Filed by Nanometrics Incorporated

Pursuant to Rule 425

under the Securities Act of 1933, as amended

and deemed filed pursuant to Rule 14a-12

under the Securities Exchange Act of 1934, as amended

Subject Company: Nanometrics Incorporated

(Commission File No. 000-13470)

Dated: October 11, 2019

On October 11, 2019, MacKenzie Partners, Inc., the proxy solicitor for Nanometrics Incorporated., circulated the below shareholder reminder letter to shareholders of record as of September 3, 2019.

October 11, 2019

Dear Stockholder:

We recently delivered to you a joint proxy statement/prospectus of Nanometrics Incorporated (NANO) wherein your support is requested to approve, among other matters, the issuance of shares of Nanometrics common stock to stockholders of Rudolph Technologies, Inc., as well as the adoption of two Nanometrics Charter Proposals. We urge your support for all the proposals to be voted upon at the NANO special meeting of stockholders to be held on October 24, 2019.    As of the date of this letter your shares of NANO remain unvoted.

The NANO board of directors unanimously recommends that stockholders vote “FOR” each of the proposals being submitted to a vote at the NANO special meeting of stockholders.

Please Vote Your NANO Shares Today!

Regardless of the number of shares you own your vote is very important. We encourage all stockholders to have their voices heard.

There are three ways to vote your shares of NANO without attending the NANO special meeting of stockholders in person – each only taking a few moments:

• By Internet – Stockholders can submit their vote via internet at www.proxyvote.com; please have the control number located on the enclosed vote instruction form available;

• By Telephone – Stockholders in the United States can submit their vote by calling the toll-free number indicated on the enclosed vote instruction form; please have your control number located on the enclosed vote instruction form available when calling; or

• By Mail – Stockholders can vote by mail by completing, signing, dating and returning the enclosed vote instruction form in the postage-paid envelope provided.

To be valid, your vote by telephone, internet or mail must be received by 11:59 p.m. (Eastern Time) on October 23, 2019, the day preceding the NANO special meeting of stockholders.

If you need assistance in voting your shares or have questions regarding the NANO special meeting of stockholders, please contact NANO’s proxy solicitor, MacKenzie Partners, Inc., at (800) 322-2885 (toll-free) or (212) 929-5500 (collect), or email at proxy@mackenziepartners.com.

We thank you for your continued support of NANO.

Sincerely,

Nanometrics Incorporated

If you have questions or need assistance in voting your shares, please contact:

1407 Broadway, 27^th Floor

New York, New York 10018

(212) 929-5500 or

Call Toll-Free (800) 322-2885

Email: proxy@mackenziepartners.com

Forward-Looking Statements

This communication contains “forward-looking statements” within the meaning of the Private Securities Litigation Reform Act of 1995 that are subject to risks and uncertainties and are made pursuant to the safe harbor provisions of Section 27A of the Securities Act of 1993, as amended, and Section 21E of the Securities Exchange Act of 1934, as amended. The words “believe” “continue,” “could,” “expect,” “anticipate,” “intends,” “estimate,” “forecast,” “project,” “should,” “may,” “will,” “would” or the negative thereof and similar expressions are intended to identify such forward-looking statements. These forward-looking statements are only predictions and involve known and unknown risks and uncertainties, many of which are beyond the control of Nanometrics Incorporated (“Nanometrics”) and Rudolph Technologies, Inc. (“Rudolph”). Statements in this communication regarding Nanometrics, Rudolph, or the proposed business combination between Nanometrics and Rudolph (the “Proposed Transaction”) that are forward-looking are based on management’s estimates, assumptions and projections, and are subject to significant uncertainties and other factors, many of which are beyond Nanometrics’ and Rudolph’s control. These factors and risks include, but are not limited to, (i) weakening of global and/or regional economic conditions, generally or specifically in the semiconductor industry, which could decrease the demand for Nanometrics’ and Rudolph’s products and solutions; (ii) the ability of

