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                                                                     Exhibit 10a

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                             KEY EMPLOYEE AGREEMENT

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To:  Jill Maunder                                       As of  February 2, 1998



     The undersigned, Applied Science and Technology, Inc., a Delaware
corporation, as well as its successors and assigns (hereinafter collectively
referred to as the "Company"), hereby agree with you as follows:

     l. POSITION AND RESPONSIBILITIES.

        1.1 You shall serve as Vice President of Human Resources of the Company
(or in such other capacity as shall be designated by the President or Board of
Directors and reasonably acceptable to you). You will, to the best of your
ability, devote your full time and best efforts to the performance of your
duties hereunder and the business and affairs of the Company and perform such
duties as may be assigned to you by or on authority of the Company's President
from time to time and the duties customarily associated with such capacity from
time to time and at such place or places as the Company shall designate are
appropriate and necessary in connection with such employment.

        1.2  You will duly, punctually and faithfully perform and observe any
and all rules and regulations which the Company may now or shall hereafter
establish governing the conduct of its business.

        1.3  You will report directly to the Company's President and will be
based out of the Company's Massachusetts corporate office.

     2. TERM OF EMPLOYMENT.

        2.1 The initial term of this Agreement shall be for the period set forth
on EXHIBIT A annexed hereto commencing with the date hereof. Thereafter, this
Agreement shall be automatically renewed for successive periods of one year,
unless you or the Company shall give the other party not less than thirty (30)
days written notice of non-renewal. Your employment with the Company may be
terminated as provided in Section 2.2 .

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       2.2  The Company shall have the right, upon written notice to you, to
terminate your employment:

                         (a) immediately at any time for "Cause" (as defined 
         herein subject to your right of cure and right to dispute as provided
         in Section 2.3 herein); or

                         (b) at any time, without "Cause," provided that the
         Company shall be obligated to pay to you the Severance Benefits set
         forth in Sections 6 or 7, as applicable, of EXHIBIT A, plus any sums
         then due to you, including those expenses as are provided for in
         Section 4 of EXHIBIT A, less (i) applicable taxes and other required
         withholdings, and (ii) any amounts you may owe to the Company. Payments
         under this Section 2.2 (b) shall not be due or payable if you are
         terminated at any time for "Cause" or if you voluntarily resign from
         your employment, except as set forth in Section 7 of EXHIBIT A.

       2.3 For purposes of Section 2.2, the term "Cause" shall mean (a) gross
negligence or willful misconduct in the performance of assigned duties; (b)
material and repetitive refusal to perform or discharge the duties or
responsibilities assigned by the President of the Company provided the same are
not illegal, unethical or inconsistent with the position of Vice President of
Human Resources of a corporation and the failure to correct such refusal and
perform such duties or responsibilities within a reasonable period of time (but
in any event no less than seven (7) calendar days after written notice of such
failure); (c) conviction of a felony or misdemeanor involving moral turpitude;
(d) willful or prolonged absence from work not excused by a bona fide medical
disability as reasonably determined by a qualified physician mutually acceptable
to both you and the Company or other good cause as reasonably determined by the
Board of Directors; and (e) falseness of any warranty or representation by you
herein or the breach of your obligations under this Agreement to the material
detriment of the Company.

       2.4 In the event of the Involuntary Termination (as hereinafter defined) 
of your employment with the Company at any time, the Company hereby agrees to
provide you with Severance Benefits as defined in Section 6 of EXHIBIT A hereto
or payments in the event of a "Change in Control" as defined in Section 7 of
EXHIBIT A. In this regard, the phrase "Involuntary Termination" shall mean (a)
any termination of your employment by the Company other than for "cause," as
defined in Section 2.3, (b) any notice by the Company not to renew this
Agreement pursuant to Section 2.1, or (c) for purposes of Section 7 of EXHIBIT A
(but not Section 6 of EXHIBIT A) any termination of your employment by you due
to any of the following circumstances: (i) a reduction in your Base Salary or
Company-paid benefits, (ii) a reduction in your eligibility for any Company
bonus or other benefit program, or (iii) a material or substantial change in
your title, position, authority or duties.

       2.5 You shall have the right to terminate this Agreement upon not less 
than thirty (30) days prior written notice to the Company.

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     3. COMPENSATION. You shall receive the compensation and benefits set forth
on EXHIBIT A ("Compensation") for all services to be rendered by you hereunder
and for your transfer of property rights pursuant to an agreement relating to
proprietary information and inventions of even date herewith attached hereto as
Exhibit C between you and the Company (the "Proprietary Information and
Inventions Agreement").

     4. OTHER ACTIVITIES DURING EMPLOYMENT.

        4.1 Except for any outside employments and directorships currently held
by you as listed on EXHIBIT B, and except with the prior written consent of the
Company's President, you will not during the term of this Agreement undertake or
engage in any other employment, occupation or business enterprise other than one
in which you are an inactive investor.

        4.2 You hereby agree that, except as disclosed on EXHIBIT B hereto,
during your employment hereunder, you will not, directly or indirectly, engage
(a) individually, (b) as an officer, (c) as a director, (d) as an employee, (e)
as a consultant, (f) as an advisor, (g) as an agent (whether a salesperson or
otherwise), (h) as a broker, or (i) as a partner, coventurer, stockholder or
other proprietor owning directly or indirectly more than two percent (2%)
interest, in any firm, corporation, partnership, trust, association, or other
organization which is engaged in the research, development, production,
manufacture or marketing of equipment or processes in direct competition with
the Company or any other line of business engaged in or under demonstrable
development by the Company (such firm, corporation, partnership, trust,
association, or other organization being hereinafter referred to as a
"Prohibited Enterprise"). Except as may be shown on EXHIBIT B, you hereby
represent that you are not engaged in any of the foregoing capacities (a)
through (i) in any Prohibited Enterprise.

