Document:

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                                                                     EXHIBIT 4.1

                        SEE RESTRICTIONS ON REVERSE SIDE

                       Incorporated Under the Laws of the
                               State of Minnesota

                  Number                                      Shares

                                 ENTEGRIS, INC.

      This Certifies that __________________________________________is the
                         owner and registered holder of
               ___________________________ shares of common stock,
                  par value $0.01 per share, of Entegris, Inc.

     Transferable only on the books of the corporation by the holder hereof
                  in person or by duly authorized attorney upon
                surrender of this certificate properly endorsed.

            IN WITNESS WHEREOF, the said corporation has caused this
       certificate to be signed by its duly authorized officers and to be
                     sealed with the seal of the corporation
                this __________ day of ___________________, 1999

---------------------------------           --------------------------------
Chairman                                    President
Dan Quernemoen                              Stan Geyer
<PAGE>

The shares represented by this certificate have been purchased for investment
within the meaning of the Securities Act of 1993, as amended (the "Act") and
applicable state securities laws, have not been registered under said federal or
state securities laws, and the shares may not be sold, offered for sale,
pledged, or otherwise transferred without an effective registration statement
under the Act and applicable state securities laws, or an opinion of counsel
satisfactory to the company to the effect that the proposed transaction will be
exempt from registration.

For Value Received __________ hereby sell, assign and transfer unto
___________________________________________________________________________
________________________________________ Shares represented by the within
Certificate, and do hereby irrevocably constitute and appoint Attorney to
transfer the said shares on the Books of the within named limited liability
company with full power of substitution in the premises.

Dated _______________, 19 _____.

IN PRESENCE OF

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NOTICE: THE SIGNATURE TO THIS ASSIGNMENT MUST CORRESPOND WITH THE NAME AS
WRITTEN UPON THE FACE OF THIS CERTIFICATE IN EVERY PARTICULAR, WITHOUT
ALTERATION OR ENLARGEMENT OR ANY CHANGE WHATEVER.<PAGE>

                                                                    EXHIBIT 10.1

                                 ENTEGRIS, INC.
                          1999 Long-Term Incentive and
                                STOCK OPTION PLAN

     1. Purpose. The purpose of the Plan is to provide incentives to attract,
retain and motivate eligible persons whose present and potential contributions
are important to the success of the Company, its Subsidiaries and Affiliates, by
offering them an opportunity to participate in the Company's future performance
through grants of Options and Awards. Capitalized terms not defined in the text
are defined in Section 23.

     2. Types of Stock Options and Awards.

          2.1 Options and Shares. Options granted under this Plan may be either:
     (a) incentive stock options ("ISOs") within the meaning of Section 422 of
     the Revenue Code, or (b) nonqualified stock options ("NSOs"), as designated
     at the time of grant. The Shares that may be purchased upon exercise of
     Options granted under this Plan are shares of the Company's Common Stock,
     $.01 par value per share.

          2.2 Awards. Awards granted under this Plan include Performance Awards
     (denominated or payable in cash, Shares, other securities and other awards
     or other property) and Restricted Stock Awards, as designated at the time
     of grant.

