Collection devices for plasma immersion ion implantation

Details Collection devices for plasma immersion ion implantation Collection devices for plasma immersion ion implantation

1998-10-01

2001-08-07

Mills, Gregory (Department: 1763)

Coating apparatus

Gas or vapor deposition

With treating means

C118S7230MP

Reexamination Certificate

active

06269765

ABSTRACT:

BACKGROUND OF THE INVENTION
The present invention relates to the manufacture of integrated circuits. More particularly, the present invention provides a technique for selectively controlling a distribution of impurities that are implanted using a plasma immersion ion implantation or plasma ion source system for the manufacture of semiconductor integrated circuits, for example. But it will be recognized that the invention has a wider range of applicability; it can also be applied to other substrates for 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), 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 use 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 mm 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 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 waveguide is used. Furthermore, most ECR sources utilize microwave power which is 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 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. Additionally, Chan's techniques can create particulate contamination during implantation processes using his plasma processing system.
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 and system for introducing impurities into a substrate using plasma immersion ion implantation is provided. In an exemplary embodiment, the present invention provides a system with a novel susceptor with a collection device that improves implantation uniformity during an implantation process.
In a specific embodiment, the present invention provides a plasma treatment system for implantation with a novel susceptor with a collection device. The system has a variety of elements such as a chamber in which a plasma is generated in the chamber. The system also has a susceptor disposed in the chamber to support a substrate (e.g., silicon wafer), which has a surface. A collection device (e.g., Faraday cup) is disposed adjacent to the susceptor to accumulate stray ions or charge to create a more uniform electric field or linearize electric field lines, and to reduce a possibility of particles from defecting off of internal surfaces of the chamber. When the defected particles land on the substrate, they may create functional and/or reliability problems for a resulting semiconductor device. In a specific embodiment, the chamber has a plurality of substantially planar rf transparent windows (but do not need be planar) on a surface of the chamber. The system also has an rf generator and at least two rf sources in other embodiments.
In an alternative embodiment, the present invention provides a method for forming a substrate using a plasma immersion ion implantation system. The method includes a step of providing a substrate (e.g., silicon wafer), which has a surface, onto a susceptor within a plasma immersion ion implantation chamber. The method then introduces and/or accelerates particles (e.g., ions) in a uniform, directional manner toward and through the surface of the substrate to uniformly distribute the particles into a selected depth across a plane of the substrate. The method also introduces particles through a perforated shield that is disposed adjacent to the substrate. The perforated shield tends to adjust the electric field to uniformly distribute the particles across the substrate surface to provide the uniformly placed particles at the selected depth. The method collects a portion, if not all, of the particles that traverse through the perforated shield in one or a plurality of collector devices, e.g., Faraday cups.
In a further alternative embodiment, the present invention provides a method for measuring implantation uniformity. In a specific embodiment, the method is an in-situ measuring technique, but is not limited to such a technique. The method has a variety of steps such providing a substrate (e.g., silicon wafer), which

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