Novel Gray-scale, Hard Photoresist – How Does It Work?

Novel Gray-scale, Hard Photoresist – How Does It Work? A. Kovalskyy, M. Vlcek, A. Ganjoo, S. Khalid*, H. Jain Lehigh University, PA; *Brookhaven National Laboratory We have developed novel gray-scale, hard inorganic photoresists for dry etching, based on gradual silver photodissolution in chalcogenide glass (ChG) thin films. These materials are perfect for creating high- quality ultrathin submicron-scale gray profiles, and can be especially useful for numerous MEMS applications (e.g. microturbines for power generation, microengines, ultrathin Fresnel lenses, etc.) and other microelectronic technologies. In spite of a number of experiments the mechanism of silver photo-dissolution remained unclear. EXAFS and XANES measurements in combination with high-resolution XPS have allowed us to observe the kinetics of dissolution process, and identify the products of dissolution as a function of silver concentration and irradiation conditions. We find that irradiation in vacuum leads to the formation of covalently bonded amorphous ternary, while irradiation in air causes formation of intermediate surface arsenic oxide layer, which is responsible for metallic + ionic bonding of silver atoms in the matrix. These studies have significant importance for industrial implementation of these unique lithographic materials as well as for a fundamental understanding of photoinduced chemical The dissolution of silver in ChG thin films subjected to light, electron, or x-ray irradiation significantly changes its chemical resistance because of the gradual change of chemical composition. Grayscale photolithography in ChG is based on the fact that both the exposure time and the light intensity affect the etching rate. Dissolution of silver to different depths depends on the total dose of irradiation as determined by the intensity and time of irradiation. The selectivity of etching defined as the etching rate ratio of exposed and unexposed regions of a sample is a function of glass film composition, its prehistory, as well as the composition of etching gas. A. Kovalskiy, A. Ganjoo, S. Khalid, H. Jain "Combined high-resolution XPS and EXAFS study of Ag photodissolution in a-As 2 S 3 thin ﬁlm“, J. non-Cryst. Solids (2010), doi: 10.1016/j.jnoncrysol.2010.02.021). Work performed on beamlines X18B and X19A. As-S As-S ≈AgAsS 2 Ag X18B-X19A

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X18B-X19A. Novel Gray-scale, Hard Photoresist – How Does It Work?. A. Kovalskyy, M. Vlcek, A. Ganjoo, S. Khalid*, H. Jain Lehigh University, PA; *Brookhaven National Laboratory. - PowerPoint PPT Presentation

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Page 1: Novel Gray-scale, Hard Photoresist – How Does It Work?

Novel Gray-scale, Hard Photoresist – How Does It Work?A. Kovalskyy, M. Vlcek, A. Ganjoo, S. Khalid*, H. JainLehigh University, PA; *Brookhaven National Laboratory

We have developed novel gray-scale, hard inorganic photoresists for dry etching, based on gradual silver photodissolution in chalcogenide

glass (ChG) thin films. These materials are perfect for creating high-quality ultrathin submicron-scale gray profiles, and can be especially useful for numerous MEMS applications (e.g. microturbines for power generation, microengines, ultrathin Fresnel lenses, etc.) and other microelectronic technologies. In spite of a number of experiments the mechanism of silver photo-dissolution remained unclear.

EXAFS and XANES measurements in combination with high-resolution XPS have allowed us to observe the kinetics of dissolution process, and identify the products of dissolution as a function of silver concentration and irradiation conditions. We find that irradiation in vacuum leads to the formation of covalently bonded amorphous ternary, while irradiation in air causes formation of intermediate surface arsenic oxide layer, which is responsible for metallic + ionic bonding of silver atoms in the matrix.

These studies have significant importance for industrial implementation of these unique lithographic materials as well as for a fundamental understanding of photoinduced chemical transformations in amorphous solids.

The dissolution of silver in ChG thin films subjected to light, electron, or x-ray irradiation significantly changes its chemical resistance because of the gradual change of chemical composition. Grayscale photolithography in ChG is based on the fact that both the exposure time and the light intensity affect the etching rate. Dissolution of silver to different depths depends on the total dose of irradiation as determined by the intensity and time of irradiation. The selectivity of etching defined as the etching rate ratio of exposed and unexposed regions of a sample is a function of glass film composition, its prehistory, as well as the composition of etching gas.

A. Kovalskiy, A. Ganjoo, S. Khalid, H. Jain "Combined high-resolution XPS and EXAFS study of Ag photodissolution in a-As2S3 thin film“, J. non-Cryst. Solids (2010), doi: 10.1016/j.jnoncrysol.2010.02.021).

Work performed on beamlines X18B and X19A.

As-SAs-S

≈AgAsS2Ag

X18B-X19A