JP2005064244A - Device and method for forming oxide film of semiconductor substrate - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an oxide film forming device of a semiconductor substrate which easily forms a high-quality oxide film on a substrate surface with high throughput, and also to provide an oxide film forming method. <P>SOLUTION: The oxide film forming device forms an oxide film on the surface of the semiconductor substrate. The oxide film forming device at least comprises: a chamber in which the semiconductor substrate is thrown; a retention means for retaining the semiconductor substrate in the chamber; an inert gas supply means for supplying an inert gas into the chamber; an O<SP>-</SP>ion supply means for supplying an O<SP>-</SP>ion into the chamber; and a natural oxide film removal means for supplying a substance for removing a natural oxide film formed on the semiconductor substrate into the chamber. The oxide film forming device includes the oxide film forming method for forming the oxide film on the surface of the semiconductor substrate by using the oxide film forming device. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an oxide film forming apparatus and an oxide film forming method for forming an oxide film on a surface of a semiconductor substrate.

  2. Description of the Related Art In recent years, with higher integration and higher performance of semiconductor elements, an oxide film (insulating film) formed on the surface of a semiconductor substrate such as a gate oxide film of a MOS capacitor has been made thinner. For example, in the case of a MOSFET having a gate length of half micron size or less, the thickness of the gate oxide film is required to be 10 nm or less.

  Usually, a silicon substrate mainly used as a semiconductor substrate is covered with an oxide film having a thickness of about 1 nm called a natural oxide film when exposed to the outside air. However, this natural oxide film contains more dangling bonds, Si—Si bonds, and the like than a thermal oxide film or the like. Therefore, if a natural oxide film is formed on the semiconductor substrate, it is easy to incorporate contaminants such as organic substances and heavy metals into the film, and the incorporated contaminants diffuse into the oxide film and silicon substrate in the thermal oxidation process. As a result, defect levels are formed, which is one of the causes of quality degradation during the manufacture of semiconductor elements.

  Therefore, when forming an oxide film on a semiconductor substrate, in order to obtain a high-quality oxide film, the silicon surface is washed in advance to remove contaminants such as organic substances and heavy metals, and the natural oxide film is removed. Thereafter, it is necessary to form an oxide film on the substrate surface.

For removing contaminants and natural oxide films, methods such as heavy metal removal using heavy metal lift-off by chlorine atoms, organic substance removal using O ₃ gas, and oxide film removal using anhydrous HF have been proposed. . These silicon substrate surface processing methods are generally called dry cleaning methods, and are performed in a vacuum container that maintains a high degree of vacuum. Therefore, contaminants and the like removed from the silicon substrate can be forcibly exhausted to prevent reattachment to the substrate surface, and the surface of the silicon substrate can be cleaned.

  However, even if the surface of the silicon substrate is cleaned in this way, the silicon substrate is exposed to the outside air when the silicon substrate is taken out of the vacuum vessel and transferred to the oxidation furnace to form an oxide film. There is a problem that a natural oxide film is formed again on the surface, and contaminants are taken into the regenerated natural oxide film again.

  Therefore, in order to solve such a problem, in Patent Document 1, a preparation chamber for removing organic substances and a natural oxide film and an oxidation furnace for forming an oxide film are hermetically sealed via a gate valve that can be opened and closed. An insulating film manufacturing apparatus is disclosed in which the gate valve is opened and the semiconductor wafer is moved from the preparation chamber to the oxidation furnace without being exposed to the outside air. By using such an insulating film manufacturing apparatus, the surface of the semiconductor wafer immediately before thermal oxidation can be kept clean, and a high-quality insulating film can be manufactured.

  However, since the insulating film manufacturing apparatus described in Patent Document 1 has a structure in which the preparation chamber and the oxidation furnace are connected in an airtight manner, the manufacturing apparatus itself must be very large, The burden on the cost was great. Furthermore, after removing organic substances and natural oxide film from the semiconductor substrate in the preparation chamber, only the thermal oxidation process (gate oxide film forming process) can be performed. there were.

