JP2005019712A - Method of manufacturing semiconductor device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To suppress the thermal oxidation of a semiconductor substrate via pin holes in a nitride film. <P>SOLUTION: A silicon oxide film 5 is laminated on a silicon nitride film 4, and a thermal oxidation film 6 is formed in a transistor formation area R1. Furthermore, a thermal oxidation film 7 having a different thickness from the thermal oxidation film 6 is formed in a transistor formation area R2, and an upper electrode 11 is formed on the silicon nitride film 4 in a capacitor formation area R3. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for manufacturing a semiconductor device, and is particularly suitable for application in the case where a nitride film for selective oxidation is used in combination with a capacitor.
[0002]
[Prior art]
In the conventional semiconductor device, for example, as disclosed in Patent Document 1, in order to improve the film quality of the silicon nitride film, there is a method in which after the silicon nitride film is formed, the silicon nitride film is subjected to thermal nitridation treatment. Has been done.
[0003]
[Patent Document 1]
Japanese Patent Laid-Open No. 7-74321
[Problems to be solved by the invention]
However, in the method of performing thermal nitridation of the silicon nitride film, the pinhole formed in the silicon nitride film remains as it is. For this reason, when a silicon nitride film for selective oxidation is used in combination with a capacitor, if the thickness of the silicon nitride film is reduced in order to increase the capacitance of the capacitor, the silicon substrate is inserted through a pinhole formed in the silicon nitride film. There is a problem that the film quality of the gate oxide film formed on the silicon substrate deteriorates due to thermal oxidation.
[0005]
Accordingly, an object of the present invention is to provide a method for manufacturing a semiconductor device capable of suppressing the thermal oxidation of a semiconductor substrate through pinholes in a nitride film.
[0006]
[Means for Solving the Problems]
In order to solve the above-described problem, according to a method for manufacturing a semiconductor device according to one embodiment of the present invention, in a method for manufacturing a semiconductor device in which gate oxide films having different thicknesses are formed over a semiconductor substrate, nitridation for selective oxidation is performed. A gate oxide film having a different thickness is formed by forming an oxide film on the film and then performing heat treatment on the semiconductor substrate.
[0007]
As a result, it becomes possible to perform heat treatment of the semiconductor substrate in a state where the pin holes of the selective oxidation nitride film are closed with the oxide film, and even when the selective oxidation nitride film is thinned, the selective oxidation nitridation is possible. It is possible to prevent the semiconductor substrate from being thermally oxidized through the pinhole formed in the film. Therefore, even when the selective oxidation nitride film is used in combination with the capacitor, it is possible to increase the capacity of the capacitor while suppressing the deterioration of the film quality of the gate oxide film, and to reduce the size of the capacitor. Become.
[0008]
In addition, according to the method for manufacturing a semiconductor device of one embodiment of the present invention, a step of forming an element isolation insulating film on a semiconductor substrate, and a nitrogen film and an oxide film on the semiconductor substrate separated by the element isolation insulating film Sequentially exposing the first and second regions of the semiconductor substrate separated by the element isolation insulating film by selectively removing the nitrogen film and the oxide film, and exposing the first region. Forming a first thermal oxide film in the first region of the semiconductor substrate by performing a heat treatment on the semiconductor substrate, and selectively removing the nitrogen film and the oxide film remaining on the semiconductor substrate. The film thickness is different from that of the first thermal oxide film by performing the step of exposing the second region of the semiconductor substrate separated by the element isolation insulating film and the heat treatment of the semiconductor substrate from which the second region is exposed. Second Forming an oxide film in the second region of the semiconductor substrate; removing an oxide film on a remaining nitrogen film of the semiconductor substrate separated by the element isolation insulating film; and the first region and the second Forming a gate electrode on each of the regions, and forming an upper electrode on the third region.
[0009]
As a result, even when pinholes exist in the nitride film, the semiconductor substrate can be selectively thermally oxidized in a state where the pinholes in the nitride film are closed with an oxide film. It is possible to form thermal oxide films having different thicknesses on the semiconductor substrate while suppressing thermal oxidation of the semiconductor substrate. Therefore, the nitride film can be used in combination with the capacitor while making the nitride film thinner, and the capacitance of the capacitor can be increased while suppressing the deterioration of the film quality of the thermal oxide film.
[0010]
According to the method for manufacturing a semiconductor device of one embodiment of the present invention, the oxide film over the nitrogen film is formed by thermal CVD.
As a result, the oxide film formed on the nitrogen film can be densified, and selective oxidation can be stably performed even when the nitrogen film is thinned. According to the method of manufacturing a semiconductor device of one embodiment of the present invention, the nitrogen film has a thickness of 100 mm or less.