     3. Shares Subject to The Plan.

          3.1 Number of Shares Available. Subject to Section 3.2, the total
     number of Shares reserved and available for grant and issuance pursuant to
     the Plan shall be initially four million five hundred thousand (4,500,000)
     Shares. Such Shares may be either authorized but unissued shares, or issued
     shares which have been reacquired by the Company. Subject to Section 3.2,
     Shares shall again be available for grant and issuance in connection with
     future Options or Awards under the Plan that: (a) are subject to issuance
     upon exercise of an Option but cease to be subject to such Option for any
     reason other than exercise of such Option; (b) are subject to an Option or
     Award granted hereunder but are forfeited or are repurchased by the Company
     at the original issue price; or (c) are subject to an Option or Award that
     otherwise terminates without Shares being issued. The Committee shall have
     the authority to replenish the Plan annually with additional Shares by
     electing to increase the number of Shares available for issuance under the
     Plan by up to four percent (4%) of the total outstanding Shares of the
     Company, such election to be made within ninety (90) days after the end of
     the fiscal year; provided, however, that the total number of Shares
     reserved and available for grant pursuant to the Plan shall not exceed
     seven million five hundred thousand (7,500,000) Shares. At all times during
     the term of this Plan, the Company shall reserve and keep available such
     number of Shares as shall be required to satisfy the requirements of
     outstanding Options and Awards under this Plan.
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          3.2 Adjustment of Shares. In the event that the number of outstanding
     Shares change as a result of a stock dividend, recapitalization, stock
     split, reverse stock split, subdivision, combination, reclassification or
     similar change in the capital structure of the Company without
     consideration, then: (a) the number of Shares reserved for issuance under
     this Plan; (b) the Exercise Prices of and number of Shares subject to
     outstanding Options; (c) the number of Shares and price per Share subject
     to outstanding Awards; and (iv) the amount payable in connection with
     Awards, shall be proportionately adjusted, subject to any required action
     by the Board or the shareholders of the Company and in compliance with
     applicable securities laws; provided, however, that fractions of a Share
     shall not be issued but shall either be paid in cash at Fair Market Value
     or shall be rounded up to the nearest Share, as determined by the
     Committee; and provided further that the Exercise Price of any Option may
     not be decreased to below the par value of the Shares.

     4. Eligibility. ISOs may be granted only to employees (including officers
and directors who are also employees) of the Company or of a Subsidiary of the
Company.

     All other Options and Awards may be granted to employees, officers,
directors, consultants, independent contractors and advisors of the Company or
any Subsidiary or Affiliate of the Company; provided, however, that such
consultants, independent contractors and advisors render bona fide services not
in connection with the offer and sale of securities in a capital-raising
transaction. A person may be granted more than one Option and/or Award under the
Plan. The Company also may, from time to time and in the manner determined by
the Committee, substitute or assume outstanding options or performance or
restricted stock awards granted by another company, whether in connection with
an acquisition of such other company or otherwise.

     5. Administration.

          5.1 Committee Authority. This Plan shall be administered by the
     Committee or the Board acting as the Committee. Subject to the general
     purposes, terms and conditions of this Plan, and to the direction of the
     Board, the Committee shall have full power to implement and carry out this
     Plan. The Committee shall have the authority to:

               (a) Construe and interpret the Plan, any Option Agreement or
          Award Agreement and any other agreement or document executed pursuant
          to this Plan.

               (b) prescribe, amend and rescind rules and regulations relating
          to this Plan.

               (c) select persons to receive Options or Awards.

               (d) determine the form and terms of Options and Awards.

               (e) determine the number of Shares or other consideration subject
          to Options and Awards.

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               (f) determine whether Options and Awards will be granted singly,
          in combination, in tandem with, in replacement of or as alternatives
          to, other Options and/or Awards under this Plan or any other incentive
          or compensation plan of the Company or any Subsidiary or Affiliate of
          the Company.

               (g) grant waivers of Plan, Option or Award conditions.

               (h) Determine the vesting, exercisabilty and payment of Options
          and Awards.

               (i) correct any defect, supply any omission, or reconcile
          inconsistency in the Plan, any Option, any Option Agreement or Award
          Agreement.

               (j) determine whether an Option or Award has been earned.

               (k) make all other determinations necessary or advisable for the
          administration of this Plan.

          5.2 Committee Discretion. Any determination made by the Committee with
     respect to any Option or Award shall be made in its sole discretion at the
     time of grant of the Option or the Award or, unless in contravention of any
     express term of this Plan or the Option/Award, at any later time, and such
     determination shall be final and binding on the Company and all persons
     having an interest in any Option or Award under this Plan.