  Therefore, in Patent Document 2, in order to increase the degree of freedom of the process and reduce the equipment cost, an evacuation process in which a silicon substrate is set in a vacuum vessel and the inside of the vacuum vessel is evacuated by a vacuum evacuation system, and the vacuum vessel A surface cleaning process in which the surface of the silicon substrate is cleaned by a dry cleaning method to remove organic substances and other contaminants and natural oxide films from the surface of the silicon substrate, and the surface of the silicon substrate is protected in the vacuum vessel. A protective film forming step for forming an ultra-thin oxide film is sequentially performed, and then the silicon substrate is taken out from the vacuum container and transferred to the next step, and an insulating oxide film is formed on the surface of the silicon substrate by an oxidizer. The manufacturing method of the oxide film which formed it is disclosed.

However, in such an oxide film manufacturing method of Patent Document 2, when a dry cleaning method is performed on a silicon substrate, the inside of the vacuum vessel must be evacuated to a high vacuum state of 6 × 10 ⁻⁷ Pa or less. A long processing time is required, resulting in a decrease in throughput. In addition, when forming a protective ultra-thin oxide film on the silicon substrate surface, the silicon substrate is heated to about 500 ° C. with an infrared lamp to oxidize the substrate surface, which may cause contamination of the substrate surface again. was there. Furthermore, in Patent Document 2, it is necessary to install an ultraviolet lamp for ozoneizing oxygen gas or an infrared lamp for heating a silicon substrate when removing contaminants in the surface cleaning process. There was also a problem that the structure became complicated.

  Conventionally, a thermal oxidation method, a plasma CVD method, or the like is used as a method for forming an oxide film on a silicon substrate. However, in the case of forming an oxide film using a thermal oxidation method, the oxide film formation region spreads in the plane direction, which has a fatal defect that it cannot cope with higher density and miniaturization of integrated circuits. Even in the case of the plasma CVD method, it is very difficult to control the thickness of the oxide film in a minute oxide film formation region.

  In particular, in recent years, for example, when oxidizing the inside of a trench in a semiconductor substrate, it may be necessary to form an oxide film with directionality. In such a case, it is necessary to cope with thermal oxidation or plasma CVD. Was very difficult. In addition, since the size of the trench is expected to become smaller in the future, it has been desired to develop an oxide film forming method capable of forming an oxide film with directionality in a minute region.

  On the other hand, Patent Document 3 discloses a method of forming an oxide film on a silicon substrate by generating a plasma containing oxygen and irradiating the silicon substrate with oxygen negative ions in the plasma. In this case, it is disclosed that a high frequency bias and / or a direct current bias is applied to the silicon substrate to irradiate the silicon substrate with oxygen negative ions.

  By forming an oxide film on a silicon substrate using such a method, oxidation hardly spreads in the surface direction unlike the thermal oxidation method, and the oxide film is formed with directionality. It became possible to oxidize suitably to a desired depth.

  However, in the oxide film forming method according to Patent Document 3, since the natural oxide film formed on the substrate must be removed by another means, there is a problem that the natural oxide film as described above is re-formed. Furthermore, since a means for generating plasma containing oxygen is required, the apparatus becomes very large and the structure of the apparatus becomes complicated.

JP-A-3-66126 JP-A-7-74165 JP 2002-280369 A Masaaki Nishioka, Zenshin Lee, Masatsugu Sadakata, “Generation of Active Oxygen from Alumina Cement C12A7 Surface”, Proceedings of the Annual Conference of the Electrostatic Society 2002, 29aA-7, pp. 253-256 (2002)

  Therefore, the present invention has been made in view of the above problems, and the object of the present invention is to form a high vacuum state or heat the semiconductor substrate to a high temperature when forming an oxide film on the surface of the semiconductor substrate. Oxide film forming apparatus and oxide film formation of a semiconductor substrate that can easily form a high-quality oxide film on the substrate surface with high throughput without using a large-scale apparatus for generating plasma It is to provide a method.

In order to achieve the above object, according to the present invention, there is provided an apparatus for forming an oxide film on a surface of a semiconductor substrate, comprising at least a chamber into which the semiconductor substrate is placed, and the semiconductor substrate in the chamber. holding means for holding and a inert gas supply means for supplying an inert gas into the chamber, O into the chamber ^- O supplying ions ^- and an ion supplying means, are formed on the semiconductor substrate in the chamber There is provided an oxide film forming apparatus for a semiconductor substrate, comprising a natural oxide film removing means for supplying a substance for removing the natural oxide film.

