JP2950555B2 - Method for manufacturing semiconductor device - Google Patents

Description

Description: Object of the Invention (Industrial Application Field) The present invention relates to a method for manufacturing a semiconductor device, and more particularly to a method for manufacturing a semiconductor device in which an oxidation step (gate post-oxidation step) after forming a gate electrode is improved. It relates to a manufacturing method.

(Prior Art) As is well known, polycrystalline silicon is widely used as an electrode and a wiring of a semiconductor device. However, signal transmission delay due to resistance of electrodes and wirings has become a serious problem with the increase in integration and speed of semiconductor devices. In particular, in the field of MOS LSI where large capacity and high integration are progressing, polycrystalline silicon used for the gate electrode is shared with the first layer wiring, and the resistance value here is the value of the high speed operation of the semiconductor device. It is an obstacle.

For these reasons, a refractory metal silicide having thermal stability and electrical low resistance is being used as an electrode wiring material instead of polycrystalline silicon. Also,
Recently, attempts have been made to use a high melting point metal such as W or Mo as the gate electrode. Refractory metals such as W and Mo have an electrical resistivity two orders of magnitude lower than that of polycrystalline silicon, and are 1/4 to 1/3 of the resistivity of silicide, making them promising as low-resistance electrode wiring. I have.

As a semiconductor device using the above-described refractory metal (for example, W) as a constituent material of a gate electrode, a semiconductor device having a structure shown in FIG. 4 is conventionally known. That is, 1 in the figure is p
A field insulating film 2 for electrically isolating an element region is formed on the surface of the substrate 1. On the surface of the substrate 1 separated by the field insulating film 2, n ⁺ type diffusion layers 3a and 3b serving as a source and a drain which are electrically separated from each other are formed. These diffusion layers
On the surface of the substrate 1 including the channel region between 3a and 3b, a gate electrode 8 including a polycrystalline silicon layer 5, a metal nitride layer (for example, a TiN layer) 6 and a W layer 7 is provided via a gate oxide film 4. Have been. The metal nitride layer 6 constituting the gate electrode 8 improves the adhesion of the W layer 7 to the polycrystalline silicon layer 4 and also improves the adhesion between the W layer 7 and the polycrystalline silicon layer 4.
Acts as a reaction barrier layer to prevent the resistivity from increasing by one digit.

By the way, in a polycrystalline silicon gate electrode forming step which has been conventionally used, an oxidizing atmosphere (for example, dry oxygen) is used to recover a defect in a thin gate oxide film such as 50 to 500 mm and a gate breakdown voltage deterioration caused by an edge shape of the gate electrode. B) a heat treatment is performed in the step of newly growing a silicon oxide film on the exposed surface of the polycrystalline silicon layer and on the substrate in the source and drain regions. This step is called a post-gate oxidation step.

However, in general, high melting point metals such as W and Mo have no resistance to heat treatment in an oxidizing atmosphere, so that the conventional post-oxidation process cannot be applied to the gate electrode structure shown in FIG. was there.

On the other hand, in the case of the W layer alone gate electrode, water vapor (H ₂ O)
A heat treatment in a hydrogen (H ₂ ) carrier gas containing 10 ppm to 10% of hydrogen. However, when post-oxidation is performed in the above-described gate electrode structure shown in FIG. 4 in such an atmosphere, there is a problem that nitrogen is released from a metal nitride layer, for example, a TiN layer, and Ti is oxidized. Therefore, post-oxidation in a hydrogen-water vapor atmosphere is not an effective solution in a gate electrode structure having a metal nitride layer. Therefore, the post-gate oxidation step cannot be applied, and the gate breakdown voltage is extremely deteriorated, which is an obstacle to the practical use of the high melting point metal gate electrode.

