Shares in AMS fell by 11% on Wednesday following news the sensor maker, best known as a supplier to Apple, was seeking approval for a capital raise.
AMS supplies sensors for Apple face recognition technology on iPhones and is in the process of buying Osram, the leading manufacturer of car headlamps, for up to $5 billion(4.06 billion pounds) as it seeks a new sales outlet in the auto industry.
Its shares have lost nearly half their value this year as investors worry about the impact of the coronavirus pandemic and the company's level of debt.
After an earlier 11% fall, the Zurich-listed shares were down 9.9% at 12.80 Swiss francs at 1415 GMT and were the biggest decliner in the sector <.SX8P>.
To refund a 4.4 billion euro ($4.8 billion) bridge loan, provided by UBS, HSBC and Bank of America Merrill Lynch for the Osram deal, ASM had already issued 190 million new shares for 1.75 billion Swiss francs (1.7 billion euros).
Now it is seeking shareholder approval to issue convertible notes, profit participation bonds or profit participation rights that could translate into 27.4 million new shares, the invitation to its June 3 shareholders meeting said.
That would deliver only 390 million francs according to Tuesday's closing price, but further dilute the shares.
A spokesman for the Austrian company said the capital raise was not directly linked to the Osram takeover and the company had carried out comparable action before.
(Reporting by Kirsti Knolle; Editing by Alison Williams and Barbara Lewis)