<PAGE>   1

                                                                    EXHIBIT 10.4

                      SECOND AMENDMENT TO CREDIT AGREEMENT

        THIS SECOND AMENDMENT TO CREDIT AGREEMENT (this "Amendment"), dated as
of April 13, 2001, is entered into by and among:

                (1) NOVELLUS SYSTEMS, INC., a California corporation
        ("Borrower");

                (2) Each of the financial institutions listed in Schedule I to
        the Credit Agreement referred to in Recital A below (collectively, the
        "Lenders"); and

                (3) ABN AMRO BANK N.V., as agent for the Lenders (in such
        capacity, "Agent").

                                    RECITALS

        A. Borrower, Lenders and Agent are parties to a Credit Agreement dated
as of June 9, 1997 (as amended by a First Amendment thereto dated as of August
28, 1997, the "Credit Agreement"), pursuant to which Lenders have provided to
Borrower a certain credit facility.

        B. Borrower now has requested Lenders and Agent to amend the Credit
Agreement to make certain changes thereto.

        C. Lenders and Agent are willing so to amend the Credit Agreement upon
the terms and subject to the conditions set forth in this Amendment.


                                    AGREEMENT

        NOW, THEREFORE, in consideration of the above recitals and for other
good and valuable consideration, the receipt and adequacy of which are hereby
acknowledged, Borrower, the Lenders and Agent hereby agree as follows:

        1. DEFINITIONS, INTERPRETATION. All capitalized terms defined above and
elsewhere in this Amendment shall be used herein as so defined. Unless otherwise
defined herein, all other capitalized terms used herein shall have the
respective meanings given to those terms in the Credit Agreement, as amended by
this Amendment. The rules of construction set forth in Schedule 1.02 to the
Credit Agreement shall, to the extent not inconsistent with the terms of this
Amendment, apply to this Amendment and are hereby incorporated by reference.

        2. AMENDMENTS TO CREDIT AGREEMENT. Subject to the satisfaction of the
conditions set forth in Paragraph 4 below, the Credit Agreement is hereby
amended as follows:

                (a) Paragraph 1.01 is amended by changing the definitions of the
        following terms appearing therein to read in their entireties as
        follows:

                        "Adjusted Net Income" shall mean, with respect to
                Borrower for any period, the sum, determined on a consolidated
                basis in accordance with GAAP, of the following:



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                                (a) The net income or net loss of Borrower and
                        its Subsidiaries for such period before provision for
                        income taxes;

                                      plus

                                (b) The sum (to the extent deducted in
                        calculating net income or loss in clause (a) above) of
                        (i) all Interest Expenses of Borrower and its
                        Subsidiaries accruing during such period, (ii) all
                        depreciation and amortization expenses of Borrower and
                        its Subsidiaries accruing during such period, and (iii)
                        all rental expenses of Borrower and its Subsidiaries
                        accruing during such period (excluding any rental
                        expenses that are capitalized by the lessor during such
                        period);

                                      minus

                                (c) Fifty percent (50%) of all Capital
                        Expenditures of Borrower and its Subsidiaries accruing
                        during such period.

                        "Agent's Fee Letter" shall mean collectively the letter
                agreement dated as of May 9, 1997 between Borrower and Agent
                regarding certain fees payable by Borrower to Agent and the
                letter agreements dated as of October 11, 2000 and December 5,
                2000 between Borrower and Agent regarding certain other fees
                payable by Borrower to Agent.

                        "Credit Documents" shall mean and include this
                Agreement, the Notes and the Agent's Fee Letter; all other
                notices, requests, certificates, documents, instruments and
                agreements delivered to Agent or any Lender pursuant to
                Paragraph 3.01; all other notices, requests, certificates,
                documents, instruments and agreements required to be delivered
                to Agent or any Lender in connection with any of the foregoing
                on or after the date of this Agreement; and all Rate Contracts
                provided to Borrower by any Lender to hedge against fluctuations
                in the LIBO Rate. (Without limiting the generality of the
                preceding definition, the term "Credit Documents" shall include
                all written waivers, amendments and modifications to any of the
                notices, requests, certificates, documents, instruments and
                agreements referred to therein.)

