JP2594702B2 - Silicon oxide film and semiconductor device having the same - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a silicon oxide film and a semiconductor device having the same, and more particularly, to a silicon oxide film having a large binding energy with oxygen and a semiconductor device having the same.

BACKGROUND ART Conventionally, as a semiconductor device, a device in which an insulating film is formed by a thermal oxidation method is known. In this method, a dry oxygen or the like mixed with a trace amount of hydrogen chloride, a dry oxygen or a water-containing oxygen, or the like is applied to a silicon substrate at a high temperature (for example,
This is a method of forming an oxide film by contacting at a temperature of 600 ° C. or higher. However, this method has a drawback that the temperature for forming an oxide film is high and a low-temperature process cannot be realized.

The importance of the low-temperature process will be described below by taking the formation of an oxide film of a MOS LSI as an example.

The progress of LSI technology is extremely rapid, and DRAMs of 1 Mbit or more are already in practical use. In order to manufacture such high-performance electronic devices, that is, fine and ultra-high-density devices, it is naturally necessary to have a more controllable and higher-performance manufacturing process that is less affected by uncertain factors. Become. As a high-performance manufacturing process, there is a low-temperature process.

For example, lowering the temperature at which an oxide film is formed reduces the amount of impurities released from the material constituting the reaction system, reduces the trap density in the oxide film due to the impurities and at the interface between the oxide film and the silicon, and increases the electrical conductivity. It is necessary to realize a highly stable semiconductor device.

Also, lowering the temperature of the process is effective for reducing the warpage of the silicon substrate, the strain and the defect density in the material of the semiconductor device configuration.

Furthermore, if the formation temperature of the oxide film is about 600 ° C. or less, it is possible to form the oxide film after forming a metal or alloy (for example, aluminum metal) having a low melting point. realizable. In particular, when the temperature is 500 ° C. or lower, hillocks are not formed on the aluminum thin film, which is particularly effective.

As described above, lowering the formation temperature of the oxide film is indispensable for realizing an ultra-miniaturized LSI.

However, since the conventional technology is a high-temperature process, an ultra-miniaturized LSI and thus a high-performance semiconductor device have not been realized.

An object of the present invention is to provide an oxide film having excellent insulating properties,
Another object of the present invention is to provide a high-speed semiconductor device having high conductance and a short channel.

DISCLOSURE OF THE INVENTION The object of the present invention is to provide a silicon oxide having a bonding energy at the Si _2P peak of silicon bonded to oxygen which is _4.1 eV or more larger than the bonding energy of the Si _{2P3 / 2} peak of silicon bonded to silicon in the X-ray photoelectron spectroscopy spectrum. This is achieved by a film and a semiconductor device including the film.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a graph showing a temporal change in the thickness of an oxide film formed on a silicon surface in ultrapure water. FIG. 2 is a sectional structural view of a semiconductor device according to an embodiment of the present invention. FIG. 3 is a sectional view showing a manufacturing process of the semiconductor device of the present invention.

11 substrate back surface of the electrode, the p ⁺ substrate 12, the n ⁺ buried region 13, the high-resistance regions 14, 15 high-resistivity n ^- region, 16 denotes an insulating isolation region, 17 and 18 n ⁺ region, 19 , 20 is the p ⁺ region, 21,22,23,24
Is a metal silicide, 25 and 26 are silicon oxide films (gate insulating films), 27 and 28 are gate electrodes, 29, 30, 31 are metal electrodes, 32,
33 and 34 are metal fluorides (AlF ₃ ), and 35 is a PSG film and a nitride film.

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention will be described with reference to the drawings.

The oxide film of the semiconductor device according to the present invention may be formed, for example, by the following method.

That is, a first step in which an aqueous solution containing oxygen and / or a molecule containing oxygen and having an impurity concentration of 1 ppm or less is brought into contact with the surface of a substrate on which an oxide film is to be formed to form an oxide film on the surface of the substrate; Forming a substrate surface in the oxide film by heat-treating the oxide film at a temperature of 20 to 600 ° C. in a gas phase of an oxygen-containing molecule or an inert gas or a mixture of two or more thereof. A second step of strengthening the bond between atoms and oxygen, and a method of forming an oxide film, which is characterized by at least the following (a patent application filed on the same day).

 First, this method will be described.

