Coating apparatus – Gas or vapor deposition – Crucible or evaporator structure
Reexamination Certificate
2000-07-21
2001-10-09
Bueker, Richard (Department: 1763)
Coating apparatus
Gas or vapor deposition
Crucible or evaporator structure
C118S715000, C392S397000
Reexamination Certificate
active
06299692
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to a head for vaporizing solid and/or liquid PRECURSOR compounds and for injecting them as vapor into a processing chamber during chemical vapor deposition onto surfaces of a semiconductor to deposit thin films of materials such as tantalum, tantalum nitride, titanium, etc.
BACKGROUND OF THE INVENTION
The growth in the use, and usefulness, of semiconductors has been accompanied by the development of new processes and materials for the design and manufacture of semiconductors together with new or improved manufacturing equipment and hardware. Important recent improvements in design and new materials have led to faster speeds of operation and greater densities for very large scale integrated (VLSI) circuits. The use of new materials such as tantalum, titanium, and other metals, has led to the need for more efficient ways of applying them to semiconductor surfaces.
A layer or film of a metal such as tantalum, titanium, etc. can be deposited by chemical vapor deposition (CVD) onto exposed surfaces of a semiconductor wafer during processing into VLSIs. For example, a precursor compound of the metal tantalum, namely pentadiethylaminotantalum (PDEAT), can be vaporized under certain conditions of pressure and temperature to obtain a gaseous or vapor phase of the compound which may then be used in CVD processing to form a layer of metal. Precursor compounds of various metals require low pressures (e.g., a Torr or less and elevated temperatures (e.g., roughly 100° C.) to change them into and hold them in vapor phase. This will be explained in greater detail hereinafter.
It is desirable that a layer of metal being deposited by CVD on a semiconductor wafer be uniform in thickness. To achieve this, a chemical vapor precursor compound of the metal flowing into a processing chamber where the semiconductor wafer is being processed should be controlled in flow direction and amplitude so that the vapor is evenly distributed and flows uniformly toward the wafer. In addition, because a CVD process step using a precursor compound of a metal such as tantalum, titanium, etc., is typically carried out in a chamber maintained under low pressure conditions (e.g., a Torr or less), the flow of gas vapor into the chamber through a vaporizer head should be impeded as little as possible by the head. The head should have high-flow-conductance so that pressure drop across it is low (e.g., a fraction of a Torr). The gas vapor should also be controlled in temperature as it passes through the head and enters the chamber to prevent condensation of the vapor into droplets or particles.
The present invention provides a simple and efficient vaporizer head with improved characteristics which fills these needs.
SUMMARY OF THE INVENTION
In accordance with the invention in one specific embodiment thereof, there is provided a vaporizer head for low pressure application of vapors of precursor compounds useful in chemical vapor deposition of materials such as titanium, tantalum, etc., onto the surfaces of semiconductors. The vaporizer head comprises a body having a center axis, an outer diameter, an outer surface, an input end, an output end, and a length between the ends. The body defines a cavity along the center axis from the input end to near but not through the output end for receiving a stream of vaporized precursor compound, the cavity having a closed well-like end for containing droplets or particles of condensed precursor compound which may occur. The body also defines a plurality of passages through the head for flow of vapor outward from the cavity through the outer surface, each passage having a length and a diameter and extending radially from the center axis at respective angles relative to the center axis. The plurality of passages have sufficiently large diameters to cause only low pressure drop to vapor flowing through them and to provide dispersion of vapor flowing through the head such that vapor flows evenly onto a semiconductor surface, the head providing a desired operating temperature for the vapor flowing through it.
In one specific embodiment the invention is a vaporizer head for applying vapors of precursor compounds useful in chemical vapor deposition of layers of materials onto semiconductors. The head comprises a body having a center axis, an outer diameter, an outer surface, an input end, an output end, and a length between the ends. The body defines a cavity along the center axis from the input end to near but not through the output end for receiving a stream of vaporized precursor compound. The cavity has a closed well-like bottom for containing droplets or particles of condensed precursor compound which may occur. The body defines a plurality of passages through the head for flow of vapor outward from the cavity through the outer surface. Each passage has a length and a diameter and extending radially from the center axis at respective angles relative to the center axis. The plurality of passages have sufficiently large diameters to cause only a pressure drop of less than about a Torr to vapor flowing through them and to provide dispersion of vapor flowing through the head such that vapor flows evenly onto a semiconductor surface. The head provides a desired operating temperature for the vapor flowing through it.
In an other specific embodiment the invention is a vaporizer head for flowing into a processing chamber vaporized precursor compounds during chemical vapor deposition of metal and other layers onto a semiconductor. The head comprises a body having a center axis, an inwardly tapered lower outer surface, an input end, an output end, and a length between the ends. The body defines a cavity along the center axis and having an opening in the input end for receiving a stream of vaporized precursor compound. The cavity has a closed well-like bottom near the output end for containing droplets and particles of the precursor compound and preventing them from leaving the head except as vapor. The body defines a first plurality of passages for flow of vapor, each passage having a length and a diameter and extending radially from the cavity like the spokes of a wheel at a first inclined angle relative to the center axis from the cavity to the lower outer surface. The body defines a second plurality of passages for flow of vapor, each passage having a length and a diameter and extending radially from the cavity like the spokes of a wheel at a second inclined angle relative to the center axis from the cavity to the lower outer surface. The body defines a third plurality of passages each having a length and a diameter and extending from just above the well-like bottom of the cavity to the output end of the body, the pluralities of passages having sufficiently large diameters to result during operation thereof of only a fraction of a Torr pressure drop to a flow of vapor flowing therethrough.
In still an other specific embodiment the invention is an apparatus for chemical vapor deposition onto semiconductor wafers. The apparatus comprises a processing chamber which can be maintained at sub-atmospheric pressure, a platform or susceptor within the chamber for holding a wafer during processing, and a vaporizer head for flowing into the chamber and onto a wafer vaporized precursor compounds for chemical vapor deposition of metal and other films onto the wafer. The head comprises a body having a center axis, an outer surface, input end, and output end, and a length between the ends. The body defines a cavity extending along the center axis with an opening in the input end for receiving a stream of vaporized material. The cavity has a closed well-like bottom end near the output end of the body for collecting droplets and particles of precursor compound and preventing them from leaving the head except as vapor. The body defines a plurality of passages through the head for flow of vaporized material. Each passage having a length and a diameter and extending radially like spokes of a wheel from along and around the cavity at an inclined angle relative to the ce
Chang Anzhong
Ku Vincent
Nguyen Anh N.
Xi Ming
Yuan Xiaoxiong
Applied Materials Inc.
Bueker Richard
Ostroff & Associates
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