  In the case of an oxide film forming apparatus for a semiconductor substrate having such a configuration, contaminants can be removed from the semiconductor substrate and a natural oxide film in a normal pressure state (or a state close to normal pressure) without setting the chamber in a high vacuum state. Since the oxide film can be formed at room temperature and normal pressure without exposing the substrate to the outside air, a high-quality oxide film can be easily formed on the substrate surface with high throughput. Thus, the oxide film forming apparatus can be formed. In addition, since the oxide film forming apparatus of the present invention has a simple and compact structure, the burden on the equipment cost can be greatly reduced.

In this case, it is preferable that the O ⁻ ion supply means generates the O ⁻ ions from 12CaO · 7Al ₂ O ₃ and supplies them into the chamber.
12CaO · 7Al ₂ O ₃ is commonly known as alumina cement C12A7, and is a material that can be manufactured from calcium oxide and alumina at a very low cost. Moreover, it has been reported that this material can generate | occur | produce only O < ^- > ion continuously with high selectivity as a negative ion (refer nonpatent literature 1). In the oxide film forming apparatus of the present invention, if the O ⁻ ion supply means generates O ⁻ ions using such 12CaO · 7Al ₂ O ₃ , only the O ⁻ ions are contained in the chamber. It can be supplied continuously and stably. Further, 12CaO.7Al ₂ O ₃ has a very small influence on the human body and the environment, so that handling and disposal of the material can be easily performed, and cost reduction can be expected.

Furthermore, the oxide film forming apparatus for a semiconductor substrate according to the present invention preferably includes an exhaust means for exhausting the chamber.
Thus, if the oxide film forming apparatus includes the exhaust means, for example, before supplying the inert gas from the inert gas supply means, nitrogen or moisture contained in the atmosphere in the chamber is removed by the exhaust means. It can be effectively removed. Therefore, for example, when O ⁻ ions are subsequently supplied into the chamber, it is possible to reliably prevent O ⁻ ions from binding to nitrogen or moisture, so that it is possible to remove contaminants by O ⁻ ions and to form oxide films. Can be done very effectively.

Preferably, the natural oxide film removing means supplies anhydrous HF.
If the natural oxide film removing means supplies anhydrous HF as described above, the oxide film forming apparatus can perform the natural oxide film removal of the semiconductor substrate held in the chamber very effectively.

Further, it is preferable that the inert gas supply means supplies argon gas or helium gas.
If the inert gas supply means supplies argon gas or helium gas in this way, the chamber can be easily filled with an inert gas such as argon gas, so that the substrate is cleaned and the natural oxide film is removed. After that, it is possible to prevent the reattachment of contaminants and the re-formation of the natural oxide film.

At this time, the semiconductor substrate on which the oxide film is formed is preferably a silicon substrate.
As described above, the oxide film forming apparatus for a semiconductor substrate of the present invention can be particularly suitably used when forming an oxide film on the surface of a silicon substrate which is a main material of a semiconductor device, and has a high quality on the surface of the silicon substrate. This oxide film can be formed easily and with high throughput.

Further, according to the present invention, there is provided a method for forming an oxide film on a surface of a semiconductor substrate, wherein the semiconductor substrate is held in a chamber and then an O ⁻ ion is first supplied while supplying an inert gas to the chamber. Introducing and cleaning the semiconductor substrate, then introducing a natural oxide film removing material to remove the natural oxide film formed on the semiconductor substrate, and then introducing O ⁻ ions again to introduce the surface of the semiconductor substrate. An oxide film is formed on the semiconductor substrate, and a method for forming an oxide film on a semiconductor substrate is provided.

  By forming the oxide film on the surface of the semiconductor substrate in this manner, the semiconductor substrate can be cleaned and the natural oxide film can be removed in a normal pressure state (or a state close to normal pressure) in one chamber. At the same time, since the oxide film can be formed at normal temperature and normal pressure without exposing the substrate to the outside air, a high quality oxide film can be easily formed on the substrate surface with high throughput.

