Semiconductor device manufacturing: process – Introduction of conductivity modifying dopant into... – Plasma
Reexamination Certificate
1998-12-01
2001-10-09
Dang, Thi (Department: 1763)
Semiconductor device manufacturing: process
Introduction of conductivity modifying dopant into...
Plasma
C438S515000, C118S7230IR
Reexamination Certificate
active
06300227
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to the manufacture of objects. More particularly, the present invention provides a technique for providing a combination of a plasma discharge and an applied magnetic field for creating a high density plasma source. The present invention can be applied to implanting particles for the manufacture of integrated circuits, for example. But it will be recognized that the invention has a wider range of applicability; it can also be applied to implanting particles for other substrates such as multi-layered integrated circuit devices, three-dimensional packaging of integrated semiconductor devices, photonic devices, piezoelectronic devices, microelectromechanical systems (“MEMS”), sensors, actuators, solar cells, flat panel displays (e.g., LCD, AMLCD), doping semiconductor devices, biological and biomedical devices, and the like.
Integrated circuits are fabricated on chips of semiconductor material. These integrated circuits often contain thousands, or even millions, of transistors and other devices. In particular, it is desirable to put as many transistors as possible within a given area of semiconductor because more transistors typically provide greater functionality, and a smaller chip means more chips per wafer and lower costs. Some integrated circuits are fabricated on a slice or wafer, of single-crystal (monocrystalline) silicon, commonly termed a “bulk” silicon wafer. Devices on such “bulk” silicon wafer typically are made by processing techniques such as ion implantation or the like to introduce impurities or ions into the substrate. These impurities or ions are introduced into the substrate to selectively change the electrical characteristics of the substrate, and therefore devices being formed on the substrate. Ion implantation provides accurate placement of impurities or ions into the substrate. Ion implantation, however, is expensive and generally cannot be used effectively for introducing impurities into a larger substrate such as glass or a semiconductor substrate, which is used for the manufacture of flat panel displays or the like.
Accordingly, plasma treatment of large area substrates such as glass or semiconductor substrates has been proposed or used in the fabrication of flat panel displays or 300 millimeter silicon wafers. Plasma treatment is commonly called plasma immersion ion implantation (“PIII”) or plasma source ion implantation (“PSI”). Plasma treatment generally uses a chamber, which has an inductively coupled plasma source, for generating and maintaining a plasma therein. A large voltage differential between the plasma and the substrate to be implanted accelerates impurities or ions from the plasma into the surface or depth of the substrate. A variety of limitations exist with the convention plasma processing techniques.
A major limitation with conventional plasma processing techniques is the maintenance of the uniformity of the plasma density and chemistry over such a large area is often difficult. As merely an example, inductively or transformer coupled plasma sources (“ICP” and “TCP,” respectively) are affected both by difficulties of maintaining plasma uniformity using inductive coil antenna designs. Additionally, these sources are often costly and generally difficult to maintain, in part, because such sources which require large and thick quartz windows for coupling the antenna radiation into the processing chamber. The thick quartz windows often cause an increase in radio frequency (“rf”) power (or reduction in efficiency) due to heat dissipation within the window.
Other techniques such as Electron Cyclotron Resonance (“ECR”) and Helicon type sources are limited by the difficulty in scaling the resonant magnetic field to large areas when a single antenna or wave guide is used. Furthermore, most ECR sources utilize microwave power. Microwave power is often more expensive and difficult to tune electrically. Hot cathode plasma sources have been used or proposed. The hot cathode plasma sources often produce contamination of the plasma environment due to the evaporation of cathode material. Alternatively, cold cathode sources have also be used or proposed. These cold cathode sources often produce contamination due to exposure of the cold cathode to the plasma generated.
A pioneering technique has been developed to improve or, perhaps, even replace these conventional sources for implantation of impurities. This technique has been developed by Dr. Chung Chan of Waban Technology in Massachusetts, now Silicon Genesis Corporation, and has been described in U.S. Pat. No. 5,653,811 (“Chan”), which is hereby incorporated by reference herein for all purposes. Chan generally describes techniques for treating a substrate with a plasma with an improved plasma processing system. The improved plasma processing system, includes, among other elements, at least two rf sources, which are operative to generate a plasma in a vacuum chamber. By way of the multiple sources, the improved plasma system provides a more uniform plasma distribution during implantation, for example. It is still desirable, however, to provide even a more uniform plasma for the manufacture of substrates.
From the above, it is seen that an improved technique for introducing impurities into a substrate is highly desired.
SUMMARY OF THE INVENTION
According to the present invention, a technique including a method for providing a high density plasma source is provided. In an exemplary embodiment, the present invention provides a method that uses a combination of a high frequency source and a magnetic source to form a high density plasma. The high density plasma source can provide a plasma that is substantially a single isotope of hydrogen, for example.
In a specific embodiment, the present invention provides a novel method for forming a plasma. The method includes forming an rf plasma discharge in a vacuum chamber. The plasma discharge includes an inductive coupling structure, which has a first cusp region at a first end of the structure and a second cusp region at a second end of the structure. In some embodiments, a third cusp region, which is between the first and second cusp regions, can also be included. The first cusp region is provided by a first electro-magnetic source and the second cusp region is provided by a second-electro magnetic source. The first electro-magnetic source and the second electro-magnetic source confines a substantial portion of the rf plasma discharge to a region away from a wall of the vacuum chamber. Accordingly, a plasma discharge is substantially a single ionic species can be formed.
In an alternative embodiment, the present invention includes a novel method for implanting particles using a plasma source. The method includes forming an rf plasma discharge in a vacuum chamber. The plasma discharge includes an inductive coupling structure, which has a first cusp region at a first end of the structure and a second cusp region at a second end of the structure. In some embodiments, a third cusp region, which is between the first and second cusp regions, can also be included. The first cusp region is provided by a first electro-magnetic source and the second cusp region is provided by a second-electro magnetic source. The first electro-magnetic source and the second electro-magnetic source confine a substantial portion of the rf plasma discharge to a region away from a wall of the vacuum chamber. The method also includes biasing a substrate relative to the plasma discharge to introduced particles from the plasma into the substrate. By way of the plasma discharge, which can be substantially a single ionic species (e.g., H
1
+), a uniform distribution of implanted particles at a selected depth in the substrate is achieved.
Numerous benefits are achieved by way of the present invention. In one aspect, the present invention provides a high density plasma source that is rich with hydrogen bearing particles in the H
1
+ state. This high density source is an active which allows the hydrogen bearing particles to be impla
Bryan Michael A.
Liu Wei
Roth Ian S.
Dang Thi
Silicon Genesis Corporation
Townsend and Townsend / and Crew LLP
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