     5. FORMER EMPLOYERS.

        5.1 You represent and warrant that your employment by the Company will
not conflict with and will not be constrained by any prior or current
employment, consulting agreement or relationship whether oral or written. You
represent and warrant that you do not possess confidential information arising
out of any such employment, consulting agreement or relationship which, in your
best judgment, would be utilized in connection with your employment by the
Company in the absence of Section 5.2.

        5.2 If, in spite of the second sentence of Section 5.1, you should find
that confidential information belonging to any other person or entity might be
usable in connection with the Company's business, you will not disclose to the
Company or use on behalf of the Company any confidential information belonging
to any of your former employers; but during your employment by the Company you
will use in the performance of your duties all information

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<PAGE>   4

which is generally known and used by persons with training and experience
comparable to your own which is common knowledge in the industry or otherwise
legally in the public domain.

     6. PROPRIETARY INFORMATION AND INVENTIONS. You agree to execute, deliver
and be bound by the provisions of the Proprietary Information and Inventions
Agreement.

     7. POST-EMPLOYMENT ACTIVITIES.

        7.1 For a period of two (2) years (or for a lesser period should the
Company so determine) after the termination or expiration, for any reason, of
your employment with the Company hereunder, absent the Company's prior written
approval, you will not directly or indirectly engage in activities similar or
reasonably related to those in which you shall have engaged hereunder during the
two years immediately preceding termination or expiration for, nor render
services similar or reasonably related to those which you shall have rendered
hereunder during such two years to, any person or entity whether now existing or
hereafter established which directly competes with (or proposes or plans to
directly compete with) the Company ("Direct Competitor") in any line of business
engaged in or under development by the Company. Nor shall you entice, induce or
encourage any of the Company's other employees to engage in any activity which,
were it done by you, would violate any provision of the Proprietary Information
and Inventions Agreement or this Section 7 or to work with you in any other
organization. As used in this Section 7.1, the term "any line of business
engaged in or under development by the Company" shall be applied as at the date
of termination of your employment, or, if later, as at the date of termination
of any post-employment consultation.

        7.2 For a period of two (2) years after the termination of your
employment with the Company, the provisions of Section 4.2 shall be applicable
to you and you shall comply therewith. As applied to such two (2) year
post-employment period, the term "any other line of business engaged in or under
development by the Company," as used in Section 4.2, shall be applied as at the
date of termination of your employment with the Company or, if later, as at the
date of termination of any post-employment consultation with the Company.

        7.3 No provision of this Agreement shall be construed to preclude you
from performing the same services which the Company hereby retains you to
perform for any person or entity which is not a Direct Competitor of the Company
upon the expiration or termination of your employment (or any post-employment
consultation) so long as you do not thereby violate any term of the Proprietary
Information and Inventions Agreement.

     8. REMEDIES. Your obligations under the Proprietary Information and
Inventions Agreement and the provisions of Sections 4, 6, 7, 8, and 9 of this
Agreement (as modified by Section 10, if applicable) shall survive the
expiration or termination of your employment (whether through your resignation
or otherwise) with the Company. You acknowledge that a remedy at law for any
breach or threatened breach by you of the provisions of the Proprietary

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<PAGE>   5

Information and Inventions Agreement or Section 7 hereof would be inadequate and
you therefore agree that the Company shall be entitled to such injunctive or
other equitable relief in case of any such breach or threatened breach.

     9. ASSIGNMENT. This Agreement and the rights and obligations of the parties
hereto shall bind and inure to the benefit of any successor or successors of the
Company by reorganization, merger or consolidation and any assignee of all or
substantially all of its business and properties, but, except as to any such
successor or assignee of the Company, neither this Agreement nor any rights or
benefits hereunder may be assigned by the Company or by you, except by operation
of law. The Company's obligations and those of any successors or assignees of
the Company under this Agreement, including but not limited to the severance
provisions and other compensation and benefits due to you pursuant to EXHIBIT A
hereto, will be a condition of and are to remain those of any successor or
assignee.

     10. INTERPRETATION. IT IS THE INTENT OF THE PARTIES THAT in case any one or
more of the provisions contained in this Agreement shall, for any reason, be
held to be invalid, illegal or unenforceable in any respect, such invalidity,
illegality or unenforceability shall not affect the other provisions of this
Agreement, and this Agreement shall be construed as if such invalid, illegal or
unenforceable provision had never been contained herein. MOREOVER, IT IS THE
INTENT OF THE PARTIES THAT in case any one or more of the provisions contained
in this Agreement shall for any reason be held to be excessively broad as to
duration, geographical scope, activity or subject, such provision shall be
construed by limiting and reducing it as determined by a court of competent
jurisdiction, so as to be enforceable to the extent compatible with applicable
law.

     11. NOTICES. Any notice which the Company is required to or may desire to
give you shall be given by personal delivery or registered or certified mail,
return receipt requested, addressed to you at your address of record with the
Company, or at such other place as you may from time to time designate in
writing. Any notice which you are required or may desire to give to the Company
hereunder shall be given by personal delivery or by registered or certified
mail, return receipt requested, addressed to the Company at its principal
office, or at such other office as the Company may from time to time designate
in writing. The date of personal delivery or the date of mailing any notice
under this Section shall be deemed to be the date of delivery thereof.

