JPH0927597A - Semiconductor device and its manufacture - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a semiconductor device which has a simple manufacturing process and can ensure the capacitance of a capacitor and to provide its manufacturing method. SOLUTION: An electrode, on one side, which constitutes a capacitor is a laminated body wherein expansive conductive films 32 whose grains are grown by a heat treatment and thermally stable conductive films 31 which are stable against a heat treatment are laminated alternately. Peripheral edge parts of the expansive conductive films protrude from peripheral edge parts of the thermally stable conductive films which are laminated at their upper and lower parts. In order to realize such a structure, the laminated body is manufactured in a laminated-film formation process wherein the expansive conductive films whose grains are grown by the heat treatment and the thermally stable conductive films which are stable against the heat treatment are formed alternately, in a patterning process in which the laminated body laminated in the film formation process is patterned and in a heat treatment process wherein the patterned laminated body is heat-treated and the expansive conductive films are grain- grown.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor device having a capacitor such as a DRAM having an increased capacitor capacity and a manufacturing method thereof.

[0002]

2. Description of the Related Art With the high integration of semiconductor devices, the minimum design rule has been miniaturized, and the cell area of memory devices such as DRAM and SRAM has been reduced. For this reason, it has become difficult to secure the capacity of the capacitor, which is a constituent element of these memory devices.

As a capacitor structure for increasing the capacity of such a capacitor, there is one shown in FIG. In the manufacturing process of the capacitor of FIG. 3, as shown in FIG. 3A, a short-axis columnar lower electrode 3 connected thereto is formed on a substrate 2 made of silicon or the like, and then, as shown in FIG. As shown in FIG. 3, an insulating film 4 is formed by covering the lower electrode 3, and further, as shown in FIG.
As shown in (C), it is manufactured by covering the insulating film 4 with the conductive film 5 as the upper electrode to form a film.

[0004] Such a capacitor element can increase the capacity by making the capacitor three-dimensional, but the capacity is insufficient for the recent reduction of the cell area. In addition, various proposals have been made to secure the capacity of the capacitor,
In order to reduce the memory cell area and increase the surface area of the capacitor, the electrode structure and forming process of the capacitor element have become very complicated, and the number of steps has also increased significantly.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a semiconductor device in which a manufacturing process is simple and a capacitance of a capacitor can be secured, and a manufacturing method thereof.

[0006]

In order to achieve the above object, the present invention provides the following semiconductor device and its manufacturing method. (1) In a semiconductor device in which a large number of capacitors are formed, one electrode constituting the capacitor is formed by alternately laminating an expanded conductive film that is grain-grown by heat treatment and a heat-stable conductive film that is stable against heat treatment. A semiconductor device, which is a laminated body, wherein the peripheral edge portion of the expanded conductive film projects from the peripheral edge portions of the heat-stable conductive films that are stacked above and below the expanded conductive film. (2) The semiconductor device according to (1), wherein the expanded conductive film is made of silicide. (3) The semiconductor device according to (1) or (2), wherein the heat-stable conductive film is made of polysilicon. (4) In a method of manufacturing a semiconductor device, in which one electrode forming a capacitor of a semiconductor device is formed, an expansive conductive film that undergoes grain growth by heat treatment and a heat stable conductive film that is stable against heat treatment are alternately formed. And a heat treatment step of subjecting the patterned laminate to a heat treatment to grain-expand the expansive conductive film by patterning the laminated body laminated by the laminated film formation step. Of manufacturing a semiconductor device. (5) The method for manufacturing a semiconductor device according to (4), wherein the expandable conductive film is silicide and the heat stable conductive film is polysilicon.

The semiconductor device of the present invention is characterized by the structure of the capacitor. For example, one of the electrodes forming the capacitor is an expansive conductive film that is grain-grown by heat treatment and a heat-stable conductive film that is stable against heat. Can be manufactured by alternately stacking the layers, patterning the layers, and then heat-treating the grains to grow the expansive conductive film. The expansive conductive film is grain-grown, whereby the peripheral edge of the expansive conductive film has a structure protruding from the peripheral edge of the heat-stable conductive film, and the side surface of one of the electrodes forming the capacitor has a structure in which irregularities are formed. .

Therefore, since the side surface of the electrode is uneven,
The surface area of the capacitor is increased, and the capacity of the capacitor is increased with a small occupied area. In addition, the process is easy and a reliable structure can be obtained. In this case, silicide is preferable as the expansive conductive film because grain growth due to heat treatment is remarkable, and as the thermally stable conductive film, polysilicon that is stable and hardly expands against the heat treatment is preferable.

[0009]

Embodiments of the present invention will be specifically described below with reference to the drawings. FIG. 1 is a sectional view showing a capacitor element in a semiconductor device of the present invention. The capacitor 1 is connected to the substrate 2 and has a structure in which a short-axis columnar lower electrode 3 protruding from the substrate 2 is covered with an upper electrode 5 via an insulating film 4. This lower electrode 3
Has a laminated structure (five layers in the figure) in which the heat stable conductive film 31 and the expanded conductive film 32 are sequentially stacked from the substrate side, and the peripheral edge 32 a of the expanded conductive film 32 is formed of the heat stable conductive film 31. It has a structure protruding from the peripheral edge 31a. Since the peripheral edge of the expanded conductive film 32 is projected from the heat-stable conductive film 31 in this manner, unevenness is formed on the side surfaces of the lower electrode 3 and the capacitor 1, and the surface area is larger than that of a simple columnar capacitor. Is increasing. Therefore, the capacitance of the capacitor is larger than the area occupied by the capacitor.

