<PAGE>   1

                                                                    Exhibit 10.5

The omitted portions indicated by brackets have been separately filed with the
Securities and Exchange Commission pursuant to a request for confidential
treatment under Rule 406, promulgated under the Securities Act of 1933, as
amended.



                       FUMED METAL OXIDE SUPPLY AGREEMENT


       This FUMED METAL OXIDE SUPPLY AGREEMENT (this "Agreement"), executed this
20th day of January, 2000, is between Cabot Corporation ("Cabot"), a Delaware
corporation, and Cabot Microelectronics Corporation ("CMC"), a Delaware
corporation. Notwithstanding the execution date hereof, this Agreement shall
become effective upon the date of the initial public offering by CMC of shares
of CMC common stock.

       WHEREAS, Cabot and certain of its subsidiaries and CMC will be parties to
a Master Separation Agreement, (the "Master Separation Agreement"), which will
provide, in part, for the separation from Cabot, of the business, assets and
liabilities of the Microelectronics Materials Division of Cabot (the "MMD
Business") and the transfer of the MMD Business to CMC;

       WHEREAS, in the past, the Microelectronics Materials Division of Cabot
has purchased various fumed metal oxide products from Cabot;

       WHEREAS, CMC desires to have Cabot provide to CMC certain fumed metal
oxide products after the separation of the MMD Business; and

       WHEREAS, Cabot desires to provide such fumed metal oxides to CMC after
the separation of the MMD Business;

       NOW, THEREFORE, in consideration of the foregoing premises and other good
and valuable consideration, the receipt and sufficiency of which is hereby
acknowledged, the parties hereby agree as follows:

SECTION 1.        TERM

       This Agreement shall commence on the date of the initial public offering
by CMC of shares of CMC common stock, and shall continue until June 30, 2005
(the "Initial Term"). Unless either party shall give a notice of nonrenewal
prior to December 31, 2003, this Agreement shall continue after the Initial Term
until terminated by either party by a written notice of termination, which shall
terminate this Agreement effective on the first June 30 or December 31 more than
18 months after the date such notice is delivered. The Initial Term, together
with any continuations, are referred to herein as the "Term". Each year of the
Term beginning on the effective date or an anniversary thereof is referred to
herein as a "Term Year", including the stub period, if any, between the last
anniversary of the effective date and the end of the Term.


<PAGE>   2

SECTION 2.        PRODUCTS

      2.1   Purchase and Sale.

      (a) Subject to the terms and conditions of this Agreement, during the
Term, Cabot shall provide to CMC, and CMC shall purchase from Cabot, the
Products (as defined below) in such quantities as specified by CMC, subject to
Sections 2.3 through 2.5 below. "Products" means:

      (i)   the fumed silica of the types set forth on Schedule A hereto (the
            "Fumed Silica"), which shall conform to the specifications, formulae
            and processes set forth on Schedule A hereto; and

      (ii)  the fumed alumina of the types set forth on Schedule B hereto (the
            "Fumed Alumina" and together with the Fumed Silica, the "Fumed Metal
            Oxides"), which shall conform to the specifications, formulae and
            processes set forth on Schedule B hereto.

      (b) Any amendment to Schedule A or Schedule B shall require the consent of
both CMC and Cabot. Unless otherwise agreed to by Cabot, any increase in costs
incurred by Cabot in manufacturing Products to comply with changes requested by
CMC to the specifications as set forth on Schedule A or Schedule B shall be paid
by CMC.

      2.2 Forecasts.

      CMC shall provide Cabot with forecasts (the "Forecasts") of the quantities
of Fumed Metal Oxides that CMC expects to purchase from Cabot (the "Forecasted
Quantities"). The Forecasts shall identify by grade, the Forecasted Quantities
and the Cabot facility or facilities that will produce and deliver to CMC such
Forecasted Quantities (including the volume to be made at each plant). CMC shall
provide the following Forecasts to Cabot:

