Maintaining low-defect spin-applied films is paramount to the success of semiconductor manufacturing.
While some spin-on films have a low number of defects as coated, defect levels can rise with the number of
wafers processed. Thin organic films may outgas or sublime during the post-coat baking process, or even
during subsequent exposures to deep or extreme ultraviolet radiation. If these outgassing components
collect on the lid of the hot plate chamber, there is an increased risk of "fall-on" defects on subsequently
processed wafers. To increase throughput, preventive maintenance and cleaning schedules are pushed to
the limit to provide maximum output from the track. New materials must be designed to produce minimal
outgassing to ensure maximum throughput without defects. Early tests for measuring outgassing provided
qualitative results gained from collecting the condensed outgassing components on a quartz wafer and
measuring the absorbance of the resulting film. A more advanced technique involves the use of a newly
designed quartz crystal microbalance (QCM) to more carefully quantify the amount of outgassing. As the
industry continues to mature, more sensitive measurements are required to design new materials with even
lower outgassing from sublimation. The inverted wafer test and the QCM techniques provide
complementary information about outgassing and together provide a better overall prediction of the defectforming
potential than either technique alone.
The 45-nm node will require the use of thinner photoresists, which necessitates the use of multilayer pattern transfer
schemes. One common multilayer approach is the use of a silicon-rich anti-reflective hardmask (Si BARC) with a
carbon-rich pattern transfer underlayer (spin-on carbon, or SOC). The combination of the two layers provides a highly
planar platform for a thin resist, and provides a route to etch substrates due to the alternating plasma etch selectivities of
the organic resist, inorganic Si BARC, and organic SOC. Yet such schemes will need to be optimized both for pattern
transfer and optics. Optimizing optics under hyper-NA immersion conditions is more complicated than with standard
(that is, NA<1) lithography. A rigorous calculation technique is used to evaluate and compare standard lithography to a
hyper-NA case using a multilayer stack. An example of such a stack is shown to have reasonable lithographic
The 65nm half pitch node will require 193nm wavelength in combination with NA > 0.9 to keep k1 above 0.3. With such high angles of diffracted light the relative amount of TE (or s) polarization that contributes to image formation increases. Unfortunately, the swing curve for TE polarization is higher than normal for traditional BARC materials. This study explores new advanced bottom anti-reflective coating (BARC) materials dedicated to ultra-high NA imaging. The improvements in imaging performance over traditional BARCs are shown through simulations and experimental results with the latest high NA TWINSCAN XT:1400 exposure systems. Simulations will show the relation between various BARC and top anti-reflective coating (TARC) material approaches and high NA imaging performance. This was done, among other things, as function of illumination settings. These simulations are accompanied by experimental results with the different suggested BARC strategies as multi-layer BARCs and tunable reflective index materials. Initial experiments were done on the TWINSCAN XT:1250 with 0.85NA. After analyzing these results, further tests were done on the TWINSCAN XT:1400 NA=0.93 exposure system. These results verify the feasibility of the newly developed BARC materials.
As the semiconductor industry constantly increases the information density and the speed of integrated circuits, the control over the shrinking critical dimension (CD) becomes increasingly important. Soon the current 248 nm exposure tools will be insufficient to meet the needs of the shrinking CD. Shorter wavelengths, such as 193 nm, will be required to progress to smaller feature size. However decreasing the exposure wavelength makes the control of the feature size even more difficult, due in part to a sharp increase in substrate reflectivity with decreasing wavelength. Controlling this reflectivity through the use of bottom antireflective coatings (BARCs) will play an important role in the success of upcoming lithographic technologies. While there are successful spindon organic BARCs for 193 nm lithography, continuing improvements in resist and process technology demand continuing improvements in BARCs. Described herein are the chemistry, methods, and performance of a highly versatile polymer for use as a future generation 193 nm spin-on thin film organic BARC. The versatility of the polymer functionality allows for cross-linking while baking by either a strong acid catalyzed thermal reaction without an additional cross-linking molecule, or an uncatalyzed thermal reaction with a cross-linker, both without off gassing. Attachment of a variety of chromophores is easily accomplished by a thermal reaction either to the polymer in solution or while on the wafer during baking. The versatility of having one polymer with functionality that allows for multiple modes of cross-linking, varied choice of chromophore, and method of chromophore attachment, provides a platform that can be easily tailored to meet the needs of the emerging 193 nm technology.