KR20010008509A - Method for manufacturing gate electrode of semiconductor device - Google Patents

Abstract

PURPOSE: A tungsten gate electrode manufacturing method is provided to be capable of prohibiting oxidization reaction of tungsten during thermal oxidization process performed after formation of the gate electrode and thus obtaining a thick oxide film by selectively activating an oxidization reaction of polysilicon. CONSTITUTION: A gate insulating film(14), a doped polysilicon film(16'), a barrier metal film(18') and a tungsten film(20') are sequentially formed on a semiconductor substrate(10). Then, the tungsten film, the barrier metal film and the doped polysilicon film are patterned by means of photography and etch process using the gate mask, thus forming a gate electrode(G). Next, the gate insulating film below the gate electrode is etched. Thereafter, in order to increase oxidization uniformity on the surface of the gate electrode, a thermal oxidization process, by which the mixture gas of H2 and H2O gas are supplied into the reaction chamber, is performed to form a uniform oxide thin film(22) on the substrate including the gate electrode.

Description

Tungsten gate electrode manufacturing method of semiconductor device {Method for manufacturing gate electrode of semiconductor device}

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a semiconductor device, and more particularly, to a method for manufacturing a tungsten gate electrode in a semiconductor device for improving low resistance of an element.

As semiconductor design rules become more sophisticated, semiconductor devices are manufactured in a multilayered and complex structure. Furthermore, in order to achieve high-speed operation due to high integration of semiconductor devices, instead of a single layer of doped polysilicon, doped polysilicon and metal silicide, for example, tungsten silicide, are replaced by a wiring of a polyside structure in which stacks are sequentially stacked. .

Recently, a doped polysilicon film has been developed to replace the conventional tungsten polyside (tungsten / polysilicon) gate electrode in view of improving the signal processing speed due to high integration and high integration of tungsten at high temperature thermal stability. Gate electrodes in which / barrier metal films / tungsten films are stacked are used in next-generation semiconductor devices.

Such a tungsten gate electrode generally deposits a doped polysilicon film by embedding a gate insulating film on a silicon substrate as a semiconductor substrate, and deposits a tungsten nitride film (WNx) to a titanium nitride film (TiNx) as a barrier metal thereon. . Then, tungsten is deposited thereon, and a photo-etching process using a gate mask is performed to form a pattern of the gate electrode. In this case, the etching process generally uses a dry etching process using plasma having excellent pattern alignment.

Then, oxidation is performed by a high temperature heat treatment process on the entire surface of the substrate including the gate electrode surface in order to smoothly proceed the impurity ion implantation process for the LDD to be performed later while reducing damage to the gate insulating film and the silicon substrate generated by the plasma etching process. Form a thin film.

However, since tungsten is usually easily oxidized by O ₂ or H ₂ O at a temperature of 400 ° C. or higher, a reducing gas such as H ₂ or a less reactive N ₂ gas is introduced into the reaction chamber during the high temperature oxidation process. It is necessary to suppress tungsten oxidation in the electrode.

In addition, in the reducing H ₂ gas atmosphere during the oxidation process, the loss of the doped polysilicon occurs due to the reduction of silicon, and further, the volume increases due to the oxidation reaction of the polysilicon, which has been lost in the etching process. In order to compensate for the loss of silicon and to maintain the vertical gate electrode pattern, the heat treatment process is performed after forming the gate electrode pattern to suppress the oxidation of tungsten by adding some oxidizing agent in a reducing gas atmosphere in consideration of thermal role conditions. A method of selectively oxidizing only polysilicon has been proposed.

In the prior art, H ₂ and O ₂ gas are introduced into the reaction chamber to form H ₂ O gas by reaction of H ₂ and O _{2 in} the form of in-situ, thereby suppressing oxidation of tungsten ( Increasing the oxidation of polysilicon) to proceed to the thermal oxidation process.

However, this chemical reaction occurs in an explosive form at a high temperature, and there is a problem in that the oxidation reaction is not uniform on the wafer because the partial gas irregularity and the gas flow in the reaction chamber are disturbed. However, since the 2H ₂ + O ₂ → 2H ₂ O reaction in the high temperature reaction chamber is mostly explosive, the gas partial pressure of H ₂ and O _{2 in} the reaction chamber is not constant depending on the position of the wafer, The effect is that the oxidation of the tungsten gate electrode is not uniform as a result. In other words, depending on the position of the wafer, the degree of oxidation of the structure varies, so that the oxidation of tungsten occurs at a position where the partial pressure of H ₂ O gas is higher than necessary, and the reduction of polysilicon occurs at the lower side of the H ₂ O partial pressure. An oxidation reaction that does not occur.

An object of the present invention is to solve the problems of the prior art as described above by first mixing the H ₂ / H ₂ O gas in the high temperature thermal oxidation process performed after the gate electrode patterning and inflow into the reaction chamber to perform the oxidation process The present invention provides a method for manufacturing a tungsten gate electrode of a highly reliable semiconductor device by uniformly oxidizing the tungsten and polysilicon on the electrode surface.