                        "Debt Service Coverage Ratio" shall mean, with respect
                to Borrower for any period, the ratio, determined on a
                consolidated basis in accordance with GAAP, of:

                                (a) The Adjusted Net Income of Borrower for such
                        period;

                                       to

                                (b) The sum of (i) all Interest Expenses of
                        Borrower and its Subsidiaries accruing during such
                        period, (ii) all rental expenses of Borrower and its
                        Subsidiaries accruing during such period (excluding any
                        rental expenses that are capitalized by the lessor
                        during such period), and (iii) 25% of all payments of
                        principal (or, in the case of Capital Leases, amounts
                        attributable to principal) of Funded Indebtedness
                        (excluding



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                        Synthetic Lease Obligations) paid or scheduled to be
                        paid by Borrower and its Subsidiaries due within one
                        year.

                        "EBITDA" shall mean, with respect to Borrower for any
                period, the sum, determined on a consolidated basis in
                accordance with GAAP, of the following:

                                (a) The net income or net loss of Borrower and
                        its Subsidiaries for such period before provision for
                        income taxes;

                                      plus

                                (b) The sum (to the extent deducted in
                        calculating net income or loss in clause (a) above) of
                        (i) all Interest Expenses of Borrower and its
                        Subsidiaries accruing during such period and (ii) all
                        depreciation and amortization expenses of Borrower and
                        its Subsidiaries accruing during such period.

                        "Funded Indebtedness" of any Person shall mean, without
                duplication:

                                (a) All obligations of such Person evidenced by
                        notes, bonds, debentures or other similar instruments
                        and all other obligations of such Person for borrowed
                        money (including obligations to repurchase receivables
                        and other assets sold with recourse);

                                (b) All obligations of such Person for the
                        deferred purchase price of property or services
                        (including obligations under letters of credit and other
                        credit facilities which secure or finance such purchase
                        price but excluding trade payables incurred by such
                        Person in the ordinary course of its business on
                        ordinary terms and not overdue) and all Synthetic Lease
                        Obligations of such Person (excluding the Economically
                        Defeased Portion of Synthetic Lease Obligations);

                                (c) All obligations of such Person under
                        conditional sale or other title retention agreements
                        with respect to property acquired by such Person (to the
                        extent of the value of such property if the rights and
                        remedies of the seller or lender under such agreement in
                        the event of default are limited solely to repossession
                        or sale of such property); and

                                (d) All obligations of such Person as borrower
                        under or with respect to Capital Leases.

                        "Pension Plan" shall mean any Employee Benefit Plan
                subject to Title IV of ERISA that either Borrower or any ERISA
                Affiliate maintains or contributes to or has any obligation
                under.

                        "Quick Ratio" shall mean, with respect to Borrower at
                any time, the ratio, determined on a consolidated basis in
                accordance with GAAP, of:

                                (a) The remainder of (i) the sum (without
                        duplication) of all cash, Cash Equivalents, short-term
                        investments and net accounts



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                        receivable of Borrower and its Subsidiaries at such
                        time, minus (ii) the sum (without duplication) of all
                        such cash, Cash Equivalents, short-term investments and
                        net accounts receivable that are subject to a Lien or
                        are otherwise restricted;

                                       to

                                (b) The current liabilities of Borrower and its
                        Subsidiaries at such time.

                (In calculating the Quick Ratio, Cash Equivalents and short-term
                investments shall be marked to market quarterly.)

                (b) Paragraph 1.01 is further amended by adding thereto, in the
        appropriate alphabetical order, the definitions of the following terms
        to read in their entireties as follows:

                        "Cash Balances" shall mean, with respect to Borrower and
                its Subsidiaries at any time, the sum, determined on a
                consolidated basis in accordance with GAAP, of (a) the
                unrestricted, unencumbered cash of Borrower and its Subsidiaries
                at such time and (b) the market value of unrestricted,
                unencumbered Cash Equivalents and short-term marketable
                securities (that are classified as current assets in accordance
                with GAAP) of Borrower and its Subsidiaries at such time. (In
                calculating Cash Balances, Cash Equivalents and short-term
                marketable securities shall be marked to market quarterly.)

                        "Economically Defeased Portion of Synthetic Lease
                Obligations" shall mean the remainder of (a) the sum of the
                "Tranche A" portions, "Tranche B" portions and "Tranche C"
                portions of leases constituting Economically Defeased Synthetic
                Lease Obligations, minus (b) the aggregate amount of the
                "Tranche A" portions of such leases that the lessee has sold,
                assigned or otherwise transferred to any other Person.

