Windows for chemical vapor deposition systems and related methods

Abstract

A system for depositing a layer on a substrate is disclosed, comprising a process chamber defining an inlet for introducing a gas into the process chamber and an outlet for allowing the gas to exit the process chamber. A substrate support is positioned within the process chamber and is configured to receive a substrate. A transparent upper window comprises a convex first face spaced from the substrate support to define an air gap therebetween. The upper window is positioned within the process chamber to direct the gas from the inlet through the air gap to the outlet. The first face comprises 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 different from the first radius of curvature.

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims priority to U.S. Provisional Patent Application No. 62 / 706,452, filed on August 18, 2020, the entire contents of which are incorporated herein by reference. Technical Field

[0003] The field generally relates to using chemical vapor deposition systems in processing semiconductor wafers and, more particularly, to windows and methods for controlling gas flow uniformity within a chemical vapor deposition processing chamber. Background Art

[0004] In chemical vapor deposition (CVD) processes (including epitaxial growth processes), the uniformity of the thickness of the deposited film on the substrate depends on the uniformity of the flow distribution of the gas in the process chamber and other factors. As the requirements for film thickness uniformity become more stringent, the desire for a more uniform flow rate distribution of the gas in the process chamber increases.

[0005] In conventional CVD apparatus, source gas is introduced into the process chamber through a gas manifold and directed between an upper window of the process chamber and a gap between a substrate positioned on a substrate support. The upper window of conventional CVD apparatus does not direct uniform gas flow distribution across the substrate surface in the process chamber.

[0006] For example, some conventional upper windows include a curved surface across the process chamber and facing the substrate, which may be convex to sink toward the center of the substrate. However, such conventional upper windows may generate turbulent airflow around the substrate, thereby causing epitaxial sinking or depression of the deposited substrate.

[0007] Additionally, some conventional CVD systems attempt to minimize the sink depth of the epitaxial thickness profile by operating at a reduced growth rate (e.g., lower deposition temperatures within the process chamber and / or at reduced gas flow rates). However, such an operating system results in longer processing times and only modest changes in the sink depth of the deposited epitaxy.

[0008] Therefore, there is a need for an upper window that can direct a more uniform flow distribution across the surface of a substrate within a processing chamber.

[0009] This background technology section is intended to introduce the reader to various technical aspects that may be related to various aspects of the present disclosure that will be described and / or claimed below. This discussion is considered helpful in providing the reader with background information to facilitate a better understanding of the various aspects of the present disclosure. Therefore, it should be understood that these statements should be interpreted in this light, and not as an admission of prior art. Summary of the invention

[0010] One aspect of the present disclosure is directed to a system for depositing a layer on a substrate. The system includes a process chamber defining an inlet for introducing a gas into the process chamber and an outlet for allowing the gas to exit the process chamber. A substrate support is positioned within the process 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 process chamber to direct the gas from the inlet through the air gap to the 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 different from the first radius of curvature.

[0011] 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 different from the first radius of curvature.

[0012] Yet another aspect of the present disclosure is directed to a method for depositing a layer on a substrate. The method includes providing a substrate on a substrate support within a processing chamber. The processing chamber includes an air inlet and an air outlet. The method further includes providing an upper window in the processing chamber. The upper window is transparent to allow 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 radial outer surface and a radial 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 different from the first radius of curvature. The method further includes directing a gas flow through the air inlet into the air gap between the first face and the substrate and to the air outlet.

[0013] There are various improvements to the features mentioned in the above aspects. Further features may also be incorporated into the above aspects. These improvements and additional features may exist individually or in any combination. For example, various features discussed below with respect to any of the illustrative embodiments may be incorporated into any of the above aspects individually or in any combination. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 is a cross-section of a chemical vapor deposition system including an upper window according to one embodiment of the present disclosure;

[0015] Figure 2 yes Figure 1 An enlarged cross-section of a chemical vapor deposition system of FIG. 1 with portions of the chemical vapor deposition system removed for illustration.

[0016] Figure 3 yes Figure 2 Bottom view of the upper window shown in FIG.

[0017] Figure 4 yes Figure 2 An enlarged cross-section of a portion of the upper window shown in FIG.

[0018] Figure 5 is a graph showing the thickness profile of epitaxy deposited on a substrate surface in a CVD system using an upper window having a single large curvature.

