Peter Carstairs is one of three finalists in the Doritos Super Bowl commercial competition, which will see the winner's 30-second ad aired during the Super Bowl 50 on Sunday (Pacific Time Zone).

The 45-year-old from Melbourne has some tough competition vying to win their chance to 'Crash the Super Bowl'.

The prize up for grabs is $US1 million in cash and a chance to work with Hollywood blockbuster director Zack Snyder.

His entry was inspired by a trip to the hospital with his then-pregnant wife, Australian actress Sibylla Budd.

The ad - which cost him $US2000 to make - features an unborn baby who can't get enough of Doritos chips during an ultrasound.

Carstairs' creation is up against two ads from Los Angeles-based filmmakers.

One follows a posse of resourceful dogs as they try to outsmart a grocery store manager that cost 29-year-old Jacob Chase $US1000 to make.

The other follows a Tinder-inspired string of awkward first dates. Filmmaker David Rudy, 42, spent $US4500 on the ad, which features Everybody Loves Raymond actress Doris Roberts and Jurassic World's Kelly Washington.

The competition promises the winner unprecedented exposure, with last year's Super Bowl watched by 114.4 million viewers in the US alone.

It's also big business for advertisers.

A commercial spot during the game costs up to $US5 million, according to Fortune,  with brands spending big bucks on slick productions featuring  superstar celebrities.

The ads, or ad-teasers, released online in the lead-up to the main event also attract hundreds of thousands of eyeballs.

"I was a commercial director for quite a long time and if I had said 'I have a spot playing in the Super Bowl', it was kind of like the 'king-daddy' to show your spots," Snyder said in a promotional video published on Doritos' competition website.

Online voting has now closed, and Carstairs won't find out if he has won until the ad airs during the game on Monday (AEST).

Peter Carstairs beat more than 4000 entries with his Melbourne-made Doritos commercial.

The competition gained considerable heft since it launched in 2006, when it called on filmmakers to submit videos "on spec", or without pay, and awarded the five finalists $US10,000 each.

Ten years on, 'Crash the Super Bowl' has become a big-budget media campaign.

Critics of the campaign claim Doritos is taking advantage of desperate filmmakers looking for a break, who spend thousands of dollars on their entries for a shot at the prize, with US tech and culture news site The Verge calling the competition "truly tasteless".

"Doritos no longer bothers to conceal how its promotion has abandoned the initial premise of being an opportunity for amateur filmmakers and fans of the snack food," wrote The Verge senior editor Chris Plante on Wednesday,

"The hopeful upstarts cut along the way gambled time and money on a rigged table," he said.