JP2006278920A - Manufacturing method for semiconductor device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve the following problem: a barrier film and a base formed beneath it can be damaged due to HF remaining in a chamber when a W thin film is formed. <P>SOLUTION: SiH<SB>4</SB>gas is introduced into the chamber to remove HF remaining in the chamber before a semiconductor substrate is conveyed into the chamber. Damage to a barrier layer or a base due to HF is thereby avoided. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a method for manufacturing a semiconductor device.

  Metal materials such as tungsten (W), titanium (Ti), cobalt (Co), aluminum (Al), and copper (Cu) are mainly used as metal wiring materials for semiconductor devices. These metals have been formed by a physical film forming method such as sputtering, but due to the recent miniaturization of wiring and the accompanying miniaturization of contact holes connecting the wirings and an increase in aspect ratio, CVD ( Chemical vapor deposition has been used for film formation.

  Among them, tungsten is often used for forming a thin film used for wiring and forming a plug by filling a contact hole.

  Japanese Patent Laid-Open No. 2002-266073 discloses a specific resistance of a tungsten film formed on a substrate when a tungsten thin film is formed due to a difference in hydrofluoric acid concentration in a processing chamber. In order to prevent the gas from changing, a gas containing HF or a substance that generates HF gas by reaction is introduced into the processing container, and the inside of the processing container is purged with the gas containing HF, It is disclosed that a substrate to be processed is disposed, and then a Si-containing gas is supplied into the processing container to perform pretreatment on the processing substrate, and then a film forming gas is supplied into the processing container to perform the film forming process. Yes.

  In order to improve the embedding property when filling the recess with tungsten, when using hydrogen gas that is less reducing than silane, in order to improve the adhesion with the underlying silicon surface, the Ti film, the TiN film or both The laminated film is formed as a barrier film to be a base film. When hydrogen gas with low reducibility is used, WF6 does not react completely, so the unreacted WF6 gas attacks the underlying Ti film, TiN film, or a laminated film of both, and the barrier layer reacts with fluorine. Thus, there may be a case where a volcano that expands in volume and protrudes upward is generated or a void is generated in the embedded hole.

  In order to remedy these problems, first, hydrogen is changed to silane, and a nucleation layer of a tungsten film is formed by a slight thickness. Alternatively, only silane is supplied alone, for example, an intermediate of silane (SiHx: x <4) is adsorbed on the wafer surface, and the above nucleation layer is formed using this as a base point. However, in order to improve the coverage of the barrier layer, an organic compound of Ti is often used as a raw material gas, and the carbon component contained in the organic compound of Ti is contained in the barrier layer. In some cases, the coverage of the adhesive layer itself deteriorated. In order to improve this, Japanese Patent Application Laid-Open No. 2002-193233 alternately repeats evacuation of the initial tungsten film while supplying an inert gas between the supply of the reducing gas and the supply of the tungsten gas. It is disclosed.

On the other hand, in JP-A-8-236464, after forming a tungsten thin film for the purpose of gradually reducing the sheet resistance of the tungsten silicon (WSix) thin film using a source gas composed of SiH4 and WF6, It is disclosed that the residual gas is purged by flowing SiH4 through the chamber.
JP 2002-266073 A JP 2002-193233 A JP-A-8-236464

  However, the tungsten CVD growth method often uses a halogenated tungsten gas (WF6) as a tungsten raw material and H2 and SiH4 gases as a reducing gas. In particular, when the recess is filled with tungsten, hydrogen is used as the reducing gas, and a large amount of HF gas, which is a reaction product gas, is generated during the growth of tungsten, as shown in Equation 1.

WF6 + 3H2 → W + 6HF (1)
As shown in FIG. 1, the recess is formed from a Ti film, a TiN film, or a laminated film of a Ti film and a TiN film in a contact hole provided in an interlayer insulating film 2 formed on a semiconductor substrate 1 made of silicon. A barrier film 3 is formed, a W film is embedded in contact with the barrier film 3, and the excess barrier film 3 and the W film on the interlayer insulating film 2 are removed by using, for example, a CMP (Chemical Mechanical Polish) method. Thus, a W plug is formed. Although the silicon layer is exposed at the bottom of the contact hole in FIG. 1, it goes without saying that the metal wiring layer or the silicide layer may be exposed.

  Needless to say, the interlayer insulating film may be a silicon oxide film, a silicon nitride film, a silicon oxynitride film, or a low relative dielectric constant film such as SiOC.