[0019] Figure 6 is a graph showing the thickness profile of epitaxy deposited on a substrate surface in a CVD system using an upper window having a single small curvature.

[0020] Figure 7 is a graph showing the thickness profile of epitaxy deposited on a substrate surface in a CVD system using a first double curvature upper window.

[0021] Figure 8 is a graph showing the thickness profile of epitaxy deposited on a substrate surface in a CVD system using a second double curvature upper window.

[0022] The same reference numbers used in the various drawings indicate the same components. DETAILED DESCRIPTION

[0023] Chemical vapor deposition (CVD) systems (also referred to herein as "substrate processing systems") are used in Figure 1 100. The illustrated system is a single substrate system, however, the systems 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. An example of a CVD system suitable for use according to the present disclosure is the Applied Materials EPI Centura 300.

[0024] As used herein, the term "curvature" refers to the amount by which the curve of a surface and / or 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 that matches 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. Similarly, 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.

[0025] The CVD system 100 includes a reaction or processing chamber 102 for depositing and / or growing thin films on a substrate 104, such as a semiconductor wafer, a gas injection port 106 disposed at an end of the processing chamber 102, and a gas exhaust port 108 disposed at an opposite end of the processing chamber 102. A gas manifold 140 disposed between the gas injection port 106 and the processing chamber 102 is used to guide an input gas 110 through the gas injection port 106 into the processing chamber 102 enclosed by an upper window 112 and a lower window 114. The gas manifold 140 includes an injector baffle or gas distribution plate disposed between the gas injection port 106 and the processing chamber 102 and an implant insert liner assembly 170 disposed adjacent to the baffle and upstream of the processing chamber 102. In operation, the input process gas 110 flows through the gas manifold 140 into the processing chamber 102 through the gas inlet 103. The gas 110 then flows over the substrate surface 116 and reacts with the substrate surface 116 or a precursor disposed thereon to deposit a film on the substrate surface 116. The gas 110 then flows out of the processing chamber 102 and through the gas exhaust port 108.

[0026] The substrate 104 on which the film is deposited is supported by a susceptor 120 within the processing chamber 102. The susceptor 120 is connected to a shaft 122, which is connected to a motor (not shown) of a rotation mechanism (not shown) to rotate the shaft 122, the susceptor 120, and the substrate 104 about a vertical axis X of the CVD system 100. The outer edge 124 of the susceptor 120 and the inner edge of a preheat ring 126 (used to heat the input gas 110 prior to contact with the substrate 104) are separated by a gap to allow the susceptor 120 to rotate. The substrate 104 is rotated to prevent excess material from being deposited on the leading edge of the wafer and to provide a more uniform epitaxial layer.

[0027] The input gas 110 may be heated before contacting the substrate 104. Both the preheat ring 126 and the susceptor 120 are generally opaque to absorb radiant heating light (e.g., infrared light) generated by high intensity radiant heating lamps 128 that may be located above the processing chamber 102 and below the processing chamber 102. Equipment other than the high intensity lamps 128 may be used to provide heat to the processing chamber 102, such as, for example, resistive heaters and induction heaters. Maintaining the preheat ring 126 and the susceptor 120 at a temperature above ambient allows the preheat ring 126 and the susceptor 120 to transfer heat to the input gas 110 as the gas 110 passes over the preheat ring 126 and the susceptor 120. The diameter of the substrate 104 may be smaller than the diameter of the susceptor 120 to allow the susceptor 120 to heat the input gas 110 before the input gas 110 contacts the substrate 104. The preheat ring 126 and the susceptor 120 may be composed of opaque graphite coated with silicon carbide.

[0028] The upper chamber wall 130 and the lower chamber wall 132 define the outer periphery of the processing chamber 102 and contact the gas injection port 106 and the gas exhaust port 108 .

[0029] CVD system 100 may include upper and lower liners 134, 136 disposed within the processing chamber to prevent reaction between gas 110 and chamber walls 130, 132 (which are typically made of a metallic material such as stainless steel). Liners 134, 136 may be made of a suitable non-reactive material such as quartz.

