Lithography equipment is undergoing some of the most significant changes since the introduction of the wafer stepper. The driving force behind these changes is the diffraction limit of optics. The resulting characteristics of new lithography equipment, to contend with the diffraction limit, are discussed. The high cost of lithography equipment has made mix-and-match lithography commonplace. Step-and-scan technology is the wave of the near-future, as a way to contend with the difficulty of manufacturing wide-field lenses. Resist processing equipment will undergoing few changes, but will often be integrated with steppers. Metrology is being stretched to its limits for technologies below 250 nm.
It's has been the general opinion of device manufacturers that deep ultraviolet imaging will be the imaging method required to produce 250nm and sub-250nm geometries for 256Mb-DRAM's and related logic technology. Traditional Wine lithography may not capable of manufacturing at these geometries and the use of deep UV radiation with "chemically amplified" photoresists will be required for these device programs. Issues regarding the problems that researchers are combating or have not yet considered in the evolutionary chain of deep ultraviolet photoresist development and implementation will be discussed. As researchers continue developing environmentally stable materials, there is a series of issues that device manufacturers need to resolve today as new quarter micron fabs are currently under construction. Fab designers may need to consider additional space for specialty tools or processes in order to produce quarter micron lithography. The issues concerning materials, process, reflectivity control, manufacturing facilities, quality control, photoresist manufacturing, photoresist cost and a proposed roadmap for the next several years of development will be discussed. The author will also provide a brief overview of current Mine photoresists and their capability to the 300= geometry region along with some basic chemistry regarding the principles of DNQ's and chemically amplified photoresists.
A brief perspective is given initially on the goals, exposure methods, performance and challenges in the lithography process. The basic framework for simulating optical lithog- raphy is then presented using three important physical aspects: imaging, resist exposure- bleaching and resist development etching. Image quality in both contact/proximity and projection printing are considered. The verification by comparison of simulated resist pro- files with SEM cross sections from resist images on wafers in then considered. The chap- ter concludes with a discussion of the challenges facing projection printing and the technology directions emerging to meet them. Greater detail on many of the concepts and models introduced in this Chapter can be found in subsequent chapters.
Introduction-Lithography is the key enabler for semiconductor manufacturing. Future Progress in circuit scaling depends on contrinued progress in lithography capability scaling. Lithograph is once again approaching a "barrier" where exisiting technology does not demonstrate a clear path for continued progress. We will explore some continuities and discontinuities in lithography that promise to drive the scaling process for many years.
Mask technology, for 0.25gm lithography and beyond, presents a significant challenge to both the mask industry and silicon industry. It is expected that optical lithography will continue to be the predominant approach, and the exposure wavelength of lithography tools will be pushed down from 365nm to 248nm and 193nm. It becomes inevitable that optical enhancements are required to provide necessary capabilities for achieving resolution at 0.2i.tm or below in manufacturing mode. However, most optical enhancement techniques such as phase shifting mask (PSM), optical proximity correction (OPC), off-axis illumination, and some combination of these methods, require substantial mask development efforts. The mask industry as a whole needs to deal with new modules, new materials, new pattern designs, sub-micron resolution, CD non- linearity effects, and high data volume, and then figure out a way to integrate solutions into silicon technology at a pace no slower than that required for silicon technology development. In many cases, a unique process or solution needs to be developed which is specific to one particular layer or one particular lithography option. In addition, in order to achieve high lithography productivity output, serious considerations need to be given for a possible increase in mask size, which by itself will have tremendous impact to the entire mask industry on tool set and material development. There is no doubt that mask technology has become a crucial and integral part of silicon technology. Its role is becoming increasingly important at 0.2511m lithography and beyond. In this presentation, we will first describe the role of mask technology by examining its significance to silicon technology. Secondly we will describe the major challenges facing mask technology. In the mask fabrication section, a few examples will be given to highlight major progress and key issues. Next, phase shifting mask technology and its challenges will be summarized. Lastly, a conclusion will be given.