This invention is designed to improve image quality of a projection optics lithography system (e.g. of the stepper and/or scanner type).
In a projection optics lithography system the image in photoresist is a function of the illumination source shape (or distribution), the object amplitude (the mask [or reticle] features), the lens attributes or pupil distribution, and the resist properties. The equation below states this in a more rigorous fashion
The “carrotted” variables in the above equation refer to sets of coordinate. Hence {circumflex over (x)}=(x,y) and z are the image space coordinates; {circumflex over (α)}=(α,β) and {circumflex over (α)}s are the pupil space coordinates. In the current use of source-mask optimization (SMO), the image, I, is the desired target. The source shape, J, and the Fourier transform of the Mask Spectrum are variables that are optimized. The Pupil and the Film (resist) are assumed fixed. SMO typically seeks to solve the inverse of this equation.
The present invention is designed to improve optical lithography image quality, by providing a determination of pupil amplitude and phase optimization, which can then be used in providing optimization at the pupil plane (e.g. by configuration of the projection optics, including providing pupil plane filter(s)). Thus, the present invention is designed to enable additional degrees of freedom to optimize the image quality produced by the optical lithography system. In essence, the present invention focuses on the pupil of the projection optics, as opposed to the illumination source and/or reticle, which are more traditionally the focus of a source mask optimization.
In a preferred embodiment, the present invention adds to a source mask optimization process (as a computational process) an additional computational feature that provides for determining pupil amplitude and phase optimization, thereby enabling optimization at the pupil plane (e.g. by configuration of the projection optics).
For example, the present invention can produce (determine) the metrics (amplitude and phase parameters) by which a customized pupil plane filtering (e.g. by one or more transmission filters) can be produced for a specific mask pattern.
One way the present invention is intended to depart from prior source mask optimization concepts is that it seeks to enhance the imaging properties of a scanner/stepper system by using the amplitude and phase distributions within the pupil of the projection optic. It is believed that the pupil has not been previously used in any source/mask optimization schemes. Using the pupil distribution as a free parameter gives many more degrees of freedom to optimize the lithographic image.
The principles of the present invention can be practiced with source mask optimization that also optimizes illumination and/or reticle parameters, or it can be practiced assuming the illumination and/or reticle parameters are fixed. Also, the invention can be practiced in a manner that adds a customized lens pupil function to the computation that is intended to result in the creation of a custom lens pupil plane filter with amplitude and phase parameters that have been calculated for a specific mask pattern.
Further features of the present invention will be apparent from the following detailed description and the accompanying drawing
As described above, the present invention relates to a method of improving optical image quality in a projection optics lithography system, e.g. of the stepper and/or scanner type, both of which are well known to those in the optical lithography art.
As illustrated in
In a projection optics lithography system the image in photoresist is a function of the illumination source shape (or distribution), the object amplitude (the mask features), the lens attributes or pupil distribution, and the resist properties. The equation below states this in a more rigorous fashion
The “carrotted” variables in the above equation refer to sets of coordinate. Hence {circumflex over (x)}=(x,y) and z are the image space coordinates; α=(α,β) and {circumflex over (α)}s are the pupil space coordinates. In the current use of source-mask optimization (SMO), the image, I, is the desired target. The source shape, J, and the Fourier transform of the Mask Spectrum are variables that are optimized. The Pupil and the Film (resist) are assumed fixed. SMO typically seeks to solve the inverse of this equation.
The present invention is designed to improve optical lithography image quality, by providing determining pupil amplitude and phase optimization, which can then be used in providing optimization at the pupil plane (e.g. by configuration of the projection optics, including providing pupil plane filter(s)). Thus, the present invention is designed to enable additional degrees of freedom to optimize the image quality produced by the optical lithography system. In essence, the present invention focuses on the pupil of the projection optics, as opposed to the illumination source and/or reticle, which are more traditionally the focus of a source mask optimization.
The basic process for configuring the projection optics, according to the present invention is schematically shown in
The invention also may be practiced using source-mask optimization. Hence, it can be thought of doing a source-mask-lens optimization. Moreover, the determination of pupil amplitude and phase optimization can be provided as part of a source mask optimization process, which can also provide optimization of either or both of the source or the mask of the projection optics system. The determination of pupil amplitude and phase optimization is produced with (a) either or both of the source shape and Fourier transform of the mask spectrum assumed fixed, or (b) either or both of the source shape and/or the Fourier transform of the mask spectrum treated as variables that are determined as part of the optimization process.