                        "Economically Defeased Synthetic Lease Obligations"
                shall mean Synthetic Lease Obligations under synthetic leases in
                which the lessee has secured the "Tranche B" portion of such
                leases and the "Tranche C" portion of such leases with cash
                and/or Cash Equivalents and initially has purchased a 100%
                participation interest in the "Tranche A" portion of such
                leases.

                        "Synthetic Lease Obligations" shall mean the monetary
                obligations of a Person under (a) a so-called synthetic,
                off-balance sheet or tax retention lease, or (b) an agreement
                for the use or possession of property creating obligations that
                do not appear on the balance sheet of such Person but which,
                upon the insolvency or bankruptcy of such Person, would be
                characterized as the indebtedness of such Person (without regard
                to accounting treatment).

                (c) Subparagraph 4.01(g) is amended to read in its entirety as
        follows:

                        (g) Litigation. Except as set forth in the most recent
                Form 10-Q and 10-K reports filed by Borrower with the Securities
                and Exchange Commission, no



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                actions (including, without limitation, derivative actions),
                suits, proceedings or investigations are pending or, to the
                knowledge of Borrower, threatened against Borrower or any of its
                Subsidiaries at law or in equity in any court or before any
                other Governmental Authority which (i) is reasonably likely
                (alone or in the aggregate) to have a Material Adverse Effect or
                (ii) seeks to enjoin, either directly or indirectly, the
                execution, delivery or performance by Borrower of the Operative
                Documents or the transactions contemplated thereby.

                (d) Subparagraph 4.01(k) is amended to read in its entirety as
        follows:

                        (k) No Agreements to Sell Assets; Etc. Neither Borrower
                nor any of its Subsidiaries has any legal obligation, absolute
                or contingent, to any Person to sell the assets of Borrower or
                any of its Subsidiaries (other than sales in the ordinary course
                of business), or to effect any merger, consolidation or other
                reorganization of Borrower or any of its Subsidiaries or to
                enter into any agreement with respect thereto, except for sales,
                mergers, consolidations or reorganizations permitted by
                Subparagraph 5.02(c), 5.02(d) or 5.02(e).

                (e) Subparagraph 4.01(l) is amended by changing clause (i) to
        read in its entirety as follows:

                        (i) Based on the most recent valuation date for any
                Pension Plan, the amount of unfunded benefit liabilities (as
                defined in Section 4001(a)(18) of ERISA), individually or in the
                aggregate for all Pension Plans (excluding for purposes of such
                computation any Pension Plans with respect to which assets
                exceed benefit liabilities) does not exceed an amount equal to
                $10,000,000. No Pension Plan has failed to meet the minimum
                funding standard of Code Section 412 (whether or not waived
                under Code Section 412(d)) or failed to make by its due date a
                required installment under Code Section 412(m). Neither Borrower
                nor any ERISA Affiliate has any liability with respect to any
                post-retirement benefit under any Employee Benefit Plan which is
                a welfare plan (as defined in section 3(1) of ERISA) that is
                reasonably likely to have a Material Adverse Effect.

                (f) Subparagraph 4.01(n) is amended to read in its entirety as
        follows:

                        (n) Patent and Other Rights. Borrower and its
                Subsidiaries own, license or otherwise have the right to use,
                under validly existing agreements, all patents, licenses,
                trademarks, trade names, trade secrets, service marks,
                copyrights and all rights with respect thereto, which are
                required to conduct their businesses as now conducted, except
                where the failure to have any such rights, either individually
                or collectively, is not reasonably likely to have a Material
                Adverse Effect.

                (g) Subparagraph 4.01(q) is amended to read in its entirety as
        follows:

                        (q) Subsidiaries, etc. Set forth in Schedule 4.01(q) (as
                supplemented by Borrower from time to time in a written notice
                to Agent) is a complete list of all of Borrower's Subsidiaries,
                the jurisdiction of incorporation of each, the



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                classes of Equity Securities of each and the percentages of
                shares of each such class owned directly or indirectly by
                Borrower.

