JPH06296024A - Semiconductor device and manufacture thereof - Google Patents

Abstract

PURPOSE:To remove a silicon nitride film without damaging a substrate by a method wherein a silicon oxide film being an insulation film between first polycrystalline silicon formed in a region to be made a drive element of a semiconductor storage element and second polycrystalline silicon and the silicon nitride film are formed before the first polycrystalline silicon is etched. CONSTITUTION:A field insulation film 102 and a first insulation film 103 are formed on a substrate 101. A first polycrystalline silicon film 104 is formed on these first insulation film 103 and the field insulation film 102. Moreover, a first silicon oxide film 105 and a second silicon nitride film 105 are formed on this first polycrystalline silicon film 104. Then, unnecessary parts of the first insulation film 103, the first silicon oxide film 105 and the second silicon nitride film 106 are removed together with the one of the first polycrystalline silicon film 104 by etching. According to this constitution, the first polycrystalline silicon film 104 and the first silicon oxide film 105 can be removed by one time etching without damaging the substrate 101.

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 more particularly to a manufacturing apparatus and a manufacturing method for a semiconductor memory element and its driving element.

[0002]

2. Description of the Related Art A conventional method for manufacturing a semiconductor memory device is as shown in FIGS. 2 (a) to 2 (h). This process will be described step by step.

First, a semiconductor substrate 201 as shown in FIG.
A first silicon nitride film is formed on the top surface of the first silicon nitride film. Then, a thermal oxidation method is performed to form the field insulating film 202. The field insulating film 202 is formed to a thickness of 600 nm to 800 nm. The first silicon nitride film is removed, and a first insulating film 203 is formed on the semiconductor substrate 201 by a thermal oxidation method. For example, it is oxidized in a dry atmosphere having an oxygen concentration of 40% at 1000 degrees. The first insulating film 203 is an EPR
30 nm to 50 nm is suitable for OM, and about 10 nm is suitable for EEPROM. The first insulating film 203 is used as a gate insulating film of a semiconductor memory device.

Next, as shown in FIG. 2B, a first polycrystalline silicon film 204 of about 200 nm is formed on the field insulating film 202 and the first insulating film 203 by the CVD method. Usually, monosilane gas is thermally decomposed at around 620 ° C. to deposit the first polycrystalline silicon 204. Then, in order to reduce the resistance of the first polycrystalline silicon film 204, for example, a Group 5 element (for example, a conductive impurity such as phosphorus element or arsenic) is ion-implanted to 1 ×.
Implantation is performed from 10 ¹⁵ to about 1 × 10 ¹⁶ atoms · cm ⁻² .

Next, as shown in FIG. 2C, unnecessary portions of the first polycrystalline silicon film 204 and the first insulating film 203 are removed by photo and etching methods.

Next, as shown in FIG. 2D, the first polycrystalline silicon 204 and the semiconductor substrate 201 are formed by a thermal oxidation method.
A first silicon oxide film 205 is formed on top. For example, 1
Oxidation is performed in a dry atmosphere having an oxygen concentration of about 40% at 000 ° C. to form a silicon oxide film of about 10 nm on the first polycrystalline silicon film 204. Then, a second silicon nitride film 206 is formed on the first silicon oxide film 205 and the field insulating film by chemical vapor deposition to a thickness of about 10 n.
Form about m.

Next, as shown in FIG. 2 (e), the first silicon nitride film 206 in the region to be the driving element of the semiconductor memory element is removed by photo and etching methods. Then, the first silicon oxide film 205 in the region to be the driving element of the semiconductor memory element is removed by photo and etching methods.

Next, as shown in FIG. 2 (f), by a thermal oxidation method,
A second silicon oxide film 207 is formed on the first silicon nitride film 206, and a third silicon oxide film 207 is formed on the semiconductor substrate 201. For example, the oxidation is performed in a dry atmosphere at an oxygen concentration of about 40% at 1000 ° C.
Silicon oxide 207 is formed to a thickness of about 3 nm.

