EXHIBIT 10.5.1  FIRST AMENDMENT TO LEASE  This
FIRST AMENDMENT TO
LEASE (this Amendment) is dated as of this __ day of November,
1999 by and between MONTAGUE LLC, a
California limited liability company (Landlord), and ULTRATECH
STEPPER, INC., a Delaware corporation (Tenant).  RECITALS  A.The Equitable Life Assurance Society of the United States (Equitable)
and Tenant entered into a Lease dated September 10, 1993, as amended by that
certain Agreement Defining Landlords Property dated January 1, 1994, those
certain letter Agreements dated November 24, 1995, and January 5, 1996, and
that certain Commencement of Term Agreement dated January 11, 1996
(collectively, the Lease), for premises (the Premises) with a street
address of 3050 Zanker Road, San Jose, California, and more particularly
described in the Lease.  B.Landlord acquired the property on
which the Premises are located on or about January 29, 1997, and succeeded to
the interest of Equitable as landlord under the Lease.  C.Landlord and Tenant now desire to
amend the Lease on the terms and conditions set forth herein. Capitalized terms
used in this Amendment and not otherwise defined shall have the meanings
assigned to them in the Lease.  AGREEMENT  NOW,
THEREFORE,for good and valuable
consideration, the receipt and sufficiency of which are hereby acknowledged,
Landlord and Tenant hereby agree as follows:  1.             Condition
Precedent To Lease Amendment.This Amendment and the parties obligations hereunder are subject to the
receipt by Landlord, no later than fifteen (15) business days after the date
hereof, of the Lenders Consent, as hereinafter defined. Landlord hereby agrees
to use diligent efforts to obtain the Lenders Consent by such date; however,
if Landlord does not receive the Lenders Consent by such date, this Amendment
shall thereupon be deemed terminated and of no further force or effect, and
neither party shall have any further rights, obligations, or liabilities
hereunder. As used herein, the term Lenders Consent means a written consent
to this Amendment in form reasonably satisfactory to Landlord, executed by the
holder of the promissory note secured by that certain Deed of Trust
(encumbering the fee interest in the real property of which the Premises are a
part) recorded on January 29, 1997, in the Official Records of Santa Clara
County, California, at Series No. 13593424.  2.             Term.Notwithstanding anything to the contrary
contained in the Lease, the initial term of the Lease is hereby extended such
that the Expiration Date (as defined in Section 2 of the Lease) shall be
changed to January 31, 2011 (or such later date to make the term of the Lease
co-terminus with the lease dated of eve date herewith between Landlord and
Tenant for the building known as 2880 Junction Avenue, San Jose, California).
The period of time from the original Expiration Date of April 3, 2005, through
the new Expiration date of January 31, 2011, is referred to herein as the
Extension Period, provided that the Extension Period shall be deemed part of
the Lease Term (as defined in Section 3.L. of the Lease) for all purposes under
the Lease.  3.             Rent
for Extension Period.Basic Rent for the
Extension Period shall be the greater of (a) $1.68 per square foot per month
for the first twelve (12) months of the Extension Period, increased by three
percent (3%) per annum compounded at the end of each twelve (12) month period
during the Extension Period, or (b) the Fair Market Rent (with annual
increases) as determined pursuant to the terms of Section 4 below.  4.             Fair
Market Rent  (a)For purposes hereof, Fair Market
Rent shall mean, collectively, the Basic Rent and annual increases determined
pursuant to the process described below. No earlier than nine (9) months and no
later than six (6) months prior to the commencement of the Extension Period,
Landlord shall notify Tenant in writing of Landlords estimate of Fair Market
Rent for the Extension Period. Within thirty (30) days after receipt of such
notice from Landlord, Tenant shall have the right either to (i) accept
Landlords statement as the Fair Market   1 
   Rent for the Extension Period, or (ii) elect
to arbitrate Landlords estimate of Fair Market Rent, such arbitration to be
conducted pursuant to the provisions hereof. Failure on the part of Tenant to
require arbitration of Fair Market Rent within such thirty (30) day period
shall constitute acceptance of the Fair Market Rent for the Extension Period as
calculated by Landlord. If Tenant elects arbitration, the arbitration shall be
concluded within sixty (60) days after the date of Tenants election, subject
to extension for an additional fifteen (15) day period if a third arbitrator is
required and does not act in a timely manner. To the extent that arbitration
has not been completed prior to the expiration of any preceding period for
which Basic Rent has been determined, Tenant shall pay Basic Rent at the rate
calculated by Landlord, with the potential for an adjustment to be made once
Fair Market Rent is ultimately determined by arbitration.  (b)           In
the event of arbitration, the judgment or the award rendered in any such
arbitration may be entered in any court having jurisdiction and shall be final
and binding between the parties. The arbitration shall be conducted and
determined in the City of San Jose in accordance with the then prevailing rules
of the American Arbitration Association or its successor for arbitration of
commercial disputes except to the extent that the procedures mandated by such
rules shall be modified as follows:  (i)            Tenant
shall make demand for arbitration in writing within thirty (30) days after
service of Landlords determination of Fair Market Rent given under Section
4(a) above, specifying therein the name and address of the person to act as the
arbitrator on its behalf. The arbitrator shall be qualified as a real estate
appraiser familiar with the Fair Market Rent of similar industrial, research
and development, or office space in the Silicon Valley area who would qualify
