Patent Description:
The field relates generally to apparatus and methods for wafer processing, and more particularly to apparatus and methods for semiconductor wafer etching or semiconductor wafer chemical vapor deposition processes.

Epitaxial chemical vapor deposition (CVD) is a process for growing a thin layer of material on a semiconductor wafer so that the lattice structure is identical to that of the wafer. Epitaxial CVD is widely used in semiconductor wafer production to build up epitaxial layers such that devices can be fabricated directly on the epitaxial layer. The epitaxial deposition process begins by introducing a cleaning gas, such as hydrogen or a hydrogen and hydrogen chloride mixture, to a front surface of the wafer (i.e., a surface facing away from the susceptor) to pre-heat and clean the front surface of the wafer. The cleaning gas removes native oxide from the front surface, permitting the epitaxial silicon layer to grow continuously and evenly on the surface during a subsequent step of the deposition process. The epitaxial deposition process continues by introducing a vaporous silicon source gas, such as silane or a chlorinated silane, to the front surface of the wafer to deposit and grow an epitaxial layer of silicon on the front surface. A back surface opposite the front surface of the susceptor may be simultaneously subjected to hydrogen gas. The susceptor, which supports the semiconductor wafer in the deposition chamber during the epitaxial deposition, is rotated during the process to allow the epitaxial layer to grow evenly.

However, epitaxial CVD growth rates are generally not uniform across the surface of each wafer because of a non-uniform temperature profile of the semiconductor wafer. A lack of uniformity causes degradation in the flatness of the wafer and may be a result of variability or local temperature deviations within the semiconductor wafer caused by non-uniform heating of the semiconductor wafer by high intensity lamps. Accordingly, there exists a need for a practical, cost-effective apparatus to improve local temperature deviations to improve uniformity of epitaxial CVD growth rates.

<CIT> discloses a susceptor support shaft for a process chamber, comprising a cylindrical support shaft and a support body coupled to the support shaft, the support body comprising a solid disc, and a refractive element placed on the top of the solid disc to redistribute secondary heat distributions across the susceptor and/or substrate for thickness uniformity of an epitaxy process.

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.

In one aspect, a reaction apparatus for contacting a process gas on a semiconductor wafer during a watering process is provided. The semiconductor wafer defines a center region. The reaction apparatus includes an upper dome, a lower dome, a shaft, and a cap. The lower dome is attached to the upper dome, and the upper dome and the lower dome define a reaction chamber. The shaft supports the semiconductor wafer within the reaction chamber. The cap is positioned on the shaft within the reaction chamber for reducing heat absorbed by the center region of the semiconductor wafer. The cap is attached to a first end of the shaft. The cap includes a tube and a disc. The tube defines a tube diameter larger than a shaft diameter of the shaft. The tube circumscribes the first end of the shaft. The disc is attached to the tube and is positioned to block radiant heat from heating the center region of the semiconductor wafer. The disc is generally opaque to absorb radiant heating light produced by high intensity lamps.

In another aspect, a method of manufacturing a semiconductor wafer in a reaction apparatus is provided. The reaction apparatus includes an upper dome and a lower dome defining a reaction chamber and a shaft for supporting the semiconductor wafer. The reaction apparatus further includes a cap positioned on the shaft within the reaction chamber for reducing heat absorbed by a center region of the semiconductor wafer. The cap includes a tube and a disc attached to the tube. The method includes channeling a process gas into the reaction chamber. The method also includes heating the semiconductor wafer with a high intensity lamp positioned within the reaction chamber. The method further includes blocking radiant heat from the high intensity lamp from heating the center region of the semiconductor wafer with the disc. The disc generates a uniform temperature distribution on the semiconductor wafer. The disc is generally opaque to absorb radiant heating light produced by the high intensity lamp. The method also includes depositing a layer on the semiconductor wafer with the process gas. The uniform temperature distribution forms a uniform thickness of the layer on the semiconductor wafer.