In implementing the source mask optimization represented by the formula above, the present invention allows the pupil phase and amplitude to be optimized, by having the pupil as the variable in the formula above. Based on the target (i.e. Scalar) Image, the formula above is used to optimize pupil phase and amplitude. This can result in solutions where the amplitude transmission and the phase of the pupil are variable. Essentially, if the pupil distribution is defined as:
{tilde over (H)}(α,β)=A(α,β)e−iϕ(α,β),
this invention allows constrained and unconstrained solutions of A and ϕ.
Thus, the present invention adds to a source mask optimization process (as a computational process) an additional computational feature that provides for determining pupil amplitude and phase optimization, thereby enabling optimization at the pupil plane (e.g. by configuration of the projection optics, including providing pupil filter(s)). One way the present invention is intended to depart from prior source mask optimization concepts is that it seeks to enhance the imaging properties of a scanner/stepper system by using the custom amplitude and phase distributions within the pupil of the projection optic. It is believed that the pupil has not been previously used in any source/mask optimization schemes. Using the pupil distribution as a free parameter gives many more degrees of freedom to optimize the lithographic image.
The principles of the present invention can be practiced with source mask optimization that also optimizes illumination and/or reticle parameters, or it can be practiced assuming the illumination and/or reticle parameters are fixed. Also the invention can be practiced in a manner that adds a customized lens pupil function to the computation that is intended to result in the creation of a custom lens pupil plane filter with amplitude and phase parameters that have been calculated for a specific mask pattern.
The distribution is optimized for the lithographic image in photoresist, and may allow for a custom amplitude, custom phase, and/or custom intensity distribution in the pupil of the projection optics (“PO”). For example, the present invention can produce (determine) the metrics (amplitude and phase parameters) by which customized pupil plane filtering (e.g. by one or more transmission filters) can be produced for a specific mask pattern.
Current scanners and steppers have huge flexibility in varying the phase of the pupil by manipulation of the Zernike aberrations; however, these are usually used to minimize Zernikes or match to other systems. The present invention would allow for the variation of those Zernikes with a simultaneous variation of the source and/or mask features to achieve the target image. This has the advantage of introducing more degrees of freedom to solve the inverse image equation. In addition, we seek to introduce customize amplitude transmission variation by the use of transmission filters at the pupil.
Finally, the optimization of the pupil distribution also can include changes to the Jones pupil of the PO when polarization illumination is used. In this case, the input polarization distribution in the lens pupil can be allowed to “float” in conjunction with the Jones pupils. The vector equation below shows the equation to be inverted:
where the function within the curly brackets are now all matrices and the polarization amplitudes per pupil point, P, have been introduced. The input polarization is defined by the object matrix, and can be unique for each pupil point. The pupil function H, is now in terms of a Jones pupil, so it can have solutions for multiple polarization basis functions.
Accordingly, the present invention is designed to enhance the imaging properties of a scanner/stepper system by using the amplitude and phase distributions within the pupil of the projection optic. Using the pupil distribution as a free parameter gives many more degrees of freedom to optimize the lithographic image. In addition, it allows for customized pupil filters to help enhance imaging in the scanner/stepper, particularly for low k1 imaging, i.e., k1<0.3.
Number | Name | Date | Kind |
---|---|---|---|
5467166 | Shiraishi | Nov 1995 | A |
5610684 | Shiraishi | Mar 1997 | A |
5677757 | Taniguchi | Oct 1997 | A |
5863712 | Von Bunau | Jan 1999 | A |
5929991 | McArthur et al. | Jul 1999 | A |
6118516 | Irie | Sep 2000 | A |
6304317 | Taniguchi | Oct 2001 | B1 |
6310679 | Shiraishi | Oct 2001 | B1 |
6597440 | Sasaki | Jul 2003 | B1 |