          5.3 Exchange Act Requirements. If the Company is subject to the
     Exchange Act, the Company will take appropriate steps to comply with the
     disinterested director requirements of Section 16(b) of the Exchange Act,
     including but not limited to, the appointment by the Board of a Committee
     consisting of not less than two Persons (who are members of the Board),
     each of whom is a Disinterested Person.

     6. Terms and Conditions of Options. The Committee may grant Options to
eligible persons and shall determine whether such Options shall be ISOs within
the meaning of the Revenue Code or NSOs, the number of Shares subject to such
Options, the Exercise Price of such Options, the period during which such
Options may be exercised, and all other terms and conditions of such Options,
subject to the following:

          6.1 Form of Option Grant. Each Option granted under this Plan shall be
     evidenced by an Option Agreement which shall expressly identify the Option
     as an ISO or NSO, and be in such form and contain such provisions (which
     need not be the same for each Participant) as the Committee shall from time
     to time approve, and which shall comply with and be subject to the terms
     and conditions of this Plan.

          6.2 Date of Grant. The date of grant of an Option shall be the date on
     which the Committee makes the determination to grant such Option unless
     otherwise specified by the Committee.

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          6.3 Exercise Period. Options shall be exercisable within the times or
     upon the events determined by the Committee as set forth in the Option
     Agreement; provided, however, that no ISO shall be exercisable after the
     expiration of ten (10) years from the date the Option is granted; and
     provided further that no ISO granted to a person who directly or by
     attribution owns more than ten percent (10%) of the total combined voting
     power of all classes of stock of the Company or any Subsidiary of the
     Company (a "Ten Percent Shareholder") shall be exercisable after the
     expiration of five (5) years from the date the ISO is granted.

          6.4 Exercise Price. The Exercise Price shall be determined by the
     Committee when the Option is granted, provided, however, that: (a) the
     Exercise Price of an ISO shall be not less than one hundred percent (100%)
     of the Fair Market Value of the Shares on the date of grant; (b) the
     Exercise Price of any ISO granted to a Ten Percent Shareholder shall not be
     less than one hundred ten percent (110%) of the Fair Market Value of the
     Shares on the date of grant; and (c) the Exercise Price of any Option may
     not be decreased to below the par value of the Shares, if any.

          6.5 Method of Exercise. Options may be exercised only by delivery to
     the Company of a written stock option exercise agreement (the "Exercise
     Agreement") in a form approved by the Committee (which need not be the same
     for each Participant), together with payment in full of the Exercise Price
     for the number of Shares being purchased.

          6.6 Limitations on ISOs. The aggregate Fair Market Value (determined
     as of the date of grant) of Shares with respect to which ISOs are
     exercisable for the first time by a Participant during any calendar year
     (under this Plan or under any other incentive stock option plan of the
     Company or any Subsidiary or Affiliate of the Company) shall not exceed One
     Hundred Thousand Dollars ($100,000). If the Fair Market Value of Shares on
     the date of grant with respect to which ISOs are exercisable for the first
     time by a Participant during any calendar year exceeds One Hundred Thousand
     Dollars ($100,000), the Options for the first One Hundred Thousand Dollars
     ($100,000) worth of Shares to become exercisable in such calendar year
     shall be ISOs and the Options for the amount in excess of One Hundred
     Thousand Dollars ($100,000) that become exercisable in that calendar year
     shall be NSOs. In the event that the Revenue Code or the regulations
     promulgated thereunder are amended after the Effective Date of the Plan to
     provide for a different limit on the Fair Market Value of Shares permitted
     to be subject to ISOs, such different limit shall be automatically
     incorporated herein and shall apply to any Options granted after the
     effective date of such amendment.

          6.7 Modification, Extension or Renewal. The Committee may modify,
     extend or renew outstanding Options and authorize the grant of new Options
     in substitution therefor, provided that any such action may not, without
     the written consent of the Participant, impair any of the Participant's
     rights under any Option previously granted.