FIG. 1 is a graph showing a temporal change in the thickness of an oxide film formed on a silicon surface when a silicon substrate is immersed in ultrapure water in which 9 ppm by volume of oxygen is dissolved. The thickness of the oxide film was measured using an ESCA device and an ellipsometer. The horizontal axis in FIG. 1 represents the time of immersing the silicon substrate in ultrapure water at 23 ° C., and the vertical axis represents the thickness of the oxide film formed on the surface of the silicon substrate. The upper numerical value in FIG. 1 represents the dissolved amount of oxygen in ultrapure water.

As shown in FIG. 1, for example, an oxide film having a thickness of 4.2 nm can be formed by holding a silicon wafer in ultrapure water having a dissolved oxygen content of 9 ppm at room temperature for 46 days.

Table 1 shows the oxide film formed in the ultrapure water (film thickness 4.2n).
m) is heated in an oxygen gas or an oxygen gas at 500 ° C. for 1 hour, and is a data on a change in a thickness of an oxide film and a 15 energy of a bond between silicon and oxygen in the oxide film.

The binding energy values in Table 1 show the binding energy of the Si _2P peak of silicon bonded to oxygen and the Si energy of silicon bonded to silicon in the X-ray photoelectron spectroscopy spectrum.
The difference from the binding energy of the _{2P3 / 2} peak is shown.

The thickness of the oxide film when heat-treated (annealed) in oxygen gas has increased to 4.9 nm. The thickness of the oxide film when heat-treated in nitrogen gas is slightly reduced to 3.98 nm.
The binding energy of the oxide film is increased by the heat treatment in both the oxygen gas and the nitrogen gas. The binding energy of the oxide film thus heat-treated is larger than the binding energy of the oxide film formed by heating the silicon surface to 800 ° C. in dry oxygen. Therefore, in this method, for example, when a silicon substrate is immersed in ultrapure water having a dissolved oxygen content of 9 vol ppm and then heated in an oxygen gas or a nitrogen gas, the silicon substrate has a thickness of 3 nm or more and has a thickness of 3 nm or more. It was clarified that an oxide film with a strong bond can be formed at a low temperature.

In conventional thermal oxidation, an oxide film having a large binding energy of 3 nm or more cannot be formed at a temperature of 600 ° C. or less. However, an ultra-clean atmosphere from which impurities such as moisture and carbon dioxide have been removed (impurity concentration of several tens ppb or less, more preferably several p
The present inventors have separately found that at 800 ° C. for 20 minutes, an oxide film of 4.81 nm can be formed and an oxide film having a binding energy of 4.64 eV can be formed at 800 ° C. × 20 minutes. However, this oxide film cannot be used when the electrode regions 29, 30, 31 are Al in the semiconductor device shown in FIG. 2 described later. Regions 29, 30, 31
Can be used when it is made of a high melting point material such as Mo, W, Ta, Ti, Pb or a silicide of these metals. However, in the present method, the regions 29, 30, and 31 can be used not only when the high melting point material is used, but also when Al is used, and further, the engagement energy can be made larger than 4.64 eV. .

The aqueous solution containing oxygen and / or a molecule containing oxygen in the first step of the method includes, for example, an aqueous solution in which oxygen is dissolved, an aqueous solution in which ozone is dissolved, an aqueous solution of hydrogen peroxide, an aqueous solution of sulfuric acid / hydrogen peroxide, an aqueous solution of hydrochloric acid / hydrogen peroxide. Hydrogen oxide aqueous solution, ammonia / hydrogen peroxide aqueous solution and the like can be mentioned. In addition, for example, an aqueous solution in which oxygen is further dissolved in a hydrogen peroxide solution may be used.

In the first step of the method, a solution containing the oxygen and / or the molecule containing oxygen is brought into contact with the surface of the substrate to form an oxide film on the surface of the substrate. Note that it is preferable that the solution be brought into contact with a catalyst that promotes the decomposition of molecules contained in the solution, since an effect of increasing the formation rate of an oxide film is observed.
Therefore, for example, when a substrate is brought into contact with a solution having a dissolved oxygen content of 0.1 ppm by volume, the use of a catalyst makes it possible to use a starting solution having a volume of 0.1 ppm by volume or less. Examples of the solid catalyst include platinum and the like. Particularly, when an aqueous solution of hydrogen peroxide is brought into contact with the platinum catalyst, hydrogen peroxide (H ₂
O ₂ ) generates oxygen radicals, and the effect of increasing the formation rate of the oxide film is remarkably recognized. For example, a 1 nm oxide film is formed in 30 minutes at room temperature, and 24 nm in a temperature range of 70 to 85 ° C.
An oxide film of 2 to 5 nm is formed in a short time. That is, an oxide film (for example, a gate oxide film in a MOS LSI) can be obtained within a sufficiently practical time.

