JPH10173171A - Semiconductor device and manufacturing method therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent boron in a gate electrode from punching through to the gate insulating film side, without deteriorating the performance of a semiconductor device. SOLUTION: A gate insulating film 10 is formed of a silicon oxide film 3 and a silicon oxinitride film 4. Diffusion and punch through of boron atoms from a gate electrode 5 can be prevented. Thereby, change of the threshold voltage of a P-type MOS transistor can be prevented, and the reliability of the gate insulating film 10 can be ensured. In the gate insulating film 10, the silicon oxinitride film 4 is formed on the upper side of the silicon oxide film 3, so that deterioration of the performance of an element such as depletion of polysilicon and decrease of transconductance can be prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method of manufacturing a semiconductor device monolithically formed on a silicon substrate and a semiconductor device, and more particularly to a method of manufacturing a semiconductor device in which a gate electrode is formed on a silicon substrate via an insulating film and a semiconductor device. Related to the device.

[0002]

2. Description of the Related Art A semiconductor device formed monolithically on a silicon substrate is required to have higher performance, and accordingly, lower operation voltage and lower power consumption are required. Therefore, in a P-type MOS transistor, P ⁺
A surface channel type having a gate electrode structure is becoming mainstream. The P ⁺ type gate electrode is generally formed by introducing boron into polysilicon.

[0003] While such low power consumption is required, high integration of semiconductor devices is also required. For this reason, miniaturization of each element constituting a semiconductor element is required, and therefore, in a MOS transistor, a gate insulating film is reduced in thickness. For example, if the gate length is 0.1
In the case of an 8 μm MOS transistor, it is expected that the thickness of the gate insulating film will be reduced to 4.5 to 5.0 nm in the future.

Therefore, a future P-type MOS transistor is required to have a P.sup. ⁺ -Type gate electrode structure in which boron is introduced, to be thinner, and to be able to maintain higher reliability. .

However, the P ⁺ type gate electrode structure has a problem that a penetration phenomenon of boron atoms occurs. This penetration phenomenon of boron atoms means that the boron in the P ⁺ -type gate electrode that has been subjected to the heat treatment diffuses along the crystal grain boundaries of polysilicon and enters the gate insulating film. The boron that has invaded the gate insulating film further diffuses and reaches the silicon substrate, where a shallow P layer is formed. As a result, it has been reported that the threshold voltage of the P-type MOS transistor fluctuates and the reliability of the gate insulating film also decreases (for example, K. Uwasawa et al., IEDM Tec).
h. Digest, p. 895 (1993)).

Until now, various reports have been made on methods for suppressing the penetration of boron atoms. Each of these uses the effect of preventing the diffusion of boron atoms by nitrogen atoms, and is roughly classified into a method of introducing nitrogen into a gate electrode and a method of introducing nitrogen into a gate insulating film.

FIG. 4 shows a P-type M formed by a conventional method.
FIG. 4 is a partial cross-sectional view of a gate electrode portion of an OS transistor. Hereinafter, specific examples of each method will be described based on the cross-sectional view.

First, the method of introducing nitrogen into the gate electrode 42 is as follows: (1) A method of ion-implanting nitrogen into the gate electrode 42 made of polysilicon (T. Kuroi et al., Jpn. J. App.
l.Phys., Vol., p. 771 (1995)). (2) CVD (Chemical Vapor Depos) of the gate electrode 42
so-called in-situ N-do
ped CVD method (literature example Satoshi Nakayama IEICE Technical Report SDM94
-42 p.55 (1994)).

[0009] There is. In these methods, as shown in FIG. 4, nitrogen is introduced into a boundary 42a between the gate electrode 42 and the silicon oxide film (gate insulating film) 41. In these methods, nitrogen segregates at the crystal grain boundary of the polysilicon forming the gate electrode 42, and the segregated nitrogen prevents boron introduced into the polysilicon from diffusing along the crystal grain boundary. It is thought to be slow.

On the other hand, the method of introducing nitrogen into the gate insulating film is as follows: (3) A method of forming a silicon oxynitride film by performing a nitriding treatment on the silicon oxide film 41 (reference example: E. Hasegawa et al.,
IEDM Tech.Digest, p.327 (1995), HSMomose et al.,
IEEE Trans. Electron Devices, Vol. 41, No. 4 (1994)). (4) A method of forming a gate insulating film 41 by thermally oxidizing a silicon substrate 40 into which nitrogen has been ion-implanted in advance (reference example)
CTLui et al., Digest of the International Symposi
um on VLSI Technology, p. 18, 1996). (5) A method in which a silicon oxynitride film is deposited on the silicon substrate 40 by the CVD method and then slightly thermally oxidized (reference example L. Ma
nchanda et al., IEDM Tech. Digest, p.459 (1993)).