6795163 | Finders | Sep 2004 | B2 |
6833906 | Ohsaki | Dec 2004 | B1 |
6963390 | Smith et al. | Nov 2005 | B1 |
20050237512 | Smith et al. | Oct 2005 | A1 |
20050254024 | Marie Van Greevenbroek | Nov 2005 | A1 |
20050273753 | Sezginer | Dec 2005 | A1 |
20060244940 | Uehara | Nov 2006 | A1 |
20060290913 | Dieckmann | Dec 2006 | A1 |
20070188730 | Takeuchi | Aug 2007 | A1 |
20070296938 | Tel et al. | Dec 2007 | A1 |
20080175432 | Choi | Jul 2008 | A1 |
20080212183 | Uitterdijk et al. | Sep 2008 | A1 |
20080309897 | Wong | Dec 2008 | A1 |
20090091736 | Yamazoe | Apr 2009 | A1 |
20100119961 | Ye | May 2010 | A1 |
20100141925 | Cao et al. | Jun 2010 | A1 |
20100251202 | Pierrat | Sep 2010 | A1 |
20110032499 | Kawashima | Feb 2011 | A1 |
20110173578 | Tsai | Jul 2011 | A1 |
20110230999 | Chen | Sep 2011 | A1 |
20140282298 | Fan | Sep 2014 | A1 |
20150131066 | Yamazoe | May 2015 | A1 |
Number | Date | Country |
---|---|---|
2006005272 | Jan 2006 | JP |
2006245085 | Sep 2006 | JP |
Entry |
---|
“EETimes What is the source mask optimization” 02/09 pp. 1-3. |
Computational lithography: virtual reality and virtual virtuality (Computational lithography Lam 2009.pdf) pp. 1-10. |
“Experimental Result and Simulation analysis for the use of Pixelated illumination from Source Mask Optimization for 22 nm Logic Lithography Process” Lai et al. |
“Rigorous Vectorial Modeling for Polarized Illumination and Projection Pupil in OPC” Zhang et al., SPIE vol. 7028 2008; pp. 1-11. |
“Lithographic Image Simulation for the 21st Century with 19-Century Tools” Gordon and Rosenbluth, SPIE vol. 5182 2003; pp. 73-87. |
“Impact of across pupil transmittance variation in projection lenses on fine device pattern imaging” Sato et al., SPIE 5040 2003 ; pp. 33-44. |
“Enhancement of photolithography resolution by fractional Fourier domain filtering” Microelectronic engineering 67-68 (2003) p. 31-38. |
“Larger Depth of Focus for Increased Yield” Cathey and Johnson SPIE vol. 5754; pp. 1493-1499. |
“Coherent Multiple Imaging by means of Pupil Plane Filtering” SPIE vol. 3679 1999; pp. 762-771. |
“Practical approach to full-field wavefront aberration coeffients using phase wheel targets” Zavyalova, et al., SPIE vol. 6154-35; pp. 1-9. |
“On the quality of measured optical aberration coefficients using phase wheel monitor” Zavyalova, et al., SPIE 6520 2007; pp. 1-9. |
“Challenges and solutions in the calibration of projection lens pupil-image metrology tools” Slonaker et al., SPIE vol. 7274 2009; pp. 1-12. |
Zavyalova et al., “Practical approach to full-field wavefront aberration measurement using phase wheel targets”, Mar. 2006, pp. 1-9, vol. 6154, SPIE, USA. |
W. Thomas Cathey and Gregory Johnson, “Larger depth of focus for increased yield”, May 12, 2004, pp. 1493-1499, vol. 5754, SPIE, USA. |
J. Du et al., “Enhancement of photolithography resolution by fractional Fourier domain filtering”, (2003), pp. 31-38, vol. 67-68, Microelectronic Engineering, China. |
Dylan McGrath, “What is source-mask optimization?”, Feb. 27, 2009, pp. 1-3, EETimes.com, Santa Clara USA. |
Miklos Erdelyi et al., “Choerent Multiple Imaging by means of Pupil Plane Filtering”, Mar. 1999, pp. 762-771, vol. 3679, SPIE, Santa Clara USA. |
Kafai Kai et al., “Experimental Result and Simulation Analysis for the use of Pixelated Illumination from Source Mask Optimization for 22nm Logic Lithography Process”, 2009, pp. 72740A-1 through 72740A-12, vol. 7274, SPIE, USA. |
Edmund Y. Lam and Alfred K. K. Wong, “Computation lithography: virtual reality and virtual virtuality”, Jul. 20, 2009, pp. 12259-12268, vol. 17, No. 15, Optical Society of America, USA. |
Lena V. Zavyalova et al., “On the quality of measured optical aberration coefficients using phase wheel monitor”, 2007, pp. 1-9, vol. 6520, SPIE, USA. |
Kazuya Sato et al., “Impact of across pupil transmittance variation in projection lenses on fine device pattern imaging”, 2003, pp. 33-44, vol. 5040, SPIE, USA. |
Steve Slonaker et al., “Challenges and solutions int he calibration of projection lens pupil-image metrology tools”, 2009, pp. 1-10, vol. 7274, SPIE, USA. |
Qiaolin (Charlie) Zhang et al., “Rigorous Vectorial Modeling for Polarized Illumination and Projection Pupil in OPC”, 2008, pp. 1-11, vol. 7028, SPIE, USA. |
Ronald L. Gordon and Alan E. Rosenbluth, “Lithographic Image Simulation for the 21st Century with 19th—Century Tools”, 2003, pp. 73-87, vol. 5182, SPIE, Bellingham USA. |
Number | Date | Country | |
---|---|---|---|
20130286369 A1 | Oct 2013 | US |