JPH0653160A - Method of forming self-aligned contact - Google Patents

Abstract

PURPOSE:To form a self-aligned contact without leaving large steps by using a void formed intentionally in a silicon oxide film instead of using a step. CONSTITUTION:Gate electrode 3 and a cap silicon oxide film 4 are laminated on a silicon substrate 1, and a silicon oxide film 5 is deposited over the substrate so that a void 8 may be formed between the electrodes 3. The silicon oxide film 5, masked with a photoresist 6 having a window 9, is etched to make a contact hole 7 self-aligned with the void. In this manner, a self-aligned contact is formed on a flat surface with no steps remaining at the contact hole. This prevents troubles in subsequent steps such as exposure and etching, thus improving yield.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for forming a contact, and more particularly to a method for forming a self-aligned contact structure which allows some misalignment.

[0002]

2. Description of the Related Art As a technique for forming a self-aligned contact, for example, when a contact is self-aligned between gate electrodes, there is a method of actively utilizing the steps of the gate electrode as shown in FIG. Used more often than before.

That is, as shown in FIG. 2A, a silicon substrate 21 has a region partitioned by a silicon oxide film 22, and a gate electrode 23 and a cap silicon oxide formed on the silicon substrate 21. After the laminated structure with the film 24 is covered with the silicon oxide film 25, contact lithography is performed, and as shown in FIG.
An opening 28 is formed in the. At this time, the size of the opening 28 of the photoresist 26 may be larger than the actual contact size, or there may be some misalignment. After that, as shown in FIG. 2C, the silicon oxide film 25 is etched back, the photoresist is removed, and the contact opening 2 is self-aligned between the gate electrodes 23.
Form 7.

[0004]

However, the above-described conventional self-aligned contact forming technique has the following problems. That is, the above-described self-aligned contact forming technique forms a self-aligned contact by utilizing the step difference of the gate electrode or the like. Therefore, the step is always necessary for forming the contact, but the step is large, so that there is a problem such as residual etching due to etching in a later step, exposure, etc., and variations in resist size.

An object of the present invention is to solve the above conventional problems and provide a method for forming a self-aligned contact that does not leave a large step in a subsequent process.

[0006]

In order to achieve the above object, the self-aligned contact forming method according to the present invention includes a wiring forming step, an insulating coating film growing step, and a contact opening step. A self-aligned contact forming method for forming a contact in a contact region adjacent to a wiring, in which the wiring forming step comprises sequentially forming a wiring material film and a first insulating film on a substrate, and then forming an extra first film. This is a step of removing the insulating film and the wiring material film, and forming a pair of a laminated structure of the first insulating film and the wiring adjacent to the contact formation region with the same width. The step of growing the second insulating film by overhanging on the step portion generated by the laminated structure of the insulating film and the wiring, and the contact opening step removes the second insulating film in the contact region by etching. A step of forming a contact opening leading to voids formed below the overhang.

[0007]

In the method of forming a self-aligned contact of the present invention, a contact is not formed by utilizing a step, and a void is intentionally formed in the contact formation region when the silicon oxide film is grown, and this void is used. Self-aligned contacts are formed as a result, and therefore no step is required at the time of opening the contact.

[0008]

The present invention will be described below with reference to the drawings. FIG. 1 is a diagram showing an embodiment of the present invention in the order of steps. In the figure, 1 is a silicon substrate, 2 is a silicon oxide film, 3 is a gate electrode, 4 is a cap silicon oxide film,
Reference numeral 5 is a silicon oxide film, 6 is a photoresist, and 7 is a contact opening.

First, in FIG. 1A, a silicon oxide film 2 is formed on a silicon substrate 1 by selective oxidation of silicon, and after a step of gate oxidation, a polysilicon film is formed on the entire surface of the substrate.
A silicon oxide film is deposited in this order by the CVD method. Then, the silicon oxide film and the polysilicon film are etched in the step of forming the gate electrode to form a laminated structure of the gate electrode 3 on the silicon substrate 1 and the cap silicon oxide film 4 formed on the silicon substrate 1 with the same width. obtain.

Next, after forming a diffusion layer by ion implantation or the like, a silicon oxide film 5 is deposited on the entire surface by plasma CVD as shown in FIG. When the film is deposited by the plasma CVD method, an overhang shape protruding on the step portion between the gate electrodes 3 and 3 is formed.
The space is not completely filled with the oxide film 5, and a void 8 is generated.

Next, an opening 9 is formed in a part of the photoresist 6 in the contact formation region by a contact photolithography process as shown in FIG. Next, the contact opening 7 is formed by etching the silicon oxide film 5 on the contact formation region (see FIG. 1).
(D)).

Since voids 8 exist in the contact formation region during this etching, the film thickness to be etched is smaller than the contact depth. Therefore, even if misalignment occurs during exposure of the contact, the gap between the gate and the contact can be increased. The insulation is maintained and the contacts open in self-alignment.

[0013]

As described above, according to the present invention, a self-aligned contact can be formed on a flat surface, and no large step remains after opening. Therefore, it is possible to reduce the problems that occur in the exposure and etching in the subsequent process, and therefore, it is possible to improve the manufacturing yield.

[Brief description of drawings]

1A to 1D are diagrams showing a process procedure used in an embodiment of the present invention.

2A to 2C are diagrams showing a process procedure of a conventional self-aligned contact forming method.

[Explanation of symbols]

 1 Silicon Substrate 2 Silicon Oxide Film 3 Gate Electrode 4 Cap Silicon Oxide Film 5 Silicon Oxide Film 6 Photoresist 7 Contact Opening 8 Void 9 Photoresist Opening

Claims (1)

[Claims] 1. A self-aligned contact forming method for forming a contact in a contact region adjacent to a wiring, which comprises a wiring forming step, an insulating coating film growing step, and a contact opening step. The wiring material film and the first insulating film are sequentially formed on the substrate, and then the excess first insulating film and the wiring material film are removed, and a pair of the laminated structure of the first insulating film and the wiring is formed. Is formed adjacent to the contact formation region with the same width, and the insulating coating step overhangs the second insulating film by overhanging on the step portion generated by the laminated structure of the first insulating film and the wiring. The contact opening step is a step of growing, and the contact opening step is a step of etching and removing the second insulating film in the contact region to form a contact opening communicating with a void formed below the overhang. Self-aligned contact formation method.