[0030] The upper and lower windows 112, 114 each include a generally annular body 142 made of a transparent material such as quartz to allow radiant heating light to pass into the processing chamber 102 and onto the preheat ring 126, the susceptor 120 and the substrate 104. The windows 112, 114 may be planar or may be as Figure 1 As shown in FIG. 1 , the windows 112, 114 may have a generally dome-shaped configuration and / or a concave configuration. Figure 1 , the lower window 114 has a generally dome-shaped configuration and the upper window has a concave configuration. The upper and lower windows 112, 114 are each coupled or connected (the terms are used interchangeably herein) to upper and lower chamber walls 130, 132, respectively, of the processing chamber 102. In particular, the upper window 112 includes a rim 138, or more generally, a frame, attached to the upper chamber wall 130. Alternatively, the upper window 112 does not include a rim 138 and is coupled to the upper chamber wall 130 in any manner that enables the upper window 112 to function as described herein.

[0031] 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 are each circumscribed within the rim 138. The upper surface 144 is oriented away from the substrate 104. The lower surface 146 is oriented toward the substrate 104. Figure 1 , the upper surface 144 is generally 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, but not limited to, in some alternative embodiments, the upper surface 144 may have a generally planar and / or dome-shaped configuration.

[0032] The lower face 146 of the upper window 112 and the susceptor 120 may define a longitudinal gap therebetween, generally indicated at 147. The gap 147 is sized to direct the input gas 110 from the gas inlet 103 along the substrate surface 116 to the gas outlet 105 when the substrate is positioned 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 will be described in more detail below, the lower face 146 is shaped to direct the process gas 110 over the substrate during operation of the CVD system to provide a substantially uniform vapor deposition on the substrate 104.

[0033] Figure 2 shows an enlarged view of a portion of the CVD system 100, and Figure 3 A bottom view of the upper window 112 is shown. Figure 4 yes Figure 2 FIG. 1 is an enlarged cross-section of a portion of the upper window 112 shown in FIG. Figure 2 (wherein portions of the CVD system 100 have been removed for illustration) the shape of the upper window 112 is shown in more detail. It should be understood that the size of the upper window 112 is Figure 2 1 is not drawn to scale, and more particularly, the curvature of the upper window 112 has been exaggerated for illustration.

[0034] like Figure 2 , the lower face 146 defines a lowest point generally indicated at 148. In particular, as described herein, the lowest point 148 of the lower face 146 is the point where the gap 147 defined between the lower face 146 and the substrate surface 116 is the narrowest. Figure 2 As shown in FIG. 1 , the lowest point 148 is spaced from the substrate 104 by a gap distance (indicated by G1). Figure 3 , the lowest point 148 of the lower face 146 is also located at the radial center of the lower face 146, or more generally, at the radial center of the upper window 112. Alternatively, the upper window 112 may be shaped so that the lowest point of the upper window 112 is spaced from the radial center of the upper window 112. In addition, as shown in FIG. Figure 2 As shown in , the lowest point 148 can be vertically aligned with the radial center of the substrate 104.

[0035] The lower surface 146 of the upper window 112 includes a radial outer surface 150 and a radial inner surface 152 circumscribed within the outer surface 150. More specifically, Figure 21, the outer surface 150 extends a first radial distance (indicated by R1) from the rim 138 radially inward to the inner surface 152. The outer surface 150 is curved such that the outer surface also extends a certain height (generally indicated by H1) from the rim 138 to the inner surface 152. More specifically, in the example embodiment, the outer surface 150 of the lower face 146 has a constant curvature between the rim 138 and the inner surface 152. Alternatively, the outer surface 150 may include multiple surfaces having varying curvatures relative to each other.

[0036] The inner surface 152 of the lower face 146 extends a second radial distance (indicated by R2) between the outer surface 150 of the upper window 112 and the lowest point 148 in a plane tangent to the lowest point 148 (also referred to as the "radial center" of the upper window in the example embodiment). The radius R2 of the inner surface 152 can be between 5 mm and 200 mm, between 25 mm and 125 mm, between 50 mm and 100 mm, or between 70 mm and 90 mm. Figure 2 In the embodiment of FIG. 1 , the radius R2 of the inner surface 152 is approximately 75 mm. The inner surface 152 may also be curved so that the inner surface 152 also extends a certain height (indicated by H2) between the outer surface 150 of the upper window 112 and the lowest point 148 (i.e., the radial center). Figure 2 In the embodiment shown in FIG. 1 , the inner surface 152 has a constant curvature from the outer surface 150 to the lowest point 148 and from the lowest point 148 to the diametrically opposed portion of the outer surface 150. Alternatively, the inner surface 152 may include multiple surfaces having varying curvatures relative to each other.

