Radiation imagery chemistry: process – composition – or product th – Imaging affecting physical property of radiation sensitive... – Forming nonplanar surface
Reexamination Certificate
2002-08-12
2003-11-04
Schilling, Richard L. (Department: 1752)
Radiation imagery chemistry: process, composition, or product th
Imaging affecting physical property of radiation sensitive...
Forming nonplanar surface
C430S271100, C430S327000, C430S331000, C510S175000, C510S176000, C510S421000, C516S204000, C568S616000, C568S855000
Reexamination Certificate
active
06641986
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates generally to a method for the manufacture of semiconductor devices. More specifically, the present invention relates to an aqueous solution for treating the surface of a substrate and a method for using same.
By the year 2004, the newly updated International Technology Roadmap for Semiconductors (ITRS) states that critical features, as measured by the gate length of MPUs and the ½ pitch of Dynamic Random Access Memory (DRAM) devices, will break the 100 nm barrier. Critical Dimension (CD) is one process control lever that is closely monitored. At the 90 nm technology node, the CD control, as measured by the 3-sigma requirement, will approach 3.0 nm which is approximately the size of the polymer molecules that comprise the photoresist. Furthermore, the size of the wafers being processed is growing larger. As a result, this magnitude of control has to be reproduced on larger, 300 mm wafers.
Paralleling the reduction in line geometries is the need for tighter control over the lithographic process. Lithography is a critical process for the manufacture of semiconductor components and integrated circuits (IC). In brief, the typical lithography process involves coating a substrate with a positive or negative resist layer, exposing the substrate to a radiation source to provide an image, and developing the substrate to form a patterned resist layer on the substrate. This patterned layer acts as a mask for subsequent substrate patterning processes such as etching, doping, and/or coating with metals, other semiconductor materials, or insulating materials.
One strategy for addressing the need for tighter CD control may be to improve the development process. This approach becomes increasingly important because the next generation of photoresists for 193 nm lithography will be more hydrophobic, and, thus, be more resistant to developer wetting. Poor wetting of the photoresist by the developer can lead to defects as well as a reduction in CD control. It is anticipated that these problems may be amplified with the move towards 300 mm processing because more surface area on the substrate will need to be simultaneously wetted. The current method to improve the wetting on the resist surface prior to photoresist development uses deionized water (DI). This method, however, may not be adequate to prepare the surface of the substrate for the future generation of resists.
The ability to reduce the surface tension of water at the air and liquid interface is of great importance in a variety of applications because decreased surface tension generally relates to increased wetting of water on the substrate surface. Surface tension reduction in water-based systems is generally achieved through the addition of surfactants. Equilibrium surface tension performance is important when the system is at rest, though the ability to reduce surface tension under dynamic conditions is of great importance in applications where high surface creation rates are used, i.e., spin coating, rolling, spray coating, and the like. Dynamic surface tension provides a measure of the ability of the solution to lower surface tension and provide wetting under high speed application conditions. Further, in certain applications such as during spray application, it is advantageous that the surfactant reduces the surface tension of the formulation in a manner that minimizes bubble generation and foaming.
Surfactants have been added to pre-rinse solutions prior to the development step to improve the contrast in positive photoresist developing. For example, EP 0231028 B1 describes treating a photoresist film in a pre-dip bath containing an organic base and cationic solution and rinsing with DI water prior to developing the photoresist film in a developer solution containing an organic base and fluorochemical surfactant. Similarly, EP 0178495 B1 describes treating a photoresist film with a pre-dip solution containing an aqueous alkali metal base and a fluorochemical or carboxylated surfactant and rinsing with DI water prior to developing the photoresist film in a developer solution containing an aqueous alkali metal hydroxide and optionally a fluorochemical or carboxylated surfactant. Both references employ a two-solution process that includes a DI water rinse step between the pre-dip and development steps. It may be desirable, however, to treat the surface of the substrate and achieve the benefits of improved wetting in fewer steps. It may also be desirable to treat the surface of the substrate with a dynamic rather than a static rinse.
Japanese patent application 2002/148821 describes coating a wafer having a fluorine and silicon-based polymer resist with a fluorosurfactant to improve the wettablity of the developer.
Accordingly, there is a need in the art to provide an aqueous solution to prepare the surface of a substrate prior to development or other steps within the lithography process. There is a further need to provide aqueous solutions that improve the wettability of the surface, for example, by lowering the contact angle of a subsequently applied processing solution on the substrate. There is also a need in the art for aqueous solutions comprising a surfactant that works effectively in high-speed applications without undesirable foaming or bubble generation. Further, there is a need in the art for an aqueous solution that reduces the number of treatment steps.
All references cited herein are incorporated herein by reference in their entirety.
BRIEF SUMMARY OF THE INVENTION
The present invention satisfies some, if not all, of the needs of the art by providing an aqueous solution comprising one or more acetylenic diol type surfactants to prepare the surface of a substrate. The aqueous solution of the present invention may be used to modify the character of the substrate surface from a hydrophobic surface to a substantially more hydrophilic surface, or vice versa. As a result of this treatment, the substrate may exhibit improved wettability, enhanced development, improved CD control, reduced defects, and/or increased throughput by achieving faster developing speeds.
Specifically, in one embodiment of the present invention, there is provided a method for improving the wettability of a substrate. The method comprises the steps of contacting the substrate with an aqueous solution comprising about 10 ppm to about 10,000 ppm of at least one surfactant having the formula (I) or (II):
wherein R
1
and R
4
are a straight or a branched alkyl chain having from 3 to 10 carbon atoms; R
2
and R
3
are either H or an alkyl chain having from 1 to 5 carbon atoms; and m, n, p, and q are numbers that range from 0 to 20; coating the substrate with a resist coating to provide a resist-coated substrate; exposing at least a portion of the resist-coated substrate to a radiation source for a time sufficient to provide a pattern on the resist coating; and applying the aqueous developer solution to the substrate to dissolve at least a portion of the resist coating. In certain embodiments, the contacting step may be performed after the coating step.
In a further embodiment of the present invention, there is provided a method for improving the wettability of a substrate. The method comprises the steps of contacting a substrate with an aqueous solution comprising about 10 ppm to about 10,000 ppm of at least one surfactant having the formula:
wherein R
1
and R
4
are a straight or a branched alkyl chain having from 3 to 10 carbon atoms; R
2
and R
3
are either H or an alkyl chain having from 1 to 5 carbon atoms; and m, n, p, and q are numbers that range from 0 to 20; coating the substrate with a resist coating to provide a resist-coated substrate; exposing at least a portion of the resist-coated substrate to a radiation source for a time sufficient to provide a pattern on the resist coating; and applying the aqueous developer solution to the substrate to dissolve at least a portion of the resist coating. In certain embodiments, the contacting step is performed before the coating step.
In yet a
Barber Leslie Cox
Karwacki Eugene Joseph
King Danielle Megan
Zhang Peng
Air Products and Chemicals Inc.
Morris-Oskanian Rosaleen P.
Schilling Richard L.
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