JPH06283599A - Semiconductor device and its manufacture - Google Patents

Abstract

PURPOSE:To reduce the gradient of a step-difference between active field regions, by constituting the side wall of a shield gate electrode as a slant form. CONSTITUTION:After impurities are introduced into a poly silicon film 4, an insulating film is formed by growing a silicon dioxide film 5 of 50-200nm in thickness by a CVD method. Photoresist 6 is spread and patterned. A dry etching method is used, the flow rate of etchant gas is changed, step-etching is performed, and the silicon dioxide film 5 and the poly silicon film 4 are worked into a structure having a slant on the side wall. Hence the poly silicon film 4 is worked into the form of a shield gate electrode. Thereby imperfect gate electrode wiring caused by the step-difference between active field regions can be restrained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor device and a method of manufacturing the same, and more particularly, to a semiconductor device having a high performance and highly reliable element isolation structure in a highly integrated and fine device and a method of manufacturing the same. Regarding

[0002]

2. Description of the Related Art A conventional element isolation technique called the field shield method is described in a paper (Fully planarized 0.5 μm tech
nologies for 16 Mb DRAM IEDM-88 p.246 ~), the field shield electrode is formed,
This is an effective method for cutting off the potential of the parasitic MOS transistor by fixing the potential of the electrode to GND or Vcc, and the active interval can be shortened.
Suitable for miniaturization of semiconductor devices.

The manufacturing process will be described in order. First, a field shield gate oxide film having a film thickness of 50 n is formed on a silicon substrate.
After the film formation to m, boron ions are introduced into the film by ion implantation under the condition of 1E12ions / cm ² for adjusting the threshold value of the transistor in the active region and the parasitic MOS transistor in the field region. After that, a field shield plate electrode is formed with phosphorus-doped polysilicon to a film thickness of 200 nm, and an interlayer insulating film and a gate oxide film and a gate electrode of the active transistor are formed.

[0004]

Conventionally, when the field shield method is used as the element isolation method as described above,
There is a problem that the step between the active region and the field region becomes steep, and due to this step, the wiring that becomes the gate electrode of the active transistor is apt to cause a defect due to a short circuit, and as a result, the reliability of the semiconductor device is deteriorated. It was

Therefore, the present invention provides a semiconductor device capable of improving the reliability of the gate wiring of an active transistor by reducing the gradient of the step between the active field regions, and a manufacturing method thereof. With the goal.

[0006]

According to the present invention, in order to solve the above problems, in the semiconductor device of the present invention, the side surface of the shield plate electrode is formed in an inclined shape. As a manufacturing method thereof, a step of forming an insulating film on the surface of a semiconductor substrate, a step of introducing impurities into the substrate through the film, and forming a polysilicon thin film on the insulating film A step of introducing impurities into the film, a step of forming the polysilicon thin film into an electrode having a sidewall inclined by step etching by a dry etching method, or a photoresist coated on the polysilicon film. After the photolithography method is used to form the sidewall with an inclination, a step of forming the polysilicon film into an electrode having an inclination on the sidewall by a dry etching method and then a step of covering the polysilicon electrode with an insulating film are performed. Good to do.

[0007]

With the above-described means, the side wall of the shield gate electrode is formed into an inclined shape, whereby the gradient of the step difference between the active field regions can be reduced. Therefore, it is possible to prevent a defect such as a disconnection of the gate electrode wiring of the active transistor formed on the field and a short circuit due to an etching residue, which is likely to occur due to the step, and to improve reliability and yield of the semiconductor integrated circuit. .

[0008]

Embodiments of the present invention will be described below in the order of steps with reference to the sectional views shown in FIGS.

As shown in FIG. 1, a field shield gate oxide film (silicon dioxide film) 2 having a film thickness of 50 is formed on a semiconductor silicon substrate 1 (containing a specific resistance of 1 to 12 Ω · cm boron) by a known thermal oxidation method. After forming to 100 nm, the boron ions 3 are used as energy 3 to adjust the threshold values of the active transistor and the parasitic MOS transistor.
Implantation of impurities is performed under the conditions of 0 to 100 keV and a dose amount of 1E to 5E12 ions / cm ² .

As shown in FIG. 2, 2E2 was added to phosphorus ions.
A polysilicon film (shield plate electrode) 4 containing about 0 to 6E20 atoms / cm ³ having a film thickness of 100 to 200 nm
To a thickness of about 50 to 200 nm by a known CVD method after the impurities are introduced into the polysilicon film 4 to improve the conductivity. An insulating film is formed. After that, the photoresist 6 is applied, and the photoresist 6 is patterned by using a known photolithography technique.

