UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

FORM 8-K

CURRENT REPORT

PURSUANT TO SECTION 13 OR 15(d)

OF THE SECURITIES EXCHANGE ACT OF 1934

Date of Report (Date of earliest event reported)

April 30, 2014

ENTEGRIS, INC.

(Exact name of registrant as specified in charter)

129 Concord Road

Billerica, MA 01821

(Address of Principal Executive Offices, including Zip Code)

(978) 436-6500

(Registrant’s telephone number, including area code)

Check the appropriate box below if the Form 8-K filing is intended to simultaneously satisfy the filing obligation of the registrant under any of the following provisions:

Item 1.01 Entry into a Material Definitive Agreement

On April 30, 2014, in connection with the Merger (as defined below), Entegris, Inc. (the “Company”) entered into an asset-based credit agreement with Goldman Sachs Bank USA, as administrative agent, collateral agent, sole lead arranger, sole bookrunner and sole syndication agent (the “ABL Facility”), that provides senior secured financing of $75.0 million (which may be increased by up to $35.0 million in certain circumstances), subject to a borrowing base limitation. The borrowing base for the ABL Facility at any time equals the sum of: (i) 90% of certain eligible accounts; plus, (ii) the lesser of (A) 60% of the inventory value of certain eligible inventory or (B) 90% of the net recovery percentage of certain eligible inventory; plus, (iii) 90% of the net recovery percentage of certain work-in-progress inventory in an amount not to exceed $5.0 million at any time; minus (iv) inventory reserves. The ABL Facility includes borrowing capacity in the form of letters of credit up to the entire amount of the facility, and up to $20 million in U.S. dollars for borrowings on same-day notice, referred to as swingline loans, and is available in U.S. dollars.

Interest Rate and Fees. Borrowings under the ABL Facility bear interest at a rate per annum equal to, at the Company’s option, any of the following, plus, in each case, an applicable margin: (a) a base rate determined by reference to the highest of (1) the prime rate quoted in the print edition of The Wall Street Journal, Money Rates Section, (2) the federal funds effective rate plus 0.50% and (3) a LIBOR rate determined by reference to the costs of funds for U.S. dollar deposits for an interest period of one month adjusted for certain additional costs, plus 1.00%; and (b) a LIBOR rate determined by reference to the costs of funds for the interest period relevant to such borrowing adjusted for certain additional costs. The initial applicable margin for borrowings under the ABL Facility is 1.00% with respect to base rate borrowings and 2.00% with respect to LIBOR borrowings. Commencing with the completion of the first fiscal quarter ending after the closing of the ABL Facility, the applicable margin for borrowings thereunder is subject to adjustment each fiscal quarter, based on the average historical excess availability during the preceding quarter. Swingline loans shall bear interest at a rate per annum equal to the base rate plus the applicable margin.

In addition to paying interest on outstanding principal under the ABL Facility, the Company is required to pay a commitment fee in respect of the unutilized commitments thereunder. The initial commitment fee is 0.33% per annum. Commencing with the completion of the first fiscal quarter ending after the closing of the ABL Facility, the commitment fee is subject to adjustment based on the amount of average unutilized commitments for the three-month period immediately preceding such adjustment date. The Company must also pay customary letter of credit fees and agency fees.

Mandatory Prepayments. If at any time the aggregate amount of outstanding loans, unreimbursed letter of credit drawings and undrawn letters of credit under the ABL Facility exceeds the lesser of (a) the commitment amount and (b) the borrowing base, the Company is required to repay outstanding loans and/or cash collateralize letters of credit, with no reduction of the commitment amount. During any period that the amount available under the ABL Facility is less than 10.0% of the lesser of (1) the commitment amount and (2) the borrowing base, until the time when the Company has excess availability greater than 10.0% of the lesser of (1) the commitment amount and (2) the borrowing base, in each case, for 30 consecutive calendar days, or during the continuance of certain events of default, including a payment or bankruptcy event of default, failure to comply with certain covenants relating to the bank accounts holding the Company’s cash or a breach of a representation or warranty made in any borrowing base certificate, the Company is required to repay outstanding loans and/or cash collateralize letters of credit with the cash that it is required to deposit daily in a collection account maintained with the administrative agent under the ABL Facility.

Voluntary Prepayments. The Company may voluntarily reduce the unutilized portion of the commitment amount and repay outstanding loans at any time. Prepayments of the loans may be made without premium or penalty other than customary “breakage” costs with respect to LIBOR loans.

