JPS5964517A - Formation of oxide film - Google Patents

Abstract

PURPOSE:To obtain a polysilicon oxide film having improved dielectric strength, by thermally oxidizing a polycrystalline silicon after ion-implantation. CONSTITUTION:An insulating film 7 is formed to the surface of the silicon substrate or wafer 1, coated with a polysilicon, subjected to the diffusion treatment, and patterned to form the capacitor electrode 6, etc. O<+>, N<+>, etc. are implanted into the electrode by ion implantation to form the ion implanted layer 10. The whole assembly is thermally oxidized or annealed at a specific temperature to form the oxide film 8 having desired thickness. A dynamic memory, etc. can be prepared from the product by conventional process. The polysilicon oxide film 8 obtained by this process is homogeneous and dense, and has excellent dielectric strength.

Description

DETAILED DESCRIPTION OF THE INVENTION (1) Technical Field of the Invention The invention relates to a method of forming an oxide film, particularly a method of forming a polysilicon oxide film used in a semiconductor device.

(2) Prior Art and Problems FIG. 1 shows an example of a one-transistor/l-cell dynamic memory. For example, a transistor (FET) consisting of a drain 2, a gate 4 on an insulating film 3, and a source (inversion layer) 5 is formed on a p-type silicon substrate 1, a capacitor electrode 6, an insulating film 7, and an inversion layer (capacitor electrode) 5. The gate 4 and the capacitor electrode 6 are usually made of polysilicon, and there is an r2 capacitor between them.
There is a green film 8, and this insulating film 8 is connected to the capacitor electrode 6.
It is formed by total thermal oxidation of polysilicon. However, recently, Memory Tani boar is 64-? As the cell size increases from 256 kilobits to 1 megabit, the cell size becomes smaller and the insulation layer must be made thinner.It is important to accurately form a defect-free film with high dielectric strength. is becoming necessary.

(3) Purpose of the Invention In view of the prior art, the present invention provides a polysilicon L-
The purpose is to improve the breakdown voltage of nQ1 oxide.

(4) Structure of the Invention In order to achieve the above object, the present invention provides an oxide film characterized in that ion implantation is performed on polycrystalline silicon, followed by heat treatment to thermally oxidize the core polycrystalline silicon. A forming method is provided.

That is, in the method of the present invention, ions are first implanted into polysilicon before thermally oxidizing the polysilicon as in the conventional method. This ion implantation refines the polysilicon crystal grains (makes them amorphous), and then heats them. Therefore, thermal oxidation of polysilicon with ion implantation will oxidize the polysilicon more easily and more uniformly than without ion implantation.
L, and gives a denser oxide film. Therefore, the breakdown voltage of the polysilicon oxide film is also improved. In addition, the implanted ions may be oxygen ions (0+), nitrogen ions (N+), argon ions (Ar+), etc., but if oxygen ions (0+) are used, in addition to the above effects, the implanted Since f-on promotes oxidation inside the polysilicon, more favorable results can be obtained. Incidentally, it is preferable that the ion implantation takes a short time in the case of the Glossene upper part.

(5) Example of the invention The method of the present invention is applied to the formation of the polysilicon oxide film 8 between the capacitor electrode 6 and the gate 4 in the one-transistor, one-cell dynamic memory described above (Second
(See Figures 4 to 4). The entire insulating film 7 is formed on the surface of the silicon substrate or wafer 1, and a polysilicon film with a total thickness of 400 mm is formed on it.
The capacitor electrode 6 is formed by adhering to 0A, fully adjusting the sheet resistance by diffusion treatment, and then patterning. after that,
0+.

N+ etc. are implanted to a depth of about 100 A (layer) at a dose of 10'/cd and an implantation energy of 10 to 100 keV.
Thermal oxidation (0□) or annealing (N2) at a temperature of 100℃
After that, a dynamic memory is fabricated by a normal process. The polysilicon oxide film 8 thus formed provides a more homogeneous and denser oxide film than the conventional one, and the withstand voltage is also greatly improved.

The above is an example in which the present invention is applied to the formation of an oxide film for insulation between polysilicon layers in dynamics, IRI, and memory, but it is clear that the present invention can also be applied to the formation of an oxide film for stacked capacitors, etc. .

(6) Effects of the Invention According to the present invention, it is possible to improve the breakdown voltage of a polysilicon thermal oxide film.

[Brief explanation of the drawing]

FIG. 1 is a 1-fold view of the dynamic memory, and FIGS. 2 to 4 are 19i side views of a step 8 for explaining the present invention in detail. 4: Gate (polysilicon), 6: Capacitor ff electrode (HOLJ silicon), 8: Polysilicon oxide film, 10:
Ion implantation layer. Patent applicant: Fujitsu Ltd. Patent attorney: °1 Akira Ki, patent attorney: Kazuyuki Nishidate, patent attorney: 1) Yukio, patent attorney: Akira Yamaguchi, 98- Figure 1 Figure 3-99-,-

Claims (1)

[Claims] 1. Do not implant ions into polycrystalline silicon, then heat-treat and thermally oxidize the polycrystalline silicon.
♀Method for forming oxide film.