JP2009267027A - Semiconductor device, and method for manufacturing thereof - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a semiconductor device which can suppress the generation of anomalous leak caused by a parasitic transistor and obtain a normal electrical property, and to provide a method for manufacturing thereof. <P>SOLUTION: The method of manufacturing a semiconductor device includes the steps of forming a LOCOS oxide film 2 on a silicon substrate into which boron ions are introduced, forming a P-type impurity diffusion layer 3 on the end of an active region 1a by implanting boron ions into the end including a channel forming region of the active region 1a located inside the oxide film 2, forming a gate insulating film on the active region 1a of the silicon substrate, forming a gate electrode 6 on the P-type impurity diffusion layer 3 and the active region 1a via the gate insulating film, and forming a diffusion layer 7 of a source-drain region on the active region by ion-implanting impurities using the LOCOS oxide film 2 and the gate electrode 6 as masks. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a semiconductor device capable of suppressing the occurrence of abnormal leakage due to a parasitic transistor and a method for manufacturing the same.

  A parasitic transistor may be formed on the gate electrode at the end of the active region isolated by the LOCOS oxide film or STI. This is because boron ions implanted in the active region are sucked into the LOCOS oxide film or the like by LOCOS oxidation or STI formation, and as a result, the boron ion concentration under the gate electrode at the end of the active region is reduced. (For example, see Patent Document 1). A conventional semiconductor device in which a parasitic transistor due to this cause is formed includes a LOCOS isolation type or STI isolation type NMOS transistor formed on a P-type silicon substrate or an SOI (Silicon on Insulator) substrate.

Japanese Patent No. 3184348 (paragraphs 0016 to 0018)

  As described above, in the conventional semiconductor device, boron ions existing at the end of the active region are sucked into the LOCOS oxide film or the like by thermal oxidation, and due to impurity redistribution, in the channel region under the gate electrode at the end of the active region. Boron concentration may decrease abnormally. As a result, a parasitic MOS transistor is formed at the end of the active region, the threshold voltage of the parasitic MOS transistor is lower than the threshold voltage of the transistor in the active region, and the parasitic MOS transistor is turned on in the off region of the transistor in the active region. May end up. This can cause abnormal leakage between the source and drain in the off region of the transistor.

  The present invention has been made in consideration of the above circumstances, and an object of the present invention is to provide a semiconductor device capable of suppressing the occurrence of abnormal leakage due to a parasitic transistor and obtaining normal electrical characteristics, and a method for manufacturing the same. It is to provide.

In order to solve the above problems, a method of manufacturing a semiconductor device according to the present invention includes a step of forming an element isolation film on a semiconductor substrate into which boron ions are introduced,
Forming a P-type impurity region at the end portion of the active region by implanting boron ions into the end portion including the channel formation region in the active region located inside the element isolation film;
Forming a gate insulating film on the active region of the semiconductor substrate;
Forming a gate electrode on the P-type impurity region and the active region via the gate insulating film;
Forming a diffusion layer of a source / drain region in the active region by ion-implanting impurities using the device isolation film and the gate electrode as a mask;
It is characterized by comprising.

  According to the method for manufacturing a semiconductor device, boron ions are implanted into an end portion of the active region including the channel formation region, thereby forming a P-type impurity region at the end portion of the active region. Thereby, the boron concentration at the end of the active region where the boron concentration is lowered by the thermal oxidation for forming the element isolation film can be increased to the concentration before the element isolation film is formed. Therefore, it is possible to suppress a decrease in boron concentration due to boron absorption into the element isolation film generated at the end of the active region. As a result, a parasitic MOS transistor having a lowered threshold voltage is formed at the end of the active region, and abnormal leakage between the source and drain in the off region of the transistor due to the parasitic MOS transistor being turned on is generated. Can be suppressed.

  Moreover, in the method for manufacturing a semiconductor device according to the present invention, the planar shape of the active region may be a shape in which a rectangular corner is notched. Thereby, the area of the P-type impurity region can be reduced. For this reason, it is possible to suppress the diffusion of boron ions to the effective channel portion, and as a result, it is possible to suppress an increase in the threshold voltage of the transistor in the active region and a decrease in the effective channel width.