[0011] There is. In these methods (3), (4) and (5), it is considered that the diffusion of boron is slowed down by the region where the nitrogen concentration in the silicon oxide film 41 is high.

[0012]

However, in the method (1), when nitrogen is excessively introduced, the polysilicon forming the gate electrode 42 is depleted when a negative gate voltage is applied. There is. Further, in the method (2), when nitrogen is introduced excessively, there is a problem that the resistivity of polysilicon increases and the storage capacity of the silicon oxide film 41 decreases.

On the other hand, the method (3) has a problem that the transconductance of the P-type MOS transistor is reduced due to the nitride layer formed near the boundary surface 40a between the silicon oxide film 41 and the silicon substrate 40.

In the method (4), while there is a report that a nitride layer cannot be formed near the boundary surface 40a, 41a between the silicon oxide film 41 and the silicon substrate 40, there is also a report that a nitride layer can be formed (A. Furukawa et al.). ., Digest of the inte
rnational Symposium on VLSI Tech. p.62, 1996). When a nitride layer is formed, it can be easily estimated that the transconductance deteriorates as in the case (3).

Further, in the method (5), most of the silicon oxide film 41 into which nitrogen is introduced is formed by the CVD method, and only a small amount of the thermally oxidized film is reported (1/1 of the total in the literature reports). 5), it is easily assumed that the dielectric breakdown resistance will be weak.

The present invention has been made in view of the above points, and a method of manufacturing a semiconductor device and a semiconductor device capable of preventing performance degradation of an element while obtaining an effect of preventing diffusion of boron atoms by nitrogen atoms. The purpose is to provide.

[0017]

According to the present invention, there is provided a method of manufacturing a semiconductor device in which a gate electrode is formed on a silicon substrate with an insulating film interposed therebetween by thermally oxidizing the silicon substrate. Forming a silicon oxide film on the silicon oxide film, forming a silicon oxynitride film into which nitrogen is introduced, on the silicon oxide film, and depositing silicon on the silicon oxynitride film. And a step of forming a gate electrode by introducing boron.

As described above, a silicon oxynitride film into which nitrogen is introduced is formed on the upper surface portion of a silicon oxide film as a gate insulating layer, and boron is introduced into silicon deposited on the silicon oxynitride film to form a gate. By forming the electrode, nitrogen can be introduced while avoiding distribution of the gate electrode on the gate insulating layer side, the upper surface of the silicon substrate, and the silicon oxide film on the silicon substrate. Thus, the performance of the device is prevented from deteriorating while the effect of preventing the diffusion of boron atoms by nitrogen atoms is obtained.

[0019]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to the drawings. FIG. 2 is a diagram showing steps S1 to S3 of the method for manufacturing a P-type MOS transistor according to the present embodiment. FIG. 3 is a view showing steps S4 and S5 of the method for manufacturing a P-type MOS transistor according to the present embodiment. In this manufacturing method, first, as shown in step S1 of FIG. 2, an element isolation oxide film 2 is formed on an N-type silicon substrate 1, and a silicon oxide film having a thickness of 4 nm is formed by a usual pyrogenic oxidation method. Form 3 Here, the conditions of the pyrogenic oxidation method can be, for example, as follows.

Oxidation temperature: 750 ° C. Gas ratio: H ₂ : O ₂ = 1: 2 Next, as shown in step S2, a silicon oxynitride film 4 having a thickness of 2 nm is formed by the CVD method. Where C
The condition of VD can be, for example, as follows.

Apparatus LPCVD (Low Pressure CVD) Substrate temperature 820 ° C. Pressure 26.7 Pa Gas ratio SiH ₂ Cl ₂ : N ₂ O: NH ₃ = 25: 7
2: 3 Average growth rate 1.4 nm / min The nitrogen concentration in the formed silicon oxynitride film 4 is:
It is about 30 atm%.

Next, heat treatment is performed. The heat treatment conditions are
For example, the following can be performed. Processing temperature 850 ° C. Processing time 20 minutes Atmosphere Nitrogen Further, by CVD method, 200 nm (not shown)
After the formation of the polysilicon film, the polysilicon film is patterned into the shape of the gate electrode using photolithography and anisotropic etching, and the gate electrode 5 is formed as shown in step S3.

Then, a silicon oxide film (not shown) of about 100 nm is deposited by CVD and etched back to form a sidewall oxide film 6 as shown in step S4 of FIG. Then, after boron ions are implanted under the conditions of 5 keV and 4 × 10 ¹⁵ cm ⁻² ,
By activating the implanted impurities by applying a rapid heat treatment at 100 ° C. for about 10 seconds, the gate electrode 5 is made to be a P ⁺ type, and at the same time, a P ⁺ type source is / Drain regions 7 and 8 are formed. Thus, a P-type MOS transistor is completed.

