JPH11111713A - Improvement of insulating film and manufacture of semi conductor device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve an insulating property of an oxide insulating film at a relatively low temperature and within a relatively short time, by effecting a process in which a heat treatment in an atmosphere of O3 (ozone) and a UV/O3 heat treatment are combined. SOLUTION: An O3 heat treatment involves the step of causing active oxygen produced by the thermal decomposition (300 to 500 deg.C) of ozone (O3 ) to penetrate into a film so as to embed oxygen defects with the active oxygen. An UV/O3 heat treatment involves the steps of: injecting ultraviolet rays in an atmosphere of highly concentrated ozone so as to decompose the ozone and obtain active oxygen whose activity is higher than that obtained by the thermal decomposition; and recovering oxygen defects with the active oxygen. The problem that the insulating property obtained by the O3 heat treatment due to an imperfect removal of impurities in the O3 heat treatment can be overcome by effecting the UV/O3 heat treatment. Further, the process time of the UV/O3 heat treatment can be shortened by effecting the O3 heat treatment. As a result, when both treatments are combined, the process time can be reduced by about 1/3 to 1/10 that required for a single process.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for modifying an insulating film used for forming / modifying an insulating film and a method for manufacturing a semiconductor device using the same.

[0002]

2. Description of the Related Art Generally, an insulating film used for a capacitor in a memory device of a semiconductor device, for example, a DRAM, is formed of a CV.
D, which is formed by a method such as thermal oxidation. Specifically, 16M-DR
The thickness of the insulating film (SiO ₂ film) of AM is usually 12 to 15 nm, but it is 7 to 10 nm for 64M-DRAM, and 256 M-DRAM.
In 1G-DRAM, it is required to reduce the thickness to 1 to 2 nm.

When the thickness of the insulating film is reduced, the insulating property of the insulating film is reduced. Therefore, in order to make up for the insufficient capacity of the insulating film, a change in the film material has been studied, and its practical use has been promoted. In recent years, silicon nitride (Si ₃ N ₄ : ε ≒ 7) or tantalum oxide (Ta ₂ O ₅ : ε ≒ 25) having a higher dielectric constant than conventionally used silicon oxide (SiO ₂ : ε ≒ 4) ) Is shifting to a film material (Monthly Semiconductor World1997.2 pp.39-42). For example, since the dielectric constant of tantalum oxide is about six times that of silicon oxide,
An equivalent capacity can be obtained with a film thickness about six times.

[0004] Insulating film characteristics include steps before film formation, and
And impurities introduced during film formation, and oxygen defects in the film
It has been known that the presence of is greatly involved. Of impurities
Introduction and generation of oxygen vacancies in the film largely depend on the film formation method.
For example, Ta (OC_TwoH _Five)_FiveMetal organic like
When an insulating film is formed by a CVD method using a compound as a raw material,
Impurities of carbon (C), hydrogen (H), etc., which are components of the processing gas
Many are taken in as things. Impurities and oxygen vacancies
In the case of
The flow and insulation are reduced. In order to improve insulation
To remove impurities in the film and repair oxygen defects
Film quality has been improved, and various methods are known.
You.

[0005] Among them, the most common rapid thermal oxidation (RTO:
R apid T hermal O xidation) method, for example using a halogen lamp in an oxygen atmosphere, a method of rapidly heating at about 800 ° C., to evaporate the impurities by heating to a high temperature, also the oxygen defects by thermal oxidation It is possible to repair.

[0006] The plasma method is a method in which plasma is generated in an oxygen atmosphere, oxygen defects are repaired by plasma oxygen / active oxygen, and the plasma oxygen is combined with impurities in an insulating film and removed. . The processing temperature at this time is generally about 300 to 500 ° C., and some of the impurities are also removed by evaporation.

Further, the O ₃ heat treatment method uses ozone (O ₃ )
This is a method in which active oxygen generated by thermal decomposition (300 to 500 ° C.) is permeated into the film to bury oxygen defects. The impurities evaporate by heating and react with active oxygen to be removed.

[0008] The UV / O ₃ heat treatment method decomposes ozone by irradiating ultraviolet rays (low-pressure mercury lamp) in a high-concentration ozone atmosphere. Obtain oxygen to repair oxygen vacancies. At this time, since heating (300 to 500 ° C.) is performed, active oxygen is also generated by thermal decomposition. On the other hand, most of the impurities are evaporated and removed by heating.

