JP2003152075A - Method for manufacturing semiconductor device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for manufacturing a semiconductor device wherein aluminum is stacked without closing an aperture of a small-sized contact whole when aluminum is stacked on a contact hole formed on an oxide film on a substrate, and a superior aluminum electrode can be formed. SOLUTION: A pattern is formed on an oxide film 2 stacked on a semiconductor substrate 1 by using a resist 6, and etching is performed as far as halfway to the oxide film 2 by isotropic dry etching. Etching is performed further until reaching a semiconductor substrate 1 by anisotropic etching, and a contact hole 3 is formed. Aluminum 7 is stacked in order on the contact hole 3, an aluminum electrode 4 is formed, and an overcoat film 5 is formed further on the aluminum electrode 4.

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a semiconductor device having a contact hole for forming an electrode through an oxide film on a semiconductor substrate. 2. Description of the Related Art As semiconductor devices have become more highly integrated, the size of contact holes formed on a semiconductor substrate has been reduced. The contact hole is for arranging an electrode through an oxide film formed on the semiconductor substrate. [0003] Such contact holes are generally
It is formed by wet etching or dry etching. However, it is difficult to control the size of a contact hole to be formed by wet etching.
Anisotropic dry etching is used to form a small contact hole having a cross section of about μm ² or less. FIG. 3 shows a process of manufacturing a semiconductor device by conventional anisotropic dry etching. As shown in FIG. 1A, a contact pattern is formed on an oxide film 2 formed on a semiconductor substrate 1 by using a resist 6, and FIG.
After performing anisotropic dry etching as shown in FIG. 2C, the resist 6 is removed as shown in FIG. In the anisotropic dry etching, since the etching proceeds only in one direction (downward in FIG. 3), the wall surfaces of the contact holes formed in the oxide film 2 are perpendicular to the semiconductor substrate 1. Thus, contact hole 8 is formed in oxide film 2.
After the formation, as shown in (d), (e) and (f) of FIG.
An aluminum electrode 10 is formed by laminating aluminum 9 by aluminum sputtering or aluminum evaporation, and an overcoat film 11 is formed by plasma SiN to prevent corrosion of the aluminum electrode 10. However, when aluminum 9 is laminated on contact hole 8 whose wall surface is formed vertically as described above, aluminum 9 adheres to the wall surface of this vertical contact hole. It is difficult to perform the process, and many layers are formed on the top surface of the oxide film 2 and the bottom surface of the contact hole 8.
In particular, at the periphery of the contact hole 8 on the upper surface of the oxide film 2,
As shown in FIGS. 3D to 3F, the aluminum 9 is laminated so as to overhang. When the overhang of the aluminum 9 progresses and the opening of the contact hole 8 is narrowed as shown in FIG. 1F, as shown in FIG. Is difficult to be stacked in the contact hole 8. As described above, when the overcoat film 11 is not sufficiently laminated on the aluminum electrode 10 and the film thickness is reduced, the aluminum electrode 10 may be corroded from the thin portion. In particular, such a phenomenon is very likely to occur in a contact hole which has been miniaturized due to the high integration of a semiconductor device. Therefore, according to the present invention, when laminating aluminum in a contact hole formed in an oxide film on a substrate, aluminum is laminated without closing an opening of a small contact hole to form a good aluminum electrode. It is an object of the present invention to provide a possible method for manufacturing a semiconductor device. According to a method of manufacturing a semiconductor device of the present invention, an aluminum electrode is formed in a contact hole penetrating an oxide film laminated on a substrate, and an aluminum electrode is formed on the aluminum electrode. In a method for manufacturing a semiconductor device in which an overcoat film is disposed, after forming a resist pattern on an oxide film, the oxide film is etched halfway by isotropic dry etching, and further until the substrate reaches by anisotropic dry etching. A contact hole is formed by etching, and aluminum is laminated on the contact hole. According to the present invention, a two-way etching is performed halfway through the oxide film by isotropic dry etching to form a tapered portion above the contact hole. A contact hole extending vertically from the portion to the substrate is formed in the oxide film. By sputtering aluminum on the contact hole with a tapered upper part, aluminum can be stacked in a tapered shape inside the contact hole without overhanging on the periphery of the contact hole on the top surface of the oxide film. It becomes. FIG. 1 is a sectional view of a semiconductor device according to an embodiment of the present invention. In FIG. 1, a semiconductor device according to an embodiment of the present invention includes a small contact hole 3 penetrating an oxide film 2 laminated on a semiconductor substrate 1.
Is provided. The contact hole 3 is formed so that a portion in contact with the semiconductor substrate 1 is perpendicular to the semiconductor substrate 1.