[0011]
As a result, the nitrogen film can be made thinner, and the capacitance of the capacitor can be increased.
According to the method for manufacturing a semiconductor device of one embodiment of the present invention, when the second region of the semiconductor substrate is exposed, the first region where the first thermal oxide film is formed is covered with a photoresist. It is characterized by.
[0012]
This makes it possible to prevent the first thermal oxide film from being damaged even when dry etching of the nitrogen film is performed when exposing the second region of the semiconductor substrate. It is possible to form the second thermal oxide film while preventing the deterioration of the film quality.
In addition, according to the method of manufacturing a semiconductor device according to one aspect of the present invention, when removing the oxide film on the nitrogen film, the first region in which the first thermal oxide film is formed and the second thermal oxidation The second region where the film is formed is covered with a photoresist.
[0013]
This makes it possible to prevent the first thermal oxide film and the second thermal oxide film from being removed when removing the oxide film on the nitrogen film, and the first thermal oxide film and the second thermal oxide film. It is possible to remove the oxide film on the nitrogen film while leaving the film as it is.
[0014]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, a semiconductor device manufacturing method according to an embodiment of the present invention will be described with reference to the drawings.
FIG. 1 is a cross-sectional view showing a method for manufacturing a semiconductor device according to an embodiment of the present invention.
[0015]
In FIG. 1A, an element isolation insulating film 2 is formed on a semiconductor substrate 1 by, for example, a LOCOS (Local Oxidation of Silicon) method. The semiconductor substrate 1 is provided with transistor formation regions R1 and R2 and a capacitor formation region R3 separated by the element isolation insulating film 2. Note that STI (Shallow Trench Isolation) may be used for element isolation of the semiconductor substrate 1.
[0016]
Then, the sacrificial oxide film 3 is formed on the semiconductor substrate 1 on which the element isolation insulating film 2 is formed by performing thermal oxidation of the semiconductor substrate 1. Then, after a silicon nitride film 4 is laminated on the semiconductor substrate 1 on which the sacrificial oxide film 3 is formed by a method such as plasma CVD, a silicon oxide film 5 is laminated on the silicon nitride film 4 by a method such as thermal CVD. To do.
Here, the film thickness of the silicon nitride film 4 can be 100 mm or less, and the film thickness of the silicon oxide film 5 can be 100 mm or less. Further, by depositing the silicon oxide film 5 on the silicon nitride film 4 using thermal CVD, the silicon oxide film 5 can be densified. Even when the silicon nitride film 4 is thinned, selective oxidation is performed. Can be performed stably.
[0017]
Next, as shown in FIG. 1B, the sacrificial oxide film 3, the silicon nitride film 4 and the silicon oxide film 5 are patterned by using a photolithography technique and an etching technique to thereby form a sacrificial oxide film in the transistor formation region R1. 3. The silicon nitride film 4 and the silicon oxide film 5 are removed to expose the surface of the semiconductor substrate 1 in the transistor formation region R1.
[0018]
Next, as shown in FIG. 1C, the semiconductor substrate 1 is thermally oxidized using the silicon nitride film 4 and the silicon oxide film 5 as an antioxidant film, thereby forming a thermal oxide film 6 in the transistor formation region R1. To do. Here, by performing thermal oxidation of the semiconductor substrate 1 using the silicon nitride film 4 and the silicon oxide film 5 as an antioxidant film, even when the silicon nitride film 4 has pinholes, the semiconductor substrate 1 in the transistor formation region R2 Can be suppressed, and the semiconductor substrate 1 in the transistor formation region R1 can be selectively thermally oxidized.
[0019]
Next, as shown in FIG. 1 (d), the sacrificial oxide film 3, the silicon nitride film 4 and the silicon oxide film 5 are patterned by using a photolithography technique and an etching technique to thereby form a sacrificial oxide film in the transistor formation region R2. 3. The silicon nitride film 4 and the silicon oxide film 5 are removed to expose the surface of the semiconductor substrate 1 in the transistor formation region R2.
[0020]
Here, when exposing the surface of the semiconductor substrate 1 in the transistor formation region R2, the transistor formation region R1 can be covered with a photoresist. Thus, even when the sacrificial oxide film 3, the silicon nitride film 4 and the silicon oxide film 5 are dry etched when exposing the surface of the semiconductor substrate 1 in the transistor formation region R2, the thermal oxide film 6 is damaged. Therefore, it is possible to prevent the thermal oxide film 6 from being deteriorated.