          6.8 No Disqualification. Notwithstanding any other provision in this
     Plan, no term of this Plan relating to ISOs shall be interpreted, amended
     or altered, nor shall any discretion or authority granted under this Plan
     be exercised, so as to disqualify this Plan under

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     Section 422 of the Revenue Code or, without the consent of the Participant
     affected, to disqualify any ISO under Section 422 of the Revenue Code.

     7. Payment For Shares Purchased Upon The Exercise of Options. Payment for
Shares upon the exercise of Options may be made in cash or by check or, or in
any other manner approved for the Participant by the Committee and where
permitted by Section 16(b) of the Exchange Act or other applicable law
including, but not limited to, cancellation of indebtedness, payment by a
promissory note, waiver of compensation, the surrender of other Company shares,
or a cashless exercise through the surrender of a portion of the Option.

     8. Withholding Taxes. Whenever Shares and/or other property are to be
issued upon exercise of Options or Awards granted under this Plan, the Company
may require the Participant to remit to the Company an amount sufficient to
satisfy federal, state and local withholding tax requirements prior to the
delivery of any certificate or certificates for such Shares. Whenever, under
this Plan, payments in satisfaction of Options or Performance Awards are to be
made in cash, such payment shall be net of an amount sufficient to satisfy
federal, state and local withholding tax requirements.

     9. Restricted Stock Awards. Awards of Shares subject to forfeiture and
transfer restrictions may be granted by the Committee. Any Restricted Stock
Award shall be evidenced by a Restricted Stock Award Agreement in such form as
the Committee shall from time to time approve, which agreement shall comply with
and be subject to the following terms and conditions and any additional terms
and conditions established by the Committee that are consistent with the terms
of the Plan.

          9.1 Grant of Restricted Stock Awards. Each restricted stock award made
     under the Plan shall be for such number of Shares as shall be determined by
     the Committee and set forth in the Restricted Stock Award Agreement
     containing the terms of such Restricted Stock Award. The Restricted Stock
     Award Agreement shall set forth a period of time during which the grantee
     must remain in the continuous employment of the Company in order for the
     forfeiture and transfer restrictions to lapse. If the Committee so
     determines, the restrictions may lapse during such restricted period in
     installments with respect to specified portions of the Shares covered by
     the Restricted Stock Award. The Restricted Stock Award Agreement may also,
     in the discretion of the Committee, set forth performance or other
     conditions that will subject the Shares to forfeiture and transfer
     restrictions. The Committee may, at its discretion, waive all or any part
     of the restrictions applicable to any or all outstanding Restricted Stock
     Awards.

          9.2 Delivery of Shares and Restrictions. At the time of a Restricted
     Stock Award, a certificate representing the number of Shares awarded
     thereunder shall be registered in the name of the Participant. Such
     certificate shall be held by the Company or any custodian appointed by the
     Company for the account of the Participant subject to the terms and
     conditions of this Plan and the grant or award, and shall bear such a
     legend setting forth the restrictions imposed thereon as the Committee, in
     its discretion, may determine. The Participant shall have all rights of a
     shareholder with respect to the Shares, including the right to receive
     dividends and the right to vote such Shares, subject

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     to the following restrictions: (i) the Participant shall not be entitled to
     delivery of the stock certificate until the expiration of the restricted
     period and the fulfillment of any other restrictive conditions set forth in
     the Restricted Stock Award Agreement with respect to such Shares; (ii) none
     of the Shares may be sold, assigned, transferred, pledged, hypothecated or
     otherwise encumbered or disposed of during such restricted period or until
     after the fulfillment of any such other restrictive conditions; and (iii)
     except as otherwise determined by the Committee, all of the Shares shall be
     forfeited and all rights of the grantee to such Shares shall terminate,
     without further obligation on the part of the Company, unless the
     Participant remains in the continuous employment of the Company for the
     entire restricted period in relation to which such Shares were granted and
     unless other restrictive conditions relating to the Restricted Stock Award
     are met. Any Common Stock, any other securities of the Company and any
     other property (except for cash dividends) distributed with respect to the
     Shares subject to Restricted Stock Awards shall be subject to the same
     restrictions, terms and conditions as such restricted Shares.

