Organic anti-reflective coating polymer, anti-reflective...

Details Organic anti-reflective coating polymer, anti-reflective... Organic anti-reflective coating polymer, anti-reflective...

2001-06-25

2003-05-13

Nakarani, D. S. (Department: 1773)

Synthetic resins or natural rubbers -- part of the class 520 ser

Synthetic resins

Polymers from only ethylenic monomers or processes of...

C427S096400, C427S384000, C428S209000, C428S411100, C428S451000, C428S901000, C526S319000

Reexamination Certificate

active

06562925

ABSTRACT:

BACKGROUND
1. Technical Field
An organic anti-reflective polymer and its preparation method are disclosed. The organic anti-reflective polymer prevents back reflection of lower film layers and eliminates a standing wave that occurs as a result of thickness changes of the photoresist and light, in a lithographic process using 248 nm KrF and 193 nm ArF laser light sources for fabricating ultrafine patterns. More particularly, the organic anti-reflective polymer is useful for fabricating ultrafine patterns of 64 M, 256 M, 1 G, and 4 G DRAM semiconductor devices. A composition containing such organic anti-reflective polymer, an anti-reflective coating layer made therefrom and a method of preparation are also disclosed thereof.
2. Description of the Background Art
In a fabrication process of ultrafine patterns for preparing semiconductor devices, standing waves and reflective notching inevitably occur due to the optical properties of lower film layer on the wafer and due to a thickness variation in the photosensitive film. In addition, there is another problem of the CD (critical dimension) alteration caused by diffracted and reflected light from the lower film layers. Thus, it has been suggested to introduce anti-reflective coating that enables preventing back reflection at a lower film layer by introducing organic material showing high absorbance at a wavelength range of the light employed as a light source.
Anti-reflective coating is classified into inorganic and organic anti-reflective coating depending upon the material used, or into absorptive and interfering anti-reflective coating based on the operation mechanism. For microlithography using I-line (365 nm wavelength) radiation, inorganic anti-reflective coating is predominantly used, while TiN and amorphous carbon as an absorptive system and SiON as an interfering system are employed.
In a fabrication process of ultrafine patterns using KrF laser, SiON has been mainly used as an inorganic anti-reflective film. However, in the case of an inorganic anti-reflective film, no material has been known which enables the control of the interference at 193 nm, the wavelength of light source. Thus, there has been great deal of efforts to employ an organic compound as an anti-reflective coating.
To be a good organic anti-reflective coating, the following conditions must be satisfied. First, peeling of the photoresist layer due to the dissolution in a solvent must not take place when conducting a lithographic process. In order to achieve this goal, a molded coating must be designed to form a cross-linked structure without producing any chemical as a by-product. Second, chemicals such as acid or amine must not migrate into or out from the anti-reflective coating. This is because when acid migrates from anti-reflective coating, undercutting occurs at a lower part of the pattern while footing may occur when a base such as amine migrates. Third, the etching speed of the anti-reflective coating should be faster than that of the upper photosensitive film so as to facilitate etching process by using photosensitive film as a mask. Finally, the anti-reflective coating must be as thin as possible to an extent to sufficiently play a role as an anti-reflective coating.
The existing organic anti-reflective material is mainly divided into two types: (1) polymers containing chromophore, cross-linking agent (single molecule) cross-linking the polymers and an additive (thermally variable oxidant); and (2) polymers which can cross link by themselves and contain chromophore and an additive (thermally variable oxidant). But these two types of anti-reflective material have a problem in that the control of k value is almost impossible because the content of the chromophore is defined according to the ratio as originally designed at the time of polymerization. Thus, if it is desired to change the k value, the polymer must be synthesized again.