This method has attracted attention because it can be processed at normal pressure and has high insulation properties. For example, Japanese Patent Application Laid-Open No. 4-3288862 and "Applied Physics
60, 11 (1991), pp. 1115-1118. In the above publication, a tantalum oxide film deposited by a CVD method is subjected to a UV / O ₃ heat treatment (300 ° C.) and then a dry O ₂ heat treatment (800 ° C.).
This dry O ₂ heat treatment is generally performed in a quartz crucible for about 30 minutes while applying high frequency (Furnace An
neal), which is performed to crystallize an insulating film in an amorphous state by deposition. As a result, a dielectric strength similar to that of the tantalum oxide film deposited by the sputtering method can be obtained.

In a semiconductor device in which an electrode is formed on the surface of an insulating film, especially when an electrode made of titanium nitride is formed on the surface of the insulating film made of tantalum oxide, O ₃
In an insulating film in which oxygen vacancies are supplemented by a heat treatment method, oxygen atoms in the insulating film are easily bonded to titanium and deprived. On the other hand, when high energy is applied by the UV / O ₃ heat treatment method, there is an advantage that the bonding between oxygen atoms and titanium is suppressed.

[0011]

The RTO method has a large effect on the insulating film and its peripheral parts due to the high processing temperature. In this case, there is a problem in that SiO ₂ is formed between the electrodes to lower the capacity, and when the lower electrode is made of metal, the film is peeled off. In addition, although the plasma method can be processed at a relatively low temperature (500 ° C.), an expensive apparatus for generating plasma is required, and the obtained insulation has large variations among individuals. .

As shown in FIG. 4, the leakage current of an insulating film (Ta ₂ O ₅ ) of about 10 nm treated at 400 ° C. for 5 minutes by using the O ₃ heat treatment method is increased when the applied voltage is increased to 4V. It is increased to about ¹⁰⁴ times in the case of not applying. In addition, a large number of protruding portions are observed in a change accompanying an increase in the applied voltage, and the stability is lacking. This is probably because the removal of the impurities (C, H) is incomplete and still remains in the film. Therefore, when a semiconductor device is manufactured using an insulating film treated by this method, variation among individual devices is likely to occur.

The UV / O ₃ heat treatment method has a disadvantage that the treatment time is long. Specifically, in order to improve the insulation of a tantalum oxide film of about 10 nm to a desired degree,
It takes 30 to 60 minutes when heated to 300 ° C, and 15 minutes when heated to 400 ° C. Also, as compared with the case where the O ₃ heat treatment method is used (FIG. 4), the change with the increase of the applied voltage is smooth and the insulation is stable, but shows a relatively high value on the high voltage side. In FIG. 4, the voltage rises sharply when the voltage exceeds 1.5 V.

[0014] Incidentally, the reason why O ₃ towards the UV / O ₃ heated than heating is smooth change in leakage current, mass of impurities are dispersed by irradiation of ultraviolet rays, flowability of the leakage current is suppressed Can be considered. As described above, conventionally, when the UV / O ₃ heat treatment method is used, it is necessary to carry out a long dry O ₂ heat treatment at about 800 ° C. later for crystallization of the insulating film. There is a problem that requires equipment of.

The present invention has been made in view of such circumstances, and by using both the UV / O ₃ heat treatment method and the O ₃ heat treatment method, the oxide insulating film can be formed at a relatively low temperature in a short time. An object of the present invention is to provide a method of modifying an insulating film capable of improving the insulating property and a method of manufacturing a semiconductor device using the same.

[0016]

According to the first aspect of the present invention,
A method for modifying an oxide insulating film of a semiconductor device, comprising the steps of: _Three
Heat treatment and UV / O_ThreeImplement in combination with heat treatment
It is characterized by that.

[0017] O ₃ instability insulating incompletely due impurity removal in the heat treatment are overcome by the practice of the UV / O ₃ heat treatment. Further, the processing time of the UV / O ₃ heat treatment can be shortened by performing the O ₃ heat treatment, and by combining these, the time can be reduced to about 1/3 to 1/10 of the case of each single treatment. It is possible.
UV / O ₃ heat treatment and O ₃ heat treatment
Since high-temperature heating is not required unlike the method, there is little need to consider the heat resistance of the oxide insulating film and its peripheral portion. As described above, both disadvantages can be compensated for and an advantage can be obtained, so that the insulation can be improved satisfactorily at a low temperature for a short time, and an expensive device is not required. Further, there is no need to perform crystallization at a high temperature for a long time.