     (a) not more than sixty (60) but not less than thirty (30) days prior to
each January 1, April 1, July 1 and October 1 during the Term, a Forecast
indicating the Forecasted Quantity for each month of the calendar quarter
commencing on such January 1, April 1, July 1 and October 1 (the "Quarterly
Forecast"); provided, however, that in such Quarterly Forecast, the Forecasted
Quantity for any month may not exceed the Forecasted Quantity for the previous
month by more than 20%;

     (b) not more than sixty (60) but not less than thirty (30) days prior to
each July 1 and January 1 during the Term, a semi-annual Forecast indicating the
Forecasted Quantity for the six (6) month period commencing on such July 1 and
January 1 (the "Six Month Forecast");



                                      -2-
<PAGE>   3

        (c) not more than sixty (60) but not less than thirty (30) days prior to
each July 1, a one (1) year Forecast indicating the Forecasted Quantity for the
calendar year commencing on the following July 1 (the "Annual Forecast"); and

        (d) on or around each July 1, an eighteen (18) month Forecast indicating
the Forecasted Quantity for the eighteen month period commencing on the
following July 1 (the "18 Month Forecast"); provided, however, that CMC shall
provide Cabot with a revised eighteen (18) Month Forecast for the remainder of
the eighteen (18) month period covered by the last 18 Month Forecast as soon
reasonably practicable after CMC becomes aware of any material changes to such
18 Month Forecast.

        For the purposes of this Agreement, Forecasts delivered by CMC to Cabot
after the execution hereof shall, upon the effectiveness of this Agreement, be
deemed to have been delivered hereunder.

        With respect to planned shutdowns of Cabot's manufacturing facilities,
the parties shall work together and cooperate with each other regarding
necessary adjustments to forecasts and delivery schedules hereunder.

      2.3   Cabot's Maximum Supply Obligations.

      (a) The obligation of Cabot to supply Products to CMC under this Agreement
shall be subject to each of the following maximum monthly volume limitations:

     (i) the maximum monthly volume of Fumed Silica from Cabot's Tuscola,
         Illinois facility (the "Tuscola Plant") shall be [ ] pounds per month;

     (ii)the maximum monthly volume of Fumed Alumina from Cabot's Tuscola,
         Illinois pilot facility (the "Tuscola Pilot Plant") shall be [ ] pounds
         per month; and

     (iii) the maximum monthly volume of Fumed Silica from Cabot's Barry, Wales
         facility (the "Barry Plant") shall be [ ] pounds per month.

     In clarification of the above, any volumes of Fumed Silica and/or Fumed
     Alumina supplied by Cabot under the Dispersions Services Agreement, of even
     date herewith, shall not be considered in calculating the maximum volumes
     of Fumed Silica and/or Fumed Alumina Cabot is obligated to supply
     hereunder.

      (b) In addition to the volume limitations set forth in 2.3(a) above, in
the event that CMC orders volumes of fumed silica from Cabot in excess of
Forecasted Quantities, Cabot shall not be obligated to supply to CMC such
Products in excess of the following volumes:


                                      -3-
<PAGE>   4


      (i)   for any calendar quarter and any plant, [ ]% of the volumes of Fumed
            Silica for such plant set forth in CMC's Quarterly Forecast;

      (ii)  for any calendar half year (beginning on or after July 1, 2000) and
            for any plant, [ ]% of the volumes of Fumed Silica for such plant
            set forth in CMC's Sixth Month Forecast; and

      (iii) for any year beginning July 1 and for any plant, [ ]% of the volumes
            of Fumed Silica for such plant set forth in CMC's Annual Forecast.

      (c) The maximum supply obligations set forth in Sections 2.3 (a) and (b)
are referred to herein as the "Maximum Volumes". If CMC shall request volumes of
Fumed Silica or Fumed Alumina in excess of the Maximum Volumes described above,
Cabot shall use commercially reasonable efforts to supply such volumes ("Excess
Volumes"); provided that Cabot shall not be obligated to breach its contractual
obligations with other customers or to take any actions which it deems
detrimental to its business, in order to supply CMC with Excess Volumes.

