JP2666420B2 - Method for manufacturing semiconductor device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Overview] Regarding a pattern forming method by a multi-layer lithography method, an object of the present invention is to shorten a processing step in a multilayer resist method, eliminate the need for proximity effect correction, and form a highly accurate pattern. An organic resin film capable of oxygen ion etching is applied as a lower layer on the film to be etched and solidified, and an oxygen ion etching is possible as an intermediate layer, a photosensitive resist film having a good contrast, containing silicon as an upper layer, and A photosensitive resist film having a lower contrast than the photosensitive resist film of the intermediate layer is successively formed, and then the upper layer and the intermediate layer are simultaneously exposed and developed, and the upper layer and the intermediate layer are masked and the lower layer is exposed to oxygen ions. And a step of patterning by etching.

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a semiconductor device, and more particularly, to a pattern forming method using a multi-layer lithography method.

In highly integrated ICs such as LSIs, the unevenness of the surface becomes severe due to multilayer wiring and the like, and there is a step, and it is difficult to form a fine pattern on the step. A method of patterning by a linography method is important.

However, it is desired that the pattern formation by such a multi-layer lithography method is simple, and that a highly accurate pattern can be obtained.

[Prior Art] Conventionally, when a resist film pattern is formed on a stepped portion, the thickness of the resist film (photosensitive resin film) is different between the concave portion and the convex portion, and when this is exposed and developed, the pattern of the concave portion and the convex portion is obtained. There was a problem that patterning could not be performed with high precision, such as different widths. That is, if both are exposed at the same time, the thick resist film portion on the concave portion becomes insufficiently exposed, and if this is developed, the width of the resist film pattern becomes narrower and the resist film portion on the convex portion becomes thinner. Is excessively exposed, and if developed, the width of the resist film pattern is increased. 4 (a) and 4 (b) are a plan view and a sectional view showing the same, showing the negative resist film 2 formed on the film 1 to be etched having a step. To be precise, the pattern width is not constant because of the relationship between the exposure wavelength and the resist film thickness. However, conceptually, the width of the resist film pattern changes in proportion to the film thickness.

Therefore, a patterning method for forming a plurality of types of resist film patterns on portions having steps has been developed, and a method for forming a pattern of a three-layer resist film is called a three-layer resist method (trilevel method). In other words, a method of forming a pattern of a two-layer resist film is called a two-layer resist method (bilevel method).

5 (a) to 5 (g) are cross-sectional views in the order of steps of a conventional pattern forming method using a three-layer resist method.

Referring to FIG. 5A, first, a lower layer 3 is formed on the film 1 to be etched.
Is thickened until flattened, baked and solidified. The lower layer 3 is a non-photosensitive organic resin film, but may be used by baking the whole surface of a negative resist film after exposure.

Next, an intermediate layer 4 is applied and solidified thereon, as shown in FIG. 5 (b). The intermediate layer 4 is a film containing silicon, for example, using an SOG (spin-on-glass) film, and baking for solidification is performed at 150 ° C., 200 ° C., and 275 ° C. in steps.

After the surface treatment of the intermediate layer, the upper layer 5 is applied thereon and solidified. The upper layer is a photosensitive resist film (negative type), which is baked at a temperature of 100 ° C. for solidification. The above surface treatment is for improving the adhesion of the upper layer.

5 (d); after that, the upper layer 5 is exposed by an electron beam (EB) exposure method. In addition, at the time of this EB exposure, exposure is performed using data subjected to proximity effect correction processing. The upper layer 5 is far away from the film 1 to be etched, so that the influence of the proximity effect is reduced, but the effect is not eliminated. Therefore, the proximity data needs to be corrected for the exposure data.

Next, as shown in FIG. 5 (e), the exposed upper layer 5 is developed to form an upper layer 5 pattern.

Then, referring to FIG. 5 (f), the intermediate layer 4 is dry-etched and patterned using the upper layer 5 pattern as a mask.

Next, referring to FIG. 5 (g); using the pattern of the intermediate layer 4 as a mask, the lower layer 3 is ion-etched with oxygen gas,
Thus, a three-layer pattern is formed. In this three-layer resist method, the lower layer 3 pattern is formed with high accuracy because the intermediate layer 4 pattern has good oxygen dry etching resistance. FIG. 5 (g) shows the upper 5 patterns, which disappear when the lower 3 patterns are formed.

Next, FIGS. 6 (a) to 6 (e) are sectional views in the order of steps of a pattern forming method by a conventional two-layer resist method.

Referring to FIG. 6A, first, a lower layer 3 is formed on the film 1 to be etched.
Is thickened until flattened, baked and solidified. The lower layer 3 uses a non-photosensitive organic resin film as in the case of the three-layer resist method.