Various refinements exist of the features noted in relation to the above-mentioned aspects of the present disclosure. Further features may also be incorporated in the above-mentioned aspects of the present disclosure 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 of the present disclosure may be incorporated into any of the above-described aspects of the present disclosure, alone or in any combination.

Referring now to <FIG>, an apparatus for etching a semiconductor wafer or for depositing an epitaxial layer on a semiconductor substrate in accordance with an embodiment of the present disclosure is generally referred to as <NUM>. The illustrated apparatus is a single wafer reactor; however, the apparatus and methods disclosed herein for providing a more uniform epitaxial layer are suitable for use in other reactor designs including, for example, multiple wafer reactors. The apparatus <NUM> includes a reaction chamber <NUM> comprising an upper dome <NUM>, a lower dome <NUM>, an upper liner <NUM>, and a lower liner <NUM>. Collectively, the upper dome <NUM>, lower dome <NUM>, upper liner <NUM>, and lower liner <NUM> define an interior space <NUM> of the reaction chamber <NUM> in which process gas contacts a semiconductor wafer <NUM>. A gas manifold <NUM> is used to direct process gas into the reaction chamber <NUM>. A perspective view of the reaction chamber <NUM> and gas manifold <NUM> is shown in <FIG>.

The apparatus <NUM> may be used to process a wafer in a wafering process, including without limitation, depositing any type of material on a wafer performed by a chemical vapor deposition (CVD) process, such as epitaxial CVD or polycrystalline CVD. In this regard, reference herein to epitaxy and/or CVD processes should not be considered limiting as the apparatus <NUM> may also be used for other purposes such as to perform etching or smoothing processes on the wafer. Also, the wafer shown herein is generally circular in shape, though wafers of other shapes are contemplated within the scope of this disclosure.

A cross section of the apparatus <NUM> is shown in <FIG>. Within the interior space <NUM> of the reaction chamber <NUM> is a preheat ring <NUM> for heating the process gas prior to contact with a semiconductor wafer <NUM>. The outside circumference of the preheat ring <NUM> is attached to the inner circumference of the lower liner <NUM>. For example, the preheat ring <NUM> may be supported by an annular ledge (not shown) of the lower liner <NUM>. A susceptor <NUM> (which may also be referred to herein as a "susceptor body") traversing the space interior to the preheat ring <NUM> supports the semiconductor wafer <NUM>.

Process gas may be heated prior to contacting the semiconductor wafer <NUM>. Both the preheat ring <NUM> and the susceptor <NUM> are generally opaque to absorb radiant heating light produced by high intensity lamps <NUM>, <NUM> that may be located above and below the reaction chamber <NUM> for heating the semiconductor wafer <NUM>. 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 process gas as the process gas passes over the preheat ring and the susceptor. Typically, the diameter of the semiconductor wafer <NUM> is less than the diameter of the susceptor <NUM> to allow the susceptor to heat the process gas before it contacts the wafer.

The preheat ring <NUM> and susceptor <NUM> may suitably be constructed of opaque graphite coated with silicon carbide, though other materials are contemplated. The upper dome <NUM> and lower dome <NUM> are typically made of a transparent material to allow radiant heating light to pass into the reaction chamber <NUM> and onto the preheat ring <NUM> and the susceptor <NUM>. The upper dome <NUM> and lower dome <NUM> may be constructed of transparent quartz. Quartz is generally transparent to infrared and visible light and is chemically stable under the reaction conditions of the deposition reaction. Equipment other than high intensity lamps <NUM>, <NUM> may be used to provide heat to the reaction chamber such as, for example, resistance heaters and inductive heaters. An infrared temperature sensor (not shown) such as a pyrometer may be mounted on the reaction chamber <NUM> to monitor the temperature of the susceptor <NUM>, preheat ring <NUM>, or semiconductor wafer <NUM> by receiving infrared radiation emitted by the susceptor, preheat ring, or wafer.