1A to 1E are process flowcharts of a tungsten gate electrode according to the present invention;

2 is a graph showing a comparison curve of the oxidation of tungsten and silicon according to the gas partial pressure and the temperature of H ₂ and H ₂ O in order to explain the tungsten gate electrode manufacturing method of the present invention.

Explanation of symbols on the main parts of the drawings

10: silicon substrate 12: device isolation film

14: gate insulating film 16: dot polysilicon film

18: oxide film 20: tungsten silicide film

G: gate electrode

In order to achieve the above object, the present invention provides a method of manufacturing a semiconductor device having a gate electrode in which a gate insulating film is embedded on a semiconductor substrate and a doped polysilicon film / barrier metal film / tungsten film is sequentially stacked. Sequentially stacking an insulating film, a doped polysilicon film, a barrier metal film, and a tungsten film, and performing a photolithography and etching process using a gate mask, and patterning the stacked tungsten film, the barrier metal film, and a doped polysilicon film to form a gate electrode. Forming a layer; etching the gate insulating film under the gate electrode; and thermally oxidizing the H ₂ and H ₂ O gas in advance and supplying them to the reaction chamber in order to increase oxidation uniformity of the gate electrode surface. Forming a uniform oxide thin film on the substrate surface including the gate electrode It characterized by consisting of W.

Hereinafter, with reference to the accompanying drawings will be described a preferred embodiment of the present invention.

1A to 1E are process flowcharts of a tungsten gate electrode according to the present invention.

In the method of manufacturing a gate electrode of the present invention, first, as shown in FIG. 1A, an isolation layer 12 for defining an active region and an isolation region of a device is formed on a silicon substrate 10. The gate insulating film 14 is formed to a thickness of 50 to 100 GPa on the entire surface of the substrate 10, and the doped polysilicon film 16 is formed to a thickness of 500 to 1000 GPa thereon. At this time, the deposition of the doped polysilicon 16 uses SiH ₄ as the reactor body and PH ₃ gas as the dopant. The mixing ratio of SiH ₄ and PH ₃ is set to 1.1: 1.5 to 1.5: 1.8.

Next, as shown in FIG. 1B, the tungsten nitride film WNx to the barrier metal 18 may be used to prevent diffusion of tungsten ions to be formed later on the doped polysilicon film 16 and dopant impurities below. A titanium nitride film TiNx is formed to a thickness of 50 to 100 GPa.

Subsequently, as illustrated in FIG. 1C, tungsten (W) 20 is deposited on the barrier metal to a thickness of 500 to 1000 Å. At this time, the deposition of tungsten (20) is carried out using chemical vapor deposition or physical vapor deposition at a temperature of 500 ~ 650 ℃, using the WF ₆ and H ₂ as the reactor body, the mixing ratio of WF ₆ and H ₂ is 2 ~ It shall be 3.5: 1 to 1.9.

As shown in FIG. 1D, the tungsten film 20, the barrier metal 18, and the doped polysilicon film 16 stacked on the substrate 10 may be formed using a photolithography process using a gate mask and plasma dry etching. Pattern. Accordingly, the tungsten film 20 ', the barrier metal 18', and the doped polysilicon film 16 'are sequentially etched in the active region between the device isolation films 12 of the substrate 10 to form the gate electrode G. To form. Then, the gate oxide film 14 is patterned in accordance with the gate electrode G. FIG.

Subsequently, as shown in FIG. 1E, when the LDD region is formed in the vicinity of the active region exposed by the gate electrode G, the lower portion generated during the plasma etching process of the ion implantation profile is adjusted. A thermal oxidation process at a high temperature (over 800 ° C.) is performed in accordance with the present invention for increasing the oxidation uniformity in the gate electrode surface while compensating for damage to the gate insulating film 12 and the substrate.

In this case, the thermal oxidation process is performed in advance to the outside by mixing the H ₂ and H ₂ O gas to the reaction chamber to provide a uniform oxide thin film 22 on the surface of the substrate 10 including the gate electrode (G) ) Is formed to a thickness of 30 ~ 300Å.

Here, the mixed gas formation of the H ₂ and H ₂ O gas is used to generate H ₂ O at high temperature before flowing into the reaction chamber by mixing the excess H ₂ O ₂ adjusted the flow rate. Alternatively, excess H ₂ may be mixed using a gas flow meter after distilling the liquid H ₂ O from which impurities are removed by distillation or deionization to make water vapor. have. This method allows more precise control of the gas mixing ratio by adjusting the flow rate before mixing H ₂ and H ₂ O. In addition, since the gas state is easier to control the impurity than the liquid state, the purity can be increased by performing an impurity removal process such as filtering H ₂ O steam again.

Then, the gas partial pressure of the mixture H ₂ O is the mean free path of the gaseous molecules according to maintain a low pressure less than the pressure of the reaction chamber, and wherein the partial pressure ratio of H ₂ O to H ₂ gas to 0.2 atmospheric pressure (1.0atm) It becomes long and can improve the uniformity of oxidation.

