Windows for chemical vapor deposition systems and related methods - Patents.com

Abstract

A system for depositing a layer on a substrate includes a process chamber defining a gas inlet for introducing gas into the process chamber and a gas outlet for allowing the gas to exit the process chamber. A substrate support is disposed within the process chamber and configured to receive a substrate. A transparent top window includes a convex first surface spaced apart from the substrate support and defining an air gap therebetween. The top window is disposed within the process chamber and directs gas from the gas inlet through the air gap to the gas outlet. The first surface includes a radially outer peripheral surface and a radially inner peripheral surface tangent to the outer peripheral surface. The outer peripheral surface has a first radius of curvature, and the inner peripheral surface has a second radius of curvature different from the first radius of curvature.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims priority to U.S. Provisional Patent Application No. 62 / 706,452, filed August 18, 2020, the entire disclosure of which is incorporated herein by reference. [Technical field]

[0002] The field relates generally to the use of chemical vapor deposition systems in the processing of semiconductor wafers, and more specifically to windows and methods for controlling gas flow uniformity within a chemical vapor deposition process chamber. [Background technology]

[0003] In chemical vapor deposition (CVD) processes, including epitaxial growth, the uniformity of the thickness of the film deposited on the substrate depends on the uniformity of the gas flow distribution in the process chamber. As the demand for uniformity of film thickness becomes stricter, it is becoming desirable for the gas flow distribution in the process chamber to be more uniform.

[0004] In a conventional CVD apparatus, source gas is introduced into a process chamber through a gas manifold and directed into a gap defined between an upper window of the process chamber and a substrate disposed on a substrate support. The upper window of the conventional CVD apparatus cannot direct a uniform gas flow distribution to the substrate surface in the process chamber.

[0005] For example, some conventional top windows span the process chamber and include a curved surface facing the substrate, which may be convex toward the center of the substrate, however, such conventional top windows can cause turbulent gas flow at the substrate, resulting in dips and dips in the epitaxy deposited on the substrate.

[0006] Additionally, some conventional CVD systems attempt to minimize the dip depth in the epitaxy thickness profile by operating at reduced growth rates (e.g., reduced deposition temperatures and / or reduced gas flow rates in the process chamber). However, such operating systems increase process times to even moderately change the dip depth of the deposited epitaxy.

[0007] Therefore, there is a need for a top window that can direct a more uniform flow distribution to the substrate surface within a process chamber.

[0008] 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 that are described and / or claimed below. This discussion is believed to be helpful in providing the reader with background information to facilitate a better understanding of the various aspects of the present disclosure. As such, it should be understood that these disclosures are to be read in this light, and not as admissions of prior art. Summary of the Invention

[0009] One aspect of the disclosure relates to a system for depositing a layer on a substrate. The system includes a process chamber defining a gas inlet for introducing gas into the process chamber and a gas outlet allowing gas to exit the process chamber. A substrate support is disposed within the process chamber and configured to receive a substrate. A transparent top window includes a convex first surface spaced apart from the substrate support and defining an air gap therebetween. The top window is disposed within the process chamber and directs gas from the gas inlet through the air gap to the gas outlet. The first surface includes a radially outer peripheral surface and a radially inner peripheral surface circumscribed within the outer peripheral surface. The outer peripheral surface has a first radius of curvature and the inner peripheral surface has a second radius of curvature different from the first radius of curvature.

[0010] Another aspect of the disclosure relates to a window for a substrate processing system. The window includes a frame for mounting the window to a process chamber of the substrate processing system and a transparent body connected to the frame. The body extends between a convex first surface and an opposing second surface. The first surface includes a radially outer peripheral surface and a radially inner peripheral surface circumscribing the outer peripheral surface. The outer peripheral surface extends radially from the frame to the inner peripheral surface, and the inner peripheral surface extends radially inward from the outer peripheral surface to a radial center of the window. The outer peripheral surface has a first radius of curvature and the inner peripheral surface has a second radius of curvature different from the first radius of curvature.

[0011] Yet another aspect of the present disclosure relates to a method of depositing a layer on a substrate. The method includes providing a substrate on a substrate support in a process chamber. The process chamber includes a gas inlet and a gas outlet. The method further includes providing a top window in the process chamber. The top window is transparent to allow radiant heat to pass through. The top window includes a convex first surface spaced from the substrate and defining an air gap therebetween. The first surface includes a radially outer peripheral surface and a radially inner peripheral surface circumscribed within the outer peripheral surface. The outer peripheral surface has a first radius of curvature and the inner peripheral surface has a second radius of curvature 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 surface and the substrate and to the gas outlet.

