For the next years optical lithography stays at 193nm with a numerical aperture of 1.35. Mask design becomes more
complex, mask and lithography specifications tighten. The k1 factor comes close to 0.25 which leads to a tremendously
increased Mask Error Enhancement Factor (MEEF). This means that CD errors on mask are getting highly amplified on
wafer. Process control becomes more important than ever. Accurate process control is a key factor to success to maintain
a high yield in chip production.
One key parameter to ensure a high and reliable functionality for any integrated circuit is the critical dimension
uniformity (CDU). There are different contributors which impact the intra-field CD performance at wafer such as mask
CD uniformity, scanner fingerprint, resist process etc. In the present work we focus on improvement of mask CD
signature which is one of the main contributors to intra-field CD uniformity. The mask CD uniformity has been
measured by WLCD32 which measures the CD based on proven aerial image technology. Based on this CD input the
CD uniformity was corrected by CDC200TM and afterwards verified by WLCD32 measurement. The CDC200TM tool
utilizes an ultrafast femto-second laser to write intra-volume shading elements (Shade-In ElementsTM) inside the bulk
material of the mask. By adjusting the density of the shading elements, the light transmission through the mask is locally
changed in a manner that improves wafer CDU when the corrected mask is printed.
Additionally, the impact of the improved CD uniformity on the lithography process window was investigated. Goal of
the work is to establish a process flow for mask CD uniformity improvement based on mask CD metrology by WLCD32
and mask CD uniformity control by CDC200TM and to verify its impact on the lithography process window. The
proposed process flow will be validated by wafer prints.
It was shown that the WLCD32 has an excellent correlation to wafer data and an outstanding CD repeatability. It
provides a reliable input for CD uniformity correction and is the tool of choice to verify the CD uniformity improvement
after CDC200TM treatment.
For mask signature matching in the case of alternating phase-shifting mask it is shown that it is can be achieved using
matching of aerial imaging. This is in contrast to the traditional approach of manufacturing an identical copy of the
reference mask. Beside description of the method AIMS and wafer data are shown that proof its successful application
on a product mask.
For the next years optical lithography stays at 193nm with a numerical aperture of 1.35. Mask design becomes more
complex, mask and lithography specification tighten and process control becomes more important than ever. Accurate
process control is a key factor to success to maintain a high yield in chip production.
One of the key parameters necessary to assure a good and reliable functionality of any integrated circuit is the Critical
Dimension Uniformity (CDU). There are different contributors which impact the total wafer CDU: mask CD uniformity,
scanner repeatability, resist process, lens fingerprint, wafer topography etc.
In this work we focus on improvement of intra-field CDU at wafer level by improving the mask CD signature using a
CDC200TM tool from Carl Zeiss SMS. The mask layout used is a line and space dark level of a 45nm node Non Volatile
Memory (NVM). A prerequisite to improve intra-field CDU at wafer level is to characterize the mask CD signature
precisely. For CD measurement on mask the newly developed wafer level CD metrology tool WLCD32 of Carl Zeiss
SMS was used. The WLCD32 measures CD based on proven aerial imaging technology. The WLCD32 measurement
data show an excellent correlation to wafer CD data. For CDU correction the CDC200TM tool is used which utilizes an
ultrafast femto-second laser to write intra-volume shading elements (Shade-In ElementsTM) inside the bulk material of
the mask. By adjusting the density of the shading elements, the light transmission through the mask is locally changed in
a manner that improves wafer CDU when the corrected mask is printed.
In the present work we will demonstrate a closed loop process of WLCD32 and CDC200TM to improve mask CD
signature as one of the main contributors to intra-field wafer CDU. Furthermore we will show that the process window
will be significantly enlarged by improvement of intra-field CDU. An increase of 20% in exposure latitude was
observed.
One of the key parameters necessary to assure a good and reliable functionality of any integrated circuit is the Critical
Dimension Uniformity (CDU). There are different contributors which impact the total CDU: mask CD uniformity,
scanner and lens fingerprint, resist process, wafer topography, mask error enhancement factor (MEEF) etc.