                (h) Subparagraph 5.01(a) is amended by (i) changing clauses
        (iii), (iv) and (v) to read in their entireties as follows:

                        (iii) Contemporaneously with the quarterly and year-end
                Financial Statements required by the foregoing clauses (i) and
                (ii), a compliance certificate of the president or chief
                financial officer of Borrower which (A) states that no Default
                has occurred and is continuing, or, if any such Default has
                occurred and is continuing, a statement as to the nature thereof
                and what action Borrower proposes to take with respect thereto;
                and (B) sets forth, for the quarter or year covered by such
                Financial Statements or as of the last day of such quarter or
                year (as the case may be), the calculation of the financial
                ratios and tests provided in Paragraph 5.03;

                        (iv) As soon as available and in no event later than
                fifty (50) days after the last day of each fiscal quarter of
                Borrower, a certificate of the chief financial officer of
                Borrower which sets forth the calculation of the Funded
                Indebtedness/EBITDA Ratio for the consecutive four-quarter
                period ending on such day;

                        (v) As soon as possible and in no event later than five
                (5) Business Days after any Senior Officer of Borrower knows of
                the occurrence or existence of (A) any Reportable Event
                (excluding any Reportable Event for which the provision of a
                30-day notice to the PBGC has been waived by regulation) under
                any Employee Benefit Plan or Multiemployer Plan; (B) any actual
                or threatened litigation, suits, claims or disputes against
                Borrower or any of its Subsidiaries involving potential monetary
                damages payable by Borrower or its Subsidiaries of $10,000,000
                or more (alone or in the aggregate); (C) any other event or
                condition which is reasonably likely to have a Material Adverse
                Effect; or (D) any Default; the statement of the president or
                chief financial officer of Borrower setting forth details of
                such event, condition or Default and the action which Borrower
                proposes to take with respect thereto;

        (ii) deleting clause (vii) and (iii) changing the designations of
        clauses (viii), (ix) and (x) to "(vii)", "(viii)" and "(ix)",
        respectively.

                (i) Subparagraph 5.01(e) is amended to read in its entirety as
        follows:

                        (e) Governmental Charges and Other Indebtedness.
                Borrower and its Subsidiaries shall promptly pay and discharge
                when due (i) all taxes and other Governmental Charges prior to
                the date upon which penalties accrue thereon, (ii) all
                indebtedness which, if unpaid, could become a Lien upon the
                property of Borrower or its Subsidiaries and (iii) subject to
                any subordination provisions applicable thereto, all other
                indebtedness; except where (A) the failure to pay any such
                taxes, other Governmental Charges or indebtedness, either alone
                or collectively, is not reasonably likely to have a Material
                Adverse Effect and (B) any such taxes, other Governmental
                Charges or indebtedness as may in good faith



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                be contested or disputed, or for which arrangements for deferred
                payment have been made, provided that in each such case
                appropriate reserves as required by GAAP are maintained.

                (j) Subparagraph 5.02(a) is amended by changing clauses (ii) and
        (iii) to read in their entireties as follows:

                        (ii) Synthetic Lease Obligations, provided that the
                aggregate principal amount thereof (including the Outstanding
                Lease Amounts hereunder) outstanding at any time does not exceed
                $595,000,000;

                        (iii) Indebtedness of Borrower and its Subsidiaries
                listed in Schedule 5.02(a) and existing on April 13, 2001
                (including committed but undrawn amounts);

                (k) Subparagraph 5.02(b) is amended by changing clauses (ii) and
        (x) to read in their entireties as follows:

                        (ii) Liens securing the Synthetic Lease Obligations;

                        (x) Judgement Liens, provided that such Liens do not
                have a value in excess of $10,000,000 or such Liens are
                released, stayed, vacated or otherwise dismissed within twenty
                (20) days after issue or levy and, if so stayed, such stay is
                not thereafter removed;

                (l) Subparagraph 5.02(c) is amended by changing clause (vi) to
        read in its entirety as follows:

                        (vi) Sales or other dispositions of assets and property
                by Borrower to any of Borrower's Subsidiaries or by any of
                Borrower's Subsidiaries to Borrower or any of its other
                Subsidiaries, provided the terms of any such sales or other
                dispositions by or to Borrower (other than sales or other
                dispositions by Borrower to any of Borrower's wholly owned
                Subsidiaries or by any of Borrower's wholly owned subsidiaries
                to Borrower, except for sales or dispositions by Borrower which,
                either singly or in the aggregate with respect to all such sales
                or dispositions, would involve all or substantially all of the
                assets or property of Borrower or which would render Borrower
                incapable of performing its obligations under the Credit
                Documents) are on terms which are no less favorable to Borrower
                than would prevail in the market for similar transactions
                between unaffiliated parties dealing at arms length;

                (m) Subparagraph 5.02(d) is amended by changing clause (iii)(C)
        thereof to read in its entirety as follows:

                        (C) The aggregate cost of any such merger,
                consolidation, establishment or acquisition does not exceed the
                amounts permitted under clause (v) of Subparagraph 5.02(e)
                (except for Borrower's cost of acquiring Gasonics International
                Corporation, which shall not be subject to such limitation).