[0012] Various refinements of the features noted in relation to the above aspects exist. The above aspects may also incorporate additional features as well. These refinements and additional features may exist individually or in any combination. For example, the various features described below in relation to any of the illustrated embodiments may be incorporated into any of the above aspects alone or in any combination. [Brief description of the drawings]

[0013] [Figure 1]FIG. 1 is a cross-sectional view of a chemical vapor deposition system including a top window according to one embodiment of the present disclosure. [Diagram 2] 2 is an enlarged cross-sectional view of the chemical vapor deposition system of FIG. 1 with portions removed for illustrative purposes. [Diagram 3] FIG. 3 is a bottom view of the upper window shown in FIG. 2. [Figure 4] FIG. 3 is an enlarged cross-sectional view of a portion of the upper window shown in FIG. 2. [Diagram 5] 1 is a graph showing the thickness profile of epitaxy deposited on a substrate surface in a CVD system using a single large curvature top window. [Figure 6] 1 is a graph showing the thickness profile of epitaxy deposited on a substrate surface in a CVD system using a single small curvature top window. [Figure 7] 1 is a graph showing the thickness profile of epitaxy deposited on a substrate surface in a CVD system using a first dual curved top window. [Figure 8] 13 is a graph showing the thickness profile of epitaxy deposited on a substrate surface in a CVD system using a second double curvature top window.

[0014] Like reference numbers used in the various drawings indicate like elements. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0015] A chemical vapor deposition (CVD) system, also referred to herein as a "substrate processing system," is generally indicated at 100 in Figure 1. While the system shown is a single substrate system, the systems and methods disclosed herein are suitable for use with other system designs including, for example, multiple substrate systems to provide more uniform gas flow distribution. One example of a CVD system suitable for use in accordance with the present disclosure is the Applied Materials EPI Centura 300.

[0016] As used herein, "curvature" refers to the amount by which a curve of a surface and / or face deviates from a plane, and "radius of curvature" refers to the radius of a circle or sphere whose periphery has a curvature that matches the curvature of the surface and / or face. For example, a surface and / or face with a relatively large curvature will have a large deviation from a plane at any point of the curve and a relatively small radius of curvature. Similarly, a surface or face with a relatively small curvature will have a relatively small deviation from a plane at any point of the curve and a relatively large radius of curvature.

[0017] The CVD system 100 includes a reaction chamber or process chamber 102 for depositing and / or growing a thin film on a substrate 104 (e.g., a semiconductor wafer), a gas inlet port 106 disposed at one end of the process chamber 102, and a gas exhaust port 108 disposed at an opposite end of the process chamber 102. A gas manifold 140 disposed between the gas inlet port 106 and the process chamber 102 is used to direct incoming gas 110 through the gas inlet port 106 into the process chamber 102 surrounded by a top window 112 and a bottom window 114. The gas manifold 140 includes an injection baffle or gas distribution plate disposed between the gas inlet port 106 and the process chamber 102, and an injection insert liner assembly 170 disposed adjacent to the baffle plate and upstream of the process chamber 102. In operation, incoming process gas 110 flows through the gas manifold 140 and into the process chamber 102 through a gas inlet 103. The gas 110 then flows over the substrate surface 116, reacting with the substrate surface 116 or precursors disposed thereon, and depositing a film on the substrate surface 116. The gas 110 then flows out of the process chamber 102 and out the gas exhaust port 108.

[0018] The substrate 104 to be deposited is supported by a susceptor 120 within the process chamber 102. The susceptor 120 is connected to a shaft 122 that is connected to a motor of a rotation mechanism (not shown) for rotating the susceptor 120, the susceptor 120, and the substrate 104 about a vertical axis X of the CVD system 100. An outer edge 124 of the susceptor 120 and an inner edge of a preheat ring 126 (for heating the inlet gas 110 before contacting the substrate 104) are separated by a gap to allow rotation of the susceptor 120. Rotating the substrate 104 prevents excess material deposition on the leading edge of the wafer and provides a more uniform epitaxial layer.

