JPH051611B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a pattern forming method, particularly a pattern forming method using a radiation-sensitive resin.

BACKGROUND TECHNOLOGY High integration and high density of integrated circuits have increased due to advances in microfabrication technology. The minimum processing line width has also become approximately 1 μm, and one way to achieve this is to expose the photosensitive film to ultraviolet light using a reduction projection method using a high aperture lens. However, if the photosensitive film is thick, it is impossible to form a good pattern.

Two or three layers can be used to solve this problem.
Various multilayer resist techniques with layered structures have been proposed. A typical method for creating a two-layer structure is the combination of PMMA copolymer/PMMA for electron beam exposure (for example, M. Hatsutsakis, Journal of Vacuum Science and Technology, Vol. 16, p. 1984 (1979) (M. Hatzakis, J.
Vac.Sci.Technol., vol.16, P.1984 (1979)), anti-reflective coating ARC (e.g., Y.C.Lin et al., Vacuum Science and Technology Journal, p.1215 (1983)) (YCLin et al.
ol, J.Voc.Sci.Technol, P.1215 (1983)). On the other hand, the three-layer structure has an inorganic layer as an intermediate layer on a flattened lower film (for example, J.M. Moran et al., Journal of Vacuum Science and Technology, Vol. 16, p. 1620 (1979) (J.M. Moran et al., J. Voc. .Sci.
Technol.vol.16P.1620 (1979)), plasma SiO ₂ films that can be formed at low temperatures (e.g. B. Sielinski et al., IBM Technical Disclosure Bulletin, Vol. 19, p. 1214 (1979))
(B. Zielinski et ol, IBM Technical
Disclosure Bulletin, vol.19, P.1214 (1979))
or spin-coatable SOG films (e.g. G.I.
R. Havas, Journal of the Electrochemical Society, Extensive Abstract Collection,
76-2 p. 743 (1976) (JRHavas, J.
Electrochem.Soc.Extended Abstract, 76-2
P.743 (1976))), the intermediate layer is etched with the patterned resist on the top layer, and then a pattern is formed on the intermediate layer using an etch mask and the lower film using RIE etc. There is.

Problems to be Solved by the Invention As mentioned above, a wide variety of multilayer resist methods have been reported, and while each has its advantages, it also has the disadvantages of increasing costs, reducing throughput, and complicating the process. ing.

Furthermore, it is well known that the single-layer resist method has the drawback that as the film thickness increases, the resolution decreases and a vertical cross-sectional shape cannot be obtained.

Means for Solving the Problems The present invention aims to solve the problems as described above.
In a two-layer resist structure, the lower resist is exposed to light without completely losing its photosensitivity, that is, to the extent that it is difficult to dissolve in a developer, and then an upper resist of the same material is formed and selectively exposed in an arbitrary shape. - It provides a method of forming a pattern by exposure to light and then a series of wet development methods.

Function The present invention provides a form in which the photoresist reaction of the lower layer resist is enhanced after selective exposure in an arbitrary shape after forming the upper layer resist by exposing the lower layer resist in advance to a range in which it is difficult to dissolve in a developer. Therefore, a fine pattern with good perpendicularity can be formed even in a thick film by a series of wet developments.

Embodiment An embodiment of the present invention will be described with reference to FIG.
A positive photosensitive resin (hereinafter referred to as resist) 2 is applied as a first layer of radiation-sensitive resin on the substrate 1,
Apply soft baking (Figure 1a). Next, the entire surface of the first layer resist 2 is irradiated with light 3 to form a photosensitive resist 2-a. In this case, the concentration of sensitive groups in the resist 2-a decreases from the value _M0 before exposure to _M1 due to the photosensitive reaction (FIG. 1b).

