Axcelis (ACLS) 10-K 2010 FY Annual report

QuickLinks -- Click here to rapidly navigate through this document

Exhibit 21.1

Axcelis Technologies, Inc.
Exhibit 21.1 to Form 10-K for the year ended December 31, 2010
Subsidiaries

        The following is a list of all direct and indirect wholly-owned subsidiaries of Axcelis Technologies, Inc. as of the date hereof:

Domestic Subsidiaries

1.

Axcelis Technologies CCS Corporation a Delaware corporation

2.

Fusion Technology International, Inc., a Delaware corporation

3.

Axcelis Technologies (Israel), Inc., a Delaware corporation

4.

Fusion Investments, Inc., a Maryland corporation

5.

High Temperature Engineering Corporation, a Delaware corporation

European Subsidiaries

6.

Axcelis Technologies, GmbH (Germany)

7.

Axcelis Technologies, S.r.l (Italy)

8.

Axcelis Technologies, Sarl (France)

9.

Axcelis Technologies, Ltd. (U.K.)

Asian Subsidiaries

10.

Axcelis Technologies, KK (Japan)

11.

Axcelis Technologies Limited (Korea)

12.

Axcelis Technologies Ltd. (Taiwan)

13.

Axcelis Technologies Pte. Ltd. (Singapore)

14.

Axcelis Technologies Semiconductor Trading (Shanghai) Co., Ltd. (Peoples Republic of China)

QuickLinks

Exhibit 21.1

Axcelis Technologies, Inc. Exhibit 21.1 to Form 10-K for the year ended December 31, 2010 Subsidiaries