[0019] The inlet gas 110 may be heated before contacting the substrate 104. Both the preheat ring 126 and the susceptor 120 are typically opaque to absorb radiant heating light (e.g., infrared light) generated by high intensity radiant heat lamps 128 that may be positioned above and below the process chamber 102. Heat may be provided to the process chamber 102 using devices other than high intensity lamps 128, such as resistive or inductive heaters. By maintaining the preheat ring 126 and the susceptor 120 at or above ambient temperature, the preheat ring 126 and the susceptor 120 transfer heat to the inlet gas 110 as the gas 110 passes over them. The diameter of the substrate 104 may be smaller than the diameter of the susceptor 120 so that the inlet gas 110 can be heated before the susceptor 120 contacts the substrate 104. The preheat ring 126 and susceptor 120 may be constructed of opaque graphite coated with silicon carbide.

[0020] Upper and lower chamber walls 130 , 132 define the perimeter of the process chamber 102 and border the gas inlet port 106 and the gas exhaust port 108 .

[0021] The CVD system 100 may include upper and lower liners 134, 136 disposed within the process chamber to prevent reactions between the gas 110 and the chamber walls 130, 132 (which are typically fabricated from a metallic material such as stainless steel). The liners 134, 136 may be made from a suitable non-reactive material such as quartz.

[0022] The upper and lower windows 112, 114 each comprise a generally annular body 142 of a transparent material, such as quartz, that allows radiant heating light to pass into the process chamber 102 to irradiate the preheat ring 126, the susceptor 120, and the substrate 104. The windows 112, 114 may be planar, or as shown in FIG. 1, the windows 112, 114 may have a generally dome-shaped configuration and / or a reentrant configuration. With particular reference to the embodiment shown in FIG. 1, the lower window 114 has a generally dome-shaped configuration and the upper window has an reentrant configuration. The upper and lower windows 112, 114 are coupled or connected (terms used interchangeably herein) to the upper and lower chamber walls 130, 132, respectively, of the process chamber 102. In particular, the upper window 112 includes a rim 138, or more broadly a frame, that is attached to the upper chamber wall 130. Alternatively, the upper window 112 may not include the rim 138 and may be coupled to the upper chamber wall 130 in any manner that enables the upper window 112 to function as described herein.

[0023] The upper window 112 further includes a transparent body 142 attached or optionally connected to the rim 138 and extending between an upper concave surface 144 and a lower convex surface 146 of the upper window 112. The upper surface 144 and the lower surface 146 each circumscribe the interior of the rim 138. The upper surface 144 faces away from the substrate 104. The lower surface 146 is oriented to face the substrate 104. As shown in FIG. 1, the upper surface 144 is substantially curved corresponding to the lower surface 146. Alternatively, the upper concave surface 144 is shaped in any manner that enables the upper window 112 to function as described herein. For example, without limitation, in some alternative embodiments, the upper surface 144 can have a generally planar and / or dome-shaped configuration.

[0024] The lower surface 146 of the upper window 112 and the susceptor 120 can define a longitudinal gap therebetween, generally indicated at 147. The gap 147 is sized to direct the gases 110 entering from the gas inlet 103 along the substrate surface 116 to the gas outlet 105 when the substrate is placed within the susceptor. In an exemplary embodiment, the gap 147 is approximately 20 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 more detail below, the lower surface 146 is shaped to direct the process gases 110 onto the substrate during operation of the CVD system to provide a substantially uniform deposition on the substrate 104.

[0025] Figure 2 is an enlarged view of a portion of the CVD system 100, and Figure 3 is a bottom view of the upper window 112. Figure 4 is an enlarged cross-sectional view of a portion of the upper window 112 shown in Figure 2. Referring now to Figure 2, from which a portion of the CVD system 100 has been removed for purposes of illustration, the shape of the upper window 112 is shown in greater detail. It will be understood that the dimensions of the upper window 112 are not drawn to scale in Figure 2, and more particularly, the curvature of the upper window 112 has been exaggerated for purposes of illustration.

[0026] As shown in FIG. 2, the lower surface 146 defines a nadir point generally designated 148. In particular, as described herein, the nadir point 148 of the lower surface 146 is the point at which the gap 147 defined between the lower surface 146 and the substrate surface 116 is narrowest. For example, as shown in FIG. 2, the nadir point 148 is spaced from the substrate 104 by a gap distance designated G1. As shown in FIG. 3, the nadir point 148 of the lower surface 146 may be located at the radial center of the lower surface 146, or more generally, at the radial center of the upper window 112. Alternatively, the upper window 112 may be shaped such that the nadir point of the upper window 112 is spaced from the radial center of the upper window 112. Additionally, as shown in FIG. 2, the nadir point 148 may be vertically aligned with the radial center of the substrate 104.

