JPH11297814A - Semiconductor device and manufacture thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a semiconductor device of a trench isolation structure and a manufacturing method thereof, wherein impurities are prevented from being diffused from channel stopper implantation layers, and, at the same time, the generation of voids in element isolation oxide films can be inhibited. SOLUTION: This device is provided with a silicon substrate 101, trenches 102 formed in this substrate 101, nitrooxide films 104 formed on the inner surfaces of the trenches 102, element isolation insulating films 103 buried in the nitrooxide films 104 formed on the inner surfaces of the trenches 102, and elements 109 formed between these element isolation insulating films 103.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor device having a trench isolation structure used in a semiconductor integrated circuit and a method for manufacturing the same.

[0002]

2. Description of the Related Art In recent years, miniaturization and high integration of semiconductor elements have rapidly progressed, and accordingly, semiconductor devices having a trench isolation structure capable of performing element isolation in a small area have been adopted. Hereinafter, a conventional trench isolation structure and a manufacturing method thereof will be described. FIG. 3 shows a sectional structure of a conventional trench isolation. In FIG. 3, 1 is a silicon substrate, 2 is an element isolation insulating film (oxide film), 3 is a gate insulating film, 4 is a gate electrode, 5 is a trench formed in the silicon substrate 1, 6 is a trench as a channel stopper of a transistor. 5, an injection layer injected into the side wall and the bottom of the substrate,
Reference numeral 7 denotes a channel injection layer injected below the gate insulating film 3, and 8 denotes an injection layer injected into the source / drain regions.

The operation of the semiconductor device having the trench isolation structure configured as described above will be described below. The gate electrode 4, the gate insulating film 3, the channel injection layer 7, and the source
In order to separate the transistor elements composed of the drain injection layer 8, an element isolation insulating film 2 for insulating the elements and a channel stopper injection layer 6 for electrically separating the elements are required. In the trench isolation structure, an element isolation insulating film 2 is formed in a trench 5 formed by anisotropically etching the silicon substrate 1. With this structure, since there is no bird's beak generated in the LOCOS isolation, which is the most commonly used isolation structure, element isolation in a small area can be realized.

FIG. 4 shows a method of manufacturing a semiconductor device having a conventional trench isolation structure. In FIG. 4, 1 is a silicon substrate, 2 is an element isolation insulating film (oxide film), 5
Is a trench, 6 is a channel stopper injection layer, and 10 is a silicon nitride film. A method of manufacturing the semiconductor device having the trench isolation structure configured as described above will be described below. As shown in FIG. 4A, an inactive region on the silicon substrate 1 is patterned using the silicon nitride film 10.
Next, as shown in FIG. 4B, a trench 5 is formed in the silicon substrate 1 by anisotropic etching. Next, as shown in FIG. 4C, a channel stopper is implanted into the side wall and the bottom of the trench 5 to form a channel stopper implanted layer 6. Next, as shown in FIG.
An element isolation insulating film (oxide film) is deposited by using the VD method or the low pressure CVD method. Next, as shown in FIG.
MP (Chemical Mechanical Po)
The element isolation insulating film 2 is polished to the same height as the silicon nitride film 10 by lishing (chemical mechanical polishing). Next, as shown in FIG. 4F, the silicon nitride film 10 is removed to form a transistor in the active region.

[0005]

However, this conventional semiconductor device has a disadvantage that the channel stopper injection layer 6 diffuses into the element isolation insulating film 2 in a heat treatment step after the injection. Also, when the element isolation insulating film 2 is deposited,
Since there is a difference in the time from the initial reaction to the deposition (hereinafter referred to as the "inactivation time") between the silicon nitride film 10 and the silicon on the side wall of the trench 5, an overhang occurs at the shoulder of the trench 5 and the final time. This has the disadvantage that voids are generated in the element isolation insulating film 2. A disadvantage caused by the generation of voids is a bridge between the same layers that is generated by being embedded in a wiring portion or an electrode material in a void portion in a wiring step (including a step of forming a gate electrode).

SUMMARY OF THE INVENTION It is an object of the present invention to provide a semiconductor device having a trench isolation structure capable of suppressing generation of voids in an element isolation oxide film and a method of manufacturing the same.

[0007]

According to a first aspect of the present invention, there is provided a semiconductor device comprising: a semiconductor substrate; a trench formed in the semiconductor substrate; an oxynitride film formed on an inner surface of the trench;
An element isolation insulating film buried on the oxynitride film of the trench,
And an element formed between the element isolation insulating films.