FIG. 1 is a partial cross-sectional view of a gate electrode portion of a P-type MOS transistor formed by the manufacturing method of the present embodiment. In this P-type MOS transistor, a silicon oxide film 3 and a silicon oxynitride film 4 form a gate insulating film 10. Thereby, diffusion and penetration of boron atoms from the gate electrode 5 can be prevented. Therefore, fluctuation of the threshold voltage of the P-type MOS transistor can be prevented, and the reliability of the gate insulating film 10 can be maintained.

In the gate insulating film 10, since the silicon oxynitride film 4 is formed on the upper side of the silicon oxide film 3, the depletion of polysilicon and the formation of a transformer are prevented as in the conventional structure shown in FIG. It is possible to prevent the performance of the element from deteriorating such as a decrease in the conductor.

Further, in this embodiment, the silicon oxynitride film 4
The thickness of the silicon oxide film 3 is 4 n for a thickness of 2 nm.
Since the silicon oxynitride film 4 side is formed thin as m, the deterioration of the breakdown voltage of the gate insulating film 10 can be suppressed.

In this embodiment, the heat treatment is performed after the silicon oxynitride film 4 is deposited. Therefore, the boundary surface 10a between the silicon oxide film 3 and the silicon oxynitride film 4 generated when the silicon oxynitride film 4 is deposited. Can be reduced.

In this embodiment, an example in which a pyrogenic oxidation method is used as a method for forming the silicon oxide film 3 has been described. However, a dry oxidation method, an ultra-dry oxidation method, a high-pressure oxidation method,
Any other oxidation method such as a reduced pressure oxidation method, an ozone oxidation method, a steam oxidation method using a water bubble, and a hydrochloric acid oxidation method may be used.

In the heat treatment of the gate insulating film 10, in this embodiment, nitrogen is used as an atmosphere. Alternatively, an inert gas to which argon, oxygen, or a halogen element is added can be selected.

Further, the CVD conditions of the silicon oxynitride film 4, the temperature of the heat treatment, the shape of the P-type MOS transistor, and the detailed manufacturing process are not limited to those exemplified in this embodiment.

[0031]

As described above, according to the present invention, a silicon oxynitride film into which nitrogen is introduced is formed on a silicon oxide film as a gate insulating layer, and the silicon deposited on the silicon oxynitride film is Since the gate electrode is formed by introducing boron, nitrogen is introduced while avoiding the distribution of the gate electrode to the gate insulating layer side portion, the upper surface side portion of the silicon substrate, and the silicon oxide film to the silicon substrate side portion. be able to. Accordingly, it is possible to prevent the performance of the device from deteriorating due to the depletion of the polysilicon and the decrease in the transconductor while obtaining the effect of preventing the diffusion of the boron atom by the nitrogen atom.

[Brief description of the drawings]

FIG. 1 shows a P-type MOS formed by a manufacturing method according to an embodiment of the present invention.
FIG. 3 is a partial cross-sectional view of a gate electrode portion of a transistor.

FIG. 2 is a view showing steps S1 to S3 of the method for manufacturing a P-type MOS transistor according to the embodiment.

FIG. 3 is a view showing steps S4 and S5 of the method for manufacturing a P-type MOS transistor according to the embodiment.

FIG. 4 is a partial cross-sectional view of a gate electrode portion of a P-type MOS transistor formed by a conventional method.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Silicon substrate, 2 ... Element isolation oxide film, 3
..Silicon oxide film, 4 ... Silicon oxynitride film, 5
..Gate electrode, 10 ... Gate insulating film.

Claims (4)

[Claims] 1. A method of manufacturing a semiconductor device in which a gate electrode is formed on a silicon substrate with an insulating film interposed therebetween, the method comprising: thermally oxidizing the silicon substrate to form a silicon oxide film on an upper surface; Forming a silicon oxynitride film into which nitrogen has been introduced, and depositing silicon on the silicon oxynitride film and introducing boron into the deposited silicon to form a gate electrode. A method for manufacturing a semiconductor device, comprising: 2. The method according to claim 1, wherein said silicon oxynitride film is formed thinner than said silicon oxide film. 3. The method according to claim 1, wherein a heat treatment is performed after the formation of the silicon oxynitride film. 4. A semiconductor device in which a gate electrode is formed on a silicon substrate via an insulating film, wherein nitrogen is introduced on the silicon oxide film formed on the upper surface of the silicon substrate and on the silicon oxide film. A silicon oxynitride film formed by: and a gate electrode formed by depositing silicon on the silicon oxynitride film and introducing boron into the deposited silicon.