     12. WAIVERS. If either party should waive any breach of any provision of
this Agreement, such party shall not thereby be deemed to have waived any
preceding or succeeding breach of the same or any other provision of this
Agreement.

     13. COMPLETE AGREEMENT; AMENDMENTS. The foregoing including Exhibits A, B,
C and D hereto, is the entire agreement of the parties with respect to the
subject matter hereof, superseding any previous oral or written communications,
representations, understandings, or agreements with the Company or any officer
or representative thereof. Any amendment to this


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Agreement or waiver by the Company of any right hereunder shall be effective
only if evidenced by a written instrument executed by the parties hereto, upon
authorization of the Company's Board of Directors.

     14. HEADINGS. The headings of the Sections hereof are inserted for
convenience only and shall not be deemed to constitute a part hereof nor to
affect the meaning of this Agreement.

     15. COUNTERPARTS. This Agreement may be signed in two counterparts, each of
which shall be deemed an original and both of which shall together constitute
one agreement.

     16. GOVERNING LAW; VENUE. This Agreement shall be governed by and construed
under Massachusetts law. The exclusive venue for any dispute regarding the
subject matter of this Agreement shall be the Trial Department of the Middlesex
Superior Court in the Commonwealth of Massachusetts.

     17. ADVICE OF SEPARATE COUNSEL. You acknowledge that you have been advised
to review this Agreement with your own legal counsel and other advisors of your
choosing and that prior to entering into this Agreement, you have had the
opportunity to review this Agreement with your attorney and other advisors and
have not asked (or relied upon) Mintz, Levin, Cohn, Ferris, Glovsky and Popeo,
P.C. to represent you in this matter.

     If you are in agreement with the foregoing, please sign your name below and
also at the bottom of the Proprietary Information and Inventions Agreement and
Stock Option Grant Letter, whereupon this Agreement shall become binding in
accordance with its terms. Please then return this Agreement to the Company.
(You may retain for your records the accompanying counterpart of this Agreement
enclosed herewith).

                                         Very truly yours,


ACCEPTED AND AGREED:                     APPLIED SCIENCE AND
                                         TECHNOLOGY,  INC.



/s/ JILL MAUNDER                         By:/s/ RICHARD S. POST
---------------------------                 ------------------------------------
    Jill Maunder                                Dr. Richard S. Post, President


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                                                                      EXHIBIT A

                   EMPLOYMENT TERM, COMPENSATION AND BENEFITS
                                 OF JILL MAUNDER



     l. TERM. The term of the Agreement to which this Exhibit A is attached and
made a part shall be for a period from the date of this Agreement ---- through
January 31, 1999.

     2. COMPENSATION.

        (a) BASE SALARY. Your base salary ("Base Salary") shall be $5,000.00
payable on a bi-weekly basis ($130,000.00 on an annualized basis) through
January 31, 1999, payable in accordance with the Company's payroll policies.
Commencing February 1, 1999, your base salary shall be established by the Board
of Directors' Compensation Committee.

        (b) BONUSES. The Company shall establish appropriate incentive 
compensation plans ("Bonuses") for you for each fiscal year that you are
employed hereunder, commencing with Fiscal 1999 which commences on June 28,
1998, under which you shall be entitled to a bonus of up to 25% of your then
current Base Salary based on the Company attaining certain financial and other
results and also based upon individual goals to be established for you. [For
information purposes, a copy of the Company's Fiscal 1998 Plan has been provided
to you under separate cover]. Such Bonuses shall be properly approved by the
Board of Directors or the Compensation Committee of the Board of Directors.

     3. VACATION, INSURANCE AND BENEFITS; EXPENSES. You shall be entitled to all
legal holidays recognized by the Company, and three weeks paid vacation per
annum. Any unused vacation may be accrued or used in accordance with Company
policy. You shall be eligible for participation in any health, dental, and other
group insurance plans which may be established and maintained by the Company for
all full-time employees or which the Company is required to maintain by law. You
shall also be entitled to participate in any employee benefit programs which the
Company's Board of Directors may establish for Company employees generally,
including, but not limited to, bonuses and stock purchase or option plans. You
will be eligible to participate in the Company's 401(k) Plan. The Company shall
reimburse you for all usual and ordinary business expenses incurred by you in
the scope of your employment hereunder in accordance with the Company's expense
reimbursement policy.

     4. STOCK OPTIONS. You shall be entitled to receive stock options to
purchase up to an aggregate of 20,000 shares of common stock of the Company.
Such options shall be priced on the closing price of the Company's Common Stock
as reported by NASDAQ on the date you commence employment with the Company and
shall vest as follows: 20% vesting immediately and the remaining 80% vesting in
four equal annual installments on the anniversary date of such grant. A copy of
the form of option grant letter is attached hereto as EXHIBIT D. Notwithstanding

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the foregoing, in the event of a Change of Control (as defined in Section 7
herein), an additional 20% of such option shall vest upon the Change of Control
(but in any event not to exceed 100% of the original option grant).

     You shall be entitled to additional stock options as determined by the
Board of Directors' Compensation Committee in its sole discretion.

     5. RELOCATION BONUS. You shall be entitled to a one-time bonus of $30,000
if you move your permanent residence to within a twenty (20) minute automobile
commute of the Corporation's principal corporate offices on or before February
1, 1999.