Nanometrics or Rudolph to meet rapid demand shifts; (iii) the ability of Nanometrics or Rudolph to continue technological innovation and introduce new products to meet customers’ rapidly changing requirements; (iv) the companies’ concentrated customer bases; (v) the ability of Nanometrics or Rudolph to identify, effect and integrate acquisitions, joint ventures or other transactions; (vi) the ability of Nanometrics or Rudolph to protect and enforce intellectual property rights; (vii) operational, political and legal risks of Nanometrics’ and Rudolph’s international operations; (viii) the increasing complexity of certain manufacturing processes; (ix) raw material shortages and price increases; (x) changes in government regulations of the countries in which Nanometrics and Rudolph operate; (xi) the fluctuation of currency exchange rates; (xii) fluctuations in the market price of Nanometrics’ stock; and (xiii) other risk factors and additional information. In addition, material risks that could cause actual results to differ from forward-looking statements include: the inherent uncertainty associated with financial or other projections; the ability of the companies’ to integrate their respective businesses promptly and effectively and to achieve the anticipated synergies and value-creation contemplated by the proposed transaction; the companies’ ability to obtain the approval of the Proposed Transaction by their respective stockholders and the timing of the closing of the Proposed Transaction, including the risk that the conditions to the transaction are not satisfied on a timely basis or at all and the failure of the Proposed Transaction to close for any other reason; the risk that a consent or authorization that may be required for the Proposed Transaction is not obtained or is obtained subject to conditions that are not anticipated; unanticipated difficulties or expenditures relating to the transaction, the response of business partners and retention as a result of the announcement and pendency of the Proposed Transaction; and the diversion of management time in connection with the Proposed Transaction. For a more detailed discussion of such risks and other factors, see Nanometrics’ and Rudolph’s filings with the Securities and Exchange Commission (the “SEC”), including under the heading “Risks Factors” in Nanometrics’ Annual Report on Form 10-K for the fiscal year ended December 29, 2018, filed on February 25, 2019, and Rudolph’s Annual Report on Form 10-K for the fiscal year ended December 31, 2018, filed on February 15, 2019 and in any other subsequently filed periodic reports or other filings of the companies with the SEC, each as available on the SEC website at www.sec.gov or investor.nanometrics.com or investors.rudolphtech.com. Neither Nanometrics nor Rudolph assumes any obligation to update any forward-looking statements or information, which speak as of their respective dates, to reflect events or circumstances after the date of this communication, or to reflect the occurrence of unanticipated events, except as may be required under applicable securities laws. Investors should not assume that any lack of update to a previously issued “forward-looking statement” constitutes a reaffirmation of that statement.

Additional Information and Where to Find It

This communication is for informational purposes only and does not constitute an offer to buy or sell or the solicitation of an offer to buy or sell any securities or a solicitation of any vote or approval. This communication relates to the Proposed Transaction. In connection with the Proposed Transaction, Nanometrics filed with the SEC an amendment to the registration statement on Form S-4 on September 6, 2019, which includes a joint proxy statement of Nanometrics and Rudolph that also constitutes a prospectus of Nanometrics. The registration statement was declared effective by the SEC on September 10, 2019, and Nanometrics and Rudolph commenced mailing the joint proxy statement/prospectus to stockholders of Nanometrics and stockholders of Rudolph on or about September 12, 2019. Each of Nanometrics and Rudolph also plan to file other relevant

documents with the SEC regarding the Proposed Transaction. No offering of securities shall be made, except by means of a prospectus meeting the requirements of Section 10 of the U.S. Securities Act of 1933, as amended. INVESTORS AND SECURITY HOLDERS ARE URGED TO READ THE REGISTRATION STATEMENT, JOINT PROXY STATEMENT/PROSPECTUS AND OTHER DOCUMENTS FILED OR THAT WILL BE FILED WITH THE SEC CAREFULLY AND IN THEIR ENTIRETY IF AND WHEN THEY BECOME AVAILABLE BECAUSE THEY CONTAIN OR WILL CONTAIN IMPORTANT INFORMATION THAT STOCKHOLDERS SHOULD CONSIDER BEFORE MAKING ANY DECISION REGARDING THE PROPOSED TRANSACTION. Investors and security holders may obtain free copies of these documents and other documents containing important information about Nanometrics and Rudolph through SEC’s website at www.sec.gov. Copies of the documents filed with the SEC by Nanometrics are available free of charge on Nanometrics’ website at investor.nanometrics.com or by contacting Nanometrics’ Investor Relations Department by email at ir@nanometrics.com or by phone at (530) 265-9899. Copies of the documents filed with the SEC by Rudolph are available free of charge on Rudolph’s website at investors.rudolphtech.com or by contacting Rudolph’s Investor Relations Department by email at investors@rudolphtech.com or by phone at (978) 253-6200.

Participants in the Solicitation

Nanometrics, Rudolph and certain of their respective directors and executive officers may be deemed to be participants in the solicitation of proxies in respect of the Proposed Transaction. Information about the directors and executive officers of Nanometrics is set forth in Nanometrics’ proxy statement for its 2019 annual meeting of stockholders, which was filed with the SEC on April 3, 2019, and Nanometrics’ Annual Report on Form 10-K for the fiscal year ended December 29, 2018, which was filed with the SEC on February 25, 2019. Information about the directors and executive officers of Rudolph is set forth in its proxy statement for its 2019 annual meeting of stockholders, which was filed with the SEC on April 2, 2019, and Rudolph’s Annual Report on Form 10-K for the fiscal year ended December 31, 2018, which was filed with the SEC on February 15, 2019. Other information regarding the participants in the proxy solicitations and a description of their direct and indirect interests, by security holdings or otherwise, is contained in the joint proxy statement/prospectus and other relevant materials filed or to be filed with the SEC regarding the Proposed Transaction. Investors should read the joint proxy statement/prospectus and other relevant materials carefully before making any voting or investment decisions. You may obtain free copies of these documents from Nanometrics or Rudolph using the sources indicated above.

No Offer or Solicitation

This communication shall not constitute an offer to sell or the solicitation of an offer to buy any securities, nor shall there be any sale of securities in any jurisdiction in which such offer, solicitation or sale would be unlawful prior to registration or qualification under the securities laws of any such jurisdiction. No offering of securities shall be made except by means of a prospectus meeting the requirements of Section 10 of the U.S. Securities Act of 1933, as amended.