According to the first aspect of the present invention, by forming the oxynitride film between the inner surface of the trench and the element isolation oxide film, it is possible to suppress generation of voids when the element isolation insulating film is deposited. A semiconductor device according to claim 2, comprising: a semiconductor substrate;
A trench formed in the semiconductor substrate, a channel stopper injection layer implanted into the inner surface of the trench, an oxynitride film formed on the surface of the channel stopper injection layer,
An element isolation insulating film deposited on the oxynitride film of the trench,
And an element formed between the element isolation insulating films.

According to the semiconductor device of the second aspect, in addition to the same effect as the first aspect, even if a high-temperature heat treatment is applied, diffusion from the channel stopper injection layer on the side wall and the bottom of the trench is suppressed. Can be. According to a third aspect of the present invention, in the first or second aspect, the oxynitride film contains silicon dioxide as a main component and contains nitrogen atoms in the film.

According to the semiconductor device of the third aspect, the same effect as that of the first aspect is obtained. According to a fourth aspect of the present invention, in the semiconductor device according to the first or second aspect, the element includes a gate electrode, a gate insulating film below the gate electrode, and a channel injection layer implanted below the gate insulating film. And a source / drain injection layer adjacent to the channel injection layer.

According to the semiconductor device of the fourth aspect, the same effect as that of the first or second aspect is obtained. The method of manufacturing a semiconductor device according to claim 5, wherein a step of forming a trench on the semiconductor substrate, a step of forming an oxynitride film on the inner surface of the trench, and forming the element isolation insulating film in the trench with the oxynitride film therebetween. And a step of depositing.

According to the method of manufacturing a semiconductor device according to the fifth aspect, the same effect as that of the first aspect is obtained. According to a sixth aspect of the present invention, in the method of manufacturing a semiconductor device, a step of forming a trench on a semiconductor substrate, a step of forming a channel stopper injection layer on an inner surface of the trench, and forming an oxynitride film on a surface of the channel stopper injection layer And a step of depositing an element isolation insulating film in the trench via an oxynitride film.

According to the method of manufacturing a semiconductor device of the sixth aspect, the same effect as that of the second aspect can be obtained. According to a seventh aspect of the present invention, in the method of the fifth or sixth aspect, the step of forming the oxynitride film includes heat-treating the inside of the trench to a high temperature in a nitride gas atmosphere.

According to a seventh aspect of the invention, there is provided a method of manufacturing a semiconductor device.
Then, the same effect as that of the fifth or sixth aspect is obtained. Contract
The method of manufacturing a semiconductor device according to claim 8 is the method according to claim 7.
And the nitriding gas is N _TwoO gas, nitrous oxide gas, ammonia
Near gas, N_TwoMixed gas of O and oxygen, or nitrous oxide
It is a mixed gas of gas and oxygen.

According to the method of manufacturing a semiconductor device according to the eighth aspect, the same effect as that of the seventh aspect is obtained. The method of manufacturing a semiconductor device according to claim 9, further comprising: forming a patterned silicon nitride film on the silicon substrate; forming a trench by anisotropic etching using the silicon nitride film as a mask; Heat treating in an atmosphere to form an oxynitride film on the inner surface of the trench, depositing an element isolation insulating film on the silicon substrate, polishing the element isolation insulating film to the height of the silicon nitride film, The method includes a step of removing the nitride film.

According to the method of manufacturing a semiconductor device of the ninth aspect, in addition to the same effect as the first aspect, the step of forming the oxynitride film also serves as rounding oxidation performed to round the corner of the shoulder of the trench. Therefore, an increase in the number of steps can be avoided.

[0017]

1 and 2 show a semiconductor device having a trench isolation structure according to an embodiment of the present invention.
This will be described below. FIG. 1 shows a sectional configuration of a semiconductor device having a trench isolation structure according to an embodiment of the present invention. In FIG. 1, 101 is a silicon substrate which is a semiconductor substrate, 102 is a trench formed by etching the silicon substrate 101, 103 is a low pressure CVD or a normal pressure CVD.
Element isolation insulating film, which is a buried oxide film formed by the
104, an oxynitride film formed by raising the silicon inside the trench 102 to a high temperature in an N ₂ O gas (laughing gas), nitrous oxide gas, or ammonia atmosphere;
Is a channel stopper implanted layer implanted into the side wall and bottom surface of the trench 102; 106 is a gate insulating film (oxide film) formed on the silicon substrate 101; 107 is a polysilicon electrode formed on the gate insulating film 106; A channel injection layer 109 is a source / drain injection layer.