                (n) Subparagraph 5.02(e) is amended to read in its entirety as
        follows:



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                        (e) Investments. Neither Borrower nor any of its
                Subsidiaries shall make any Investment except for Investments in
                the following:

                                (i) Investments permitted by the investment
                        policy of Borrower duly approved by the Board of
                        Directors of Borrower and in effect at the time of such
                        Investment;

                                (ii) Investments held by Gasonics International
                        Corporation on the date Gasonics International
                        Corporation is acquired by Borrower;

                                (iii) Any transaction permitted by Subparagraph
                        5.02(a);

                                (iv) Investments by Borrower in the "Tranche A"
                        portion of synthetic leases in which it is the lessee
                        and which constitute Economically Defeased Synthetic
                        Lease Obligations;

                                (v) Investments in joint ventures and strategic
                        alliances, provided that the aggregate amount of such
                        Investments does not exceed in any fiscal year two and
                        one-half percent (2 1/2%) of the tangible assets of
                        Borrower and its Subsidiaries, determined on a
                        consolidated basis in accordance with GAAP, on the last
                        day of the immediately preceding fiscal year; and

                                (vi) Other Investments, provided that the
                        aggregate amount of such other Investments plus the
                        aggregate cost of all mergers and consolidations
                        consummated, Subsidiaries established and Subsidiaries
                        and assets acquired by Borrower pursuant to Subparagraph
                        5.02(d) (excluding Borrower's acquisition of Gasonics
                        International Corporation) does not exceed in any fiscal
                        year (A) $100,000,000 for any amounts paid in cash and
                        (B) $500,000,000 for any amounts paid with shares of
                        common stock of Borrower (as determined according to the
                        stock price of such shares on the date of transfer) and
                        accounted for on a pooling basis in accordance with
                        GAAP.

                (o) Paragraph 5.02 is further amended by (i) deleting
        Subparagraph 5.02(i) and (ii) changing the designation of Subparagraph
        5.02(j) to "(i)".

                (p) Paragraph 5.03 is amended to read in its entirety as
        follows:

                        5.03. Borrower's Financial Covenants. Until the
                termination of this Agreement and the satisfaction in full by
                Borrower of all Obligations, Borrower will comply, and will
                cause compliance, with the following financial covenants, unless
                Required Lenders shall otherwise consent in writing:

                                (a) Funded Indebtedness/Capital Ratio. Borrower
                        shall not permit its Funded Indebtedness/Capital Ratio
                        on any day set forth below to be greater than the ratio
                        set forth opposite such day below:

                             The last day of any
                                    fiscal quarter                 0.40 to 1.00.



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                                (b) Quick Ratio. Borrower shall not permit its
                        Quick Ratio on any day set forth below to be less than
                        the ratio set forth opposite such day below:

                             The last day of any
                                    fiscal quarter                 1.50 to 1.00.

                                (c) Debt Service Coverage Ratio. Borrower shall
                        not permit its Debt Service Coverage Ratio for any
                        fiscal quarter ending on any day set forth below to be
                        less than the ratio set forth opposite such day below:

                             The last day of any
                                    fiscal quarter                 3.50 to 1.00.

                                (d) Tangible Net Worth. Commencing on December
                        31, 2000, Borrower shall not permit its Tangible Net
                        Worth on the last day of any fiscal quarter (such date
                        to be referred to herein as a "determination date") to
                        be less than the sum on such determination date of the
                        following:

                                        (i) $664,477,000.00 (the approximate
                                amount of Borrower's Tangible Net Worth on
                                December 31, 1999);

                                      plus

                                        (ii) Seventy-five percent (75%) of the
                                sum of (A) Borrower's consolidated annual net
                                income for its fiscal year ending December 31,
                                2000 (ignoring any annual loss); plus (B) the
                                sum of Borrower's consolidated quarterly net
                                income (ignoring any quarterly losses) for each
                                fiscal quarter ending after December 31, 2000
                                through and including the fiscal quarter ending
                                on the determination date;

                                      plus

                                        (iii) One hundred percent (100%) of the
                                Net Proceeds of all Equity Securities issued by
                                Borrower and its Subsidiaries (to Persons other
                                than Borrower or its Subsidiaries) during the
                                period commencing on December 31, 1999 and
                                ending on the determination date;

                                      plus

                                        (iv) One hundred percent (100%) of the
                                principal amount of all debt securities of
                                Borrower and its Subsidiaries converted into
                                Equity Securities of Borrower and its
                                Subsidiaries during the period commencing on
                                December 31, 1999 and ending on the
                                determination date.