Next, as shown in FIG. 2G, a second polycrystalline silicon film 209 is formed on the field insulating film 202 and the second polycrystalline silicon film 209.
Silicon oxide film 207 and the third silicon oxide film 20
A film having a thickness of about 300 nm is formed on the surface 8 by chemical vapor deposition.
Then, an impurity such as phosphorus or arsenic is implanted into the second polycrystalline silicon film 208 by using an ion implantation method to make it a conductor. For example, a group 5 element (for example, a conductive impurity such as phosphorus element or arsenic) is ion-implanted to obtain 1 × 10 5.
Implant about ¹⁵ to 1 × 10 ¹⁶ atoms · cm ⁻² .

Next, as shown in FIG. 2H, an unnecessary portion of the second polycrystalline silicon 209 on the third silicon oxide film 208 is removed by a photo and etching method. This becomes the gate electrode of the transistor (driving element of the semiconductor memory element) of the peripheral circuit. Then, the second polycrystalline silicon 209, the second silicon oxide film 207, and the second silicon nitride film 2 are formed by a photo and etching method.
06, the first silicon oxide film 205, and unnecessary portions of the first polycrystalline silicon 204 are removed. This becomes the gate electrode of the semiconductor memory element.

Finally, an ion implantation method is used to implant impurities such as phosphorus and arsenic to source 21 of the semiconductor memory device.
0 and drain 211, source 212 and drain 213 of the transistor of the peripheral circuit are formed.

The above steps are the conventional semiconductor device and the manufacturing method thereof.

[0013]

However, according to the above-mentioned conventional technique, when the first silicon nitride film 206 in the region to be the driving element of the semiconductor memory element is removed by the etching method, the first silicon oxide film 205 is removed. Since the thickness is about 5 nm, the semiconductor substrate 201 is also etched. As a result, the defect density of the gate oxide film of the drive element of the semiconductor memory element increases, the breakdown voltage decreases, and the threshold voltage of the drive element of the semiconductor memory element varies. In addition, two photo and etching processes are performed to remove the first polycrystalline silicon 204, the first silicon oxide film 205, and the second silicon nitride film formed in the region to be the driving element of the semiconductor memory device. This is necessary and causes a problem of increasing the number of manufacturing steps. Therefore, the present invention solves such problems.
The purpose is to remove the silicon nitride film formed in the region to be the driving element of the semiconductor memory element without damaging the semiconductor substrate in the region to be the driving element of the semiconductor memory element, and to reduce the number of manufacturing steps. It is an object of the present invention to provide a method of manufacturing a semiconductor device that can be significantly reduced.

[0014]

A method of manufacturing a semiconductor device according to the present invention has a MOS type transistor structure having a floating gate and a control gate, and is dependent on how the charge is injected into the floating gate.
In a method of manufacturing a semiconductor device in which a control threshold voltage of a characteristic of the MOS transistor of the control gate changes, a step of forming a field insulating film on a semiconductor substrate, and a step of forming a first insulating film on the semiconductor substrate ,
Forming a conductor layer on the first insulating film and the field insulating film, forming a first silicon oxide film on the conductor layer, forming a silicon nitride film on the first silicon oxide film, It is characterized in that it comprises a step of removing the silicon nitride film, the first silicon oxide film and the conductor layer so as to remain in the region where the MOS transistor is formed.

[0015]

1 (a) to 1 (f) are main cross-sectional views of respective steps of a method of manufacturing a semiconductor device according to an embodiment of the present invention. In all the drawings of the embodiments, those having the same function are designated by the same reference numeral, and the repeated description thereof will be omitted. Hereinafter, description will be made in order according to FIGS. 1A to 1F.

First, a semiconductor substrate 101 as shown in FIG.
A silicon nitride film is formed in a predetermined shape on the top. Then, thermal oxidation is performed to form the field insulating film 102. The field insulating film 102 is formed to have a thickness of 600 nm to 800 nm. The nitride film is removed, and a first insulating film 103 is formed on the semiconductor substrate 101 by a thermal oxidation method. For example, it is oxidized in a dry atmosphere having an oxygen concentration of 40% at 1000 degrees. The first insulating film 203 is 30 in the case of EPROM.
nm to 50 nm, and in the case of EEPROM, about 10 nm is suitable. The first insulating film 203 is used as a gate insulating film of a semiconductor memory device.

