<PAGE>

                                                                    EXHIBIT 3.15

                          CERTIFICATE OF INCORPORATION
                                       OF
                            AMTECH WORLD CORPORATION

                                    ARTICLE I

      The name of the Corporation is Amtech World Corporation.

                                   ARTICLE II

      The name of the Corporation's registered agent and the address of its
registered office in the State of Delaware is The Corporation Trust Company,
1209 Orange Street, Wilmington, New Castle County, Delaware 19801.

                                   ARTICLE III

      The purpose of the Corporation is to engage in any lawful act or activity
for which corporations may be organized under the Delaware General Corporation
Law, as the same exists or may hereafter be amended.

                                   ARTICLE IV

      The total number of shares of capital stock which the Corporation shall
have the authority to issue is One Hundred Thousand (100,000) shares of Common
Stock, $.01 par value,

                                    ARTICLE V

      The business and affairs of the Corporation shall be managed by the Board
of Directors. The number of directors constituting the initial Board of
Directors is three (3), and the names of the persons who are to serve as
directors until the first annual meeting of stockholders or until their
successors are duly elected and qualified are as follows:

<TABLE>
<CAPTION>
    Director                     Address
-------------------    ---------------------------
<S>                    <C>
David P. Cook          4514 Cole Ave., Suite 1200
                       Dallas, Texas  75205

Kenneth W. Anderson    4514 Cole Ave., Suite 1200
                       Dallas, Texas  75205

Gary L. Seawright      2530 Camino Entrada
                       Santa Fe, New Mexico  87505
</TABLE>

<PAGE>

                                   ARTICLE VI

      In furtherance and not limitation of the powers conferred by the Delaware
General Corporation Law, the Board of Directors is expressly authorized to
alter, amend or repeal the bylaws of the Corporation or to adopt new bylaws.

                                   ARTICLE VII

      The incorporator is William E. Stone, III whose mailing address is 2000
Lincoln Plaza, 500 North Akard, Dallas, Texas 75201.

                                  ARTICLE VIII

      A director of the Corporation shall not be personally liable to the
Corporation or its stockholders for monetary damages for breach of fiduciary
duty as a director, except liability (i) for any breach of the director's duty
of loyalty to the Corporation or its stockholders, (ii) for acts or omissions
not in good faith or which involve intentional misconduct or a knowing violation
of law, (iii) under Section 174 of the Delaware General Corporation Law, or (iv)
for any transaction from which the director derived any improper personal
benefit. If the Delaware General Corporation Law is amended after the filing of
this Certificate of Incorporation to authorize corporate action further
eliminating or limiting the personal liability of directors, then the liability
of a director of the Corporation shall be eliminated or limited to the fullest
extent permitted by the Delaware General Corporation Law, as so amended.

      Any repeal or modification of the foregoing paragraph by the stockholders
of the Corporation shall not adversely affect any right or protection of a
director of the Corporation existing at the time of such repeal of modification.

                                   ARTICLE IX

      A. Each person who was or is made a party or is threatened to be made a
party to or is otherwise involved in any action, suit or proceeding, whether
civil, criminal, administrative or investigative (hereinafter a "proceeding"),
by reason of the fact that he or she, or a person of whom he or she is the legal
representative, is or was a director or officer of the Corporation or is or was
serving at the request of the Corporation as a director or officer of another
corporation or of a partnership, joint venture, trust or other enterprise,
including service with respect to an employee benefit plan (hereinafter an
"indemnitee"), whether the basis of such proceeding is alleged action in an
official capacity as a director or officer or in any other capacity while
serving as a director or officer shall be indemnified and held harmless by the
Corporation to the fullest extent authorized by the Delaware General Corporation
Law, as the same exists or may hereafter be amended (but, in the case of any
such amendment, only to the extent that such amendment permits the Corporation
to provide broader indemnification rights than permitted prior thereto), against
all expense, liability and loss (including, without limitation, attorneys' fees,
judgments, fines, ERISA excise taxes or penalties and amounts paid or to be paid
in settlement) reasonably incurred or suffered by such indemnitee in connection
therewith and such indemnification shall continue as to an indemnitee who has
ceased to be a director or officer and shall inure to the benefit of the
indemnitee's heirs, executors and administrators; provided, however, that,
except for a proceeding brought by an indemnitee to enforce his rights to

                                       2
<PAGE>

indemnification, the Corporation shall indemnify any such indemnitee in
connection with a proceeding (or part thereof) initiated by such indemnitee only
if such proceeding (or part thereof) was authorized by the board of directors of
the Corporation. The right to indemnification conferred in this Article IX shall
be a contract right and shall include the right to be paid by the Corporation
the expenses incurred in defending any such proceeding in advance of its final
disposition (hereinafter an "advancement of expenses"); provided, however, that,
if the Delaware General Corporation Law requires, an advancement of expenses
incurred by an indemnitee in his or her capacity as a director or officer (and
not in any other capacity in which service was or is rendered by such
indemnitee, including, without limitation, service to an employee benefit plan)
shall be made only upon delivery to the Corporation of an undertaking
(hereinafter an "undertaking"), by or on behalf of such indemnitee, to repay all
amounts so advanced if it shall ultimately be determined by final judicial
decision from which there is no further right to appeal (hereinafter a "final
adjudication") that such indemnitee is not entitled to be indemnified for such
expenses under this Article or otherwise.