as an expert witness over objection to give opinion testimony addressed to the
issue in a court of competent jurisdiction. Failure on the part of Tenant to
make a proper demand in a timely manner for such arbitration shall constitute a
waiver of the right thereto. Within fifteen (15) days after the service of the
demand for arbitration, Landlord shall give notice to Tenant, specifying the
name and address of the person designated by Landlord to act as arbitrator on
its behalf who shall be similarly qualified. If Landlord fails to notify Tenant
of the appointment of its arbitrator, within or by the time above specified,
then the arbitrator appointed by Tenant shall be the arbitrator to determine
the issue.  (ii)           In
the event that two arbitrators are chosen pursuant to section 4(b)(i) above,
the arbitrators so chosen shall, within fifteen (15) days after the second
arbitrator is appointed determine the Fair Market Rent. If the two arbitrators
shall be unable to agree upon a determination of Fair Market Rent within such
fifteen (15) day period, they, themselves, shall appoint a third arbitrator,
who shall be a competent and impartial person with qualifications similar to
those required of the first two arbitrators pursuant to Section 4(b)(i). In the
event they are unable to agree upon such appointment within seven (7) days
after expiration of such fifteen (15) day period, the third arbitrator shall be
selected by the parties themselves, if they can agree thereon, within a further
period of fifteen (15) days. If the parties do not so agree, then either party,
on behalf of both, may request appointment of such a qualified person by the
then Chief Judge of the United States District Court having jurisdiction over
the County of Santa Clara, acting in his private and not in his official
capacity, and the other party shall not raise any question as to such Judges
full power and jurisdiction to entertain the application for and make the
appointment. The three arbitrators shall decide the dispute if it has not
previously been resolved by following the procedure set forth below.  (iii)         Where
an issue cannot be resolved by agreement between the two arbitrators selected
by Landlord and Tenant or settlement between the parties during the course of
arbitration, the issue shall be resolved by the three arbitrators within
fifteen (15) days of the appointment of the third arbitrator in accordance with
the following procedure. The arbitrator selected by each of the parties shall
state in writing his determination of the Fair Market Rent supported by the
reasons therefor with counterpart copies to each party. The arbitrators shall
arrange for a simultaneous exchange of such proposed resolutions. The role of
the third arbitrator shall be to select which of the two proposed resolutions
most closely approximates his determination of Fair Market Rent. The third
arbitrator shall have no right to propose a middle ground or any modification
of either of the two proposed resolutions. The resolution he chooses as most
closely approximating his determination shall constitute the decision of the
arbitrators and be final and binding upon the parties.  (iv)          In
the event of a failure, refusal or inability of any arbitrator to act, his
successor shall be appointed by him, but in the case of the third arbitrator,
his successor shall   2 
   be appointed in the same manner as provided
for appointment of the third arbitrator. The arbitrators shall decide the issue
within fifteen (15) days after the appointment of the third arbitrator. Any
decision in which the arbitrator appointed by Landlord and the arbitrator
appointed by Tenant concur shall be binding and conclusive upon the parties.
Each party shall pay the fee and expenses of its respective arbitrator and both
shall share the fee and expenses of the third arbitrator, if any, and the attorneys
fees and expenses of counsel for the respective parties and of witnesses shall
be paid by the respective party engaging such counsel or calling such
witnesses.  (v)            The
arbitrators shall have the right to consult experts and competent authorities to
obtain factual information or evidence pertaining to a determination of Fair
Market Rent, but any such consultation shall be made in the presence of both
parties with full right on their part to cross-examine. The arbitrators shall
render their decision and award in writing with counterpart copies to each
party. The arbitrators shall have no power to modify the provisions of the
Lease or this Amendment.  5.             Ratification.
The Lease, as amended by this Amendment, is hereby ratified by Landlord and
Tenant and Landlord and Tenant hereby agree that the Lease, as so amended,
shall continue in full force and effect.  6.             Miscellaneous.  (a)           Voluntary
Agreement. The parties have read this Amendment and on the advice of
counsel they have freely and voluntarily entered into this Amendment.  (b)           Attorneys
Fees. If either party commences an action against the other party
arising out of or in connection with this Amendment, the prevailing party shall
be entitled to recover from the losing party reasonable attorneys fees and
costs of suit.  (c)           Successors.This Amendment shall be binding on and inure to the benefit of the
parties and their successors.  (d)           Counterparts.
This Amendment may be signed in two or more counterparts. When at least one
such counterpart has been signed by each party, this Amendment shall be deemed
to have been fully executed, each counterpart shall be deemed to be an
original, and all counterparts shall be deemed to be one and the same
agreement.  IN WITNESS WHEREOF, Landlord and Tenant have
executed this Amendment as of the date first written above.  LANDLORD:MONTAGUE LLC,a California
  limited liability companyBy:
  Montague Park Corporation,
  a California corporationBy:
  /s/
  Henry D. BullockHenry D. Bullock, President   3 
   TENANT:ULTRATECH STEPPER, INC.,a Delaware
  corporationBy:
  /s/
  Bruce R. WrightName:
  Bruce R. WrightTitle:
  Chief Financial OfficerBy:Name:Title:     4