KR0156125B1 - Semiconductor device manufacturing method - Google Patents

Abstract

The present invention relates to a bipolar oxide isolation (Bipolar Oxide Isolation) process, in particular to achieve a perfect device isolation (acti-ve) depth by performing two-step oxidation using an epitaxial lateral overgrowth (ELO) process The present invention relates to a semiconductor manufacturing method which has a stable device characteristic by preventing a decrease in depth.

In order to achieve the object of the present invention, a first step of selectively implanting ions onto a first conductive substrate to form a high concentration second conductive impurity region, and isolation of device regions on the substrates on both sides of the high concentration second conductive impurity region A second step of forming a first thermal oxide film for forming the first thermal oxide film, a third step of forming a low concentration second conductive epitaxial layer on the entire surface of the substrate, and a second low concentration of a portion except the upper portion of the high concentration first conductive type impurity region A fourth step of selectively etching a conductive epitaxial layer so that the first thermal oxide layer is not exposed, and a fifth step of thermally oxidizing the low concentration second conductive epitaxial layer of the etched portion to form a second thermal oxide layer Characterized in that comprises a.

Description

Semiconductor device manufacturing method

1 is a cross-sectional view of a conventional bipolar oxide isolation process.

2 is a cross-sectional view of the bipolar oxide isolation process of the present invention.

* Explanation of symbols for main parts of the drawings

21 substrate 22, 24 first and second insulating films

23a: N ⁺ impurity diffusion region 23b: N type buried layer

25: N-type epitaxy layer 26: oxide isolation

The present invention relates to a bipolar oxide isolation (Bipolar Oxide Isolation) process, and in particular, complete device isolation by performing two-step oxidation using an ELO (Epitaxial Lateral Overgrowth) process. The present invention relates to a method of manufacturing a semiconductor device, which has stable device characteristics by preventing the decrease in active depth.

Conventional bipolar oxide isolation manufacturing method is described with reference to the accompanying drawings as follows.

FIG. 1 is a cross-sectional view of a conventional bipolar oxide isolation manufacturing process, in which a first insulating film 2 is formed on a p-type substrate 1 and exposed on the first insulating film 2 as shown in FIG. And selectively defining an impurity diffusion region by an etching process, and then implanting a high concentration (N ⁺ ) impurity ion into the impurity diffusion region to form an N-type impurity region 3.

Subsequently, as shown in FIG. 1 (b), the first insulating layer is removed, and then a low concentration N-type epitaxy (N-type Ep-itaxy: hereinafter referred to as N-Epi) layer 4 is grown.

At this time, an N-type buried layer (hereinafter abbreviated as NBL) 5 is formed.

As shown in FIG. 1C, a second insulating film (oxide film: SiO ₂ ) 6 and a third insulating film (nitride film: SiN ₄ ) 7 are sequentially deposited on the N-type epitaxy ₄ , and After defining the area where the isolation is to be formed by the exposure and etching processes on the entire surface, thermal oxidation is performed on the entire surface as shown in FIG. 1 (d), and the third insulating layer 7a is removed to remove the first layer ( oxide is isolated 8 as in e). Referring to Figure 1 (e) in detail as follows.

The active A and B are completely isolated by the NBL's contact with oxide isolation (dotted line).

At this time, since the depth of the NBL is about 4 μm, the side diffraction is caused by the side diffusion factor (depth * 0.8) in FIG. This makes it difficult to achieve full isolation.

To prevent this, the NBL is defined inside the isolation process in consideration of the side deflection of the NBL.

In this case, for example, when the NBL depth is not sufficient or the thermal oxidation thickness is not sufficient, the isolation between the devices A and B does not occur like the solid line display.

Therefore, if the device and device characteristics are problematic, and if the NBL side deflection is not considered, the NBL side deflection must have a wide design rule for complete isolation, thereby increasing the chip area.

Finally, since the amount of NBL-UP is increased at the same time as the oxidation is progressed by performing thermal oxidation at a time, the device breakdown characteristic is deteriorated.

SUMMARY OF THE INVENTION The present invention has been made to solve the problems of the prior art, and seeks perfect device isolation by performing two-step oxidation using an ELO process and prevents the active depth from being reduced, thereby achieving stable device characteristics. Its purpose is to have it.

Referring to the bipolar oxide isolation process of the present invention for achieving the above object in detail as shown in FIG.

As shown in FIG. 2A, a first insulating layer 22 is formed on the p-type substrate 21 to selectively define the impurity diffusion region by exposing and etching the first insulating layer 22. High concentration (N ⁺ ) impurities are implanted into the impurity diffusion region to form an N ⁺ type impurity diffusion region 23a.

Subsequently, as illustrated in FIG. 2B, the first nitride film is removed, and then a second insulating film (oxide SiO ₂ ) and a third insulating film (nitride film SiN ₄ ) are sequentially deposited on the entire surface.

The first thermal oxidation is performed after defining a region where the first isolation is to be formed by an exposure and etching process on the entire surface.

In this case, the second insulating layer is formed of a blocking second insulating layer 24 that prevents the NBL side difference, and an N-type buried layer 23b is formed.

After removing the third insulating layer as shown in FIG. 2 (c), a low concentration N-type epitaxy layer 24 is g-rowed by using an epitaxial lateral overgrowth (ELO) process. Let's do it.

At this time, the N-Epi growth mechanism (mechanism), N-Epi does not grow on the oxide (oxide) only grows up and grows in the lateral direction (overg-rowth) in the second degree (d) As in N-Epi layer coalescing (coalescence) (25).

The N-Epi layer is planarized 25 as shown in FIG. 2 (e), and the fourth insulating film (oxide film: SiO ₂ ) is formed on the planarized front surface as shown in FIG. A fifth insulating film (nitride film: SiN ₄ ) is deposited in sequence.

After the selective etching process is performed such that the fourth insulating layer and the fifth insulating layer remain only above the N-type buried layer 23b, that is, removed only in the isolation region, the N-Epi layer 25 is formed using the fifth insulating layer as a mask. Selective etching is performed so that the breaking second insulating layer 24 is not exposed.

Thereafter, as shown in FIG. 2 (g), second thermal oxidation is performed on the entire surface to contact the first isolation to form an oxide isolation 26.

At this time, since thermal oxidation has a smaller thickness of thermal oxidation than in the related art, the amount of NBL-UP during the oxidation process is reduced, so that the thermal oxidation voltage can have a high breakdown voltage and thus have much more stable device characteristics.

In addition, as shown in FIG. 2D, the NBL defined as the active region is completely blocked on the oxide surface, so that the devices C and D are reliably isolated as in FIG. 2H.

The bipolar oxide isolation method of the present invention as described above has the following effects.

First, NBL, which is defined as an active region, is completely blocked on the oxide surface, thereby forming a reliable isolation between the device and the device.

Second, by performing two-step oxidation, it is possible to increase breakdown voltage by increasing NBL-UP smaller than the amount of NBL-UP by conventional one-step oxidation. Characteristics can be obtained.

Claims (1)

Forming a high concentration second conductive impurity region by selectively ion implanting onto the first conductive substrate, and forming a first thermal oxide film for isolating the device region on the substrates on both sides of the high concentration second conductive impurity region A second process, a third process of forming a low concentration second conductive epitaxial layer on the entire surface of the substrate, and the low concentration second conductive epitaxial layer in a portion except the upper portion of the high concentration first conductivity type impurity region; And a fourth step of selectively etching such that the first thermal oxide film is not exposed, and a fifth step of thermally oxidizing the low-concentration second conductive epitaxial layer of the etched portion to form a second thermal oxide film. Semiconductor device manufacturing method.