Coating processes – Coating by vapor – gas – or smoke
Reexamination Certificate
2001-03-06
2003-02-04
Meeks, Timothy (Department: 1762)
Coating processes
Coating by vapor, gas, or smoke
C427S255280
Reexamination Certificate
active
06514564
ABSTRACT:
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT
Not applicable.
BACKGROUND OF THE INVENTION
The present invention relates to an apparatus and method for dynamically blending two or more fluids to form a blended gaseous mixture which is delivered via a distribution header to one or more tools for chemical vapor deposition, including epitaxial film growth or similar layer deposition processes. Although the invention may have other applications, it is particularly applicable in semiconductor fabrication.
Semiconductor manufacturers often use a deposition gas mixture of trichlorosilane (SiHCl
3
) (TCS) and hydrogen (H
2
) for growth of thin films (e.g., epitaxial silicon) on silicon wafers. Such a mixture is usually obtained by sparging or bubbling H
2
gas into TCS liquid held at a specified temperature in a bubbler apparatus. This apparatus delivers a H
2
gas carrier stream saturated with TCS into a process tool used in semiconductor fabrication. However, since the stream must be saturated to ensure a consistent composition into the process tool, the bubbler must be located at close proximity to the process tool to avoid condensation in the customer's supply line (because condensation would affect the stream composition). Consequently, each tool typically has its own bubbler, which significantly increases capital expenditures required to handle TCS and reduces the available floor space in semiconductor fabrication facilities.
It is desired to have a delivery system and method which provide consistent composition of a blended gaseous mixture at a non-saturated condition (i.e., lower TCS dewpoint).
It is further desired to have a distribution header from which the blended gaseous mixture could be delivered to multiple tools, which would reduce floor space requirements and save capital.
It is still further desired to have the ability to provide a blended gaseous mixture to a variable number of process tools while maintaining consistent stream composition.
It is still further desired to have the ability to quickly manipulate the stream composition when end user requirements fluctuate.
BRIEF SUMMARY OF THE INVENTION
The present invention is a dynamic blending gas delivery system and method. The present invention also includes a blended gaseous mixture produced in accordance with the dynamic blending method. The blended gaseous mixture is used in chemical vapor deposition tools or other similar process tools, such as tools used in epitaxial film growth.
A first embodiment of the invention is a method for processing a plurality of fluids to form a blended gaseous mixture and supplying the blended gaseous mixture to a distribution header from which the blended gaseous mixture is delivered to at least one chemical vapor deposition tool or similar process tool. The method comprises seven steps. The first step is to supply a first fluid. The second step is to heat the first fluid to a temperature where at least some portion of the first fluid is a vapor. The third step is to superheat the vapor portion of the first fluid to a temperature sufficient to avoid condensation of the blended gaseous mixture delivered to the at least one chemical vapor deposition tool or similar process tool. The fourth step is to supply a second fluid. The fifth step is to heat the second fluid to a temperature sufficient to avoid condensation of the superheated vapor portion of the first fluid when the superheated vapor portion comes in contact with the second fluid. The sixth step is to combine the heated second fluid and the superheated vapor portion of the first fluid to form a blended gaseous mixture having desired physical and chemical properties for chemical vapor deposition, epitaxial film growth, or a similar process. The final step is to deliver the blended gaseous mixture to the distribution header from which the blended gaseous mixture is delivered to the at least one chemical vapor deposition tool or similar process tool.
In the described apparatus and process, the first fluid is trichlorosilane (SiHCl
3
) (TCS) and the second fluid is hydrogen (H
2
). However, the invention may be used to dynamically blend and deliver other vapor deposition fluids. For example, it may be used with other first fluids, including but limited to, silicon tetrachloride (SiCl
4
), dichlorosilane (SiH
2
Cl
2
), tetraethylorthosilicate (TEOS), phosphorus oxychloride (POCl
3
), trimethylsilane (SiH(CH
3
)
3
), boron trichloride (BCl
3
), and tungsten hexafluoride (WF
6
). Other possible second fluids include, but are not limited to, helium, nitrogen, argon, and oxygen.
A second embodiment of the invention is a method which includes the additional step of automatically maintaining a desired flow ratio between the first and second fluids so as to maintain the desired physical and chemical properties of the blended gaseous mixture. In one variation of this embodiment, the step of automatically maintaining a desired flow ratio between the first and second fluids comprises the following sub-steps: (a) measuring a flow rate of the first fluid; (b) measuring a flow rate of the second fluid; (c) measuring a change in pressure inside the distribution header; and (d) adjusting the flow rates of the first and second fluids at the desired flow ratio proportionally in an inverse relation to a measured change in pressure inside the distribution header.
A third embodiment includes three steps in addition to the steps in the first embodiment discussed above. The first additional step is to supply a third fluid which does not react with the first or second fluids or with the blended gaseous mixture. The next additional step is to heat the third fluid to a temperature sufficient to avoid condensation of the blended gaseous mixture delivered to the at least one chemical vapor deposition tool or similar process tool. The final additional step is to combine an amount of the heated third fluid in the gaseous phase with the blended gaseous mixture whereby a desired molar ratio of the first and second fluids is maintained so as to maintain the desired physical and chemical properties of the blended gaseous mixture and whereby condensation of the blended gaseous mixture is avoided in the distribution header. In one variation of this embodiment, the third fluid is an inert gas.
A fourth embodiment has one step in addition to the steps in the third embodiment. The additional step is to automatically maintain a desired flow ratio between the first and second fluids so as to maintain the desired physical and chemical properties of the blended gaseous mixture.
A fifth embodiment has two steps in addition to the steps in the first embodiment. The first additional step is to provide a storage buffer upstream of the distribution header. The second additional step is to deliver the blended gaseous mixture to the storage buffer prior to delivering the blended gaseous mixture to the distribution header.
A sixth embodiment is a dynamic blending gas delivery system for supplying a blended gaseous mixture to a distribution header from which the blended gaseous mixture is delivered to at least one chemical vapor deposition tool or similar process tool. The system includes: (1) means for supplying a first fluid; (2) means for heating the first fluid to a temperature where at least some portion of the first fluid is a vapor; (3) means for superheating the vapor portion of the first fluid to a temperature sufficient to avoid condensation of the blended gaseous mixture delivered to the at least one chemical vapor deposition tool or similar process tool; (4) means for supplying a second fluid; (5) means for heating the second fluid to a temperature sufficient to avoid condensation of the superheated vapor portion of the first fluid when the superheated vapor portion comes in contact with the second fluid; (6) means for combining the heated second fluid and the superheated vapor portion of the first fluid to form a blended gaseous mixture having desired physical and chemical properties for chemical vapor deposition, epitaxial film growth, or a sim
Botelho Alexandre de Almeida
Del Prato Thomas Anthony
Ford Robert William
Air Products and Chemicals Inc.
Chase Geoffrey L.
Meeks Timothy
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