KR20090035338A - Method for fabricating dual gate in semiconductor device - Google Patents

Abstract

A method for fabricating a dual gate in a semiconductor device is provided to improve reliability of the gate oxide by protecting a foreign material from being permeated into the gate conductive film. A gate insulating film is formed on a semiconductor substrate including a first region and a second region. A diffusion barrier which contains a nitrogen by supplying a nitrogen radical ion to the gate insulating layer is formed. A conductive film is formed on a diffusion barrier which is formed on the silicon layer. A conductive film is formed on the silicon(Si) film, and a mask film pattern exposing the first area(A) is formed. An impurity ion of p-type is injected into the conductive film of the first area(A) by performing the ion injection process which use a mask film pattern as the ion implantation barrier film.

Description

Method for fabricating dual gate in semiconductor device

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor device, and more particularly, to a method of forming a dual gate of a semiconductor device capable of preventing impurities from penetrating into the gate conductive film and improving the reliability of the device.

A semiconductor device, such as a dynamic random access memory (DRAM), has a cell region and a peripheral circuit region. In particular, the peripheral circuit region includes a complementary metal oxide semiconductor (CMOS). In general complementary morph transistors, a p-type morph transistor has a buried channel structure, in which the channel length decreases as the device density increases, thereby applying a high electric field. This degrades the leakage current characteristics. Therefore, in recent years, a dual gate structure has been adopted to implement a p-type MOS transistor of a surface channel structure.

In the process of manufacturing the dual gate, after forming a gate conductive layer, an n-type impurity is implanted into a region where an n-type MOS transistor is to be formed, and a p-type impurity is implanted into a region where a p-type MOS transistor is to be formed. do. Then, a thermal diffusion process is performed on the entire semiconductor substrate to sufficiently diffuse the impurities injected into the gate conductive film. Accordingly, in the dual gate formed on the semiconductor substrate, a p-type gate injecting p-type impurities is formed in a region where a p-type morph transistor is formed, and an n-type impurity is injected in a region in which an n-type morph transistor is formed. An n-type gate is formed.

However, in order to form such a dual gate, impurity is implanted on the gate conductive layer, and during the subsequent thermal process, the impurity moves toward the gate insulating film and penetrates into the gate insulating film, thereby flattening the semiconductor device. As the threshold voltage changes according to the displacement of the band), the reliability of the gate insulating layer may decrease. Degradation of the reliability of the gate insulating film may affect a subsequent process, so a method of preventing impurities from penetrating into the gate insulating film is required.

A method of forming a dual gate of a semiconductor device according to an embodiment of the present invention includes forming a gate insulating film on a semiconductor substrate; Supplying nitrogen radical ions generated by laser irradiation on the gate insulating film to form a diffusion barrier film containing nitrogen; Forming a gate conductive layer on the diffusion barrier layer; Forming a gate metal film and a hard mask film on the gate conductive film; And patterning the hard mask to gate insulating film to form a gate stack.

In the present invention, the gate insulating film is preferably formed by supplying oxygen (O) radical ions on the semiconductor substrate.

The gate insulating film may be formed at a temperature of 750 ° C to 900 ° C.

The forming of the diffusion barrier layer may include generation of radical ions including a furnace including a boat on which a semiconductor substrate on which the gate insulating layer is formed may be mounted, and a laser irradiation part and a supply line connected to the reactor. Loading in a boat of a radical generator comprising a portion; Irradiating a laser from the laser irradiator to form nitrogen radical ions (N ^* ) while supplying a nitrogen source gas into the reaction chamber from the source gas injector; And supplying the formed nitrogen radical ions (N ^* ) to the semiconductor substrate disposed in the reactor through the supply line to form a diffusion barrier.

The nitrogen source gas preferably includes nitrous oxide (N ₂ O) gas, ammonium (NH ₃ ) gas, and nitrogen (N ₂ ) gas.

The radical generator is preferably batch-typed.

The diffusion barrier is preferably formed at a reaction temperature of 700 ° C to 700 ° C and a reaction pressure of 700 mTorr or less.