     6. SEVERANCE BENEFITS.

        (a) When provided for in this Agreement, you shall be entitled to
"Severance Benefits." When used in this Agreement, the term "Severance Benefits"
shall mean a total amount equal to (i) fifty percent (50%) of your then current
annual Base Salary, plus (ii) 50% of your Bonuses earned for the Company's most
recent fiscal year. If the Company's fiscal year is changed, the Bonuses shall
be based upon your bonuses received during the Company's most recent fiscal
year. The Severance Benefits shall be paid via check to you in six (6) equal
monthly installments commencing within ten (10) days after the date of your
termination of employment with the Company.

        (b) In addition, the term "Severance Benefits" shall include the
continuation for you and your family, during the Severance Period, as defined
below, of all of the other benefits which are provided or available to you on
the last day of your actual service with the Company. For purposes of this
Agreement, the term "Severance Period" means the period of six (6) months
beginning on the Date of Termination. Notwithstanding the foregoing, such
Severance Benefits shall be reduced by any compensation you receive as an
employee or consultant from any third party during such Severance Period.

        (c) The Severance Benefits referred to above will be in addition to, and
not in substitution for, any accrued and unpaid salary, vacation, pension or
other similar retirement benefits, and unreimbursed expenses to which you may be
otherwise entitled.

     7. CHANGE IN CONTROL.

        (a) For purposes of this Agreement, "Change in Control" means and shall
be deemed to occur if any of the following occurs: (i) the acquisition by an
individual, entity or group, as defined in Section 13(d)(3) or 14(d)(2) of the
Securities Exchange Act of 1934, as amended (the "Exchange Act"), of beneficial
ownership, as defined in Rule 13d-3 promulgated under the Exchange Act, of 50%
or more of either (A) the outstanding shares of common stock, $.01 par value per
share, of the Company (the "Common Stock"), or (B) the combined voting


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<PAGE>   9
power of the voting securities of the Company entitled to vote generally in the
election of directors (the "Voting Securities"); or (ii) individuals who, on
November 21, 1997, constituted the Board of Directors of the Company (the
"Incumbent Board") cease for any reason to constitute at least a majority of the
Board of Directors of the Company; PROVIDED, HOWEVER, that any individual
becoming a director subsequent to February 2, 1998, whose election, or
nomination for election by the Company's shareholders, was approved by a vote of
at least a majority of the directors then serving and comprising the Incumbent
Board shall be considered as though such individual were a member of the
Incumbent Board, but excluding, for this purpose, any such individual whose
initial assumption of office occurs as a result of either an actual or
threatened election contest (as such terms are used in Rule 14a-11 of Regulation
14A promulgated under the Exchange Act) or other actual or threatened
solicitation of proxies or consents; or (iii) approval by the Board of Directors
or the shareholders of the Company of a (A) tender offer to acquire any of the
Common Stock or voting securities, (B) reorganization, (C) merger or (D)
consolidation, other than a reorganization, merger or consolidation with respect
to which all or substantially all of the individuals and entities who were the
beneficial owners, immediately prior to such reorganization, merger or
consolidation, of the Common Stock and voting securities beneficially own,
directly or indirectly, immediately after such reorganization, merger or
consolidation, more than 80% of the then outstanding common stock and voting
securities (entitled to vote generally in the election of directors) of the
Company resulting from such reorganization, merger or consolidation in
substantially the same proportions as their respective ownership, immediately
prior to such reorganization, merger or consolidation, of the Common Stock and
the voting securities; or (iv) Approval by the Board of Directors or the
shareholders of the Company of (A) a complete or substantial liquidation or
dissolution of the Company, or (B) the sale or other disposition of all or
substantially all of the assets of the Company, excluding a reorganization of
the Corporation under the corporate laws of Delaware.

        (b) In the event of your actual termination of employment 
contemporaneous with or following a Change in Control, except (x) because of
your death, (y) by the Company for Cause or Disability (as hereinafter defined)
or (z) by you other than for Good Reason (as hereinafter defined): (i) you shall
be entitled to receive, in lieu of the sums described in Section 6, an amount
equal to 100% of the Severance Benefits due and determined as if payable under
Section 6 above, to be paid in accordance with the terms of this Agreement; and
(ii) the following additional provisions shall apply (which provisions shall
supersede any other provisions of the Agreement, including but not limited to
Section 2 of the Agreement, to the extent such provisions are inconsistent with
the following provisions):

            (1) DISABILITY.  For purposes of this Section 7(b),  termination by
the Company of your employment based on "Disability" shall mean termination
because of your absence from your duties with the Company on a full time basis
for one hundred eighty (180) consecutive days as a result of your incapacity due
to physical or mental illness, unless within thirty (30) days after Notice of
Termination (as hereinafter defined) is given to you following such absence, you
shall have returned to the full time performance of your duties.


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            (2) GOOD REASON.  Termination by you of your employment for 
"Good Reason" shall mean termination based on:

                (A) a determination that there has been a material adverse
change in your status or position(s) as an executive officer of the Company as
in effect immediately prior to the Change in Control, including, without
limitation, a material adverse change in your status or position as a result of
a diminution in your duties or responsibilities (other than, if applicable, any
such change directly attributable to the fact that the Company is no longer
publicly owned) or the assignment to you of any duties or responsibilities which
are inconsistent with such status or position(s), or any removal of you from, or
any failure to reappoint or reelect you to, such position(s) (except in
connection with the termination of your employment for Cause or Disability or as
a result of your death or by you other than for Good Reason) and further
provided that you have given the Company notice of this material adverse change
and the Company has failed to correct such material adverse change within a
reasonable period of time (but at least 14 days after written notice from you);

                (B) a reduction by the Company (within two years following the
Change of Control) in your Base Salary as in effect immediately prior to the
Change in Control, other than a reduction in salaries generally for officers of
the Company;

