JPH06224442A - Mos type integrated circuit with built-in nonvolatile memory and manufacture thereof - Google Patents

Abstract

PURPOSE:To improve a reliability of a nonvolatile memory without reducing a performance of a normal MOS transistor. CONSTITUTION:At least one of a first gate insulating film 5 and a second gate insulating film 9 of a nonvolatile memory 2, for example, the first gate insulating film 5 contains nitrogen atoms, and a gate insulating film 6 of a normal MOS transistor 3 does not contain nitrogen. When the gate insulating film contains nitrogen, TDDB characteristics and a hot carrier resistance are improved, and thus a reliability of the nonvolatile memory 2 in which a higher reliability is required is improved. Though an electrical driving capability is reduced due to the nitrogen content, the gate insulating film 6 in the normal MOS transistor 3 which has a margin reliability does not contain nitrogen, and thus the electrical driving capability is not reduced.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a MOS type integrated circuit having a built-in non-volatile memory, and in particular, a non-volatile memory capable of increasing the reliability of the non-volatile memory without degrading the performance of ordinary MOS transistors. Built-in MOS
Type integrated circuit and its manufacturing method.

[0002]

2. Description of the Related Art As a MOS type integrated circuit, there is one having a non-volatile memory as shown in FIG. A nonvolatile memory generally has a floating gate (first gate) formed on a first gate insulating film and a control gate (second gate) formed on the floating gate via a second gate insulating film. It has a so-called double gate structure formed, which is a significant difference from the ordinary MOS transistor. In this specification, a normal MOS transistor means a MOS transistor having no multiple gate structure.

The non-volatile memory is an ordinary MOS.
The reliability required for the gate insulating film is different from that of the transistor, and the reliability of the gate insulating film must be high. First, the control voltage applied to the control gate is as high as, for example, ten and several volts, and since the electric field strength applied to the gate insulating film is high, reliability is required in terms of withstand voltage, and secondly, the first gate. This is because electrons pass through the insulating film due to the tunnel effect and have a great influence on storage, reading, and erasing operations, so that higher reliability is particularly required for the first gate insulating film.

However, the conventional MOS with built-in non-volatile memory
In the type integrated circuit, both the gate insulating film of the non-volatile memory and the gate insulating film of the ordinary MOS transistor are formed of the ordinary oxide film SiO ₂ .

[0005]

In the conventional MOS integrated circuit with a built-in non-volatile memory, high reliability is required for the gate insulating film of the non-volatile memory, especially for the first gate insulating film. Since it is formed of the ordinary silicon oxide film SiO ₂ like the gate insulating film of the ordinary MOS transistor, there is a problem that the reliability of the gate insulating film of the non-volatile memory is not sufficient.

The present invention has been made to solve such a problem, and an object thereof is to improve the reliability of a non-volatile memory without degrading the performance of an ordinary MOS transistor.

[0007]

According to another aspect of the present invention, there is provided a MOS type integrated circuit including a nonvolatile memory, wherein at least one of a first gate insulating film and a second gate insulating film of the nonvolatile memory is a nitrogen atom. And a gate insulating film of a common MOS transistor does not contain nitrogen atoms. A MOS type integrated circuit having a nonvolatile memory according to claim 2 is the MOS type integrated circuit according to claim 1, wherein both the first gate insulating film and the second gate insulating film of the nonvolatile memory contain nitrogen atoms. It is characterized by

An MO incorporating the non-volatile memory according to claim 3.
A method of manufacturing an S-type integrated circuit includes a step of forming a gate insulating film containing a nitrogen atom at the same time on a surface of a region where a nonvolatile memory is to be formed and a surface of a region where a MOS transistor is to be formed, and the gate insulating film. A step of forming an electrode to be a first gate and a second gate insulating film covering a surface of the electrode on a region of the film where a non-volatile memory is to be formed, and a gate insulation of a region where an ordinary MOS transistor is to be formed. Removing the film, and forming a gate insulating film containing no nitrogen atom therein. According to a fourth aspect of the present invention, there is provided a method of manufacturing a MOS integrated circuit having a built-in non-volatile memory according to the third aspect of the present invention, wherein the second gate insulating film covers a surface of an electrode to be the first gate. It is characterized in that a gate insulating film containing nitrogen atoms is formed.