      2.4 Minimum Volumes. CMC shall be obligated to purchase from Cabot during
each six month period covered by a Six Month Forecast a "Minimum Volume,"
meaning at least 90% of the aggregate volumes of Fumed Silica forecasted to be
purchased by CMC as set forth in each Six Month Forecast. Cabot and CMC
recognize that damages for CMC's failure to purchase Minimum Volumes would be
difficult to ascertain and prove. Cabot and CMC agree that if, during any six
month period CMC fails to purchase from Cabot the Minimum Volume of Fumed Silica
for such six month period, CMC shall pay to Cabot liquidated damages in an
amount equal to the product obtained by multiplying (i) the difference (in
pounds) between (x) the applicable Minimum Volume and (y) the amount of Fumed
Silica actually purchased by CMC during the relevant six month period times (ii)
$[ ]. Cabot and CMC agree that such liquidated damages are the sole and
exclusive remedy for CMC's failure to purchase Minimum Volumes. Cabot and CMC
further agree that such liquidated damages represent a reasonable estimate of
Cabot's damages and do not constitute a penalty.

      2.5 Exclusivity; Exception Thereto.

       (a) CMC shall purchase from Cabot all of the Fumed Metal Oxides necessary
to produce the products produced by CMC on the effective date of this Agreement.
With respect to products developed and produced by CMC after the effective date
of this Agreement, CMC shall not be obligated to purchase from Cabot any of the
Fumed Metal Oxides necessary to produce such products.

       (b) During the Term of this Agreement, Cabot shall not knowingly, without
CMC's prior written consent, directly or indirectly, sell any Fumed Metal Oxides
to any

                                      -4-
<PAGE>   5

person or entity other than CMC for use in the production of any goods or
products that compete with any CMP (chemical mechanical polishing) consumable
goods and products produced by CMC.

       (c) In the event CMC requests a change to a Product specification, which
change is necessary in order to achieve a material performance difference in
CMC's end product, and Cabot is not able or is unwilling to modify such Product,
CMC shall have the right to obtain such modified product from any third party,
subject to any intellectual property rights Cabot may have.

       (d) Notwithstanding Section 2.5(a) above, in the event that Cabot fails
to supply CMC with its requirements for Products for any reason, CMC shall have
the right to obtain such Products from any third party, subject to any
intellectual property rights Cabot may have.

SECTION 3.        PRICING

      3.1 Prices. Cabot shall sell the Products to CMC in accordance with the
following prices (the "Prices"):

      (a)   Fumed Silica Price.

            The price for Fumed Silica shall be equal to the Base Price (as
defined below) plus the Feedstock Adjustment (as defined below). The price of
Fumed Silica to be purchased shall be determined by the date the order therefor
is placed with Cabot, with respect to all volumes specified therein to be
delivered within 90 days after the date such order is placed, and by the date
specified for delivery, with respect to all volumes specified for delivery
thereafter.

            The "Base Price" shall be $[ ] per pound during the first Term Year.
The Base Price shall increase by $[ ] per pound for each subsequent Term Year,
to be effective commencing on the first day of each subsequent Term Year.

      The "Feedstock Adjustment" shall be calculated and applied every six (6)
months and is obtained by (i) calculating the difference between the New
Feedstock Cost per pound of fumed silica manufactured (as defined below) and the
Starting Feedstock Cost per pound of fumed silica manufactured (as defined
below) and (ii) dividing this difference by a yield factor of [ ], provided that
if the New Feedstock Cost is less than the Starting Feedstock Cost, the
Feedstock Adjustment shall be zero. The Feedstock Adjustment shall be calculated
and provided to CMC prior to each July1 and January 1 with respect to the
following six (6) month period and shall be based on CMC's Six Month Forecast
for such period as well as the historical feedstock cost information for the
most recent six month period ended May 31 (in the case of the July 1 adjustment)
and

                                      -5-
<PAGE>   6

November 30 (in the case of the January 1 adjustment).