                (C) the failure by the Company (within two years following the
Change of Control) to continue in effect any Plan (as hereinafter defined) in
which you are participating at the time of the Change in Control of the Company
(or Plans providing you with at least substantially similar benefits) other than
as a result of the normal expiration of any such Plan in accordance with its
terms as in effect at the time of the Change in Control, or the taking of any
action, or the failure to act, by the Company which would adversely affect your
continued participation in any of such Plans on at least as favorable a basis to
you as is the case on the date of the Change in Control or which would
materially reduce your benefits in the future under any of such Plans or deprive
you of any material benefit enjoyed by you at the time of the Change in Control;

                (D) the failure by the Company to provide and credit you with
the number of paid vacation days to which you are then entitled in accordance
with the Company's normal vacation policy as in effect immediately prior to the
Change in Control;

                (E) the failure by the Company to obtain from any Successor (as
hereinafter defined) the assent to this Agreement contemplated by Section
7(b)(7) hereof; or

                (F) any purported termination by the Company of your employment
which is not effected pursuant to a Notice of Termination satisfying the
requirements of Section 7(b)(3) below (and, if applicable, Section 7(b)(1)
above); and for

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<PAGE>   11
purposes of this Agreement, no such purported termination shall be effective.

     For purposes of this Agreement, "Plan" shall mean any compensation plan or
any employee benefit plan such as a thrift, pension, profit sharing, medical,
disability, accident, life insurance plan or a relocation plan or policy or any
other plan, program or policy of the Company intended to benefit employees.

                (3) NOTICE OF  TERMINATION.  Any  purported  termination  by the
Company or by you following a Change in Control shall be communicated by written
notice to the other party hereto which indicates the specific termination
provision in this Agreement relied upon (the "Notice of Termination").

                (4) DATE OF  TERMINATION.  "Date of  Termination"  following  a
Change in Control shall mean (A) if your employment is to be terminated for
Disability, thirty (30) days after Notice of Termination is given (provided that
you shall not have returned to the performance of your duties on a full-time
basis during such thirty (30) day period), (B) if your employment is to be
terminated by the Company for any reason other than death or Disability or by
you pursuant to Sections 7(b)(2)(F) or 7(b)(6) hereof or for any other Good
Reason, the date specified in the Notice of Termination, or (C) if your
employment is terminated on account of your death, the day after your death.

                (5) COMPENSATION UPON TERMINATION OR DURING DISABILITY; OTHER 
                    AGREEMENTS.

                    (A) During any period following a Change in Control of the
Company that you fail to perform your duties as a result of incapacity due to
physical or mental illness, you shall continue to receive your Base Salary at
the rate then in effect and any benefits or awards under any Plan shall continue
to accrue during such period, to the extent not inconsistent with such Plans,
until and unless your employment is terminated pursuant to and in accordance
with this Section 7(b). Thereafter, your benefits shall be determined in
accordance with the Plans then in effect.

                    (B) If your employment is terminated for Cause following a
Change in Control of the Company, the Company shall pay to you your Base Salary
through the Date of Termination at the rate in effect just prior to the time a
Notice of Termination is given plus any benefits or awards (including both the
cash and stock components) which pursuant to the terms of any Plans have been
earned or become payable, but which have not yet been paid to you. Thereupon,
the Company shall have no further obligations to you under this Agreement.

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<PAGE>   12


                (6) SUCCESSORS, BINDING AGREEMENT.

                    (A) The Company will seek,  by request at least five (5)
business days prior to the time a Person becomes a Successor (as hereinafter
defined), to have such Person, by agreement in form and substance satisfactory
to you, assent to the Company's obligations under this Agreement. Failure of
such Person to furnish such assent by the later of (i) three (3) business days
prior to the time such Person becomes a Successor or (ii) two (2) business days
after such Person receives a written request to so assent shall constitute Good
Reason for termination by you of your employment if a Change in Control of the
Company occurs or has occurred. For purposes of this Section, "Successor" shall
mean any person that succeeds to, or has the ability to control, the Company's
business directly, by merger or consolidation, or indirectly, by purchase of the
Company's securities eligible to vote for the election of directors.

                    (B) This Agreement shall inure to the benefit of and be
enforceable by your personal legal representatives, executors, administrators,
successors, heirs, distributees, devisees and legatees. If you should die while
any amount would still be payable to you hereunder if you had continued to live,
all such amounts, unless otherwise provided herein, shall be paid in accordance
with the terms of this Agreement to your devisee, legatee or other designee or,
if no such designee exists, to your estate.

                    (C) For purposes of Section 7, the "Company" shall include
any subsidiaries of the Company and any corporation or other entity which is the
surviving or continuing entity in respect of any merger, consolidation or form
of business combination in which the Company ceases to exist; provided, however,
for purposes of determining whether a Change in Control has occurred herein, the
term "Company" shall refer to Applied Science and Technology, Inc. or its
Successor(s).

                (7) FEES AND EXPENSES; MITIGATION.

                    (A) The Company shall reimburse you, on a current basis, for
all reasonable legal fees and related expenses incurred by you in connection
with the Agreement following a Change in Control of the Company, including
without limitation, (i) all such fees and expenses, if any, incurred in
contesting or disputing any termination of your employment or (ii) your seeking
to obtain or enforce any right or benefit provided by this Agreement, in each
case, regardless of whether or not your claim is upheld by a court of competent
jurisdiction; provided, however, you shall be required to repay any such amounts
to the Company to the extent that a court issues a final and non-appealable
order setting forth the determination that the position taken by you was
frivolous or advanced by you in bad faith.