2 is a graph showing a comparison curve of the oxidation of tungsten and silicon according to the gas partial pressure and the temperature of H ₂ and H ₂ O to explain the tungsten gate electrode manufacturing method of the present invention. Oxidation of (②) shows different equilibrium curves depending on the gas partial pressure and temperature of H ₂ and H ₂ O, respectively.

More specifically, if control in a temperature range between 800 ℃ to 1200 ℃ during the thermal oxidation process of the present invention, the H ₂ O gas partial pressure of the mixed gas of H ₂ / H ₂ O to 0.1 or less while suppressing the tungsten film oxidized Only the polysilicon film can be selectively oxidized.

Usually, each gas partial pressure of the gas mixture is proportional to the mole ratio of the gas, and under constant pressure it is proportional to the volume ratio of the gas. Therefore, the present invention can also obtain the correct partial pressure of the gas by adjusting the pre-mixed H ₂ O gas flow rate using a gas flow meter and the additional reaction between the mixed gases in the reaction chamber is eliminated so that the flow of gas is desired. It is done.

In addition, the present invention has a loading temperature of less than 500 ℃ to prevent the oxidation of tungsten by O ₂ in the atmosphere when loading or unloading the wafer in the reaction chamber, N ₂ , H ₂ , He as an inert gas Or a single gas such as Ar or blown them in a limiting amount. After loading the wafer, in order to suppress the oxidation in the temperature raising process as much as possible, it is preferable that the temperature increase rate up to the oxidation reaction temperature be 5 ° C / min or more.

In addition, the present invention prevents the oxidation reaction of tungsten by blowing a single gas, such as N ₂ , H ₂ , He or Ar, or an excessive amount of the inert gas into the reaction chamber in the reaction chamber after the oxidation reaction is finished.

As described above, the present invention is a H ₂ used in the thermal oxidation process is carried out to reduce the damage of the gate insulating film and the silicon substrate generated by the plasma etching process and to proceed with the impurity ion implantation process for the LDD to be performed later Since the mixed gas of / H ₂ O is mixed before entering the reaction chamber, it is easy to adjust the partial pressure ratio of each component gas in the mixed gas, so that the oxidation reaction of tungsten and polysilicon can be selectively adjusted.

The present invention provides a uniform distribution of the reaction gas in the reaction chamber and ensures uniformity of the oxidizing atmosphere since the gas flow is not disturbed, thereby improving the oxidation characteristics of the tungsten gate electrode.

Claims (7)

A method of manufacturing a semiconductor device having a gate electrode having a gate insulating film embedded thereon and a doped polysilicon film / barrier metal film / tungsten film sequentially stacked thereon, Sequentially depositing a gate insulating film, a doped polysilicon film, a barrier metal film, and a tungsten film on the semiconductor substrate; Performing a photolithography and an etching process using a gate mask to pattern the stacked tungsten film, the barrier metal film, and the doped polysilicon film to form a gate electrode; Etching the gate insulating film under the gate electrode; And In order to increase the uniformity of oxidation on the surface of the gate electrode, a thermal oxidation process of mixing H ₂ and H ₂ O gas in advance and supplying it to the reaction chamber is performed to form a uniform oxide thin film on the substrate surface including the gate electrode. A method for manufacturing a gate electrode of a semiconductor device, comprising the steps of: The method of claim 1, wherein the mixed gas formation of the H ₂ and H ₂ O gas, A method of manufacturing a tungsten gate electrode in a semiconductor device, comprising using H ₂ O at a high temperature before mixing it with excess H ₂ and adjusting the flow rate of O ₂ before flowing into the reaction chamber. The method of claim 1, wherein the mixed gas formation of the H ₂ and H ₂ O gas, A method of manufacturing a tungsten gate electrode in a semiconductor device, comprising distilling H ₂ O in a liquid state from which impurities are removed to make water vapor and then mixing excess H ₂ using a gas flow meter. The gas partial pressure of the mixed H ₂ O, A method of manufacturing a tungsten gate electrode in a semiconductor device, characterized in that the partial pressure ratio of H ₂ O to H ₂ gas is 0.2 or less, and the pressure of the reaction chamber is low pressure of less than or equal to normal pressure. The method of claim 1, wherein the forming of the oxide thin film is performed. The method of manufacturing a tungsten gate electrode of a semiconductor device, characterized in that it is carried out at 800 ℃ or more and the thickness of the oxide thin film is 30 ~ 300Å. The semiconductor device according to claim 1, wherein the loading temperature is 500 ° C. or less to prevent tungsten being oxidized by O ₂ in the atmosphere when loading or unloading a wafer into the reaction chamber during the thermal oxidation process. Tungsten gate electrode manufacturing method. The gas of N ₂ , H ₂ , He, Ar, or the like together to prevent oxidization of tungsten by O ₂ in the atmosphere when loading or unloading a wafer into the reaction chamber during the thermal oxidation process. A method of manufacturing a tungsten gate electrode in a semiconductor device, characterized in that for blowing in excess.