[0009]

According to the MOS type integrated circuit having the non-volatile memory according to the first aspect, the gate insulating film containing a nitrogen atom is excellent in TDDB characteristics and hot carrier resistance as compared with a gate insulating film containing no nitrogen atom. Since at least one of the first gate insulating film and the second gate insulating film of the non-volatile memory contains a nitrogen atom, the reliability of the non-volatile memory can be increased. The performance of the ordinary MOS transistor does not deteriorate because the gate insulating film does not contain nitrogen atoms. That is, when the gate insulating film contains nitrogen atoms, the reliability is increased, but the electric drive capability of the MOS transistor is decreased due to the decrease in mobility. However, there is a margin in reliability of the gate insulating film
Since the gate insulating film of the transistor does not contain nitrogen atoms, the performance of a normal MOS transistor does not deteriorate.

An MO incorporating the non-volatile memory according to claim 2.
According to the method of manufacturing the S-type integrated circuit, both the first gate insulating film and the second gate insulating film of the non-volatile memory contain nitrogen atoms, so that the reliability of the non-volatile memory can be further improved. it can. According to the method of manufacturing a MOS integrated circuit having a built-in non-volatile memory according to claim 3, a gate simultaneously containing nitrogen atoms is formed on the surface of the region where the non-volatile memory is to be formed and the surface of the region where the MOS transistor is to be formed. After forming the insulating film, an electrode to be a floating gate and a second gate insulating film covering the electrode are formed in a portion of the gate insulating film above the region where the nonvolatile memory is to be formed, and then a normal MOS transistor is formed. Since the gate insulating film in the region where the gate is to be formed is removed and the gate insulating film containing no nitrogen atom is formed therein, the first gate insulating film of the non-volatile memory is made to contain the nitrogen atom, so that It is possible to prevent the gate insulating film from containing nitrogen atoms.

An MO incorporating the non-volatile memory according to claim 4.
According to the method for manufacturing an S-type integrated circuit, in the method for manufacturing a MOS-type integrated circuit according to claim 3, since the second gate insulating film that covers the electrode to be the floating gate also contains nitrogen atoms, Both the first gate insulating film and the second gate insulating film can contain nitrogen atoms, and the reliability of the nonvolatile memory can be further improved.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS MO devices incorporating a nonvolatile memory of the present invention are described below.
The S-type integrated circuit and its manufacturing method will be described in detail with reference to the illustrated embodiment. FIG. 1 is a sectional view showing one embodiment of a MOS type integrated circuit of the present invention. In the drawing, 1 is a semiconductor substrate, 2 is a non-volatile memory, 3 is an ordinary MOS transistor, 4 is a field insulating film, 5 is a first gate insulating film of the non-volatile memory 2, and is a silicon oxide containing nitrogen atoms. It consists of SiO ₂ . 6 is an ordinary MOS transistor 3
Of the silicon oxide SiO ₂ containing no nitrogen atom.

Reference numeral 7 denotes a floating gate (first gate) of the non-volatile memory 2, which is made of polysilicon. A gate 8 of the MOS transistor 3 is made of polysilicon. Reference numeral 9 denotes a second gate insulating film formed on the surface of the floating gate 7 of the nonvolatile memory 2, which is made of silicon oxide SiO ₂ containing nitrogen atoms. Reference numeral 10 is a control gate (second gate) formed on the second gate insulating film 9 and is made of polysilicon. In addition, 12, 1
2 is a source, a drain, 13 and 13 of the nonvolatile memory 2.
Are the source and drain of the MOS transistor 3. The MOS type integrated circuit incorporating the nonvolatile memory according to the first embodiment is different from the conventional MOS type integrated circuit incorporating the nonvolatile memory.
The gate insulating film 5 and the second gate insulating film 9 are greatly different in that they are made of silicon oxide SiO ₂ containing nitrogen atoms. The gate insulating film of the ordinary MOS transistor 3 is a silicon oxide SiO containing no nitrogen atom.
_It consists of _two .