  Since the W film 4 uses a halogenated gas (WF 6) and hydrogen (H 2) as shown in Equation 1, a reaction product gas HF always exists in the processing chamber.

  The generated HF remains in the processing chamber. The HF gas sometimes attacked the W barrier film 3 and the silicon layer, metal layer, or silicide layer formed under the W barrier film 3 immediately before the W film formation, resulting in damage.

  If the barrier film and / or the silicon layer, the metal layer, or the silicide layer is damaged, the silicon layer may cause a leak, and the metal film may have a high resistance.

The present invention introduces WF6 gas and H2 gas into a chamber using the contact hole of a semiconductor device having an insulating film formed on a semiconductor substrate and at least a contact hole penetrating the insulating film as source gases. A method of manufacturing a semiconductor device embedded by forming a tungsten film on a semiconductor substrate,
An HF barge process for introducing SiH4 gas into the chamber before introducing the semiconductor substrate into the chamber and purging the HF in the chamber;
Then introduce an inert gas into the chamber,
And a step of introducing a semiconductor substrate into the chamber.

  The partial pressure of SiH4 gas in the HF purge step is preferably 0.1 to 3 torr, and the carrier gas of SiH4 gas in the HF purge step is preferably an inert gas and / or hydrogen gas.

  Furthermore, it is preferable that the temperature of the chamber in the HF purge process is 300 to 500 ° C.

  In the present invention, after the tungsten film is formed, SiH4 is introduced into the chamber, and after removing the semiconductor substrate on which the tungsten thin film is formed without removing HF in the chamber, before introducing the semiconductor substrate into the chamber, Since the HF in the chamber can be removed, the barrier film and / or the silicon layer, the metal layer, or the silicide layer may be damaged in order to prevent the leakage or resistance from increasing.

  In the present invention, when W is buried in a contact hole penetrating the interlayer insulating film formed in the interlayer insulating film by using the CVD method, the chamber before the semiconductor substrate having the contact hole formed is transferred to the chamber of the CVD apparatus. SiH 4 is introduced into the chamber, and HF remaining in the chamber is removed by the reaction of Formula 2.

SiH4 + 4HF → SiF4 + 4H2 (2)
Then, SiF4, 4H2 produced | generated by reaction is removed by attracting | sucking in a vacuum, introducing an inert gas.

  Thereafter, a semiconductor substrate with contact holes formed therein is introduced into the chamber, WF6 and H2 gases are supplied to the chamber, a tungsten film is formed, and tungsten is embedded in the contact holes.

  The tungsten film is formed by introducing argon gas and WF 6 gas, which are hydrogen and carrier gas. WF6 is introduced into the chamber at a smaller flow rate than that for forming the tungsten thin film to form nuclei on the semiconductor substrate, and then the flow rate of WF6 gas is increased to form a tungsten thin film on the surface of the semiconductor substrate.

  The conditions for forming the tungsten thin film are described in detail in the prior art.

  In the present invention, it is important to introduce SiH4 gas into the chamber and remove HF in the chamber, and the HF in the chamber reacts with SiH4 gas to be discharged out of the chamber as SiF4.

  FIG. 3 shows the HF concentration in the chamber measured by a quadrupole mass spectrometer.

  As shown in FIG. 3, when SiH4 is introduced (1) into the chamber, the HF concentration in the chamber decreases. When SiH4 is introduced into the chamber, the introduction of SiH4 is stopped in a state where the HF concentration in the chamber is lowered (2), an inert gas is introduced into the chamber, and SiF4 produced by the reaction between SiH4 and hydrofluoric acid and H2 is exhausted from the chamber. Thereafter, the semiconductor substrate is introduced into the chamber, and (3) WF6 gas and H2 as source gases are introduced into the chamber. WF6 gas and H2, which are source gases, react in the chamber, form a tungsten thin film on the semiconductor substrate, and fill the contact holes formed in the semiconductor substrate with tungsten (4 to 5).

  When WF6 gas and H2 as source gases are introduced into the chamber, HF is formed by the reaction of Formula 1, the HF concentration is increased, nuclei are formed, and then a tungsten film is formed. When the supply of the source gas is stopped after the tungsten film having the desired thickness is formed (5) and the inert gas is introduced, the HF concentration in the chamber decreases. Thereafter, the semiconductor substrate (sometimes referred to as a wafer) is unloaded from the chamber (6). Since HF generated during the formation of the tungsten film is partially adsorbed in the chamber, HF remains in the chamber.

