Amazon will raise $15 billion from its first U.S. dollar bond offering in three years, according to a filing with the Securities and Exchange Commission on Monday, as big tech firms ramp up investments in AI infrastructure.

Big technology firms are turning to debt sales worth tens of billions of dollars to fund infrastructure expansions as demand for artificial intelligence workloads surges.

The e-commerce giant filed for a six-part bond sale earlier on Monday. Proceeds may be used for everything, from acquisitions and capital expenditures to share buybacks.

At the peak, the bond attracted about $80 billion of demand, according to Bloomberg News, which first reported the development.

Pricing discussions for the longest portion of the deal, a 40-year bond, tightened to 0.85 percentage point above Treasuries, from 1.15 percentage point initially, the report said.

Last month, Meta Platforms announced its biggest bond sale of up to $30 billion, while cloud infrastructure and software maker Oracle is also reportedly looking to raise $15 billion in bond sales.

Major tech firms, including Meta, Amazon and Alphabet, are expected to spend $400 billion on AI infrastructure this year, according to Morgan Stanley estimates.

Amazon has been spending more on AI, with its capital expenditure expected to total around $125 billion this year and more the year after. It recently announced a $38 billion deal with OpenAI, giving a major lift to its cloud unit after losing ground to Microsoft and Google.