As described above, the first gate insulating film 5 and the second gate insulating film 9 are formed of the silicon oxide SiO ₂ containing nitrogen atoms. This is because the TDDB characteristics, hot carrier resistance, etc. are improved, and the reliability of the nonvolatile memory is greatly improved. That is, by including nitrogen atoms, the TDDB characteristics, hot carrier resistance, etc. of the gate insulating film are improved. What to do is 1991 IEEE IE
DM 91-359-362. On the other hand, the gate insulating film 6 of an ordinary MOS transistor is formed of silicon oxide SiO ₂ which does not contain nitrogen atoms. First, when the gate insulating film contains nitrogen atoms, the reliability of the gate insulating film is increased. In the second aspect, the electric drive capability of the MOS transistor is reduced due to the decrease in mobility. Secondly, the MOS transistor operating at a low power supply voltage requires the reliability of the gate insulating film as compared with the MOS transistor operating at a high power supply voltage. Is low and there is a large margin in reliability.

However, according to the present embodiment, an ordinary MO
The reliability of the nonvolatile memory 2 can be improved without deteriorating the capacity of the S transistor. 2A to 2E are cross-sectional views showing the first half of the main part of the method for manufacturing the MOS integrated circuit shown in FIG. 1 in process order.

(A) A field insulating film 4 is formed on the surface of the semiconductor substrate 1 except for a region 2 where a non-volatile memory is to be formed and a region 3 where a MOS transistor is to be formed by selective oxidation of the semiconductor substrate 1. A gate insulating film (thickness 10 mm) 6 made of silicon oxide SiO ₂ is formed on the surface of the region 2 where the non-volatile memory is to be formed and the region 3 where the MOS transistor is to be formed. This formation is performed by heat treatment in a normal wet or dry O ₂ atmosphere. FIG. 2A shows a state after the gate insulating film 6 is formed.

(B) Next, in an atmosphere of NH ₃ or N
By performing high temperature heat treatment in a ₂ O atmosphere, nitrogen atoms are introduced into the gate insulating film 6 to form the gate insulating film 5 containing nitrogen atoms. FIG. 2B is a cross-sectional view showing a state after formation of the gate insulating film 5 containing nitrogen atoms. The introduction of nitrogen atoms into the gate insulating films 6 and 6 is NH
_When performing high temperature heat treatment in ₃ atmospheres, the temperature is 9
The treatment time is preferably 0 to 1000 ° C. and the treatment time is 1 to 30 minutes. When performing high temperature heat treatment in an N ₂ O atmosphere,
The temperature may be 1000 to 1200 ° C., and the treatment time may be 1 to 30 minutes.

(C) Next, as shown in FIG. 2C, a polysilicon layer 7 to be the floating gate of the nonvolatile memory 2 is formed by CVD. (D) Next, as shown in FIG. 2D, the polysilicon layer 7 is selectively etched using the resist film 11 as a mask to remove the polysilicon film 7 on the portion other than the nonvolatile memory 2. To do.

(E) Next, the resist film 11 is removed, and as shown in FIG. 2E, the surface of the polysilicon film 7 on the non-volatile memory 2 is oxidized to form a second silicon oxide film. The gate insulating film 9 is formed. Incidentally, the thickness of the gate insulating film 5 of the MOS transistor 3 is slightly increased by this oxidation treatment.

