KR100356805B1 - Method of manufacturing smeicofnuctor device - Google Patents

Abstract

The present invention discloses a method of manufacturing a semiconductor device for reducing contact resistance between a gate line and a bit line having a tungsten polyside (W-polycide) structure. According to the disclosed method, the gate line and the bit line are formed in a tungsten polyside structure including a laminated film of a doped poly-Si layer and a tungsten silicide layer (WSix), wherein the gate line is the bit line. In order to reduce contact resistance and improve gate characteristics, silicon nitride film SiNx is deposited in-situ on the tungsten silicide film WSix after deposition of tungsten silicide film WSix. It is done.

Description

Manufacturing method of semiconductor device {METHOD OF MANUFACTURING SMEICOFNUCTOR DEVICE}

The present invention relates to a method for manufacturing a semiconductor device, and more particularly, to a method for manufacturing a semiconductor device for reducing contact resistance between a gate line and a bit line having a tungsten polyside structure.

As is well known, polysilicon has been used as the material of the gate line and the bit line. However, since the polysilicon gate lines and bit lines have limitations in implementing low resistance values at the fine line widths required in high-density and high-speed devices, their use has been proposed, and recently, tungsten polysides ( W-polycide) is used as a material for gate lines and bit lines in place of the polysilicon for improving signal processing speed.

The tungsten polyside is a structure in which a doped poly-Si layer and a tungsten silicide (WSix) layer are stacked, and thus, a low resistance at a fine line width can be realized compared to a single layer of polysilicon.

On the other hand, the gate line and the bit line are electrically separated from each other in the cell region, but are contacted with each other in the peripheral circuit region for signal transmission to the capacitor.

1 is a cross-sectional view illustrating a gate line and a bit line having a tungsten polyside structure in contact with each other in a peripheral circuit area according to the related art.

As shown in the drawing, the gate line 2 of the tungsten polyside structure formed of a laminated structure of the doped polysilicon film 2a and the tungsten silicide film 2b on the semiconductor substrate 1 is formed to extend in one direction. The interlayer insulating film 3 is deposited on the entire semiconductor substrate 1 so as to cover the gate line 2, and the doped polysilicon film 12a and the tungsten silicide film 12b are stacked. The bit line 12 of the tungsten polyside structure having a structure is disposed to extend in a direction orthogonal to the gate line 2 on the interlayer insulating film 3, It is formed to contact the gate line 2 through 4).

However, when the gate line and the bit line having the tungsten polyside structure are contacted, the contact resistance therebetween increases due to the following reasons.

First, when the gate line and the bit line of the tungsten polyside structure are contacted, the tungsten silicide layer of the gate line and the doped polysilicon layer of the bit line come into contact with each other. As shown in FIG. 2, tungsten silicide Due to the difference between the work function (Φ _WSix ) of the film and the work function (Φ _poly-Si ) of the polysilicon film, a barrier height is generated between them, which represents a rather large value of about 0.65 eV. Accordingly, the tunneling current during the electron movement in the tungsten silicide (WSix) film is reduced, so that the contact resistance between the gate line and the bit line is increased.

In FIG. 2, Ec denotes a conduction band energy, Ev denotes a balance band energy, Ef denotes a Fermi energy, and Evac denotes a vaccum energy level.

Second, when forming a bit line contact for contact with the gate line by using a plasma etching process, tungsten silicide (WSix) of the gate line is inevitably exposed to the plasma, at this time, tungsten (W) and silicon (Si) Due to the difference in the sputter yield between the surface of the tungsten silicide (WSix) becomes rough, and due to the difference in reactivity with the plasma etching gas, the amorphous tungsten silicide (WSix) film on the surface of the amorphous tungsten oxide film (WO) ₃ ) and a compound such as tungsten carbide (WC) is formed, thereby increasing the contact resistance between the gate line and the bit line.

In particular, when an insulating film such as the tungsten oxide film WO ₃ and tungsten carbide WC is formed at the contact interface between the gate line and the bit line, the insulating film acts as a barrier during electron channeling, and thus tunneling is performed. The current is drastically reduced, while the contact resistance is increased.

The reason why the insulating layer is formed is because, as shown in Table 1 below, the ΔH (reaction heat generation) value exhibits a large negative value and the production reaction proceeds actively.

Table 1

Compound △ H (KJ / mole) Creation order WC, SiC +--20.5 ↓ First direction in the direction of the arrow SiO ₂ + ∼-17 WNx 12.6 W ₂ N -72 WO ₂ -533 WO ₃ -843

In conclusion, when the gate line and the bit line of the tungsten polyside structure are contacted according to the conventional method, a signal delay phenomenon occurs due to an increase in the contact resistance therebetween, so that high-speed operation cannot be achieved.