[0037] The lower side 146 extends from the edge 138 to the lowest point 148 to a certain total height (indicated by H3). Figure 2 In the illustrated embodiment, the total height H3 is equal to the sum of the height H1 of the outer surface 150 and the height H2 of the inner surface 152. The total height H3 may be between 6 mm and 20 mm, between 8 mm and 16 mm, or between 9 mm and 12 mm. Figure 2 In the embodiment, the total height H3 of the lower surface 146 is approximately 10 mm.

[0038] like Figure 2 and 4 As shown in , in the example embodiment, the outer surface 150 has a greater curvature than the inner surface 152, so that the inner surface 152 has a greater radius of curvature than the outer surface 150. Figure 3 and 4, the lower face 146 defines a curvilinear boundary 149 extending circumferentially around the lower face 146 at the intersection of the inner surface 152 and the outer surface 150. The outer surface 150 has a radius of curvature that is at least twice the radius of curvature of the inner surface 152. The radius of curvature of the outer surface 150 is suitably between 700 mm and 1,500 mm, between 800 mm and 1,400 mm, or between 900 mm and 1300 mm. Figure 2 In the illustrated embodiment, the radius of curvature of the outer surface 150 is 1,260 mm. The radius of curvature of the inner surface 152 is suitably between 3,000 mm and 13,000 mm, between 6,000 mm and 10,000 mm, or between 7,000 mm and 9,000 mm. Figure 2 In the illustrated embodiment, the radius of curvature of the inner surface 152 is 8,000 mm. The ratio of the radius of curvature of the inner surface 152 to the radius of curvature of the outer surface 150 is suitably between 100:1 and 1.1:1, between 20:1 and 2:1, between 13:1 and 4:1, or between 10:1 and 5:1. Figure 2 In the illustrated embodiment, the ratio of the radius of curvature of the inner surface 152 to the radius of curvature of the outer surface 150 is approximately 6:1.

[0039] The upper window 112 is appropriately sized so that at least a portion of the outer surface 150 and at least a portion of the inner surface 152 vertically overlap (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 surface 152 can be between 4:1 and .5:1, between 3:1 and 1:1, or between 2.5:1 and 1.5:1. Figure 2 In the illustrated embodiment, the ratio of the radius of the substrate 104 to the radius R2 of the inner surface 152 is approximately 2:1. More specifically, the radius R2 of the inner surface 152 is approximately 75 mm and the radius of the substrate 104 is approximately 150 mm. In an alternative embodiment, the radius R2 of the inner surface 152 is approximately 100 mm and the radius of the substrate 104 is approximately 150 mm. In an alternative embodiment, the upper window 112 may be sized such that the outer surface 150 is radially spaced from the substrate 104 and only the inner surface 152 vertically covers the substrate surface 116.

[0040] In operation, gas 110 is introduced into CVD system 100 from a gas injection port at a selected flow rate. The gas may then flow into an air gap 147 defined between lower face 146 and susceptor 120 and / or substrate 104. More specifically, at least a portion of the gas may flow along outer surface 150 of lower face 146 to inner surface 152. The gas 110 may then flow into a narrower portion of gap 147 between the inner surface and substrate 104. Due at least in part to the configuration of outer surface 150 and inner surface 152, gap 147 may be narrower at the center of substrate 104, while the curvature of inner surface 152 may be relatively smaller (i.e., the radius of curvature of inner surface 152 may be relatively larger) than at least some conventional upper windows. The combination of narrow gap 147 at the center of the substrate and the relatively small curvature of upper window 112 proximate the center of substrate 104 facilitates providing laminar gas flow around the center of substrate 104 and inhibits formation of a "sink" or depression of epitaxial deposition around the center of substrate 104.

[0041] Examples

[0042] The windows for the CVD systems of the present disclosure are further illustrated by the following examples. These examples should not be construed as intended to be limiting.

