TFT-LCD equipment for the year 2000 Monitor Market
06/01/1997
TFT-LCD equipment for the year 2000 monitor market
Robert Conner, Applied Komatsu Technology Inc., Santa Clara, California
The thin-film transistor/liquid crystal display (TFT-LCD) industry is at a critical juncture. The demand for TFT-LCDs will likely increase over the next five years if TFT-LCDs can successfully displace CRTs for most desktop PC and workstation applications. In order to address this larger consumer market, the industry must cope with several challenges:
progressively larger LCD sizes, higher resolutions, and new aspect ratios;
incessant pressure to reduce prices in order to develop new markets;
"boom/bust" cycles resulting in rapid transitions from excess capacity/falling prices to shortages and rising prices;
critical need to improve the productivity and return-on-investment for capacity expansion; and
many uncertainties on both the demand side (i.e. the market "sweet spots" in 1998-2000) and supply side (i.e. the best substrate size for a new fab).
The market`s requirements advance at a surprisingly rapid rate. High-end applications quickly become the mainstream, causing demand-supply imbalances. The emerging TFT-LCD monitor market offers an opportunity to break out of this cycle.
This far, substrate sizes optimized for efficient production of one particular LCD size have become inefficient when the market moves to a slightly larger LCD size (Table 1). The constant race to larger substrate sizes results in short useful lifecycles of fabs and fab equipment. To assure its own future growth as a profitable business, the industry should agree on an LCD size "roadmap" that logically addresses at least two generations of substrate sizes. This will allow equipment makers to focus their efforts on process and productivity issues rather than re-engineering their systems for new and nonstandard substrate sizes that vary among their customers.
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Figure 1. Trend to higher resolutions and dots/in.
Monitor market "sweet spots"
At recent trade shows, the multitude of TFT-LCD monitors shown range in size from 12.1 to 25 in., and extend the sizing logic that has so far applied to notebook computers. In notebooks, very small (<1-in.) size change increments have occurred in recent years as 8.4, 9.5, 10.4, 11.3, 12.1, and now 13.3 in. have all become mainstream - albeit short-lived - TFT-LCD sizes.
However, in the desktop computer monitor market, consumers are accustomed to buying monitors in a few standard sizes. As TFT-LCD monitors progress from niche into mainstream market status in two to three years, display sizes will likely consolidate into a few market "sweet spots."
TFT-LCD monitor sizes in 1998 and beyond may have slightly smaller equivalent dimensions than standard CRT monitor sizes, for the following reasons:
TFT-LCD-to-CRT comparisons will be based on higher display quality, not display area. TFT-LCDs will have higher resolution (dots/inch, or dpi) that allows a character size of approximately 90% of a CRT`s to have equivalent quality.
Viewable area for CRTs is about 10% smaller than the measured diagonal dimension, while TFT-LCDs are measured from the edge of the viewable part of the display. Thus, a 14-in. TFT-LCD provides equivalent display quality to a 17-in. CRT (i.e., the LCD`s slightly smaller character size compared with the 17-in. CRT`s 15-16-in. viewable area).
Users will be willing to trade-off a small amount of the LCD`s area (1-in. diagonal) for a price similar to CRTs.
Users will be increasingly making their display choices based on image quality, because increased resolution, measured in dpi, dramatically enhances usability. Figure 1 shows an upward progression of resolutions. Today`s best CRT monitors have 85-100 dpi (0.30-0.25 mm dot pitch) and are largely unable to go higher than 100 dpi. The 100 dpi resolution is marginally acceptable for readability - that is what today`s computer users are used to. Yet, moving to 120 and 150 dpi, and beyond to 300 dpi, gives remarkable increases in clarity. At 150 dpi, the display begins to approximate the quality of the printed page. At 300 dpi, users will find the display as easy to read as a newspaper or book.
LCD and substrate size relationship
TFT-LCD manufacturers are torn between two opposing forces - the desire to build larger LCDs by using larger substrate sizes (than their competitors) versus the desire to standardize on a substrate size in order to reduce manufacturing cost. The substrate area of TFT-LCDs has almost quadrupled during the last five years, with substrate generations averaging only 2-2.5 years.
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Figure 2 shows the number of LCDs produced per various substrate sizes. Each display size uses the available substrate area with differing degrees of efficiency. Any substrate area not used for the display is wasted and must be minimized.
The relationship between probable TFT-LCD monitor sizes and substrate sizes is shown in Table 2, which shows the maximum (most efficient) number of LCDs/substrate for increasing substrate sizes. For example, the maximum XGA (4:3 aspect ratio) LCD sizes on a 550 ? 650-mm substrate are (6) 12.5 in. or (4) 14.9 in. Substrate sizes should increase by major steps to increase the number of market "sweet spot" LCDs produced per substrate. For instance, 600 ? 720-mm, 750 ? 950-mm, and 900 ? 1100-mm substrates all efficiently produce LCDs in the three monitor market "sweet spots."
This "roadmap" enables the LCD manufacturer to produce the same efficient combination of three LCD sizes on successive substrate generations, minimizing the risk of inefficient production while providing a cost-reduction path. Six 14-in. LCDs (equivalent to 17-in. CRTs in character clarity) can be produced on 600 ? 720-mm substrates to begin significant penetration of desktop monitors. Nine 14-in. LCDs, produced on future 750 ? 950-mm substrates, offer a cost reduction. Twelve 14-in. LCDs, produced on future 900 ? 1100-mm substrates, offer further savings. As long as the market "sweet spots" don`t change, the 600 ? 720-mm fab continues to be efficient when subsequent generation fabs come online - the fab`s lower depreciation costs offset its disadvantage of producing fewer substrates.
Fab investment productivity and substrate sizes
To date, the short-term competitive advantage of larger substrate sizes has outweighed industry standardization efforts, resulting in very short useful lifecycles for TFT-LCD manufacturing equipment. Each new substrate size requires that all the equipment in the TFT array manufacturing line be able to support it. The fab`s first year generates more revenue than in subsequent years due to falling TFT-LCD prices.
Table 2 shows that a 600 ? 720-mm substrate provides a 50-100% increase (2-3?) in the number of LCDs/substrate with just a 21% substrate area increase over a 550 ? 650 mm. Since a 600 ? 720-mm fab is a stretch of a third-generation fab, it benefits from the third generation`s learning curve, providing a fast production start-up ramp with minimum risk and cost increase, hence, a significant productivity increase.
Both 750 ? 950-mm and 900 ? 1100-mm fabs require a complete new set of equipment. A 750 ? 950-mm fab produces 50-100% more LCDs than 600 ? 720-mm (or 125-300% than 550 ? 650 mm). The 750 ? 950-mm size provides less technical risk than 900 ? 1100 mm and hence higher probability of a high-volume fourth-generation production fab by the year 2000. The industry must assess the magnitude of the technical risks in going to 750 ? 950 mm for the fourth generation versus a more difficult 900 ? 1100-mm substrate size.
Summary
The TFT-LCD industry is entering a significant new period. First, it is transitioning into the mainstream market for desktop computer displays, where TFT-LCDs will soon begin to displace CRTs. Also, it is about to migrate to a larger substrate size that, if carefully chosen as part of an industry-wide standard "Roadmap," can greatly increase fab profitability and bring new efficiencies to the production of TFT-LCD manufacturing equipment. Standards on a few LCD sizes will enable a consistent, highly productive fab migration that addresses the market "sweet spots" in the mainstream consumer monitor market.