On the other hand, when forming a gate line with a tungsten polyside structure, it is common to form an anti-reflection film made of silicon nitride film on the tungsten silicide (WSix) film, for example, if the anti-reflection film is not formed, the tungsten silicide Due to the high reflectance optical properties of the (WSix) film, the width of the resist pattern cannot be secured stably in the photo process, and the result of the unstable photo process also affects the subsequent etching process, making the line width control of the gate line unstable. As a result, there is a problem that deterioration of gate characteristics such as gate oxide integrity (GOI) characteristics and threshold voltage characteristics is caused.

Accordingly, an object of the present invention is to provide a method of manufacturing a semiconductor device capable of preventing a decrease in gate characteristics while preventing an increase in contact resistance between a gate line and a bit line. have.

1 is a cross-sectional view illustrating a state in which a gate line and a bit line having a tungsten polyside structure are contacted according to the related art.

2 is a view for explaining a work function at a contact interface between a tungsten silicide film and a polysilicon film.

3 is a cross-sectional view showing a state in which a gate line and a bit line having a tungsten polyside structure are contacted according to the present invention.

4 is a diagram for explaining a work function at a contact interface between a silicon nitride film and polysilicon.

Explanation of symbols on the main parts of the drawings

21 semiconductor substrate 22,42 doped polysilicon film

23,43 tungsten silicide film 24 silicon nitride film

30 gate 31 interlayer insulating film

32: contact hole 50: bit line

The semiconductor device manufacturing method of the present invention for achieving the above object, a tungsten polyside consisting of a laminated film of a doped poly-Si (doped poly-Si) and a tungsten silicide film (WSix) doped the gate line and the bit line In the method of manufacturing a semiconductor device having a (W-polycide) structure, the gate line after the deposition of a tungsten silicide layer (WSix), in order to reduce the contact resistance and the gate characteristics with the bit line, the tungsten silicide layer Silicon nitride film (SiNx) is deposited in-situ on (WSix).

According to the present invention, by forming a silicon nitride (SiNx) film on the tungsten silicide (WSix) film of the gate line, it is possible to reduce the contact resistance between the gate line and the bit line, and to prevent the deterioration of the gate characteristics.

(Example)

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

3 is a cross-sectional view illustrating a state in which a gate line and a bit line formed in accordance with an embodiment of the present invention are in contact. As shown, the gate line 30 and the bit line 50 have a tungsten polyside structure composed of a stacked structure of doped polysilicon films 22 and 42 and tungsten silicide films 23 and 43, and an interlayer insulating film. The contact holes 32 provided at 31 are contacted with each other via bit line contacts. In particular, the gate line 30 has a structure in which a silicon nitride (SiNx) film 24 is further formed on the tungsten silicide layer 23.

Here, the doped polysilicon films 22 and 42 of the gate line 30 and the bit line 50 are deposited by CVD using SiH ₄ as a reaction gas at 500 to 700 ° C, and as a dopant, PH ₃ Using a gas, the mixing ratio of SiH ₄ and PH ₃ is adjusted to about 1.1: 1.5 to 1.5: 1.8.

Further, the tungsten silicide film 23 for the gate line 30 is deposited by reacting SiH ₂ Cl ₂ and WF ₆ at 550 to 600 ° C., and at this time, a mixture ratio of SiH ₂ Cl ₂ and WF ₆ is respectively deposited. 8 to 10: 1.5 to 2 to 9 to 11: 0.8 to 1.2, so that a tungsten silicide [WSix (x = 2.3 to 2.5)] film having a composition ratio of silicon of about 2.3 to 2.5 is formed. SiN ₄ and N _{2 in} the mixed ratio of 3 to 6: 7 to 10 to 2 to 5: 7 to 9 with a silicon nitride film (SiNx) on top of the Si ⁺ / N ⁺ PECVD process by RF discharge. 24) to be deposited.

That is, according to the present invention, after the deposition of the tungsten silicide layer 23, the mixed gas of SiH ₄ and N ₂ introduced as a reaction gas into the chamber during the deposition of the tungsten silicide layer 23 is ionized by RF discharge. Thereafter, the silicon nitride film 24 is continuously deposited at room temperature by an in-situ PE-CVD method.

In this case, the tungsten silicide film 23 and the silicon nitride film 24 adjust the mixing ratio and deposition time of SiH ₂ Cl ₂ , WF ₆ , N _2, and SiH ₄ , and the tungsten silicide film 23 is 500 to 1,000 Å. Thickness, and the silicon nitride film 24 is deposited to a thickness of 100 to 200 mm 3. In addition, the form of the plasma for depositing the silicon nitride film 24 uses a high-efficiency RF Si ⁺ / N ⁺ plasma having a 13.56 MHz waveform with high ionization efficiency and reactivity efficiency.

Meanwhile, in order to promote the reactivity between Si ⁺ / N ⁺ and the tungsten silicide film 23, the surface of the tungsten silicide film 23 using argon (Ar) plasma in an in-situ manner before the PE-CVD process. In this case, in order to ensure the stability of the plasma during the argon plasma, the process pressure and the flow rate are preferably set to about 3 to 8 mTorr and 10 to 30 sccm, respectively. In addition, after the silicon nitride film 24 is formed, the silicon nitride film 24 may be crystallized through a subsequent thermal process at 600 to 900 ° C.