Next, an altered layer is formed on the surface of the resist 2-a by fluorine-based gas plasma 4 to such an extent that no change occurs in the photosensitive reaction on the surface of the resist 2-a (FIG. 1c). Next, a resist made of the same material as the first layer resist 2 is coated on the first layer resist, and a second layer resist 2 is coated on top of the first layer resist 2.
This is the resist layer 5. At this time, due to the previous surface treatment, the first and second layer resists 2-a
and 5 can be laminated separately without mixing (Fig. 1d).

Next, using a mask 6 having a pattern, the second layer resist 5 and the first layer resist 2-a are selectively irradiated with light 8 other than the chromium portion 7 at the same time. At this time, the light irradiation part 5- of the second layer resist is
The concentration of sensitive groups in a varies from M ₀ to M ₂ on average. Further, the concentration of the sensitive group in the light irradiated portion 2-b of the first resist layer changes from M ₁ to M ₃ on average. Here, it is assumed that M ₃ <M ₂ <M ₁ <M ₀ (Fig. 1e).

Next, using a developer that is difficult to dissolve the resist when the concentration of sensitive groups in the resist is _M1 or more, but is easy to dissolve when the concentration of sensitive groups in the resist is _M2 or less, the light irradiated areas 2-b and 5-a are
Develop and remove.

Through these series of steps, it is possible to form a pattern having a resist cross-sectional shape with good verticality even though the resist is applied thickly (FIG. 1f). Note that, in addition to light, radiation energy such as an electron beam may also be used for exposure.

Next, a specific example based on the embodiment will be explained using FIG. 1. A first layer of resist 2 is applied to a thickness of 1.0 μm and soft baked at 90° C. for 5 minutes.
Next, the ultraviolet rays in the ultraviolet range (3000 to 5000 Å) generated by a Hg lamp are applied at 10 mJ/cm ^2, which is about 1/20 of the exposure dose that causes a complete reaction.
The concentration of sensitive groups is reduced to 80% of its pre-irradiation level by irradiation with an exposure energy of about 100%. In this case, the photosensitivity of the first layer resist remains. and
Plasma is generated using CF ₄ gas, and surface treatment is performed using fluorine radicals.

Next, a second layer of resist 5, which is the same type as the first layer of resist, is placed on top of the first layer of resist.
Apply 1.0μm thick. The total film thickness at this time is approximately 2.0μ
It becomes m.

Next, the first and second resist layers are irradiated with a single wavelength of 4365 Å at 200 mJ/cm ² for a second time using a reduction projection exposure method through a reticle 6 having a fine pattern 7 . Finally, the photosensitive resist is developed with an alkaline developer. FIG. 2 shows the dissolution rate R of the developing solution used in this case relative to the concentration M of sensitive groups in the resist. As shown in the figure, the dissolution rate of the resist used is one in which the concentration of the sensitive group changes significantly between 60% and 80%.

Effects of the Invention As described above, according to the present invention, a vertical and fine pattern can be formed on a radiation-sensitive resin film even in a thick film. The present invention will exhibit effective value for future microfabrication technology.

[Brief explanation of the drawing]

1A to 1F are cross-sectional views of a pattern forming process according to an embodiment of the present invention, and FIG. 2 is a diagram showing a resist dissolution rate. 1...Substrate, 2, 2a...1st layer resist,
3...Light, 5...Second layer resist.

Claims (1)

[Claims] 1. Applying a first radiation-sensitive resin onto a substrate, performing a first radiation irradiation, and applying a first radiation-sensitive resin onto the substrate.
a step of subjecting the radiation-sensitive resin film to a radiation reaction to reduce the concentration M of radiation-reactive groups to _M1 ;
A second radiation-sensitive resin is coated on the radiation-reacted first radiation-sensitive resin, and a second radiation-sensitive resin is selectively irradiated to reduce the concentration of radiation-reactive groups in the first radiation-sensitive resin. and developing with a developer capable of selectively developing a portion of the first radiation-sensitive resin with a radiation-reactive group concentration M ₁ and a portion with a radiation _- reactive group concentration M ₃ ; 1st
and a step of selectively removing the second radiation-sensitive resin film to form a radiation-sensitive resin pattern.