            The "New Feedstock Cost" shall be derived from the following
formula:

            New Feedstock Cost = [     ]

                  Where:

                  A = pounds of fumed silica forecasted to be purchased by CMC
                  in the upcoming Six Month Forecast from the Tuscola plant.
                  B = pounds of fumed silica forecasted to be purchased by
                  CMC in the upcoming Six Month Forecast from the Barry plant.
                  C = Total "Delivered Cost" of all [ ] (other than [ ] used
                  in [ ] manufacturing) consumed in the manufacture of fumed
                  silica at the Tuscola plant during the applicable six (6)
                  month period divided by the total number of pounds of fumed
                  silica produced at the Tuscola plant (other than [ ] which was
                  toll manufactured), including off-quality material. As used
                  herein, the "Delivered Cost" of [ ] means the purchase price
                  paid by Cabot for such [ ], including transportation costs and
                  applicable sales and use taxes as well as price adjustments
                  related solely to the [ ], and excluding [ ] adjustments or
                  credits and handling costs, labor and depreciation.
                  D = Total "Delivered Cost" of all [ ] (other than [ ] used in
                  [ ] manufacturing) consumed in the manufacture of fumed
                  silica at the Barry plant during the applicable six (6) month
                  period divided by the total number of pounds of fumed silica
                  produced at the Barry plant (other than [ ] which was toll
                  manufactured), including off-quality material.

            The "Starting Feedstock Cost" shall equal the total "Delivered Cost"
of all [ ] (other than [ ] used in [ ] manufacturing) consumed at the Tuscola
and Barry plant during the six (6) month period ended November 30, 1999 divided
by the total number of pounds of fumed silica produced at the Tuscola and Barry
plant (other than [ ] which was toll manufactured), including off-quality
material, during such period.

            CMC shall have the right to have a recognized accounting firm audit
the books and records of Cabot necessary to verify the Feedstock Adjustment
provided above. Such accounting firm shall be obligated to keep any information
obtained during the audit of Cabot's books and records confidential and may
confirm to CMC only

                                      -6-
<PAGE>   7

whether, and to what extent, Cabot's calculations of the Feedstock Adjustment
deviate from the calculation of such accounting firm.

      (b) Excess Volumes of Fumed Silica. The price for Excess Volumes of Fumed
Silica shall be as follows:

            (1) Subject to Section 2.3(c) above, if Cabot has the production
capacity to produce the Excess Volumes of Fumed Silica at the times and in the
volumes requested by CMC without interfering with its supply of products for
other customers, Cabot shall produce such Excess Volumes and sell them to CMC at
the prices set forth in Section 3.1(a) hereof.

            (2) Subject to Section 2.3(c) above, if Cabot would be required to
displace volumes intended for other customers, otherwise interfere with its
supply of products to other customers or obtain Products from other sources in
order to meet a request of CMC in respect of Excess Volumes of Fumed Silica, the
price for such Excess Volumes shall be determined by Cabot, provided that such
price shall not exceed [ ].

      (c)   Fumed Alumina Price.

      Until Cabot shall begin commercial scale production of fumed alumina, the
price for fumed alumina shall be equal to $[ ] per pound. For purposes of this
agreement, "commercial scale production of fumed alumina" shall mean Cabot
having a fumed alumina production unit capable of producing fumed alumina at a
production rate greater than [ ] pounds per year. Upon commencement by Cabot of
such commercial scale production of fumed alumina, Cabot and CMC shall
renegotiate the price per pound of Fumed Alumina.

      (d) In addition to the above described purchase prices for the fumed metal
oxides, MMD shall reimburse Cabot for all reasonable costs incurred by Cabot in
conducting analytical services requested by CMC for [ ].

      3.2 Cost Savings. Cabot and CMC acknowledge that it is their intention to
decrease the costs associated with manufacturing the Products, and to share any
cost savings resulting from joint efforts equally between them (other than cost
savings with respect to packaging, which the parties agree shall not be passed
on to CMC). Cabot and CMC agree to discuss, from time to time, ways to jointly
decrease such costs.

