Exhibit 10.12

                                 PROMISSORY NOTE


$700,000                                                    April 29, 2002


     FOR VALUE RECEIVED, Brad Mattson (the "undersigned") promises to pay to
Mattson Technology, Inc. (the "Company"), or order, the principal sum of Seven
Hundred Thousand Dollars ($700,000) on or before the later of (i) August 31,
2002 and (ii) the date which is ninety days after the date that the Securities
and Exchange Commission declares effective that certain registration statement
on Form S-3 (File No. 333-86072), filed by the Company with the Securities and
Exchange Commission on April 12, 2002 ("Due Date"). Such principal sum shall not
bear interest. The entire outstanding balance of principal shall be due and
payable on the Due Date.

     The undersigned agrees that until this Note is repaid in full, he shall not
sell, pledge or otherwise transfer or dispose of any Company common stock in any
manner except as required to (i) transfer 1,000,000 shares to Diane Mattson as
part of a Marriage Settlement Agreement, or (ii) sell shares after the end of
the lock-up period as necessary to repay the principal due under this note. In
the event of any other disposition, including any disposition relating to a
merger or acquisition involving the Company, this Note shall be immediately due
and payable and all proceeds relating to any such transactions shall be applied
to the repayment of this Note.

     The Company may at its option accelerate, in whole or in part, the maturity
of the outstanding principal balance due on this Note and any accrued interest
thereon upon the occurrence of any of the following events:

     (1)  A default in the payment of any installment of principal when due;

     (2)  The undersigned becomes insolvent; and

     (3)  The commencement by the undersigned of any proceeding under any
          provision of the United States Bankruptcy Code, as amended, or under
          any other bankruptcy or insolvency law, including assignments for the
          benefit of creditors, formal or informal moratoria, compositions,
          extension generally with creditors, or proceedings seeking
          reorganization, arrangement, or other relief (collectively, an
          "Insolvency Proceeding"), or the commencement against the undersigned
          of an Insolvency Proceeding that is not dismissed or stayed within
          thirty (30) days.



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     The undersigned waives demand, presentment, notice of protest, notice of
demand, dishonor, diligence in collection and notices of intention to accelerate
maturity. The Company may automatically effectuate any such acceleration by
making an entry to such effect in its records, in which event the unpaid balance
on this Note shall become immediately due and payable without demand or notice.

     Principal is payable in lawful money of the United States of America. The
undersigned may prepay any amount due hereunder, without premium or penalty.

     In the event the Company incurs any costs or fees in order to enforce
payment of this Note or any portion thereof, the undersigned agrees to pay to
the Company, in addition to such amounts as are owed pursuant to this Note, such
costs and fees, including, without limitation, a reasonable sum for attorneys'
fees.

     The undersigned hereby waives to the full extent permitted by law all
rights to plead any statute of limitations as a defense to any action hereunder.

     The failure of the Company to exercise any of the rights created hereby, or
to promptly enforce any of the provisions of this Note, shall not constitute a
waiver of the right to exercise such rights or to enforce any such provisions.

     This Note is made under and shall be construed in accordance with the laws
of the State of California, without regard to the conflict of law provisions
thereof.

     The undersigned agrees to execute and deliver any documents requested by
the Company in order to enforce its rights hereunder.



                                       ---------------------------------
                                       Brad Mattson











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