The higher the processing temperature is, the shorter the processing time is. However, it is necessary to set an appropriate processing temperature in accordance with various conditions such as film quality, film thickness, film forming method, peripheral portions, and the like. . Considering the film quality, it is considered that, for example, a processing temperature of about 300 to 700 ° C. is appropriate for a tantalum oxide film, and a processing temperature of about 50 to 900 ° C. is appropriate for a silicon oxide film.

[0019] According to a second aspect of the invention, according to claim 1, which comprises carrying out the UV / O ₃ heat treatment after O ₃ heat treatment.

[0020] by O ₃ heat treatment, after the oxygen defect is partially repaired, when subjected to UV / O ₃ heat treatment, ozone UV (and heat) the permeability of degraded by generated active oxygen due to deterioration However, since the surface of the oxide insulating film is not so dense that the penetration of active oxygen is difficult in practice, active oxygen can sufficiently enter during the UV / O ₃ heat treatment. Therefore, the burying of further oxygen defects proceeds favorably. Most of the impurities are evaporated by heating, and the impurities are removed by bonding with active oxygen, and the remaining lump is dispersed by the action of ultraviolet rays during the UV / O ₃ heat treatment.

According to a third aspect of the present invention, in the first aspect, the O ₃ heat treatment is performed after the UV / O ₃ heat treatment.

When the O ₃ heat treatment is performed after the oxygen vacancies are partially repaired by the UV / O ₃ heat treatment, the permeability of the active oxygen generated by the thermal decomposition of ozone seems to deteriorate. Actually, since the surface of the oxide insulating film is not so dense as to make it difficult for active oxygen to pass therethrough, oxygen defects are satisfactorily repaired. Most of the impurities are evaporated by heating, and the impurities are removed by bonding with active oxygen, and the remaining lump is dispersed by the action of ultraviolet rays during the UV / O ₃ heat treatment.

According to a fourth aspect of the present invention, in any one of the first to _third aspects, the wavelength of the UV / O ₃ heat treatment is
It is characterized by using ultraviolet light having a wavelength of 150 to 300 nm.

When irradiated with ultraviolet light having a wavelength of 150 to 200 nm, generation of ozone or active oxygen from oxygen is promoted,
It is known that the effect of decomposing ozone to generate active oxygen is promoted by ultraviolet rays having a wavelength of 200 to 300 nm. Therefore, by using the wavelength in this range, the action of decomposition / generation of ozone can be obtained, and the above-described effects can be obtained.

According to a fifth aspect of the present invention, there is provided a method of manufacturing a semiconductor device.
An oxide insulating film formed on a substrate is modified by using the insulating film modifying method according to any one of claims 1 to 4.

As a result, a high-quality semiconductor device with less leakage current in the oxide insulating film and less product variation can be manufactured.

[0027]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be specifically described below with reference to the drawings showing the embodiments. Embodiment 1 FIG. FIG. 1 is a schematic longitudinal sectional view showing an apparatus used for carrying out the method for modifying an insulating film according to the present invention, and FIG. 2 is a perspective view showing a main part and a peripheral structure thereof. In the figure, reference numeral 1 denotes a cylindrical chamber made of a surface-treated Al material, and a rotatably supported stage 2 is installed in the center of the chamber 1. Stage 2
Has a built-in mechanism for holding the wafer W thereon and a heater for heating the mounted wafer W to a predetermined temperature. An opening 3 for taking in and out the wafer W is provided on a side wall of the chamber 1, and a shutter 4 is attached to the opening 3. An exhaust port 9 is provided on the bottom wall of the chamber 1.

A lamp chamber 6 is connected to the upper side of the chamber 1 and is separated by a circular glass plate 5. In the lamp chamber 6, an ultraviolet lamp 7 having an arc tube formed in a zigzag shape in a plane is provided with its surface facing the surface of the stage 2. The glass plate 5 is provided with a large number of ozone spray holes 8, 8,... For introducing and spraying ozone into the chamber 1 in two orthogonal radial directions. The supply tube 10 passes through the side of the arc tube of the ultraviolet lamp 7.
Are provided, and the supply pipe 10 and each ozone spray hole 8, 8 ...
And are connected. A predetermined flow rate of ozone is supplied to the supply pipe 10 from an ozone generator 11 installed outside the apparatus.

A robot 12 for loading / unloading the wafer W through the opening 3 when the shutter 4 is opened is provided outside the apparatus. The robot 12 moves the wafer W outside the apparatus.
The wafer W is transferred between a wafer cassette 13 for accommodating the wafer W, a positioning stage 14 for positioning the wafer W on the stage 2, and a cooling stage 15 for cooling the wafer W unloaded from the apparatus after the processing. It has been done.