In this work we focus on improvement of intra-field CDU at wafer level by improving the mask CD signature using a
CDC200TM tool from Carl Zeiss SMS. The mask layout used is a line and space dark level of a 45nm node Non Volatile
Memory (NVM). A prerequisite to improve intra-field CDU at wafer level is to characterize the mask CD signature
precisely. For CD measurement on mask the newly developed wafer level CD metrology tool WLCD32 of Carl Zeiss
SMS was used. The WLCD32 measures CD based on aerial imaging technology. The WLCD32 measurement data show
an excellent correlation to wafer CD data. For CDU correction the CDC200TM tool is used. By utilizing an ultrafast
femto-second laser the CDC200TM writes intra-volume shading elements (Shade-In ElementsTM) inside the bulk of the mask. By adjusting the density of the shading elements, the light transmission through the mask is locally changed in a
manner that improves wafer CDU when the corrected mask is printed.
In the present work we will demonstrate a closed loop process of WLCD32 and CDC200TM to improve mask CD
signature as one of the main contributors to intra-field wafer CDU.
As we move technology further and further down the geometry scale we are coming upon imaging situations where our use of existing optical lithography is being questioned due to the lack of process margin in manufacturing lines. This is especially apparent in the imaging of contacts where memory devices, that generally have the densest arrays of these features, may no longer be able to print the desired features. To overcome this it is necessary to either modify the design, a very expensive and time consuming process, or find an imaging process capable of printing the desired features. Electron Projection Lithography (EPL) provides an option to print very small features with a large process margin.
In this paper we detail the performance of both memory and logic based designs in an EPL process. We detail the manufacture and results of stencil mask manufacture. Data is also presented showing the imaging results (DOF, exposure latitude, pattern transfer) of features down to 50nm imaged on Nikon’s EB1A tool.
Recent development work on the EUV electric capillary discharge source been has focused on two areas: increasing EUV power generation and minimizing debris deposition on plasma facing optics. To achieve high-power operation, a pulser capable of driving the source up to 1.7 kHz and a new high-power lamp have been integrated. An EUV flux of 9 W into p-sr and a 2 percent bandwidth has been generated in burst mode at 1000 Hz. Three additional parametric studies are discussed. The first compares the EUV power generation and spectral output for three different capillary materials. The second study compares the source efficiency for 3 mm and 6 mm length capillaries. And the third parametric study measures the EUV output stability over a one million pulse run. The second focus area has been to increase mirror reflectance lifetimes through the further development of the gas curtain debris mitigation approach. A new gas curtain laboratory has been built with more than a 10x increase in flow capability and a 10x reduction in chamber background pressure. Measurements of the gas curtain efficiency have demonstrated a reduction in particulate deposition rate of at least a factor of eighty.
IDEAL has been proposed as a new double exposure technique to realize k1 equals 0.3 optical lithography. We have applied this technique to complicated 2D structures that can be found in a poly-level of a memory test pattern device. Experimental results showed that IDEAL has a quite large process window also on structured substrate such as SiN and poly-silicon. For the CD target of 0.13 micrometers , exposure latitude larger than 10 percent with a depth of focus larger than 0.5 micrometers was achieved by IDEAL exposure. The alignment latitude of the two reticles used to compose the final lithographic image was larger than +/- 40 nm, moreover line-end shortening effects are also improved by IDEAL exposure.
Optical proximity correction is one of the major hurdles chip manufacturing has to overcome. The paper presents evaluation results of CAPROX OPC, a rule based OPC software. Mask making influences as well as production requirements are discussed. Rule generation, one of the most critical parts in a rule based correction scheme is discussed. Two different applications are presented.
A hierarchical rule based optical proximity effect correction approach is presented. The approach has been driven by maskmaking and production requirements to make OPC a practical problem solution. The model based rule generation is presented, as well as benchmark tests on different state-of- the-art test chips.
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