JPH0661252A - Semiconductor device and its manufacture - Google Patents

Abstract

PURPOSE:To restrain a trapping center of carrier from being newly generated through implantation of hot carriers to a gate oxide film in a semiconductor device such as an MOSFET and its manufacturing method. CONSTITUTION:Hydrogen, hydrogen compound, halogen or halogen compound are introduced to a main surface of a semiconductor substrate 1 by an ion implantation device before or after formation of a gate oxide film 4; thereby, density of interface level, fixed charge, trapping center, etc., is reduced and formation of new structural defect due to implantation of hot carrier to the gate oxide film 4 is restrained. A semiconductor device such as an MOSFET having less variation of a gate threshold voltage, that is, resistant to deterioration due to hot carriers is acquired by using the gate oxide film 4.

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 a method for manufacturing the same, and more particularly to a technique for preventing malfunction due to hot carriers.

[0002]

2. Description of the Related Art A MOS (Metal Oxide Semiconductor) transistor is composed of a source and a drain (both 10 '), a gate oxide film 4 and a gate electrode 5, as shown in FIG.

Next, the manufacturing process will be described with reference to FIG. In the figure, 1 is a semiconductor substrate, 2 is a LOCOS oxide film formed by LOCOS-oxidizing the surface of the semiconductor substrate 1, 3 is channel ion implantation performed on the semiconductor surface between the LOCOS oxide films 2, and 4 is the channel ion. After implantation, a gate oxide film 5 obtained by oxidizing the surface of the semiconductor substrate is a polysilicon gate electrode formed on the gate oxide film 4,
6 is N- drain ion implantation, 7 is a low concentration N- source / drain region formed by the N- drain ion implantation, 8 is a sidewall film formed on the gate electrode 5, and 9 is N + drain ion implantation. 10 'is an N + source / drain region. The N− source / drain region 7 in FIG. 5 (d) is the N + source / drain region 1.
It forms an LDD (Lightly Doped Drain) structure together with 0 '.

As shown in FIG. 5A, first, the semiconductor substrate 1
After forming the LOCOS oxide film 2 thereon, channel ion implantation 3 is performed. Then, after forming the gate oxide film 4 (FIG. 5B), a polysilicon gate electrode 5 is deposited, the polysilicon gate electrode 5 is patterned together with the gate oxide film 4, and then N- drain implantation 6 is performed. (Fig. 5
(c)), N-source / drain regions 7 are formed.

Next, a sidewall film 8 is formed by depositing an insulating film on the entire surface and then etching it, and then N + drain ion implantation 9 is performed to form an N + source / drain region 10 '. Together with the N- drain region 7, the basic structure of the n-type MOSFET having the LDD structure is formed.

In order to realize a high-density integrated circuit, elements are being miniaturized, but the operating voltage of the elements is TTL.
Since it is fixed at 5V or 3.3V which is the (Transistor-Transistor Logic) level, the electric field in the gate oxide film or the substrate is effectively increased with the miniaturization of the element. Therefore, the carriers (electrons or holes) traveling in the substrate under the gate oxide film 4 are accelerated by the electric field and have high kinetic energy, and some of them cross over the energy barrier of the substrate / oxide film interface during channel traveling. It is captured in the gate oxide film 4. This kind of carrier is CH
It is called E (Channel Hot Electron). In addition to this, carriers with high energy that have reached the drain collide with impurity atoms to newly generate electron-hole pairs, and a part of them crosses over the energy barrier at the substrate / oxide film interface and the gate oxide film 5 is formed. Captured inside. This type of carrier is called DAHC (Drain Avalanche Hot Carrier).