(Problems to be Solved by the Invention) The present invention has been made in order to solve the above-mentioned conventional problems, and it has been proposed that silicon oxide can be formed without causing oxidation of a metal layer and a metal nitride layer constituting a gate electrode in a post-oxidation step. An object of the present invention is to provide a method for manufacturing a semiconductor device in which a film can be grown and a gate breakdown voltage is improved.

[Structure of the Invention] (Means for Solving the Problems) In a method for manufacturing a semiconductor device according to the present invention, an electrode in which a metal nitride layer and a metal layer are laminated in this order on a silicon substrate via a silicon oxide film (for example, Forming a gate electrode); mixing hydrogen, water vapor, and a non-oxidizing gas containing nitrogen to prepare a mixed gas; and a silicon substrate on which the electrode is formed in an atmosphere of the mixed gas. And a step of heat-treating.

Another method of manufacturing a semiconductor device according to the present invention includes a step of forming an electrode (for example, a gate electrode) in which a metal nitride layer and a metal layer are stacked in this order on a silicon substrate via a silicon oxide film; Preparing a mixed gas by mixing carbon dioxide and a non-oxidizing gas containing nitrogen; and heat-treating the silicon substrate on which the electrodes are formed in an atmosphere of the mixed gas. It is characterized by the following.

Examples of the metal nitride include Ti, Zr, Hf, Nb, Ta, W, and Mo.
And nitrides of metal elements belonging to Group IVa, Va or VIa of the periodic table.

Examples of the metal include W, Mo, Al, Cu, Ag, and Au.
And at least one of them as a main component.

Examples of the non-oxidizing gas containing nitrogen include nitrogen alone and a mixture of nitrogen and hydrogen.

The heat treatment may be performed in a temperature range of 800 to 900 ° C.

When nitrogen is used as the nitrogen-containing non-oxidizing gas, it is desirable to set the mixing ratio of the hydrogen, water vapor, and nitrogen as follows. That is, _assuming that the partial pressures of H ₂ , H ₂ O, and N ₂ are P _H2 , P _H2O , and P _N2 , P _H2 / P _H2O is 0.5 or more and 1.0
× 10 ⁹ or less, and logP _N2 is −22 or more and 14 or less. Further, as more preferable conditions, the temperature is 800 to 9
The temperature is preferably set to 00 ° C. At this time, P _H2 / P _{H2O is set} to 1 × 10 ³ or more and 1.0 × 10 ⁴ or less, and logP _{N2 is set} to −2 or more and 2 or less. However, the reducing gas described above in place of H ₂ and H ₂ O,
The present invention can be achieved under the same conditions even when each of the oxidizing gases is used.

In the method of the present invention, when the thickness of the metal layer is increased, stress is applied from the metal layer to the semiconductor substrate or the gate oxide film, and when there are many mobile ions in the metal layer, the mobile ions are transferred to the silicon oxide film. In order to alleviate the stress applied to the semiconductor substrate from the metal layer and prevent diffusion of mobile ions in the metal layer into the silicon oxide film, the silicon oxide film and the metal nitride A polycrystalline silicon layer may be interposed between the layers.

According to the present invention, when heat treatment is performed after forming an electrode (for example, a gate electrode) in which a metal nitride layer and a metal layer are stacked in this order on a silicon substrate via a silicon oxide film, hydrogen, water vapor And a non-oxidizing gas containing nitrogen to prepare a mixed gas, and heat-treat in an atmosphere of the mixed gas to oxidize only silicon without oxidizing a metal layer (for example, a W layer). Can be obtained, and by using a gas containing nitrogen as a carrier gas, a denitrification reaction from a metal nitride layer (for example, a TiN layer) can be prevented. Can be prevented. Therefore, since the silicon oxide film can be grown without oxidizing the metal layer and the metal nitride layer in the post-oxidation treatment in such an atmosphere, a semiconductor device having good gate withstand voltage can be manufactured.