[0043] Example 1: Thickness Profile Change

[0044] In a first example, the thickness profile of epitaxial deposition on a substrate is measured for different upper windows with different lower surfaces. Specifically, a large curvature window, a small curvature window, and two windows with a double curvature lower surface are tested in a CVD system. More specifically, each of the windows is tested in an Applied Materials EPI Centura 300 system. The CVD system is controlled to deposit an epitaxial film on a cylindrical substrate with a diameter of 300 mm. Specifically, the CVD system is controlled to deposit a film on the substrate at a growth rate of about 1.4 um / min (micrometers / minute) for each of the test windows. The thickness variation value is measured by determining the difference between the maximum thickness and the minimum thickness within the radial range of the substrate. For example, the radial range of the substrate includes -100 mm to -50 mm, -50 mm to 0 mm, 0 mm to 50 mm, and 50 mm to 100 mm, wherein the 0 mm position indicates the radial center of the substrate. The typical sinking value of each in the test is calculated by averaging the thickness variation value within each of the substrate diameter ranges.

[0045] As shown in Table 1 provided below, the large curvature window includes a lower surface with a single curvature radius of 3,556 mm, the small curvature window includes a lower surface with a single curvature radius of 8,070 mm, and the first double curvature window has a lower surface with an outer surface with a curvature radius of 1,260 mm and an inner surface with a curvature radius of 8,000 mm. The second double curvature window has a lower surface with an outer surface with a curvature radius of 910 mm and an inner surface with a curvature radius of 8,000 mm. The inner surface of the first double curvature window has a radius of 75 mm, and the inner surface of the second double curvature window has a radius of 100 mm.

[0046] The large curvature window is positioned in the CVD system so that the gap between the large curvature window and the substrate (e.g., similar to that described above with respect to Figure 1 The gap 147 described above) is about 23 mm at its narrowest point. In other words, the lowest point of the upper window (e.g., similar to the above description of Figure 2 and 3 The distance between the point 148 described and the substrate is about 23 mm. The first and second double curvature windows are positioned in a substantially similar manner to the large curvature. Due to the larger curvature outer surface of the double curvature window, the gap between the substrate and each of the double curvature windows is about 20 mm at its narrowest point. The small curvature window is also positioned so that the gap between the substrate and the window is about 20 mm at its narrowest point.

[0047] Table 1 : Epitaxial profile test windows 1 to 4

[0048]

[0049]

[0050] As shown in Table 1 provided above, the first and second double curvature windows each result in a lower relative thickness variation (i.e., improved thickness uniformity) than both the large and small curvature windows. In addition, the first and second double curvature windows each result in a smaller typical sag than the large curvature window. The "relative layer thickness variation" of the 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 resulting value is multiplied by 100 to obtain a percentage. This percentage is the "relative layer thickness variation" disclosed herein.

[0051] Figures 5 to 8 is a graph showing the measured thickness profile of the epitaxy deposited on the substrate surface for each of the test windows. The Y-axis in the graph represents the thickness of the epitaxy deposited on the substrate surface in nanometers, and zero is adjusted according 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, Figure 5 A measured thickness profile 402 is shown from the above-described test described with respect to Table 1 performed on a large curvature window. Figure 6 A measured thickness profile 502 is shown from the above-described test performed on a large curvature window. Figure 7 A measured thickness profile 602 is shown from the above-described test performed on a first double curvature window having an inner surface radius of 75 millimeters. Figure 8 A measured thickness profile 702 is shown from the above-described test performed on a second double curvature window having an inner surface radius of 100 millimeters.

[0052] like Figure 5 As shown in , the large curvature window causes the epitaxial thickness profile to dip significantly 404 at about 1 / 3 of the radial distance from the center of the substrate (i.e., at + / - 50 mm from the center of the substrate). Figure 6 As shown in FIG. 5 , the dip 504 at about + / - 50 mm portion of the substrate of the small curvature window is less obvious than that of the large curvature window. However, the small curvature window causes a high edge rise 506 on the substrate between the range of -150 mm to -125 mm and between the range of 125 mm to 150 mm.

[0053] refer to Figure 7 and 8 , epitaxy deposited on the substrate using both the first and second double curvature windows has reduced dip 604, 704 within a radius of + / -50 mm compared to the large curvature window. Additionally, epitaxy deposited on the substrate surface has reduced edge rise 606, 706 between the range of -150 mm to -125 mm and between the range of 125 mm to 150 mm compared to the small curvature window. Thus, as shown in Table 1 provided above, the double curvature windows each result in an epitaxial deposition profile with lower relative thickness variation compared to the large and small curvature upper windows.

[0054] Example 2: Growth rate comparison

[0055] In a second example, a test window was used to measure the effect of operating a CVD system at different flow rates. For each test, the temperature of the process chamber was maintained at 1100 degrees Celsius.