[0027] The lower surface 146 of the upper window 112 includes a radially outer peripheral surface 150 and a radially inner peripheral surface 152 circumferentially disposed within the outer peripheral surface 150. More specifically, as shown in the embodiment of FIG. 2, the outer peripheral surface 150 extends radially inwardly a first radial distance, designated R1, from the rim 138 to the inner peripheral surface 152. The outer peripheral surface 150 is curved such that the outer peripheral surface also extends a height, generally designated H1, from the rim 138 to the inner peripheral surface 152. More specifically, in the exemplary embodiment, the outer peripheral surface 150 of the lower surface 146 has a constant curvature between the rim 138 and the inner peripheral surface 152. Alternatively, the outer peripheral surface 150 may include multiple surfaces having varying curvatures relative to one another.

[0028] The inner circumferential surface 152 of the lower surface 146 extends a second radial distance, indicated as R2, between the outer circumferential surface 150 and the lowest point 148 of the upper window 112 (which in the illustrated embodiment is also the "radial center" of the upper window). The radius R2 of the inner circumferential surface 152 may be between 5 and 200 millimeters, between 25 and 125 millimeters, between 50 and 100 millimeters, or between 70 and 90 millimeters. In the embodiment of FIG. 2, the radius R2 of the inner circumferential surface 152 is about 75 millimeters. The inner circumferential surface 152 may also be curved to extend a height, indicated as H2, between the outer circumferential surface 150 and the lowest point 148 (i.e., the radial center) of the upper window 112. 2, the inner circumferential surface 152 has a constant curvature from the outer circumferential surface 150 to the nadir 148 and from the nadir 148 to a diametrically opposite portion of the outer circumferential surface 150. Alternatively, the inner circumferential surface 152 can include multiple surfaces having varying curvatures relative to one another.

[0029] The lower surface 146 extends from the rim 138 to a lowest point 148 with an overall height indicated as H3. More specifically, in the embodiment shown in FIG. 2, the overall height H3 is equal to the sum of the height H1 of the outer circumferential surface 150 and the height H2 of the inner circumferential surface 152. The overall height H3 may be between 6 millimeters and 20 millimeters, 8 millimeters and 16 millimeters, or 9 millimeters and 12 millimeters. In the embodiment of FIG. 2, the overall height H3 of the lower surface 146 is approximately 10 millimeters.

[0030] As shown in Figures 2 and 4, in an exemplary embodiment, the outer circumferential surface 150 has a greater curvature than the inner circumferential surface 152 such that the inner circumferential surface 152 has a greater radius of curvature than the outer circumferential surface 150. As a result, as shown in Figures 3 and 4, the lower surface 146 defines a circumferentially extending curved boundary 149 of the lower surface 146 at the intersection of the inner circumferential surface 152 and the outer circumferential surface 150. The outer circumferential surface 150 may have a radius of curvature that is at least twice the radius of curvature of the inner circumferential surface 152. The radius of curvature of the outer circumferential surface 150 is preferably 700 millimeters to 1,500 millimeters, 800 millimeters to 1,400 millimeters, or 900 millimeters to 1,300 millimeters. In the embodiment shown in Figure 2, the radius of curvature of the outer circumferential surface 150 is 1,260 millimeters. The radius of curvature of the inner peripheral surface 152 is preferably 3,000 to 13,000 millimeters, 6,000 to 10,000 millimeters, or 7,000 to 9,000 millimeters. In the embodiment shown in FIG. 2, the radius of curvature of the inner peripheral surface 152 is 8000 millimeters. The ratio of the radius of curvature of the inner peripheral surface 152 to the radius of curvature of the outer peripheral surface 150 is preferably 100: to 1.1:1, 20: to 2:1, 13: to 4:1, or 10:1 to 5:1. In the embodiment shown in FIG. 2, the ratio of the radius of curvature of the inner peripheral surface 152 to the radius of curvature of the outer peripheral surface 150 is about 6:1.

