JPS60770A - semiconductor equipment - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] [Field of Application of the Invention] The present invention relates to a semiconductor device, particularly a semiconductor integrated circuit memory, and relates to a semiconductor device that achieves a good large capacity without increasing the planar area of its storage capacitor. [Background of the Invention] Conventional storage capacitors have been formed on flat Si substrates, so as semiconductor integrated circuit memories become more highly integrated and finer, the area that can be occupied decreases and the signal capacity decreases. There were drawbacks. In order to maintain a large signal capacity, one method is to increase the dielectric constant of the insulating film and make it thinner, but recently it has been found that trenches are dug in the S+ substrate and the side walls of the trenches are utilized without increasing the planar area. A method of increasing the surface ft has been proposed. However, there was a drawback that the dielectric strength of the storage capacitor formed by forming 5io2i in the groove formed by this method by the thermal oxidation method was about 1.2 even if it was formed on a normal plane.

[Purpose of the invention]

An object of the present invention is to provide a storage capacitor structure that achieves an increase in capacitance due to an increase in effective area without impairing dielectric strength, in a storage capacitor that uses a side wall portion formed by digging a trench in a Si substrate. An object of the present invention is to provide a method for manufacturing the same.

[Summary of the invention]

Conventionally, sharp edges were generated by trenching an 8i substrate, and when a 5in2 film was subsequently formed by thermal oxidation, the dielectric strength deteriorated.

The present invention has a three-layer insulating film structure in which a thermally oxidized Sr02 film is first formed on the trench, then Si3N4 is formed by vapor phase growth, and finally Si3N4 is oxidized by thermal oxidation. This realizes a large storage capacity with a dielectric strength comparable to that of a flat structure.

[Embodiments of the invention]

An embodiment of the present invention will be described below with reference to FIGS. 1 and 2.

A mask material 2 such as a SiO□ film is applied on a P-type S+ substrate 1 of about 10 Ω·cm, and unnecessary portions are removed by photoetching or the like to form an opening. As shown in Part 2 below, CC
l2. CF4. Etch grooves 5 with a depth of about 4 μm were formed in desired portions of the 83 substrate 1 by a parallel plate plasma etching method using a gas containing SF6 as a main component. Thereafter, the 8i02 film 2 used as a mask is removed to expose the Si groups &. Thereafter, a capacitor insulating film 3 is formed.

Thereafter, polycrystalline silicon, ir, and 2 were formed using a low-pressure OVD method, and phosphorus was added at a high concentration to form a capacitor electrode.

An insulating film for a capacitor was first formed using a conventional method of thermal oxidation to form a SiO film to a thickness of about 20 nm. At this time, prior to thermal oxidation, in order to remove crystal damage and contamination on the dry etched surface, a mixed solution of N H40H and H20z or M
The 8+ substrate surface was slightly cleaned and slightly removed with the F+HNO3 mixture.

In addition, as another method for forming an insulating film, Sio
2 films are formed, and Si3N is deposited on it by low pressure OVD method.
Finally, this S i 3N4 film is oxidized by H2-〇□ gas combustion method to form 8i02/8i 3N4
A three-layer structure film of /SiO2 was formed with a total thickness of 20 nm.

In addition, other methods such as a Si3N4/SiO2 two-layer structure film and an 8r02 film formed by a reduced pressure OVD method were also carried out.

The dielectric strength voltage of a 5-inch double-film canister formed by a conventional thermal oxidation method was measured. The results are shown in Figure 3.
Here, the dielectric strength voltage was defined as the voltage when a leakage current of 10 nA flows. The area of the electrode is 5.8xlO'μm2, and a capacitor formed on a flat 8i substrate with no etched grooves is compared with a capacitor formed on an 8i substrate with 3600 etched grooves (groove type capacitor). It was shown.

As a result, while the dielectric strength of the planar capacitor is 18V, the dielectric strength of the trench capacitor is extremely poor at about 7V.

On the other hand, S I Q□/Si3N4/SiO2 according to the present invention
With a three-layer insulation film structure, as shown in Figure 4, the insulation film breakdown voltage of a planar capacitor is approximately 21V, while even a trench capacitor has a dielectric breakdown voltage of approximately 20V, so there is almost no deterioration in insulation voltage. . The above-mentioned slight difference of about lV.

In the case of a trench type capacitor, this is due to an increase in the effective capacitor area and is not an essential difference.

〔Effect of the invention〕

In addition, S ta N 4/8 + 0 in other embodiments
2 double layer film and SiO2 film made by low pressure vapor phase growth method, etc.
Although the dielectric strength of the trench capacitor is superior to that of the SjO□ single-layer film formed by thermal oxidation, the 5in2 of the present invention
/5i3N4/ There is nothing superior to the three-layer SiO2 film structure.0 As described above, the 5in2/ Si3N4/ Si of the present invention
The O2 three-layer insulating film structure exhibits good dielectric strength even when the 8J substrate is shaped at an acute angle, such as a trench capacitor formed by digging a trench, so it is suitable for semiconductor memory. It is extremely effective when used as a storage capacity.

[Brief explanation of drawings]

FIGS. 1 and 2 are diagrams showing the process of manufacturing a trench type capacitor, and FIGS. 3 and 4 are diagrams showing the dielectric strength of the conventional and the present invention, respectively. 1, 8+ substrate 2, dry etching mask 8i0□ film 3, capacitor insulating film 4, phosphorous-doped polycrystalline 8i 5, etch groove, enamel, bloom 5

Claims (1)

[Claims] 1. In the storage capacitor provided in the area including the sidewalls of the trench dug into the silicon substrate, the insulating layer portion forming the storage capacitor is made of silicon dioxide (8j02) and silicon nitride (S; 3N4).
), a semiconductor device characterized by having a three-layer insulating film structure made of silicon dioxide (8j02).