FIGS. 3A to 3F show the MOS shown in FIG.
FIG. 9 is a cross-sectional view showing the latter half of the main part of the method for manufacturing a die integrated circuit in order of process. (A) Next, the second gate insulating film 9 is made to contain nitrogen atoms by the nitriding treatment similar to the step of FIG. Figure 3
(A) shows the state after the nitriding treatment of the second gate insulating film 9. (B) Next, as shown in FIG. 3A, by etching the silicon oxide SiO ₂ with the second gate insulating film 9 masked by the resist film 11, the MOS is formed.
The gate insulating film 5 containing nitrogen atoms on the region 3 where the transistor is to be formed is removed.

(C) Next, the resist film 11 is removed, and thereafter, the gate insulating film 6 made of silicon oxide is formed on the region 3 where the MOS transistor is to be formed by heat oxidation.
To form. FIG. 3C shows the state after the gate insulating film 6 is formed. (D) Next, as shown in FIG. 3D, a polysilicon layer 10 to be the control gate of the nonvolatile memory 2 and the gate of the MOS transistor 3 is formed by CVD.

(E) Next, as shown in FIG. 3E, a resist film is formed on the region of the polysilicon layer 10 where the nonvolatile memory 2 is to be formed and the region where the gate of the MOS transistor 2 is to be formed. The gate 8 of the MOS transistor 2 is formed by masking 11 and etching the polysilicon layer 10 in that state. (F) Next, as shown in FIG. 3F, the MOS transistor 2 and the portion of the nonvolatile memory 2 where the control gate is to be formed are masked with a resist film 11.
In that state, the control gate 10 is formed by selectively etching the polysilicon layer. After that, the MOS type integrated circuit shown in FIG. 1 can be obtained by proceeding the manufacturing according to a normal CMOSIC manufacturing process.

FIG. 3 shows an M incorporating the nonvolatile memory of the present invention.
It is sectional drawing which shows the other Example of OS type integrated circuit. The present embodiment is different from the embodiment shown in FIG. 1 only in that the second gate insulating film is made of silicon oxide 9a containing no nitrogen atom. The MOS integrated circuit shown in FIG. 4 can be obtained by omitting the nitriding treatment of the second gate insulating film 9 shown in FIG.

According to the present embodiment, at least the reliability of the first gate insulating film 5 through which the electrons of the non-volatile memory 2 pass by the tunnel effect can be improved, and the reliability of the non-volatile memory can be increased by that much. Can be increased. Note that the second gate insulating film 9a may be formed in a so-called ONO structure in which a silicon oxide film and a nitride film are laminated, or may be formed of a material other than that, and the present invention is implemented in various modes. be able to.

[0025]

According to the present invention, the M including the nonvolatile memory according to claim 1 is incorporated.
In the OS type integrated circuit, at least one of the first gate insulating film and the second gate insulating film of the non-volatile memory contains a nitrogen atom, and the gate insulating film of an ordinary MOS transistor does not contain a nitrogen atom. It is characterized by. Therefore, according to the MOS integrated circuit of claim 1, the gate insulating film containing nitrogen atoms has excellent TDDB characteristics and hot carrier resistance as compared with a gate insulating film not containing nitrogen atoms, and the first gate of the non-volatile memory. Since at least one of the insulating film and the second gate insulating film contains a nitrogen atom, the reliability of the nonvolatile memory can be increased. The performance of the ordinary MOS transistor does not deteriorate because the gate insulating film does not contain nitrogen atoms.

An MO incorporating the non-volatile memory according to claim 2.
The S-type integrated circuit is characterized in that, in the MOS integrated circuit according to claim 1, both the first gate insulating film and the second gate insulating film of the non-volatile memory contain nitrogen atoms. Therefore, according to the MOS integrated circuit of the second aspect, since both the first gate insulating film and the second gate insulating film of the nonvolatile memory contain nitrogen atoms, the reliability of the nonvolatile memory is improved. can do.

