Integrated stepwise statistical process control in a plasma...

Details Integrated stepwise statistical process control in a plasma... Integrated stepwise statistical process control in a plasma...

2002-06-07

2004-11-30

Hassanzadeh, Parviz (Department: 1763)

Semiconductor device manufacturing: process

Including control responsive to sensed condition

C438S689000, C156S345240, C118S712000

Reexamination Certificate

active

06825050

ABSTRACT:

The present invention relates to apparatus and methods for improving efficiency in the manufacture of integrated circuitry on a substrate, such as a semiconductor substrate for use in IC fabrication or a glass panel for use in flat panel display fabrication. More particularly, the present invention relates to apparatus and methods for integrating stepwise statistical processing functionalities into a plasma processing system environment to render the process of manufacturing, installing, qualifying, operating, maintaining and/or upgrading the plasma processing system more efficient.
Plasma processing systems have been around for some time. Over the years, plasma processing systems utilizing inductively coupled plasma sources, electron cyclotron resonance (ECR) sources, capacitive sources, and the like, have been introduced and employed to various degrees to process semiconductor substrates and glass panels. During processing, multiple deposition and/or etching steps are typically employed. During deposition, materials are deposited onto a substrate surface (such as the surface of a glass panel or a wafer). For example, deposited layers comprising various forms of silicon, silicon dioxide, silicon nitride, metals and the like may be formed on the surface of the substrate. Conversely, etching may be employed to selectively remove material from predefined areas on the substrate surface. For example, etched features such as vias, contacts, or trenches may be formed in the layers of the substrate. In both deposition and etching applications, multiple steps may be performed to achieve the proper deposition of materials and/or the acceptable etching of features through one or more layers.
As integrated circuits become more complex and their operating speeds increase, circuit designers are packing an ever increasing number of devices (such as transistors, resistors, capacitors, and the like) into a smaller area on the substrate. Furthermore, in order to achieve even higher speeds, circuit designers frequently resort to exotic and expensive materials to deposit and/or to etch the layers that form the resultant ICs. To accommodate these requirements, plasma processing systems are also becoming highly complex and expensive to manufacture and to operate.
In the semiconductor industry, the cost of ownership of a given plasma processing system is a critical issue for plasma processing equipment vendors and IC manufacturers alike. In a very simplistic sense, the cost of ownership of a given plasma processing system can viewed as the cost, in terms of time, effort, and money spent, to acquire and operate that plasma processing system per unit of production, e.g., per substrate successfully processed.
For equipment vendors, one way to reduce the cost of ownership is reduce the amount of time and effort associated with manufacturing, installing, and qualifying a plasma processing system for production use. For example, an equipment vendor would strive to minimize the time and effort required to produce a plasma processing system that satisfies a particular set of system specifications. During the installation process, an equipment vendor would also try to minimize the time and effort involved in assembling the various parts of the manufactured plasma processing system into a working unit at a customer site. During the qualification process, an equipment vendor would strive to minimize the time and effort required to ensure that an installed plasma processing system can satisfactorily perform a particular process required by the customer/IC manufacturer. By reducing the amount of time and effort required to manufacture, install, and qualify a plasma processing system for production use, equipment vendors can reduce the system acquisition cost and may be able to pass some or all of the savings to their customers (i.e., the IC manufacturers who purchase the plasma processing systems for use in producing ICs), thereby lowering the cost of ownership of that plasma processing system.
After a given plasma processing system is put into production use, one way to further reduce the cost of ownership of that plasma processing system is to increase yield, i.e., increasing the number of successfully processed substrates per any given time period. Under this approach, the cost of acquiring the plasma processing system is viewed as a sunk cost, and if that plasma processing system can be optimized to produce a greater number of commercially acceptable processed substrates per unit of time, the effective cost to produce each commercially acceptable processed substrate is lowered.
Yet another way to further reduce the cost of ownership is to increase the utilization of the plasma processing system, e.g., by minimizing the amount of time that the system is taken out of production for maintenance and/or upgrade so that the system could be employed for production for a larger percentage of the time. Maintenance is a big issue since the process involved in, for example, cleaning a plasma processing chamber, in diagnosing and replacing broken parts, and in requalifying a system after maintenance for subsequent production use is very time consuming. In one sense, some maintenance is unavoidable to keep the plasma processing system in good working order and to minimize the number of IC defects. However, unnecessary maintenance needlessly reduces the amount of time that a given system can be employed for production. Worse, incorrect maintenance procedures and/or intervals on certain subsystems can lead to severe damage to the plasma processing system and/or destroy many expensive substrates.
In metrology, equipment vendors and IC manufacturers alike examine the processed substrates for evidence of unacceptable defects, and to employ the information obtained from such examination as feedback in the manufacture, installation, qualification, operation, and upgrade processes. For example, one or more substrates may be processed as part of the system manufacturing process to allow an equipment vendor to examine the processed substrates and to determine whether the manufactured plasma processing system conforms to predefined system specifications. As a further example, after the various parts of the manufactured plasma processing system are shipped to a customer site and reassembled, one or more substrates may be processed therein, and the processed substrates may be examined to determine whether the plasma processing system has been correctly reassembled at the customer site. As yet another example, during the qualification cycle for a particular process recipe, one or more substrates may be processed to allow a process engineer to determine whether the plasma processing system can satisfactorily perform a process required by the customer. If the substrates show an unacceptable level of defect, specialists may be called upon to troubleshoot the plasma processing system, and the cycles of processing substrates, examining the processed substrates, and troubleshooting the plasma processing system based on the data obtained from the processed substrates may continue until the plasma processing system is brought into specification and is deemed satisfactory for production use.
While the processed substrates can furnish certain data useful in the manufacture, installation, and qualification of a plasma processing system, there are disadvantages associated with relying primarily on substrates data to guide the manufacturing, installation, and qualification processes. For example, if a process involves multiple steps, each with its own gas mixture, gas pressure, RF voltage and power settings, and duration, it is difficult to ascertain exactly, by examining a post-process substrate, which parameter in which step did not conform to specifications and is thus likely to be the source of the defects. In metrology, one can refer back to the log file to obtain more information but the process is not integrated and requires one or more wafer runs (and possibly ruining one or more wafers) before the problem is spotted.
Furthermore, the wh

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