It is desirable that the hydrogen peroxide solution does not contain a stabilizer, and the amount of TOC contained in the hydrogen peroxide solution is at least 1 pp.
m, preferably 0.1 ppm or less. Also in other aqueous solutions, the amount of unavoidable impurities is 1 ppm or less.
More preferably, it is 0.1 ppm or less.

In the first step of the method, when the dissolved amount of oxygen or oxygen-containing molecules in the aqueous solution containing oxygen and / or oxygen-containing molecules is set to 0.1 ppm by volume or more, an oxide film is formed on the surface of the silicon substrate. Formation is observed in a relatively short time, and the larger the dissolved amount of oxygen or molecules containing oxygen, the higher the formation rate of the oxide film. Note that, for example, 0
The upper limit of the amount of oxygen that can be dissolved in an aqueous solution at a temperature of 14 ° C. is 14 ppm at about 1 atm. For example, the amount of dissolved oxygen may be increased as follows. That is, increasing the amount of oxygen or molecules containing oxygen dissolved in the aqueous solution can be achieved, for example, by immersing the silicon substrate in ultrapure water in a closed container, putting oxygen gas in the closed container, By increasing the pressure of the In addition, oxygen and / or
Alternatively, the upper limit of the dissolved amount of oxygen-containing molecules is preferably 10,000 ppm by volume.

As the oxygen-containing molecule used in the second step of the method, the same molecules as in the first step can be used in the gas phase. Examples of the inert gas include a nitrogen gas, an argon gas, and a helium gas. The oxygen, the molecule containing oxygen, or the inert gas can be used as it is or a mixed gas thereof. In order to further increase the binding energy, the concentration of such impurities (moisture or hydrocarbons) in the gas phase is preferably several tens ppb or less, more preferably several ppb or less, and 0.1 ppb or less.
More preferably pb or less.

When oxygen or a molecule containing oxygen is contained in the gas phase in the second step, an effect of further increasing the thickness of the oxide film is recognized. Further, the effect of increasing the thickness of the oxide film is more remarkably recognized as the number of oxygen or molecules containing oxygen contained in the gas phase increases.

The temperature of the oxide film in the second step is preferably from 20 to 600 ° C., more preferably from 100 to 500 ° C., but a temperature closer to 500 ° C. is more practical because the purpose is achieved in a short time and the practical meaning is large. preferable.

The heat treatment temperature in the second step is desirably as high as the wafer state allows. The pressure of the gaseous phase is not particularly limited, and may be any pressure range of reduced pressure, normal pressure, and pressurized state.

Next, a semiconductor device according to an embodiment of the present invention will be described with reference to the drawings.

FIG. 2 is a sectional view of a semiconductor device showing the embodiment.

Here, only a pair of CMOSs included in the semiconductor device is shown. In FIG. 2, 11 is an electrode on the back of the substrate, 12 is a p ⁺ substrate, and 13 is
n ⁺ buried region, 14 is a high-resistance p ^- region, 15 is a high-resistivity n ^- region, 16 is an isolation region, 17, 18 is an n ⁺ region, 19, 20 is a p ⁺ region, 21, 22, 23, 24 is MoSi ₂ , WSi ₂ , TaSi ₂ , TiSi ₂ or Pd ₂
A metal silicide such as Si; 25, 26 a silicon oxide film (gate insulating film) formed by the above method; 27, 28 a gate electrode; 29, 30, 31 a metal electrode such as Al, AlSi or AlCu; , 33 and 34 are metal fluoride films for insulating and separating the electrodes 27, 28, 29, _{30 and 31} (for example, AlF ₃ when Al is used as an electrode), and 35 is a PSG film or a nitride film for passivation. is there.

In FIG. 2, the interface between the gate insulating film 25 and the region 14 is the region 17, 1
The interface between the gate insulating film 26 and the region 15 is formed closer to the region 5 than the interface between the regions 19 and 20 and the region 15. In this structure, the short-channel effect is less likely to occur because the electric field intensity between the source and the drain in the channel portion is reduced.

