Electrical transmission or interconnection systems – Plural supply circuits or sources – Substitute or emergency source
Reexamination Certificate
1998-05-21
2001-04-10
Paladini, Albert W. (Department: 2836)
Electrical transmission or interconnection systems
Plural supply circuits or sources
Substitute or emergency source
C307S023000
Reexamination Certificate
active
06215202
ABSTRACT:
FIELD OF THE INVENTION
The field of the invention relates generally to the stabilization and control of electric power delivered from a utility grid to a load. In particular, the field of the invention relates to a shunt connected superconducting energy management system (SEMS) providing a single switched connection between a utility grid and one or more power sensitive loads such as a semiconductor manufacturing plant having power requirements in the range on the order of 2 megawatts (MW) to 200 MW. When a voltage disturbance is sensed in the grid, the power control circuitry aspect of the invention simultaneously isolates the load and SEMS from the grid by a single switch which simultaneously provides full back up power to the load instantaneously without voltage transients or disturbances. The provision of instantaneous back up power to one or more large loads without voltage transients was not previously possible with conventional back-up power systems.
BACKGROUND
The role of the power transmission utility industry in providing reliable service is under increasing pressure in today's wholesale power market, which must manage an increasing number of transmission modes, brought upon by deregulation. Power generation outages or transmission line faults several systems away can produce voltage disturbances throughout interconnected power systems. Transmission planning done for individual systems decades ago did not anticipate these changes, nor the higher power quality standards that would be required by today's critical manufacturing processes, such as for example, semiconductor and integrated circuit fabrication. From a utility company's perspective, the degree of reliability of power must be “good enough” for the general public, and added enhancements for a particular industry face difficulty obtaining regulatory approval if the costs are to be borne by other electric customers.
Deregulation of the Utility Industry and increased sharing of existing utility grid networks are expected to result in a further decline in the quality of electric power available for industrial consumers. In a deregulated environment utilities will begin to minimize investment and maintenance expenditures and therefore the grid infrastructure will become older and less reliable, thereby decreasing power quality. Momentary sags and power interruptions cause at least $26 billion in downtime in terms of productivity in the United States alone. Lost revenue due to power quality problems for a typical 200 millimeter wafer semiconductor manufacturing factory in the United States is estimated to be in the range of $20-$50 million per year per plant.
Exacerbating the problem are the variety of entities involved in supporting semiconductor manufacturing, none of whom take full responsibility for ownership of the power quality problem. The industry trend is toward higher performing equipment within plants which may typically lead to greater sensitivity to a voltage disturbance. Existing solutions for distributed power quality within a plant, such as a conventional uninterruptable power supplies (UPS), often create unacceptable harmonic distortions in power, thereby increasing instability and leaving gaps in protection that are discovered piecemeal as particular plant or grid operating scenarios are developed.
There is an increasing need for clean, uninterrupted electric power to be provided for today's power sensitive industrial processes. For example, the optical industry, hard disk production, textiles, paper mills, plastic foil production or other complex processes involving rotating machinery incur severe economic losses in terms of damaged product and down time when there is a power interruption or undervoltage condition on the utility grid. In particular, semiconductor manufacturing processes are especially sensitive to interruptions, undervoltage conditions or any discontinuity on the utility grid supplying power to the plant.
The increasing demand for semiconductor wafer manufacturing plants to provide smaller, faster integrated circuits with device dimensions which are approaching the wavelength of visible light has created an urgent need for clean, stable, uninterrupted electric power. As semiconductor wafer processing increasingly requires lithography at deep submicron dimensions, the complex series of lithographic process steps and positioning of wafers become extremely sensitive to even slight variations in power.
Miniaturization, which has been the driving force for achieving performance and cost improvements in very large scale integrated systems (VLSI), emphasizes more reliable VLSI devices as well as higher performance. The objective today in both high speed logic and fast memories is toward higher integration levels. Higher integration levels are seen as the key to obtaining higher device performance. At submicron dimensions, even slight variations in power or minor voltage discontinuities for as little as 50 milliseconds can result in losses of wafers containing integrated circuits worth millions of dollars. Refer to FIG.
7
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The sensitivity of modern VLSI technology to even slight variations in power can be seen from the following example. Major applications in MOS technology as well as increasing use of bipolar structures include polysilicon gate electrodes and interconnects. Poly layers in direct contact with the silicon substrate are used as diffusion sources and buried contacts. High performance devices are realized by means of the extremely high resistivity of lightly doped polysilicon. In device fabrication applications, poly structures must be exposed to an entire range of process technologies such as oxidation, diffusion and implantation. These processes are very sensitive to even slight voltage variations.
Further, VLSI structures and devices are inherently multi-layered with multiple interfaces whose properties may be crucial to the resulting device behavior. As dimensions shrink to 0.25 microns and below, even minor variations in power can detrimentally affect the extreme precision which must be adhered to when implementing VLSI fabrication processes. Processes such as reactive ion etching, plasma enhanced chemical vapor deposition (CVD), diffusion, and ion implantation are inherently electric powered based. Other methods can be used to shrink dimensions of integrated circuits even further, such as extreme ultraviolet lithography (EUV), x-ray lithography and electron beam lithography. Since the foregoing processes are arguably capable of shrinking dimensions smaller than 0.1 microns, such processes are extremely sensitive to undervoltage conditions such as voltage transients induced by lightning, interruptions or sags in voltage due to increased utility demand, or simply an inability to provide clean power due to varying industrial loads.
As lithographic processing becomes ever more complex, it becomes necessary to provide a stable, uninterrupted source of power to steer electron beams or conduct other lithographic processes with complete, invariant accuracy. Power discontinuities which may have been tolerated even a few years ago are now unacceptable due to the fact that the extremely small device dimensions now magnify any power deviation. Also, the more exacting semiconductor processing technologies are creating an increased power demand. Consequently, semiconductor processing plants are operating at higher electric power levels.
In order to solve the problems in meeting increased power demands and providing an uninterrupted source of clean power to a critical manufacturing process or the like, one conventional approach is the use of distributed power protection (uninterruptable power supply or UPS) at the equipment level. However, implementation of this solution has proven difficult and only partially effective for the following reasons.
It is difficult to identify the critical loads that require immediate protection since the priority of the loads may be changing in accordance with the specific semiconductor processing step being undertaken. Distribut
Luongo Cesar A.
Unterlass Franz Josef
Bechtel Enterprises Inc.
Deberadinis n R.
Morrison & Foerster / LLP
Paladini Albert W.
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