At this time, it is preferable that O ⁻ ions introduced into the chamber are generated from 12CaO · 7Al ₂ O ₃ (claim 8).
Thus, if O ⁻ ions are generated from 12CaO · 7Al ₂ O _3, only O ⁻ ions can be continuously and stably introduced into the chamber. If 12CaO · 7Al ₂ O ₃ is used, handling and disposal of materials can be easily performed, and further cost reduction can be expected.

In this case, it is preferable that O ⁻ ions generated from the 12CaO · 7Al ₂ O ₃ are introduced into the chamber using an inert gas as a carrier gas.
Thus, O inert gas as a carrier gas ^- is introduced ions into the chamber, O ^- to the supply of ions can be easily and smoothly it is also easily controlled reaction at the semiconductor substrate surface it can.

Further, it is preferable that the chamber is evacuated before supplying the inert gas to the chamber.
Thus, if the chamber is evacuated before supplying the inert gas to the chamber, nitrogen or moisture contained in the initial atmosphere in the chamber before introducing the inert gas is effectively removed. Is possible. Thus, for example, then into the chamber O ^- formation of cleaning and oxide film of the semiconductor substrate by ion ^- it is possible ions is prevented reliably from being bonded to the nitrogen and water, O ^- O upon supply ions Can be done very effectively.

Furthermore, it is preferable that the natural oxide film removing substance is anhydrous HF (Claim 11), and the inert gas is preferably argon gas or helium gas (Claim 12).
If the natural oxide film removing material is anhydrous HF, the natural oxide film removal of the semiconductor substrate held in the chamber can be performed very effectively. Further, if the inert gas is argon gas or helium gas, it is possible to reliably prevent the reattachment of pollutants and the re-formation of the natural oxide film after the semiconductor substrate is cleaned or the oxide film is removed.

In the present invention, the semiconductor substrate can be a silicon substrate (claim 13), and in particular, the diameter of the silicon substrate can be 150 mm or more (claim 14).
Thus, the present invention can be used very suitably when an oxide film is formed on the surface of a silicon substrate. In particular, the silicon substrate is O ^- due to the high reactivity with the ion, O after removal of the native oxide film ^- at a high speed silicon substrate surface can form an oxide film by introducing ions into the chamber, significantly improved throughput it can. Further, according to the present invention, the diameter of the silicon substrate can be set to 150 mm or more, and a high-quality oxide film is efficiently formed on the surface of a large-diameter silicon substrate having a diameter of 200 mm, 300 mm, or more, which has recently been particularly demanded. It can be formed stably.

Further, after forming an oxide film on the surface of the semiconductor substrate, it is preferable to perform lamp heating treatment (RTA treatment) for 15 seconds or less at a temperature of 500 ° C. or higher and 1100 ° C. or lower (claim 15).
In the present invention, as described above, an ultrathin oxide film can be formed with high accuracy without increasing the temperature of the silicon substrate. However, the oxide film formed at room temperature may have a large number of pinholes and the like, and it may be difficult to apply to a device because the dielectric breakdown strength is weak for use as a gate oxide film. In addition, defects may be formed at the interface between the silicon and the silicon oxide film, resulting in an interface state, which may adversely affect the device characteristics of the MOS transistor. Therefore, after forming an oxide film with excellent thickness accuracy on the surface of the semiconductor substrate as described above, a lamp heat treatment (RTA treatment; Rapid Thermal Annealing) is performed at a temperature of 500 ° C. to 1100 ° C. for 15 seconds or less. As a result, defects in the oxide film and defects at the interface between silicon and the oxide film can be eliminated, and an extremely high-quality oxide film that can be used for a device can be obtained.

  As described above, according to the present invention, the cleaning of the semiconductor substrate and the removal of the natural oxide film can be performed in the normal pressure state (or a state close to the normal pressure), and then the substrate is not exposed to the outside air at room temperature. Since the oxide film can be formed under normal pressure, a high quality oxide film can be easily formed on the substrate surface with high throughput. Furthermore, since the oxide film forming apparatus for a semiconductor substrate according to the present invention has a simple structure and is compact, the burden on the equipment cost can be greatly reduced and the cost can be reduced.