          9.3 Termination of Restrictions. At the end of the restricted period
     and provided that any other restrictive conditions of the Restricted Stock
     Award are met, or at such earlier time as otherwise determined by the
     Committee, all restrictions set forth in the Restricted Stock Award
     Agreement relating to the Restricted Stock Award or in this Plan shall
     lapse as to the Restricted Shares subject thereto, and a stock certificate
     for the appropriate number of Shares, free of the restrictions and the
     restricted stock legend, shall be delivered to the Participant or the
     Participant's beneficiary or estate, as the case my be.

     10. Performance Awards.

          10.1 Grant of Performance Awards. The Committee is further authorized
     to grant performance awards. Subject to the terms of this Plan and any
     applicable award agreement, a Performance Award granted under this Plan:
     (i) may be denominated or payable in cash, Shares (including without
     limitation, restricted stock), other securities, other awards or other
     property; and (ii) shall confer on the Participant rights valued as
     determined by the Committee, in its discretion, and payable to, or
     exercisable by, the Participant, in whole or in part, upon the achievement
     of such performance goals during such performance periods as the Committee,
     in its discretion, shall establish. Subject to the terms of this Plan and
     any applicable award agreement, the performance goals to be achieved during
     any performance period, the length of any performance period, the amount of
     any Performance Award granted, and the amount of any payment or transfer to
     be made by the Participant and by the Company under any Performance Award
     shall be determined by the Committee.

          10.2 Shares Subject to Performance Awards. For purposes of this
     Section 10: (i) if a Performance Award entitles the Participant to receive
     or purchase Shares, the number of Shares covered by such Performance Award
     to which such Performance Award relates shall be counted on the date of
     grant of such Performance Award against the aggregate number of Shares
     available under this Plan; and (ii) if a Performance Award entitles the
     Participant to receive cash payments but the amount of such payments are
     denominated in or based on a number of Shares, the number of Shares shall
     be counted on the date of

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     grant of such Performance Award against the aggregate number of shares
     available under this Plan; provided, however, that Performance Awards that
     operate in tandem with (whether granted simultaneously with or at a
     different time from), or that are substituted for, other Performance Awards
     may be counted or not counted under procedures adopted by the Committee in
     order to avoid double counting.

     11. Privileges of Stock Ownership. No Participant shall have any of the
rights of a shareholder with respect to any Shares until the Shares are issued
to the Participant.

     12. Transferability. Options and Awards granted under this Plan, and any
interest therein, shall not be transferable or assignable by a Participant, and
may not be made subject to execution, attachment or similar process, otherwise
than by will or by the laws of descent and distribution or pursuant to a
qualified domestic relations order as defined by the Revenue Code or Title I of
the Employee Retirement Income Security Act (or the rules thereunder). During
the lifetime of the Participant an Option or Award shall be exercisable only by
the Participant, and any elections with respect to an Option or Award may be
made only by the Participant.

     13. Restrictions on Shares. At the discretion of the Committee, the Company
may require that an Option or Award be subject to restrictions including, but
not limited to, a right of first refusal or a right to repurchase by the
Company.

     14. Certificates. All certificates for Shares or other securities delivered
under this Plan shall be subject to such stock transfer orders, legends and
other restrictions as the Committee may deem necessary or advisable, including
restrictions under any applicable federal, state or foreign securities law, or
any rules, regulations and other requirements of the SEC or any stock exchange
or automated quotation system upon which the Shares may be listed.

     15. Escrow; Pledge of Shares. To enforce any restrictions on a
Participant's Shares, and/or to enforce any obligation of a Participant in
connection with an Option or Award the Committee may require the Participant to
deposit all certificates representing Shares, together with stock powers or
other instruments of transfer approved by the Committee, appropriately endorsed
in blank, with the Company or an agent designated by the Company to hold in
escrow until such restrictions have lapsed or terminated, and the Committee may
cause a legend or legends referencing such restrictions to be placed on the
certificates.

