FOURTH
                          AMENDMENT TO CREDIT AGREEMENT

         THIS FOURTH AMENDMENT TO CREDIT AGREEMENT (the "Fourth Amendment"), is
executed as of the 29th day of December, 1999, by and between PLASMA-THERM,
INC., a Florida corporation whose address is 10050 16th Street North, St.
Petersburg, Florida 33716 (hereinafter called "Borrower") and BANK OF AMERICA,
N.A., a national banking association, d/b/a NationsBank, N.A., successor to
NationsBank, N.A., f/k/a NationsBank, N.A. (South), whose address is 101 E.
Kennedy Boulevard, 5th Floor (FL1-400-05-03), Tampa, Florida 33602 (hereinafter
called "Lender").

                              W I T N E S S E T H:

         WHEREAS, on April 18, 1997, Borrower and Lender executed that certain
Credit Agreement (the "Credit Agreement") to set forth the terms and provisions
relating to certain loans made by Lender to Borrower.

         WHEREAS, the Credit Agreement was amended on March 25, 1998 (the "First
Amendment"), December 8, 1998 (by letter agreement) (the "Letter Amendment"),
February 18, 1999 (the "Second Amendment"), and May 31, 1999 (the "Third
Amendment").

         WHEREAS, simultaneously with entering into this Fourth Amendment,
Borrower has modified that certain construction/term loan made by Lender to
Borrower on February 18, 1999, in the original principal amount of
$4,500,000.00.

         WHEREAS, in connection with the aforesaid modification, Lender and
Borrower desire to amend the Credit Agreement, as previously amended by the
First Amendment, Letter Amendment, Second Amendment and Third Amendment.

         NOW THEREFORE, for and in consideration of the premises and for other
good and valuable consideration, the receipt and adequacy of which are hereby
acknowledged by all of the parties hereto, the parties hereby covenant and agree
as follows:

         1. AMENDMENTS TO CREDIT AGREEMENT. The terms of the Credit Agreement,
First Amendment, Letter Amendment, Second Amendment and Third Amendment are
hereby modified, supplemented and amended as follows:

                  a. The Borrowing Base Certificate attached as Exhibit "A" to
the Credit Agreement is hereby deleted in its entirety and replaced by that
certain Borrowing Base Certificate Form attached hereto as Exhibit "A" to this
Fourth Amendment.

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                  b. Sections 6x. and 6y. of the Credit Agreement as set forth
in Section 1m. of the Third Amendment are hereby deleted in their entirety.

                  c. The Credit Agreement is hereby amended to add the following
subsections cc., dd. and ee. to Section 6:

                     cc. The Borrower shall maintain minimum quarterly revenue
                  of not less than $10,000,000.00.

                     dd. The Borrower shall maintain minimum quarterly EBITDA of
                  not less than $1,400,000.00.

                     ee. The Borrower shall submit to the Lender company
                  prepared financial statements for the three-month period ended
                  November 30, 1999, not later than December 31, 1999.

                  d. Section 7i. of the Credit Agreement as amended by Section
1n. of the Third Amendment is hereby deleted in its entirety and replaced by the
following:

                     i. The Borrower shall maintain a Cash Flow Coverage
                  Ratio of 2.00 to 1.00. Cash Flow Coverage Ratio is defined as
                  EBITDA less fifty percent (50%) of capital expenditures, less
                  shareholder distributions, less share repurchases, less tax
                  expense, all divided by current maturities of long term debt
                  and capital lease obligations and interest expense. EBITDA
                  shall be defined as net earnings plus interest expense, less
                  interest income, plus income tax expense, plus depreciation
                  expense, plus amortization expense. For purposes of
                  calculating the EBITDA, capital expenditures, interest expense
                  and income tax expense, the Borrower's third quarter 1999
                  shall be multiplied by four (4), the Borrower's third and
                  fourth quarter 1999 performance shall be multiplied by two
                  (2), and the Borrower's third and fourth quarter 1999 and
                  first quarter 2000 will be multiplied by 1.33. Beginning at
                  the fiscal quarter ended May 31, 2000, EBITDA, interest
                  expense, capital expenditures and income tax expense shall be
                  calculated based on the last four consecutive fiscal quarters.