Hereinafter, although an embodiment is described about the present invention, the present invention is not limited to these.
As a result of intensive studies on a method capable of easily forming a high-quality oxide film at normal temperature and normal pressure on the surface of a semiconductor substrate, the present inventors have determined that 12CaO · 7Al ₂ O ₃ (commonly referred to as alumina cement) Focusing on C12A7), by using this 12CaO · 7Al ₂ O ₃ to generate O ⁻ ions, cleaning of the semiconductor substrate and formation of an oxide film on the substrate surface at normal temperature and pressure are easy and extremely efficient. The present invention has been completed by finding that it is possible to carry out the process.

First, an oxide film forming apparatus for a semiconductor substrate according to the present invention will be described with reference to the drawings, but the present invention is not limited thereto. FIG. 1 is a schematic explanatory view showing an example of an oxide film forming apparatus for a semiconductor substrate according to the present invention.
The semiconductor substrate oxide film forming apparatus 1 of the present invention includes at least a chamber 3 into which a semiconductor substrate 2 is charged, a holding means 4 for holding the semiconductor substrate 2 in the chamber 3, and supplying an inert gas into the chamber 3. supplying an ion supply means 6, a substance for removing a natural oxide film formed on the semiconductor substrate 2 into the chamber 3 ^- and inert gas supply means 5, O into the chamber 3 to ^- O supplying ions Natural oxide film removing means 7 to be provided.

In this oxide film forming apparatus 1, O ^- ion supplying means 6, O ^- is not particularly limited as long as it can be introduced into the chamber to produce ions, for example, using a 12CaO · 7Al ₂ O ₃ Te is active O ^- O to produce ions ^- the ion generating device 8 can be constituted by iontophoresis nozzle 9 made of stainless steel pipe, which is negatively charged.

By using the ion supplying means 6, for example, O ^{- -} Such O O generated from 12CaO · _7Al 2 _{O 3} with an ion generating device 8 ^- ions chamber 3 from the ion introduction nozzle 9 the inert gas as a carrier gas It can be introduced continuously and stably. Further, if the O ⁻ ion supply means 6 generates and supplies O ₂ ⁻ ions from 12CaO · 7Al ₂ O ₃ , the material can be easily handled and discarded, and 12CaO -Since 7Al ₂ O ₃ is an inexpensive material, the cost can be reduced.

In addition, as the O ⁻ ion generator 8 that generates O ⁻ ions from 12CaO · 7Al ₂ O ₃ as described above, for example, as shown in FIG. 2, a tubular tube having one end made of 12CaO · 7Al ₂ O ₃ closed. A C12A7 tube 10 having a shape of: an electrode 11 for applying a negative voltage to the C12A7 tube 10, a collecting electrode 12 disposed at a position away from the C12A7 tube 10, and a heater 13 for heating the C12A7 tube 10. Things can be used. For example, the C12A7 tube 10 and the collecting electrode are heated while the C12A7 tube 10 is heated to about 600 to 800 ° C. by the heater 13 in a state where the inside of the O ⁻ ion generator 8 is decompressed to about 1.3 × 10 ⁻³ Pa. 12, O 2 ⁻ ions can be generated continuously and stably.

  In the present invention, the natural oxide film removing means 7 includes a supply tank 14 for storing the natural oxide film removing substance and a natural oxide film removing process for introducing the natural oxide film removing substance from the supply tank 14 into the chamber 3. A substance introduction nozzle 15 is provided, and the natural oxide film removing means 7 can stably supply a substance capable of removing a natural oxide film such as anhydrous HF into the chamber 3.

  Furthermore, an inert gas such as argon gas can be stably supplied from the inert gas supply means 5. For example, by adjusting a valve 16 installed in the inert gas supply means 5, the chamber 3 The flow rate of the inert gas supplied into the inside can be controlled.

