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A HIGH CONTRAST NEGATIVE E-BEAM RESIST PROCESS FOR THE AEBLE-150 DIRECT-WRITE SYSTEM

IP.com Disclosure Number: IPCOM000006160D
Original Publication Date: 1991-Jul-01
Included in the Prior Art Database: 2001-Dec-10
Document File: 4 page(s) / 172K

Publishing Venue

Motorola

Related People

C.M Brown: AUTHOR [+2]

Abstract

The application of direct-write E-beam lithog- raphy using an AEBLE 150 depends heavily upon resist sensitivity. If the resist is not sensitive, large layer to layer misalignments can result due to the space charge regions set up in the resist patterning layer from the large deposited charge. This charge induced misalignment effect is especially prevalent when carrying out circuit interconnect layouts on advanced Bipolar device backends.

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MOTOROLA INC. Technical Developments Volume 13 July 1991

A HIGH CONTRAST NEGATIVE E-BEAM RESIST PROCESS FOR THE AEBLE-150 DIRECT-WRITE SYSTEM

by CM Brown and J.N. Helberi

  The application of direct-write E-beam lithog- raphy using an AEBLE 150 depends heavily upon resist sensitivity. If the resist is not sensitive, large layer to layer misalignments can result due to the space charge regions set up in the resist patterning layer from the large deposited charge. This charge induced misalignment effect is especially prevalent when carrying out circuit interconnect layouts on advanced Bipolar device backends.

  Negative E-beam resists are usually sensitive (see Table I), but seldom are they sensitive with high contrast or resolution and also dry-process compatible which is required for direct-write wafer fabrication efforts. Of course, sensitive E-beam resists that are not dry-process compatible are not usable for making integrated circuits and are basically relegated to mask or reticle fabrication applications where wet etching is still quite widely employed. The dry-process compatible resists of Table II are generally less sensitive, hence, they generally require larger E-beam exposures or deposited radiation charge to function; when they are more sensitive, they usually exhibit contrast values ~2 and submicron resolution and proximity are difficult problems for these systems. Here, we report an extensively optimized process for a chemically amplified resist, SAL 603, which pos- sesses great contrast/resolution without sacrificing wafer process compatibility.

In 1990, Dammel et al (1) and Takahashi et al (2) reported t&component resists for E-beam and X-ray

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appllcatlons which function via a chemical amplification dissolution reduction crosslinking mechanism. For these systems, the exposed image is created by an acid-catalyzed chemical crosslinking reaction utilizing the acid produced via radiation induced acid formation from the photoacid generating component of the resist. Since the acid produced is not consumed in the dissolution inhibiting crosslinking reaction, it can carry out much more solubility reduction or image formation in the exposed area per unit dose than that which occurs for the

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classical free radical type systems (Table I). Hence, this type of system is very sensitive and overcomes the sensitivity problems of the systems of Table II. The sensitivity of SAL 603 depends on the substrate and the feature size, but typical exposures range from OS- 30 pC/cm', approaching an order of magnitude or better than for the corresponding conditions for the systems of Table II. SAL 603 contrast values >3 are typical; this level of contrast value far exceeds those for most of the systems of Tables I and II.

  In 1989, an early commercial sample of XP-90- 104A, now called SAL 603 product, was received for testing on the Motorola AEBLE 150 system in ATC. The process recommended by the vendor was not a high perf...