The forming of the gate insulating layer and the forming of the diffusion barrier layer may be performed in-situ.

In an embodiment, a method of forming a dual gate of a semiconductor device may include forming a gate insulating film on a semiconductor substrate having a first region and a second region; Supplying nitrogen radical ions generated by laser irradiation on the gate insulating film to form a diffusion barrier film containing nitrogen; Forming a polysilicon film of a first conductivity type on the diffusion barrier of the first region, and forming a polysilicon film of a second conductivity type on the diffusion barrier of the second region; Forming a gate metal film and a hard mask film on the first and second conductive polysilicon films; And patterning the hard mask layer to the gate insulating layer to form a gate stack.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. As those skilled in the art would realize, the described embodiments may be modified in various different ways, all without departing from the spirit or scope of the present invention.

1 to 7 are diagrams for explaining a dual gate of a semiconductor device according to an embodiment of the present invention. 8 is a view schematically showing a reactor used in the present invention. 9 is a view showing for explaining the radical nitridation process of the present invention. 10 is a view showing that impurities have penetrated into the gate insulating film.

Referring to FIG. 1, a gate insulating layer 105 is formed on a semiconductor substrate 100 having a first region A and a second region B. FIG. Here, the first region A is a region where the p-type MOS transistor is to be disposed, and the second region B is a region where the n-type MOS transistor is to be disposed.

Specifically, an oxidation process is performed on the semiconductor substrate 100 to form the gate insulating layer 105. The gate insulating layer 105 may be formed using a wet oxidation method or a dry oxidation method at a temperature of 750 ° C to 900 ° C. The gate insulating layer 105 may be formed of a silicon oxide layer (SiO ₂ ) while the supplied oxide source reacts with the silicon (Si) component of the semiconductor substrate 100. In this case, the gate insulating layer 105 may be formed using an oxidizing radical source. It is preferable that the gate insulating film 105 is formed to have a thickness of 30 kPa to 60 kPa.

Referring to FIG. 2, a diffusion barrier 110 is formed on the gate insulating layer 105.

Specifically, the semiconductor substrate 100 on which the gate insulating layer 105 is formed is loaded into the furnace 200 of FIG. 8. A boat 205 for mounting a plurality of wafers (or semiconductor substrates) is disposed in the reactor 200, and a radical ion generator 210 for generating radical ions at a position separated from the reactor 200. ) Is arranged. The radical ion generator 210 may include a laser in the reaction chamber 215, a source gas injection unit 220 supplying a source gas into the reaction chamber 215, and a source gas supplied in the reaction chamber 215. It comprises a laser irradiation unit 225 for generating a radical ion by irradiating the. The reactor 200 and the radical ion generator 210 are connected to each other using the supply line 230, and the supply amount may be adjusted through a valve 235.

The semiconductor substrate 100 is loaded on the boat 205 disposed in the reactor 200. Next, a nitrogen (N) source gas is supplied into the reaction chamber 215 from the source gas injector 220 of the radical ion generator 210. Here, while supplying a nitrogen source gas, a laser is irradiated onto the reaction chamber 215 from the laser irradiation unit 225 to react with the nitrogen source gas supplied into the reaction chamber 215 to generate nitrogen radical ions (N ^* ). The nitrogen source gas may be supplied including nitrous oxide (N ₂ O) gas, ammonium (NH ₃ ) gas and nitrogen (N ₂ ) gas. When the laser is irradiated into the reaction chamber 215 supplied with the nitrogen source gas, nitrogen molecules excited in the reaction chamber 215 as the nitrogen source gas is decomposed, nitrogen radical ions (N ^* ), some ions, and There are electrons. Next, nitrogen radical ions N ^* present in the reaction chamber 215 are supplied to the semiconductor substrate 100 disposed in the reactor 200 through the supply line 230. At this time, the nitrogen radical ions (N ^* ) may adjust the supply amount through the valve 235 of the supply line 230.