The upper part is formed in a tapered shape such that the contact hole 3 is enlarged. The area of the contact hole in contact with the semiconductor substrate 1 is 1 μm ² or less. The semiconductor device includes an aluminum electrode 4 electrically connected to the semiconductor substrate via the contact hole 3. On the aluminum electrode 4, an overcoat film 5 of SiN, SiO or the like is formed in order to prevent corrosion of the aluminum electrode 4. FIG. 2 is a process chart showing a method of manufacturing the semiconductor device of FIG. First, as shown in FIG. 2A, a pattern for forming the contact hole 3 of FIG. 1 is formed on the oxide film 2 formed on the semiconductor substrate 1 by using a resist 6. Next, as shown in FIG. 2B, the oxide film 2 is etched partway by isotropic dry etching. In the isotropic etching, etching is performed in two directions, that is, a direction perpendicular and a direction parallel to the opening surface 6a of the resist 6, so that a portion closer to the resist 6 is enlarged above the contact hole 3 as shown in the figure. Taper 3a
Is formed. Further, as shown in FIG. 1C, etching is performed by anisotropic dry etching until the semiconductor substrate 1 is reached. In the anisotropic etching, the etching is performed only in the direction perpendicular to the opening surface 6a of the resist 6, so that the lower portion of the contact hole 3 is vertically in contact with the semiconductor substrate 1 from the tapered portion 3 as shown. Vertical wall 3b is formed. Then, when the resist 6 is removed, a contact hole 3 in which a tapered portion 3a is formed in an upper portion and a vertical wall portion 3b is formed in a lower portion as shown in FIG. Subsequently, as shown in FIGS. 1E, 1F, and 1G, aluminum 7 is sequentially laminated on the oxide film 2 in which the contact holes 3 are formed by sputtering. At this time, since the tapered portion 3a is formed on the upper portion of the oxide film 2, the aluminum 7 is stacked in a tapered shape along the tapered portion 3a. Therefore, the aluminum electrode 4 is not partially thinned, and disconnection due to thinning and disconnection due to electromigration can be prevented. In addition, since the aluminum 7 is laminated in a tapered shape along the tapered portion 3a, the opening of the contact hole 3 can be blocked as in the related art without overhanging from the periphery of the contact hole 3 on the upper surface of the oxide film 2. Absent. As shown in FIG. 1H, an overcoat film 5 is formed on the aluminum electrode 4 formed by laminating the aluminum 7 by plasma. At this time, since the opening of the contact hole 3 is secured so as to expand toward the upper side of the aluminum electrode 4, the overcoat film 5 does not partially become thinner, but completely covers the aluminum electrode 4. It is formed as follows. Therefore, the overcoat film 5
Can be prevented from deteriorating the moisture resistance due to the partial thinning and the reliability of the semiconductor device from being corroded by the aluminum electrode 4. According to the present invention, after a resist pattern is formed on an oxide film, it is etched to the middle of the oxide film by isotropic dry etching, and further until it reaches the substrate by anisotropic dry etching. By forming a contact hole by etching, and laminating aluminum on the contact hole, aluminum is laminated in a tapered shape by a tapered portion formed on the upper part of the contact hole, and disconnection due to partial thinning of the aluminum electrode and Disconnection due to electromigration can be prevented. Further, since overhang of aluminum at the periphery of the contact hole can be prevented, aluminum can be laminated without blocking the opening of the small contact hole, and an overcoat film can be formed more favorably. The reliability of the semiconductor device can be improved by preventing electrode corrosion.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a cross-sectional view of a semiconductor device according to an embodiment of the present invention. FIG. 2 is a process chart showing a method for manufacturing the semiconductor device of FIG. 1; FIG. 3 is a diagram showing a process of manufacturing a semiconductor device by conventional anisotropic dry etching. [Description of Signs] 1 Semiconductor substrate 2 Oxide film 3 Contact hole 3a Tapered portion 3b Vertical wall portion 4 Aluminum electrode 5 Overcoat film 6 Resist 7 Aluminum

   ────────────────────────────────────────────────── ─── Continuation of front page    F-term (reference) 4M104 BB02 CC01 DD08 DD12 DD16                       DD37 EE05 EE16 EE17 FF07                       HH01 HH13 HH20                 5F004 AA12 DB03 EA29 EB01                 5F033 HH08 JJ01 JJ08 KK01 NN32                       PP15 QQ09 QQ11 QQ16 QQ22                       RR04 RR06 SS15 XX02 XX05                       XX18

Claims (1)

Claims: 1. Manufacturing a semiconductor device in which an aluminum electrode is formed in a contact hole penetrating an oxide film laminated on a substrate, and an overcoat film is disposed on the aluminum electrode. In the method, after forming a resist pattern on the oxide film, the contact hole is etched by etching to the middle of the oxide film by isotropic dry etching and further by anisotropic dry etching until reaching the substrate. Forming a layer of aluminum on the contact hole.