[0031] The upper window 112 is preferably sized such that at least a portion of the outer peripheral surface 150 and at least a portion of the inner peripheral surface 152 vertically cover (i.e., are vertically aligned with) the substrate surface 116. In particular, the ratio of the radius of the substrate 104 to the radius R2 of the inner peripheral surface 152 is 4: to 5: 1, 3: 1 to 1: 1, or 2.5: 1 to 1.5: 1. In the embodiment shown in FIG. 2, the ratio of the radius of the substrate 104 to the radius R2 of the inner peripheral surface 152 is about 2: 1. More specifically, the radius R2 of the inner peripheral surface 152 is about 75 millimeters and the radius of the substrate 104 is about 150 millimeters. In an alternative embodiment, the radius R2 of the inner peripheral surface 152 is about 100 millimeters and the radius of the substrate 104 is about 150 millimeters. In an alternative embodiment, the upper window 112 can be sized such that the outer periphery 150 is radially spaced from the substrate 104 and only the inner periphery 152 perpendicularly covers the substrate surface 116 .

[0032] In operation, gas 110 is introduced into the CVD system 100 through a gas inlet port at a selected flow rate. The gas may then flow into an air gap 147 defined between the lower surface 146 and the susceptor 120 and / or substrate 104. More specifically, at least a portion of the gas may flow along an outer circumferential surface 150 of the lower surface 146 to an inner circumferential surface 152. The gas 110 may then flow into a narrow portion of the gap 147 between the inner circumferential surface and the substrate 104. Due at least in part to the configuration of the outer circumferential surface 150 and the inner circumferential surface 152, the gap 147 may be narrow at the center of the substrate 104, while the curvature of the inner circumferential surface 152 may be relatively small (i.e., the radius of curvature of the inner circumferential surface 152 may be relatively large) as compared to at least some conventional upper windows. The narrow gap 147 at the center of the substrate, in combination with the relatively small curvature of the upper window 112 proximate the center of the substrate 104, facilitates providing laminar gas flow around the center of the substrate 104 and prevents the formation of a "dip" or depression in the epitaxial deposition surrounding the center of the substrate 104.

[0033] Working Example The windows for the CVD systems of the present disclosure are further illustrated by the following examples, which should not be construed in a limiting sense.

[0034] Example 1: Thickness profile variation In the first example, the thickness profile of the epitaxy deposition on the substrate was measured for different top windows with different bottom surfaces. Specifically, a large curvature window, a small curvature window, and two windows with double curvature bottom surfaces were tested in a CVD system. Specifically, each window was tested in an Applied Materials EPI Centura 300 system. The CVD system was controlled to deposit an epitaxy film on a cylindrical substrate with a diameter of 300 mm. Specifically, the CVD system was controlled to deposit a film on the substrate at a growth rate of about 1.4 μm / min (microns per minute) for each test window. The thickness variation was measured by determining the difference between the maximum and minimum thicknesses in the radial range of the substrate. For example, the substrate radial ranges were -100 mm to -50 mm, -50 mm to 0 mm, 0 mm to 50 mm, and 50 mm to 100 mm, with the 0 mm position representing the radial center of the substrate. The representative dip value for each test was calculated by averaging the thickness variation values ​​for each substrate diameter range.

[0035] As shown in Table 1 below, the large curvature window had a lower surface with a single radius of curvature of 3,556 millimeters, the small curvature window had a lower surface with a single radius of curvature of 8,070 millimeters, the first double curve window had a lower surface with an outer periphery with a radius of curvature of 1,260 millimeters and an inner periphery with a radius of curvature of 8,000 millimeters, the second double curve window had a lower surface with an outer periphery with a radius of curvature of 910 millimeters and an inner periphery with a radius of curvature of 8,000 millimeters, the inner periphery of the first double curve window had a radius of 75 millimeters, and the inner periphery of the second double curve window had a radius of 100 millimeters.

[0036] The large curvature window was positioned in the CVD system such that the gap between the large curvature window and the substrate (e.g., similar to gap 147 described above with respect to FIG. 1) was approximately 23 millimeters at its narrowest point. In other words, the distance between the lowest point of the upper window (e.g., similar to point 148 described above with respect to FIGS. 2 and 3) and the substrate was approximately 23 millimeters. The first and second double curvature windows were positioned at substantially the same location as the large curvature. Due to the large curvature of the outer periphery of the double curvature window, the gap between the substrate and the double curvature window was approximately 20 millimeters at its narrowest point. Additionally, the small curvature window was positioned such that the gap between the substrate and the window was approximately 20 millimeters at its narrowest point.