                        provided, however, that in no case shall Borrower permit
                        its Tangible Net Worth on December 31, 2000 to be less
                        than $1,260,000,000.00.



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                                (e) Minimum Cash Balances. Borrower shall not
                        permit its Cash Balances on any date to be less than the
                        remainder of:

                                        (i) The aggregate amount on such date of
                                all Synthetic Lease Obligations of Borrower and
                                its Subsidiaries that (A) would be attributable
                                to principal if such obligations were treated as
                                loan obligations and (B) become due within one
                                (1) year of such date;

                                      minus

                                        (ii) The sum of (A) all cash of Borrower
                                and its Subsidiaries on such date and (B) the
                                market value of Cash Equivalents and short-term
                                marketable securities (that are classified as
                                current assets in accordance with GAAP) of
                                Borrower and its Subsidiaries on such date to
                                the extent such cash, Cash Equivalents and
                                short-term marketable securities secure payment
                                of the current Synthetic Lease Obligations
                                referred to in clause (i) above.

                        (In calculating the market value of Cash Equivalents and
                        short-term marketable securities under this
                        subparagraph, Cash Equivalents and short-term marketable
                        securities shall be marked to market quarterly.)

                (q) Subparagraphs 6.01(e) and 6.01(h) are amended by changing
        the amount "$2,500,000" wherever it appears therein to "$10,000,000".

                (r) Paragraph 8.01 is amended by changing the notice addresses,
        etc. for Borrower and Agent set forth therein to read in their
        entireties as follows:

                      Borrower:     Novellus Systems, Inc.
                                    4000 North First Street
                                    San Jose, CA 95134
                                    Attn:  Treasurer
                                    Telephone:  (408) 432-5339
                                    Fax No: (408) 545-3009

                      Agent:        ABN AMRO Bank N.V.
                                    Agency Services
                                    208 South LaSalle Street, Suite 1500
                                    Chicago, IL 60604
                                    Attn: Josephine O'Brien
                                    Telephone: (312) 992-5091
                                    Fax: (312) 992-5157

                                    with copies to:

                                    ABN AMRO Bank N.V.
                                    101 California Street, Suite 4550
                                    San Francisco, CA 94111-5812



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<PAGE>   11

                                    Attn: Joe Endoso
                                    Telephone: (415) 984-3718
                                    Fax: (415) 362-3524

                                    and

                                    ABN AMRO Bank N.V.
                                    Credit Administration
                                    208 South LaSalle Street, Suite 1500
                                    Chicago, IL 60604
                                    Attn:  Gregory Miller
                                    Telephone:  (312) 992-5116
                                    Fax:  (312) 992-5111

                (s) Schedules 4.01(g) and 5.02(e) are deleted.

                (t) Schedule 5.02(a) is amended to read in its entirety as set
        forth in the counterpart schedule hereto.

                (u) Exhibits A and B are hereby amended by changing the notice
        address appearing therein to the following:

                      ABN AMRO Bank N.V.,
                            as Agent
                      Agency Services
                      208 South LaSalle Street, Suite 1500
                      Chicago, IL  60604
                      Attn:  Josephine O'Brien

        3. REPRESENTATIONS AND WARRANTIES. Borrower hereby represents and
warrants to Agent and the Lenders that the following are true and correct on the
date of this Amendment and that, after giving effect to the amendments set forth
in Paragraph 2 above, the following will be true and correct on the Effective
Date (as defined below):

                (a) The representations and warranties of Borrower set forth in
        Paragraph 4.01 of the Credit Agreement and in the other Credit Documents
        are true and correct in all material respects as if made on such date
        (except for representations and warranties expressly made as of a
        specified date, which shall be true as of such date);

                (b) No Default has occurred and is continuing; and

                (c) All of the Credit Documents are in full force and effect.