SECTION 4.        ORDERS, SHIPPING, DELIVERY AND PAYMENT

      (a) Orders for Products shall be issued by CMC from time to time. Each
order shall specify the date(s) the products are to be delivered, which date(s)
shall be not less than ten (10) business days prior to the date the order is
received by Cabot. For purposes

                                      -7-
<PAGE>   8

of applying 2.3 and 2.4 only, each volume of Product shall be deemed to be in
the month specified for its shipment in CMC's order; and if no date is
specified, then in the month following the month in which the order therefor is
issued by CMC.

      (b) All sales of Products under this agreement are made F.O.B. Cabot's
point of shipment. CMC shall be responsible for all transportation costs and
title and risk of loss shall pass to CMC upon delivery to carrier.

      (c) All Products shall be prepared by Cabot for delivery to CMC, as the
case may be, including the necessary dunnage, to prevent damage during the
normal course of transportation.

      (d) Cabot shall invoice CMC for the Products delivered to CMC during each
month by the fifteenth (15th) calendar day of the following month. Cabot shall
deliver such invoices to CMC by regular U.S. mail, or other methods such as
express U.S. mail, overnight courier or other means, if mutually acceptable.

      (e) CMC shall pay each such invoice within fifteen (15) calendar days of
receipt thereof. Such payment shall be made by check or wire transfer in readily
available same day or next day funds denominated in United States dollars. If
payment is to be made by wire transfer, CMC shall request and Cabot shall
provide to CMC, wire transfer instructions.

SECTION 5.        WARRANTIES

      5.1 Warranty as to Products. Cabot represents and warrants to CMC that,
when shipped to CMC, the Products will conform in all respects to the
specifications then in effect and as then set forth in the materials specified
on Schedule A and Schedule B hereto. CABOT MAKES NO OTHER REPRESENTATION OR
WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, AS TO MERCHANTABILITY, FITNESS FOR A
PARTICULAR PURPOSE OR ANY OTHER MATTER WITH RESPECT TO THE PRODUCTS, WHETHER
USED ALONE OR IN COMBINATION WITH OTHER SUBSTANCES, EVEN IF THE PURPOSES OR USES
OF SUCH PRODUCTS ARE KNOWN BY CABOT.

      5.2 Remedies. If any Products do not conform in all respects to the
specifications then in effect and as then set forth on Schedule A and Schedule B
hereto, Cabot agrees to replace such Products with Products that conform to such
specifications. Subject to the following sentence, CMC shall not be obligated to
accept or pay for Products that do not conform to the specifications then in
effect for such Products. If any such non-conformity is the result of materials,
process specifications or formulae provided by CMC to Cabot, CMC shall pay Cabot
for the Products and such volumes

                                      -8-
<PAGE>   9

shall be included in determining the volumes of Products delivered by Cabot to
CMC hereunder. IN NO EVENT SHALL CABOT BE RESPONSIBLE OR LIABLE FOR ANY SPECIAL,
INCIDENTAL OR CONSEQUENTIAL DAMAGES ARISING AS A RESULT OF ANY BREACH OF
WARRANTY IN RESPECT OF ANY PRODUCTS UNDER THIS AGREEMENT OR THE TRANSACTIONS
CONTEMPLATED HEREBY.

SECTION 6.        CONSENTS; NOTICES

      Unless otherwise set forth herein, whenever any notice, consent or
approval is to be given in this Agreement, it must be in writing and delivered
in accordance with the provisions of this Section 6. Any such writing will be
duly given upon delivery, if delivered by hand, facsimile transmission or mail,
to the following addresses:

      If to Cabot:            Cabot Corporation
                              Business and Technical Center
                              Billerica, MA 01821
                              Attn: Fumed Metal Oxide Product Line Manager
                              Telecopier:

                        With a copy to:

                              Cabot Corporation
                              75 State Street
                              Boston, MA 02109
                              Attn: Law Department
                              Telecopier: 617-342-6039



      If to CMC:              Cabot Microelectronics Corporation
                              870 North Commons Drive
                              Aurora, IL 60504
                              Attn:  Vice President of Operations
                              Telecopier:  630-375-5596

or to such other address as may be designated in writing by any of the parties
from time to time in accordance herewith.