An MO incorporating the non-volatile memory of claim 3.
A method of manufacturing an S-type integrated circuit includes a step of forming a gate insulating film containing a nitrogen atom at the same time on a surface of a region where a nonvolatile memory is to be formed and a surface of a region where a MOS transistor is to be formed, and the gate insulating film. A step of forming an electrode to be a first gate and a second gate insulating film covering the surface of the electrode in a portion of the film on a region where a non-volatile memory is to be formed; The method has a step of removing the gate insulating film and forming a gate insulating film containing no nitrogen atom therein. Therefore, according to the method of manufacturing a MOS integrated circuit of claim 3, the surface of the region where the nonvolatile memory is to be formed,
A gate insulating film containing nitrogen atoms is simultaneously formed on the surface of the region where the MOS transistor is to be formed, and an electrode to be the first gate and an electrode to be the first gate are formed in the portion of the gate insulating film above the region where the nonvolatile memory is to be formed. A second gate insulating film covering the gate insulating film is formed, and then the gate insulating film in a region where a normal MOS transistor is to be formed is removed to form a gate insulating film containing no nitrogen atom. The first gate insulating film contains nitrogen atoms,
The gate insulating film of the OS transistor can be prevented from containing nitrogen atoms.

An MO incorporating the non-volatile memory according to claim 4.
The method for manufacturing an S-type integrated circuit is the method for manufacturing a MOS-type integrated circuit according to claim 3, wherein a gate insulating film containing nitrogen atoms is formed as a second gate insulating film covering the surface of the electrode to be the first gate. It is characterized by doing. Therefore, according to the method of manufacturing a MOS integrated circuit of claim 4, since the second gate insulating film covering the electrode serving as the first gate contains nitrogen atoms, the first gate insulating film of the nonvolatile memory is formed. Both the first gate insulating film and the second gate insulating film can contain nitrogen atoms, and the reliability of the nonvolatile memory can be further improved.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing one embodiment of a MOS type integrated circuit incorporating a nonvolatile memory of the present invention.

2A to 2E are cross-sectional views showing, in the order of steps, the first half of the main part of the method for manufacturing the MOS integrated circuit shown in FIG.

3A to 3F are cross-sectional views showing the latter half of the main part of the method for manufacturing the MOS integrated circuit shown in FIG. 1 in process order.

FIG. 4 is a sectional view showing another embodiment of a MOS type integrated circuit incorporating the nonvolatile memory of the present invention.

FIG. 5 is a plan view of a MOS integrated circuit including a nonvolatile memory.

[Explanation of symbols]

 1 semiconductor substrate 2 non-volatile memory 3 MOS transistor 4 field insulating film 5 first gate insulating film 6 gate insulating film of MOS transistor 7 first gate (floating gate) 8 gate 9, 9a second gate insulating film 10 2 gates (control gate)

Claims (4)

[Claims] 1. A first gate is formed on a first gate insulating film, and a second gate insulating film is formed on the first gate insulating film to form a second gate insulating film.
M with a built-in non-volatile memory with the structure of the gate
In the OS type integrated circuit, at least one of the first gate insulating film and the second gate insulating film of the nonvolatile memory contains a nitrogen atom, and the gate insulating film of an ordinary MOS transistor does not contain a nitrogen atom. MOS type integrated circuit having a built-in nonvolatile memory 2. The MOS integrated circuit according to claim 1, wherein both the first gate insulating film and the second gate insulating film of the non-volatile memory contain nitrogen atoms. 3. A gate insulating film containing a nitrogen atom is simultaneously formed on the surface of a region where a nonvolatile memory is to be formed, which is surrounded by a field insulating film of a semiconductor substrate, and on the surface of a region where an ordinary MOS transistor is to be formed at the same time. A step of forming, a step of forming an electrode to be the first gate and a second gate insulating film covering the surface of the electrode in a portion of the gate insulating film on a region where the nonvolatile memory is to be formed, A step of removing a gate insulating film in a region where a MOS transistor is to be formed and forming a gate insulating film containing no nitrogen atom therein; Production method 4. The non-volatile memory according to claim 3, wherein a gate insulating film containing nitrogen atoms is formed as a second gate insulating film covering the surface of the electrode to be the first gate. Method for manufacturing MOS integrated circuit