KR100277871B1 - Separator Formation Method - Google Patents

Abstract

The present invention relates to a method of forming a separator for improving the electrical characteristics of a high voltage or high current device because it prevents the concentration change in the drift layer or high concentration well when forming the separator.

The isolation layer forming method of the present invention comprises a first conductivity type epitaxial layer including first and second conductivity type wells and first and second conductivity type drift layers and a buried insulation layer, and an isolation region is defined. Forming a first insulating film on the SOI substrate, and selectively etching the first insulating film, the first and second conductive wells, and the highly concentrated first and second conductive wells in the isolation region. Forming first and second trenches in which the first insulating film is exposed; growing a second insulating film on sidewalls of the first and second trenches by heat treatment of the entire surface including the first insulating film; and the first and second trenches. Forming a third insulating film and a conductor on the entire surface to fill the trench, forming a fourth insulating film on the conductor, removing the fourth insulating film, the conductor, the third insulating film, and the first insulating film on the SOI substrate. Including the steps It features.

Description

Separator Formation Method

The present invention relates to a method of forming a separator, and more particularly, to a method of forming a separator for improving the electrical characteristics of the device.

1A to 1F are cross-sectional views showing a conventional method of forming a separator.

A conventional isolation film formation method using a silicon on insulator (SOI) wafer in the manufacture of high voltage and high power devices is a high density n-type substrate 11a and a burried oxide film 11b having a thickness of 1 to 3 μm as shown in FIG. P-type well 12, n-type well 13, n-type drifting layer 14, p-type drifting layer 15, high-density p-type well 16, and high-concentration n-type well 17 ), An SOI substrate 11 composed of a p-type epitaxial layer 11c having an isolation region and defining an isolation region is prepared.

Here, the p-type well 12 is formed in a predetermined region in the surface of the p-type epitaxial layer 11c by general photosensitive etching processes, ion implantation processes, and drive-in diffusion processes. The n-type well 13 is formed in the surface of the p-type epitaxial layer 11c on one side of the p-type well 12.

The n-type drifting layer 14 is formed in a predetermined region in the surface of the p-type well 12, the p-type drifting layer 15 is formed in a predetermined region in the surface of the n-type well 13 and the high concentration The p-type well 16 is formed in the surface of the p-type well 12 on one side of the n-type drifting layer 14, and the high concentration n-type well 17 is an n-type well on one side of the p-type drifting layer 15. (13) It is formed in the surface.

Then, a first oxide film 18 having a thickness of 9000 to 11000 kPa is formed on the SOI substrate 11.

As shown in FIG. 1B, after the photoresist film 19 is coated on the first oxide film 18, the photoresist film 19 is selectively etched to remove only the isolation region, and the selected photo etched photoresist 19 is then removed. ) Is selectively etched using the first oxide film 18 as a mask.

As shown in FIG. 1C, the p-type well 12, the n-type well 13, the high concentration p-type well 16, and the high concentration are removed by using the photoresist film 19 as a mask. The n-type well 17 is selectively etched to form first and second trenches in which the buried oxide film 11b is exposed.

As shown in FIG. 1D, after removing the first oxide film 18, a second oxide film 20 having a thickness of 900 to 1100 μs is grown on the entire surface except the exposed buried oxide film 11b by a thermal oxidation process on the entire surface. Next, on the second oxide film 20, a third oxide film 21 having a thickness of 2900 to 3100 kW is formed by a high temperature low deposition (HLD) process.

A polycrystalline silicon 22 is formed on the third oxide film 21 by a filling process, and a planarization spin on glass (SOG) layer 23 is formed on the polycrystalline silicon 22.

As illustrated in FIG. 1E, the SOG layer 23, the polycrystalline silicon 22, the third oxide film 21, and the second oxide film 20 are etched back through the entire planarization process.

Here, in order to prevent the SOI substrate 11 from being excessively etched during the etch back process, the second oxide film 20 of 200 to 800 Å remains.

As shown in FIG. 1F, the remaining second oxide film 20 is removed.

However, in the conventional isolation layer formation method, since the thermal oxide film is grown after forming the first and second trenches and removing the remaining first oxide film, the exposed drifting layer or the dopants of the well-concentrated well escapes, so the drifting layer However, the electrical characteristics of the high-voltage or high-current device due to the change in concentration in the high concentration well region are inhibited. In particular, when the average concentration of the p-type drift layer decreases, the breakdown voltage of the device decreases.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and therefore, an object of the present invention is to provide a method of forming a separator that improves electrical characteristics of a high voltage or high current device because it prevents concentration changes in a drifting layer or a high concentration well when forming a separator.

1A to 1F are cross-sectional views illustrating a conventional method of forming a separator.

2A to 2F are cross-sectional views illustrating a method of forming a separator according to an embodiment of the present invention.

