JPH0430466A - Semiconductor electrode - Google Patents

Abstract

PURPOSE:To make polysilicon uniform in grain size so as to enable stress to act uniformly on an oxide film provided thereunder by a method wherein a protective film of nitride or the like is formed on an electrode of polysilicon or the like. CONSTITUTION:A field active region 1 is formed on a substrate 4, then a capacitor insulating oxide film 3 is provided, and a polysilicon 2 is deposited. In succession, a nitride film 7 is formed, and an oxide film 3 is deposited thereon. process follows, where a word line 6 and a bit line 5 are formed. By this setup, the cell plate polysilicon 2 located under the word line 6 is protected by the thin nitride film 7, and the cell plate polysilicon 2 is protected against oxidation in a thermal treatment and kept uniform and small in grain size. Therefore, only by adding a simple process, stress acting on the film 3 is made uniform, whereby a semiconductor electrode can be improved in reliability.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] This invention relates to electrodes for semiconductor capacitors and the like.

[Conventional technology]

Conventionally, it has been common to use only an oxide film on an electrode made of a conductor used in a capacitor or the like.

As an example, the case of a capacitor forming a memory cell of a dynamic random access memory (hereinafter referred to as DRAM) will be described. It was shaped like a rice scoop as shown in Figure 2. A field active region (1) in which impurities are implanted into a semiconductor substrate, and an electrode for a cell plate made of chemically deposited polysilicon (2) on which an insulating film (2) made of an oxide film or a nitride film is interposed. 3) constitutes the memory cell of F.

The field active region (1) is a node that stores electrical information, and the polysilicon electrode (2) is fixed at a constant potential and is insulated by an oxide film or a nitride film, functioning as a capacitor.

As a method for manufacturing a semiconductor electrode, a P-type semiconductor substrate (4)
First, areas other than the rice scoop-shaped field active region (1) in FIG. 2 are oxidized to form a KN-type diffusion layer (1) under the polysilicon that will become the capacitor part. Impurities are formed by ion implantation.

After that, a silicon oxide film (Si
02) Chemically deposit +31 to deposit the first polysilicon (2) which will become the cell plate.

Furthermore, it is used as a transistor for cell selection.

After forming the oxide film (3), N20 polysilicon is made to form the sheath of the transistor. Inject an N-type obtuse material to become the drain, and bit I for reading/writing information transmission.
I (5) is formed of silicon oxide of a high melting point metal such as tungsten silicide after the contact hole (6) for electrical connection with the source of the transistor is fully opened.

Figure N3 shows a cross-sectional view of the memory cell portion. As shown by the dotted line, a word line (6) for selecting an adjacent cell runs above the cell plate. For this reason, the first polysilicon, which is the cell plate below this word line (6), is further oxidized in areas other than the word line due to the heat treatment after the second polysilicon is devoted and the impurity implanted into the diffusion layer. , even though the grains grow and become larger, the grain size remains as small as 1 element.

The state is shown in FIG.

[Problem to be solved by the invention]

Conventional semiconductor electrodes were constructed as described above, so
Under the second polysilicon, which is a word line, the first polysilicon, which is a cell rate, is not oxidized and remains with a small grain size despite various heat treatments.

At this time, it is considered that the stress generated in the @1 polysilicon film tends to become unbalanced at the boundary between the small grain size and the large grain size.

If an imbalance occurs, the stress applied to the extremely thin oxide film for capacitor insulation will also be unbalanced, and if there is an imbalance in the stress applied to this oxide film, it will greatly affect the reliability of the insulation oxide film. give.

For example, there have been problems such as accelerating bit defects that occur during continuous use after the product has been manufactured, and further shortening the life of the product.

This invention was made to solve the above-mentioned problems. It is possible to make the grain size of W and l polysilicon uniform by adding a simple process, and it also makes the stress on the oxide film uniform, improving reliability. The aim is to obtain semiconductor electrodes with high properties.

[Means to solve the problem]

In the semiconductor electrode according to the present invention, a protective film is formed on conventional polysilicon, and the grain size of the polysilicon is made uniform, so that the stress applied to the underlying oxide film K is made uniform.

[For production]

Since the semiconductor electrode in this invention is covered with a thin protective film, it will not be oxidized and grow grains during subsequent heat treatment, and the surface in contact with the capacitor oxide film, regardless of whether it is above or below the word line, Because the grain sizes are always the same, there is no stress imbalance.

Therefore, the stress applied to the capacitor oxide film K is uniform everywhere, making it possible to ensure high reliability.

〔Example〕

An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is an enlarged sectional view of a word line portion of a memory cell according to an embodiment of the present invention.

In the figure, (1) is a diffusion layer, (2) is a cell plate polysilicon, (3) is an oxide film, (4) is a substrate, and (6) is a
(7) is a word line, and (7) is a nitride film.

In FIG. 1, the cell plate polysilicon (2) located below the hatched word line (6) is covered with a thin nitride film (
7).

As a result, cell plate polysilicon (2) was produced.

Even after heat treatment, the grain size remains small without being oxidized.

The method for manufacturing a semiconductor electrode is similar to the conventional process, after creating a field active region (1) on a substrate (4),
An oxide insulating film (3) for the capacitor is created, and first polysilicon (2) is deposited. After that, nitride film ('7)
After that, an oxide film (3) is deposited.

The subsequent creation of the word line (6) and bits 41 and 5 is performed in exactly the same manner as the conventional method, and there is no problem.

〔Effect of the invention〕

As described above, according to the present invention, it is possible to obtain electrodes for capacitors used in semiconductors with significantly improved reliability compared to conventional methods by simply adding a simple process.

[Brief explanation of the drawing]

FIG. 1 shows a semiconductor electrode according to an embodiment of the present invention.
2 is a plan view of the memory cell portion of a conventional DRAM, FIG. 3 is a sectional view of the memory cell portion of a conventional DRAM, and FIG. 4 is a cross-sectional view of the memory cell portion of the conventional DRAM. FIG. 3 is an enlarged cross-sectional view of a portion. In the figure, (1) is a diffusion layer, (2) is a cell plate polysilicon, (3) is an oxide film, (4) is a substrate, and (6) is a
indicates a word line, and (7) indicates a nitride film. In addition, the same symbols in the figures indicate the same or equivalent parts.

Claims (1)

[Claims] In a capacitor formed on a P-type or N-type semiconductor substrate, the semiconductor substrate is used as one electrode, and a thin oxide film is sandwiched between the capacitors and the other electrode made of a conductor such as polysilicon formed thereon. A semiconductor electrode characterized in that it is coated with an electrically insulating protective film such as a nitride film.