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                                                                   EXHIBIT 10.11
 
                              SEVERANCE AGREEMENT
                              -------------------

          This Severance Agreement is entered into as of this 30th day of
December, 1996 by and between Aseco Corporation, a Delaware corporation (the
"Company"), and Sebastian J. Sicari (the "Employee").

                                   Recitals:
                                   -------- 

          WHEREAS, the Employee is an executive officer of the Company; and

          WHEREAS, the Company and the Employee wish to provide for the payment
of certain severance compensation by the Company to the Employee in the event
the Employee's employment by the Company is terminated.

          NOW, THEREFORE, in consideration of the Employee's continued service
to the Company and other good and valuable consideration, the receipt and
sufficiency of which are hereby acknowledged, the parties agree as follows:

          1.  Definitions.
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          "Benefit Period" shall mean the twelve (12)-month period following the
Termination Date, in the context of Section 2, and the twenty-four (24)-month
period following the Termination Date, in the context of Section 3.

          "Cause" shall be deemed to exist if the Board of Directors of the
Company in good faith determines, after giving the Employee notice and an
opportunity to be heard, that the Employee has committed an act constituting
fraud, embezzlement, larceny or theft.

          "Change in Control" shall mean (i) the sale, lease, transfer or other
disposition by the Company of all or substantially all of its assets in a single
transaction or a series of related transactions; (ii) the merger or
consolidation of the Company with another entity in which the stockholders of
the Company immediately prior to such merger or consolidation hold less than 50%
of the outstanding voting stock of the surviving or resulting corporation
immediately following such transaction; or (iii) the sale or exchange (to or
with any person or entity other than the Company) by the stockholders of the
Company of more than 50% of the outstanding voting stock of the Company in a
single transaction or series of related transactions.


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          "Ineligibility Period" shall mean that portion of the applicable
Benefit Period when the Employee is ineligible for coverage under the Company's
group life or group health insurance policies.

          "Termination Date" shall mean the effective date of the termination of
the Employee's employment with the Company.

          2.  Severance Other Than Following a Change in Control.
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          In the event the Employee's employment by the Company is terminated
for any reason other than (i) for Cause by the Company, (ii) voluntary
resignation by the Employee or (iii) the Employee's death, and Section 3 is
inapplicable, the Company shall (i) pay the Employee within five (5) days after
the Termination Date a lump sum amount equal to the sum of (A) twelve (12) times
the Employee's monthly base salary in effect at the time of such termination
plus (B) the average of the annual bonus amounts paid to the Employee in respect
of the Company's two fiscal years immediately preceding the Termination Date
(less applicable withholding taxes and FICA with respect to (A) and (B)) and
(ii) continue to provide during the Benefit Period life and health insurance
coverage to the Employee, with benefits substantially comparable to those
provided to executive officers of the Company generally immediately prior to
such termination. Notwithstanding the foregoing, the Company shall have the
right, in lieu of providing such coverage during any Ineligibility Period, to
pay the Employee an amount equal to 200% of the amount it would have cost the
Company to provide such coverage during such Ineligibility Period, assuming the
Employee were eligible for coverage under the Company's group insurance policies
and assuming further no increase in premium costs under such policies after the
commencement of such Ineligibility Period.

          3.  Severance Following a Change in Control.
              --------------------------------------- 

          Except as provided in the last sentence of this Section 3, in the
event the Employee's employment by the Company is terminated for any reason
whatsoever, including voluntary resignation by the Employee, within twenty-four
months following a Change in Control, the Company shall (i) pay the Employee
within five days after the Termination Date a lump sum amount equal to the sum
of (A) twenty-four (24) times the Employee's monthly base salary in effect at
the time of such termination plus (B) two times the average of the annual bonus
amounts paid 

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to the Employee in respect of the Company's two fiscal years
immediately preceding the Termination Date (less applicable withholding taxes
and FICA with respect to (A) and (B)) and (ii) continue to provide during the
Benefit Period life and health insurance coverage to the Employee, with benefits
substantially comparable to those provided to executive officers of the Company
generally immediately prior to such termination.  Notwithstanding the foregoing,
the Company shall have the right, in lieu of providing such coverage during any
Ineligibility Period, to pay the Employee an amount equal to 200% of the amount
it would have cost the Company to provide such coverage during any Ineligibility
Period, assuming the Employee were eligible for coverage under the Company's
group insurance policies and assuming further no increase in premium costs under
such policies after the commencement of the Ineligibility Period.
Notwithstanding anything to the contrary contained in this Agreement, the
Employee shall not be entitled to any severance benefits pursuant to Section 2
or this Section 3 if the Employee's employment by the Company is terminated by
the Company for Cause.

          4.  Vesting of Stock.  Upon a Change in Control, the vesting of all
              ----------------                                               
stock options held by the Employee and exercisable to purchase common stock of
the Company shall be accelerated so that all such options shall be immediately
exercisable in full.

          5.   Miscellaneous.
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               5.1   This Agreement constitutes the entire agreement between the
parties and supersedes all prior agreements and understandings, whether written
or oral, relating to the subject matter of this Agreement, including without
limitation that certain letter agreement dated October 23, 1990.

               5.2   This Agreement may be amended or modified only by a written
instrument executed by both the Company and the Employee.

               5.3   This Agreement shall be construed, interpreted and enforced
in accordance with the laws of The Commonwealth of Massachusetts.

               5.4   This Agreement shall be binding upon and inure to the
benefit of both parties and their respective successors and assigns, including
any corporation with which or into which the Company may be merged or which may
succeed to its assets or business.

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               5.5   The captions of the sections of this Agreement are for
convenience of reference only and in no way define, limit or affect the scope or
substance of any section of this Agreement.

               5.6   In case any provision of this Agreement shall be invalid,
illegal or otherwise unenforceable, the validity, legality and enforceability of
the remaining provisions shall in no way be affected or impaired thereby.

          IN WITNESS WHEREOF, the parties hereto have executed this Agreement as
of the day and year set forth above.

                                        ASECO CORPORATION            
                                                                     
                                                                     
                                                                     
                                        By:___________________________
                                                                     
                                        Title:________________________
                                                                     
                                                                     
                                                                     
                                        EMPLOYEE                     
                                                                     
                                                                     
                                                                     
                                        ______________________________
                                        Sebastian J. Sicari           
 

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