  In the method of manufacturing a semiconductor device according to the present invention, the P-type impurity region can be completely covered with the gate electrode. Thereby, the current path between the source and the drain can be limited, and the effective channel width W can be almost determined.

  In the semiconductor device manufacturing method according to the present invention, the active region may have a rectangular planar shape, and the P-type impurity region may be formed inside a corner of the active region. Thereby, the area of the P-type impurity region can be reduced. Therefore, diffusion of boron ions to the effective channel portion can be suppressed, and as a result, an increase in the threshold voltage of the transistor in the active region and a decrease in the effective channel width can be suppressed.

In the method for manufacturing a semiconductor device according to the present invention, the semiconductor substrate may be an SOI type semiconductor substrate.
In the method for manufacturing a semiconductor device according to the present invention, the element isolation film may be a LOCOS oxide film or an STI.

A semiconductor device according to the present invention includes an element isolation film formed on a semiconductor substrate into which boron ions are introduced,
An active region formed inside the device isolation film;
A P-type impurity region formed by implanting boron ions into an end portion including a channel formation region in the active region;
A gate insulating film formed on the active region of the semiconductor substrate;
A gate electrode formed on the P-type impurity region and the active region via the gate insulating film;
A diffusion layer of a source / drain region formed in the active region;
It is characterized by comprising.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIGS. 1A to 1D are plan views for explaining a method for manufacturing a semiconductor device according to the first embodiment of the present invention. 2A to 2D are cross-sectional views taken along the line AA ′ shown in FIGS.

  First, as shown in FIGS. 1A and 2A, boron ions are implanted into the silicon substrate 1 to form a P-type well region 11 in the silicon substrate 1. Thereafter, a LOCOS oxide film 2 as an element isolation film is formed on the silicon substrate 1 by the LOCOS method. As a result, an active region 1 a located inside the LOCOS oxide film 2 is formed in the silicon substrate 1. Here, when the silicon substrate 1 is thermally oxidized to form the LOCOS oxide film 2, boron ions existing at the end of the active region 1a are sucked into the LOCOS oxide film 2 by this thermal oxidation, and as a result, The boron concentration at the end of the active region 1a decreases.

  Thereafter, as shown in FIGS. 1B and 2B, a resist pattern 4 is formed on the silicon substrate 1 by photolithography so that the end of the active region 1a is opened.

  Next, boron ions are implanted into the silicon substrate 1 using the resist pattern 4 and the LOCOS oxide film 2 as a mask, and then the resist pattern 4 is peeled off. Next, boron ions implanted into the silicon substrate 1 are diffused by heat treatment. As a result, the P-type impurity diffusion layer 3 is formed at the end of the active region 1a including the channel formation region. That is, since boron ions are implanted into the end portion of the active region 1a whose boron concentration has been lowered by the thermal oxidation for forming the LOCOS oxide film 2 described above in the process shown in FIG. 2B, boron at the end portion of the active region 1a is formed. The concentration can be increased to a concentration before the LOCOS oxide film 2 is formed. Note that the boron concentration of the P-type impurity diffusion layer 3 may be equal to or higher than the concentration before the LOCOS oxide film 2 is formed.

  Next, as shown in FIGS. 1C and 2C, a gate oxide film to be the gate insulating film 5 is formed in the active region 1a of the silicon substrate 1 by a thermal oxidation method. Next, a polysilicon film is formed on the gate insulating film 5 and the LOCOS oxide film 2 by a CVD (Chemical Vapor Deposition) method, and this polysilicon film is processed using a photolithography method and a dry etching method. Thereby, the gate electrode 6 is formed on the gate insulating film 5.

  Thereafter, as shown in FIGS. 1D and 2D, impurity ions are ion-implanted using the gate electrode 6 and the LOCOS oxide film 2 as a mask, and the silicon substrate 1 is heat-treated. Thereby, the diffusion layer 7 of the source / drain region is formed in the silicon substrate 1 shown in FIG.

