JPS61199639A - Method for oxidation of semiconductor - Google Patents

Abstract

PURPOSE:To enable to uniformly form an oxide film on the surface layer part of a substrate at a high speed by a method wherein strong oxidizing gas is photodecomposed using the energy beam having photodecomposable energy, and the surface of the semiconductor is oxidized by the photodecomposed oxygen atoms in excited state. CONSTITUTION:The laser beam (a) of the XeF excimer laser to be used to heat a substrate in advance is made to irradiate on the silicon substrate 2 arranged in the reaction chamber 3 of an oxide film forming device 1 through the intermediary of a quartz window 4. Besides, the mixed gas of ozone and oxygen, which is the strong oxidizing gas with which the surface layer part of the silicon oxidizing gas to be used to oxidize the surface layer part of the silicon substrate 2 at a high speed by generating photo-decomposition, is sent to a reaction chamber 3, and the laser beam (b) of the KrF excimer laser is made to irradiate as a different beam. The oxygen atoms, which is the constituting atoms of the atmospheric mixed gas of the reaction chamber 3, is photo-decomposed or photo-excited by the laser beam (b), and an oxide film is formed on the surface part of the silicon substrate 2 at a high speed by having the oxygen atoms of said mixed gas to easily couple with the Si atoms which is the constituting atoms of the silicon substrate 2 preheated by the laser beam (a) of the XeF excimer laser.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for oxidizing a semiconductor, and particularly to a method for forming an oxide film on the surface layer of a semiconductor.

[Conventional technology]

In recent years, oxide film formation has become an essential technology in the manufacturing process of semiconductor devices.

Conventionally, methods for forming oxide films on semiconductor substrates such as silicon substrates in the manufacturing process of semiconductor devices include thermal oxidation methods such as dry oxidation and steam oxidation, and vapor phase growth methods. There is.

However, the demand for yield improvement due to technological advances,
There is a demand for not only two-dimensional but also three-dimensional miniaturization, and as a technology to meet these demands, there is a need for a method to form oxide films quickly and with high precision at low temperatures. A short-wavelength pulsed laser that is absorbed by the surface layer of the semiconductor substrate and instantaneously heats the surface layer is irradiated onto the semiconductor substrate in an oxygen atmosphere while keeping the inside of the semiconductor substrate at a low temperature, rapidly oxidizing the surface layer. A method of forming an oxide film is known that not only forms a film but also prevents the occurrence of distortion on the inside thereof.

[Problem that the invention seeks to solve]

As mentioned above, a short wavelength pulsed laser has the advantage of not only being able to form an oxide film at high speed, but also being able to perform oxidation at low temperatures without damaging the inside of the substrate.

However, if the atmosphere is oxygen 02, the oxidation reaction rate on the surface is slow, and not only is it not possible to bring out the performance of a short wavelength laser sufficiently, but also the oxidation reaction is instantaneous and at low temperature, so SiO and 5i02 coexist. There is also a risk that a non-uniform oxide film may be formed.

SUMMARY OF THE INVENTION In view of these problems, an object of the present invention is to provide a method for uniformly forming an oxide film on the surface layer of a semiconductor at high speed.

[Means for solving problems]

The present invention solves the above-mentioned problems by using a semiconductor oxidation method in which a strong oxidizing gas is photolyzed using an energy beam having photolytic energy, and the surface of the semiconductor is oxidized by the photolyzed excited state oxygen atoms. This solves the problem.

[Effect]

By causing the strong oxidizing gas to absorb light, the electron system of the constituent atoms of the strongly oxidizing gas is dissociated or further photoexcited, and the constituent atoms of the strongly oxidizing gas in this excited state and the constituent atoms of the substrate easily undergo an oxidation reaction. Therefore, the oxide film is formed uniformly and quickly.

〔Example〕

Preferred embodiments of the present invention will be described with reference to the drawings.