A description will be given of a method of modifying the insulating film in the apparatus configured as described above. First, the wafer W taken out of the wafer cassette 13 by the robot 12 and positioned by the positioning stage 14 is loaded into the apparatus in which the shutter 4 is opened in advance. The stage 2 is heated to a predetermined temperature, the wafer W is heated to that temperature, and is rotated by the rotation of the stage 2. At the same time, a predetermined amount of ozone is supplied from the ozone generator 11 into the chamber 1 through the supply pipe 10 and the ozone spray holes 8, 8,.

In this state, O ₃ heat treatment is performed for several minutes.
Thereafter, the ultraviolet lamp 7 is turned on, and the UV / O ₃
A heat treatment is performed. After the process is completed, the shutter 4 is opened, and the wafer W is carried out of the apparatus by the robot 12. The robot 12 places the unloaded wafer W on the cooling stage 15,
After a predetermined time has elapsed, the cooled wafer W is transferred to a wafer cassette.
Store it in 12.

The wavelength of the ultraviolet light emitted from the ultraviolet lamp 7 is preferably 150 to 300 nm. This is for the following reasons. That is, as a chemical action of ultraviolet rays, 20
Ozone or active oxygen is generated at a wavelength of 0 nm or less, and 200
This is because it is known that at ~ 300 nm, ozone is decomposed to generate active oxygen.

Therefore, specifically, as the ultraviolet lamp 7,
A low-pressure mercury lamp irradiating ultraviolet rays of 185 and 254 nm can be used, or a barrier discharge lamp of 172 nm emission type or 248 nm emission type can be used. When a barrier discharge lamp is used, it emits a single wavelength,
Although it is necessary to select one of the wavelengths, there is an advantage that the apparatus configuration is simple because the blinking point is possible.

The higher the heating temperature of the wafer W by the stage 2, the shorter the processing time and the better the effect can be obtained. However, the quality and thickness of the oxide insulating film, the method of forming the film, and the formation of the wafer W What is necessary is just to set suitably in consideration of the heat resistance of the other component part performed. Considering the film quality, it is considered that, for example, a processing temperature of about 300 to 700 ° C. is appropriate for a tantalum oxide film, and a processing temperature of about 50 to 900 ° C. is appropriate for a silicon oxide film. In addition, MIS (M etal- I ns
ulator- S ilicon) up to 800 ° C. in a tantalum oxide film used in a capacitor structure is susceptible to heating of usually about 500 ° C., it is used in the capacitor of the MIM (M etal- I nsulator- M etal ) structure The limit is about 500 ° C for tantalum oxide films. This is because the lower electrode of the MIM-structured capacitor is changed from conventional Si to a metal (W, Pt, Ru, etc.), so that the lower electrode is peeled off at a high temperature.

In the method of the present invention, the instability of insulation due to incomplete removal of impurities in the O ₃ heat treatment is caused by UV / UV
Overcome by performing O ₃ heat treatment. UV / O
_{(3) The} duration of the heat treatment can be shortened by performing the O ₃ heat treatment, and by combining them, it is possible to reduce to about 1/3 to 1/10 of the case of each single treatment. is there. UV / O ₃ heat treatment and O ₃
Since heat treatment does not require high-temperature heating unlike the RTO method, it is less necessary to consider heat resistance of the oxide insulating film and its peripheral portion. As described above, both disadvantages can be compensated and advantages can be obtained, so that the insulating property can be improved satisfactorily at a low temperature for a short time, and an expensive device is not required.

[0036] by O ₃ heat treatment, after the oxygen defect is partially repaired, when subjected to UV / O ₃ heat treatment, although the permeability of the active oxygen appears to deteriorate, in practice oxide insulating film Since the surface is not so dense that it is difficult for active oxygen to pass therethrough, active oxygen can sufficiently penetrate during the UV / O ₃ heat treatment. Therefore, the burying of further oxygen defects proceeds favorably. Most of the impurities evaporate by heating, and are removed by the combination of the impurities and active oxygen.
Further, the lump remaining after removing the impurities is dispersed by the ultraviolet rays.

By manufacturing a semiconductor device by using such an oxide insulating film reforming process, a high-quality semiconductor device with less leakage current in the oxide insulating film and less product variation can be manufactured.

Embodiment 2 In the present embodiment, FIG.
Processing is performed in the reverse order to that of the first embodiment using the apparatus shown in FIG. That is, the robot 12 causes the wafer cassette 13
, And the wafer W positioned by the positioning stage 14 is loaded into the apparatus in which the shutter 4 is opened in advance. The stage 2 is heated to a predetermined temperature, the wafer W is heated to that temperature, and is rotated by the rotation of the stage 2. At the same time, the ozone generator 11
Supply a predetermined flow rate of ozone into the chamber 1 through the supply pipe 10 and the ozone spray holes 8, 8,.