  In the present invention, HF remaining in the chamber is removed by introducing SiH4 gas into the chamber and reacting with HF before introducing the next semiconductor substrate into the chamber. . Since the HF in the chamber is removed before the semiconductor substrate is carried into the chamber, the underlying or barrier film is not damaged by the HF due to the HF remaining in the chamber before the tungsten film is formed.

  Further, when SiH4 gas is introduced into the chamber after the tungsten film is formed, even if WF6 is contained in the chamber, tungsten surface tungsten silicide is formed, and WF6 does not remain in the chamber. Polysilicon may be formed.

  In the case of growing tungsten to fill the opening, if tungsten silicide or polysilicon is formed on the surface of the tungsten thin film, then unnecessary tungsten film formed on the surface is removed by CMP. In this case, tungsten silicide or polysilicon has a lower polishing rate than the tungsten film. In particular, tungsten silicide does not cause a problem such as extremely low polishing rate.

  After the HF purge, an inert gas such as argon gas or nitrogen gas is introduced into the chamber, and then the substrate is introduced into the chamber.

  Needless to say, the tungsten thin film can be formed by the method shown in the above-mentioned prior art.

  In purging HF in the chamber, it is important to optimize the chamber temperature, the concentration of SiH 4 introduced into the chamber, the flow rate, etc., in order to reliably purge HF in a short time.

  The chamber temperature is preferably 300 to 500 ° C, more preferably 400 to 500 ° C. If the chamber temperature is 300 ° C. or higher, HF reacts with SiH 4 at a sufficient rate, and if it is 500 ° C. or lower, silicon powder adheres to the chamber due to decomposition of SiH 4, and the substrate is grown during the subsequent growth of the tungsten film. No silicon powder is deposited.

  The SiH4 partial pressure is preferably in the range of 0.1 to 3 torr, more preferably 0.5 to 2 Toor. If the SiH4 partial pressure is 0.1 torr or more, HF reacts with SiH4 at a sufficient rate, and if it is 3 torr or less, silicon powder adheres to the chamber due to excess SiH4, and the substrate is grown during the subsequent growth of the tungsten film. No silicon powder is deposited.

  The flow rate of SiH4 at the time of purging is preferably in the range of 100 sccm to 300 sccm. If the HF purge is performed under these conditions, the purge time is completed in about 3 to 20 seconds, so that the cycle time for growing the tungsten thin film becomes long and the tungsten growth process does not become long.

  It is preferable to use an inert gas (Ar, N2) and / or H2 gas such as argon gas or nitrogen gas as the carrier gas at the time of HF purge. An inert gas (Ar, N2) and / or H2 gas such as argon gas or nitrogen gas will not affect the reaction between HF and SiH4.

  After the HF purge is completed, an inert gas is introduced into the chamber, and then the semiconductor substrate is introduced into the chamber.

1 is a schematic cross-sectional view of a semiconductor device of the present invention. The figure which shows the manufacturing method of this invention. The figure which shows the change of the fluorine density | concentration which measured the HF density | concentration in a chamber with the quadrupole mass spectrometer.

Explanation of symbols

1 Semiconductor substrate 2 Interlayer insulating film 3 Barrier film 4 W film

Claims (4)

WF6 gas and H2 gas are introduced into the chamber using the contact hole of the semiconductor device having an insulating film formed on the semiconductor substrate and at least a contact hole penetrating the insulating film as a source gas, and the semiconductor substrate A method of manufacturing a semiconductor device embedded by forming a tungsten film thereon,
An HF barge process for introducing SiH4 gas into the chamber before introducing the semiconductor substrate into the chamber, and purging HF in the chamber;
Thereafter, an inert gas is introduced into the chamber,
And a step of introducing a semiconductor substrate into the chamber.   2. The method of manufacturing a semiconductor device according to claim 1, wherein a partial pressure of the SiH 4 gas in the HF purge step is 0.1 to 3 torr.   2. The method of manufacturing a semiconductor device according to claim 1, wherein a carrier gas of SiH4 gas in the HF purge process is an inert gas and / or a hydrogen gas.   2. The method of manufacturing a semiconductor device according to claim 1, wherein the temperature of the chamber in the HF purge step is 300 to 500 ° C. 3.

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