  As described above, according to the first embodiment of the present invention, boron ions are implanted into the end portion of the active region 1a including the channel region under the gate electrode 6 in the steps shown in FIGS. 1B and 2B. As a result, the P-type impurity diffusion layer 3 is formed at the end of the active region 1a. As a result, the boron concentration at the end of the active region 1a where the boron concentration is reduced by the thermal oxidation for forming the LOCOS oxide film 2 can be increased to the concentration before the LOCOS oxide film 2 is formed. Therefore, it is possible to suppress a decrease in boron concentration due to boron suction into the LOCOS oxide film 2 generated at the end of the active region 1a. As a result, a parasitic MOS transistor having a lowered threshold voltage is formed at the end of the active region, and abnormal leakage between the source and drain in the off region of the transistor due to the parasitic MOS transistor being turned on is generated. Can be suppressed.

  Next, a method for manufacturing a semiconductor device according to the second embodiment of the present invention will be described with reference to FIGS.

  First, as shown in FIG. 3A, boron ions are implanted into a silicon substrate to form a P-type well region in the silicon substrate. Thereafter, a LOCOS oxide film 2a as an element isolation film is formed on the silicon substrate by the LOCOS method. Thereby, an active region located inside the LOCOS oxide film 2a is formed on the silicon substrate. At this time, the active region located inside the LOCOS oxide film 2a is formed to have a shape in which four corners of the active region 1a shown in FIG. Thereafter, a resist pattern 4a is formed on the silicon substrate by photolithography so that the end of the active region is opened.

  Next, boron ions are implanted into the silicon substrate using the resist pattern 4a and the LOCOS oxide film 2a as a mask, and then the resist pattern 4a is peeled off. Next, boron ions implanted into the silicon substrate are diffused by heat treatment. As a result, a P-type impurity diffusion layer 3a is formed at the end of the active region including the channel formation region. This P-type impurity diffusion layer 3a is compared with the P-type impurity diffusion layer 3 shown in FIG. The area has been reduced. It should be noted that the boron concentration of the P-type impurity diffusion layer 3a may be higher than the concentration before the LOCOS oxide film 2 is formed.

  Next, as shown in FIG. 3B, a gate oxide film to be the gate insulating film 5a is formed in the active region of the silicon substrate by a thermal oxidation method. Next, a polysilicon film is formed on the gate insulating film 5a and the LOCOS oxide film 2a by a CVD method, and this polysilicon film is processed using a photolithography method and a dry etching method. Thereby, the gate electrode 6a is formed on the gate insulating film 5a.

  Thereafter, as shown in FIG. 3C, impurity ions are ion-implanted using the gate electrode 6a and the LOCOS oxide film 2a as a mask, and the silicon substrate is heat-treated. Thereby, the diffusion layer 7a of the source / drain region is formed in the silicon substrate.

  As described above, also in the second embodiment of the present invention, the same effect as that of the first embodiment can be obtained. Further, since the active region shown in FIG. 3A has a shape in which four corners of the active region 1a shown in FIG. 1A are cut out, boron ions are additionally implanted into the active region of this shape. The area of the P-type impurity diffusion layer 3a can be reduced. Thereby, the diffusion of boron ions to the effective channel portion can be suppressed as compared with the P-type impurity diffusion layer 3 shown in FIG. As a result, an increase in threshold voltage and a decrease in effective channel width of the transistors in the active region can be suppressed.

  Next, a method for manufacturing a semiconductor device according to the third embodiment of the present invention will be described with reference to FIGS.

  First, as shown in FIG. 4A, boron ions are implanted into a silicon substrate to form a P-type well region in the silicon substrate. Thereafter, a LOCOS oxide film 2b as an element isolation film is formed on the silicon substrate by the LOCOS method. Thereby, an active region located inside the LOCOS oxide film 2b is formed on the silicon substrate. At this time, the active region located inside the LOCOS oxide film 2b is formed to have a shape in which the four corners of the active region shown in FIG. Thereafter, a resist pattern 4b is formed on the silicon substrate by photolithography so that the end of the active region is opened.

