Radiation imagery chemistry: process – composition – or product th – Imaging affecting physical property of radiation sensitive... – Making electrical device
Reexamination Certificate
2001-07-25
2003-11-25
Huff, Mark F. (Department: 1756)
Radiation imagery chemistry: process, composition, or product th
Imaging affecting physical property of radiation sensitive...
Making electrical device
C430S009000, C430S014000, C430S015000, C430S311000, C430S313000, C430S322000, C430S323000, C430S394000, C427S489000
Reexamination Certificate
active
06653054
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to photolithography techniques and aims to provide resins sensitive to extreme ultraviolet light (EUV) wavelengths for making masks resisting plasma etching and enabling structures with dimensions of less than 0.1 &mgr;m to be obtained.
2. Description of the Related Art
The expression “extreme ultraviolet light” generally refers to light at wavelengths less than 100 nm and in particular at wavelengths of around 11 to 13 nm.
Light in the range of wavelengths from 300 to 100 nm is generally referred to as deep ultraviolet light. The expression “ultraviolet light” refers to light at wavelengths from 700 to 300 nm.
The wavelengths routinely used in photolithography are in the deep ultraviolet (DUV) range, are generally of the order of 193 to 248 nm, and enable structures with critical dimensions from 0.18 &mgr;m to 0.12 &mgr;m to be obtained.
At these wavelengths some resins already exhibit photo-ablation, given that the radiation energy is of the order of 6.4 eV at a wavelength of 193 nm. At a wavelength of 13 nm, which corresponds to an energy of 92.5 eV, photo-ablation or partial sublimation by depolymerization should be observed in many photolithography mask resins.
These observations have led to the development of various compositions of the materials of photolithography masks since it is no longer necessary to add photosensitive substances or acid generators to make them sensitive, the materials being quasi-inherently sensitive to wavelengths from 11 to 13 nm.
Modern photolithography techniques use a 193 nm (DUV) ArF excimer laser and enable the fabrication of structures with critical dimensions of the order of 0.1 &mgr;m using phase-shift masks (PSM).
Problems with the transparency of the masks already begin to appear at this wavelength, and at shorter wavelengths other limitations are operative, for example excessive absorption of conventional chemical amplification resins, absence of transparency of the silica at wavelengths of less than 160 nm, which imply the use of CaF
2
, and the necessity to operate in a flow of nitrogen or in a vacuum at wavelengths from 172 nm.
For the above reasons, and to push back the limitations of deep UV lithography without having recourse to PSM techniques, many experiments have been conducted using extreme ultraviolet light wavelengths of around 11 nm to 13 nm, and research has also been conducted into X-ray beam lithography, electron beam lithography and ion beam lithography.
One of the main problems arising from the use of lithography techniques below 193 nm lies mainly in the design of the lithography tool. In particular, the problem of absorption of light in the optics is often encountered, and the only solution is to use reflective optics (mirrors and mask), rather than refractive optics, and what is more in a vacuum. “Photorepeaters” (die by die image repetition equipment) operating by reflection have already been used at a wavelength of 13.4 nm, for example. Also, initial experiments indicate that multilayers of silicon and molybdenum offer reflection ratios of the order of 70% at a target EUV wavelength of 13 nm (92.5 eV). These multilayers have low absorption and refractive indices respectively greater than and less than 1 in the range from 70 to 100 eV that corresponds to wavelengths from 18 to 12 nm. These masks are made by depositing palladium on multilayers of silicon and molybdenum.
As a general rule, the sources used to produce EUV radiation are either a synchrotron or a plasma generated by firing a pulsed laser onto a metallic (Cu, Au and Sn) target or using xenon “cluster” gas jets.
With regard to photosensitive resins, given the generally high absorption of the polymers used at short wavelengths, it can be assumed that the sensitivity of photosensitive resins in the EUV will be high, but the depth of penetration very small, which is why the use of top surface imaging (TSI) techniques is generally recommended, such as the silylation technique that consists of diffusing a reactive gas based on disilane, the use of double layers consisting of organosilicon resin and planarizing resin, or the use of very thin sensitive layers or photo-ablation layers.
As just explained, given the high absorption of the prior art resins at short wavelengths, the sensitivity of polymers to EUV radiation is generally high, but the depth of penetration could prove to be too small to authorize the use of resin layers sufficiently thick to act as an etching mask, regardless of the technique employed.
In particular, for top surface imaging resins using the silylation technique that involves diffusing a reactive gas based on disilane in the exposed areas, the main limitations concern the non-uniformity of silylation, both locally and globally, due to diffusion of the gas and to swelling of the exposed parts, and an increased sensitivity of the resin to many parameters, such as the working pressure or the wavelength used.
Top surface imaging resins using the double layer technique with organosilicon resin and planarizing resin appear to be more beneficial than silylation techniques. This is because organosilicon resins have great potential because they can consist of molecules that are either richer in carbon or richer in silica which, after EUV exposure, adopt a positive or negative behavior on development. This positive or negative behavior is obtained by developing the exposed parts which are richer in silica in an acid or basic solution or by developing the unexposed parts in a solvent. Experiments have been conducted at 193 nm on polysiloxanes and polysilazanes to fabricate 0.1 to 0.2 nm structures and have shown a satisfactory sensitivity from 30 to 100 mJ/cm
2
at 193 nm. At 13.4 nm the energy is much higher (92.5 eV) and even leads to excitation of the Si 2p and Si 2s electrons. It has nevertheless become apparent that absorption is still the limiting factor.
Although promising, this approach remains a top surface imaging technique, given the absorption of light at the surface of the layers, and gives rise to associated problems with lateral diffusion and resistance of the patterns.
Another approach previously mentioned consists in investigating very thin single layers of resin given the high absorption of EUV in resins such as polysiloxane resins, such as those already mentioned above, or methacrylic esters.
Recent experiments have used resins based on HEMA (hydroxyethyl methacrylate) methacrylic esters without chemical amplification and show acceptable sensitivity at 193 nm to electron beams and to X-ray beams.
However, these resins are necessarily very thin and do not constitute a sufficiently resistant mask.
With regard to the use of photo-ablation layers, resins exhibiting this behavior have been tried at 193 nm with relative success, given the low exposure energy (6.4 eV).
At a wavelength of 13 nm the energy is much higher (92.5 eV) and enables easier photo-ablation of some polymers or sublimation by depolymerization of intrinsically unstable polymers.
Experiments have been conducted with intrinsically unstable polyphthalaldehyde polymers, synthesized below its floor temperature, i.e. at a temperature below which the equilibrium of the polymerization and depolymerization reactions would be shifted toward depolymerization, and stabilized by grafting a stable molecule to the end of the chain.
The main problem encountered when using single photo-ablation layers is that they are not resistant to plasma etching precisely because of their capacity for photo-ablation and do not constitute functional masking layers.
The object of the invention is therefore to palliate the problems encountered in the prior art and to enable the execution of photolithography using extreme ultraviolet light radiation.
SUMMARY OF THE INVENTION
In accordance with one aspect of the invention the prior art problems are solved by providing a semiconductor substrate etching masking layer to which a pattern to be etched can be transferred by photolithography at extreme ultraviolet light wa
Barreca Nicole
France Telecom
Huff Mark F.
Meyertons Eric B.
Meyertons Hood Kivlin Kowert & Goetzel P.C.
LandOfFree
Resin, a double resin layer for extreme ultraviolet light... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Resin, a double resin layer for extreme ultraviolet light..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Resin, a double resin layer for extreme ultraviolet light... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3152761