Explanation of symbols for main parts of the drawings

31: SOI substrate 31a: High concentration n-type substrate

31b: Buried oxide film 31c: p-type epitaxial layer

32: p-type well 33: n-type well

34: n-type drifting layer 35: p-type drifting layer

36: high concentration p-type well 37: high concentration n-type well

38: first oxide film 39: photosensitive film

40: second oxide film 41: third oxide film

42: polycrystalline silicon 43: SOG layer

The isolation layer forming method of the present invention comprises a first conductivity type epitaxial layer including first and second conductivity type wells and first and second conductivity type drift layers and a buried insulation layer, and an isolation region is defined. Forming a first insulating film on the SOI substrate, and selectively etching the first insulating film, the first and second conductive wells, and the highly concentrated first and second conductive wells in the isolation region. Forming first and second trenches in which the first insulating film is exposed; growing a second insulating film on sidewalls of the first and second trenches by heat treatment of the entire surface including the first insulating film; and the first and second trenches. Forming a third insulating film and a conductor on the entire surface to fill the trench, forming a fourth insulating film on the conductor, removing the fourth insulating film, the conductor, the third insulating film, and the first insulating film on the SOI substrate. Including the steps It features.

When described in detail with reference to the accompanying drawings a preferred embodiment of the separator according to the present invention as follows.

2A to 2F are cross-sectional views illustrating a method of forming a separator according to an embodiment of the present invention.

The isolation layer forming method according to the embodiment of the present invention using the SOI wafer in the manufacture of high voltage and high power devices, as shown in Figure 2a, a high concentration n-type substrate 31a and a buried oxide film 31b having a thickness of 1 ~ 3㎛ and p P-type epi, in which the well type 32, the n type well 33, the n type drifting layer 34, the p type drifting layer 35, the high concentration p type well 36, and the high concentration n type well 37 are formed. An SOI substrate 31 composed of a tactile layer 31c and defined as an isolation region is prepared.

Here, the p-type well 32 is formed in a predetermined region in the surface of the p-type epitaxial layer 31c by a general photosensitive etching process, ion implantation processes, and drive-in diffusion processes of the photoresist layer. The n-type well 33 is formed in the surface of the p-type epitaxial layer 31c on one side of the p-type well 32.

The n-type drifting layer 34 is formed in a predetermined region in the surface of the p-type well 32, the p-type drifting layer 35 is formed in a predetermined region in the surface of the n-type well 33 and the high concentration The p-type well 36 is formed in the surface of the p-type well 32 on one side of the n-type drifting layer 34, and the high concentration n-type well 37 is an n-type well on one side of the p-type drifting layer 35. (33) It is formed in the surface.

A first oxide film 38 having a thickness of 9000 to 11000 kPa is formed on the SOI substrate 31.

As shown in FIG. 2B, after the photoresist 39 is applied onto the first oxide layer 38, the photoresist 39 is selectively etched to remove only the isolation region, and the selected photo etched photoresist 39 is then removed. ), The first oxide film 38 is selectively etched using a mask.

As shown in FIG. 2C, the p-type well 32, the n-type well 33, and the high-concentration p-type well 36 are removed using the exposed first oxide layer 38 as a mask. The high concentration n-type well 37 is selectively etched to form first and second trenches in which the buried oxide layer 31b is exposed.

As shown in FIG. 2D, a second oxide film 40 having a thickness of 900 to 1100 μs is grown on sidewalls of the first and second trenches by a thermal oxidation process on the entire surface, and then the first and second oxide films 38 and 40 are formed. On the HLD process, a third oxide film 41 having a thickness of 2900 to 3100 Å is formed.

Then, polycrystalline silicon 42 is formed on the third oxide film 41 by a peeling process, and a planarization SOG layer 43 is formed on the polycrystalline silicon 42.

As shown in FIG. 2E, the SOG layer 43, the polycrystalline silicon 42, the third oxide film 41, the second oxide film 40, and the first oxide film 38 are etched back in the planarization process of the entire surface.

Here, in order to prevent the SOI substrate 31 from being excessively etched during the etch back process, the first oxide film 38 having the thickness of 200 to 800 Å is left.

As shown in FIG. 2F, the remaining first oxide layer 38 is removed by a wet etching process.

The isolation film forming method of the present invention forms the first and second trenches and grows the thermal oxide film in the state where the first oxide film remains, so that the dopants of the drifting layer or the highly well-concentrated well do not escape by the protective film of the first oxide film. Since the concentration change in the layer or the high concentration well is prevented and the breakdown voltage of the device is prevented from being lowered, there is an effect of improving the electrical characteristics of the high voltage or high current device.

Claims (4)

Providing an SOI substrate comprising a first conductive type epitaxial layer including a first conductive type well and a first conductive type drifting layer and a buried insulating film, the isolation region being defined; Forming a first insulating film on the SOI substrate; Selectively etching the first insulating film, the first and second conductive wells, and the highly concentrated first and second conductive wells in the isolation region to form first and second trenches in which the buried insulating film is exposed; Growing a second insulating film on sidewalls of the first and second trenches by heat treatment of the entire surface including the first insulating film; Forming a third insulating film and a conductor on the entire surface of the first and second trenches and forming a fourth insulating film on the conductor; And removing the fourth insulating film, the conductor, the third insulating film, and the first insulating film on the SOI substrate. The method of claim 1, And the first insulating film is formed of a first oxide film having a thickness of 9000 to 11000 kPa. The method of claim 1, And the second insulating film is grown into a second oxide film having a thickness of 900 to 1100 Å. The method of claim 1, And the third insulating film is formed of a third oxide film having a thickness of 2900 to 3100 kPa.