In the transistor element including the gate insulating film 106, the polysilicon electrode 107, the channel injection layer 108, and the source / drain injection layer 109, a portion other than the element is separated by an insulating film in order to separate adjacent elements. Must be enclosed in In the trench isolation structure, a trench 102 is formed in a silicon substrate 101 by anisotropic etching, and the inside of the trench 102 is separated by a CVD method.
Embed with Further, in order to enhance the electrical isolation between the transistor elements, ion implantation of a polarity opposite to that of the source / drain implantation layer 109 is implanted into the side wall and bottom surface of the trench 102 to form the channel implantation layer 108. Trench 1
02 and the oxynitride film 104 between the element isolation insulating film 103
Is a film containing a silicon dioxide film as a main component and containing a predetermined concentration of nitrogen atoms at a predetermined position in the film. The oxynitride film 104 is formed by depositing a silicon dioxide film in an atmosphere of laughing gas, nitrous oxide gas or ammonia gas at 700 to 1100.
It is obtained by heat treatment at a high temperature of ° C. This oxynitride film 104 is used for suppressing the diffusion of ion species such as boron since dangling bonds and broken bonds existing in silicon dioxide are terminated by nitrogen atoms. In order to suppress the diffusion from the channel stopper injection layer 105, the nitrogen concentration in the oxynitride film 104 needs to be 1 atm% or more.

Next, an embodiment of a method of manufacturing a semiconductor device having a trench isolation structure according to the present invention will be described with reference to FIG.
This will be described below. FIG. 2 is a process sectional view of a method for manufacturing a trench isolation structure according to the present invention. In FIG. 2, 101 is a silicon substrate, 111 is a silicon nitride film (Si ₃ N ₄ film) formed by a low pressure CVD method, 102 is a trench formed by etching the silicon substrate 101, 113 is N ₂ O gas, and 104 is An oxynitride film 103 is a CVD oxide film, that is, an element isolation insulating film.

As shown in FIG. 2A, a silicon substrate 10
1 is patterned using a silicon nitride film 111. Next, as shown in FIG.
Anisotropic etching is performed using 11 as a mask to form a trench 102. Next, as shown in FIG.
A heat treatment of 700 to 1100 ° C. in an atmosphere of ₂ O gas 113, to form the oxynitride film 104 on the side walls and bottom of trench 102. The oxynitride film 104 has a silicon dioxide film containing nitrogen atoms. This oxynitridation step
Since it can also serve as rounding oxidation performed to round the corner of the shoulder of the trench 102, the number of steps is not increased. Next, as shown in FIG. 2D, an element isolation insulating film 103 is deposited by a CVD method. At this time, the silicon nitride film 1
11 and the composition of the oxynitride film 104 are close to each other, so that the difference in the activation time between the silicon nitride film 111 and the side wall of the trench 102 can be reduced.
Generation of voids in the element isolation insulating film 103 can be prevented. Next, as shown in FIG. 2E, the element isolation insulating film 103 is raised to the height of the silicon nitride film 111 by CMP.
After polishing, the silicon nitride film 111 is removed as shown in FIG.

As described above, after the trench 102 is formed, N
_{After the} oxynitride film 104 is formed by performing a heat treatment at a high temperature of 700 ° C. to 1100 ° C. in an atmosphere of 2O gas 113, the element isolation insulating film 103 is formed. An isolation structure can be formed. The step of forming the oxynitride film 104 can also serve as a thermal oxidation treatment for rounding the shoulder of the trench 102, and does not increase the number of steps.

In this embodiment, the N ₂ O gas is used as the nitriding gas at the time of forming the oxynitride film 104. However, nitrous oxide gas, ammonia gas, mixed gas of N ₂ O and oxygen, nitrous oxide gas The same effect can be obtained by using a mixed gas of oxygen and oxygen. In the manufacturing process shown in FIG.
In the case where the step of implanting the channel stopper injection layer 105 is provided after the formation of the trench 102 in (b), the semiconductor device shown in FIG. 1 can be manufactured. In this case, diffusion from the channel stopper injection layer 105 is suppressed. can do.