In the first embodiment, as shown in FIG.
A mixed gas containing 1% 03 gas and 02 gas at a partial pressure of 0.5 atmospheres was used, and KrF was used as a light source to photolyze the gas.
This is an example using an excimer laser (wavelength: 249 nm).

First, in this example, a laser beam a of an XeF excimer laser (wavelength: 350 nm) that heats the substrate in advance is applied to the silicon substrate 2 placed in the reaction chamber 3 of the oxide film forming apparatus 1 through the quartz window 4 .

This XeF excimer laser is a pulse laser,
A laser beam a of the XeF excimer laser is irradiated from above in the figure and heats the surface layer of the silicon substrate 2. This preheating is performed at a temperature of about 900° C. or lower, and therefore does not cause thermal distortion inside the substrate.Furthermore, before and after heating the surface layer of the silicon substrate 2, photodecomposition occurs and the temperature increases at high speed. A mixed gas of ozone and oxygen, which is a strong oxidizing gas that oxidizes the surface layer of the silicon substrate 2, is sent to the reaction chamber 3.

By sending this mixed gas, the atmosphere in the reaction chamber 3 becomes the mixed gas, and the mixed gas in the reaction chamber 3 of the oxide film forming apparatus 1 is irradiated with a laser beam b of a KrF excimer laser as a separate beam. do.

The laser beam b of the KrF excimer laser photolyzes or photoexcites oxygen atoms, which are constituent atoms of the mixed gas in the atmosphere of the reaction chamber 3.

The oxygen atoms of this mixed gas easily combine with the Si atoms, which are the constituent atoms of the silicon substrate 2, which have been preheated by the laser beam a of the XeF excimer laser, so that an oxide film is rapidly formed on the surface of the silicon substrate 2. formed in the part.

To explain this reaction, as shown in Figure 2, there is a relationship between the sea urchin strongly oxidizing gas and the wavelength of the energy beam irradiated, and a relationship between the silicon substrate and the wavelength of the energy beam irradiated. In terms of the relationship between the gas and the wavelength of the irradiated energy beam, when 03 gas is included as the strong oxidizing gas as in this first embodiment,
The photodecomposition of Q3' m O2+ OX generates zero oxygen atoms in an excited state, and the generated zero oxygen atoms in an excited state have a strong oxidizing power, so that a rapid oxidation reaction can be realized.

``Next, regarding the wavelength dependence of the absorption spectrum of ozone contained in the above mixed gas, as shown in Figure 3, Kr
It has been shown that light absorption occurs efficiently at 249 nm, the wavelength of F excimer laser, and the quantum efficiency of photolyzing ozone to generate excited state oxygen atoms at this wavelength is also shown in Figure 4. It can be seen that it is excellent. Therefore, when ozone is irradiated with the laser beam b of the KrF excimer laser, oxygen atoms activated by photolysis and excitation are efficiently supplied, which is a factor in the rapid formation of an oxide film.

Regarding the relationship between the wavelength of the energy beam irradiated with the silicon substrate, the wavelength of the energy beam that heats the silicon substrate 2 is approximately 113 Qnm or less, so that only the surface layer of the silicon substrate can be efficiently heated. Necessary for heating. The preheating described in the first embodiment is performed by the laser beam a of the XeF excimer laser that is directly irradiated onto the silicon substrate 2 as described above.
The wavelength of is 350 nm. Therefore, the laser beam a of the XeF excimer laser used in the first embodiment causes the silicon base f! Only the surface layer 2 can be efficiently heated, and since photolysis and heating are performed using separate light sources, the thickness of the oxide film can be controlled accurately. In addition, depending on the direction of the irradiated light beam, it is possible to cause photolysis near the surface layer or to widen the area where photolysis occurs.
An oxide film can be formed efficiently. Furthermore, by controlling the amount of energy, no thermal distortion occurs inside the substrate, and on the other hand, when the amount of energy is increased, only the surface layer can be melted and oxidized at high speed.

