<PAGE>
EXHIBIT 5.1
[Letterhead of Dunkley, Bennett, Christensen & Madigan, P.A.]
January 8, 2001
Entegris, Inc.
3500 Lyman Boulevard
Chaska, MN 55318
Re: Registration Statement on Form S-8
Ladies and Gentlemen:
We have acted as counsel to Entegris, Inc., a Minnesota corporation (the
"Company"), in connection with the proposed registration by the Company pursuant
to a Registration Statement on Form S-8 of an aggregate of 20,287,194 shares of
Common Stock, par value $0.01 per share (the "Shares"), to be offered under the
Entegris, Inc. Employee Stock Ownership Plan, the Entegris, Inc. 1999 Long-Term
Incentive and Stock Option Plan, the Entegris, Inc. Outside Directors' Stock
Option Plan and the Entegris, Inc. Employee Stock Purchase Plan (the "Plans").
We have examined such documents and have reviewed such questions of law as
we have considered necessary and appropriate for the purposes of the opinions
set forth below.
In rendering our opinions set forth below, we have assumed the authenticity
of all documents submitted to us as originals, the genuineness of all signatures
and the conformity to authentic originals of all documents submitted to us as
copies. As to questions of fact material to our opinions, we have relied upon
certificates or representations of officers of the Company, public officials and
others.
Based on the foregoing, we are of the opinion that the Shares have been
duly authorized and, upon issuance, delivery and payment therefor in accordance
with the terms of the Plan, will be validly issued, fully paid and
nonassessable.
Our opinions expressed above are limited to the laws of the State of
Minnesota.
We hereby consent to the filing of this opinion as an exhibit to the
above-described Registration Statement.
Very truly yours,
/s/ Dunkley, Bennett, Christensen & Madigan, P.A.
