he used benday dots

Yes, the dots that Roy Lichtenstein uses are his signature mark and are called 'Benday Dots'.

The dots commonly seen in pop art are called "benday dots." These dots are used to create shading and tone in a printed image, and were popularized by artists like Roy Lichtenstein. Benday dots are named after illustrator and inventor Benjamin Henry Day Jr., who patented the process in 1879.

It cannot be said with any certainty who was first. The most famous user of Benday dots was Roy Lichtenstein.

ben-day dots , primary colors , and comic strips