[0037] Table 1: Epitaxy Profile Test Windows 1-4 TIFF0007607748000001.tif159163

[0038] As shown in Table 1 provided above, the first and second double curvature windows each provided lower relative thickness variation (i.e., improved thickness uniformity) than both the large and small curvature windows. Additionally, the first and second double curvature windows each provided smaller typical dips than the large curvature window. The "relative layer thickness variation" of a deposited layer is determined by measuring the difference between the maximum and minimum layer thicknesses and dividing this difference by the average layer thickness. The resulting number is multiplied by 100 to obtain a percentage. This percentage is the "relative layer thickness variation" disclosed herein.

[0039] 5-8 are graphs showing measurements of the thickness profile of the epitaxy deposited on the substrate surface for each test window. The Y-axis of the graphs represents the thickness of the epitaxy deposited on the substrate surface in nanometers, with zero calibrated to the lowest thickness measured on the substrate. The X-axis of the graphs shows the distance from the radial center of the substrate. More specifically, FIG. 5 shows the measured thickness profile 402 from the above-mentioned tests performed on the large curvature window, as described with respect to Table 1. FIG. 6 shows the measured thickness profile 502 from the above-mentioned tests performed on the small curvature window. FIG. 7 shows the measured thickness profile 602 from the above-mentioned tests performed on the first double curvature window, having an inner circumferential radius of 75 millimeters. FIG. 8 shows the measured thickness profile 702 from the above-mentioned tests performed on the second double curvature window, having an inner circumferential radius of 100 millimeters.

[0040] As shown in Figure 5, the large curvature window resulted in a large dip 404 in the epitaxy thickness profile near one-third of the radial distance from the substrate center (i.e., at ±50 millimeters from the substrate center). Additionally, the dip 504 around the ±50 millimeter portion of the substrate was less pronounced in the small curvature window than in the large curvature window, as shown in Figure 6. However, the small curvature window resulted in a high edge rise 506 in the range of -150 millimeters to -125 millimeters and 125 millimeters to 150 millimeters on the substrate.

[0041] 7 and 8, epitaxy deposited on substrates using both the first and second double curvature windows exhibited reduced dips 604, 704 in the ±50 millimeter radius range compared to the large curvature window. Additionally, epitaxy deposited on substrate surfaces exhibited reduced edge rises 606, 706 between the ranges of -150 millimeters to -125 millimeters and 125 millimeters to 150 millimeters compared to the small curvature window. As a result, the double curvature window resulted in epitaxial growth profiles with less relative thickness variation compared to the large curvature top window and the small curvature top window, respectively, as shown in Table 1 above.

[0042] Example 2: Growth rate comparison In a second example, a test window was used to measure the effect of operating a CVD system at different flow rates. In each test, the process chamber temperature was held at 1100°C.

[0043] In the first test, the large curvature window, the small curvature window, and the first double curvature top window were each tested in a CVD system, and a trichlorosilane-hydrogen mixture was introduced into the CVD system at a flow rate of 8.5 standard liters per minute. The average thickness and deposition time of the epitaxy film were measured to obtain the growth rate in microns per minute. The test results are listed in Table 2 below.

[0044] Table 2: Growth rate comparison at a flow rate of 8.5 slm TIFF0007607748000002.tif34146

[0045] As shown in Table 2 provided above, the first double curvature window resulted in increased growth rates compared to the large curvature window.

[0046] In the second test, the first double curvature window and the second double curvature window were tested in a CVD system, and the trichlorosilane-hydrogen mixture was introduced into the CVD system at a flow rate of 7.6 standard liters per minute. The average epitaxy film thickness and deposition time were measured to obtain the growth rate in microns per minute. The test results are listed in Table 3 below.

[0047] Table 3: Growth rate comparison at a flow rate of 7.6 slm TIFF0007607748000003.tif27146

[0048] As shown in Table 3 provided above, the second double curvature window provided improved growth rates compared to the first double curvature window. Additionally, the growth rate of the first double curvature window used at a flow rate of 7.6 standard liters per minute was nearly identical to the resulting growth rate of the large curvature window operating at an increased flow rate of 8.5 standard liters per minute measured in the first test.