In the oxide film 4, in addition to the trap centers described above, interface states, interface sources / fixed charges and mobile ions are present. This state is shown in FIG. 4 is a gate oxide film, 1
0 is sodium ion Na +, 11 is potassium ion K
+ And 16 (Qm) are mobile ions such as sodium ion Na + potassium ion K +. 13 (Qo) is a fixed charge. 14 (Qi) is an interface state. 12 (Q
t) is the above CHE (Channel Hot Electron) or D
AHC (Drain Avalanche Hot Carrier) is a trapping center formed by being trapped in the gate oxide film 5 over the energy barrier at the substrate / oxide film interface. Above interface level 1
4 (Qi) is distorted Si-O bond or unsaturated bond of silicon

[0008]

[Chemical 1]

The cause is. The mobile ions 16 are alkaline ions such as sodium ions (Na +) and potassium ions (K +). These charges are related to the electrical characteristics of the MOS transistor. The electrical characteristics of the MOS transistor are given by the following equation in the triode region.

ID = W / L.μCox (VG-VT) VD (1)

Where ID is drain current, W is gate width, L is gate length, μ is mobility, Cox is gate capacitance, and V is
G is a gate voltage, VT is a gate threshold voltage, and VD is a drain voltage. The basic characteristic of this MOSFET is shown by the characteristic (17) in FIG. In the case of an n-type MOS transistor, when the fixed charge Qo is generated at the interface, the gate threshold voltage VT is Q due to the influence of the electric flux generated from the fixed charge.
It decreases by o / Cox, and the ID-VG characteristic shifts to the negative side of the gate voltage as shown by the characteristic (18) in FIG. Further, when the interface state Qi is generated, the interface state captures a part of the free carriers and the amount of charge that can move freely is reduced, so that the mutual conductance is reduced as shown by the characteristic (19) in FIG. . Since the charge has a distribution ρ (x) in the thickness direction in the oxide film, the gate threshold voltage is as follows.

[0012]

[Equation 1]

Here, φMS is the work function difference between semiconductor and metal, tox is the gate oxide film thickness, QD is the inversion layer charge, QB is the depletion layer charge, Cox is the gate oxide film capacitance, and φF is the Fermi potential. When the trap center Qt (12) is in the oxide film, when the trap center captures an electron that has passed through the energy barrier of the silicon substrate / oxide interface, the trap center becomes a negative charge state and the gate threshold is reached. The value voltage fluctuates according to equation (2).

Part of the carriers that have overcome the energy barrier at the silicon substrate / oxide film (SiO2) interface are trapped by the trap centers distributed in the oxide film. The capture center is
Known are (1) trap centers due to moisture, (2) trap centers by high temperature heat treatment, and (3) trap centers generated by carrier injection into the oxide film. Moisture in oxide film (H2
O) reacts with (Si-O-Si) at high temperature to form SiOH
It produces structural defects such as (silanol) and SiH. Among them, it is reported that SiOH acts as a trap center for electrons, but SiH does not serve as a trap center for carriers. Further, it has been reported that the capture center of SiOH is remarkably reduced when heat-treated in a non-oxidizing atmosphere at 1000 ° C. or higher, and in a normal manufacturing process of a MOS transistor on a silicon wafer, after the gate oxide film is formed, a poly-silicon is trapped at a high temperature. Since silicon is deposited, it is considered that the trap centers caused by water will almost disappear. On the other hand, after the OH groups and oxygen ions in the oxide film are removed by the high temperature heat treatment, unsaturated bonds of the silicon atoms, chemical formula 1 and oxygen vacancies

[0015]

[Chemical 2]

A structural defect due to is generated. This structural defect acts as a trap center for electrons. In addition to these, as the trapping centers by the high temperature heat treatment, there are trapping centers by the distorted Si—O bond existing near the silicon substrate / oxide film interface. This trapping center acts on holes. The trap centers formed by the high temperature heat treatment increase in density when the high temperature heat treatment is performed in a non-oxidizing atmosphere. In addition to this, when carriers are injected into the oxide film, unsaturated silicon atoms increase in the vicinity of the interface, and XPS (X-ray Photoemission Spec.
troscopy) measurement.