     16. Securities Laws and Other Regulatory Compliance. An Option or Award
shall not be effective unless such Option or Award is in compliance with all
applicable federal and state securities laws, rules and regulations of any
governmental body, and the requirements of any stock exchange or automated
quotation system upon which the Shares may then be listed, as they are in effect
on the date of grant of the Option or Award and also on the date of exercise or
other issuance of Shares. Notwithstanding any other provision in this Plan, the
Company shall have no obligation to issue or deliver certificates for Shares
under this Plan prior to: (a) obtaining any approvals from governmental agencies
that the Company determines are necessary or advisable and/or (b) completion of
any registration or other qualification of such Shares under any state or
federal law or ruling of any governmental body that the Company determines to be
necessary or advisable. The Company shall be under no obligation to register the
Shares with the

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SEC or to effect compliance with the registration, qualification or listing
requirements of any state securities laws, stock exchange or automated quotation
system, and the Company shall have no liability for any inability or failure to
do so.

     17. No Obligation to Employ. Nothing in this Plan or any Option or Award
granted under this Plan shall confer or be deemed to confer on any Participant
any right to continue in the employ of or to continue any other relationship
with, the Company or any Subsidiary or Affiliate of the Company or limit in any
way the right of the Company or any Subsidiary or Affiliate of the Company to
terminate the Participant's employment or other relationship at any time, with
or without cause.

     18. Adoption and Shareholder Approval. This Plan shall become effective on
the date that it is adopted by the Board. This Plan shall be approved by the
shareholders of the Company (excluding Shares issued pursuant to this Plan),
consistent with applicable laws, within twelve (12) months before or after the
Effective Date.

     19. Term of Plan. This Plan shall terminate ten (10) years from the
Effective Date or, if earlier, the date of shareholder approval.

     20. Amendment or Termination of This Plan. The Board may at any time
terminate or amend this Plan in any respect, including, without limitation,
amendment of any form of Option Agreement or Award Agreement or instrument to be
executed pursuant to the Plan; provided, however, that the Board shall not,
without the approval of the shareholders of the Company, amend the Plan in any
manner that requires such shareholder approval pursuant to the Revenue Code or
the regulations promulgated thereunder as such provisions apply to ISO plans or
pursuant to the Exchange Act or Rule 16b-3 (or its successor), as amended,
thereunder.

     21. Nonexclusivity of This Plan. Neither the adoption of this Plan by the
Board, the submission of this Plan to the shareholders of the Company for
approval nor any provision of this Plan shall be construed as creating any
limitations on the power of the Board to adopt such additional compensation
arrangements as it may deem desirable including, without limitation, the
granting of stock options or awards otherwise than under this Plan, and such
arrangements may be either generally applicable or applicable only in specific
cases.

     22. Governing Law. This Plan and all agreements, documents and instruments
entered into pursuant to this Plan shall he governed by and construed in
accordance with the internal laws of the State of Minnesota, excluding that body
of law pertaining to conflict of law or choice of law.

     23. Definitions. As used in this Plan, the following terms shall have the
following meanings:

     "Affiliate" means any corporation that directly, or indirectly through one
or more intermediaries, controls or is controlled by, or is under common control
with, another corporation, where "control" (including the terms "controlled by"
and "under common control with") means the possession, direct or indirect, of
the power to cause the detection of the

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management and policies of the corporation, whether through the ownership of
voting securities, by contract or otherwise.

     "Award" means either a Performance Award or Restricted Stock Award granted
under this Plan, or both, as the context requires.

     "Award Agreement" means either a Performance Award Agreement or Restricted
Award Agreement granted under this Plan, or both, as the context requires.

     "Board" means the Board of Directors of the Company.

