Technology Used in Semiconductor Lithography Equipment
Semiconductors are constantly evolving. Canon has focused on developing far-sighted technology for semiconductor lithography equipment that meets the strict cutting edge demands. These technologies serve as the driving force behind Canon's optical and control technologies.
Stage Synchronization Control Technology
Achieving High Yield Rates and High Productivity of Semiconductors
Among the technologies supporting the manufacture of semiconductors, synchronization control technology is as important as circuit miniaturization technology. The precision of stage positioning has a direct effect on yield rates, while stage speed affects productivity as measured by hourly "throughput."
Semiconductor lithography equipment which uses the scan and repeat method*1 carries out wafer exposure while continually synchronizing the movements of the wafer and reticle stages. Ensuring the accurate positioning of reticle patterns on the wafer during exposure with proper focus and uniform light intensity requires the extremely precise control of all moving sections.
To achieve ultra-fine line widths, the flatness of the wafer*2 also must not be overlooked. If the positioning of both stages and the lens is not corrected for each shot in accordance with even the slightest inconsistencies on the surface of the wafer, the exposure of microscopic circuit lines would not be possible.
- *1 Scan and repeat method
A method of exposure in which both the reticle and wafer stages move. Compared with the step and repeat method, in which only the wafer stage moves, this approach offers the merits of greater depth of focus while facilitating larger chip sizes.
- *2 Wafer flatness
Not only the curvature of the wafer surface as a whole, but even slight imperfections of only a few nanometers within a single shot area (about 20 mm2) can create problems.
Core Technology for LSI Integration Expected to be Expanded to Postprocessing
In the semiconductor lithography process where a pattern on a mask is projected onto a single wafer numerous times, the position is determined by reading several alignment (positioning) marks on the surface of the wafer. Meanwhile, 3-D packaging is believed to be promising for further increasing density, and development of technology for performing alignment using the back of the wafer was hurried in order to achieve this. 3-D packaging refers to a technology in which several LSIs containing circuits are placed in layers and a circuit is completed using vertical electrodes to form a single LSI. The process used for forming the holes for the electrodes requires accurate alignment.
Canon has developed the TSA*3-scope for reading alignment marks on the back of the wafer by transmitting infrared light through the wafer. This TSA-scope has the benefit of not having a restricted range of measurement when compared to methods that directly detect alignment from the back of the wafer. Moreover, as it can be used in a variety of packaging processes, Canon is developing a diverse range of applications utilizing this as a key technology for products used in postprocessing in semiconductor fabrication.
- *3 TSA (Through Silicon Alignment)
An alignment method using long-wave infrared light for observing alignment marks formed on the back of the wafer through the silicon.
Exposure Equipment Application Platform
Supporting Total Productivity Improvement
Semiconductor exposure equipment software not only achieves maximum performance from the hardware, but also plays a vital role by contributing to increasing total productivity. The application platform that forms the core of the software system is composed of an infrastructure connecting multiple CPUs / OSs and a plug-in framework that supports basic control and data management, making it possible to rapidly adapt to the needs of diversifying semiconductor manufacturers.
Not only does this technology provide a common platform for semiconductor manufacturers' various online, GUI, EES,*4 and other interfaces, but by opening these to external access, it allows access and precise control of all kinds of internal and external data and makes providing solutions simple.
At present, this platform is being applied to the FPA-7000 series and future plans include linking it with a "recipe server"*5 to develop it into a solutions system.
- *4 EES (Equipment Engineering System)
Linking not only with exposure equipment but also with peripheral equipment is indispensable for improving precision and productivity in semiconductor manufacturing. EES provides a system and interface for data sharing.
- *5 Recipe server
Makes possible the creation and editing of "recipes" (control information) for wafer exposure for each piece of equipment and can be linked to a production management system.