                           In addition, for purposes of calculating the Cash
                  Flow Coverage Ratio, the current maturities of long term debt
                  and capital leases in the denominator shall be the greater of
                  actual current maturities from the financial statements or
                  $550,000.00. Also, interest

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<PAGE>

                  expense in the denominator shall be the greater of the
                  interest expense as determined in the prior paragraph or
                  $500,000.00.

                           For purposes of calculating EBITDA, net income shall
                  exclude any net gains on the sale, conversion or other
                  disposition of capital assets, net gains on the acquisition,
                  retirement, sale or other disposition of capital stock and
                  other securities of the Borrower and any subsidiaries, net
                  gains on the collection of proceeds of life insurance
                  policies, any right-up of any asset, any other net gain or
                  credit of an extraordinary nature, all determined in
                  accordance with GAAP.

                  e. The Credit Agreement is hereby amended to add the following
subsection k. to Section 7:

                  k. Make any shareholder dividend payments or incur any cash
                  outflow for the repurchase of its capital stock without prior
                  written approval from the Lender.

The Credit Agreement, as modified by the First Amendment, the Letter Amendment,
the Second Amendment, the Third Amendment and this Fourth Amendment shall remain
in full force and effect, shall conform fully with this Fourth Amendment, and
shall apply with full force and effect to the Loans described in the Credit
Agreement.

         2. REPRESENTATIONS AND WARRANTIES OF BORROWER. Borrower hereby
restates, reaffirms, and where necessary updates, all representations and
warranties set forth in Section 8 of the Credit Agreement and elsewhere in the
Credit Agreement, as amended from time to time.

         3. OTHER TERMS AND CONDITIONS. Except as set forth herein, all other
terms and conditions of the Credit Agreement and the First Amendment, the Letter
Amendment, the Second Amendment and the Third Amendment shall remain in full
force and effect and shall be binding upon the Lender and the Borrower pursuant
to their terms, and the Borrower and Lender hereby ratify and reaffirm all
covenants, obligations, terms, conditions and provisions under the Credit
Agreement.


             The remainder of this page is intentionally left blank.


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<PAGE>

         IN WITNESS WHEREOF, Borrower and Lender have executed this Third
Amendment the day and year first above written.


Signed, sealed and delivered in    PLASMA-THERM, INC., a Florida
the presence of:                   corporation ("Borrower")

 /s/ MICHELLE A. DOWLING
 -----------------------
 Signature of Witness


 /s/ MICHELLE A. DOWLING           By: /s/ STACY L. WAGNER
 -----------------------              -------------------
 Legibly Print Name of Witness        Stacy L. Wagner
                                      Vice President and Chief Financial Officer

 /s/ NEDRA MILLNER
 -----------------
Signature of Witness                    (CORPORATE SEAL)


 /s/ NEDRA MILLNER
 -----------------
Legibly Print Name of Witness


                                   BANK OF AMERICA, N.A., a national banking
 /s/ LINDA R. EARLS                association, d/b/a NationsBank, N.A.,
 ------------------                successor to NationsBank, N.A., f/k/a
 Signature of Witness              NationsBank, N.A. (South) ("Lender")

 /s/ LINDA R. EARLS
 ------------------
 Legibly Print Name of Witness     By: /s/ SADAHRI W. BERRY
                                       --------------------
 /s/ JEAN L.L. MILLER                  Sadahri W. Berry
 --------------------                  Vice President
Signature of Witness

 /s/ JEAN L.L. MILLER                   (CORPORATE SEAL)
 --------------------
Legibly Print Name of Witness


STATE OF GEORGIA  )
COUNTY OF CLAYTON )

         The foregoing instrument was acknowledged before me this 29th day of
December, 1999, by STACY L. WAGNER, as Vice President and Chief Financial
Officer of PLASMA-THERM, INC., a Florida corporation, on behalf of the
corporation. She is |_| personally known to me or |X| has produced FLORIDA
DRIVER'S LICENSE as identification.

