The field of plasma etching is reviewed. Plasma etching, a revolutionary extension of the technique of physical sputtering, was introduced to integrated circuit manufacturing as early as the mid 1960s and more widely in the early 1970s, in an effort to reduce liquid waste disposal in manufacturing and achieve selectivities that were difficult to obtain with wet chemistry. Quickly, the ability to anisotropically etch silicon, aluminum, and silicon dioxide in plasmas became the breakthrough that allowed the features in integrated circuits to continue to shrink over the next 40 years. Some of this early history is reviewed, and a discussion of the evolution in plasma reactor design is included. Some basic principles related to plasma etching such as evaporation rates and Langmuir–Hinshelwood adsorption are introduced. Etching mechanisms of selected materials, silicon, silicon dioxide, and low dielectric-constant materials are discussed in detail. A detailed treatment is presented of applications in current silicon integrated circuit fabrication. Finally, some predictions are offered for future needs and advances in plasma etching for silicon and nonsilicon-based devices.

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Plasma etching: Yesterday, today, and tomorrow

This critical review focuses on the solution deposition of transparent conductors with a particular focus on transparent conducting oxide (TCO) thin-films TCOs play a critical role in many current and emerging opto-electronic devices due to their unique combination of electronic conductivity and transparency in the visible region of the spectrum Atmospheric-pressure solution processing is an attractive alternative to conventional vacuum-based deposition methods due to its ease of fabrication, scalability, and potential to lower device manufacturing costs An introduction into the applications of and material criteria for TCOs will be presented first, followed by a discussion of solution routes to these systems Recent studies in the field will be reviewed according to their materials system Finally, the challenges and opportunities for further enabling research will be discussed in terms of emerging oxide systems and non-oxide based transparent conductors (341 references)

Solution processing of transparent conductors: from flask to film

Substrate processing systems are described that have a capacitively coupled plasma (CCP) unit positioned inside a process chamber. The CCP unit may include a plasma excitation region formed between a first electrode and a second electrode. The first electrode may include a first plurality of openings to permit a first gas to enter the plasma excitation region, and the second electrode may include a second plurality of openings to permit an activated gas to exit the plasma excitation region. The system may further include a gas inlet for supplying the first gas to the first electrode of the CCP unit, and a pedestal that is operable to support a substrate. The pedestal is positioned below a gas reaction region into which the activated gas travels from the CCP unit.

Semiconductor processing system and methods using capacitively coupled plasma

An exemplary system may include a chamber configured to contain a semiconductor substrate in a processing region of the chamber. The system may include a first remote plasma unit fluidly coupled with a first access of the chamber and configured to deliver a first precursor into the chamber through the first access. The system may still further include a second remote plasma unit fluidly coupled with a second access of the chamber and configured to deliver a second precursor into the chamber through the second access. The first and second access may be fluidly coupled with a mixing region of the chamber that is separate from and fluidly coupled with the processing region of the chamber. The mixing region may be configured to allow the first and second precursors to interact with each other externally from the processing region of the chamber.

Semiconductor processing systems having multiple plasma configurations

A method of selectively etching a metal-containing film from a substrate comprising a metal-containing layer and a silicon oxide layer includes flowing a fluorine-containing gas into a plasma generation region of a substrate processing chamber, and applying energy to the fluorine-containing gas to generate a plasma in the plasma generation region. The plasma comprises fluorine radicals and fluorine ions. The method also includes filtering the plasma to provide a reactive gas having a higher concentration of fluorine radicals than fluorine ions, and flowing the reactive gas into a gas reaction region of the substrate processing chamber. The method also includes exposing the substrate to the reactive gas in the gas reaction region of the substrate processing chamber. The reactive gas etches the metal-containing layer at a higher etch rate than the reactive gas etches the silicon oxide layer.

Methods for etch of metal and metal-oxide films

Solution processible hardmasks are described that can be formed from aqueous precursor solutions comprising polyoxometal clusters and anions, such as polyatomic anions. The solution processible metal oxide layers are generally placed under relatively thin etch resist layers to provide desired etch contrast with underlying substrates and/or antireflective properties. In some embodiments, the metal oxide hardmasks can be used along with an additional hardmask and/or antireflective layers. The metal oxide hardmasks can be etched with wet or dry etching. Desirable processing improvements can be obtained with the solution processible hardmasks.

Solution processible hardmasks for high resolution lithography

High resolution, high sensitivity inorganic resists

The dynamic absorption coefficients of several chemically amplified resists (CAR) and non-CAR extreme ultraviolet (EUV) photoresists are measured experimentally using a specifically developed setup in transmission mode at the x-ray interference lithography beamline of the Swiss Light Source. The absorption coefficient α and the Dill parameters ABC were measured with unprecedented accuracy. In general, the α of resists match very closely with the theoretical value calculated from elemental densities and absorption coefficients, whereas exceptions are observed. In addition, through the direct measurements of the absorption coefficients and dose-to-clear values, we introduce a new figure of merit called chemical sensitivity to account for all the postabsorption chemical reaction ongoing in the resist, which also predicts a quantitative clearing volume and clearing radius, due to the photon absorption in the resist. These parameters may help provide deeper insight into the underlying mechanisms of the EUV concepts of clearing volume and clearing radius, which are then defined and quantitatively calculated.

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Dynamic absorption coefficients of chemically amplified resists and nonchemically amplified resists at extreme ultraviolet

This paper describes a metal oxide patternable hardmask designed for EUV lithography. The material has imaged 15-nm
half-pitch by projection EUV exposure on the SEMATECH Berkeley MET, and 12-nm half-pitch by electron beam
exposure. The platform is highly absorbing (16 μm-1) and etch resistant (>100:1 for silicon). These properties enable
resist film thickness to be reduced to 20nm, thereby reducing aspect ratio and susceptibility to pattern collapse. New
materials and processes show a path to improved photospeed. This paper also presents data for on coating uniformity,
metal-impurity content, outgassing, pattern transfer, and resist strip.

Directly patterned inorganic hardmask for EUV lithography

Inpria is developing directly patternable, metal oxide hardmasks as robust, high-resolution photoresists for EUV lithography Targeted formulations have achieved 13nm half-pitch at 35 mJ/cm2 on an ASML’s NXE:3300B scanner Inpria’s second-generation materials have an absorbance of 20/μm, thereby enabling an equivalent photon shot noise compared to conventional resists at a dose lower by a factor of 4X These photoresists have ~40:1 etch selectivity into a typical carbon underlayer, so ultrathin 20nm films are possible, mitigating pattern collapse In addition to lithographic performance, we review progress in parallel advances required to enable the transition from lab to fab for such a metal oxide photoresist This includes considerations and data related to: solvent compatibility, metals cross-contamination, coat uniformity, stability, outgassing, and rework

Jason K. Stowers

Papers

Solution processible hardmasks for high resolution lithography

High resolution, high sensitivity inorganic resists

Dynamic absorption coefficients of chemically amplified resists and nonchemically amplified resists at extreme ultraviolet

Directly patterned inorganic hardmask for EUV lithography

Integrated fab process for metal oxide EUV photoresist