In FIG. 2, the material of the gate electrodes 27 and 28 desirably has a high diffusion potential in both the n ⁺ regions 17 and 18 and the p + regions 19 and 20. For example, when Al, AlSi or AlCu is used, a high diffusion potential can be obtained. Al has a diffusion potential of about 0.7 V for the n ⁺ region and about 0.4 V for the p ⁺ region. Of course, the work function value of the gate electrode
Any material having a high barrier to both the n ⁺ region and the p ⁺ region may be used, and a refractory metal or a metal silicide may be used. Therefore, the resistance of the gate electrode is small. Alternatively, in this structure, the diffusion potential of p ⁺ substrate 12 and gate electrode 27 for the n ⁺ source region, and for the p ⁺ source region
By the diffusion potential of n ⁺ buried region 13 and gate electrode 28,
A potential barrier is created in the channel and the channel regions 14, 15
With the impurity density of about 10 ¹⁴ to 10 ¹⁶ cm ⁻³ , normally-off characteristics of a MOS transistor are realized. That is, region 14
The region 15 is a high-resistance region, and the impurity concentration is kept low. Therefore, the channel width through which the electron holes flow is kept wide, and a short channel can be realized without a decrease in the movement of carriers running in the channel. In other words, the large MOS transistor transconductance g _m.

In FIG. 2, the junction surface between the n ⁺ region 17 and the region 14, the junction surface between the n ⁺ region 18 and the region 14, the junction surface between the p ⁺ region 19 and the region 15, and the p ⁺ region 20 and the region 15 Is a flat surface and the area of the bonding surface is small, so that the fringe effect is small and the capacitance between the source region and the drain region, between the source region and the substrate, and between the drain region and the substrate is small.

In FIG. 2, the material of the electrodes 29, 30, 31 is, for example, A
l, AlSi, AlCu, AlCuSi, and the resistance of the source electrode and the drain electrode is small. Source resistance, drain resistance, the gate resistance is small, also the source, on the drain capacitance is small, because a large transconductance g _m, an excellent transistor speed performance. Of course, the source electrode and the drain electrode may be made of a metal such as Mo, W, Ta, or Ti.

As described above, with the semiconductor device having the structure including the oxide film formed by the present method, a semiconductor integrated circuit using an insulated gate transistor excellent in ultra-high speed can be realized.

In FIG. 2, an n ⁺ buried region 13 is provided as a substrate.
Although the p ⁺ substrate 12 has been described, the operation of the semiconductor device described above can also be realized using an insulating substrate such as sapphire, spinel, quartz, AlN, or SiC.

Next, an example of a manufacturing process for manufacturing the semiconductor device of FIG. 2 is shown in FIG. The case where a p ⁺ substrate is used as the substrate 12 will be described. In the region 13 of the p ⁺ substrate 12, an n + buried region is formed by thermal diffusion of P from a PSG film deposited by, for example, a CVD method. Of course, the region 13 may be formed by P or As ion implantation and activation annealing. Isolation region 16, p ^- region
The 14, n ^- region 15 is formed, for example, as follows. After thermally oxidizing the surface of the substrate 12 having the buried region 13 by about several tens of nm, a PSG film or a BPSG film is formed to a predetermined thickness by a CVD method. The thermal oxide film and the PSG film or the BPSG film corresponding to the regions 14 and 15 are removed by reactive ion etching. Subsequently, CVD using SiH ₄ , Si ₂ H ₆ or SiH ₂ Cl ₂
The regions 14 and 15 are selectively epitaxially grown by the method.

In this way, the structure shown in FIG. 3A is formed, but the structure is not limited to the above method and may be formed by any other method. Note that the thickness of the regions 14 and 15 may be appropriately selected depending on the device to be formed, and may be, for example, a value of about 0.03 to 0.5 μm.

Next, a metal layer having a thickness of 10 to 20 nm, for example, a layer made of W, Ta, Ti, Mo, or the like is selectively grown on the surfaces of the regions 14 and 15. Thereafter, for example, As is applied to the region 14 and B is applied to the region 15 by ion implantation through these metal layers.
By selectively implanting Si and then performing activation annealing, silicide layers in regions 21 and 23, n ⁺ region 17 and p ⁺ region 19 are formed as shown in FIG. 3 (b). Next, for example, an Al film having a thickness of about 0.2 to 1.0 μm is formed by a sputtering method or a CVD method, and a predetermined region is etched by reactive ion etching as shown in FIG. 3C. The surfaces of the regions 29, 30, 31 are fluorinated using ultra-high-purity F ₂ gas, for example, at 100 ° C. for about 4 hours, and then
Annealing is performed at 150 ° C. for 5 hours in an inert gas (for example, N ₂ gas) to form an AlF ₃ insulating layer (regions 32, 33, and 34 in FIG. 4D) on the surface of the Al region. Next, FIG. 3 (d)
As shown in (1), using the regions 32, 33, and 34 as masks, predetermined regions of the metal silicide layer, the n ⁺ region, and the p ⁺ region are etched by reactive ion etching to form contact holes.

