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                                                                    EXHIBIT 99.4

                                     LOGO
                              1010 RINCON CIRCLE
                          SAN JOSE, CALIFORNIA 95131
                                                                   July 7, 1997
 
Dear Stockholder:
 
  You are cordially invited to attend a special meeting ("OnTrak Special
Meeting") of the stockholders of OnTrak Systems, Inc. ("OnTrak") to be held at
the offices of OnTrak, 1010 Rincon Circle, San Jose, California, on August 5,
1997, at 2:00 p.m., local time. At the OnTrak Special Meeting, you will be
asked to consider and vote upon the approval and adoption of an Agreement and
Plan of Merger, dated as of March 24, 1997 (the "Merger Agreement"), pursuant
to which OnTrak will be acquired by Lam Research Corporation ("Lam") by means
of a merger (the "Merger") of Omega Acquisition Corporation, a wholly-owned
subsidiary of Lam, with and into OnTrak, resulting in OnTrak becoming a
wholly-owned subsidiary of Lam.
 
  The Merger Agreement provides for the conversion and exchange of each and
every outstanding share of common stock of OnTrak, par value $0.0001 per share
("OnTrak Common Stock") into 0.83 of a share of common stock of Lam, par value
$0.001 per share ("Lam Common Stock"), subject to the following adjustment
(the "Exchange Ratio"). If the average of the daily closing sale prices per
share of the Lam Common Stock as reported on the Nasdaq National Market on the
ten trading days ending the eighth trading day preceding the OnTrak Special
Meeting (the "Lam Closing Value") falls below certain thresholds specified in
the Merger Agreement, then Lam may elect to adjust the Exchange Ratio to that
number of shares of Lam Common Stock equal to $24.90 divided by the Lam
Closing Value. If Lam determines not to adjust the Exchange Rate in those
circumstances, then OnTrak has the option to terminate the Merger Agreement.
If adjusted, the Exchange Ratio will be fixed prior to the OnTrak Special
Meeting and the special meeting of stockholders of Lam. Stockholders may
ascertain whether Lam has adjusted the Exchange Ratio or whether OnTrak has
terminated the Merger Agreement by phoning 1-888-LAM-TRAK or logging onto the
World Wide Web at http://www.lamrc.com at any time after July 25, 1997. If,
subsequent to the mailing of the Proxy Card, you wish to revoke or change your
vote, you may do so by phoning 1-888-LAM-TRAK or logging onto the World Wide
Web at http://www.lamrc.com at any time after July 25, 1997, and following the
instructions provided by the messages thereon.
 
  Following the Merger, based on the number of shares of Lam Common Stock and
OnTrak Common Stock outstanding as of March 31, 1997 and an Exchange Ratio of
0.83 of a share of Lam Common Stock for each share of OnTrak Common Stock, the
former stockholders of OnTrak will hold approximately 6,422,165 shares or
17.3% of the Lam Common Stock. In addition, each outstanding option or right
to purchase OnTrak Common Stock under OnTrak's stock option and stock purchase
plans will be assumed by Lam and will be converted into an option or right to
purchase Lam Common Stock, with appropriate adjustments, based upon the
Exchange Ratio, made to the number of shares issuable under the option and to
the exercise or purchase price of each option or right. On June 25, 1997, the
last practicable date prior to the printing of the Joint Proxy
Statement/Prospectus, the last sale prices of OnTrak Common Stock and Lam
Common Stock as reported on the Nasdaq National Market, were $28.75 and
$35.75, respectively.
 
  Pursuant to the Merger Agreement, an Office of the Chairman will be created
at Lam and will include Roger D. Emerick, the current Chairman of the Board
and Chief Executive Officer and me. Mr. Emerick will be the Chairman of the
Board, and as contemplated by the Merger Agreement, I will enter into an
employment agreement with Lam pursuant to which I will serve as Chief
Executive Officer of Lam. In addition, the Lam Board of Directors will be
expanded, and Richard J. Elkus, Jr. and I, currently directors of OnTrak, will
be appointed to the Board of Directors of Lam.
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  In the material accompanying this letter, you will find a Notice of Special
Meeting of Stockholders, a Joint Proxy Statement/Prospectus and a Proxy Card.
In addition to describing the terms and conditions of the Merger Agreement,
the enclosed Joint Proxy Statement/Prospectus sets forth information,
including summary financial data about Lam and OnTrak. The complete text of
the Merger Agreement appears as Annex A to the Joint Proxy
Statement/Prospectus. Please carefully review all of these materials and
consider the information contained in them. Your vote on the Merger is
important.
 
  Approval of the Merger Agreement requires the affirmative vote of the
holders of a majority of the outstanding shares of OnTrak Common Stock.
Certain executive officers and directors and other stockholders owning an
aggregate of approximately 26% of the outstanding shares of OnTrak have
entered into agreements pursuant to which they have agreed to vote all of the
shares of OnTrak Common Stock held by them in favor of the Merger.
 
  AFTER CAREFUL CONSIDERATION, YOUR BOARD OF DIRECTORS HAS UNANIMOUSLY
APPROVED THE MERGER AGREEMENT AND THE TRANSACTIONS CONTEMPLATED THEREBY AND
HAS CONCLUDED THEY ARE FAIR TO AND IN THE BEST INTERESTS OF ONTRAK AND ITS
STOCKHOLDERS. YOUR BOARD OF DIRECTORS UNANIMOUSLY RECOMMENDS A VOTE IN FAVOR
OF THE MERGER.
 
  Stockholders are urged to review carefully the information contained in the
accompanying Notice of Special Meeting and Joint Proxy Statement/Prospectus,
including in particular the information under the captions "Risk Factors,"
"OnTrak Special Meeting--Recommendations of OnTrak Board of Directors," "The
Merger and Related Transactions--Joint Reasons For the Merger," "--OnTrak's
Reasons For the Merger" and "--Material Contacts and Board Deliberations"
prior to making any voting decision in connection with their OnTrak Common
Stock.
 
  Regardless of the size of your holdings, it is important that your shares be
voted at the OnTrak Special Meeting. All stockholders are invited to attend
the OnTrak Special Meeting in person. Whether or not you plan to attend the
OnTrak Special Meeting in person, please complete, sign and promptly return
the enclosed proxy card in the enclosed postage-prepaid envelope to assure
representation of your shares. You may revoke your proxy at any time before it
has been voted, and if you attend the OnTrak Special Meeting you may vote in
person even if you have previously returned your Proxy Card. Your prompt
cooperation will be greatly appreciated.
 
                                          Sincerely,

                                          /s/ James W. Bagley

                                          James W. Bagley
                                          Chairman and Chief Executive Officer
 
                YOUR PROXY IS IMPORTANT--PLEASE VOTE PROMPTLY.