SECTION 7.        GENERAL

      7.1 Severability. If any provision of this Agreement shall be found to be
invalid or unenforceable, then such provision or provisions shall not invalidate
or in any way affect the enforceability of the remainder of this Agreement and
such provision or

                                      -9-
<PAGE>   10

provisions shall be curtailed and limited to the extent necessary to bring the
Agreement within any legal requirement and the parties shall negotiate in good
faith with respect to an equitable modification of the provision or application
thereof held to be invalid.

      7.2 Modification; Waivers. Except as expressly provided herein, this
Agreement may be modified or amended only with the written consent of each party
hereto. Neither party hereto shall be released from its obligations hereunder
without the written consent of the other party. The observance of any term of
this Agreement may be waived (either generally or in a particular instance and
either retroactively or prospectively) by the party entitled to enforce such
term, but any such waiver shall be effective only if in a writing signed by the
party against which such waiver is to be asserted. Except as otherwise
specifically provided herein, no delay on the part of either party hereto in
exercising any right, power or privilege hereunder shall operate as a waiver
thereof, nor shall any waiver on the part of either party hereto of any right,
power or privilege hereunder operate as a waiver of any other right, power or
privilege hereunder nor shall any single or partial exercise of any right, power
or privilege hereunder preclude any other or further exercise thereof or the
exercise of any other right, power or privilege hereunder.

      7.3 Succession. This Agreement shall be binding upon and shall inure to
the benefit of the parties hereto and their respective successors and other
legal representatives and, to the extent that any assignment hereof is permitted
hereunder, their assignees.

      7.4 Counterparts. This Agreement may be executed in counterparts.

      7.5 Further Assurances. Each party agrees to provide any additional
documents and take any such further action as may be reasonably requested by the
other party in order to carry out the purpose and intent of this Agreement.

      7.6 Entire Agreement. This Agreement contains the full and complete
undertaking and agreement between the parties hereto with respect to the sale of
fumed silica and fumed alumina by Cabot to CMC, and supersedes all other
agreements between Cabot and CMC, whether written or oral, except any
confidentiality agreements between the parties, which shall, to the extent such
agreements do not contradict the terms of this Agreement, continue in effect.

      7.7 Headings. The headings of the sections and other subdivisions of this
Agreement are for convenient reference only. They shall not be used in any way
to govern, limit, modify, construe this Agreement or any part or provision
thereof nor otherwise be given any legal effect.

      7.8 Assignees and Third Parties. This Agreement may not be assigned by
either party without the prior written consent of the other party and any
attempted

                                      -10-
<PAGE>   11

assignment without such consent shall be null and void; provided, however, that
Cabot may assign this Agreement to a subsidiary or affiliated company. In
addition, Cabot may make arrangements for the production and sale of Products
required hereunder to be manufactured and sold by a subsidiary or an affiliate,
including but not limited to Cabot Carbon Ltd. Such arrangements may take the
form of an assignment of certain rights and obligations hereunder or a
subcontract of certain obligations hereunder. Similarly, CMC may make
arrangements for the purchase of Products hereunder to be made by a subsidiary,
including but not limited to Cabot Microelectronics International Corporation.
Such arrangements may take the form of an assignment of certain rights and
obligations hereunder. However, all sales of Products pursuant to any such
arrangement shall be governed by the terms of this Agreement.

      7.9 Governing Law. This Agreement shall be governed by and construed and
enforced in accordance with the laws of Delaware, without giving effect to
principles of conflicts or choice of laws of Delaware or of any other
jurisdiction.

      7.10 Force Majeure. Each of the parties hereto shall be excused from
delays in performing or from failure to perform hereunder to the extent that
such delays or failures result from causes beyond the reasonable control of such
party, including, but not limited to, forces of nature, acts of God, strikes,
lockouts, wars, blockades, insurrections, riots, epidemics, restraints or
requirements of any government or government agency, civil disturbances,
explosions, breakage or accident to machinery or lines of pipe, unavailability
of raw material or supplies, strandings, perils of the sea, the binding order of
any court or governmental authority which has been resisted in good faith by all
reasonable means, and other cause, whether of the kind enumerated or otherwise,
not reasonably within the control of the party claiming suspension. Failure to
prevent or settle any strike shall not be considered to be a matter within the
control of the party claiming suspension. However, in order to be excused from
delay or failure to perform, such party must act diligently to remedy the cause
of such delay or failure.