In the conventional MOS transistor manufacturing process, it is known that the interface state and the fixed charge on the interface are significantly reduced by heat treatment in a hydrogen atmosphere before forming the gate oxide film. By this processing, the initial operation of the MOS transistor can be controlled by the gate electrode without being affected by the interface state or the interface fixed charge, and the variation in the gate threshold voltage within the wafer is reduced. However, when hot carriers are injected into the gate oxide film, unsaturated silicon atoms are generated near the silicon substrate / oxide film interface. Therefore, the gate threshold voltage fluctuates over time, which causes a malfunction.

[0018]

The conventional semiconductor device and the method of manufacturing the same are configured as described above. When the element is miniaturized, the electric field in the semiconductor substrate becomes high, and the carriers are accelerated by the electric field. You will get high energy. When the high energy exceeds the energy barrier between the semiconductor substrate and the oxide film, a carrier trap center by unsaturated silicon atoms is newly formed in the vicinity of the interface between the semiconductor substrate and the oxide film, which deteriorates the operation of the semiconductor device. There was a problem of being connected.

Further, the interface level and the interface fixed charge that change the gate threshold value are greatly reduced by introducing hydrogen by flowing hydrogen at a high temperature in a furnace in a non-oxidizing atmosphere before the gate oxidation. be able to. However, this method has the problem that it is difficult to control the distribution of hydrogen in the silicon substrate and the concentration to be introduced, and this method also makes it difficult to introduce hydrogen at a high concentration near the silicon substrate / oxide film interface. In addition, there is a problem in that the injection of hot carriers allows the generation of new trapping centers.

The present invention has been made in order to solve the above problems, and even when it is operated for a long period of time, the carrier is injected into the oxide film, so that the semiconductor substrate / oxide film interface is unsaturated. An object of the present invention is to provide a semiconductor device having resistance to deterioration of operation due to generation of silicon and a method for manufacturing the same.

[0021]

According to a first aspect of the present invention, there is provided a semiconductor device manufacturing method, wherein hydrogen, a hydrogen compound, halogen or a halogen compound is ion-implanted into a main surface of a semiconductor wafer before forming an oxide film on the main surface. It is characterized by being introduced by a device. The method of manufacturing a semiconductor device according to a second aspect is characterized in that after forming an oxide film on the main surface of the semiconductor wafer, hydrogen, hydrogen compound, halogen or halogen compound is introduced into the main surface.

The method of manufacturing a semiconductor device according to a third aspect is characterized in that the introduction of the second aspect is performed by an ion implantation device.
A method for manufacturing a semiconductor device according to claim 4 is the method according to claim 1 or 3.
The ion implantation apparatus described above is characterized in that the ion acceleration energy is 10 KeV or less.
According to a fifth aspect of the present invention, there is provided a method of manufacturing a semiconductor device, wherein the ion implantation apparatus according to the third aspect introduces an ion beam having an incident angle of 3 degrees.
It is characterized in that it is carried out while rotating the wafer at 0 ° to 60 °.

According to a sixth aspect of the present invention, there is provided a method of manufacturing a semiconductor device, wherein the ion implantation is performed by depositing a film on an oxide film and introducing the ion implantation device into the oxide film through the laminated film. Is characterized by. A semiconductor device manufacturing method according to a seventh aspect is characterized in that the introduction according to the second aspect is introduced in a furnace in a non-oxidizing atmosphere after forming the gate oxide film. A semiconductor device according to claim 8 is the semiconductor device according to any one of claims 1 to 7.
Manufactured by any of the above methods, and has the oxide film as a gate oxide film.

[0024]

In the present invention, since hydrogen, hydrogen compound, halogen, or halogen compound is introduced into the semiconductor substrate / oxide film interface and into the oxide film, the interface state, fixed charge, trapping in the oxide film are introduced. Decrease the concentration of the core,
At the same time, it is possible to suppress the generation of new trap centers by injecting hot carriers into the oxide film.