See FIG. 6 (b); then, the upper layer 6 is applied thereon and solidified. The upper layer 6 is a photosensitive resist film containing silicon, for example, a recently developed PMSS (silylated polymethylsilsesquioxane; negative type).

Next, the upper layer 6 is exposed by the EB exposure method, as shown in FIG. 6 (c). Note that this EB exposure processing requires correction of the proximity effect.

Next, as shown in FIG. 6 (d), the exposed upper layer 6 is developed to form an upper layer 6 pattern.

Next, referring to FIG. 6 (e); using the upper layer 6 pattern as a mask, the lower layer 3 is ion-etched with oxygen gas,
A lower three-layer pattern is formed.

[Problems to be Solved by the Invention] The three-layer resist method described above has a drawback that the processing steps are complicated and the processing time is long. In particular, EB exposure is a direct drawing method, and it is necessary to perform proximity effect correction on exposure data. There is a problem that data processing takes an enormous amount of time.

The two-layer resist method requires a shorter processing step than the three-layer resist method because a photosensitive resist film containing silicon is used for the upper layer 6, but the two-layer resist method has a low contrast and a proximity effect. Correction is required in the same manner, and there is a disadvantage that a residue (inorganic substance or the like) of the upper layer 6 remains on the film to be etched. This residue remains on the lower layer 3 without being scattered when the upper layer 6 of the silicon-containing film is developed,
When the lower layer 3 is patterned, the lower layer 3 is strongly hit with ions, so that the residue does not scatter but remains as it is and adheres to the film to be etched.

An object of the present invention is to shorten the processing steps in such a multilayer resist method, eliminate the need for proximity effect correction, and to form a highly accurate pattern using a photosensitive resist film containing silicon. The proposed manufacturing method is proposed.

[Means for Solving the Problem] The problem is to form an organic resin film capable of being subjected to oxygen ion etching as a lower layer 13 on a film to be etched 11 as shown in the principle diagrams shown in FIGS. 1 (a) to 1 (f). It is applied and solidified (FIG. (A)), and then a photosensitive resist film (FIG. (B)) which can be subjected to oxygen ion etching and has good contrast as the intermediate layer, and contains silicon as the upper layer 15 and Subsequently, a photosensitive resist film having lower contrast than the photosensitive resist film of the intermediate layer (FIG. 10C) is formed, and then the upper layer is formed.
15 and the intermediate layer 14 are simultaneously exposed and developed (FIG.
(E)) and using the upper layer and the intermediate layer as masks,
The problem is solved by a manufacturing method including a step of etching (13) (13) the pattern 13 by etching it with oxygen ions. This principle diagram is an example in which a negative type is used as a photosensitive resist film.

[Operation] That is, in the present invention, the upper layer 15 made of a photosensitive resist film containing silicon and the intermediate layer 14 made of a photosensitive resist film having good contrast are simultaneously exposed and developed. Then, the upper layer 15 is affected only by the forward scattering of the proximity effect (the conventional upper layer 5 is affected by the back scattering due to the SOG film of the intermediate layer). The effect is reduced if the thickness is reduced. Further, since the intermediate layer 14 is a resist film having a good contrast, the upper portion is patterned with high accuracy, and the lower portion is broadened under the influence of the backscattering of the proximity effect (FIG. 3B). reference). On the other hand, the upper layer 15 has poor contrast,
And a high-precision pattern is formed. As described above, the upper layer 15 is less affected by forward scattering and is not affected by back scattering, and is regulated by the intermediate layer to form a high-precision pattern. Therefore, when patterning is performed by oxygen ion etching using the upper layer pattern as a mask, the intermediate layer and the lower layer are formed with high precision, and the need for proximity effect correction is eliminated. Therefore, according to the pattern forming method of the present invention, a highly accurate pattern can be formed by a shortened pattern forming step.

[Example] Hereinafter, an example will be described in detail with reference to the drawings.

2 (a) to 2 (d) are cross-sectional views in the order of steps of a pattern forming method according to the present invention.

Referring to FIG. 2 (a), CMS (chloromethylated polystyrene) having a thickness of 1 to 2 μm is applied on the film 11 to be etched of the semiconductor substrate 10 as an organic resin film capable of being subjected to oxygen ion etching of the lower layer 13. CMS (Chloromethylated polystyrene) film of 3000-4000mm thickness as a photosensitive resist film with good contrast, which can be flattened and solidified, exposed to the whole surface and then insolubilized, and then oxygen ion etching of the intermediate layer 14 is possible and has a good contrast. And soft baked at 80 ° C, followed by
An upper layer 15 of a silicon-containing photosensitive resist film containing silicon having a low contrast and a thickness of 1500 to 2000 膜厚 is coated with a PMSS (silylated polymethylsilsesquioxane) film and baked at 100 ° C.