                    (B) You shall not be required to mitigate the amount of any
payment the Company becomes obligated to make to you in connection with this
Agreement, by seeking other employment or otherwise.

                                       A-6
<PAGE>   13

                (8) TAXES.  All payments to be made to you under this Agreement
will be subject to required  withholding of federal,  state and local income and
employment taxes.

     (c) Notwithstanding any other provision of this Agreement, in the event
that any payment or benefit received or to be received by you as a result of or
in connection with a Change in Control, whether pursuant to the terms of this
Agreement or any other plan, arrangement or agreement with the Company (all such
payment and benefits being hereinafter called the "Total Payments") would
subject you to the excise tax (the "Excise Tax") imposed under Section 4999 of
the Internal Revenue Code of 1986, as amended (the "Code"), then, to the extent
necessary to eliminate any such imposition of the Excise Tax (after taking into
account any reduction in the Total Payments in accordance with the provisions of
any other plan, arrangement or agreement, if any), (a) any non-cash severance
payments otherwise payable to you shall first be reduced (if necessary, to
zero), and (b) any cash severance payment otherwise payable to you shall next be
reduced. For purposes of the immediately preceding sentence, (i) no portion of
the Total Payments the receipt or enjoyment of which you shall have effectively
waived in writing shall be taken into account, (ii) no portion of the Total
Payment shall be taken into account which in the opinion of
nationally-recognized certified public accountants (in each case as mutually
selected by you and the Company) does not constitute a "parachute payment"
within the meaning of Section 280G of the Code, including, without limitation,
by reason of Section 280G(b)(2) or (b)(4)(A) of the Code, (iii) any payments to
you shall be reduced only to the extent necessary so that the Total Payments
[other than those referred to in clauses (i) and (ii)] in their entirety
constitute reasonable compensation for services actually rendered within the
meaning of Section 280G(4)(B) of the Code or are otherwise not subject to
disallowance as deductions, in the opinion of the tax counsel or the accountants
referred to in clause (ii); and (iv) the value of any non-cash benefit or any
deferred payment or benefit included in the Total Payments shall be determined
by such accountants in accordance with the requirements of section 280G(d)(3)
and (4) of the Code (and such determination shall be reviewed by such tax
counsel).

                      [THIS SPACE INTENTIONALLY LEFT BLANK]

                                      A-7
<PAGE>   14
                                                                      EXHIBIT B



                    OUTSIDE EMPLOYMENTS AND DIRECTORSHIPS OF

                                  JILL MAUNDER


                                      None



                                      B-1
<PAGE>   15
                                                                      EXHIBIT C



                -------------------------------------------------

                PROPRIETARY INFORMATION AND INVENTIONS AGREEMENT

                -------------------------------------------------

To:  Applied Science and Technology, Inc.
     35 Cabot Road
     Woburn, Massachusetts  01801

                                                         As of February 2, 1998

     The undersigned, in consideration of and as a condition of my employment or
continued employment by you and/or by companies which you own, control, or are
affiliated with or their successors in business (collectively, the "Company"),
hereby agrees as follows:

     1. CONFIDENTIALITY. I agree to keep confidential, except as the Company may
otherwise consent in writing, and, except for the Company's benefit, not to
disclose or make any use of at any time either during or subsequent to my
employment, any Inventions (as hereinafter defined), trade secrets, confidential
information, knowledge, data or other information of the Company relating to
products, processes, know-how, designs, formulas, test data, customer lists,
business plans, marketing plans and strategies, pricing strategies, or other
subject matter pertaining to any business of the Company or any of its
affiliates, which I may produce, obtain, or otherwise acquire during the course
of my employment, except as herein provided. I further agree not to deliver,
reproduce or in any way allow any such trade secrets, confidential information,
knowledge, data or other information, or any documentation relating thereto, to
be delivered to or used by any third parties without specific direction or
consent of a duly authorized representative of the Company.

     2. CONFLICTING EMPLOYMENT; RETURN OF CONFIDENTIAL MATERIAL. I agree that
during my employment with the Company I will not engage in any other employment,
occupation, consulting or other activity relating to the business in which the
Company is now or may hereafter become engaged, or which would otherwise
conflict with my obligations to the Company. In the event my employment with the
Company terminates for any reason whatsoever, I agree to promptly surrender and
deliver to the Company all records, materials, equipment, drawings, documents
and data of which I may obtain or produce during the course of my employment,
and I will not take with me any description containing or pertaining to any
confidential information, knowledge or data of the Company which I may produce
or obtain during the course of my employment.

                                      C-1
<PAGE>   16


     3. ASSIGNMENT OF INVENTIONS.

        3.1  I hereby acknowledge and agree that the Company is the owner of all
Inventions. In order to protect the Company's rights to such Inventions, by
executing this Agreement I hereby irrevocably assign to the Company all my
right, title and interest in and to all Inventions to the Company.

        3.2  For purposes of this Agreement, "Inventions" shall mean all
discoveries, processes, designs, technologies, devices, or improvements in any
of the foregoing or other ideas, whether or not patentable and whether or not
reduced to practice, made or conceived by me (whether solely or jointly with
others) during the period of my employment with the Company which relate in any
manner to the actual or demonstrably anticipated business, work, or research and
development of the Company, or result from or are suggested by any task assigned
to me or any work performed by me for or on behalf of the Company.

        3.3  Any discovery, process, design, technology, device, or improvement
in any of the foregoing or other ideas, whether or not patentable and whether or
not reduced to practice, made or conceived by me (whether solely or jointly with
others) which I develop entirely on my own time not using any of the Company's
equipment, supplies, facilities, or trade secret information ("Personal
Invention") is excluded from this Agreement provided such Personal Invention (a)
does not relate to the actual or demonstrably anticipated business, research and
development of the Company, and (b) does not result, directly or indirectly,
from any work performed by me for the Company.