(Without limiting the scope of the term "Credit Documents," Borrower expressly
acknowledges in making the representations and warranties set forth in this
Paragraph 3 that, on and after the date hereof, such term includes this
Amendment.)

        4. EFFECTIVE DATE. Borrower shall deliver to Agent a written notice
specifying the effective date for this Amendment ("Effective Date"), which date
shall be a Business Day prior to April 27, 2001. Borrower shall deliver such
notice to Agent at least five (5) Business Days



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<PAGE>   12

prior to the Effective Date. The amendments effected by Paragraph 2 above shall
then become effective on the Effective Date, subject to receipt by , Agent and
Required Lenders, on or prior to such date, of the following, each in form and
substance satisfactory to Agent, Required Lenders and their respective counsel:

                (a) This Amendment duly executed by Borrower, Required Lenders
        and Agent;

                (b) A certificate of the Chief Financial Officer or Treasurer of
        Borrower, addressed to Agent and dated the Effective Date, certifying
        that:

                        (1) The representations and warranties set forth in
                Paragraph 4.01 of the Credit Agreement and in the other Credit
                Documents are true and correct in all material respects as of
                such date (except for such representations and warranties made
                as of a specified date, which shall be true as of such date);

                        (2) No Default has occurred and is continuing as of such
                date;

                        (3) All of the Credit Documents are in full force and
                effect on such date;

                (c) A favorable written opinion of Morrison & Foerster, LLP,
        counsel to Borrower, dated the Effective Date, addressed to Agent for
        the benefit of , Agent and the Lenders, covering such legal matters as
        Agent may reasonably request and otherwise in form and substance
        satisfactory to Agent;

                (d) An amendment fee for each Lender that executes this
        Amendment on or prior to April 13, 2001 equal to 0.125% of such Lender's
        Commitment on the Effective Date;

                (e) All fees and expenses payable to the Parties on or prior to
        the Effective Date (including all Agent's Fees);

                (f) All fees and expenses of Agent's counsel through the
        Effective Date, to the extent set forth in statements of such counsels
        delivered to Borrower one or more days prior to the Effective Date; and

                (g) Such other evidence as , Agent or any Lender may reasonably
        request to establish the accuracy and completeness of the
        representations and warranties and the compliance with the terms and
        conditions contained in this Amendment and the other Credit Documents.

        5. EFFECT OF THIS AMENDMENT. On and after the Effective Date, each
reference in the Credit Agreement and the other Credit Documents to the Credit
Agreement shall mean the Credit Agreement as amended hereby. Except as
specifically amended above, (a) the Credit Agreement and the other Credit
Documents shall remain in full force and effect and are hereby ratified and
affirmed and (b) the execution, delivery and effectiveness of this Amendment
shall not, except as expressly provided herein, operate as a waiver of any
right, power, or remedy of the Lenders or Agent, nor constitute a waiver of any
provision of the Credit Agreement or any other Credit Document.



                                       12
<PAGE>   13

        6. MISCELLANEOUS.

                (a) Counterparts. This Amendment may be executed in any number
        of identical counterparts, any set of which signed by all the parties
        hereto shall be deemed to constitute a complete, executed original for
        all purposes.

                (b) Headings. Headings in this Amendment are for convenience of
        reference only and are not part of the substance hereof.

                (c) Governing Law. This Amendment shall be governed by and
        construed in accordance with the laws of the State of California without
        reference to conflicts of law rules.

                            [Signature pages follow]



                                       13
<PAGE>   14

        IN WITNESS WHEREOF, Borrower, Agent and Lenders have caused this
Amendment to be executed as of the day and year first above written.

BORROWER:                                   NOVELLUS SYSTEMS, INC.

                                            By:
                                               ---------------------------------
                                               Name:
                                                    ----------------------------
                                               Title:
                                                     ---------------------------


AGENT:                                      ABN AMRO BANK N.V.

                                            By:
                                               ---------------------------------
                                               Name:
                                                    ----------------------------
                                               Title:
                                                     ---------------------------


                                            By:
                                               ---------------------------------
                                               Name:
                                                    ----------------------------
                                               Title:
                                                     ---------------------------


LENDERS:                                    ABN AMRO BANK N.V.