       Notary Public, Fulton County Georgia
       My Commission Expires August 22, 2003

My commission expires:                       /s/ MICHELLE A. DOWLING
                      ---------------------  --------------------------
                                             Signature of Notary Public

                        (SEAL)               MICHELLE A. DOWLING
                                             -------------------
                                             Legibly Print Name of Notary Public

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<PAGE>

                                   EXHIBIT "A"

                         BORROWING BASE CERTIFICATE FORM
                                   Page 1 of 2



BANK OF AMERICA, N.A.                                  DATE:  __________________
P.O. Box 31590
FL1-010-02-01
Tampa, Florida  33631

Credit Agreement between us, the undersigned hereby certifies to you, as of the
above date, the following:
<TABLE>
<CAPTION>


<S>                                                                                    <C>
(A)  Aggregate amount of domestic Accounts as of the applicable month end              $
                                                                                       ------------------------

(B)  Less Ineligible Accounts (Accounts which do not meet the definition of
     Eligible Accounts): $

(C)  Net Amount of Eligible domestic Accounts (A)-(B)                                  $
                                                                                       ------------------------

(D)  80% of Item (C)                                                                   $
                                                                                       ------------------------

(E)  Foreign accounts less than 60 days old backed by letters of credit                $
                                                                                       ------------------------

(F)  80% of Item (E)                                                                   $

(G)  The lesser of:  25% of raw materials inventory (excluding all raw material
     inventory on hand in excess of one year old) OR $3,000,000.00
                                                                                       $
                                                                                       ------------------------

(H)  Total items (D), (F) and (G)                                                      $
                                                                                       ------------------------

(I)  The lesser of $10,000,000 and Item (H)                                            $
                                                                                       ------------------------

(J)  The aggregate unpaid principal Line Loan we now owe Lender as of the applicable
     month end                                                                         $
                                                                                       ------------------------

(K)  The aggregate amount of issued, outstanding Standby Letters of Credit as of the
     applicable month end                                                              $
                                                                                       ------------------------

(L)  Total of unpaid principal Line Loan and issued Standby Letters of Credit is as
     of the applicable month end                                                       $
                                                                                       ------------------------

(M)  Availability [(I)-(J)] [If Item (M) is negative, paydown of at least a
     like amount is required or establishment of minimum liquidity of equal
     amount, to Lender's satisfaction]                                                 $
                                                                                       ------------------------
</TABLE>


<PAGE>

                                   EXHIBIT "A"

                         BORROWING BASE CERTIFICATE FORM
                                   Page 2 of 2


The undersigned hereby certifies, represents and warrants to Bank of America,
N.A., a national banking association as follows:

1.       All of the representations and warranties contained in the Credit
         Agreement or in any other Loan Document are true and correct in all
         material respects on the date hereof, except to the extent such
         representations and warranties expressly relate to an earlier date.

2.       No event has occurred, or would result from the Advance made in
         connection herewith, that constitutes an Event of Default or a Default
         that, with the giving of notice, the passage of time, or both would
         constitute an Event of Default under the Credit Agreement or any other
         Loan Document.

3.       The description of Eligible Accounts and the values assigned thereto
         are true and correct in all material respects.

4.       The aggregate unpaid principal balance of the Line Loan does not exceed
         the lesser of (i) the Line Commitment or (ii) the Borrowing Base,
         unless adequate minimum liquidity has been established to Lender's
         satisfaction.

Unless the context otherwise requires, all capital terms used in this
Certificate if not separately defined herein, shall have the meanings assigned
to them in the Credit Agreement.



PLASMA-THERM, INC., a Florida corporation


By:   __________________________________________
      Stacy L. Wagner
      Vice President and Chief Financial Officer


Date: __________________________________________


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