[0056] In the first test, each of the large curvature window, the small curvature window and the first double curvature upper window was 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 / minute. The average thickness of the epitaxial deposition and the deposition time were measured to determine the growth rate (in micrometers / minute). The results of the test are provided in Table 2 below.

[0057] Table 2 : Growth rate comparison at a flow rate of 8.5slm

[0058] Average thickness(um) Deposition time (sec) Growth rate (um / min) Large curvature window 2.442 102.5 1.435 Small curvature window 3.283 120 1.641 Hyperbolic Window #1 2.64 102.5 1.551

[0059] As shown in Table 2 provided above, the first double curvature window results in an increased growth rate relative to the large curvature window.

[0060] In a second test, each of the first and second hyperbolic windows was tested in a CVD system and a trichlorosilane-hydrogen mixture was introduced into the CVD system at a flow rate of 7.6 standard liters / minute. The average thickness of the epitaxial deposition and the deposition time were measured to determine the growth rate (in micrometers / minute). The results of the test are provided in Table 3 below.

[0061] Table 3 : Growth rate comparison at a flow rate of 7.6slm

[0062] Average thickness(um) Deposition time (sec) Growth rate (um / min) Hyperbolic Window #1 2.431 102.5 1.428 Hyperbolic Window #2 2.519 102.5 1.481

[0063] As shown in Table 3 provided above, the second double curvature window resulted in an increased growth rate relative to the first double curvature window. In addition, the growth rate using the first double curvature window at a flow rate of 7.6 standard liters / minute was approximately the same as the growth rate measured in the first test caused by the large curvature window operating at an increased flow rate of 8.5 standard liters / minute.

[0064] In a CVD system including an upper window as described herein, uniformity of gas flow distribution across a substrate surface can be maintained between different gas flow rates compared to conventional CVD systems. For example, a process gas (e.g., a trichlorosilane-hydrogen mixture) can be introduced into a CVD system at a flow rate of at least about 5 standard liters / minute, at least about 10 standard liters / minute, or even at least about 15 standard liters / minute while maintaining a relative layer thickness variation of less than about 4% across the substrate surface, less than about 2% across the substrate surface, or even less than about 1% across the substrate surface. A carrier gas (e.g., hydrogen) can also be introduced at a higher flow rate (e.g., at least about 70 standard liters / minute, at least about 80 standard liters / minute, or even at least about 90 standard liters / minute) while maintaining a relative layer thickness variation of less than about 4% across the substrate surface, less than about 2% across the substrate surface, or even less than about 1% across the substrate surface. Because uniformity of gas flow distribution across a substrate surface can be maintained at higher gas flow rates, the rate at which a given film or layer is deposited on a substrate can also be increased while maintaining uniformity of layer thickness. For example, the epitaxial layer may be deposited on a silicon wafer having a diameter of at least about 150 mm, at least about 200 mm, at least about 300 mm, while maintaining a relative layer thickness variation of less than about 4% across the diameter of the silicon wafer, less than about 2% across the diameter of the silicon wafer, or even less than about 1% across the diameter of the silicon wafer.

[0065] As used herein, the term "standard liter" refers to one liter of reference gas at 0°C and 101.3 kPa (1013 millibars).

[0066] The described examples are suitable for processing semiconductor wafers (e.g., silicon wafers), but may also be used in other applications. Some examples are particularly suitable for use in atmospheric pressure silicon-on-silicon chemical vapor deposition epitaxy using a gas mixture comprising 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. Doping gas species other than diborane may be used, including phosphine and arsine. The described examples may also be used in processes other than atmospheric pressure silicon-on-silicon epitaxy, including 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. Examples may also be used to process wafers other than silicon wafers, including wafers having germanium, gallium arsenide, indium phosphide, and silicon carbide.

[0067] As described above, a processing chamber including an upper window of the present disclosure provides improvements over known processing chambers. The upper window of the present disclosure includes two surfaces having different curvatures to guide the process flow during operation and facilitate providing a laminar flow of the process gas across the substrate. Therefore, the uniformity of the gas flow distribution across the substrate surface can be improved. More specifically, a CVD system including an upper window of the present disclosure provides the following advantages over some conventional CVD systems: 1) reduced epitaxial sinking on the substrate; 2) reduced epitaxial rise on the substrate near the outer periphery of the substrate; 3) reduced processing time for epitaxial deposition on the substrate; and 4) extended life of the semiconductor wafer.