Next, as shown in FIG. 1B, a first polycrystalline silicon film 104 having a thickness of about 200 nm is formed on the first insulating film 103 and the field insulating film 102 by chemical vapor deposition. Usually, monosilane gas is thermally decomposed at around 620 ° C. to deposit the first polycrystalline silicon 106.
Then, in order to reduce the resistance of the first polycrystalline silicon film 106, for example, a Group 5 element (for example, a conductive impurity such as phosphorus element or arsenic) is ion-implanted to
Implantation is performed at about 10 ¹⁵ to 1 10 ¹⁶ atoms · cm ⁻² . Then, the first polycrystalline silicon 1 is formed by the thermal oxidation method.
A first silicon oxide film 105 is formed on the substrate 04 with a thickness of about 10 nm. For example, it is oxidized at 1000 ° C. in a dry atmosphere having an oxygen concentration of about 40%. Then, the second silicon nitride film 106 is formed on the first silicon oxide film 107 by about 10 nm by chemical vapor deposition.

Next, as shown in FIG. 1C, the second silicon nitride film 106, the first silicon oxide film 105, the first polycrystalline silicon film 104, and the first insulating film 103 are formed by a photo and etching method. Remove unnecessary parts of.

Next, as shown in FIG. 1D, the second silicon nitride film 106 and the first silicon oxide film 106 are formed by a thermal oxidation method (for example, oxidation in a dry atmosphere at an oxygen concentration of 40% at about 1000 ° C.). 105 and a second silicon oxide film 107 on the first polycrystalline silicon film 104 by about 3 nm,
A third silicon oxide film 108 is formed on the semiconductor substrate 101.
To form. The third silicon insulating film 108 is used as a gate insulating film of a driving element of a semiconductor memory element.

Next, as shown in FIG. 1E, the second polycrystalline silicon film 109 is formed on the field insulating film 102 and the second polycrystalline silicon film 109.
Silicon oxide film 107 and the third silicon oxide film 10
A film having a thickness of about 300 nm is formed on the surface 8 by chemical vapor deposition.
Then, an impurity such as phosphorus or arsenic is implanted into the second polycrystalline silicon film 208 by using an ion implantation method to make it a conductor. For example, a group 5 element (for example, a conductive impurity such as phosphorus element or arsenic) is ion-implanted to obtain 1 × 10 5.
Implant about ¹⁵ to 1 × 10 ¹⁶ atoms · cm ⁻² .

Next, as shown in FIG. 1F, the second polycrystalline silicon 109, the second silicon oxide film 107, the second silicon nitride film 106, and the first silicon oxide film 105 are formed by photo and etching methods. And the first
An unnecessary portion of the polycrystalline silicon 104 is removed. This becomes the gate electrode of the semiconductor memory element.

Then, by the photo and etching method,
An unnecessary portion of the second polycrystalline silicon 109 on the third silicon oxide film 108 is removed. This becomes the gate electrode of the transistor (driving element of the semiconductor memory element) of the peripheral circuit.

Finally, an ion implantation method is used to implant impurities such as phosphorus and arsenic to source 11 of the semiconductor memory device.
0 and drain 111, source 112 and drain 113 of the transistor of the peripheral circuit are formed.

The above manufacturing process is the semiconductor device and the manufacturing method thereof according to one embodiment of the present invention.

Thus, as shown in FIG. 1B, the first silicon oxide film 105 is formed on the first polycrystalline silicon 104 before etching the first polycrystalline silicon film 104.
And forming the second silicon nitride film 106, and thereafter,
As shown in FIG. 1C, by forming the first polycrystalline silicon film 104, the silicon substrate is not etched unlike the prior art.