     "Committee" means the committee appointed by the Board to administer this
Plan, or if no committee is appointed, the Board.

     "Company" means Entegris, Inc., a corporation organized under the laws of
the State of Minnesota, or any successor corporation.

     "Disability" means a disability, whether temporary or permanent, partial or
total, within the meaning of Section 22(e)(3) of the Revenue Code, as determined
by the Committee.

     "Disinterested Person" means a director who has not, during the period that
person is a member of the Committee and for one year prior to service as a
member of the Committee, been granted or optioned equity securities pursuant to
the Plan or any other plan of the Company or any Subsidiary or Affiliate of the
Company, except in accordance with the requirements set forth in Rule
l6b-3(c)(2)(i) (and any successor regulation thereto) as promulgated by the SEC
under Section 16(b) of the Exchange Act, as such rule is amended from time to
time and as interpreted by the SEC.

     "Effective Date" means the date on which the Board adopts this Plan.

     "Exchange Act" means the Securities Exchange Act of 1934, as amended.

     "Exercise Price" means the price at which a holder of an Option may
purchase the Shares issuable upon exercise of the Option.

     "Fair Market Value" means, as of any date, the value of a Share of the
Company's Common Stock determined as follows:

          (a)  if such Common Stock is then quoted on the Nasdaq National Market
               System, its last reported sale price on the Nasdaq National
               Market System or, if no such reported sale takes place on such
               date, the average of the closing bid and asked prices.

          (b)  if such Common Stock is publicly traded and is then listed on a
               national securities exchange, the last reported sale price or, if
               no such reported sale takes place on such date, the average of
               the closing bid and asked prices on

                                       9
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               the principal national securities exchange on which the Common
               Stock is listed or admitted to trading.

          (c)  if such Common Stock is publicly traded but is not quoted on the
               Nasdaq National Market System nor listed or admitted to trading
               on a national securities exchange, the average of the closing bid
               and asked prices on such date, as reported by The Wall Street
               Journal, for the over-the-counter market.

          (d)  if none of the foregoing is applicable, by the Board of Directors
               of the Company in good faith.

     "Insider" means an officer or director of the Company or any other person
whose transactions in the Company's Common Stock are subject to Section 16 of
the Exchange Act.

     "Option" means a contractual right to purchase Shares at sometime in the
future at a specified price.

     "Option Agreement" means, with respect to each Option, the signed written
agreement between the Company and the Participant setting forth the terms and
conditions of the Option.

     "Participant" means a person who receives an Option or Award under this
Plan.

     "Performance Award" means an award of cash, Shares or other property
payable upon the achievement of specific performance goals.

     "Performance Award Agreement" means, with respect to each Performance
Award, the signed written agreement between the Company and the Participant
setting forth the terms and conditions of the Performance Award.

     "Plan" means this Entegris, Inc. 1999 Long-Term Incentive and Stock Option
Plan, as amended from time to time.

     "Restricted Stock Award" means an award of Shares subject to forfeiture and
transfer restrictions as determined by the Committee.

     "Restricted Stock Award Agreement" means, with respect to each Restricted
Stock Agreement, the signed written agreement between the Company and the
Participant setting forth the terms and conditions of the Restricted Stock
Award.

     "Revenue Code" means the Internal Revenue Code of 1986, as amended.

     "SEC" means the Securities and Exchange Commission.

                                       10
<PAGE>

     "Securities Act" means the Securities Act of 1933, as amended.

     "Shares" mean shares of the Company's Common Stock, $.01 par value per
share, reserved for issuance under this Plan, as adjusted pursuant to Sections 3
and 18 and any successor security.

     "Subsidiary" means any corporation (other than the Company) in an unbroken
chain of corporations beginning with the Company if, at the time of granting of
the Option, each of the corporations other than the last corporation in the
unbroken chain owns stock possessing fifty percent (50%) or more of the total
combined voting power of all classes of stock in one of the other corporations
in such chain.

                                       11

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