Semiconductor device manufacturing: process – Chemical etching
Reexamination Certificate
2000-06-27
2001-08-21
Powell, William (Department: 1765)
Semiconductor device manufacturing: process
Chemical etching
C216S049000, C430S313000, C438S710000, C438S725000
Reexamination Certificate
active
06277750
ABSTRACT:
TECHNICAL FIELD
This invention relates to a novel composition for a bottom anti-reflective coating composition, a method of forming a bottom anti-reflective coating between a substrate and a photoresist layer using the bottom anti-reflective coating composition and manufacturing integrated circuits utilizing a photolithography method, and novel polymer dyes. More particularly this invention relates to a composition for a bottom anti-reflective coating comprising at least a solvent and a novel polymer dye having recurrent cyclic acetal units, and a method of forming a bottom anti-reflective coating by using the composition and manufacturing integrated circuits by utilizing a photolithography method, novel polymer dyes, and a method of producing thereof.
BACKGROUND ART
In manufacturing integrated circuits and active elements and interconnecting structures within microelectronic devices, a photolithography technique using photoresist compositions is utilized. In general the manufacturing of the integrated circuits or microelectronic devices are conducted as followed. That is, first, a photoresist material dissolved in a solvent is applied on a substrate such as silicon wafer by spin coating. The substrate coated with resist is then baked at elevated temperatures to evaporate any solvent in the photoresist composition and to form a thin photoresist layer with good adhesion to the substrate. The thin photoresist layer on the wafer was subjected to an imagewise exposure to radiation in the range of 150 to 450 nm wavelength, such as visible or ultraviolet (UV) rays. The imagewise exposure may also be conducted by electron beam or X-ray radiation in place of such visible or UV rays. In the exposed areas of the photoresist layer the chemical transformation arises by the exposure. After the imagewise exposure, the substrate with an imagewise exposed resist layer was subjected to developing process using an alkaline developer to dissolved out either the unexposed (negative-working resist) or exposed (positive-working resist) areas. The opened areas on the substrate formed by dissolving out the resist are subjected to additional unselective processing steps to manufacture final integrated circuits or electronic devices.
In manufacturing integrated circuits and the like, the high degree of integration has been intended and, in recent years, in order to attain a higher degree of integration techniques for still more decreasing feature sizes are required. Therefore lithographic techniques using conventional near UV, such as g-line (436 nm) and i-line (365 nm) shift to imaging processes using radiation of shorter wavelength, such as middle UV (350-280 nm), or deep UV (280-150 nm). The latter especially employs KrF (248 nm) or ArF (1 93 nm) excimer laser radiation. Excimer laser radiation sources emit monochromatic radiation. Highly sensitive, excimer laser compatible chemically amplified, positive- or negative-working deep UV photoresist compositions offering excellent lithographic performance and high resolution capability have become available recently. Due to their chemical compositions and their image formation mechanisms, state-of-the-art chemically amplified photoresist compositions are usually transparent at the exposure wavelength, and do not exhibit a pronounced sensitivity owing to poisoning effects induced by base contaminants present at the photoresist-substrate or photoresist-air interfaces, respectively. While appropriate deep-UV exposure tools in combination with the high performing photoresists are capable of patterning structural elements with dimensions below quarter micron design rules, tendency of arising image distortions and displacements due to some optical effects become conspicuous in such high resolution image. Therefor the method of forming resist images not affected by such optical effects and having good reproducibility are strongly required.
One of the problems caused by such optical effects is “standing wave” formation which is well known in the art and arise from substrate reflectivity and thin film interference effects of the monochromatic radiation. Another problem is “reflective notching” known in the art due to light reflection effects resulting from highly reflective topographic substrates. In single layer resist processes it is difficult to conduct the linewidth uniformity control due to the reflective notching. Certain reflective topographical features may scatter light through the photoresist film, leading to linewidth variations, or in other case, resist loss. Such problems are extensively documented in the literature, e.g. (i) M. Horn, Solid State Technol., 1991(11), p. 57 (1991), (ii) T. Brunner, Proc. SPIE 1466, p. 297 (1991), or (iii) M. Bolsen et al., Solid State Technol., 1986(2), p. 83, (1986).
Thin film interference generally results in changes of linewidth by variations of the substantial light intensity in the resist film as the thickness of the resist changes. These linewidth variations are proportional to the swing ratio (S) defined by following equation (1) and must be minimized for better linewidth control.
S=4(R
1
R
2
)
½
e
−&agr;D
(1)
Wherein R
1
is the reflectivity at the resist-air interface, R
2
is the reflectivity of the resist-substrate interface, &agr; is the resist optical absorption coefficient, and D represents the resist film thickness.
One of lithographic techniques to overcome the above-mentioned problems during pattern formation on reflective topography is addition of radiation absorbing dyes to the photoresists as described in U.S. Pat. Nos. 4,575,480 or 4,882,260. This corresponds to an increase of the optical absorption coefficient a in equation (1) above. When a dye is added to the photoresist to form a radiation sensitive film having high optical density at the exposure wavelength, drawbacks such as loss of resist sensitivity, resolution and depth-of-focus capability, contrast deterioration, and profile degradation are encountered. In addition, difficulties during subsequent hardening processes, thinning of the resists in alkaline developers and sublimation of the dye during baking of the films may be observed.
Top surface imaging (TS1) processes, or multi layer resist arrangements (MLR) as described in U.S. Pat. No. 4,370,405 may help prevent the problems associated with reflectivity. However, such methods require complex processes and are not only difficult to control the processes but also expensive and therefore not preferred. Single layer resist (SLR) processes dominate semiconductor manufacturing because of their simplicity and cost-effectiveness.
The use of either top or bottom anti-reflective coatings in photolithography is a much simpler and effective approach to diminish the problems that arise from thin film interference, corresponding to either a decrease of R
1
or R
2
and thereby reducing the swing ratio S.
The most effective means to eliminate the thin film interference is to reduce the through the use of so-called bottom anti-reflective coatings (BARC). These coatings have the property of absorbing the light which passes through the photoresist and not reflecting it back. The bottom anti-reflective coating composition is applied as a thin film on the substrate prior to coating with the photoresist composition. The resist is then applied on the bottom anti-reflective coating, exposed and developed. The anti-reflective coating in the resist removed areas is then etched, for example in an oxygen plasma, and the resist pattern is thus transferred to the substrate allowing for further processing steps for forming active elements, interconnecting structures etc. The etch rate of the anti-reflective coating composition is of major importance and should be relatively higher than that of the photoresist, so that it is etched without significant loss of the photoresist film during the etch process.
Bottom anti-reflective coatings are typically divided into two types, namely inorganic and organic bottom anti-reflective coating types.
Inorganic types include stacks of dielectric
Kang Wen-Bing
Kimura Ken
Nishiwaki Yoshinori
Padmanaban Munirathna
Pawlowski Georg
Clariant Finance (BVI) Limited
Jain Sangya
Powell William
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