature window and the second dual curvature window each resulted in a smaller typical dip than the large curvature window. "Relative layer thickness variation" of a deposited layer is determined by measuring the difference between the maximum layer thickness and the minimum layer thickness, and dividing this difference by the average layer thickness. The resultant value is multiplied by <NUM> in order to arrive at a percentage. This percentage is the "relative layer thickness variation" as disclosed herein.

<FIG> are graphs showing the measured thickness profiles of epitaxy deposited on the substrate surfaces for each of the test windows. The Y-axis in the graph represents the thickness in nanometers of epitaxy deposited on the substrate surface, with the zero adjusted to the lowest measured thickness on the substrate. The X-axis in the graph indicates the distance from the radial center of the substrate. More specifically, <FIG> shows the measured thickness profile <NUM> from the above tests, described with respect to Table <NUM>, performed on the large curvature window. <FIG> shows the measured thickness profile <NUM> from the above tests performed on the large curvature window. <FIG> shows the measured thickness profile <NUM> from the above tests performed on the first dual curvature window, having an inner surface radius of <NUM> millimeters. <FIG> shows the measured thickness profile <NUM> from the above tests performed on the second dual curvature window, having an inner surface radius of <NUM> millimeters.

As shown in <FIG>, the large curvature window resulted in significant dips <NUM> in the epitaxy thickness profile around one third of the radial distance from the center of the substrate (i.e., at +/- <NUM> millimeters from the center of the substrate). Moreover, as shown in <FIG>, the dips <NUM> around the +/- <NUM> millimeter portion of the substrate were less pronounced with the small curvature window as compared with the large curvature window. However, the small curvature window resulted in high edge upticks <NUM> between the -<NUM> millimeters to -<NUM> millimeter range and between the <NUM> millimeter to <NUM> millimeter range on the substrate.

Referring to <FIG> and <FIG>, the epitaxy deposited on the substrates using both the first dual curvature window and the second dual curvature window had reduced dips <NUM>, <NUM> around the +/-<NUM> millimeter radius range compared with the large curvature window. Moreover, the epitaxy deposited on the substrate surfaces had reduced edge upticks <NUM>, <NUM> between the -<NUM> millimeters to -<NUM> millimeter range and between the <NUM> millimeter to <NUM> millimeter range, as compared with the small curvature window. As a result, as shown in Table <NUM>, provided above, the dual curvature windows each resulted in an epitaxial deposition profile that had a lower relative thickness variation compared to the large and small curvature upper windows.

In a second example, the test windows were used to measure the effects of operating the CVD system at different flow rates. For each of the tests, the temperature of the processing chamber was maintained at <NUM> degrees Celsius.

In a first test, the large curvature window, the small curvature window, and the first dual curvature upper window were each tested in the CVD system and a trichlorosilane-hydrogen mixture was introduced into the CVD system at a flow rate of <NUM> standard-liters per minute. Average thickness of the epitaxy deposition and deposition time were measured to determine a growth rate in microns per minute. The results of the tests are provided in Table <NUM> below.

As shown in Table <NUM>, provided above, the first dual curvature window resulted in an increased growth rate relative to the large curvature window.

In a second test, the first dual curvature window and the second dual curvature window were each tested in the CVD system and a trichlorosilane-hydrogen mixture was introduced into the CVD system at a flow rate of <NUM> standard-liters per minute. Average thickness of the epitaxy deposition and deposition time were measured to determine a growth rate in microns per minute. The results of the tests are provided in Table <NUM> below.

As shown in Table <NUM>, provided above, the second dual curvature window resulted in an increased growth rate relative to the first dual curvature window. Moreover, the growth rate using the first dual curvature window at a flow rate of <NUM> standard-liters per minute was about the same as the growth rate as resulted from the large curvature window operating at an increased flow rate of <NUM> standard-liters per minute measured in the first test.