[0049] In a CVD system including a top window as described herein, the uniformity of gas flow distribution across the substrate surface can be maintained across different gas flow rates as compared to conventional CVD systems. For example, a process gas such as a trichlorosilane-hydrogen mixture can be introduced into the CVD system at a flow rate of at least about 5 standard liters per minute, at least about 10 standard liters per minute, or even at least about 15 standard liters per minute and maintain a relative layer thickness variation across the substrate surface of less than about 4%, less than about 2%, or even less than about 1% across the substrate surface. A carrier gas such as hydrogen can also be introduced at a higher flow rate, such as at least about 70 standard liters per minute, at least about 80 standard liters per minute, or at least about 90 standard liters per minute, while maintaining a relative layer thickness variation across the substrate surface of less than about 4%, less than about 2%, or even less than about 1% across the substrate surface. The ability to maintain uniformity of gas flow distribution across the substrate surface with increased gas flow rates allows for increased rates of deposition of a given film or layer on a substrate while maintaining uniformity of layer thickness. For example, the epitaxial layer can be deposited on silicon wafers having a diameter of at least about 150 millimeters, at least about 200 millimeters, or at least about 300 millimeters while maintaining a relative layer thickness variation of less than about 4% across the diameter of the wafer, less than about 2% across the diameter of the wafer, or even less than about 1% across the diameter of the wafer.

[0050] As used herein, the term "standard liter" means one liter of a reference gas at 0° C. and 101.3 kPa (1013 mbar).

[0051] The described embodiments are suitable for processing semiconductor wafers, such as silicon wafers, but may be used in other applications. Some embodiments are particularly suitable for use in atmospheric pressure silicon-on-silicon chemical vapor deposition using gas mixtures including hydrogen, trichlorosilane, and diborane. Silicon precursors other than trichlorosilane may also be used, including higher silane precursors such as dichlorosilane, silane, trisilane, tetrachlorosilane, methylsilane, pentasilane, and neopentasilane. Precursors other than silicon precursors may also be used, including germanium precursors such as germane and digermane. Dopant gas species other than diborane may also be used, including phosphine and arsine. The described embodiments may also be used in processes other than atmospheric pressure silicon-on-silicon epitaxy, such as reduced pressure epitaxy (e.g., pressures between about 10 Torr and about 750 Torr), silicon-germanium epitaxy, carbon-doped silicon epitaxy, and non-epitaxial chemical vapor deposition. The present embodiment may also be used to process wafers other than silicon wafers, such as wafers having germanium, gallium arsenide, indium phosphide, and silicon carbide.

[0052] As discussed above, the process chamber including the top window of the present disclosure provides an improvement over known process chambers. The top window of the present disclosure includes two surfaces with different curvatures to facilitate directing the process flow during operation to provide a laminar flow of process gas across the substrate. As a result, the uniformity of the gas flow distribution at the substrate surface can be improved. More specifically, the CVD system including the top window of the present disclosure provides the following advantages over some conventional CVD systems: 1) reduced epitaxial dip on the substrate, 2) reduced epitaxial rise on the substrate near the substrate periphery, 3) reduced processing time for epitaxial growth on the substrate, and 4) improved semiconductor wafer life.

[0053] When introducing elements of the disclosure or embodiments thereof, the articles "a," "an," "the," and "said" are intended to mean that there are one or more of the element. The terms "comprising," "including," and "having" are intended to be inclusive and mean that there may be additional elements other than the listed elements.

[0054] Because various changes may be made in the structures and methods described above without departing from the scope of the present disclosure, it is intended that all matter contained in the above description and shown in the accompanying drawings be interpreted as illustrative and not in a limiting sense.

Claims

1. 1. A system for depositing a layer on a substrate, comprising: a process chamber having a gas inlet for introducing gas into the process chamber and a gas outlet for exhausting gas from the process chamber; a substrate support disposed within the process chamber and configured to receive the substrate; a top window that is transparent to allow radiant heating light to pass therethrough, the top window having a first surface spaced apart from the substrate support and defining an air gap therebetween, the top window being positioned within the process chamber to direct gas from a gas inlet, through the air gap, to a gas outlet, the first surface including a radially outer peripheral surface and a radially inner peripheral surface tangent to the outer peripheral surface, the outer peripheral surface having a first radius of curvature, the inner peripheral surface having a second radius of curvature different from the first radius of curvature, the outer peripheral surface and the inner peripheral surface each being convex, the top window including a transparent body, the transparent body including the inner peripheral surface and the outer peripheral surface; A system including:

2. 2. The system of claim 1, wherein the inner periphery is disposed to be vertically aligned with the substrate when the substrate is received on the substrate support, and the second radius of curvature is greater than the first radius of curvature.