  Next, using the resist pattern 4b and the LOCOS oxide film 2b as a mask, boron ions are implanted into the silicon substrate, and then the resist pattern 4b is peeled off. Next, boron ions implanted into the silicon substrate are diffused by heat treatment. As a result, the P-type impurity diffusion layer 3b is formed at the end of the active region that is narrower than the gate length L of the channel formation region. The length l of the P-type impurity diffusion layer 3b is formed smaller than the gate length L (see FIG. 4B). Note that the boron concentration of the P-type impurity diffusion layer 3b may be equal to or higher than the concentration before the LOCOS oxide film 2 is formed.

  Next, as shown in FIG. 4B, a gate oxide film to be the gate insulating film 5b is formed in the active region of the silicon substrate by a thermal oxidation method. Next, a polysilicon film is formed on the gate insulating film 5b and the LOCOS oxide film 2b by a CVD method, and this polysilicon film is processed using a photolithography method and a dry etching method. Thereby, the gate electrode 6b is formed on the gate insulating film 5b. At this time, the gate electrode 6b is formed so as to cover the P-type impurity region 3b at the end of the active region.

  Thereafter, as shown in FIG. 4C, impurity ions are ion-implanted using the gate electrode 6b and the LOCOS oxide film 2b as a mask, and the silicon substrate is heat-treated. Thereby, the diffusion layer 7b of the source / drain region is formed in the silicon substrate.

  As described above, also in the third embodiment of the present invention, the same effect as in the second embodiment can be obtained. Further, the four corners of the active region shown in FIG. 4 (a) are cut out to be larger than those in FIG. 3 (a), and boron ions are additionally implanted into the active region having this shape. Impurity diffusion layer 3b is positioned inside gate electrode 6b, and P-type impurity diffusion layer 3b is completely covered by gate electrode 6b. That is, the length 1 of the P-type impurity diffusion layer 3b is made smaller than the gate length L. Thereby, the current path between the source and the drain can be limited, and the effective channel width W can be almost determined.

  Next, the manufacture of the semiconductor device according to the fourth embodiment of the present invention will be described with reference to FIGS.

  First, as shown in FIG. 5A, boron ions are implanted into a silicon substrate to form a P-type well region in the silicon substrate. Thereafter, a LOCOS oxide film 2c as an element isolation film is formed on the silicon substrate by the LOCOS method. Thereby, an active region located inside the LOCOS oxide film 2c is formed on the silicon substrate. Thereafter, a resist pattern 4c is formed by photolithography so that the end of the active region is opened in the silicon substrate.

  Next, using the resist pattern 4c and the LOCOS oxide film 2c as a mask, boron ions are implanted into the silicon substrate, and then the resist pattern 4c is peeled off. Next, boron ions implanted into the silicon substrate are diffused by heat treatment. As a result, a P-type impurity diffusion layer 3c is formed at the end of the active region including the channel formation region, and this P-type impurity diffusion layer 3c is compared with the P-type impurity diffusion layer 3 shown in FIG. The area has been reduced. Note that the boron concentration of the P-type impurity diffusion layer 3c may be equal to or higher than the concentration before the LOCOS oxide film 2 is formed.

  Next, as shown in FIG. 5B, a gate oxide film to be the gate insulating film 5c is formed in the active region of the silicon substrate 1 by a thermal oxidation method. Next, a polysilicon film is formed on the gate insulating film 5c and the LOCOS oxide film 2c by a CVD method, and this polysilicon film is processed using a photolithography method and a dry etching method. Thereby, the gate electrode 6c is formed on the gate insulating film 5c. At this time, the gate electrode 6c is located on the P-type impurity diffusion layer 3c at the end of the active region.

  Thereafter, as shown in FIG. 5C, impurity ions are ion-implanted using the gate electrode 6c and the LOCOS oxide film 2c as a mask, and the silicon substrate 1 is subjected to heat treatment. As a result, the diffusion layer 7 c of the source / drain region is formed in the silicon substrate 1.