Note that the laser beam for photolysis used in the first example above has a beam of 320 nm in an ozone mixed gas atmosphere.
Any energy beam may be used without being limited to the KrF excimer laser as long as it has a wavelength of m or less. Furthermore, the XeF excimer laser for heating is not limited to this, and any pulsed laser with a wavelength of 1130 nm or less may be used, and it must also be one that heats only the surface layer and causes distortion inside the substrate. Any energy beam may be used.

In the first embodiment, the silicon substrate 2 is not directly irradiated with the laser beam a having photolyzable energy. However, when an energy beam with photodegradable energy is irradiated not only with a strong oxidizing gas but also with a substrate, the heating Phenomena such as the bonding between the constituent atoms of the substrate being severed occur. The oxide film can be formed even more quickly by utilizing the bonding and cutting between the constituent atoms of the substrate. That is, if the substrate is a silicon substrate, the second
As shown in the figure, these phenomena occur at a wavelength of 1130 nm or less for heating and at a wavelength of 2600 nm or less for cutting bonds between constituent atoms of the substrate, and these phenomena are combined with the photodecomposition effect described above. This allows a more rapid oxidation reaction to occur.

In the second embodiment of the present invention, as in the first embodiment, a mixed gas of ozone is used as the strong oxidizing gas, and when the wavelength of the energy beam is 260 nm or less, S
Taking advantage of the fact that bonding breaks between i atoms occur, a KrF excimer laser (wavelength: 249 nm) is used as an energy beam with a wavelength of 260 nm or less to combine bond cutting between atoms and photolysis of the above-mentioned mixed gas. This is an example.

First, in the example shown in FIG. 5, a laser beam C of a KrF excimer laser is applied to a silicon substrate 12 placed inside a reaction chamber 13 of an oxide film forming apparatus 11 through a quartz window 14. The above-mentioned mixed gas, which is a photodecomposable strong oxidizing gas, is sent to the reaction chamber 13 as an atmospheric gas. Laser beam C of KrF excimer laser
is irradiated onto the silicon substrate 12, and this silicon substrate 1
At the same time, the surface layer of silicon substrate 12 is preheated to 900° C. or lower, and at the same time, the surface layer of silicon substrate 12 is
Bonding and cutting of the Si atom, which is the constituent atom of No. 2, is performed. Further, the laser beam C of the KrF excimer laser is also optically absorbed by the above-mentioned mixed gas of ozone and oxygen, which is a strong oxidizing gas, as in the first embodiment, and this optical absorption causes the above-mentioned photodecomposition. 0 oxygen atoms in the excited state are generated. The 0 oxygen atoms in the excited state and the bonded Si atoms easily combine to form an oxide film at a faster rate than the general 5i02 film formation.

In this second embodiment, unlike the first embodiment described above, the effect is not simply photodecomposition, but the bond-cleaved Si atoms and the excited oxygen atoms generated by photolysis easily combine. Due to the combined effect of
It is possible to quickly form an oxide film by taking advantage of the performance of the energy beam, and since preheating, bonding cutting, and photolysis are performed using a single light source, the oxide film formation mechanism is simple and the equipment is easy to use. The above also has advantages. Furthermore, since energy is applied only to the surface layer, no distortion occurs inside the substrate, and it is possible to melt only the surface layer of the substrate and form an oxide film at a higher speed.

Note that the KrF excimer laser that performs the preheating, bond cutting, and photodecomposition functions is not limited to this, and may be any energy beam with a wavelength of 260 nm or less, and may be a laser beam that heats only the surface layer for preheating. energy beams may be used.

Next, a third embodiment of the present invention will be described. The third embodiment is a method of forming an oxide film by the same method as the second embodiment, but uses a low-pressure mercury lamp as the light source.