3. The system of claim 2 , wherein a ratio of the second radius of curvature to the first radius of curvature is from 100:1 to 1.1:

1.

4. 4. The system of claim 3, wherein the ratio is from 10:1 to 5:

1.

5. The system of claim 1 , wherein the inner periphery and the outer periphery are each positioned to be vertically aligned with at least a portion of the substrate when the substrate is received on the substrate support.

6. 2. The system of claim 1, wherein the upper window further comprises a rim surrounding the first surface and configured to be coupled to the process chamber, the outer circumferential surface extending from the rim to the inner circumferential surface with a first radius of curvature.

7. 7. The system of claim 6, wherein the inner periphery extends from the outer periphery to the radial center of the upper window at a second radius of curvature.

8. The system of claim 7 , wherein the air gap is reduced between the outer periphery and the inner periphery.

9. 2. The system of claim 1, wherein the inner periphery defines a radius extending in a plane tangent to a radial center of the upper window, the radius extending from the radial center to the outer periphery, the radius of the inner periphery being between 5 millimeters and 200 millimeters.

10. 10. The system of claim 1, wherein the upper window further includes a second side opposite the first side and a body extending between the first side and the second side, the second side having a concave curvature.

11. 2. The system of claim 1, wherein the upper window further comprises a rim surrounding the first surface and configured to be coupled to the process chamber, the outer circumferential surface extending at a first height between the rim and the inner circumferential surface, the inner circumferential surface extending at a second height between the outer circumferential surface and a linear center of the upper window, the first height being greater than the second height.

12. A chemical vapor deposition system comprising: a chamber wall at least partially defining a process chamber; a substrate support disposed in the process chamber and configured to receive a substrate thereon; A window, a frame for mounting the window to the chamber wall; and a window including: a transparent body connected to the frame, the body extending between a first surface and an opposing second surface, the first surface being positioned to face the substrate support when the frame is attached to the chamber wall, the first surface including a radially outer peripheral surface and a radially inner peripheral surface tangent to the outer peripheral surface, the outer peripheral surface extending radially from the frame to the inner peripheral surface, the inner peripheral surface extending radially inward from the outer peripheral surface to a linear center of the window, the outer peripheral surface having a first radius of curvature and the inner peripheral surface having a second radius of curvature different from the first radius of curvature, the outer peripheral surface and the inner peripheral surface each being convex, the transparent body including the inner peripheral surface and the outer peripheral surface; 1. A chemical vapor deposition system comprising:

13. The chemical vapor deposition system of claim 12 , wherein the second radius of curvature is greater than the first radius of curvature.

14. 14. The chemical vapor deposition system of claim 13, wherein a ratio between the second radius of curvature and the first radius of curvature is from 100:1 to 1.1:

1.

15. 13. The chemical vapor deposition system of claim 12, wherein the outer periphery extends from the frame to the inner periphery with a first radius of curvature, and the inner periphery extends from the outer periphery to the linear center of the window with a second radius of curvature.

16. 13. The chemical vapor deposition system of claim 12, wherein the inner periphery defines a radius extending in a plane tangent to a radial center of the window, the radius extending from the radial center to the outer periphery, the radius of the inner periphery being between 5 millimeters and 200 millimeters.

17. The chemical vapor deposition system of claim 12 , wherein the second surface has a concave curvature.

18. 1. A method for depositing a layer on a substrate, comprising the steps of: providing a substrate on a substrate support in a process chamber, the process chamber including a gas inlet and a gas outlet; providing a top window in the process chamber, the top window being transparent to allow radiant heating light to pass therethrough, the top window having a first surface spaced from the substrate to define an air gap therebetween, the first surface including an outer radial surface and an inner radial surface tangent to the outer radial surface, the outer radial surface having a first radius of curvature and the inner radial surface having a second radius of curvature different from the first radius of curvature, the outer radial surface and the inner radial surface each being convex, the top window including a transparent body, the transparent body including the inner and outer radial surfaces; directing a flow of gas through a gas inlet, into an air gap between the first surface and the substrate, and to a gas outlet; The method includes:

19. 20. The method of claim 18, wherein the gas flow is provided at a flow rate of greater than 2 standard liters per minute and the variation in relative thickness of the deposited layer on the substrate is less than about 2%.

20. The system of claim 1, wherein the upper window includes a transparent body, the transparent body including an inner surface and an outer surface.

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