After that, by using a known dry etching method, the etchant gas flow rate and the like are changed and step etching is performed, and as shown in FIG. Processed into a structure with. Through the above processing, the polysilicon film 4 is processed into the shape of the shield gate electrode.

Further, after coating the photoresist 6 on the silicon dioxide film 5 on the polysilicon film 4, the exposure condition and the developing condition are changed by using a known photolithography method, as shown in FIG. The photoresist 6a to be patterned is formed into a shape having a side wall with an inclination. After that, by using a known anisotropic dry etching method, the polysilicon film 4 can be processed into a structure having an inclined sidewall.

After that, a silicon dioxide film is formed again by a known CVD method, and then the above-mentioned silicon dioxide film is etched by using a known anisotropic etching method to form sidewalls as shown in FIG. Form the wall 7.

In each of the above embodiments, after the silicon dioxide film 5 is formed on the polysilicon film 4, the photoresist 6 and 6a are applied on the silicon dioxide film 5 for etching. Photoresists 6 and 6a are applied on the silicon film 4 and etched to process the sidewalls of the polysilicon film 4 into an inclined shape, and then a silicon dioxide film is formed. The silicon dioxide film 5 and the side wall wall 7 may be formed.

Then, again, as shown in FIG. 6, the gate oxide film 8 of the active transistor is formed to a film thickness of 10 to 50 nm by a known thermal oxidation method, and then phosphorus or arsenic is added to 2E20 to 6E20 atoms / cm 2. Known CV with a film thickness of 100 to 400 nm containing polysilicon containing about ³
A film is formed by the D method, and the polysilicon thin film is patterned by a known fine processing method to form the gate electrode 9.

After that, the source / drain diffusion layer 10 is formed in a self-selective manner by a known ion implantation method. The surface concentration of the source / drain contains 1E19 to 1E21 atoms / cm ³ of arsenic or phosphorus impurities, and the junction depth is about 0.2 to 0.3 μm.

Thereafter, as shown in FIG. 7, a device is manufactured by forming an annealed interlayer insulating film 11 of a diffusion layer, forming a contact hole, forming a metal wiring 12, and the like.

[0018]

As described above, according to the present invention,
By forming the shield plate electrode into a shape having an inclined sidewall, it is possible to suppress defects in the gate electrode wiring caused by a step between the active field regions,
The yield of semiconductor devices can be improved.

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional view showing a manufacturing process of a semiconductor device to which the present invention is applied.

FIG. 2 is a schematic cross-sectional view subsequent to FIG. 1 showing a manufacturing process of a semiconductor device.

FIG. 3 is a schematic cross-sectional view subsequent to FIG. 2 showing a manufacturing process of a semiconductor device.

FIG. 4 is a schematic cross-sectional view showing another embodiment following FIG. 1 showing the manufacturing process of the semiconductor device.

FIG. 5 is a schematic cross-sectional view showing the manufacturing process of the semiconductor device, following FIG. 3;

FIG. 6 is a schematic cross-sectional view showing the manufacturing process of the semiconductor device, following FIG. 5;

7 is a schematic cross-sectional view following FIG. 6 showing one embodiment of a semiconductor device.

[Explanation of symbols]

 1 semiconductor silicon substrate 2 shield gate oxide film 3 ion implantation 4 polysilicon film 5 silicon dioxide film 6 ・ 6a photoresist 7 silicon dioxide film 8 gate oxide film 9 gate electrode 10 source / drain diffusion layer 11 interlayer insulating film 12 metal wiring

Claims (5)

[Claims] 1. A semiconductor device characterized in that an insulating film, a shield plate electrode, and an insulating film are sequentially formed on a surface of a silicon substrate, and the shield plate electrode is fixed at a constant potential for element isolation. A semiconductor device in which the side wall of the shield plate electrode is inclined. 2. A step of forming an insulating film of silicon dioxide on the surface of a silicon substrate, a step of introducing impurities into the substrate through the insulating film, and a poly that will become a shield plate electrode on the insulating film. A step of forming a silicon film,
Forming a shield plate electrode by inclining the side wall of the polysilicon film. 3. The method according to claim 2, wherein the polysilicon film is covered with an insulating film of silicon dioxide, and then the sidewalls of the insulating film and the polysilicon film are processed to have a sloped shape. Manufacturing method of semiconductor device. 4. The method according to claim 2, further comprising a step of performing step etching on the polysilicon film by using a dry etching method to process the electrode into a shape in which a side wall thereof is inclined. A method of manufacturing a semiconductor device according to item 1. 5. A step of processing a photoresist using a photolithography method when processing the polysilicon film, and processing the sidewall of the photoresist into a slanted shape, and then a dry etching method to process the polysilicon film. 4. The method for manufacturing a semiconductor device according to claim 2, further comprising the step of: processing the electrode into an electrode whose side wall is inclined.