Radiant energy – Irradiation of objects or material – Irradiation of semiconductor devices
Reexamination Certificate
1999-10-27
2001-07-17
Berman, Jack (Department: 2881)
Radiant energy
Irradiation of objects or material
Irradiation of semiconductor devices
C250S306000, C205S136000, C205S123000, C065S386000, C065S425000
Reexamination Certificate
active
06262426
ABSTRACT:
TECHNICAL FIELD OF INVENTION
This invention is directed toward a technique for improving the imaging and fabrication of new and traditional types of integrated electrical devices, electro-optical devices, optical devices, and micro machines.
BACKGROUND OF INVENTION
Unbound atoms naturally attract or expel electrons forming ions. In general, metal atoms lose electrons most readily becoming positive ions, while nonmetals prefer to gain electrons becoming negative ions. Atoms joined together as molecules can also possess net positive or negative charges. These atoms are called dipoles. Atoms because they contain a positive nucleus and a negative electron cloud can become polarized in an electric field; the atoms in this state are also usually referred to as dipoles. In an electric field the atom can be thought of as possessing two superimposed positive and negative charged regions. Upon the application of the electric field the positive charge nucleus moves in the direction of the applied field and the negative charged electrons move in the opposite direction. If the electric field is strong enough, an electron may be stripped from the atom creating a positive ion, in which case the atom will migrate toward a negative charged electrode. Each element has a different ionization enthalpy, which is the energy required to remove an electron from one mole of gaseous atoms or ions.
Material sandwiched between a positive and negative charged plate can also become polarized. In this application the material between the plate is called a dielectric. Induced positive and negative surface charge densities form within the dielectric nearest to the plates, a positive region near the negative plate and a negative region near the positive plate. The distance between the plates is limited by the electric discharge that could occur through the dielectric medium. The maximum voltage that can be applied between the plates is dependent on the strength of the electric field or the dielectric strength of the dielectric. The dielectric by nature reduces the electric field potential between the charged plates or probes. If the field strength in the medium exceeds the dielectric strength the insulating properties break down and the medium begins to conduct. Every substance has its own unique dielectric strength. An electric field created between two oppositely charged very sharp tip probes, unlike the charged plates, is not uniform, but weakens along a radius perpendicular to a imaginary line connecting the centers of the probes tips. The maximum electric field potential lies at the tips of the probes. Therefore, the maximum surface charges created by the electric field are found on the dielectric underneath the probe tips.
The process of moving elements through a liquid medium from one charged inert electrode to a second oppositely charge inert electrode is called electrolysis. If the electrodes participate in the electrolysis process one electrode may dissolve and plate the other. This deposition of one electrode onto another is commonly called electroplating. The movement of ions in a solution can be used as a technique as shown by Dr. Jean-Claude Bradley in his published articles appearing in Nature (1997, vol. 389, p.268) and Advanced Materials in December 1997 (vol. 15, p. 1168) to create micro wires and micro wire connections between circuits. In his procedure two thin copper plates are placed between two inert highly charged electrodes. The electrodes induce opposite surface charges on the copper plates. The surface charges create copper ions that travel across a substrate from one plate to the other. Because of gravity and Brownian motion of the medium the ions slow down and deposit on a surface between the copper plates. The ions deposited between the plates form a non-conducting wire type pattern. To make the wire conductive the pattern is placed in a copper plating solution for a set time.
Dr. Bradley's technique is called Spatially Coupled Bipolar Electrochemistry (SCBE), because the method avoids physical contact with the devices three-dimensional circuitry can be created. His technique is also used to form functional catalysts in which the positioning of catalytic materials can be precisely placed on isolated particles a few microns wide allowing for the creation of designer catalyst that can be used in commercial and industrial applications.
Another technique to manipulate neutral atoms is by creating standing electromagnetic waves positioned on top of a substrate in a vacuum to focus neutral atoms into linear or dot patterns by dipole force interactions, as shown in U.S. Pat. No. 5,360,764, issued to Celotta, et al. This process which also works for ions is designed to create evenly spaced groups of linear or spotted patterns for semiconductor devices. To create single lines or dots, a filter or mask is used to block the unwanted material. The process works since atoms of different elements will only absorb photons with a specific energy. Because of this a group of tunable lasers can be set to a frequency just below the atoms abortion frequency so that the atoms will not absorb the photons. Instead the photons will interact with the atom and change the atom's momentum slowing it down. This procedure is called laser cooling. The use of multiple lasers can actually trap atoms in a suspended state. The 1997 Nobel Prize in physics was awarded jointly to Steven Chu, Claude Cohen-Tannoundji and William D. Phillips for the development of methods to trap and cool atoms.
In current fabrication of integrated circuits at any scale, an opaque mask or reticle with a desired pattern is created to block light usually infrared, or an electron beam from exposing a photon or an electron beam sensitive resist placed on top of a substrate. In the fabrication of integrated circuits the substrate is a semiconductor. In the creation of micro machines the substrate can be any dissolvable material from which the part can later be freed. After exposure the exposed area of the resist is then removed, if a positive resist is used, a void will be created. In the creation of semiconductor devices the void is filled with a selected doping material. The dopants most readily used are phosphorous pentoxide or boron nitride. After the dopant has been placed on the silicon it is placed in a furnace with temperatures between 950 and 1000 degrees Celsius. The dopant, because of the high temperature, will diffuse into the substrate. The dopant concentrations, depth, and distribution in the substrate are mostly unpredictable.
Silicon dioxide can also be formed on the substrate acting as insulation between a silicon substrate and the interconnecting wires. The silicon dioxide is formed at 1100 degree Celsius temperatures. During the formation of silicon dioxide the surface silicon is being consumed. The final stage is connecting the wires and annealing them at 475 degrees Celsius. These steps are usually repeated a few times to create integrated circuits or a micro machine. The size of the device is dependent on the wavelength of the resist exposing particles, the smaller the wavelength the greater the resolution.
In a semiconductor wafer the electrically active area is only 10 microns deep which is usually only 1% the thickness of a typical wafer used in commercial applications. If energetic short wave particles like x-rays or elections are used to expose the resist to achieve greater resolution, they can destroy the surface of the substrate. Furthermore, if the substrate is a semiconductor unknown defects in crystalline structure can form allowing for unwanted and unpredictable variations in the devices electrical properties through the thin shell in which the current flows. This can hamper the goal for current fabrication, which is to create micro devices as small and defined as possible. The more devices that can be fitted onto a single surface will reduce the cost, the delay in switching, and the power consumption of the device (up to a physical point).
In 1986 Gerd Benning and Heinrich Rohrer who shared the Nobe
Berman Jack
Lehrer Norman E.
S&F Technological Development and Solutions Partners
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