Optimal lithographic process control involves a closely coupled combination of test wafer and
product wafer characterization. It has been shown in previous work that MPX (Monitor Photo
Excursion) optical technology for line-end-shortening metrology of focus and dose provides reliable
and low cost product monitor solution. In this work we apply MPX technology to litho cell monitor
and control on test wafers. Focus-exposure matrix (FEM) wafers are measured and analyzed
automatically on a routine basis. Process window parameters are tracked over time by scanner,
including spatial analysis of results across the scanner field such as tilt and curvature.
Improvements in litho cell control are discussed.
A Phase-Grating Focus Monitor (PGFM) is used to assess the focus control of a state-of-the-art lithography scanner (TWINSCAN AT:1100) over substrate topography. The starting wafer flatness quality is found to be critical in minimizing the overall defocus distribution. In fact, on nearly all wafers, the most significant contributor to defocus across the wafer was the small-scale topography. Results obtained over programmed topography, created by etching various patterns into silicon, are found to agree well with the simulated defocus behavior based on the measurement of the wafer surface obtained on the scanner metrology stage. Finally, we report on preliminary focus control results over realistic device-type substrate topography, involving thin-film and polish effects.
The impact of flare on lithographic imaging has been the subject of increased investigation as critical dimension requirements and K1 factors continue to be reduced. All 'real world' lithographic systems include aberrations and non-uniformities that detract from the ability to produce the ultimate imaging possible. The increased acceptance of double exposure techniques, such as complementary phase shift, can greatly increase the sensitivities of the process by effectively doubling the flare exposure in each image. All optical imaging systems have some amount of stray light, or flare, that detracts from system performance, critical dimension (CD) control, and process latitude. The effects of flare are compounded with the use of multiple exposure processes are used since this doubles the amount of exposure energy going through the optics and therefore increase the amount of stray light. Flare was characterized on two 0.63NA 193nm lithographic scanners using two different measurement techniques. Using a double-exposure technique previously presented new data that characterizes the across slit flare performance of a 193nm lithography system is reported. Data showing the effect of lens contamination and cleaning is also presented. In addition, a different flare metrology technique based on MTF was used to characterize the flare effects at a range of spatial frequencies. Metrology requirements and limitations of each technique are also discussed.
KEYWORDS: Semiconducting wafers, Thin film coatings, Deep ultraviolet, Scanning electron microscopy, Metals, Image processing, Etching, Cadmium, Photoresist processing, Tin
The imaging performance of IBM's positive DUV resist is evaluated on SVGL Micrascan. Preliminary results on GCA excimer laser are included. Contamination effects are studied using 0.5 micron lines and spaces on Micrascan I using cross-sections at various delay times. The effects of delay times between different processing steps such as coat to expose and expose to PEB are studied. The performance is further evaluated by processing wafer lots on line for Micrascan I and II. Data on resolution, depth of focus and process latitude are presented for 0.35 and 0.5 micron geometries. The effects of PEB temperature variation are studied. Performance on different substrates (poly, metals and contacts) is evaluated.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.