[0025]

EXAMPLES Example 1. A method of manufacturing a semiconductor device according to an embodiment of the present invention will be described below with reference to the drawings. In FIG. 1, the same symbols as those in FIG. 5 indicate the same or corresponding portions.
1 is hydrogen, a hydrogen compound, a halogen, or a halogen compound. Next, the manufacturing method will be described. First, as shown in FIG. 1A, a LOCOS oxide film 2 is formed on a Si semiconductor substrate 1. Next, as shown in FIG. 1B, hydrogen is ion-implanted at an energy of 5 KeV and a dose of 1.0 × 10 ¹⁵ / cm ² with an incident angle of 7 ° without rotating the wafer. Next, as shown in FIG. 1C, a gate oxide film 4 having a film thickness of about 10 nm is formed by dry oxidation at 800 ° C. for 20 minutes, for example.

By injecting hydrogen before gate oxidation, hydrogen is taken into the oxide film during gate oxidation. On the oxide film side of the silicon substrate / oxide film interface, there are a large number of unsaturated silicon atoms (Chemical formula 1) that cause structural defects, including trap centers formed by injection of hot carriers into the oxide film. This forms SiH because many hydrogen ions are present at the interface. Since this structural defect does not serve as a center for capturing carriers, fluctuations in the threshold voltage of the gate can be suppressed. Also, near the interface, distorted Si-
When the O bond is broken, at the same time as the unsaturated silicon atom (・
O-Si) is also generated. When electrons are injected into the oxide film, neutral structural defects (.O-Si) act as electron trap centers, but there are many hydrogen ions (HO).
-Si) is formed, carrier capture is suppressed, and fluctuations in the threshold voltage of the gate are reduced. In the above,
I have explained hydrogen as an example, but hydrogen compounds, halogens,
Alternatively, the same effect can be obtained by introducing a halogen compound.

As a method of introducing hydrogen into the silicon substrate before the gate oxidation, there is a method of flowing hydrogen at a high temperature in a furnace in a non-oxidizing atmosphere. In this method, the distribution of hydrogen in the silicon substrate and the concentration to be introduced. However, the ion implantation method as in this embodiment has the advantage that the ion implantation energy and dose can be accurately controlled.

Example 2. Next, a second embodiment of the present invention will be described with reference to FIG. In the above embodiment, since hydrogen is injected before the gate oxidation, there is a problem that the hydrogen affects the formation of the gate oxide film depending on the concentration of the injected hydrogen. In this embodiment, in order to avoid this, after forming the gate oxide film, hydrogen, a hydrogen compound, or halogen, a halogen compound is introduced into the gate oxide film by an ion implantation machine.

That is, as shown in FIG.
After forming the OCOS oxide film 2, the gate oxide film 4 is formed. Then, the gate oxide film 4 is formed by the ion implantation device.
Inject hydrogen into the inside with an incident angle of 7 ° (21)
(Fig. 2 (b)). Although not shown in the figure, for the same reason, hydrogen may be introduced by flowing hydrogen in a furnace in a non-oxidizing atmosphere after forming the gate oxide film 4, for example.

In the second embodiment, hydrogen is injected before or after the gate oxidation, which is different from the first embodiment. However, the same effect as that of the first embodiment can be obtained. That is,
In the second embodiment, since hydrogen is injected after the gate oxide film is formed, the hydrogen is taken into the oxide film. On the oxide film side of the silicon substrate / oxide film interface, there are a large number of unsaturated silicon atoms (Chemical Formula 1) that cause structural defects, but since many hydrogen ions are present on the interface, SiH is formed. . Since this structural defect does not serve as a center for capturing carriers, fluctuations in the threshold voltage of the gate can be suppressed. Also,
Near the interface, when the distorted Si-O bond is broken, (.O-Si) is also formed at the same time as the unsaturated silicon atom. When electrons are injected into the oxide film, neutral structural defects (・
(O-Si) acts as an electron trap center, but (H-O-Si) is formed due to the large number of hydrogen ions present, carrier trapping is suppressed, and fluctuations in the threshold voltage of the gate are reduced. .