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

First, for example, as shown in FIG.
After a field oxide film 12 is formed on the surface of the silicon substrate 11 by selective oxidation, a thermal oxidation process is performed to cover the surface of the silicon substrate 11 separated by the field oxide film 12 with a thickness of 50 to 300 mm.
The silicon oxide film 13 was formed.

Next, after depositing a polycrystalline silicon layer 14 having a thickness of 500 さ れ with an impurity added on the silicon oxide film 13, the substrate 11 is
N ₂ with Ti as target while maintaining temperature of 73K
TiN layer with a thickness of 500 mm on the polycrystalline silicon layer 14 by sputtering in a mixed gas of Ar and Ar (mixing ratio 50:50)
Fifteen deposited. Subsequently, using a mixed gas of hydrogen (H ₂ ), monosilane (SiH ₄ ) and tungsten hexafluoride (WF ₆ ) by LPCVD, 0.173 torr of H ₂ , 0.013 torr of SiH ₄ and WF ₆ of
Maintain a partial pressure of 0.065 torr and apply a TiN layer 1 at a substrate temperature of 420 ° C.
A W layer 16 having a thickness of about 1500 ° was deposited on the layer 5 (FIG. 1 (b)).
Illustrated). Subsequently, the W layer 16, the TiN layer 15, and the polycrystalline silicon layer 14 are sequentially and selectively etched using ordinary photolithography and reactive ion etching (RIE) to thereby form the gate electrode shown in FIG. 17 was formed.

Next, heat treatment was performed at 800 ° C. in a mixed gas atmosphere containing hydrogen (H ₂ ) and water vapor (H ₂ O) and using nitrogen (N ₂ ) as a carrier gas. This heat treatment is performed, for example, at 1100 K in a N ₂ atmosphere containing 40% of a partial pressure in the range indicated by the hatched portion in FIG. 2 (specifically, H ₂ : H ₂ O = 2000: 1) (at point A). (Shown). By such heat treatment, new oxide films 18 and 19 were grown on the side wall of the polycrystalline silicon layer 14 and the silicon substrate 11, respectively, as shown in FIG. 1 (d), and the gate oxide film became thicker. In the heat treatment, the W layer 16 and the TiN layer 15 constituting the gate electrode 17 were not oxidized at all.
That is, this heat treatment atmosphere is oxidizing to silicon, W
The layer 16 has a reducing property and the TiN layer 15 has an antioxidant property. It is important to select the heat treatment atmosphere so as to exhibit such properties, and therefore, the temperature and the gas ratio are determined as described above. Subsequently, using the field oxide film 12 and the gate electrode 17 as a mask, n-type impurities, for example, arsenic are ion-implanted and activated to form n ⁺ -type diffusion layers 20 a and 20 b serving as a source and a drain on the surface of the silicon substrate 1. did.

According to the present embodiment, the post-oxidation process under the atmosphere can eliminate the withstand voltage defective portion existing in the gate oxide film and increase the thickness of the gate oxide film at the edge of the gate electrode 17 where the electric field is concentrated. Good gate breakdown voltage can be obtained. Further, the gate electrode 17 can be formed of a low-resistance material including the W layer 16. As a result, it is possible to manufacture a highly reliable MOS semiconductor device having a high gate breakdown voltage (breakdown electric field strength), a very short gate delay time, and a miniaturizable gate length of 0.5 μm or less.

In fact, the frequency of the gate breakdown voltage (breakdown electric field strength) in the MOS semiconductor device obtained according to the present embodiment, and the gate breakdown voltage (breakdown electric field) in the MOS semiconductor device (comparative example) shown in FIG. (A) and (B) were obtained, and the results shown in FIGS. 3A and 3B were obtained. FIGS. 3A and 3B show the results of evaluating 100 patterns using a measurement pattern in which 1 million transistors having a gate area of 1 μm ² are connected in parallel. The semiconductor device (FIG. 3 (A)) manufactured in this example has a gate withstand voltage of 8 MV / cm or more, and has an initial short circuit as compared with the semiconductor device of the comparative example (FIG. 3 (B)). (<1MV / cm) or 5MV / cm
No defective mode of less than cm is observed, indicating that the device has good gate breakdown voltage characteristics.