In addition, it is necessary to remove the first polycrystalline silicon 104, the first silicon oxide film 105, and the second silicon nitride film 106, which are formed in a region to be a driving element of the semiconductor memory device, once to remove the photo. And an etching process.

The invention made by the present inventor has been specifically described based on the above embodiment, but the present invention is not limited to the above embodiment, and is modified within a range not departing from the gist thereof. Of course, you can do that.

For example, in the embodiment of the manufacturing method of the present invention, the ONO film (SiO ₂
/ SiN / Si0 ₂ was used, but the NO film (SiN / S
It is effective even when i0 ₂ ) is used.

[0029]

According to the present invention, silicon oxide which is an insulating film between a floating gate (first polycrystalline silicon) and a control gate (second polycrystalline silicon) formed in a region to be a driving element of a semiconductor memory element. By forming the film and the silicon nitride film before etching the first polycrystalline silicon, the floating gate (first polycrystalline silicon) and the control gate (second polycrystalline silicon) formed in the region to be the driving element of the semiconductor memory element are formed. It is possible to remove the silicon oxide film and the silicon nitride film, which are insulating films between polycrystalline silicon, without damaging the semiconductor substrate. Further, the first polycrystalline silicon and the first silicon oxide film formed in the region to be the driving element of the semiconductor memory element can be removed by one photo and etching step, and the number of manufacturing steps can be reduced. It becomes possible to do.

[Brief description of drawings]

FIG. 1 is a main sectional view for explaining an embodiment of a method for manufacturing a semiconductor device of the present invention in the order of steps and a main sectional view for explaining the semiconductor device.

FIG. 2 is a main cross-sectional view for explaining a conventional method for manufacturing a semiconductor device in order of steps and a main cross-sectional view for explaining the semiconductor device.

[Explanation of symbols]

101 semiconductor substrate 102 field insulating film 103 first insulating film 104 first polycrystalline silicon film 105 first silicon oxide film 106 second silicon nitride film 107 second silicon oxide film 108 third silicon oxide film 109 second polycrystalline silicon film 110 Source of Semiconductor Memory Device 111 Drain of Semiconductor Memory Device 112 Source of Peripheral Circuit Transistor of Semiconductor Memory Device 113 Drain of Peripheral Circuit Transistor of Semiconductor Memory Device 201 Semiconductor Substrate 202 Field Insulating Film 203 First Insulating Film 204 First Polycrystalline Silicon Film 205 First silicon oxide film 206 Second silicon nitride film 207 Second silicon oxide film 208 Third silicon oxide film 209 Second polycrystalline silicon film 210 Source of semiconductor memory device 211 Drain of semiconductor memory device 212 Peripheral circuit Source of the 213 transistor 213 drain of the peripheral circuit transistor

Claims (2)

[Claims] 1. A MOS type transistor structure having a floating gate and a control gate, wherein a control threshold voltage of the characteristic of the MOS transistor of the control gate changes depending on how the charge is injected into the floating gate. In the method for manufacturing a semiconductor device, a step of forming a field insulating film on a semiconductor substrate, a step of forming a first insulating film on the semiconductor substrate, and forming a conductor layer on the first insulating film and the field insulating film. The step of forming a first silicon oxide film on the conductor layer, the step of forming a silicon nitride film on the first silicon oxide film, the conductor layer and the first silicon oxide in a region for forming a MOS transistor. Film and a step of removing the silicon nitride film so as to leave the semiconductor film Method of manufacturing location. 2. A MOS type transistor structure having a floating gate and a control gate, wherein a control threshold voltage of the characteristic of the MOS transistor of the control gate changes depending on how the charge is injected into the floating gate. In the semiconductor device, the first insulating film is formed on the semiconductor substrate of the semiconductor memory element, and the first polycrystalline silicon film (floating gate) is formed on the insulating film. A first silicon oxide film is formed on the polycrystalline silicon film, a silicon nitride film is formed on the first silicon oxide film, and a second silicon oxide film is formed on the silicon nitride film.
A semiconductor device, wherein a silicon oxide film is formed, and a third insulating film is formed next to the first polycrystalline silicon film.