As shown in FIG. 9, the nitrogen radical ions N ^* supplied to the semiconductor substrate 100 are formed on the semiconductor substrate 100, for example, silicon (Si) of the silicon oxide layer (SiO ₂ ). Reaction with a component to form a diffusion barrier 110 of the nitrogen (N) component on the gate insulating film 105. The nitrogenous diffusion barrier 110 may include a silicon oxynitride (SiON) film. The diffusion barrier 110 is preferably formed at a reaction temperature of 700 ° C to 700 ° C and a reaction pressure of 700 mTorr or less. In this case, it is preferable that the diffusion barrier 110 proceed in-situ in the reactor 200 in which the gate insulating layer 105 is formed.

As such, when the diffusion barrier layer 115 of the nitrogen (N) component is formed on the gate insulating layer 105 by using a nitriding process for supplying nitrogen radical ions, a gate conductive layer doped with impurities is formed and then impurities are activated. Even if the heat treatment is performed, the impurities can be prevented from penetrating into the gate insulating film 105 to improve the characteristics of the semiconductor device. That is, if the impurity is suppressed from penetrating the gate insulating film 105, it is possible to prevent the threshold voltage from being changed while the flat band is displaced.

On the other hand, a method of nitriding the upper portion of the gate insulating film using plasma is proposed as a method of forming the diffusion barrier film of the nitrogen component. The nitriding process using plasma is a method of forming nitrogen radical ions using a plasma at a temperature of 350 ° C to 400 ° C while supplying a nitride source gas. However, in the method of forming nitrogen radical ions using plasma, the degree of deterioration of the gate insulating film due to damage caused by plasma after nitriding treatment is serious depending on the process conditions. In particular, in a process requiring a high nitrogen concentration, when the gate insulating film is exposed to plasma for a long time or exposed to a high energy plasma, the leakage current increases by more than 1000 times, and the reliability is severely degraded so that it cannot be applied to the device. do. In addition, as shown in FIG. 10, a problem such as damage (A) of silicon (Si) of the semiconductor substrate 300 may occur due to an attack caused by plasma exposure. In addition, since the gate insulating layer is formed, a single-type plasma equipment may be used, thereby increasing process steps. In the drawings, the portions not described are the gate insulating layer 305 and the gate conductive layer 310.

However, in the embodiment of the present invention, by forming nitrogen radical ions using a laser in the process of forming the diffusion barrier 110, a gate insulating film having excellent quality is formed without attacking the semiconductor substrate 100 by plasma exposure. It is possible to improve the reliability of the device. In addition, the process step may be reduced by in-situ in the reactor 200 in which the gate insulating layer 105 is formed. In addition, the yield can be improved by using a batch-type reactor that can operate a plurality of semiconductor substrates together.

Referring to FIG. 3, a conductive film 115 is formed on the diffusion barrier 110. The conductive film 115 formed on the diffusion barrier film 110 may be formed of a silicon (Si) film. This silicon film may be formed of a doped polysilicon in which impurities are implanted, or may be formed of an undoped amorphous silicon. When impurities are injected onto the conductive layer 115, phosphorus (P) may be doped or boron (B) may be doped.

Referring to FIG. 4, a mask layer pattern 120 exposing the first region A is formed. The mask layer pattern 120 may be formed as a photoresist layer. Next, as indicated by the arrows in the figure, an ion implantation process using the mask film pattern 120 as the ion implantation barrier film is performed to form p-type impurity ions, such as boron, in the conductive film 115 of the first region A. (B) Ion or boron fluoride (BF ₂ ) ions are implanted. By this ion implantation process, the conductive film 125a in which the p-type impurity ion is implanted is formed in the first region A, and the conductive film 125b in which the n-type impurity ion is implanted in the second region B is formed. Is formed. After the ion implantation process is performed, the mask layer pattern 120 is removed.

Referring to FIG. 5, heat treatment is performed on the semiconductor substrate 100 to activate impurity ions implanted in the conductive films 125a and 125b. By the heat treatment, the p-type gate conductive film 130 is formed in the first region A, and the n-type gate conductive film 135 is formed in the second region B. FIG.