Referring now to <FIG>, wherein some components of the apparatus <NUM> are removed to better illustrate the apparatus, the apparatus <NUM> includes a shaft <NUM> that may support the susceptor <NUM>. The shaft <NUM> extends through a central column <NUM>. The shaft <NUM> includes a first end <NUM> attached to the central column <NUM> and a second end <NUM> positioned proximate a center region <NUM> of the semiconductor wafer <NUM>. The shaft <NUM> has a shaft diameter <NUM> of about <NUM> millimeters (mm) to about <NUM>.

The shaft <NUM> is connected to a suitable rotation mechanism (not shown) for rotation of the shaft <NUM>, susceptor <NUM>, and semiconductor wafer <NUM> about a longitudinal axis X with respect to the apparatus <NUM>. The outside edge of the susceptor <NUM> and inside edge of the preheat ring <NUM> (shown in <FIG>) are separated by a gap <NUM> to allow rotation of the susceptor. The semiconductor wafer <NUM> is rotated to prevent an excess of material from being deposited on the wafer leading edge and provide a more uniform epitaxial layer.

The apparatus <NUM> also includes a cap <NUM> positioned on the shaft <NUM> within the reaction chamber <NUM> for reducing heat absorbed by the center region <NUM> of the semiconductor wafer <NUM>. The cap <NUM> is attached to the first end <NUM> of the shaft <NUM> proximate the center region <NUM> of the semiconductor wafer <NUM> to block radiant heat from the lower high intensity lamp <NUM> from heating the center region of the semiconductor wafer. Reducing radiant heat to the center region <NUM> of the semiconductor wafer <NUM> reduces a temperature of the center region while maintaining a temperature of outer radial regions <NUM> of the semiconductor wafer <NUM>, generating a uniform temperature profile of the semiconductor wafer.

The cap <NUM> includes a tube <NUM> and a disc <NUM> attached to the tube. In the illustrated embodiment, the tube <NUM> and the disc <NUM> are integrally formed together such that the cap <NUM> has a unitary construction. In alternative embodiments, the tube <NUM> and the disc <NUM> may be formed separately and attached to each other. The tube <NUM> includes a cylindrical wall <NUM> having a first end <NUM>, a second end <NUM>, and a tube length <NUM> and defining a tube conduit <NUM> and a tube diameter <NUM>. The first end <NUM> defines a first end opening <NUM>, and the second end <NUM> defines a second end opening <NUM>. The tube diameter <NUM> is larger than the shaft diameter <NUM> such that the first end <NUM> of the shaft <NUM> is inserted into the first end opening <NUM> and the first end <NUM> circumscribes the first end of the shaft. The second end <NUM> is attached to the disc <NUM>.

The disc <NUM> includes an annular disc <NUM> defining a disc hole <NUM>, an inner diameter <NUM>, an outer diameter <NUM>, and a disc thickness <NUM>. The tube diameter <NUM> and the inner diameter <NUM> are the same, or substantially equal, such that the cylindrical wall <NUM> is substantially flush with the disc hole <NUM> and the tube conduit <NUM> and the disc hole define a cap conduit <NUM> extending through the cap <NUM>. In alternative embodiments, the tube diameter <NUM> is larger than the inner diameter <NUM>, and the tube conduit <NUM> and the disc hole <NUM> define the cap conduit <NUM>.

The annular disc <NUM> has a first side <NUM> and a second side <NUM>, and the first side of the annular disc is attached to the second end <NUM> of the tube <NUM>. The first side <NUM> of the annular disc <NUM> is oriented toward the lower high intensity lamp <NUM>, and the second side <NUM> is oriented toward the center region <NUM> of the semiconductor wafer <NUM>. The annular disc <NUM> may be attached to the tube <NUM> in any suitable manner. Additionally, the annular disc <NUM> may have other shapes, one or more recesses formed therein, and/or several openings formed therein.

