JP2564113B2 - Method for forming fine electrodes - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for forming a fine electrode, and in particular, after forming a PN junction, a fine electrode capable of accurately forming electrodes connected to respective regions with a predetermined size. And a method of forming the same.

<Prior Art> FIGS. 2A to 2F are process diagrams showing a conventional example, and FIG. 2A is a semiconductor substrate 2 on which a thermal oxide film 1 is grown.
Is represented. An opening 3 is formed in the thermal oxide film 1 through a lithography process (FIG. 2B), and impurities are diffused from the opening 3 to form a base region 4. An oxide film 5 is grown on the base region 4 during the diffusion process, and a step is formed between the thermal oxide film 1 and the oxide film 5 (FIG. 2 (c)). Subsequently, an emitter diffusion opening 6 is formed in the oxide film 5 (FIG. 2 (d)), and impurities are diffused from the opening 6 to form an emitter region 7. Since the oxide film 8 grows on the emitter region 7 even during the diffusion process of the emitter region 7, a step is again formed between the oxide film 5 and the oxide film 8 (FIG. 2 (e)). Therefore, in order to form an opening for an electrode, first, a photoresist is applied to the thermal oxide film 1 and the oxide films 5 and 8, and a photomask is brought into contact with the surface of the thermal oxide film 1.
Then, the photomask pattern is transferred to the photoresist film by exposure. After the post-baking, the photoresist film is patterned, and openings 9 and 10 are formed in the oxide films 5 and 8 by using the patterned photoresist film as a mask (FIG. 2 (f)).

<Problems to be Solved by the Invention> In the above-mentioned conventional example, the steps 9 and 10 are formed between the thermal oxide film 1 and the oxide films 5 and 8, respectively.
At the time of drilling, the distance from the photomask applied to the surface of the thermal oxide film 1 to the oxide films 5 and 8 becomes different. Generally, if the wavelength of the irradiated light is λ and the distance between the photomask and the photoresist film is G, the resolution R is G and λ.
Proportional to the square root of the product of and. Therefore, in addition to the dimensional accuracy of the opening 9 and the dimensional accuracy of the opening 10, there is a difference in film thickness between the oxide films 5 and 8, and the oxide film 8 is over-etched. The dimensions tend to have undesired values. Therefore, from the perspective of resolution 9,
Furthermore, from the viewpoint of over-etching, the base region 4 and the emitter region 7 must be formed large.

<Means for Solving Problems> In view of the above problems, the present invention forms an oxide film on the surface of a semiconductor substrate, introduces impurities of the first conductivity type, and then forms the oxide film on the surface of the semiconductor substrate by a CVD method. And using the oxide film as a mask to form a second conductivity type impurity region,
An opening is formed in the oxide film without removing the oxide film, and electrodes are respectively formed in the opening used for introducing the second conductivity type impurities and the newly formed opening. And

<Embodiment> FIGS. 1A to 1H show an embodiment of the present invention, in which 11 denotes an N-type semiconductor substrate, and the surface of the semiconductor substrate 11 has a thickness of A silicon dioxide film 12 having a thickness of about 1000Å is grown (Fig. 1 (a)). A photoresist 13 is applied on the silicon dioxide film 12, and after patterning, a P-type impurity with an impurity dose amount of about 10 ¹⁴ ions / cm ³ , for example, boron is ion-implanted into the semiconductor substrate 11 (see FIG. b)).

After removing the photoresist film, a silicon dioxide film 14 is deposited on the silicon dioxide film 12 by the CVD method to a thickness of about 1500 Å (Fig. 1 (c)), and a heat treatment process at about 900 ° C to 1000 ° C is performed to form a base A region 15 is formed (Fig. 1 (d)).

In the subsequent step, the opening 16 is formed in the silicon dioxide film 14 and the base region 15 is exposed. In the step of forming the opening 16, since the photoresist film is applied to the silicon dioxide film 14 and then the photoresist film is patterned by the contact exposure method, the pattern of the photoresist is accurately transferred to the photoresist film, and the opening of the desired size is formed. 16 can be drilled.

When the base region 15 is exposed, a polysilicon film 17 of about 500 to 1000 Å containing N-type impurities such as phosphorus is deposited on the exposed base region and the silicon dioxide film 14, and a cap is formed thereon. An oxide film is formed (first
Figure (e)). After the formation of the cap oxide film, phosphorus is diffused from the polysilicon film 17 into the semiconductor substrate 11 by heat treatment to form the N-type emitter region 18. After that, the cap oxide film is entirely removed by etching, and the polysilicon film 17 is etched except on the emitter region 18 (FIG. 1 (f)).

Then, openings 19 and 20 for base electrodes are formed in the silicon dioxide film 14 on the base region 15 (FIG. 1 (g)).
In forming the openings 19 and 20, since the surface of the silicon dioxide film 14 is flat, the photomask can be brought into close contact with the surface, and the openings 19 and 20 having desired dimensions can be formed. Therefore, a metal, for example, aluminum is vapor-deposited on the silicon dioxide film 14, the exposed base region 15 and the polysilicon film 17, and this is patterned to form the base electrode 21 and the emitter electrode 22 (first Figure 1 (h)). At this time, the base electrode 21 and the emitter electrode 22 are substantially on the same plane, and it can be said that the same applies to the formation of the openings 19 and 20 in the photomask process for forming the electrodes.

<Effect> As described above, according to the present invention, the first conductivity type impurity region is formed in the oxide film without removing the oxide film in which the opening for forming the second conductivity type impurity region is formed. Since the openings for exposing the holes are provided, and the electrodes are provided in the openings and the openings for forming the impurity regions of the second conductivity type, it is possible to form a pattern by the contact exposure method for forming any of the openings. It is possible to obtain an effect that it can be accurately formed in the dimension of. Moreover, since the size of the opening in which the electrode is formed can be precisely controlled, the first conductivity type impurity region and the second conductivity type impurity region can be reduced, and the integration degree can be improved, and further, the transistor The effect that the characteristics can be improved can be obtained.

[Brief description of drawings]

1 (a) to (h) are process diagrams of an embodiment of the present invention,
2A to 2F are process diagrams of a conventional example. 11 ... Semiconductor substrate, 13 ... Mask layer, 14 ... Oxide film, 15 ... First conductivity type impurity region, 16, 19, 20 ... Opening, 18 ... Second conductivity type impurity region, 21 , 22 …… Electrode.

Claims (1)

(57) [Claims] 1. A step of forming an oxide film on the surface of a semiconductor substrate, a step of introducing impurities of a first conductivity type into the semiconductor substrate by a mask layer formed on the surface of the oxide film, and a mask layer To remove the oxide film on the surface of the oxide film.
A step of forming using a CVD method, and forming an opening in the surface of the oxide film to introduce impurities into the surface of the semiconductor substrate through the opening to form an impurity region of the second conductivity type in the impurity region of the first conductivity type. A step of forming an opening in the oxide film to expose an impurity region of the first conductivity type; and a step of forming an oxide film on the impurity region of the first conductivity type and the impurity region of the second conductivity type. A method of forming a fine electrode, comprising a step of providing an electrode in each opening and connecting the electrode to an impurity region of a first conductivity type and an impurity region of a second conductivity type, respectively.