Next, by performing the above-described processing, an oxide film is formed on the surface exposed from the contact hole. That is, as shown in FIG. 3E, an oxide film is formed in the silicide layer, the n ⁺ region, the p ⁺ region, and the n ⁻ region by oxidation at a temperature of 500 ° C. or less.

Further, the structure of the semiconductor device shown in FIG. 2 can be formed by forming the gate electrodes 27 and 28, etching a predetermined region, forming the passivation layer 35, and forming the electrode 11.

(Comparative Test Example) Two silicon wafers were immersed in a 30% hydrogen peroxide (H ₂ O ₂ ) solution immersed in a platinum catalyst for 1 hour. After soaking for 1 hour,
An oxide film of 7 angstroms was formed on the surface of the silicon wafer. This oxide film has the bonding energy of the Si _2P peak of silicon bonded to oxygen in the X-ray photoelectron spectroscopy spectrum and the silicon
The difference from the binding energy of the _{2P3 / 2} peak was 3.99 eV. This oxide film is referred to as an oxide film 1 as a comparative example.

Further, of the two wafers on which the oxide film 1 is formed, 1
8 sheets in nitrogen gas (impurity concentration several ppb or less)
Heat treatment was performed at 00 ° C. for 1 hour. The thickness of the oxide film after this heat treatment is 9 angstroms, and the silicon ₂ p
The difference between the peak binding energy and the binding energy of the silicon Si _{2P3 / 2} peak bound to silicon was 4.22 eV. The oxide film after the heat treatment is referred to as an oxide film 2.

The wafer having the oxide film 1 and the oxide film 2 formed thereon is dried at a moisture content of 0.6 to 1.3 V% and a water concentration of 10 ^-2 ppm to 515 p.
When left in a gas of pm, the oxide film 1 was easily removed by etching, but the oxide film 2 was not etched. Therefore, the oxide film 2 can be used as an etching mask.

When a voltage of 1 V was applied to the oxide films 1 and 2,
While a current of 1 A / cm ² or more flowed through oxide film 1, only a current of 1 × 10 ⁻⁴ A / cm ² flowed through oxide film 2. That is, the binding energy between the Si _2P peak and Si _{2P3 / 2} is 4.1
It can be seen that in the case of eV, extremely high insulating properties are exhibited.

Therefore, if the oxide film 2 is used as, for example, various insulating films (for example, gate insulating films) of MOS transistors, a semiconductor device having excellent characteristics can be obtained. Further, the thickness of the insulating film in various devices can be reduced. For example, the insulating film can be provided as a tunnel insulating film.

INDUSTRIAL APPLICABILITY The silicon oxide film of the present invention is characterized in that, in the X-ray photoelectron spectroscopy spectrum, the binding energy of the Si _2P peak of silicon bonded to oxygen is lower than that of silicon bonded to silicon.
The bond energy is _4.1 eV or more than the binding energy of the _{2P3 / 2} peak, and it has excellent insulating properties and can be used as an etching mask or a tunnel insulating film.

A semiconductor device provided with this oxide film has a high conversion conductance, a short channel, and excellent high-speed performance.

Claims (8)

(57) [Claims] In the X-ray photoelectron spectroscopy spectrum, the binding energy of the Si _2P peak of silicon bonded to oxygen is as follows:
A silicon oxide film that is _4.1 eV or more larger than the peak binding energy of Si _{2P3 / 2} of silicon bonded to silicon. 2. The bonding energy of the Si _2P peak of silicon bonded to oxygen is _lower than that of silicon bonded to silicon.
_2. The silicon oxide film according to claim 1, wherein said silicon oxide film has a binding energy of 4.7 eV or more larger than a peak binding energy of _{2P3 / 2} . 3. A semiconductor device comprising a MOS transistor provided with the oxide film according to claim 1 as an insulating film. 4. The semiconductor device according to claim 3, wherein said insulating film is a gate insulating film. 5. The semiconductor device according to claim 3, wherein said insulating film is a tunnel insulating film. 6. The semiconductor device according to claim 3, wherein the thickness of the oxide film is 0.5 to 10 nm. 7. The silicon oxide film according to claim 1, wherein said oxide film is a mask oxide film for etching. 8. The semiconductor device according to claim 3, wherein a metal fluoride film is provided on at least a part of the insulating film that insulates and separates the gate electrode from the source and drain electrodes.