Example 3. Next, a third embodiment of the present invention will be described with reference to FIG. When, for example, hydrogen is introduced into the gate oxide film 4, since the gate oxide film thickness 4 is about 10 nm, energy of 5 K is required for distribution in the oxide film 4.
It must be below eV. In Examples 1 and 2, hydrogen was introduced by the ion implanter without increasing the incident angle, but with the ion implanter, the energy was 5 KeV.
Since the degree is the lower limit, it is difficult to inject into a shallower distribution than that at the time of implantation at 5 KeV. In this example,
In order to avoid this, the incident angle is set to, for example, 30 ° to 6
Ions are implanted while rotating the wafer at about 0 °.

That is, in FIG. 3A, the semiconductor substrate 1 has a LOC.
After forming the OS oxide film 2, for example, hydrogen is used as energy 5
Implantation is carried out while rotating the wafer (indicated by arrow 21) at KeV, dose amount of 1.0 × 10 ¹⁴ / cm ² , and incident angle of 60 °. In FIG. 3B, after forming the gate oxide film 4, similar ion implantation (shown by the arrow 21) is performed. In this example, since the implantation is performed at an incident angle of 60 °, it is possible to obtain a shallower distribution than when the implantation is performed at an incident angle of 7 °, and it is possible to distribute the above-described introduced substances in the gate oxide film 4 as designed. .

Example 4. Next, a fourth embodiment of the present invention will be described with reference to FIG. In this embodiment, after forming the gate oxide film 4 and depositing the polysilicon electrode 5, for example, hydrogen is injected at about 10 KeV and an incident angle of 7 °. In this case, since the implantation is performed through the polysilicon gate electrode 5, hydrogen can be implanted into the gate oxide film 4 with the energy of 5 KeV or more without rotating the wafer obliquely.

[0034]

As described above, according to the semiconductor device and the method of manufacturing the same according to the present invention, hydrogen, a hydrogen compound, a halogen, or a halogen compound is introduced into the main surface of the semiconductor wafer by an ion implantation device, and then the semiconductor is manufactured. By designing an oxide film on the main surface of the wafer to introduce hydrogen, a hydrogen compound, a halogen, or a halogen compound into the gate oxide film 4, the introduction product is designed near the semiconductor substrate / oxide film interface. Can be distributed on the street.

After the gate oxide film 4 is formed, hydrogen, a hydrogen compound, halogen, or a halogen compound is introduced into the gate oxide film 4 by ion implantation or by a furnace in a non-oxidizing atmosphere. The introduction of hydrogen or the like at the time of forming 4 does not affect the ion implantation, and at the same time, the trap centers in the gate oxide film 4 can be reduced.

Further, in the implantation at an incident angle of about 7 °, the ion implantation machine has a lower limit of the implantation energy of about 5 KeV, so that a shallower distribution than that at the time of 5 KeV implantation cannot be obtained in the gate oxide film 4. Incident angle 30 °
The incident angle is 7 °, 5 KeV by injecting while rotating the wafer at about 60 ° or by depositing a film such as the polysilicon electrode 5 on the gate oxide film 4 and injecting through this film. It is possible to obtain a distribution shallower than the distribution at the time of implantation, and it is possible to distribute the above-described introduced substances in the gate oxide film 4 having a film thickness of about 10 nm as designed.