     4. DISCLOSURE OF INVENTIONS. I agree that in connection with any Invention,
I will promptly disclose such Invention to my immediate superior at the Company
in order to permit the Company to enforce its property rights to such Invention
in accordance with this Agreement. My disclosure shall be received in confidence
by the Company.

     5. PATENTS AND COPYRIGHTS; EXECUTION OF DOCUMENTS.

        5.1  Upon request, I agree to assist the Company or its nominee
(at its expense) during and at any time subsequent to my employment in every
reasonable way to obtain for its own benefit patents and copyrights for
Inventions in any and all countries. Such patents and copyrights shall be and
remain the sole and exclusive property of the Company or its nominee. I agree to
perform such lawful acts as the Company deems to be necessary to allow it to
exercise all right, title and interest in and to such patents and copyrights.

        5.2  In connection with this Agreement, I agree to execute, acknowledge
and deliver to the Company or its nominee upon request and at its expense all
documents, including assignments of title, patent or copyright applications,
assignments of such applications, assignments of patents or copyrights upon
issuance, as the Company may determine necessary or desirable to protect the
Company's or its nominee's interest in Inventions, and/or to use in

                                       C-2
<PAGE>   17
obtaining patents or copyrights in any and all countries and to vest title
thereto in the Company or its nominee to any of the foregoing.

     6. MAINTENANCE OF RECORDS. I agree to keep and maintain adequate and
current written records of all Inventions made by me (in the form of notes,
sketches, drawings and other records as may be specified by the Company), which
records shall be available to and remain the sole property of the Company at all
times.

     7. PRIOR INVENTIONS. It is understood that all Personal Inventions, if any,
whether patented or unpatented, which I made prior to my employment by the
Company, are excluded from this Agreement. To preclude any possible uncertainty,
I have set forth on Schedule A attached hereto a complete list of all of my
prior Personal Inventions, including numbers of all patents and patent
applications and a brief description of all unpatented Personal Inventions which
are not the property of a previous employer. I represent and covenant that the
list is complete and that, if no items are on the list, I have no such prior
Personal Inventions. I agree to notify the Company in writing before I make any
disclosure or perform any work on behalf of the Company which appears to
threaten or conflict with proprietary rights I claim in any Personal Invention.
In the event of my failure to give such notice, I agree that I will make no
claim against the Company with respect to any such Personal Invention.

     8. OTHER OBLIGATIONS. I acknowledge that the Company from time to time may
have agreements with other persons or with the U.S. Government or agencies
thereof, which impose obligations or restrictions on the Company regarding
Inventions made during the course of work thereunder or regarding the
confidential nature of such work. I agree to be bound by all such obligations
and restrictions and to take all action necessary to discharge the Company's
obligations.

     9. TRADE SECRETS OF OTHERS. I represent that my performance of all the
terms of this Agreement and as an employee of the Company does not and will not
breach any agreement to keep confidential proprietary information, knowledge or
data acquired by me in confidence or in trust prior to my employment with the
Company, and I will not disclose to the Company, or induce the Company to use,
any confidential or proprietary information or material belonging to any
previous employer or others. I agree not to enter into any agreement either
written or oral in conflict herewith.

     10. MODIFICATION. I agree that any subsequent change or changes in my
employment duties, salary or compensation or, if applicable, in any Employment
Agreement between the Company and me, shall not affect the validity or scope of
this Agreement.

     11. SUCCESSORS AND ASSIGNS. This Agreement shall be binding upon my heirs,
executors, administrators or other legal representatives and is for the benefit
of the Company, its successors and assigns.


                                       C-3
<PAGE>   18
     12. INTERPRETATION. IT IS THE INTENT OF THE PARTIES THAT in case any one or
more of the provisions contained in this Agreement shall, for any reason, be
held to be invalid, illegal or unenforceable in any respect, such invalidity,
illegality or unenforceability shall not affect the other provisions of this
Agreement, and this Agreement shall be construed as if such invalid, illegal or
unenforceable provision had never been contained herein. MOREOVER, IT IS THE
INTENT OF THE PARTIES THAT in case any one or more of the provisions contained
in this Agreement shall for any reason be held to be excessively broad as to
duration, geographical scope, activity or subject, such provision shall be
construed by limiting and reducing it in accordance with a judgment of a court
of competent jurisdiction, so as to be enforceable to the extent compatible with
applicable law.

     13. WAIVERS. If either party should waive any breach of any provision of
this Agreement, he or it shall not thereby be deemed to have waived any
preceding or succeeding breach of the same or any other provision of this
Agreement.

     14. COMPLETE AGREEMENT, AMENDMENTS. I acknowledge receipt of this
Agreement, and agree that with respect to the subject matter thereof the
provisions of this Key Employee Agreement of which this Exhibit C is one part,
is my entire agreement with the Company, superseding any previous oral or
written communications, representations, understandings, or agreements with the
Company or any officer or representative thereof. Any amendment to this
Agreement or waiver by either party of any right hereunder shall be effective
only if evidenced by a written instrument executed by the parties hereto, and,
in the case of the Company, upon written authorization of the Company's Board of
Directors.

     15. HEADINGS. The headings of the sections hereof are inserted for 
convenience only and shall not be deemed to constitute a part hereof nor
to affect the meaning thereof.