  As described above, also in the fourth embodiment of the present invention, the same effect as that of the first embodiment can be obtained. Furthermore, by reducing the area of the P-type impurity diffusion layer 3c, the diffusion of boron ions to the effective channel portion can be suppressed as compared with the P-type impurity diffusion layer 3 shown in FIG. As a result, an increase in threshold voltage and a decrease in effective channel width of the transistors in the active region can be suppressed.

  Next, a method for manufacturing a semiconductor device according to the fifth embodiment of the present invention will be described with reference to FIG.

  As shown in FIG. 6, the LOCOS oxide film 2d, the P-type impurity region 3d at the end of the active region, on the SOI layer 8 of the SOI type semiconductor substrate in which the support substrate 10, the BOX layer 9, and the SOI layer 8 are sequentially stacked. The gate insulating film 5d, the gate electrode 6d, and the diffusion layers of the source / drain regions are formed by any of the methods of the first to fourth embodiments.

  As described above, also in the fifth embodiment of the present invention, the same effect as any one of the first to fourth embodiments can be obtained.

  The present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the spirit of the present invention. For example, in the first to fifth embodiments, the element isolation region is LOCOS type isolation, but the element isolation region may be STI (Shallow Trench Isolation) type isolation.

Each figure is a plan view for explaining the method for manufacturing the semiconductor device according to the first embodiment. Each drawing is a sectional view for explaining the method for manufacturing the semiconductor device according to the first embodiment. Each drawing is a plan view for explaining the method for manufacturing the semiconductor device according to the second embodiment. Each figure is a plan view for explaining the method for manufacturing a semiconductor device according to the third embodiment. Each drawing is a plan view for explaining the method for manufacturing a semiconductor device according to the fourth embodiment. Sectional drawing for demonstrating the manufacturing method of the semiconductor device which concerns on 5th Embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Silicon substrate, 2, 2a, 2b, 2c, 2d ... LOCOS oxide film, 3, 3a, 3b, 3c, 3d ... P-type impurity diffusion layer, 4, 4a, 4b, 4c, 4d ... Resist pattern, 5, 5a, 5b, 5c, 5d ... Gate insulating film, 6, 6a, 6b, 6c, 6d ... Gate electrode, 7, 7a, 7b, 7c, 7d ... Source Drain region, 8 ... SOI layer, 9 ... BOX layer, 10 ... support substrate, 11 ... well region

Claims (7)

Forming an element isolation film on a semiconductor substrate into which boron ions have been introduced;
Forming a P-type impurity region at the end portion of the active region by implanting boron ions into the end portion including the channel formation region in the active region located inside the element isolation film;
Forming a gate insulating film on the active region of the semiconductor substrate;
Forming a gate electrode on the P-type impurity region and the active region via the gate insulating film;
Forming a diffusion layer of a source / drain region in the active region by ion-implanting impurities using the element isolation film and the gate electrode as a mask;
A method for manufacturing a semiconductor device, comprising:   2. The method of manufacturing a semiconductor device according to claim 1, wherein the planar shape of the active region is a shape in which a rectangular corner is cut out.   3. The method of manufacturing a semiconductor device according to claim 1, wherein the P-type impurity region is completely covered with the gate electrode.   2. The method of manufacturing a semiconductor device according to claim 1, wherein the planar shape of the active region is a rectangle, and the P-type impurity region is formed inside a corner of the active region.   5. The method for manufacturing a semiconductor device according to claim 1, wherein the semiconductor substrate is an SOI type semiconductor substrate.   6. The method of manufacturing a semiconductor device according to claim 1, wherein the element isolation film is a LOCOS oxide film or an STI. An element isolation film formed on a semiconductor substrate into which boron ions have been introduced;
An active region formed inside the device isolation film;
A P-type impurity region formed by implanting boron ions into an end portion including a channel formation region in the active region;
A gate insulating film formed on the active region of the semiconductor substrate;
A gate electrode formed on the P-type impurity region and the active region via the gate insulating film;
A diffusion layer of a source / drain region formed in the active region;
A semiconductor device comprising:

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