[0068] When introducing elements of the present disclosure or embodiments thereof, the articles “a,” “an,” and “the,” are intended to mean that there are one or more of the elements. The terms “comprising,” “including,” and “having” are intended to be inclusive and mean that there may be additional elements other than the listed elements.

[0069] As various changes could be made in the above constructions and methods 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 shall be interpreted as illustrative and not in a limiting sense.

Claims

1. A system for depositing a layer on a substrate, the system comprising: a processing chamber defining a gas inlet for introducing a gas into the processing chamber and a gas outlet for allowing 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 that is transparent to allow radiant heating light to pass through the upper window, the upper window having a first face that is spaced from the substrate support to define an air gap therebetween, the upper window being positioned within the processing chamber to guide the gas from the gas inlet through the air gap to the gas outlet, the first face comprising a radially outer surface and a radially inner surface circumscribed within the outer surface, the outer surface having a first radius of curvature, and the inner surface having a second radius of curvature that is different from the first radius of curvature, wherein each of the outer surface and the inner surface is convex, and wherein a portion of the air gap defined by the outer surface and the substrate support is larger than a portion of the air gap defined by the inner surface and the substrate support.

2. The system of claim 1, wherein the inner surface is positioned in vertical alignment with the substrate when the substrate is received on the substrate support, and wherein the second radius of curvature is greater than the first radius of curvature.

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

1.

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

1.

5. The system of claim 1, wherein the inner surface and the outer surface are each positioned in vertical alignment with at least a portion of the substrate when the substrate is received on the substrate support.

6. The system of claim 1, wherein the upper window further comprises a rim circumscribing the first face and configured to be coupled to the processing chamber, and wherein the outer surface extends from the rim to the inner surface at the first radius of curvature.

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

8. The system of claim 1 , wherein the inner surface 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 surface, and wherein the radius of the inner surface is between 5 mm and 200 mm.

9. The system of claim 1, wherein the upper window further comprises a second face opposite the first face and a body extending between the first face and the second face, the second face having a concave curvature.

10. The system of claim 1, wherein the upper window further comprises a rim circumscribing the first face and configured to couple to the processing chamber, wherein the outer surface extends a first height between the rim and the inner surface, wherein the inner surface extends a second height between the outer surface and a radial center of the upper window, wherein the first height is greater than the second height.

11. The system of claim 1, wherein the upper window comprises a transparent body including the inner surface and the outer surface.

12. A chemical vapor deposition system comprising: a chamber wall at least partially defining the processing chamber; a substrate support positioned within the processing chamber, the substrate support configured to receive a substrate thereon; and A window including: a frame for attaching the window to the chamber wall; and a transparent body connected to the frame, the body extending between a first face and an opposed second face, the first face facing the substrate support when the frame is attached to the chamber wall to define an air gap therebetween, the first face comprising a radially outer surface and a radially inner surface circumscribed within the outer surface, the outer surface extending radially from the frame to the inner surface and the inner surface extending radially inwardly from the outer surface to a radial center of the window, 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, wherein each of the outer surface and the inner surface is convex, and wherein a portion of the air gap defined by the outer surface and the substrate support is larger than a portion of the air gap defined by the inner surface and the substrate support.

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

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 between 100:1 and 1.1:

1.

15. The chemical vapor deposition system of claim 12, wherein the outer surface extends from the frame to the inner surface at the first radius of curvature, and the inner surface extends from the outer surface to a radial center of the window at the second radius of curvature.

16. The chemical vapor deposition system of claim 12, wherein the inner surface 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 surface, and wherein the radius of the inner surface is between 5 mm and 200 mm.

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

18. A method of depositing a layer on a substrate, the method comprising: providing a substrate on a substrate support within a processing chamber, the processing chamber comprising a gas inlet and a gas outlet; providing an upper window in the processing chamber, the upper window being transparent to enable radiant heating light to pass through the upper window, the upper window having a first face spaced from the substrate to define an air gap therebetween, the first face comprising a radially outer surface and a radially inner surface circumscribing the outer surface, 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, wherein each of the outer surface and the inner surface is convex, and wherein a portion of the air gap defined by the outer surface and the substrate is larger than a portion of the air gap defined by the inner surface and the substrate; and An air flow is directed through the air inlet, into the air gap between the first face and the substrate, and to the air outlet.

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

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