Then, the PMSS film as the upper layer 15 and the CMS film as the intermediate layer 14 are directly drawn and exposed by the EB exposure method. However, it is not necessary to apply the proximity effect correction to the exposure data.

Then, development is performed using MIBK (methyl isobutyl ketone) to form a high-precision upper layer 15 pattern and an intermediate layer 14 pattern affected by backscattering.

Next, referring to FIG. 2 (d); the upper layer 15 pattern is used as a mask to perform vertical reactive ion etching (RIE) with oxygen (O ₂ ) ions to pattern the lower layer 13 CMS film. At that time, the intermediate layer 14 is simultaneously patterned with high accuracy.

According to the above-described forming method, the processing steps are substantially the same as those of the conventional two-layer resist method, and it is not necessary to perform the proximity effect correction at the time of EB exposure, so that the pattern forming method is greatly simplified. . In addition, a high-precision pattern is formed, and residues generated from the upper layer containing silicon are lifted off in the developing step of the intermediate layer and are not removed and remain.

Next, the features and effects of the pattern forming method according to the present invention will be described with reference to FIGS. FIG. 3A shows the residual film ratio with respect to the dose (exposure) of the upper layer 15 resist and the intermediate layer 14 resist. Usually, the dose is added so that the residual film ratio is about 80 to 99% so as not to cause overexposure. However, in this figure, the intermediate layer 14 resist indicated by a broken line is better than the upper layer 15 resist indicated by a solid line. This shows that the contrast is good, and the present invention uses such a resist for the upper layer 15 and the intermediate layer 14. Although the above description has been made of the photosensitive resist film based on the quality of the contrast, the contrast is exactly a γ value. The γ value is represented by γ value = 1 / log (A / B), where A and B connect 0% and 50% of the remaining film ratio in the data curve of the remaining film ratio and the exposure amount. Draw a straight line,
The exposure amount at the intersection of this straight line and the remaining film ratio of 100% is B, and the remaining film ratio is 0.
The exposure amount at% is represented by A.

FIG. 3 (b) is an explanatory view of exposure and development, showing the backscattering (reflection from the substrate to be etched) and forward scattering (reflection in the resist) already described.

FIGS. 3 (c) and 3 (d) show an irradiation energy intensity curve according to the structure of the present invention and an irradiation energy intensity curve according to the conventional three-layer resist method, wherein the vertical axis is the reciprocal of the dose and the horizontal axis. Is a dimension value of a half width of the rectangular pattern. As shown in FIG. 3D, a pattern with high accuracy cannot be formed unless the dose is changed according to the pattern width. In the present invention, different width patterns can be formed with high precision by the same dose as shown in FIG. This indicates that the pattern forming method according to the present invention can form patterns having various mixed dimensions with high accuracy.

[Effects of the Invention] As is clear from the above description, according to the present invention, in a multi-layer lithography method using EB exposure, a high-precision pattern can be formed in a simpler forming process, and the quality of a semiconductor device such as an IC is improved. -It greatly contributes to the improvement of throughput.

BRIEF DESCRIPTION OF THE DRAWINGS FIGS. 1 (a) to 1 (f) are principle diagrams according to the present invention, and FIGS. 2 (a) to 2 (d) are cross-sectional views in the order of steps of a pattern forming method according to an embodiment of the present invention. FIGS. 3 (a) to 3 (d) are views for explaining the features and effects of the pattern forming method according to the present invention, and FIGS. 4 (a) and 4 (b) show a conventional one-layer resist film pattern. FIGS. 5 (a) to 5 (g) are step-by-step cross-sectional views of a conventional pattern forming method using a three-layer resist method, and FIGS. 6 (a) to (e) are pattern forming methods using a conventional two-layer resist method. FIG. In the figure, reference numerals 1 and 11 denote a film to be etched, 3 a lower layer, 4 an intermediate layer, 5 and 6 an upper layer, 13 a lower layer (CMS film) of the pattern forming method according to the present invention, and 14 a pattern forming method according to the present invention. An intermediate layer (CMS film) 15 of the method is an upper layer (PMSS film) of the pattern forming method according to the present invention.

Claims (1)

(57) [Claims] An organic resin film capable of being subjected to oxygen ion etching is applied as a lower layer on a film to be etched and solidified. A photosensitive resist film capable of performing oxygen ion etching and having a good contrast as an intermediate layer, and silicon as an upper layer. Containing and subsequently forming a photosensitive resist film having a lower contrast than the photosensitive resist film of the intermediate layer, then simultaneously exposing and developing the upper layer and the intermediate layer, and using the upper layer and the intermediate layer as a mask, A method for manufacturing a semiconductor device, comprising a step of etching and patterning a lower layer with oxygen ions.