Thank you for your question.  Lawn scarification, also known as dethatching, is the process of removing excess thatch from  lawn using a vertical mower that leaves shallow slits in the soil.  Some thatch (<1/2") is good, but thatch over 1" should be removed.  Fall (early Sept.) is the best time of year to dethatch because the turf has time to recover before going dormant and there is less pressure from weeds.  More info in the attached links:
Core Aeration & Dethatching of Lawns-MSU
How to Control Thatch in the Lawn-UMN - how to measure the thatch layer...
Managing Thatch in Lawns-PSU
Core aeration is an alternative way to reduce thatch that is not as damaging to the turf.  You can also thicken your lawn by seeding and/or spreading a layer of compost on the lawn after core aerating.  More info here:
Core Aeration of Lawns-Iowa St
Core Aeration of Lawns-MSU
Core Aeration of lawns-Illinois
I would also recommend doing a soil test to determine the soil fertility this spring. Knowing the type and fertility (pH, macro-nutrient levels, CEC, etc.) of your soil is the starting point to establishing & maintaining a strong/thick turf that can resist diseases, weeds, moss and insects/grubs and look great without wasting material or $. More info here: Don't Guess-Soil Test-MSU and MSU Home Soil Test-self mailer Soil test results will identify any fertility concerns that you can work to correct, to improve turf health (it’s a well spent $26). Your report will provide recommendations to correct any deficiencies found, fertilizer type and a fertilization schedule (amount and timing) based on your preferred maintenance level (high, moderate or low).