Referring to FIG. 6, a gate metal layer 140 is formed on the p-type gate conductive layer 130 and the n-type gate conductive layer 135. The gate metal layer 140 may be formed of a metal silicide layer or a metal layer, or may have a double layer structure of a metal silicide layer and a metal layer. In this case, the metal silicide film may be formed of a tungsten silicide (WSix) film, and the metal film may be formed of a tungsten (W) film. Next, a hard mask film 145 is formed on the gate metal film 140. The hard mask layer 145 supplies a nitride source such as nitrous oxide (N ₂ O) gas, ammonium (NH ₃ ) gas, and nitrogen (N ₂ ) gas on the semiconductor substrate on which the gate metal layer 140 is formed. It can be formed by applying an appropriate power.

Referring to FIG. 7, the n-type gate 150 and the p-type gate 155 are formed on the semiconductor substrate 100 by patterning the hard mask layer 145 to the gate insulating layer 105.

In the method of forming a dual gate of a semiconductor device according to the present invention, as the diffusion barrier layer is formed on the gate insulating layer by a nitriding process using nitrogen radical ions, the impurity of the gate conductive layer penetrates the gate insulating layer. Can be prevented. In the process of forming the diffusion barrier layer, nitrogen radical ions may be formed using a laser to prevent the semiconductor substrate from being damaged by plasma exposure. In addition, the process step can be reduced by going in-situ in one reactor in which the gate insulating film is formed.

1 to 7 are diagrams for explaining a dual gate of a semiconductor device according to an embodiment of the present invention.

8 is a view schematically showing a reactor used in the present invention.

9 is a view showing for explaining the radical nitridation process of the present invention.

10 is a view showing that impurities have penetrated into the gate insulating film.

Claims (9)

Forming a gate insulating film on the semiconductor substrate; Supplying nitrogen radical ions generated by laser irradiation on the gate insulating film to form a diffusion barrier film containing nitrogen; Forming a gate conductive layer on the diffusion barrier layer; Forming a gate metal film and a hard mask film on the gate conductive film; And And forming a gate stack by patterning the hard mask layer to the gate insulating layer. The method of claim 1, The gate insulating film is formed by supplying oxygen (O) radical ions on the semiconductor substrate. The method of claim 1, The gate insulating film is formed at a temperature of 750 ℃ to 900 ℃ dual gate forming method of a semiconductor device. The method of claim 1, wherein the forming of the diffusion barrier layer, In the boat of the radical generating device including a furnace including a boat on which the wafer insulating film is formed and a boat on which a wafer can be mounted, and a radical ion generating unit including a laser irradiation unit and a supply line connected to the reactor. Loading; Irradiating a laser from the laser irradiator to form nitrogen radical ions (N ^* ) while supplying a nitrogen source gas into the reaction chamber from the source gas injector; And And supplying the formed nitrogen radical ions (N ^* ) to the semiconductor substrate disposed in the reactor through the supply line to form a diffusion barrier layer. The method of claim 1, The nitrogen source gas comprises a nitrous oxide (N ₂ O) gas, ammonium (NH ₃ ) gas and nitrogen (N ₂ ) gas, characterized in that the dual gate formation method of the semiconductor device. The method of claim 4, wherein And the radical generating device is batch-typed. The method of claim 1, The diffusion barrier layer is formed at a reaction temperature of 700 ℃ to 700 ℃ and a reaction pressure of 700mTorr or less. The method of claim 1, The forming of the gate insulating film and the forming of the diffusion barrier layer are performed in-situ (in-situ), the method of forming a dual gate of a semiconductor device. Forming a gate insulating film on the semiconductor substrate having the first region and the second region; Supplying nitrogen radical ions generated by laser irradiation on the gate insulating film to form a diffusion barrier film containing nitrogen; Forming a polysilicon film of a first conductivity type on the diffusion barrier of the first region, and forming a polysilicon film of a second conductivity type on the diffusion barrier of the second region; And Forming a gate metal film and a hard mask film on the first and second conductive polysilicon films; And And forming a gate stack by patterning the hard mask layer and the gate insulating layer.

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