[0021]
Next, as shown in FIG. 1E, the semiconductor substrate 1 is thermally oxidized using the silicon nitride film 4 and the silicon oxide film 5 as an anti-oxidation film, so that thermal oxidation having a film thickness different from that of the thermal oxide film 6 is performed. A film 7 is formed in the transistor formation region R2.
Next, as shown in FIG. 1 (f), the transistor formation region R1 and the transistor formation region R2 are covered with a photoresist 8, and then the silicon oxide film 5 is etched to thereby form the silicon oxide film in the capacitor formation region R3. 5 is removed. Here, the transistor formation region R1 and the transistor formation region R2 are covered with the photoresist 8, and then the silicon oxide film 5 is etched to remove the silicon oxide film 5 in the capacitor formation region R3. It is possible to prevent the thermal oxide films 6 and 7 respectively formed on R1 and R2 from being removed, and the silicon oxide film 5 on the silicon nitride film 4 is formed while leaving the thermal oxide films 6 and 7 as they are. It can be removed.
[0022]
Next, as shown in FIG. 1 (g), polycrystalline silicon is deposited on the semiconductor substrate 1 by a method such as CVD, and the polycrystalline silicon is patterned by using a photolithography technique and an etching technique. Gate electrodes 9 and 10 are formed on oxide films 6 and 7, respectively, and upper electrode 11 is formed on silicon nitride film 4 in capacitor formation region R3.
[0023]
As a result, even when there are pinholes in the silicon nitride film 4, the semiconductor substrate 1 can be selectively thermally oxidized while the pinholes in the silicon nitride film 4 are closed with the silicon oxide film 5. It is possible to form the thermal oxide films 6 and 7 having different thicknesses on the semiconductor substrate 1 while suppressing the thermal oxidation of the semiconductor substrate 1 through the pinholes. Therefore, the silicon nitride film 4 can be used together with the capacitor while making the silicon nitride film 4 thinner, and the capacitance of the capacitor is increased while suppressing the deterioration of the film quality of the thermal oxide films 6 and 7. It becomes possible.
[0024]
In the above-described embodiment, the method for forming the two types of thermal oxide films 6 and 7 on the same semiconductor substrate 1 has been described. However, the three types of thickness of the thermal oxide films 6 and 7 are formed on the same semiconductor substrate. You may make it form.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view showing a method for manufacturing a semiconductor device according to an embodiment.
[Explanation of Symbols] R1, R2 Transistor formation region, R3 Capacitor formation region, 1 Semiconductor substrate, 2 Element isolation insulating film, 3 Sacrificial oxide film, 4 Nitride film, 5 Oxide film, 6, 7 Thermal oxide film, 8 Resist, 9, 10 Gate electrode, 11 Upper electrode

Claims (6)

In a method for manufacturing a semiconductor device in which gate oxide films having different thicknesses are formed on a semiconductor substrate,
A method of manufacturing a semiconductor device, comprising forming a gate oxide film having a different thickness by forming an oxide film on a selective oxidation nitride film and then performing a heat treatment on the semiconductor substrate. Forming an element isolation insulating film on a semiconductor substrate;
Sequentially stacking a nitrogen film and an oxide film on the semiconductor substrate separated by the element isolation insulating film;
Exposing the first region of the semiconductor substrate separated by the element isolation insulating film by selectively removing the nitrogen film and the oxide film;
Forming a first thermal oxide film in the first region of the semiconductor substrate by performing a heat treatment of the semiconductor substrate in which the first region is exposed;
Exposing the second region of the semiconductor substrate separated by the element isolation insulating film by selectively removing the nitrogen film and the oxide film remaining on the semiconductor substrate;
Forming a second thermal oxide film having a thickness different from that of the first thermal oxide film in the second region of the semiconductor substrate by performing a heat treatment on the semiconductor substrate in which the second region is exposed;
Removing the oxide film on the remaining nitrogen film of the semiconductor substrate separated by the element isolation insulating film;
Forming a gate electrode on each of the first region and the second region, and forming an upper electrode on the third region. 3. The method of manufacturing a semiconductor device according to claim 2, wherein the oxide film on the nitrogen film is formed by thermal CVD. 4. The method of manufacturing a semiconductor device according to claim 2, wherein the thickness of the nitrogen film is 100 mm or less. 5. The first region in which the first thermal oxide film is formed is covered with a photoresist when the second region of the semiconductor substrate is exposed. 5. Manufacturing method of the semiconductor device. When removing the oxide film on the nitrogen film, the first region where the first thermal oxide film is formed and the second region where the second thermal oxide film is formed are covered with a photoresist. The method for manufacturing a semiconductor device according to claim 2, wherein the method is a semiconductor device manufacturing method.

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