                                            By:
                                               ---------------------------------
                                               Name:
                                                    ----------------------------
                                               Title:
                                                     ---------------------------


                                            By:
                                               ---------------------------------
                                               Name:
                                                    ----------------------------
                                               Title:
                                                     ---------------------------


                                            KEYBANK NATIONAL ASSOCIATION

                                            By:
                                               ---------------------------------
                                               Name:
                                                    ----------------------------
                                               Title:
                                                     ---------------------------


                                            THE SUMITOMO BANK, LIMITED

                                            By:
                                               ---------------------------------
                                               Name:
                                                    ----------------------------
                                               Title:
                                                     ---------------------------



                                       S-1
<PAGE>   15

                                            THE INDUSTRIAL BANK OF JAPAN,
                                            LIMITED, SAN FRANCISCO AGENCY

                                            By:
                                               ---------------------------------
                                               Name:
                                                    ----------------------------
                                               Title:
                                                     ---------------------------


                                            THE BANK OF NOVA SCOTIA

                                            By:
                                               ---------------------------------
                                               Name:
                                                    ----------------------------
                                               Title:
                                                     ---------------------------


                                            UNION BANK OF CALIFORNIA, N.A.

                                            By:
                                               ---------------------------------
                                               Name:
                                                    ----------------------------
                                               Title:
                                                     ---------------------------


                                            COMERICA BANK-CALIFORNIA

                                            By:
                                               ---------------------------------
                                               Name:
                                                    ----------------------------
                                               Title:
                                                     ---------------------------


                                            FLEET NATIONAL BANK

                                            By:
                                               ---------------------------------
                                               Name:
                                                    ----------------------------
                                               Title:
                                                     ---------------------------


                                            BANQUE NATIONALE DE PARIS

                                            By:
                                               ---------------------------------
                                               Name:
                                                    ----------------------------
                                               Title:
                                                     ---------------------------



                                      S-2
<PAGE>   16

                                            CREDIT LYONNAIS LOS ANGELES BRANCH

                                            By:
                                               ---------------------------------
                                               Name:
                                                    ----------------------------
                                               Title:
                                                     ---------------------------


                                            THE FUJI BANK, LIMITED

                                            By:
                                               ---------------------------------
                                               Name:
                                                    ----------------------------
                                               Title:
                                                     ---------------------------


                                            GENERAL ELECTRIC CAPITAL CORPORATION

                                            By:
                                               ---------------------------------
                                               Name:
                                                    ----------------------------
                                               Title:
                                                     ---------------------------


                                            THE MITSUBISHI TRUST AND BANKING
                                            CORPORATION, LOS ANGELES AGENCY

                                            By:
                                               ---------------------------------
                                               Name:
                                                    ----------------------------
                                               Title:
                                                     ---------------------------


                                            SOCIETE GENERALE

                                            By:
                                               ---------------------------------
                                               Name:
                                                    ----------------------------
                                               Title:
                                                     ---------------------------


                                            CALIFORNIA BANK & TRUST, formerly
                                            known as "The Sumitomo Bank of
                                            California"

                                            By:
                                               ---------------------------------
                                               Name:
                                                    ----------------------------
                                               Title:
                                                     ---------------------------



                                      S-3
<PAGE>   17

                                            WELLS FARGO BANK, N.A.

                                            By:
                                               ---------------------------------
                                               Name:
                                                    ----------------------------
                                               Title:
                                                     ---------------------------


                                            SANWA BANK CALIFORNIA

                                            By:
                                               ---------------------------------
                                               Name:
                                                    ----------------------------
                                               Title:
                                                     ---------------------------



                                      S-4
<PAGE>   18

                                SCHEDULE 5.02(a)

                              EXISTING INDEBTEDNESS


<TABLE>
<CAPTION>
FINANCIAL INSTITUTION              CURRENCY                AMOUNT           FACILITY TYPE
---------------------              --------                ------           -------------
<S>                                <C>                <C>              <C>
Bank of Tokyo Mitsubishi             JPY              1,300,000,000        Line of Credit
Bank of Tokyo Mitsubishi             JPY                520,000,000        Line of Credit
Sanwa Bank                           JPY              2,400,000,000        Line of Credit
Sumitomo Bank                        JPY                500,000,000        Line of Credit
ABN AMRO Bank                        USD                     97,000          Standby L/C
Malayan Banking Berhad                RM                     30,000    Bank Guarantee Facility
</TABLE>



                                   5.02(a)-1