  And in the oxide film forming apparatus 1 of this invention, it is preferable that the exhaust port 17 formed in the chamber 3 is connected to the exhaust means 18. If the exhaust means 18 is installed in the oxide film forming apparatus 1 as described above, the chamber 3 is exhausted to easily and effectively remove nitrogen, moisture, and the like contained in the initial atmosphere in the chamber. Can be removed. As the exhaust means 18, for example, a vacuum pump can be used. In this case, in the present invention, the degree of vacuum required to replace the gas in the chamber 3 is sufficient, and it is not necessary to use a high vacuum.

Next, a method for forming an oxide film on a semiconductor substrate according to the present invention will be described.
In the method for forming an oxide film on a semiconductor substrate of the present invention, after holding the semiconductor substrate in the chamber, while supplying an inert gas to the chamber, the O ⁻ ions are first introduced to clean the semiconductor substrate, and then the natural oxidation is performed. by introducing a film removing material to remove a natural oxide film formed on a semiconductor substrate, then again O ^- is intended to form an oxide film on the surface of the semiconductor substrate by introducing ions.

Hereinafter, the oxide film forming method of the present invention will be described in detail with reference to the oxide film forming apparatus 1 shown in FIG. 1, taking as an example the case of forming an oxide film on a silicon substrate.
First, the silicon substrate 2 is put into the chamber 3 and held and fixed to the holding means 4. Next, the exhaust in the chamber 3 is performed using the exhaust means 18. In the present invention, the exhaust of the chamber 3 is not necessarily performed, but by exhausting the chamber 3 in this manner, nitrogen, moisture, and the like contained in the atmosphere in the chamber can be effectively removed. it ions can be reliably prevented from being oxidized by combining with nitrogen and moisture, also washing and removal of the native oxide film on the semiconductor substrate ^- O upon supply ions ^- O since it is, thereafter chamber Thus, it is possible to reliably prevent the semiconductor substrate from being recontaminated and the natural oxide film from being re-formed.

When exhausting the inside of the chamber 3 in this way, the purpose is to remove nitrogen, moisture, etc. contained in the atmosphere in the chamber, so there is no need to depressurize the chamber to a high vacuum state as in the prior art. For example, the inside of the chamber 3 may be exhausted by the exhaust means 18 so that the inside of the chamber is in a low vacuum state of about 1 × 10 ⁴ Pa or less.

  After evacuating the chamber 3 in this way, argon gas is supplied as an inert gas from the inert gas supply means 5, and the argon gas is filled to normal pressure or close to normal pressure. At this time, helium gas etc. can also be used as an inert gas in this invention.

Then, after filling an argon gas into the chamber 3, while supplying into the chamber 3 by adjusting to the inert gas supply means 5 about the argon gas for example, 3l / min flow rate valve 16, first O ^- ions The silicon substrate 2 is cleaned by introducing it into the chamber 3 from the O ⁻ ion supply means 6. At this time, O ^- by using the ion supplying means 6, O generated from 12CaO · _7Al 2 _{O 3} ^- ions, inert gas (e.g., argon gas) from the ion inlet nozzle 9 as a carrier gas into the chamber 3 It can be introduced continuously and stably, and the reaction on the surface of the semiconductor substrate can be easily controlled.

By introducing O ⁻ ions into the chamber 3 in this way, contaminants such as organic substances are removed from the surface of the silicon substrate 2 by the O ⁻ ions even in a state where the chamber is at normal pressure or close to normal pressure. 2 surfaces can be effectively cleaned. At this time, since the argon gas is continuously supplied into the chamber, the contaminant removed from the surface of the silicon substrate can be discharged from the exhaust port 17, and the contaminant can be prevented from reattaching to the substrate surface. it can. That is, since the O ⁻ ion has a very high reactivity, it can react with a small amount of organic substances or heavy metals existing on the wafer to form an oxide and volatilize it. In this case, since a natural oxide film exists on the wafer surface, an oxide film by O ⁻ ions is not formed at this time.

  Next, while the argon gas is continuously supplied from the inert gas supply means 5 into the chamber 3 at a flow rate of about 3 l / min, a natural oxide film removing substance is introduced from the natural oxide film removal means 7 to the silicon substrate 2. The formed natural oxide film is removed. At this time, the substance supplied from the natural oxide film removing means 7 is not particularly limited as long as it can remove the natural oxide film on the surface of the substrate. For example, the water concentration is reduced as much as possible as the natural oxide film removing substance. By using anhydrous HF, the natural oxide film removal of the silicon substrate can be performed very effectively. In addition, after removing the natural oxide film on the silicon substrate in this manner, the chamber is filled with argon gas, so that the natural oxide film is re-formed on the surface of the silicon substrate, and contaminants adhere to it. Nor.

