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Si-N Attenuated Phase Shift Layer for Phase Shift Mask Application

IP.com Disclosure Number: IPCOM000109412D
Original Publication Date: 1992-Aug-01
Included in the Prior Art Database: 2005-Mar-24
Document File: 2 page(s) / 96K

Publishing Venue

IBM

Related People

Chieu, T: AUTHOR [+3]

Abstract

There is much interest in improving lithography mask technology by the addition of a dielectric layer to produce an optical phase shift of 180~ in regions of the mask. One particular type of mask involves the use of an attenuating layer, such as thin Cr, that transmits a small amount, typically of order 4 to 8%, of the incident UV energy, in conjunction with the dielectric layer.

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Si-N Attenuated Phase Shift Layer for Phase Shift Mask Application

       There is much interest in improving lithography mask
technology by the addition of a dielectric layer to produce an
optical phase shift of 180~ in regions of the mask.  One particular
type of mask involves the use of an attenuating layer, such as thin
Cr, that transmits a small amount, typically of order 4 to 8%, of the
incident UV energy, in conjunction with the dielectric layer.

      A difficulty with fabricating this structure is that the light
transmission is extremely sensitive to the thickness of the Cr layer.
For example, it can be estimated that a film of thickness of about
145A is required for this application and the tolerance requirement
is of order one nanometer to maintain transmission in the range 4 to
8%.

      As an alternative, we described a method of preparing a phase
shift layer that has absorption (at the UV wavelength of the
lithographic system) that can be controlled by gas pressure within
the sputtering system during the layer deposition process.  The
amount of absorption is adjusted so that a film that is of the
correct thickness to provide a phase shift of 180 degrees, has just
the desired amount of transmission.  The advantage of this method is
that the light attenuation and phase shift are achieved with a single
layer.  In addition, the thickness tolerance can now be of order 10
nm.

      The data shown in Fig. 1 are for films deposited by RF
sputtering using a silicon target and a sputtering gas mixture
consisting of argon and nitrogen.  During sputterin...