The outer diameter <NUM> is larger than the tube diameter <NUM> and the inner diameter <NUM> such that the annular disc <NUM> blocks radiant heat from the lower high intensity lamp <NUM> from heating the center region of the semiconductor wafer. The annular disc <NUM> extends from the disc hole <NUM> and the cylindrical wall <NUM> such that the annular disc extends a blocking distance <NUM> from the cylindrical wall and the disc hole. The blocking distance <NUM> is configured to block a predetermined amount of radiant heat to generate the uniform temperature profile of the semiconductor wafer <NUM>.

The cap <NUM> is made of an opaque material to block visible and infrared light from being transmitted to the center region <NUM> of the semiconductor wafer <NUM>.

Generally, the cap <NUM> corrects and/or affects the radial temperature profile of the semiconductor wafer <NUM> during processing, such as epitaxial deposition to alleviate non-uniformities. The cap <NUM> may cause the temperature of the center region <NUM> of the semiconductor wafer <NUM> above the cap to decrease (relative to when a cap is not used) thereby decreasing the amount of material (e.g., silicon) that deposits in the center region of the semiconductor wafer during epitaxial CVD processes. Accordingly, the cap <NUM> is suitably positioned a distance below the center region <NUM> of the semiconductor wafer <NUM> in which a localized or global maximum layer thickness occurs to decrease the deposition at the central region and create a more uniform radial deposition profile. Note that this maximum layer thickness may be a local or global maximum, and may generally be referred to as a non-uniformity.

The thickness profile may be determined by use of any suitable method available to those of skill in the art including, for example, use of a Fourier-Transform Infrared (FTIR) spectrometer or use of a wafer flatness tool (e.g., KLA-Tencor Wafersight or WaferSight2; Milpitas, California). In some embodiments, the radial thickness profile of the substrate is determined before material deposition (e.g., before deposition of an epitaxial layer) and the thickness profile of the layered structure may then be measured. The thickness profile of the deposited layer may be determined by subtracting the substrate thickness from the layered structure thickness.

Specifically, in the illustrated embodiment, the tube length <NUM> is about <NUM> to about <NUM>; the tube diameter <NUM> is about <NUM> to about <NUM>; the inner diameter <NUM> is about <NUM> to about <NUM>; the outer diameter <NUM> is about <NUM> to about <NUM>; the disc thickness <NUM> is about <NUM> to about <NUM>; and the blocking distance <NUM> is about <NUM> to about <NUM>. In alternative embodiments, the shaft diameter <NUM>, the tube length <NUM>, the tube diameter <NUM>, the inner diameter <NUM>, the outer diameter <NUM>, the disc thickness <NUM>, and the blocking distance <NUM> may be any distance that enables the cap <NUM> to operate as described herein. More specifically, the shaft diameter <NUM>, the tube length <NUM>, the tube diameter <NUM>, the inner diameter <NUM>, the outer diameter <NUM>, the disc thickness <NUM>, and the blocking distance <NUM> are suitably chosen depending on a location and size of a local or global epitaxial layer thickness minimum or maximum.

A distance <NUM> between the cap <NUM> and the susceptor <NUM> that is less than about <NUM>, less than about <NUM>, or even less than about <NUM>. Decreasing the distance <NUM> between the cap <NUM> and the susceptor <NUM> generally results in deposition of more material on the wafer in portions of the wafer above the ring and increasing the distance generally results in less deposition. Therefore, the amount of material deposited on portions of the wafer above the cap <NUM> may be adjusted by varying this distance.

The ranges recited above for the shaft diameter <NUM>, the tube length <NUM>, the tube diameter <NUM>, the inner diameter <NUM>, the outer diameter <NUM>, the disc thickness <NUM>, the blocking distance <NUM>, the distance <NUM>, and the like are exemplary and values outside of the stated ranges may be used without limitation. As shown in <FIG>, the disc <NUM> has a substantially uniform circular shape. In other embodiments, the disc <NUM> may be shaped to include various projections and/or notches or recesses. The disc <NUM> may also be beveled or rounded. Such non-uniform shapes may enable the disc <NUM> to block radiant heat from the lower high intensity lamp <NUM> from heating regions out the center region <NUM> of the semiconductor wafer <NUM>. For example, analysis of the temperature profile of the semiconductor wafer <NUM> may identify regions outside of the center region <NUM> that have elevated temperatures such that the deposition of material in those areas is non-uniform. The shape of the disc <NUM> may be adjusted to block radiant heat from the lower high intensity lamp <NUM> from heating those regions to decrease material deposition within those regions.