Amortization and Final Maturity. There is no scheduled amortization under the Company’s ABL Facility. The principal amount outstanding under the ABL Facility is due and payable in full on the fifth anniversary of the closing date.

Guarantees and Security. All obligations under the ABL Facility are unconditionally guaranteed by certain of the Company’s existing wholly owned domestic subsidiaries and are required to be guaranteed by certain of the Company’s future wholly owned domestic subsidiaries. All obligations under the ABL Facility, and the guarantees of those obligations, are secured, subject to certain exceptions, by substantially all of the Company’s assets and the assets of the Company’s subsidiaries that have guaranteed the ABL Facility (referred to herein as the subsidiary guarantors), including, in each case subject to customary exceptions and exclusions:

Certain Covenants and Events of Default. The ABL Facility contains a number of negative covenants that, among other things and subject to certain exceptions, restrict the Company’s ability and the ability of each of the Company’s subsidiaries to:

The covenant limiting dividends and other restricted payments is expected to permit the restricted actions in an unlimited amount so long as certain restricted payment conditions are satisfied, principally that no event of default exists and that the Company must have pro forma excess availability under the ABL Facility (a) for the 30 day period ending on the payment date, greater than the greater of 15.0% of the lesser of (i) the commitment amount and (ii) the borrowing base, (b) greater than 15% on the payment date and (c) either (i) for the 30 day period ending on the payment date, greater than 17.5% or (ii) a pro forma Fixed Charge Coverage Ratio (as defined in the credit agreement governing the ABL Facility) of at least 1.0 to 1.0. Each of the covenants limiting (1) certain acquisitions, (2) investments, (3) the incurrence of unsecured debt and (4) prepayments or redemptions of certain indebtedness are expected to permit the restricted actions in an unlimited amount so long as certain payment conditions, and other conditions, are satisfied, principally that no event of default exists and that the Company must have pro forma excess availability under the ABL Facility (a) for the 30 day period ending on the payment date, greater than the greater of 12.5% of the lesser of (i) the commitment amount and (ii) the borrowing base, (b) greater than 12.5% on the payment date and (c) either (i) for the 30 day period ending on the payment date, greater than 15.0% or (ii) a pro forma Fixed Charge Coverage Ratio (as defined in the credit agreement governing the ABL Facility) of at least 1.0 to 1.0.

From the time when the Company has excess availability less than the greater of (a) 10.0% of the lesser of (1) the commitment amount and (2) the borrowing base and (b) $7.0 million, until the time when the Company has

excess availability equal to or greater than the greater of (a) 10.0% of the lesser of (1) the commitment amount and (2) the borrowing base and (b) $7.0 million for 30 consecutive days, the credit agreement governing the ABL Facility requires the Company to maintain a Fixed Charge Coverage Ratio tested on the last day of each fiscal quarter of at least 1.0 to 1.0.

The credit agreement governing the ABL Facility additionally contains certain customary representations and warranties, affirmative covenants and provisions relating to events of default.

The foregoing summary of the ABL Facility is not complete and is qualified in its entirety by reference to the credit and guaranty agreement and the pledge and security agreement entered into in connection with the closing of the ABL Facility, copies of which are filed as Exhibits 10.1 and 10.3 to this Current Report on Form 8-K and are incorporated herein by reference.

On April 30, 2014, in connection with the Merger, the Company entered into a term loan credit and guaranty agreement with Goldman Sachs Bank USA, as administrative agent, collateral agent, sole lead arranger, sole bookrunner and sole syndication agent (the “Term Loan Facility”), that provides senior secured financing of $460 million (which may be increased by up to $225.0 million in certain circumstances).

Interest Rate and Fees. Borrowings under the Term Loan Facility bear interest at a rate per annum equal to, at the Company’s option, any of the following, plus, in each case, an applicable margin: (a) a base rate determined by reference to the highest of (1) the prime rate quoted in the print edition of The Wall Street Journal, Money Rates Section (2) the federal funds effective rate plus 0.50% and (3) a LIBOR rate determined by reference to the costs of funds for U.S. dollar deposits for an interest period of one month adjusted for certain additional costs, plus 1.00%; and (b) a LIBOR rate determined by reference to the costs of funds for the interest period relevant to such borrowing adjusted for certain additional costs, subject to a LIBOR rate floor of 0.75% per annum. The applicable margin for borrowings under the Term Loan Facility is 1.75% with respect to base rate borrowings and 2.75% with respect to LIBOR borrowings.

In addition to paying interest on outstanding principal under the Term Loan Facility, the Company will pay customary agency fees.