SUMMARY OF THE DISCLOSURE
A novel organic polymer for anti-reflective coating and its preparation are disclosed method.
An anti-reflective coating composition comprising the aforementioned polymer and a preparation method thereof are also disclosed
A semiconductor device on which a pattern is formed from such an anti-reflective coating by submicrolithography is also disclosed.
DETAILED DESCRIPTION OF THE PRESENTLY PREFERRED EMBODIMENTS
The following polymer compounds having Formulas 1 and 2, respectively are provided which can be used in an anti-reflective coating.
In the above Formulas 1 and 2:
R, R′, and R″ are each independently hydrogen or methyl; R
a
to R
d
, and R
1
to R
18
are each independently —H, —OH, —OCOCH
3
, —COOH, —CH
2
OH, or substituted or unsubstituted, or straight or branched alkyl or alkoxy alkyl having 1 to 5 carbon atoms; m and n each represents an integer selected from 1, 2, 3, 4 and 5; x, y, and z each represents mole fraction from 0.01 to 0.99; R
19
and R
20
are each independently straight or branched substituted C
1-10
alkoxy; and R
21
is hydrogen or methyl.
The compound of Formula 2 is prepared by polymerizing (meth)acrolein to obtain poly(meth)acrolein followed by reacting the obtained polymeric product with branched or straight substituted alkyl alcohol having 1 to 10 carbon atoms.
In detail, (meth)acrolein is first dissolved in an organic solvent and added thereto a polymerization initiator to carry out polymerization under vacuum at a temperature ranging from about 60 to about 70° C. for a time period from about 4 to about 6 hours. Then, the obtained polymeric product is reacted with branched or straight substituted alkyl alcohol having 1 to 10 carbon atoms in the presence of trifluoromethylsulfonic acid as a catalyst at a room temperature for a time period ranging from about 20 to about 30 hours.
In the above process, suitable organic solvent is selected from the group consisting of tetrahydrofuran (THF), cyclohexanone, dimethylformamide, dimethylsulfoxide, dioxane, methylethylketone, benzene, toluene, xylene and mixtures thereof. As a polymerization initiator, it can be mentioned 2,2-azobisisobutyronitrile (AIBN), benzoylperoxide, acetylperoxide, laurylperoxide, t-butylperacetate, t-butylhydroperoxide or di-t-butylperoxide. A preferred example of the said alkyl alcohol having 1 to 10 carbon atoms is ethanol or methanol.
A preferred compound of Formula 2 is selected from the group consisting of the compounds of the following Formulas 3 to 6.
The above compounds of Formulas 3 to 6 are readily cured in the presence of acid and other polymers having alcohol group.
The polymer of Formula 1 is prepared by reacting 9-anthracene methyliminealkylacrylate monomer, hydroxyalkylacrylate monomer, glycidylalkylacrylate monomer and 9-anthracenealkylmethacrylate monomer in an organic solvent and then polymerizing the obtained compound with a polymerization initiator. Any conventional organic solvent can be used in this process but a preferred solvent is selected from the group consisting of tetrahydrofuran, toluene, benzene, methylethylketone, dioxane and mixtures thereof. As a polymerization initiator, any conventional radical polymerization initiator can be used but it is preferred to use a compound selected from the group consisting of 2,2′-azobisisobutyronitrile, acetylperoxide, laurylperoxide, and t-butylperoxide. The above polymerization reaction is preferably carried out at a temperature ranging from about 50 to about 90° C. and each of the monomers has a mole fraction ranging from about 0.01 to about 0.99.
An effective anti-reflective coating composition can comprise a polymer of Formula 1 and a polymer of Formula 2.
Further, an effective anti-reflective coating composition can comprise a polymer of Formula 1, a compound of Formula 2 and an anthracene derivative as an additive. Illustrative, non-limiting examples of the anthracene derivatives (hereinafter, “anthracene derivative additive”) is selected from the group consisting of anthracene, 9-anthracenemethanol, 9-anthracenecarbonitrile, 9-anthracene carboxylic acid, dithranol, 1,2,10-anthracentriol, anthraflavonic a

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