In CVD systems including the upper windows described herein, the uniformity of the gas flow distribution across the substrate surface can be maintained across different gas flow rates compared with conventional CVD systems. For example, process gas, such as a trichlorosilane-hydrogen mixture, may be introduced into the CVD system at a flow rate of at least about <NUM> standard-liters per minute, at least about <NUM> standard-liters per minute, or even at least about <NUM> standard-liters per minute, while maintaining a relative layer thickness variation of less than about <NUM>% across the substrate surface, less than about <NUM>% across the substrate surface, or even less than about <NUM>% across the substrate surface. Carrier gas, such as hydrogen, may also be introduced at a higher flow rate, such as at least about <NUM> standard-liters per minute, at least about <NUM> standard-liters per minute, or even at least about <NUM> standard-liters per minute, while maintaining a relative layer thickness variation of less than about <NUM>% across the substrate surface, less than about <NUM>% across the substrate surface, or even less than about <NUM>% across the substrate surface. Because the uniformity of the gas flow distribution across the substrate surface can be maintained at higher gas flow rates, the rate at which a given film or layer is deposited on a substrate may also be increased while maintaining uniformity in the layer thickness. For example, an epitaxial layer may be deposited on a silicon wafer having a diameter of at least about <NUM> millimeters, at least about <NUM> millimeters, at least about <NUM> millimeters, while maintaining a relative layer thickness variation of less than about <NUM>% across the diameter of the wafer, less than about <NUM>% across the diameter of the wafer, or even less than about <NUM>% across the diameter of the wafer.

As used herein, the term "standard-liter" refers to one liter of the referenced gas at <NUM> and <NUM> kPa (<NUM> millibar).

The examples described are suitable for processing semiconductor wafers, such as silicon wafers, though may be used in other applications. Some of the examples are particularly suited for use in atmospheric-pressure silicon on silicon chemical vapor deposition epitaxy using gas mixtures including hydrogen, trichlorosilane, and diborane. Silicon precursors other than trichlorosilane may also be used, including dichlorosilane, silane, trisilane, tetrachlorosilane, methylsilane, pentasilane, neopentasilane, and other higher order silane precursors. Precursors other than silicon precursors may also be used, including germane, digermane, and other germanium precursors. Dopant gas species other than diborane may be used, including phosphine and arsine. The examples described may also be used in processes other than atmospheric-pressure silicon on silicon epitaxy, including reduced-pressure epitaxy (e.g., at pressures between about <NUM> Torr and about <NUM> Torr), silicon-germanium epitaxy, carbon-doped silicon epitaxy, and non-epitaxial chemical vapor deposition. The examples may also be used to process wafers other than silicon wafers, including wafers having germanium, gallium arsenide, indium phosphide, and silicon carbide.

As described above, processing chambers including the upper windows of the present invention provide an improvement over known processing chambers. The upper windows of the present invention include two surfaces having different curvatures to direct the process flow during operation and facilitate providing a laminar flow of process gas across the substrate. As a result, uniformity in gas flow distribution across the substrate surface can be improved. More specifically, CVD systems including the upper windows of the present invention provide the following advantages over the some conventional CVD systems: <NUM>) reduced epitaxial dips on the substrate; <NUM>) reduced epitaxial upticks on the substrate near the outer perimeter of the substrate; <NUM>) reduced processing time for epitaxial deposition on substrates; and <NUM>) improved lifespan of semiconductor wafers.

Claim 1:
A system (<NUM>) for depositing a layer on a substrate (<NUM>), the system comprising:
a processing chamber (<NUM>) defining a gas inlet (<NUM>) for introducing gas (<NUM>) into the processing chamber and a gas outlet (<NUM>) to allow the gas to exit the processing chamber;
a substrate support positioned within the processing chamber and configured to receive a substrate; and
an upper window (<NUM>) comprising:
a frame (<NUM>) for attaching the window to the processing chamber; and
a transparent body (<NUM>) connected to the frame, the body extending between a convex first face and an opposed second face, the first face including a radially outer surface (<NUM>) and a radially inner surface (<NUM>) circumscribed within the outer surface, the outer surface extending radially from the frame to the inner surface and the inner surface extending radially inward from the outer surface to a radial center of the window, characterized in that the outer surface having a first radius of curvature and the inner surface having a second radius of curvature different from the first radius of curvature,
the convex first face being spaced from the substrate support to define an air gap (<NUM>) therebetween, and the upper window being positioned within the processing chamber to direct the gas from the gas inlet (<NUM>), through the air gap, and to the gas outlet (<NUM>).