The AI boom continues to heat up! Sierra, founded by the chairman of OpenAI's board, is valued nearly five times in less than a year.

Sierra Technologies, an artificial intelligence startup founded by OpenAI board chairman Bret Taylor and former Alphabet Inc. executive Clay Bavor, raised $175 million in a funding round that values the company at $4.5 billion. The deal represents a significant jump in the company's valuation, which was near $1 billion earlier this year.

Taylor, who was co-CEO of Salesforce.com Inc., said in an interview Monday that while the funding environment in the industry appeared to be "foamy," the prospects for AI justified the spending.

"In hindsight, it makes sense," he said, comparing the best companies in the industry to internet-era giants like Alphabet's Google. But he also warned that the industry was also full of "a lot of snake oil," suggesting there were still a lot of exaggerations or misrepresentations.

Sierra develops AI customer service tools for brands like ADT Inc., a home security company, and Casper Sleep Inc., a mattress company. A spokesperson said the funding round was led by Greenoaks Capital Partners and included Thrive Capital, Iconiq Capital and existing investors.