As shown in Figure 6, a mixed gas of ozone is used as a strong oxidizing gas, and a low-pressure mercury lamp (wavelength 235 nm) is used as an energy beam that causes photolysis and cuts the bonding of Si atoms, which are constituent atoms of the substrate. However, the beam d from the low-pressure mercury lamp irradiates the silicon substrate 22 and ozone, which is a strong oxidizing gas. When using this low-pressure mercury lamp, since the low-pressure mercury lamp itself does not have enough energy to preheat the surface layer of the silicon substrate 22, a separate beam for preheating is required. XeF excimer laser (wavelength 350
r1m) is used. Note that the separate beam for preheating is not limited to this, and may include XeC1 excimer laser, A
Preheating can be performed by using an energy beam having a wavelength of 1130 nm or less, such as an r laser.

The method for forming an oxide film according to the third embodiment is carried out in accordance with the second embodiment, and includes generating oxygen atoms in an excited state through photolysis by irradiating the ozone mixed gas with the beam d of a low-pressure mercury lamp; Silicon substrate 2 of beam d of low pressure mercury lamp
By irradiating Si atoms on the surface layer of the silicon substrate 22 and bonding and cutting the Si atoms in the surface layer portion of the silicon substrate 22, the excited oxygen atoms and Si atoms easily bond, so that an oxide film can be formed at high speed.

Next, as a fourth embodiment, an example using a YAG laser beam (secondary or higher harmonics having a wavelength of 101065n) will be described.

Since the fourth harmonic of the YAG laser beam has a wavelength of approximately 266 nm, it can cause photolysis of ozone gas when a mixed gas of ozone is used as the strong oxidizing gas. As shown in FIG. 7, the fourth harmonic e of the YAG laser beam is irradiated onto a mixed gas of ozone in the atmosphere of the silicon substrate 32, and oxygen atoms in an excited state are extracted from the optical absorption of the ozone gas. bring about

These excited oxygen atoms easily combine with Si atoms, which are constituent atoms of the silicon substrate 32, and quickly form an oxide film. In the case of this embodiment as well, another energy beam can be used for preheating the substrate, and an energy beam with a wavelength of 260 nm or less that cuts the bonding of Si atoms in the surface layer of the silicon substrate 32 or , an energy beam that melts the surface layer of the silicon substrate 32 can be combined.

Finally, as a fifth example, a XeCl excimer laser
An example using a laser beam f (wavelength: 308 nm) will be explained.

Similar to the above embodiment, the above mixed gas of ozone and oxygen is used as a strong oxidizing gas that can be photodecomposed into the atmospheric gas,
A laser beam f of a XeC1 excimer laser is used as an energy beam that photolyzes this mixed gas and heats the silicon substrate 42 with an energy amount of 500 mJ/
When irradiating under the irradiation conditions of 10 pulses per pulse Ill, l) of cd, 35n3 and a total of 800 pulses, the oxidation rate is approximately twice as high as that of the case where only oxygen gas is used as the atmosphere gas. I was able to do it.

Note that in the first to fifth embodiments described above, the strong oxidizing gas used in each embodiment was described as a mixed gas of ozone, but the strong oxidizing gas is not limited to this, and for example, No gas may be used. , N20 gas, NO2 gas, halogen gas such as CI2, gas such as CCl4 or SFs, or a combination thereof. When irradiated with an energy beam, photolysis occurs and the constituent atoms of the substrate are easily destroyed. Anything that combines with
Further, the energy beam can be selected depending on the strong oxidizing gas, and the relationship between these can be selected or combined depending on the wavelength, that is, from the functional aspects of heating, photolysis, and bonding cutting. -For example,
As shown in Figure 2, NO2 gas, N20 gas and 02 gas
When using gas, N O2 is below 244 nm, N
Since 02 is photodecomposed by an energy beam with a wavelength of 230 nm or less and O2 is 175 nm or less, for example, in 02, a Xe resonance lamp, an F2 excimer laser (1A r F excimer laser), etc. can be used, and For N20, an ArF excimer laser, a deuterium lamp, a low-pressure mercury lamp, etc. can be used, and for the above-mentioned 03, the above-mentioned KrF excimer laser 1, the above-mentioned low-pressure mercury lamp, deuterium lamp, XeCl excimer laser, etc. can be used. These energy beams can be used to perform photolysis and easily combine with constituent atoms of the substrate. Furthermore, the energy beam may be a high-order harmonic of various laser beams, or may be an electron beam or an ion beam.