      B. If a claim under this Article is not paid in full by the Corporation
within a reasonable time after a written claim has been received by the
Corporation, the indemnitee may at any time thereafter bring suit against the
Corporation to recover the unpaid amount of the claim. If successful in whole or
in part in any such suit, or advancement of expenses pursuant to the terms of an
undertaking, the indemnitee shall be entitled to be paid also the expense of
prosecuting or defending such suit. In (i) any suit brought by the indemnitee to
enforce a right to indemnification hereunder (but not in a suit brought by the
indemnitee to enforce a right to an advancement of expenses) it shall be a
defense that, and (ii) any suit by the Corporation to recover an advancement of
expenses pursuant to the terms of an undertaking the Corporation shall be
entitled to recover such expenses upon a final adjudication that, the indemnitee
has not met the applicable standard of conduct set forth in the Delaware General
Corporation Law. Neither the failure of the Corporation (including its board of
directors, independent legal counsel or its stockholders) to have made a
determination prior to the commencement of such suit that indemnification met
the applicable standard of conduct set forth in the Delaware General Corporation
Law, nor an actual determination by the Corporation (including its board of
directors, independent legal counsel, or its stockholders) that the indemnitee
has not met such applicable standard of conduct, shall create a presumption that
the indemnitee has not met the applicable standard of conduct or, in the case of
such a suit brought by the indemnitee, be a defense to such suit. In any suit
brought by the indemnitee to enforce a right to indemnification or to an
advancement of expenses hereunder or by the Corporation to recover an
advancement of expenses pursuant to the terms of an undertaking, the burden of
proving that the indemnitee is not entitled to be indemnified, or to such
advancement of expenses, under this Article or otherwise shall be on the
Corporation.

      C. The rights to indemnification and to the advancement of expenses
conferred in this Article IX shall not be exclusive of any other right which any
person may have or hereafter acquire under this Certificate of Incorporation or
any bylaw, agreement, vote of stockholders or disinterested directors or
otherwise.

      D. The Corporation may maintain insurance, at its expense, to protect
itself and any director or officer of the Corporation or another corporation,
partnership, joint venture, trust or other enterprise against any expense,
liability or loss, whether or not the Corporation would have

                                       3
<PAGE>

the power to indemnify such person against such expense, liability or loss under
the Delaware General Corporation Law.

      E. The Corporation may, to the extent authorized from time to time by the
board of directors, grant rights to indemnification and to the advancement of
expenses to any employee or agent of the Corporation the fullest extent of the
provisions of this Article IX with respect to the indemnification and
advancement of expenses of directors and officers of the Corporation.

                                    ARTICLE X

      No stockholder of the Corporation will be entitled to cumulative voting
with respect to the election of directors or, by reason of his holding shares of
any class of capital stock of the Corporation, have any preferential rights to
purchase or subscribe to any shares of any class of capital stock of the
Corporation, or any notes, debentures, bonds, warrants, options or other
securities of the Corporation, now or hereafter to be authorized.

                                   ARTICLE XI

      Any amendment to this Certificate of Incorporation, any merger or
consolidation of this Corporation with or into another corporation or
joint-stock or other association, any sale, lease or exchange of all or
substantially all the assets of this Corporation, any dissolution of this
Corporation or any alteration of the powers, preference or special rights of the
shares of any class of the capital stock of this Corporation shall require the
affirmative vote of the holders of at least two-thirds of the outstanding shares
entitled to vote thereon.

      IN WITNESS WHEREOF, the undersigned incorporator of the Corporation hereby
certifies that the facts herein stated are true, and accordingly has signed this
instrument this 21st day of October, 1987.

                                  /s/ William E. Stone, III
                                  -------------------------
                                  William E. Stone, III

                                       4
<PAGE>

                 CERTIFICATE OF CHANGE OF LOCATION OF REGISTERED

                           OFFICE AND REGISTERED AGENT

                                       OF

                            AMTECH WORLD CORPORATION

      The Board of Directors of: AMTECH WORLD CORPORATION a Corporation of the
State of Delaware, on this 1st day of March, A.D. 1996, do hereby resolve and
order that the location of the Registered Office of this Corporation within this
State be, and the same hereby is:
1013 Centre Road, in the City of Wilmington, in the County of New Castle,
Delaware, 19805.

      The name of the Registered Agent therein and in charge thereof upon whom
process against the Corporation may be served, is: CORPORATION SERVICE COMPANY.

      AMTECH WORLD CORPORATION a Corporation of the State of Delaware, does
hereby certify that the foregoing is a true copy of a resolution adopted by the
Board of Directors at a meeting held as herein stated.

      IN WITNESS WHEREOF, said corporation has caused this Certificate to be
signed by Ronald A. Woessner , Vice President this 18th day of March A.D. 1996.

                                  Amtech World Corporation

                                  /s/ Ronald W. Woessner
                                  ----------------------
                                  Authorized Officer
                                  Ronald W. Woessner