At this time, the ultraviolet lamp 7 is turned on, and the UV / O ₃ heat treatment is performed for several minutes. Then, the UV lamp 7
Is turned off, and O ₃ heat treatment is performed for several minutes. After the process is completed, the shutter 4 is opened, and the wafer W is carried out of the apparatus by the robot 12. The robot 12 places the unloaded wafer W on the cooling stage 15 and stores the cooled wafer W in the wafer cassette 12 after a predetermined time has elapsed.

In this embodiment, as in the first embodiment, good insulation can be obtained. When O ₃ heat treatment is performed after oxygen vacancies are partially repaired by UV / O ₃ heat treatment, the permeability of active oxygen seems to be deteriorated. Oxygen vacancies are satisfactorily repaired because they are not so dense that it is difficult for active oxygen to pass through.

[0041]

EXAMPLE FIG. 3 shows the insulating property when a Ta ₂ O ₅ film having a thickness of 10 nm formed on a poly-Si subjected to a nitriding treatment by a CVD method was treated under the respective conditions shown in Table 1. The processing temperature was set at 400 ° C., the ozone concentration was 5%, and the flow rate of the ozone generator 11 was 10 liter / min. In sample No. 3, ozone is generated, and the ozone generator 11 is unnecessary.

[0042]

[Table 1]

FIG. 3 shows that the sample Nos.
In sample No. 4, there was almost no difference due to the order of treatment and ultraviolet wavelength, and the leak current was significantly lower in both UV / O ₃ heat treatment alone and sample Nos. 6 and 7 without treatment. It turns out that there is. UV / O ₃ heat treatment is O
_{3 Even after the} heat treatment, it was confirmed that the surface structure was not so dense as to make it difficult for active oxygen to pass therethrough.

In each of sample Nos. 1-4,
There is no instability of the insulation observed only in the O ₃ heat treatment (Sample No. 5), and the temperature gradually changes (increases) with an increase in the applied voltage. As described above, it was found that the method of the present invention can provide excellent insulation properties in a total of 5 minutes of treatment. This was about 3 of the time when equivalent insulation was obtained only by UV / O ₃ heat treatment.

The method of the present invention can be applied to an SiO ₂ film used as a gate insulating film of a transistor.

[0046]

As described above, in the method for modifying an insulating film and the method for manufacturing a semiconductor device according to the present invention, oxygen defects in an oxide insulating film are repaired by active oxygen in which ozone is thermally decomposed by O ₃ heat treatment. Oxygen vacancies are repaired by active oxygen having high energy, which is obtained by decomposing ozone with ultraviolet rays by the UV / O ₃ heat treatment. Further, the impurities in the film are evaporated by heating, and the lump of the impurities is dispersed by the irradiation of the ultraviolet rays. Due to these effects, the present invention has excellent effects, such as the insulating property of the oxide insulating film is significantly improved, the time required for processing is shorter than before, and the apparatus is relatively simple.

[Brief description of the drawings]

FIG. 1 is a schematic longitudinal sectional view showing an apparatus used for carrying out a method for modifying an insulating film according to the present invention.

FIG. 2 is a perspective view showing a configuration of a main part of the apparatus shown in FIG. 1 and its periphery.

FIG. 3 is a graph showing the results of implementing the method of the present invention.

FIG. 4 is a graph showing the results of implementing the conventional method.

[Explanation of symbols]

 2 Stage 7 UV lamp 10 Supply tube 11 Ozone generator W Wafer

Claims (5)

[Claims] 1. A method for modifying an oxide insulating film of a semiconductor device, the method comprising modifying an O ₃ heat treatment and a UV / O ₃ heat treatment in combination. Wherein O ₃ insulating film modification method according to claim 1, which comprises carrying out the UV / O ₃ heat treatment after heat treatment. _{3. The} method according to claim 1, wherein an O ₃ heat treatment is performed after the UV / O ₃ heat treatment. 4. In the UV / O ₃ heat treatment, the wavelength is 150 to
2. An ultraviolet light having a wavelength of 300 nm is used.
4. The method for modifying an insulating film according to any one of Items 3 to 3. 5. A method for manufacturing a semiconductor device, wherein an oxide insulating film formed on a substrate is modified by using the method for modifying an insulating film according to claim 1.