In the bit line, the doped polysilicon film 42 is formed to have a thickness of 500 to 700 GPa, the tungsten silicide film 43 is formed to have a thickness of 900 to 1,300 GPa, and the tungsten silicide film 43 is 350 to MS (monosilane, SiH ₄ ) and WF ₆ are used as the reaction gas at 400 ° C., and the mixing ratio of MS and WF ₆ is adjusted to about 90-100: 1 to 4 degrees.

As described above, when the silicon nitride film is deposited on the tungsten silicide film for the gate line, the silicon nitride film has an optical characteristic similar to that of the silicon nitride oxide (SiON) generally used as an antireflection film. In spite of the omission, the gate line width can be stably realized at the time of gate patterning. Therefore, the GOI characteristic, the threshold voltage characteristic and the gate characteristic can be improved, so that the signal processing speed of the device can be increased.

In addition, when the silicon nitride film is deposited on the tungsten silicide film, a contact between the gate line and the bit line is made between the silicon nitride film and the doped polysilicon film, and as shown in FIG. 4, the silicon nitride film The work function Φ _SiNx is not only lower than the work function of the tungsten silicide film Φ _WSix , but also similar to the work function Φ _poly-Si of the polysilicon film, so that the potential barrier between the silicon nitride film and the polysilicon film is The height is not large, so that the tunneling current increases when the electrons move in the tungsten silicide film WSix, while the contact resistance decreases.

In addition, when a silicon nitride film is deposited on the tungsten silicide film of the gate line, since the silicon nitride film is exposed during bit line contact formation, the formation of insulating compounds such as WO ₃ and WC on the surface of the tungsten silicide film is suppressed, so Increasing contact drop caused by the insulating compound is prevented. In particular, since the silicon nitride film has a small difference in lattice constant from the tungsten silicide film and a small difference in stress generated during deposition, the lifting phenomenon of the film is also suppressed due to the stress relaxation effect. It is very easy to apply in the actual element production process.

As described above, the present invention forms a gate line and a bit line in a tungsten polyside structure composed of a laminated film of a doped polysilicon film and a tungsten silicide film, but in the case of the gate line, a silicon nitride film is formed on the tungsten silicide film. In this way, the contact resistance between the gate line and the bit line can be lowered by the silicon nitride film, so that the fabrication of a device which is very advantageous for high speed operation can be made, and the operating voltage required for driving the device can be reduced, thereby reducing the power consumption. The device of can be manufactured.

In addition, by using the silicon nitride film as an anti-reflection film, it is possible to stably control the line width of the gate, and to reduce the residual stress in the tungsten silicide film through the formation of the silicon nitride film, By reducing the diffusion of fluorine (F) introduced in the deposition process, gate characteristics such as GOI characteristics and threshold voltage characteristics can be improved.

In addition, since the adhesion strength between the gate line and the bit line can be increased through the formation of the silicon nitride film, defects in the bit line can be prevented, so that the production yield can be improved.

In addition, this invention can be implemented in various changes within the range which does not deviate from the summary.

Claims (8)

In the semiconductor device manufacturing method of forming a tungsten polyside (W-polycide) structure consisting of a laminated film of a doped poly-Si (doped poly-Si) and a tungsten silicide (WSix) structure, the gate line and the bit line The gate line may be formed in-situ on the tungsten silicide layer WSix after deposition of the tungsten silicide layer WSix to reduce contact resistance with the bit line and improve gate characteristics. SiNx) method for manufacturing a semiconductor device, characterized in that for depositing. The method of claim 1, wherein the silicon nitride film A method of manufacturing a semiconductor device, characterized in that the deposition of the tungsten silicide film and the in-situ PECVD process. The method of claim 2, wherein the silicon nitride film is deposited at room temperature by adjusting the mixing ratio of SiH ₄ and N ₂ to 3 to 6: 7 to 10 to 2 to 5: 7 to 9 as a reaction gas. Method of manufacturing a semiconductor device. The method of manufacturing a semiconductor device according to claim 2, wherein the tungsten silicide film and the silicon nitride film are each deposited at a thickness of 500 to 1,000 GPa and 100 to 200 GPa. The method of claim 2, wherein the silicon nitride film is deposited using a high efficiency RF Si ⁺ / N ⁺ plasma having a 13.56 MHz waveform having high ionization efficiency and reactivity efficiency. The method of manufacturing a semiconductor device according to claim 2, wherein the surface of the tungsten silicide film is activated by argon (Ar) plasma before the deposition of the silicon nitride film. The method of claim 6, wherein the argon plasma, A process for producing a semiconductor device, characterized in that the process pressure and flow rate are performed under conditions of 3 to 8 mTorr and 10 to 30 sccm, respectively. The method of claim 2, wherein after deposition of the silicon nitride film, Method for manufacturing a semiconductor device, characterized in that for performing the crystallization, thermal processing at 600 ~ 900 ℃.