By introducing hydrogen, a hydrogen compound, a halogen, and a halogen compound into the gate oxide film 4 by the above-described method, a structural defect is caused on the oxide film side of the silicon substrate / oxide film interface. There are a large number of unsaturated silicon atoms (Chemical Formula 1), but due to the large number of hydrogen ions existing at the interface, they form SiH, and this structural defect does not serve as a trap center for carriers, so the gate threshold It is possible to suppress variation in the value voltage. Further, in the vicinity of the silicon substrate / oxidation interface, when the distorted Si-O bond is broken, (.O-Si) is also generated at the same time as the unsaturated silicon atom, and when electrons are injected into the oxide film, neutrality occurs. Although the structural defect (.O-Si) of 2 acts as the electron trap center,
Since a large number of hydrogen ions are present, (H—O—Si) is formed, carrier capture is suppressed, and fluctuations in the threshold voltage of the gate are reduced.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing a manufacturing process of a semiconductor device according to an embodiment of the present invention.

FIG. 2 is a cross-sectional view showing a manufacturing process of a semiconductor device according to a second embodiment of the present invention.

FIG. 3 is a sectional view showing a manufacturing process of a semiconductor device according to a third embodiment of the present invention.

FIG. 4 is a sectional view showing a manufacturing process of a semiconductor device according to a fourth embodiment of the present invention.

FIG. 5 is a cross-sectional view showing a manufacturing process of a conventional semiconductor device.

FIG. 6 is a cross-sectional view for explaining an interface level, an interface fixed charge, a trap center, and mobile ions in an oxide film.

FIG. 7 is a diagram for explaining influences of an interface state, an interface fixed charge, a trap center, and movable ions on electric characteristics of a semiconductor device.

[Explanation of symbols]

1 semiconductor substrate 2 LOCOS oxide film 3 channel ion implantation 4 gate oxide film 5 polysilicon gate electrode 6 N- drain ion implantation 7 N- source / drain region 8 sidewall film 9 N + drain ion implantation 10'N + source / drain Region 10 Sodium ion 11 Potassium ion 12 Capture center 13 Fixed charge 14 Interface level 16 Mobile ion Qt Capture center Qo Fixed charge Qi Interface level 17 Basic characteristics of MOSFET 18 Electrical characteristics with fixed charge Qo and capture center Qt 19 Electrical characteristics with interface state Qi 20 Gate threshold voltage 21 Hydrogen, hydrogen compound, halogen, or halogen compound

Claims (8)

[Claims] 1. A method comprising the steps of introducing hydrogen, a hydrogen compound, halogen or a halogen compound into the main surface of the semiconductor wafer by an ion implantation apparatus, and then forming an oxide film on the main surface of the semiconductor wafer. A method for manufacturing a characteristic semiconductor device. 2. A step of forming an oxide film on the main surface of a semiconductor wafer, and thereafter, hydrogen, a hydrogen compound, and
And a step of introducing a halogen or a halogen compound, the method for manufacturing a semiconductor device. 3. A method for manufacturing a semiconductor device, wherein the introduction of hydrogen, a hydrogen compound, halogen or a halogen compound by the ion implantation apparatus according to claim 2 is performed by an ion implantation apparatus. 4. A method of manufacturing a semiconductor device, wherein the ion implantation apparatus according to claim 1 or 3 introduces hydrogen, a hydrogen compound, a halogen or a halogen compound at an ion acceleration energy of 10 KeV or less. 5. The ion implantation apparatus according to claim 1 or 3, wherein the ion beam is incident on the substrate at an incident angle of about 30.
A method of manufacturing a semiconductor device, characterized in that the wafer is introduced while being rotated at an angle of 60 ° to 60 °. 6. The introduction of hydrogen, a hydrogen compound, a halogen or a halogen compound by the ion implantation apparatus according to claim 3, depositing a film on an oxide film, and introducing the film into the oxide film through the laminated film. A method of manufacturing a semiconductor device, comprising: 7. The manufacturing of a semiconductor device according to claim 2, wherein the introduction of hydrogen, a hydrogen compound, a halogen or a halogen compound is performed in a furnace in a non-oxidizing atmosphere after forming the oxide film. Method. 8. A semiconductor device manufactured by the method for manufacturing a semiconductor device according to claim 1 and having the oxide film as a gate oxide film.