      7.11 Confidentiality. Each of Cabot and CMC agree to keep confidential and
not disclose, and shall cause their respective subsidiaries and affiliates to
keep confidential and not disclose, to any party or use for any purpose (other
than the performance of this Agreement), any proprietary or other confidential
information of the other party which is received pursuant to this Agreement
("Confidential Information"). Confidential Information shall be subject to the
restrictions of this paragraph only if it is marked as confidential or
proprietary or, if not disclosed in tangible form, the disclosing party notifies
the recipient of its confidential or proprietary nature prior to its disclosure.
For purposes of this Agreement, Confidential Information of a party does not
include, and a party and a party's subsidiaries and affiliates will have no
obligations under this provision with respect to, any information of the other
party or any subsidiary or affiliate of the other party (the other party and
subsidiaries and affiliates of the other party being referred

                                      -11-
<PAGE>   12

to as the "receiving party") which:

      (i) is already known to the receiving party from a source other than the
disclosing party as evidenced by competent proof thereof; or

      (ii) is or becomes publicly known through no wrongful act of the receiving
party (in which event the receiving party's obligations under this Agreement in
respect thereto shall terminate on the date such information enters the public
domain); or

      (iii) is rightfully received by the receiving party from a third party
without violation of any obligations of confidentiality owed by the third party
to the disclosing party; or

      (iv) is disclosed by the disclosing party to a third party without
restrictions on the third party's right to use or disclose such information; or

      (v) is independently developed by employees or consultants of the
receiving party without use of or reference to the disclosing party's
Confidential Information; or

      (vi) is approved for release by written authorization of the disclosing
party

      7.12 Independent Contractors. CMC and Cabot are each independent
contractors. Nothing herein contained shall be construed to place CMC and Cabot
in the relationship of principal and agent, master and servant, partners, or
joint venturers, and, except as otherwise set forth in this Agreement, neither
party shall have, expressly or by implication, the power to represent itself as
having any authority to make contracts in the name of or binding upon the other,
or to obligate or bind the other in any manner whatsoever.

      7.13 Resale Prohibition. The parties intend and agree that the fumed
silica and fumed alumina being sold hereunder to CMC is being sold solely for
the use by CMC and its subsidiaries in manufacturing their products.
Accordingly, CMC and its subsidiaries are prohibited from reselling any fumed
silica or fumed alumina purchased hereunder. However, in the event CMC
determines, in good faith, that the fumed metal oxides supplied hereunder, which
otherwise meet the specification set forth in Scheduled A or B, but which are
not fit for CMC's use in the manufacture of CMP slurries, CMC shall have the
right to resell such fumed metal oxides, provided, CMC first offers Cabot the
option to purchase such fumed metal oxides back from CMC at a price which is the
lower of (i) the price paid by CMC to Cabot for such material, or (ii) the price
at which CMC will resell such material.




                                      -12-
<PAGE>   13


      IN WITNESS WHEREOF, the parties hereto have executed this Agreement as a
sealed instrument and have delivered this Agreement as of the day and year first
above written.

                                     CABOT CORPORATION


                                     By:    /s/  Samuel W. Bodman
                                        --------------------------------------
                                        Name:  Samuel W. Bodman
                                        Title: Chief Executive Officer



                                     CABOT MICROLELECTRONICS CORPORATION


                                     By:     /s/ Matthew Neville
                                        --------------------------------------
                                        Name:  Matthew Neville
                                        Title: President and
                                               Chief Executive Officer


                                      -13-
<PAGE>   14

                                   Schedule A

                           Fumed Silica Specifications








Product                       Specification

[     ]                             [     ]

[     ]                             [     ]

[     ]                             [     ]





                                      -14-
<PAGE>   15

                                   Schedule B

                          Fumed Alumina Specifications








Product                       Specification

[     ]                             [     ]





                                      -15-