JPH0658910B2 - Semiconductor device - Google Patents

Description

The present invention relates to a semiconductor device, and more particularly to a semiconductor device with reduced characteristic deterioration in a radiation environment.

(Prior Art) As shown in FIG. 2, a conventional semiconductor device has an oxide film 2 having a thickness of about 1 μm for protecting a semiconductor surface and a silicon oxide film 3 having a thickness of about 1 μm for separating elements. It is common to have

(Problems to be Solved by the Invention) In the above structure, when the radiation environment, particularly heavy particles such as α-rays, and electron rays γ-rays are irradiated, the electrons are emitted in the silicon oxide films 2 and 3. Hole pairs are generated, and the mobility of which is smaller than that of electrons, which is one millionth, is smaller than that of electrons.
Are easily trapped by the hole traps existing near the interface between the silicon oxide films 2 and 3, and the amount of generated holes is proportional to the thickness of the silicon oxide film. Then, the holes trapped by the hole traps are more likely to be absorbed on the surface of the semiconductor substrate 1 by N.
For example, in the case of a P-type semiconductor substrate, the interface between the P-type base region 6 and the silicon oxide film 2 in contact with the NPN pyramidal transistor formed on the semiconductor substrate 1 shown in FIG. There is a drawback in that the increase and the decrease in the direct current amplification factor occur. Further, as shown in FIG. 2, in the case where the silicon oxide film 3 for separating the adjacent transistors is, for example, a P-type semiconductor substrate, the interface between the semiconductor substrate 1 and the silicon oxide film 3 is used as a path to establish a conduction state, and isolation between elements is not achieved. There was a possible drawback. Therefore, in order to reduce the amount of holes generated in the silicon oxide films 2 and 3, it is considered to thin the silicon oxide film. In the case of the element isolation silicon oxide film 3, there are drawbacks that the capacitance between the wiring 4 and the semiconductor substrate 1 increases, the operating speed decreases, and the electrical isolation decreases. Further, in the case of the silicon oxide film 2 as the surface protection film of the bipolar transistor, the silicon oxide film is used as a mask of the doping material when the base 6 or the emitter 5 is formed. It is mainly determined from the viewpoint of the effect as a mask, and the transistor having a deeper junction has a larger silicon oxide film thickness. Therefore, in order to reduce the thickness of the silicon oxide film, a conventional method is to remove the silicon oxide film 2 on the active region of the transistor and then re-form it to a film thickness of 20 nm or less. Since the surface is exposed, there is a drawback that a leak current is generated due to contamination of the surface.

(Means for Solving Problems) The present invention has been proposed in order to improve the above-mentioned drawbacks, and an object of the present invention is to provide a semiconductor device in which specific deterioration is reduced even in a radiation environment. .

In order to achieve the above object, the present invention provides a semiconductor device having a bipolar transistor which protects a semiconductor surface with a silicon oxide film, in a semiconductor device having at least a junction with an emitter base and a junction with a base collector. The gist of the invention is a semiconductor device characterized in that the thickness of a silicon oxide film formed in the vicinity thereof is 20 nm or less.

Further, according to the present invention, in a semiconductor device in which an element isolation is performed by a silicon oxide film, it is formed near a junction between an element surrounded by an element isolation silicon oxide film and the element isolation silicon oxide film. The gist of the invention is a semiconductor device characterized in that the thickness of the formed silicon oxide film is 20 nm or less.

Next, examples of the present invention will be described. It is needless to say that the embodiment is merely an example, and various modifications and improvements can be made without departing from the spirit of the present invention.

Next, examples will be described.

FIG. 1 shows an embodiment of the present invention, in which 11 is a semiconductor substrate, 12, 22 and 13 are silicon oxide films, 14 is a wiring metal, 15 is an emitter region, 16 is a base region, 1
7 is a collector region. In the present invention, the silicon oxide film 22 near the junction between the emitter region 15 and the base region 16, the silicon oxide film 22 near the junction between the base region 16 and the collector region 17, and the junction between the collector region 17 and the semiconductor substrate 11. Of the silicon oxide film 22 formed near the junction between the element surrounded by the silicon oxide film 22 and the element isolation silicon oxide film 13 and the element isolation silicon oxide film 13 described above. The feature is that the thickness is 20 nm or less. This reduces the effect of radiation irradiation. In this case, when the thickness of the silicon oxide film exceeds 20 nm, the direct current amplification factor is remarkably lowered by the irradiation of radiation. If the oxide film has a thickness of 5 nm or less, the effect of protecting the semiconductor device is small.

Next, a method of manufacturing the device of the present invention will be described.

Figure 1 (a) before contact window formation by conventional manufacturing process
Up to this is the same as the conventional method, but in the present invention, FIG. 1 (c)
There are two methods for forming the silicon oxide film 22, as shown in FIG. In the first method, an etching apparatus having a known ethylate is used to leave 12 silicon oxide films,
Etching only the region where a thin oxide film of m or less is formed, as shown in FIG. 2 (c), or as shown in FIG. 2 (b), a region of a thin silicon oxide film of 20 nm or less is formed. The silicon oxide film is completely removed, leaving only 12 parts, and then a second layer is formed by a method such as thermal oxidation or chemical vapor deposition.
A silicon oxide film 22 is formed as shown in FIG.

FIG. 2 (d) shows that after the manufacturing process of the present invention is applied, the contact window is opened and the wiring 14 is formed.

When the present invention is implemented in this way, the silicon oxide film is
Since it is as thin as m or less, it has high resistance to radiation, and since the silicon oxide film is not completely removed, there is an advantage that a leak current due to surface contamination or the like is unlikely to occur.

(Advantages of the Invention) As described above, according to the present invention, in a semiconductor device, by reducing the thickness of the silicon oxide film on the surface side of the device to 20 nm or less, deterioration of characteristics of the semiconductor device due to radiation irradiation is reduced. There are advantages.

Furthermore, there is no need to make drastic changes in the manufacturing process, which is beneficial from the viewpoint of manufacturing.

[Brief description of drawings]

FIG. 1 is a sectional view of an embodiment of the present invention, and FIG. 2 is a sectional view of a conventional semiconductor device. 1, 11 ... Semiconductor substrate, 2, 12, 22 ... Silicon oxide film, 3, 13 ... Silicon oxide film for element isolation,
4, 14 ... Wiring, 5, 15 ... Emitter area, 6, 1
6 ... Base region, 7, 17 ... Collector region, 8, 1
8: Bonding appearing on the surface of the semiconductor substrate

Claims (2)

[Claims] 1. A semiconductor device having a bipolar transistor for protecting a semiconductor surface with a silicon oxide film, the semiconductor device being formed at least near a junction between an emitter and a base and a junction between a base and a collector. A semiconductor device characterized in that the thickness of the silicon oxide film is 20 nm or less. 2. A semiconductor device in which elements are separated by a silicon oxide film, in the vicinity of a junction between an element surrounded by the element isolation silicon oxide film and the element isolation silicon oxide film. A semiconductor device, wherein the thickness of the formed silicon oxide film is 20 nm or less.