Here, the invention described in the claims is not limited to the embodiment described in the above embodiment.

[0024]

According to the semiconductor device of the first aspect, by forming an oxynitride film between the inner surface of the trench and the element isolation oxide film, it is possible to suppress generation of voids when the element isolation insulating film is deposited. According to the semiconductor device of the second aspect, in addition to the same effects as those of the first aspect, even when a high-temperature heat treatment is applied, diffusion from the channel stopper injection layer on the side wall and the bottom of the trench can be suppressed.

According to the semiconductor device of the third aspect, the same effect as that of the first aspect is obtained. According to the semiconductor device of the fourth aspect, there is an effect similar to that of the first or second aspect.
According to the semiconductor device of the fifth aspect, the same effect as that of the first aspect is obtained. According to the method of manufacturing a semiconductor device of the sixth aspect, the same effect as that of the second aspect can be obtained.

According to the method of manufacturing a semiconductor device according to the seventh aspect, the same effects as those of the fifth or sixth aspect can be obtained. According to the method of manufacturing a semiconductor device according to claim 8, claim 7 is provided.
Has the same effect as. According to the method of manufacturing a semiconductor device according to the ninth aspect, in addition to the same effect as the first aspect, the step of forming the oxynitride film can also serve as rounding oxidation performed to round the corner of the shoulder of the trench. An increase in the number of steps can be avoided.

[Brief description of the drawings]

FIG. 1 is a sectional view of a semiconductor device having a trench isolation structure according to an embodiment of the present invention.

FIG. 2 is a cross-sectional view showing the steps of the method for manufacturing the semiconductor device in the order of steps.

FIG. 3 is a cross-sectional view of a conventional semiconductor device having a trench isolation structure.

FIG. 4 is a cross-sectional view showing steps of a conventional manufacturing method in the order of steps.

[Explanation of symbols]

Reference Signs List 101 silicon substrate (semiconductor substrate) 102 trench 103 element isolation insulating film 104 oxynitride film 105 channel stopper injection layer 106 gate insulating film 107 polysilicon electrode 108 channel injection layer 109 source / drain injection layer 111 silicon nitride film 113 N ₂ O gas

Claims (9)

[Claims] A semiconductor substrate; a trench formed in the semiconductor substrate; an oxynitride film formed on an inner surface of the trench; an element isolation insulating film buried on the oxynitride film in the trench; And a device formed between the device isolation insulating films. 2. A semiconductor substrate, a trench formed in the semiconductor substrate, a channel stopper injection layer implanted into an inner surface of the trench, an oxynitride film formed on a surface of the channel stopper injection layer, A semiconductor device comprising: an element isolation insulating film deposited on the oxynitride film in a trench; and an element formed between the element isolation insulating films. 3. The semiconductor device according to claim 1, wherein the oxynitride film contains silicon dioxide as a main component and contains nitrogen atoms in the film. 4. The device comprises a gate electrode, a gate insulating film below the gate electrode, a channel injection layer implanted below the gate insulating film, and a source / drain implant adjacent to the channel injection layer. The semiconductor device according to claim 1, further comprising a layer. 5. A step of forming a trench on a semiconductor substrate, and a step of forming an oxynitride film on an inner surface of the trench;
Depositing an element isolation insulating film in the trench via the oxynitride film. 6. A step of forming a trench on a semiconductor substrate, a step of forming a channel stopper injection layer on an inner surface of the trench, a step of forming an oxynitride film on a surface of the channel stopper injection layer, and the step of: Depositing an element isolation insulating film therein via the oxynitride film. 7. The method for manufacturing a semiconductor device according to claim 5, wherein the step of forming the oxynitride film includes heat-treating the inside of the trench to a high temperature in a nitriding gas atmosphere. 8. The semiconductor device according to claim 7, wherein the nitriding gas is an N ₂ O gas, a nitrous oxide gas, an ammonia gas, a mixed gas of N ₂ O and oxygen, or a mixed gas of nitrous oxide and oxygen. Manufacturing method. 9. A step of forming a patterned silicon nitride film on a silicon substrate, a step of forming a trench by anisotropic etching using the silicon nitride film as a mask, and a heat treatment in an atmosphere of a nitriding gas. Forming an oxynitride film on the inner surface of the trench, depositing an element isolation insulating film on the silicon substrate, polishing the element isolation insulating film to a height of the silicon nitride film; A method for manufacturing a semiconductor device including a step of removing a film.