Mandatory Prepayments. The credit agreement governing the Term Loan Facility requires the Company to prepay outstanding term loans, subject to certain exceptions, with:

Voluntary Prepayments. The Company may voluntarily prepay outstanding loans under the Term Loan Facility at any time without premium or penalty other than customary “breakage” costs with respect to LIBOR loans, provided, however, that if on or prior to the date that is six months after the closing date of the Term Loan Facility, the Company prepays any loan in connection with a repricing transaction, the Company must pay a prepayment premium of 1.00% of the aggregate principal amount of the loans so prepaid.

Amortization and Final Maturity. The Company is required to make scheduled quarterly payments each equal to 0.25% of the original principal amount of the term loans made on the closing date, with the balance due on the seventh anniversary of the closing date.

Guarantees and Security. All obligations under the Term Loan Facility are unconditionally guaranteed by certain of the Company’s existing wholly owned domestic subsidiaries, and are required to be guaranteed by certain of the Company’s future wholly owned domestic subsidiaries. All obligations under the Term Loan Facility, and the guarantees of those obligations, are secured, subject to certain exceptions, by substantially all of the Company’s assets and the assets of the Company’s immediate parent and the Company’s subsidiary guarantors, including, in each case subject to customary exceptions and exclusions:

Certain Covenants and Events of Default. The Term Loan Facility contains a number of negative covenants that, among other things and subject to certain exceptions, restrict the Company’s ability and each of the Company’s subsidiaries ability to:

The credit agreement governing the Term Loan Facility does not require the Company to comply with any financial maintenance covenants but additionally contains certain customary representations and warranties, affirmative covenants and provisions relating to events of default.

The foregoing summary of the Term Loan Facility is not complete and is qualified in its entirety by reference to the credit and guaranty agreement and the pledge and security agreement entered into in connection with the closing of the Term Loan Facility, copies of which are filed as Exhibits 10.2 and 10.4 to this Current Report on Form 8-K and are incorporated herein by reference.

In connection with the closing of the ABL Facility and Term Loan Facility, on April 30, 2014, Goldman Sachs Bank USA, as collateral agent for the ABL Facility and as collateral agent for the Term Loan Facility, entered into an intercreditor agreement (the “Intercreditor Agreement”), which was acknowledged by the Company. The Intercreditor Agreement governs the relative priorities (and certain other rights) of the ABL Facility lenders and Term Loan Facility lenders pursuant the respective security agreements that each entered into with the Company and the guarantors.

The foregoing summary of the Intercreditor Agreement is not complete and is qualified in its entirety by reference to the intercreditor agreement entered into in connection with the closing of the Term Loan Facility and ABL Facility, a copy of which is filed as Exhibit 10.5 to this Current Report on Form 8-K and incorporated herein by reference.

Item 2.01 Completion of Acquisition or Disposition of Assets.

Effective April 30, 2014, pursuant to the Agreement and Plan of Merger, dated as of February 4, 2014 (the “Merger Agreement”), among the Company, Atomic Merger Corporation, a Delaware corporation (“Merger Sub”), and ATMI, Inc., a Delaware corporation (“ATMI”), Merger Sub was merged with and into ATMI, with ATMI continuing as the surviving corporation and as a wholly owned subsidiary of the Company (the “Merger”).

Upon completion of the Merger, each share of common stock of ATMI, par value $0.01 per share, issued and outstanding immediately prior to the completion of the Merger, other than: (i) shares owned directly by the Company, or any of its subsidiaries; (ii) shares owned by ATMI as treasury stock, or by any of its subsidiaries; (iii) restricted stock awards issued by ATMI; or (iv) shares as to which dissenters’ rights have been properly exercised, was cancelled and extinguished and converted into the right to receive: $34.00 per share in cash, without interest or dividends thereon, less any applicable withholding taxes.

A total of approximately $1.15 billion in cash will be paid as consideration for the Merger.

Item 8.01 Other Events.

On April 30, 2014, the Company issued a press release announcing the completion of the transactions contemplated by the Merger Agreement described above. A copy of this press release is filed herewith as Exhibit 99.1 to this Form 8-K and is incorporated in this Item 8.01 by reference.

Item 9.01 Financial Statements and Exhibits.

SIGNATURE

Pursuant to the requirements of the Securities Exchange Act of 1934, the registrant has duly caused this report to be signed on its behalf by the undersigned hereunto duly authorized.

Date: May 1, 2014

EXHIBIT INDEX