<FIG> is a flow diagram of a method <NUM> of manufacturing a semiconductor wafer in a reaction apparatus. The method <NUM> includes channeling <NUM> a process gas into the reaction chamber. The method <NUM> also includes heating <NUM> the semiconductor wafer with a high intensity lamp positioned within the reaction chamber. The method <NUM> further includes blocking <NUM> radiant heat from the high intensity lamp from heating the center region of the semiconductor wafer with the disc. The disc generates a uniform temperature distribution on the semiconductor wafer. The method <NUM> also includes depositing <NUM> a layer on the semiconductor wafer with the process gas. The uniform temperature distribution forms a uniform thickness of the layer on the semiconductor wafer.

The processes of the present disclosure are further illustrated by the following Example. This Example should not be viewed in a limiting sense.

An opaque cap as described herein was tested in a single wafer epitaxy reactor to determine their effect on the epitaxial wafer temperature profile. The epitaxial wafers were prepared by exposing single crystal silicon wafer produced by the Czochralski method to a process gas at a wafer temperature between <NUM> to <NUM>. The disc of the cap had an outer diameter of <NUM>.

A control run was performed in which a cap was not used. <FIG> is a graph <NUM> of epitaxial wafer radial temperature as a function of wafer radial distance. As can be seen from <FIG>, the control resulted in a non-uniform epitaxial wafer radial temperature profile <NUM>, and the cap resulted in a uniform epitaxial wafer radial temperature profile <NUM>. The uniform epitaxial wafer radial temperature profile <NUM> is more uniform because the local temperature maximums at the ends of the profile are less than the local temperature maximums at the ends of the non-uniform epitaxial wafer radial temperature profile <NUM>. Accordingly, the cap generated a uniform temperature profile of the epitaxial wafer.

Compared to conventional methods for producing silicon wafers, the systems and methods of the present disclosure have several advantages. For example, reactors that include caps as described facilitate cost-effective manufacture of semiconductor wafers with a uniform temperature profile during deposition. The uniform temperature profile generates a more uniform deposition thickness profile. Thus, the caps enable production of a semiconductor wafer with a uniform thickness profile. An example cap has a disc in or around a center region of the wafer and blocks radiant heat from heating the center region of the wafer. The temperature of the center region is thereby reduced, generating a uniform temperature profile and a uniform thickness profile. Accordingly, the example caps eliminate or reduce local temperature deviations, as compared to the prior art, to improve the uniformity of epitaxial CVD growth on a wafer. Additionally, use of the above examples can improve the production rate of the epitaxial CVD system, and can lower operational costs by reducing waste.

Claim 1:
A reaction apparatus for contacting a process gas on a semiconductor wafer during a watering process, the semiconductor wafer defining a center region, the reaction apparatus comprising:
an upper dome;
a lower dome attached to the upper dome, the upper dome and the lower dome defining a reaction chamber;
a shaft for supporting the semiconductor wafer within the reaction chamber; and
a cap positioned on the shaft within the reaction chamber for reducing heat absorbed by the center region of the semiconductor wafer, the cap attached to a first end of the shaft, the cap comprising:
a tube defining a tube diameter larger than a shaft diameter of the shaft, wherein the tube circumscribes the first end of the shaft; and
a disc attached to the tube, wherein the disc is positioned to block radiant heat from heating the center region of the semiconductor wafer, and wherein the disc is generally opaque to absorb radiant heating light produced by high intensity lamps.