JPH04171816A - Semiconductor device and manufacture thereof - Google Patents

Abstract

PURPOSE:To reduce the area occupied by a shallow contact hole by forming at least a deep contact having a tapered shape and the shallow contact hole having no tapered shape in an opening formed on an insulating film on a semiconductor substrate. CONSTITUTION:After a LOCOS separating layer 12 and polycrystalline silicon wiring layer 13 are formed on a semiconductor substrate 11 and an interlayer insulating film 14 is deposited on the substrate 11, a photoresist 15 is patterned. During the course of the patterning process, a remaining part 17 of the photoresist is intentionally formed in a shallow contact hole forming section 16. Because of the photoresist 17, no wet etching takes place in the section 16 when the wet etching is performed in the next process. After the wet etching, a shallow contact hole 19 is formed by removing the photoresist 17 in the section 16 and the insulating film 14 by dry etching. In a deep contact hole forming section 18, a deep contact hole 20 is formed. Finally, a metallic wiring material 21 is deposited and metallic wiring is patterned.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a semiconductor device having fine contact holes and a method for manufacturing the same.

Conventional technology Semiconductor devices are evolving endlessly to become highly integrated and multi-functional. In particular, the progress of ultra-fine semiconductor manufacturing technology in the field of MOS memory is remarkable. Generally, in a device using multilayer polycrystalline silicon wiring, the glabellar insulating film between each wiring has many layers, resulting in a considerable thickness of the glabellar insulating film.

If a contact hole is opened in this glabella insulating film and a contact is formed from the top layer metal wiring to the bottom silicon substrate, the contact hole will be quite deep, and the metal wiring material will be sufficiently filled in the contact hole. The metal wiring is not deposited, and the metal wiring is likely to be disconnected within the contact hole. In order to avoid this, as shown in FIG. 2, a taper etching technique is used in which only the opening of the contact hole is enlarged so that metal wiring material is sufficiently deposited within the contact hole. That is, in FIG. 2, 1 is a silicon substrate, 2 is a LOGO3 separation layer, 3 is a polycrystalline silicon wiring layer, 4 is an insulating film between the eyebrows, 5 is a photoresist pattern, 6 is a shallow contact hole,
7 is a deep contact hole. For etching the tapered portion of the contact hole 6.7, isotropic etching is performed, and after forming a sufficient taper at the contact hole opening, anisotropic etching is performed to form the contact hole 6.7 with a tapered shape. form. Further, a wet etching technique using chemicals is generally used for the above-mentioned isotropic etching, and a dry etching technique is used for the above-mentioned anisotropic etching.

Problems to be Solved by the Invention In such conventional contact hole forming methods, there is a large difference between shallow and deep contact holes in fine wiring pattern devices, and it is difficult to improve step coverage in the contact hole portion of the metal wiring material. In order to improve etching, it is necessary to form a larger taper for deeper contact holes.If wet etching is performed to create a sufficient taper shape for deep contact holes, this wet etching will cause side etching to occur in shallow contact holes. There was a problem in that the area occupied by the wide and shallow contact hole 6 became too large.

The present invention has been made to solve the above problems, and an object of the present invention is to provide a semiconductor device in which the area occupied by a shallow contact hole is reduced, and a method for manufacturing the same.

Means for Solving the Problems In order to achieve the above object, the present invention provides a deep contact hole having a tapered shape in an opening formed in an insulating film on a semiconductor substrate and a deep contact hole having a non-tapered shape. Due to the structure having a small number of shallow contact holes.

Effects of the present invention With the above structure, the photoresist at the bottom remains in the shallow contact hole portion, so wet etching does not proceed during taper etching and no taper is formed, and in the deep contact hole, the photoresist remains as usual. A taper is formed, and in the dry etching process in the next process, the remaining photoresist film is etched off in the shallow contact hole portion, and then the contact hole etching progresses, and the deep contact hole is etched as normal. An ideal taper shape can be obtained in a deep contact hole, and a contact hole with a small occupied area can be obtained with almost no taper shape in a shallow contact hole.

Embodiment An embodiment of the present invention will be described with reference to the drawings. FIGS. 1(a) to 1(d) show cross-sectional views of steps in the method of forming a contact hole of the present invention.

First, as in the conventional example, as shown in FIG. 1(a), a LOCO8 isolation layer 12 and a polycrystalline silicon wiring layer 13 are formed on a semiconductor substrate 11, and an interlayer insulating film 14 is deposited. The photoresist 15 is patterned. At this time, a photoresist residue 17 is intentionally generated in the shallow contact hole forming portion 16. This phenomenon generally occurs when the pattern size is reduced (which results in underexposure, and 7 photoresists remain in the underexposed area at the bottom. Note that 18 is a deep contact hole formation area).

Next, as shown in FIG. 1(b), wet etching is performed using buffered hydrofluoric acid. In the shallow contact hole formation portion 16, the remaining photoresist 17 remains even after development, so that wet etching with hydrofluoric acid has not progressed. Further, as shown in FIG. 1(e), dry etching is performed using a fluorocarbon gas to open a contact hole. - In general, dry etching has a much lower selectivity to photoresist than wet etching, so after etching off the remaining photoresist 17 existing in the shallow contact hole forming portion 16, the insulating film 14 is etched off.
A shallow contact hole 19 is completed by etching off. Further, dry etching proceeds as usual in the deep contact hole forming portion 18, and a deep contact hole 20 is formed. Finally, as shown in FIG. 1(d), a metal wiring material 21 is deposited and the metal wiring is patterned.

Effects of the Invention As is clear from the above embodiments, according to the present invention, a deep contact hole having a tapered shape and a deep contact hole having a non-tapered shape are formed in an opening formed in an insulating film on a semiconductor substrate. Since the structure has at least a shallow contact hole, a tapered shape is rarely created, and there is no side etching, and a shallow contact hole that occupies a small area and a deep contact with a tapered opening are formed. It is possible to provide an ultrafine semiconductor device having holes and a method for manufacturing the same.

[Brief explanation of drawings]

FIGS. 1A to 1C are cross-sectional views of steps in a method of manufacturing a semiconductor device according to an embodiment of the present invention, and FIG. 2 is a cross-sectional view of a conventional semiconductor device. 11... Semiconductor substrate, 14... Interlayer insulating film (insulating film), 19... Shallow contact hole, 20... Deep depth contact hole. Name of agent: Patent attorney Haruaki Ogata and two others Konguk FJ
1-Le Figure 1

Claims (2)

[Claims] (1) A semiconductor characterized by having at least a deep contact hole with a tapered shape and a shallow contact hole without a tapered shape in an opening formed in an insulating film on a semiconductor substrate. Device. (2) A method for manufacturing a semiconductor device including a step of forming a photoresist pattern on an insulating film on a semiconductor substrate, performing wet etching and then dry etching to form a contact hole. A method for manufacturing a semiconductor device, which includes at least the step of forming a contact hole by reducing the dimensions of a photoresist pattern so that the bottom of a photoresist film in a shallow contact hole formation portion is underexposed and the photoresist at the bottom remains even after development. .