Semiconductor device manufacturing: process – Chemical etching – Vapor phase etching
Reexamination Certificate
1999-04-29
2001-06-19
Powell, William (Department: 1765)
Semiconductor device manufacturing: process
Chemical etching
Vapor phase etching
C438S725000, C438S736000, C438S738000
Reexamination Certificate
active
06248669
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates generally to a method of manufacturing semiconductor devices, and more particularly to a method of manufacturing semiconductor devices which includes a patterning process using chemically amplified photo resist.
BACKGROUND OF THE INVENTION
As semiconductor devices such as large-scale integrated circuit (LSI) devices and the like are highly integrated, it becomes necessary in these LSI devices to form finer inner conductors, electrodes and the like. For example, in case of a Dynamic Random Access Memory (DRAM), 64 Megabit DRAM uses 0.35 micrometer (micron) rule, and 256 Megabit DRAM of the next generation uses 0.25 micrometer rule. In order to deal with such needs of miniaturization, exposure light source having shorter wavelength is required in the field of lithography for forming LSI patterns. Therefore, recently, in place of a conventional mercury lamp having high energy level emission line spectrum of g-line (436 nm), i-line (365 nm) and the like, excimer lasers of KrF (248 nm), ArF (193 nm) and the like have been introduced.
When such excimer lasers are used, it is impossible to use conventional resist for i-line exposure because of low transmittance. Therefore, new material such as polyhydroxystyrene (PHS) is developed. Also, because of low illuminance of the excimer lasers, chemically amplified photo resist is developed which can realize the photo resist having high sensitivity. In the chemically amplified photo resist, when it is exposed to the light, proton acid (H+) is generated from photo acid generator in the photo resist. In case the chemically amplified photo resist is a positive type, the acid diffuses into the photo resist when the resist is heated after the exposure to the light and renders resist resin in exposed portions soluble in developer, thereby enabling patterns to be formed. In case the chemically amplified photo resist is a negative type, the acid acts as a catalyst for crosslinking reaction and renders exposed portions of the resist insoluble in developer to enable pattern formation.
On the other hand, as a material of electrical wirings and electrodes, metallic materials such as aluminum (Al) and the like having high reflectance are mainly used. However, when the photo resist is applied directly on such materials, there occurs a problem that formed patterns deform due to light reflection from the metallic materials. Therefore, in general, anti-reflection process was done by forming a film of titanium nitride and the like on the metallic materials. Also, when LOCOS oxidation is to be performed to form isolation regions between elements, it is necessary to deposit silicon nitride film or silicon oxynitride film only on regions not to be oxidized. To this end, the silicon nitride film or the silicon oxynitride film was formed on whole surface of a substrate, and, on such silicon nitride film or silicon oxynitride film, the photo resist was directly applied and exposed. However, lone pairs (lone electron pairs) exist in such materials having nitrogen atoms. Therefore, when the chemically amplified photo resist is applied on such materials and exposed by using the excimer laser of KrF and the like, the proton acid generated is captured or trapped by the lone electron pairs and acid deactivation occurs, thus it becomes impossible to form desired patterns appropriately. That is, when the positive type resist is used, so called “skirt trailing” phenomenon is generated wherein width of the bottom portion of an opening becomes narrower than that of the top portion, or regions which are to become openings are not completely penetrated and resist patterns are not separated and resolved. On the contrary, when the negative type photo resist is used, encroaching or ingrowing phenomenon occurs in which the section of the bottom portion of the opening becomes larger at the interface with grounding plane than other portion of the opening.
In order to solve these problems in using the chemically amplified photo resist, Japanese patent application No. 6-217555, filed on Sep. 12, 1994 in Japan (Japanese patent laid-open publication No. 8-83786, published on Mar. 26, 1996) discloses a pattern forming method, in which, after forming a silicon oxide layer or a silicon oxynitride layer on a silicon nitride layer, chemically amplified resist is applied, and then exposed and developed. In this publication, a method of oxidizing the surface of the silicon nitride layer, by using oxygen plasma, is also disclosed to form the silicon oxide layer or the silicon oxynitride layer on the surface of the silicon nitride layer. Also, a method is known in which wet processing is performed on the silicon nitride layer by using acid solution. However, in these method, since a new layer is stacked by using separate process or by using separate apparatus, or wet process or another apparatus is further required, there is a possibility that manufacturing process becomes complicated and throughput is deteriorated.
On the other hand, in Japanese patent application No. 8-64360 filed on Mar. 21, 1996 in Japan (Japanese patent laid-open publication No. 9-260246, published on Oct. 3, 1997) a technique is disclosed wherein by using a film forming apparatus in which a film forming chamber and an ashing chamber are adjacently disposed, ashing is performed continuously after forming a nitride film to form a chemically amplified resist film on the nitride film whose quality at the surface is improved or modified. In this publication, it is disclosed that by using this technique lone pairs at the surface of the nitride film can be vanished or decreased, thereby the phenomenon in which the proton acid generated at the exposure is consumed by the lone pairs can be avoided.
In usual manufacturing process, process of resist application and exposure is not always conducted soon after the formation of nitride film, but often conducted one through several days after the formation, for reasons of processing semiconductor wafers by the manufacturing lot. If the wafers are stored or left for a long time before exposure process, effect of surface modification will be deteriorated, even if the quality of the surface of the nitride film is modified as described in the above-mentioned Japanese patent laid-open publication No. 9-260246 and the like. Also, if resist patterns once formed do not satisfy the permissible precision limits of pattern size or pattern location, it is necessary to perform reconstruction wherein the resist is stripped off and another resist is again applied to the wafer, and then exposure and developing are performed. However, when the resist is stripped off, the effect of quality improvement by the plasma is damaged, and the effect is further deteriorated due to the long time storage as mentioned above.
Therefore, it is an object of the present invention to provide a method of manufacturing a semiconductor device in which, when patterns are formed by using the chemically amplified photo resist formed on a layer which is etched and which includes nitrogen atoms, photo resist patterns having superior sectional profile can be fabricated.
It is another object of the present invention to provide a method of manufacturing a semiconductor device in which, when patterns are formed by using the chemically amplified photo resist formed on a layer which is etched and which includes nitrogen atoms, skirt trailing phenomenon or encroaching phenomenon of the chemically amplified photo resist in a lithography process can be avoided.
It is another object of the present invention to provide a method of manufacturing a semiconductor device in which, when patterns are formed by using the chemically amplified photo resist formed on a layer which is etched and which includes nitrogen atoms, skirt trailing phenomenon or encroaching phenomenon of the chemically amplified photo resist in a lithography process can be avoided without complicating a manufacturing process and without deteriorating throughput.
It is still another object of the present invention to pr
Ichikawa Toshihiko
Ogawa Hiroshi
Hayes Soloway Hennessey Grossman & Hage PC
NEC Corporation
Powell William
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