Sec Form 4 Filing - Redinbo Greg @ AXCELIS TECHNOLOGIES INC - 2025-02-28

FORM 4 Check this box if no longer subject to Section 16. Form 4 or Form 5 obligations may continue. See Instruction 1(b).

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 STATEMENT OF CHANGES IN BENEFICIAL OWNERSHIP Filed pursuant to Section 16(a) of the Securities Exchange Act of 1934, Section 17(a) of the Public Utility Holding Company Act of 1935 or Section 30(h) of the Investment Company Act of 1940

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1. Name and Address of Reporting Person Redinbo Greg 2. Issuer Name and Ticker or Trading Symbol AXCELIS TECHNOLOGIES INC [ ACLS] 5. Relationship of Reporting Person(s) to Issuer (Check all applicable) _____ Director _____ 10% Owner X __ Officer (give title below) _____ Other (specify below) EVP MARKETING AND APPLICATIONS (Last) (First) (Middle) C/O AXCELIS TECHNOLOGIES, INC., 108 CHERRY HILL DRIVE 3. Date of Earliest Transaction (MM/DD/YY) 02/28/2025 (Street) BEVERLY, MA01915 4. If Amendment, Date Original Filed (MM/DD/YY) 6. Individual or Joint/Group Filing (Check Applicable Line) __ X __ Form filed by One Reporting Person _____ Form filed by More than One Reporting Person (City) (State) (Zip)

Table I - Non-Derivative Securities Acquired, Disposed of, or Beneficially Owned 1.Title of Security (Instr. 3) 2. Transaction Date (MM/DD/YY) 2A. Deemed Execution Date, if any (MM/DD/YY) 3. Transaction Code (Instr. 8) 4. Securities Acquired (A) or Disposed of (D) (Instr. 3, 4 and 5) 5. Amount of Securities Beneficially Owned Following Reported Transaction(s) (Instr. 3 and 4) 6. Ownership Form: Direct (D) or Indirect (I) (Instr. 4) 7. Nature of Indirect Beneficial Ownership (Instr. 4) Code V Amount (A) or (D) Price Common Stock 02/28/2025 F( 1 ) 471 D $ 54.79 ( 2 ) 22,632 ( 3 ) D Common Stock 02/28/2025 F( 4 ) 749 D $ 54.79 ( 2 ) 21,883 ( 5 ) D

Amount or Number of Shares Table II - Derivative Securities Acquired, Disposed of, or Beneficially Owned ( e.g. , puts, calls, warrants, options, convertible securities) 1. Title of Derivative Security (Instr. 3) 2. Conversion or Exercise Price of Derivative Security 3. Transaction Date (MM/DD/YY) 3A. Deemed Execution Date, if any (MM/DD/YY) 4. Transaction Code (Instr. 8) 5. Number of Derivative Securities Acquired (A) or Disposed of (D) (Instr. 3, 4, and 5) 6. Date Exercisable and Expiration Date (MM/DD/YY) 7. Title and Amount of Underlying Securities (Instr. 3 and 4) 8. Price of Derivative Security (Instr. 5) 9. Number of Derivative Securities Beneficially Owned Following Reported Transaction(s) (Instr. 4) 10. Ownership Form of Derivative Security: Direct (D) or Indirect (I) (Instr. 4) 11. Nature of Indirect Beneficial Ownership (Instr. 4) Code V (A) (D) Date Exercisable Expiration Date Title

Reporting Owners Reporting Owner Name / Address Relationships Director 10% Owner Officer Other Redinbo Greg C/O AXCELIS TECHNOLOGIES, INC. 108 CHERRY HILL DRIVE BEVERLY, MA01915 EVP MARKETING AND APPLICATIONS Signatures /s/ Lynnette C. Fallon, Attorney-in-Fact 03/04/2025 Signature of Reporting Person Date

Explanation of Responses:

( 1 )This forfeiture of shares for tax withholding purposes relates to the vesting on February 28, 2025 of performance based restricted stock units ("2023 PRSUs") granted to the executive in May 2023. The units vesting on the 2023 PRSUs were deemed earned by the Compensation Committee in February 2024, and the shares vesting on February 28, 2025 represent the final tranche of that grant. As agreed with the executive, the shares issued to the executive on the vesting were reduced by a number of shares having a value equal to the executive's tax withholding obligation with respect to the vested 2023 PRSUs. ( 2 )Represents the closing price of the Company's common stock on February 28, 2025, the date of the tax withholding. ( 3 )Of the shares held as of February 28, 2025 after the vesting of the 2023 PRSUs, 14,123 were issuable on vesting of restricted stock units granted to the reporting person under the 2012 Equity Incentive Plan and are subject to forfeiture. ( 4 )This forfeiture of shares for tax withholding purposes relates to the vesting on February 28, 2025 of performance based restricted stock units ("2024 PRSUs") granted to the executive in May 2024. Of the 2024 PRSUs granted, 150% were determined to be earned by the executive pursuant to a resolution of the Axcelis Technologies, Inc. Compensation Committee on February 13, 2025, and half of the earned shares vested on February 28, 2025. As agreed with the executive, the shares issued to the executive on the vesting were reduced by a number of shares having a value equal to the executive's tax withholding obligation with respect to the vested 2024 PRSUs. ( 5 )Of the shares held as of February 28, 2025 after the vesting of the 2024 PRSUs, 11,985 were issuable on vesting of restricted stock units granted to the reporting person under the 2012 Equity Incentive Plan and are subject to forfeiture.

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