Semiconductor device manufacturing: process – With measuring or testing
Reexamination Certificate
2001-11-30
2004-08-10
Picardat, Kevin M. (Department: 2822)
Semiconductor device manufacturing: process
With measuring or testing
C438S016000, C702S179000, C702S182000, C702S183000, C702S188000
Reexamination Certificate
active
06773932
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates generally to facility management and control systems and, more particularly, to facility management and control systems and methods for use in the semiconductor wafer manufacturing industry to collect process data including particle measurement data from remote locations.
BACKGROUND OF THE INVENTION
In order to monitor and control modern industrial processes, facility management and control systems have been developed. Facility management and control systems collect various types of process data. A facility management and control system can then analyze the process data for quality control purposes as described below.
The measurement instruments that provide the process data are typically distributed throughout the facility with the particular arrangement dependent upon the nature of the process being monitored and the configuration of the facility. In addition, various types of measurement instruments can be employed depending upon the process data that is to be collected. For example, measurement instruments are typically employed to measure process data such as temperatures, pressures, humidity levels, switch positions and the like. While these measurement instruments can operate independently, the process data provided by the measurement instruments that monitor a particular stage of a process are oftentimes collected by a programmable logic controller.
Although the measurement instruments are typically distributed at various locations throughout the facility depending upon the particular stage of the process that is to be monitored, facility management and control systems generally include a computer for collecting and processing the data provided by the various measurement instruments. The computer is typically located at a relatively centralized position, such as within a control room or the like. As such, the computer is generally remote from most, if not all, of the measurement instruments by being positioned in a different room of the same building or in another building altogether. By collecting the data provided by the measurement instruments or, more commonly, by one or more programmable logic controllers with a computer, the data can be more thoroughly analyzed such as by cross-checking or correlating the data obtained by measurement instruments that are designed to monitor different stages of the process.
The computer can process the data in various manners for quality control and other purposes. In this regard, the data can be examined from a historical perspective in an attempt to determine, after the fact, the processing conditions that existed during the fabrication of products that were eventually determined to be of either unusually high quality or unacceptably low quality. In order to avoid fabricating a number of unacceptable products prior to detecting the problem and taking corrective action to bring the process back into tolerance, the computer can compare the current process data to predetermined acceptable ranges of process data. As such, if the process data collected by the measurement instruments falls outside the predetermined range of acceptable process data, the central computer can trigger an alarm such that the process parameters can be quickly adjusted prior to fabricating a large number of unacceptable products.
One example of a process for which a facility management and control system has been developed is the wafer fabrication process. In this process, wafers, such as silicon wafers, undergo a number of different process steps in order to fabricate wafers having the desired characteristics, such as the desired resistivity, surface roughness, etc. A facilities management and control system that includes a computer and a number of distributed measurement instruments is particularly useful for a wafer fabrication process since slight variations in the process parameters can substantially alter the characteristics of the resulting wafers, thereby causing wafers that will be unacceptable to be fabricated as a result of only minor changes in the process parameters. A facilities management and control system is also advantageous for a wafer fabrication process since the throughput of a wafer fabrication process is relatively high such that it is desirable to detect variations in the process parameters as soon as possible in order to reduce the number of unacceptable wafers that are fabricated.
In a wafer fabrication process, one of the most important process parameters is the particle count at different stages. In this regard, wafers are subjected to various environments during the fabrication process, some of which are designed to be ultra-pure environments having relatively few particles or contaminants. For example, at different stages of the fabrication process, a wafer is typically washed with ultra-pure water, exposed to ultra-pure chemicals, subjected to high pressure gas, such as hydrogen or nitrogen, having relatively few particles or subjected to an aerosol having relatively few particles, such as within a cleanroom. During any of these stages of the fabrication process, it is desirable to measure the particles in the particular medium, such as the water, chemical, gas or aerosol.
Two types of particle measurements are accumulated particle counts and differential particle counts. Accumulated particle counts are a running total of the particles, typically having at least a predefined minimum size or diameter, detected within a window of time. Thus, an accumulated particle count is typically the sum of several measurements taken during the window of time. Conversely, differential particle counts measure the change in particles, also typically having at least a predefined minimum size, from one measurement to the next.
These particle measurements can then be used to monitor particle levels and to track changes in the particle levels. Historical trends can be identified and used to analyze particle data correlation with wafer quality and other manufacturing processes. Based upon historical trends and related process data, acceptable operating levels and/or thresholds for accumulated particle counts and differential particle counts can be established to maintain wafer fabrication quality standards. Since the accumulated and differential particle counts each provide somewhat different and useful data, it is therefore desirable to measure and track the accumulated particle counts and differential change in particle counts from measurement to measurement. As such, various particle measurement instruments have been developed and are commercially available to provide these particle counts.
Unfortunately, these conventional particle measurement instruments are generally unable to transmit the data, such as the particle counts, that has been collected to a computer that is remote from the particle measurement instruments in the same manner as other measurement instruments or programmable logic controllers. As such, dedicated computers were oftentimes co-located with the particle measurement instruments in order to collect and characterize the data. In order to correlate the data collected by the particle measurement instruments with the data collected by various other measurement instruments distributed throughout the wafer fabrication facility, technicians would have to manually collect the particle data from the dedicated computers associated with the respective particle measurement instruments distributed throughout the facility, such as by obtaining a printout of the particle data from each dedicated computer or downloading the particle data onto a computer diskette or the like. Typically, the particle data is then manually re-entered into a spreadsheet. By copying other process data from the facilities management and control system, i.e., the process data collected by other measurement instruments, and by exporting this other process data in spreadsheet format, this other process data can be merged with the particle data and the combined data set can be evaluated. As such, the various dif
Carlson Leif
Robinson Michael M.
Alston & Bird LLP
Picardat Kevin M.
Seh America, Inc.
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