JP3034377B2 - Method for manufacturing capacitor electrode in semiconductor device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor device,
RAM (Dynamic RANDAM Access)
And a method of forming an electrode of a capacitor portion in the memory section.

[0002]

2. Description of the Related Art In a semiconductor device, especially a DRAM requiring a capacitor, when a rough polysilicon film having an uneven surface is used for the lower electrode of the capacitor, the surface area is smaller than when a conventional polysilicon film is used. And a capacity (C _s ) as much as 2.5 times can be obtained.

FIG. 2 shows a conventional example of forming such a rough surface polysilicon film.

First, as shown in FIG. 2A, a second polysilicon 5 as a storage electrode is formed on a word line or an insulating film formed on a semiconductor substrate 1, and the polysilicon 5 is formed. When the surface is roughened by a CVD (chemical vapor deposition) method, fine irregularities are formed on the polysilicon 5 as shown in FIG. Thereafter, the uneven polysilicon 5 is patterned into a storage electrode, and a capacitor dielectric film is further formed thereon, so that the area S of the capacitor dielectric film increases, which is about twice as large as that in the case where there is no unevenness. of C _s is obtained.

In the above-described manufacturing method, once the polysilicon 5 is formed, the substrate is once taken out of the processing apparatus (chamber), and then the substrate is put in a CVD apparatus to roughen the surface as described above. That is, deposition is performed twice. This is commonly called a two-stage depot.

[0006]

However, in the above-described two-stage deposition of a rough polysilicon film, after the lower polysilicon film or the amorphous silicon film is formed, the processing apparatus is once used as described above. LPCVD
(Low pressure CVD) Take out of furnace, then LPCVD again
A rough polysilicon film had to be formed in a furnace.

Further, since the shape of the irregularities on the surface of the rough polysilicon film changes due to the heat treatment, non-uniformity of the heat treatment in the batch at the time of taking out from the LPCVD furnace causes a change in the irregularities, and the variation in the capacitance of the capacitor increases. There was a problem.

SUMMARY OF THE INVENTION An object of the present invention is to improve the problem of the throughput of the two-step deposition of the rough polysilicon film and the problem of the unevenness of the unevenness described above.

[0009]

In order to achieve the above object, the present invention provides a method for forming a rough polysilicon film by LPCVD.
An amorphous silicon film or a polysilicon film is formed as a film by a method, and a silicon nitride film or a silicon oxynitride film is formed on the amorphous silicon film or the polysilicon film in the same chamber. , A rough polysilicon film was formed in the same furnace.

After forming the rough polysilicon, a silicon nitride film or a silicon oxynitride film is formed on the rough polysilicon film, and then the furnace is evacuated, purged with N ₂ , returned to normal pressure, and unloaded. It was done.

[0011]

According to the present invention, as described above, since the silicon nitride film is deposited in the same furnace, it is not necessary to remove the silicon nitride film from the furnace once, as compared with the conventional two-stage rough polysilicon film deposition. An improvement in time throughput can be expected. Also, by changing the thickness of the lower polysilicon film,
A lower electrode having a desired thickness can be formed regardless of the conditions for forming the upper rough surface polysilicon film.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The manufacturing process of an embodiment of the present invention is shown in FIG. 1 and will be described below.

First, as shown in FIG. 1A, an oxide film 2 as an insulating film is formed on a silicon substrate 1 at 950 ° C. in a WetO ₂ atmosphere. LPC using SiH ₄ on it
Reaction temperature 620 ° C, reaction pressure 0.2 Torr by VD method
To deposit a polysilicon film 3. This may be an amorphous silicon film. Next, place Si in the same chamber.
An H ₂ Cl ₂ / NH ₃ gas is introduced to form a silicon nitride film 4 on the surface of the polysilicon film 3 to a thickness of 10 to 20 °.

Next, as shown in FIG. 1B, an SiH ₄ gas is again introduced into the same chamber used in the above step, and an amorphous silicon film (rough silicon film) is formed at a reaction temperature of 570 ° C. and a reaction pressure of 0.2 Torr. 5). At this time, since the silicon nitride film 4 is present, the deposited amorphous silicon film is not affected by the crystallinity of the underlying polysilicon film 3 or amorphous silicon film.

Next, by performing heat treatment in the same furnace for 5 to 80 minutes, crystal grains are formed on the surface of the amorphous silicon film, and a rough polysilicon film 5 having irregularities is obtained. Next, a SiH ₂ Cl ₂ / NH ₃ gas is introduced into the furnace, and a silicon nitride film 6 is
0 ° is formed.

[0016] Then as shown in FIG. 1 (c), the vacuum, N ₂
After purging and returning to the atmospheric pressure, the chamber is taken out of the chamber. After the silicon nitride film 6 on the surface of the rough polysilicon film 5 is taken out of the chamber, it is removed by HF treatment. Next, an n-type impurity is introduced and diffused to provide conductivity and form a capacitor lower electrode.

Here, since the silicon nitride film 4 is as thin as 10 to 20 °, it does not affect the resistance and capacitance of the capacitor electrode.

In the above description, Si ₂ H ₂ Cl ₂ / NH ₃ / N ₂ O is used instead of the SiH ₂ Cl ₂ / NH ₃ gas, and the portions 4 and 6 are formed of a silicon oxynitride film. Is obtained.

[0019]

As explained above, according to the present invention,
Since a silicon nitride film was deposited in the same furnace,
Compared with the conventional two-stage rough-surface polysilicon film deposition, there is no need to once remove from the furnace, and an improvement in throughput of about 3 hours can be expected. By changing the thickness of the lower polysilicon film, a lower electrode having a desired thickness can be formed without depending on the conditions for forming the upper rough surface polysilicon film.

In addition, since the silicon nitride film is formed on the film surface in the same furnace after the formation of the amorphous silicon by the amorphous silicon deposition and the heat treatment, the crystallization from the surface of the rough polysilicon film is stabilized. (Stop), there is no influence of the heat treatment in the post-process, especially when taking out from the chamber, and it is possible to form a rough polysilicon film with excellent uniformity between wafers.

[Brief description of the drawings]

FIG. 1 shows an embodiment of the present invention.

FIG. 2 Conventional example

[Explanation of symbols]

 Reference Signs List 1 silicon substrate 2 oxide film 3 polysilicon film or amorphous silicon film 4, 6 silicon nitride film 5 rough polysilicon film

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-4-196435 (JP, A) JP-A-5-304273 (JP, A) JP-A-5-175456 (JP, A) (58) Field (Int.Cl. ⁷ , DB name) H01L 27/108 H01L 21/318 H01L 21/822 H01L 21/8242 H01L 27/04

Claims (2)

(57) [Claims] (A) forming an insulating film on a semiconductor substrate;
Forming a first film made of a polysilicon film or an amorphous silicon film thereon, and (b) removing the semiconductor substrate on which the first film is formed from the processing device in the above process without removing the semiconductor substrate on which the first film is formed. Forming a second film made of a silicon nitride film on the first film, (c) further comprising an amorphous silicon film on the second film in the same processing apparatus following the above step Third
Forming a third film into a polysilicon film having an uneven surface by depositing the film and performing a heat treatment. A method for manufacturing a capacitor electrode in a semiconductor device, comprising: . 2. The method according to claim 1, wherein a silicon oxynitride film is formed as the second film instead of the silicon nitride film.