     16. COUNTERPARTS. This Agreement may be signed in two counterparts, each of
which shall be deemed an original and both of which shall together constitute
one agreement.

     17. GOVERNING LAW. This Agreement shall be governed by and construed under
Massachusetts law.

     18 EMPLOYMENT STATUS. Nothing in this Agreement shall affect in any manner
whatsoever the right or power of the Company to terminate the employment of the
Employee.

                                      C-4

<PAGE>   19
     IN WITNESS WHEREOF, the parties have executed this Proprietary Information
and Inventions Agreement as of the date first written above.

                                               EMPLOYEE



                                               /s/ JILL MAUNDER
                                               ---------------------------------
                                                   Jill Maunder

Accepted and Agreed:
APPLIED SCIENCE AND TECHNOLOGY,  INC.



By:/s/ RICHARD S. POST
-------------------------------------
       Dr. Richard S. Post, President


                                      C-5
<PAGE>   20


                                                                     SCHEDULE A



                            LIST OF PRIOR INVENTIONS
                                 OF JILL MAUNDER



                                                           Identifying Number or
Title             Date                                       Brief Description
-----             ----                                     ---------------------
                                     NONE


                                       C-6

<PAGE>   21

                                              EXHIBIT D (INCENTIVE STOCK OPTION)


                      APPLIED SCIENCE AND TECHNOLOGY, INC.
                                  35 Cabot Road
                           Woburn, Massachusetts 01801

 
                                                    February 2, 1998

Jill Maunder
[Address]

Dear Jill:

     I am pleased to advise you that APPLIED SCIENCE AND TECHNOLOGY, INC. (the
"Company") has, pursuant to its 1993 Stock Option Plan (the "1993 Plan"),
awarded you an incentive stock option to twenty thousand (20,000) shares of the
Common Stock, $.01 par value per share, of the Company at an exercise price of $
per share, for a total exercise price of $ . The Company is making this offer to
"share the business" with valued employees such as yourself. We hope that by
owning a piece of the Company you will continue your efforts towards helping the
Company grow and succeed.

     The following terms and conditions are applicable with respect to this
option, and your signature below shall constitute your acknowledgment and
acceptance of same:

          (a)  This option shall not be transferable under any circumstances
               except by operation of law. During your lifetime, this option is
               only exercisable by you, and after your death, is only
               exercisable by your estate.

          (c)  The price at which this option may be exercised shall be $ per
               share, for a total exercise price of $ .00.

          (d)  This option is exercisable commencing immediately and at any time
               hereafter through ten years from today's grant date, subject to
               the following terms:

               (1)  In the event of termination of your employment with the
                    Company (or a parent or subsidiary of the Company) for any
                    reason other than death or disability as defined in Internal
                    Revenue Code Section 22(e)(3), as amended (the "Code"), all
                    unexercised options shall terminate immediately.

               (2)  In the event of termination of your employment as a result
                    of your death, the outstanding options exercisable by you at
                    the date of your death may

                                       E-1
<PAGE>   22

                    be exercised by your estate until one (1) year from the date
                    of your death, but in any event no later than January 31,
                    2008.

               (3)  In the event of termination of your employment as a result
                    of your disability, as above defined, or in the event of a
                    disability that lasts for more than ninety (90) days, all
                    outstanding options exercisable by you at the date of such
                    termination shall terminate one (1) year from the date your
                    employment terminates, but in any event no later than
                    January 31, 2008.

               (4)  Notwithstanding anything herein to the contrary, the maximum
                    extent to which this option may be exercised is as follows:

                          DATES                                      UP TO
                          -----                                      ------
                    2/2/98  -  1/31/99                                 20%
                    2/1/99  -  1/31/00                                 40%
                    2/1/00  -  1/31/01                                 60%
                    2/1/01  -  1/31/02                                 80%
                    2/1/02  -  1/31/08                                100%

               (e)  This option may not be exercised as to less than one hundred
                    (100) shares at any one time unless it is being exercised in
                    full and the balance of the shares subject to this option is
                    less than one hundred (100).

               (f)  The shares of Common Stock underlying this option and the
                    exercise price therefore shall be appropriately adjusted
                    from time to time for stock splits, reverse splits, stock
                    dividends and reclassifications of shares.

               (g)  In the event of a sale or acquisition of substantially all
                    of the stock or assets of the Company, the Company shall
                    give at least thirty (30) days' notice of such an event to
                    you and you may exercise up to 100% of the vested portion of
                    this option; if you do not exercise the option within thirty
                    (30) days of such notice, all unexercised portions of this
                    option shall terminate and be of no further force or effect.
                    Notwithstanding the foregoing, additional shares underlying
                    this option grant may vest in accordance with the provisions
                    of Exhibit A of your Employment Agreement of even date with
                    the Company.

     This opportunity to purchase stock in the Company is being offered because
of the Company's desire to reward continuing loyal service. Exercising options
may not be a prudent business decision for some employees. Therefore, we urge
you to review this opportunity carefully and make a decision to exercise options
only if your personal financial situation makes this a wise choice.

                                      E-2

<PAGE>   23


     When you wish to exercise this stock option, please refer to the provisions
of this letter and then correspond in writing with the Secretary of the Company.
Further, please indicate your acknowledgment and acceptance of this option by
signing the enclosed copy of this letter and returning it to the undersigned.

                                       Very truly yours,

                                       APPLIED SCIENCE AND TECHNOLOGY, INC.




                                        By:_____________________________________
                                           John M. Tarrh, Senior Vice President


ACKNOWLEDGMENT AND ACCEPTANCE:



--------------------------------------
Jill Maunder



                                      E-3