Furthermore, the substrate is not limited to the silicon substrate mentioned above, but may also be a substrate of GaAs, Ta%Mo, AI, etc. In the case of a GaAs substrate, it can be quickly processed without generating arsenic inside the substrate. An oxide film can also be formed.

〔Effect of the invention〕

According to the method for forming an oxide film of the present invention, an oxide film can be formed without causing thermal strain inside the substrate, and activated oxygen atoms can be transferred to, for example, a silicon substrate by photodecomposition of a strong oxidizing gas. Since it can be combined with Si atoms, etc., it is possible to form a high-quality oxide film at high speed.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram showing the method of forming an oxide film by photolysis using a KrF excimer laser according to the first embodiment of the present invention, and FIG. 2 shows the wavelength of the energy beam and its function on a silicon substrate. It is a diagram showing the relationship between the wavelength of the energy beam and the photodecomposition of a strong oxidizing gas,
Figure 3 is a characteristic diagram showing the optical absorption spectrum of ozone, Figure 4 is a characteristic diagram showing the wavelength dependence of the quantum efficiency of photolyzing ozone to generate excited state oxygen, and Figure 5 is a characteristic diagram showing the wavelength dependence of the quantum efficiency of photolyzing ozone to generate excited state oxygen. FIG. 6 is a schematic diagram illustrating an oxide film forming method using a KrF excimer laser according to a second embodiment of the present invention, in which bonding of silicon atoms is cut and a strong oxidizing gas, ozone mixed gas, is photodecomposed; 8 are schematic diagrams illustrating the third embodiment, the fourth embodiment, and the fifth embodiment, respectively, when other light sources are used. 2.12.22.32.42...Silicon substrate a...
...XeF excimer laser laser beam b,,c...
Laser beam d of KrF excimer laser...beam e of low-pressure mercury lamp...fourth harmonic of YAG laser beam r...
...Laser beam patent for XeC1 energy beam Applicant Sony Corporation agent Patent attorney Koike Mima Sakae Tamura - 2nd - 3rd m 4th m 18[fL→ 155m 5g 11' s7 Figure 8 Procedures Fushosho (spontaneous) 1. Indication of the case 1985 Patent side No. 40176 2. Name of the oxidation method for semiconductors 3. Relationship with the person making the amendment Patent applicant's address Address of Tokyo Parts Co., Ltd. 6-7-35 Name (2
18) Sony Co., Ltd. Company Representative: Norio Oga 4, Agent Address: 11, 2-6-4 Toranomon, Minato-ku, Tokyo 105
Mori Building 11th floor Tn (508) 826611t5 Name (6773) Patent attorney Kai Koike (1 other person) 5, Date of amendment order 6, Subject of amendment 7, Statement of contents of amendment, page 16, No. 7 " written in lines 10 to 10
Not limited to the silicon substrate mentioned above, but also GaAs, Ta, M
In the case of a GaAs substrate, a substrate such as A1 may be used, and in the case of a GaAs substrate, J is not limited to the above-mentioned silicon substrate, but may also be a germanium substrate, a compound semiconductor substrate such as GaAs, InP, GaP, etc.
The substrate may be made of metal such as Ta, Mo, or A1;
In the case of substrates such as S, InP, and GaP, the correction is made to ``do not generate arsenic, phosphorus, etc. inside the substrate.''that's all

Claims (1)

[Claims] A method for oxidizing a semiconductor, in which a strong oxidizing gas is photolyzed using an energy beam having energy capable of photolyzing the gas, and the surface of the semiconductor is oxidized by the photolyzed excited state oxygen atoms.