Here, for the expansive conductive film, it is necessary to select a material that causes grain growth by heat treatment, and this structure can be realized. Examples of such a material include silicide such as tungsten silicide. The heat-stable conductive film is made of a material that is stable to the heat treatment for grain-growing the expansive conductive film and hardly expands by the heat treatment, and specifically, polysilicon can be exemplified.

The thickness and the number of laminated layers of each film constituting the lower electrode are not particularly limited, but the thickness is, for example, 50 to 100 n.
m, and the number of laminated layers can be 2 to 10 or more. Next, a method of manufacturing the capacitor according to the present invention will be described with reference to FIG. (A) Laminated film forming step First, although not shown, for example, 20 keV, 10 ¹⁵
Ion implantation under the condition of / cm ³ . Next, as shown in FIG. 2A, a polysilicon film 31 doped with impurities, for example, as a heat stable conductive film, and a tungsten silicide film 32 ', for example, as an expansive conductive film, are alternately formed with a film thickness of 50 nm by a CVD method. To form a laminated film. (B) Patterning Step After resist patterning by the lithography method, anisotropic etching, for example, C by using the resist RE as a mask.
The capacitor lower electrode is patterned by ECR etching or the like using l ₂ / O ₂ as an etching gas. (C) Heat treatment step After removing the resist RE, for example, at 850 ° C., N ₂ + O
Heat treatment is performed under the conditions of ₂ gas and 10 min. As a result, the polysilicon film 31 is stable against heat,
Although not expanded, the grains of the tungsten silicide film 32 'grow and the peripheral edge of the tungsten silicide film 32 protrudes from the peripheral edge of the polysilicon film 31 to form a protrusion 32b, as shown in FIG. 2C. Therefore, unevenness is formed on the side surface of the lower electrode 3 to increase the surface area.

The heat treatment conditions are not limited to the above-mentioned conditions, but may be, for example, a temperature of 800 to 850 ° C. and a heat treatment time of 10 to 30 minutes. (D) Capacitor upper electrode forming step As the capacitor insulating film, the insulating film 4 is made of TEOS (tetraethoxysilane) by using, for example, a low pressure CVD apparatus.
To form a film. Next, a conductive film, for example, polysilicon doped with impurities is formed and patterned to form the capacitor upper electrode 5.

Through the above steps, the capacitor element as shown in FIG. 1 can be manufactured. This step can be easily performed. The obtained capacitor can have a large capacitor surface area with a small occupied area, and the capacity can be easily secured. Such a capacitor is
For example, the present invention can be applied to all semiconductor devices having capacitors such as DRAM, and in addition to DRAM, for example, L having a capacitive element.
It can also be applied to a CD (liquid crystal device), an FRAM (ferroelectric thin film memory), or the like.

[0014]

The semiconductor device of the present invention can increase the capacitance of a capacitor with a small occupied area and meet the demand for reduction of the memory cell area. Further, according to the method of manufacturing a semiconductor device of the present invention, the capacitor can be formed by an easy process.

[Brief description of drawings]

FIG. 1 is a sectional view showing a structure of a capacitor of a semiconductor device of the present invention.

2A to 2D are cross-sectional views showing a manufacturing process of the capacitor of the present invention.

3A to 3C are schematic cross-sectional views showing steps showing a conventional manufacturing process of a capacitor.

[Explanation of symbols]

1 Capacitor 2 Substrate 3 Capacitor Lower Electrode 31 Thermally Stable Conductive Film 32 'Expandable Conductive Film Before Grain Growth 32 Expandable Conductive Film 32b Projection 4 Capacitor Insulating Film 5 Capacitor Upper Electrode

Claims (5)

[Claims] 1. In a semiconductor device having a large number of capacitors formed therein, one of the electrodes constituting the capacitor is formed by alternately laminating expanded conductive films grain-grown by heat treatment and thermally stable conductive films stable against heat treatment. And a peripheral portion of the expanded conductive film projecting from the peripheral portions of the heat-stable conductive films stacked above and below the expanded conductive film. 2. The semiconductor device according to claim 1, wherein the expanded conductive film is made of silicide. 3. The semiconductor device according to claim 1, wherein the heat stable conductive film is made of polysilicon. 4. A method of manufacturing a semiconductor device, wherein one electrode constituting a capacitor of a semiconductor device is formed, wherein an expansive conductive film that is grain-grown by heat treatment and a heat stable conductive film that is stable against heat treatment are alternately formed. A laminated film forming step of forming a film; a patterning step of patterning the laminated body laminated by the laminated film forming step; and a heat treatment step of heat-treating the patterned laminated body to grain-expand the expansive conductive film. A method for manufacturing a characteristic semiconductor device. 5. The method of manufacturing a semiconductor device according to claim 4, wherein the expansive conductive film is silicide, and the thermally stable conductive film is polysilicon.