Electronic design automation (EDA) is a category of software tools for designing electronic systems such as printed circuit boards and integrated circuits.
Cadence is the most widely used , and the most professional, software for IC layout designing, however there are many other tools like mentor graphics tool, tanner, and also other open source tools like glade, and electric.
There are many tools. Professionally I have used cadence for 3 years which has good market share. Others include mentor graphics' IC station and there was a free layout tool called Laker but it is now a synopsys tool.
Cadence is the industry standard commercial tool for IC design.
ELECTRIC VLSI DESIGN SYSTEM is an opensource tool that gives a similar experience and can be used for academic purposes. Nevertheless, it has been used to get IC manufactured for older technology nodes.
Moreover, you can get very good help resources for ELECTRIC at CMOSedu.com
Apart from Cadence and Synopsys, there is Tanner EDA tool with its L-edit (layout editor). Tanner has been acquired by Mentor Graphics in 2015, later by Siemnes (2019?) so both EDA providers merged their tools. Now you can use L-edit from Tanner and complete the layout verification by Calibre, so both tool worlds are merged and interoperable. Mentor provides also a high-end digital P&R tool called Olympus SoC. Tanner L-edit can be run under Linux and Windows OS, as node-licence or as network-licence. https://www.mentor.com/products/ic_nanometer_design/custom-ic-design/
There is an affordable EDA tool for layout of VLSI chips (ASICs) as well as MEMS and can be used for writing also the photo masks. Windows-based. The tools provider JUSPERTOR is located in south Munich, Germany and attends regularly DAC design automation conference. https://layouteditor.com/ https://www.juspertor.com/ Other layout tools are: Magic Layout (Linux based): http://opencircuitdesign.com/magic/ Klayout (Windows and Linux OS based) from Germany https://www.klayout.de/
In case you want to custom design an IC, Cadence is definitely the No.1 choice. However, in case you want to implement large digital circuits, Synopsys can be helpful too.