In the above embodiment, hydrogen was used as the reducing gas and water vapor was used as the oxidizing gas. However, when carbon monoxide was used as the reducing gas and carbon dioxide was used as the oxidizing gas, the oxygen potential during the heat treatment was hydrogen-steam. The condition range shown in FIG. 2 can be applied as it is with substantially the same value as in the case of FIG.

Note that, in the above embodiment, the n-type
An example in which the present invention is applied to the manufacture of a channel MOS semiconductor device has been described.
The present invention can be similarly applied to the manufacture of semiconductor devices, MOS capacitors, MOS diodes, and the like.

[Effects of the Invention] As described above in detail, according to the present invention, a silicon oxide film can be grown without causing oxidation of a metal layer and a metal nitride layer constituting a gate electrode in a post-oxidation step, and thus a signal transmission speed is high. In addition, it is possible to provide a method for manufacturing a highly reliable semiconductor device with an improved gate breakdown voltage at a high yield.

[Brief description of the drawings]

1 (a) to 1 (d) are cross-sectional views showing a manufacturing process of a MOS type semiconductor device according to an embodiment of the present invention, and FIG. 2 is a diagram showing hydrogen, steam (or carbon monoxide, FIG. 3 (A) is a characteristic diagram showing a partial pressure condition of carbon dioxide), FIG. 3 (A) is a characteristic diagram showing a gate breakdown voltage frequency of the MOS type semiconductor device manufactured in this embodiment, and FIG. FIG. 4 is a characteristic diagram showing the frequency of the gate breakdown voltage of the MOS type semiconductor device manufactured according to Example). FIG. 4 is a sectional view showing a conventional MOS type semiconductor device. 11 ... p-type silicon substrate, 13 ... silicon oxide film, 14 ...
... polycrystalline silicon layer, 15 ... TiN layer, 16 ... W layer, 17 ...
... gate electrode, 18, 19 ... oxide film, 20a, 20b ... n ⁺ type diffusion layer.

Continued on the front page (58) Fields surveyed (Int.Cl. ⁶ , DB name) H01L 21/336 H01L 29/78 H01L 21/283 H01L 21/316

Claims (4)

(57) [Claims] A step of forming an electrode in which a metal nitride layer and a metal layer are laminated in this order on a silicon substrate via a silicon oxide film; and mixing hydrogen, water vapor, and a non-oxidizing gas containing nitrogen. A step of preparing a gaseous mixture by heat-treating the silicon substrate on which the electrodes are formed in an atmosphere of the gaseous mixture. 2. The mixing ratio of the hydrogen and the water vapor is such that when the partial pressures of the hydrogen and the water vapor are P _H2 and P _H2O , respectively, P _H2 / P _H2O is 0.5 or more and 1.0 × 10 ⁹ or less. The method for manufacturing a semiconductor device according to claim 1, wherein: 3. The non-oxidizing gas containing nitrogen is nitrogen, and the mixing ratio of the hydrogen, the steam, and the nitrogen is such that the partial pressures of the hydrogen, steam, and nitrogen are P _H2 ,
2. The method according to claim 1, wherein P _H2 / P _H2O is 0.5 or more and 1.0 × 10 ⁹ or less, and log P _N2 is −22 or more and 14 or less, where P _H2O and P _N2. . 4. A step of forming an electrode in which a metal nitride layer and a metal layer are laminated in this order on a silicon substrate via a silicon oxide film, a non-oxidizing gas containing carbon monoxide, carbon dioxide, and nitrogen. A method of preparing a gas mixture by mixing the above-mentioned methods, and a step of heat-treating the silicon substrate on which the electrodes are formed in an atmosphere of the gas mixture.