Then, after washing and removal of the natural oxide film of the silicon substrate as described above, while continuing to supply the argon gas at a flow rate of about 3l / min into the chamber 3, O ^- O of the ion supply means 6 ^- ions Then, an oxide film is formed on the surface of the silicon substrate 2. At this time, O ⁻ ions can be expected to have a low damage process such as an endothermic reaction as compared with O ⁺ ions, and have high reactivity with a silicon substrate and strong oxidizing power. By introducing O 2 ⁻ ions into the chamber 3 at a flow rate of about 5 μl / min, an oxide film having a thickness of about 3 nm can be easily formed on the surface of the silicon substrate 2 even when the inside of the chamber 3 is at normal temperature and normal pressure. And it can be formed in a short time.

Furthermore, in the oxide film forming method of the present invention, after forming the oxide film on the surface of the semiconductor substrate as described above, lamp heat treatment (RTA treatment) is performed at a temperature of 500 ° C. to 1100 ° C. for 15 seconds or less. Is preferred.
When an oxide film is formed on a semiconductor substrate at room temperature, many defects such as pinholes may be formed in the oxide film, and the dielectric breakdown strength is weak for use as a gate oxide film. Can be difficult. In addition, defects may be formed at the interface between the silicon and the silicon oxide film, resulting in an interface state, which may adversely affect the device characteristics of the MOS transistor. Therefore, after forming an oxide film with excellent thickness accuracy on the surface of the semiconductor substrate near the room temperature as described above, the semiconductor substrate is rapidly heated by, for example, lamp heating between 500 ° C. and 1100 ° C. After holding at temperature for a maximum of 15 seconds, the lamp heating power is controlled to cool rapidly to room temperature. By performing the RTA process on the semiconductor substrate in this manner, defects in the oxide film and defects at the interface between the silicon and the oxide film can be effectively eliminated, and an extremely high quality oxide film that can be used for a device is obtained. be able to. Note that such an RTA process is not necessarily performed when the oxide film is formed.

  By forming an oxide film on the surface of the silicon substrate as described above, the semiconductor substrate can be cleaned and the natural oxide film can be removed in a normal pressure state (or a state close to normal pressure) in one chamber. At the same time, the oxide film can be formed at normal temperature and normal pressure without exposing the substrate to the outside air. Therefore, high quality without contamination on the surface of a semiconductor substrate, especially the surface of a large-diameter silicon substrate having a diameter of 150 mm or more, which has recently been increasing in demand, without forming a high vacuum state and heating the substrate as in the past. The oxide film can be easily and stably formed with high throughput.

Furthermore, in the present invention, since the structure of the oxide film forming apparatus is simpler and more compact than the conventional one, the burden on the equipment cost can be greatly reduced, and 12CaO used for the generation of O 2 ⁻ ions. · 7Al ₂ O ₃ is also because it is inexpensive material, it can be made considerably cost.

  In addition, according to the oxide film forming method of the present invention, an oxide film having a very small thickness can be formed as a protective film on the surface of a semiconductor substrate. Therefore, a semiconductor having an extremely stable surface on which a protective oxide film is formed. A substrate can be provided. In such a semiconductor substrate, since the substrate surface is covered with a protective ultra-thin oxide film, the semiconductor substrate surface can be protected from exposure to the outside air when transferred to the next process (for example, thermal oxidation process). In addition, the surface of the semiconductor substrate can be kept clean by preventing re-formation of the natural oxide film.

  As a result, for example, it is possible to prevent the formation of defect levels due to the diffusion of contaminants in the natural oxide film, which has been regarded as a problem in the past, so that the minority carrier generation lifetime (defect level density of the semiconductor substrate is low). A parameter indicating a lack of quality) can be improved, and a semiconductor element having excellent quality can be manufactured at a high yield. Furthermore, such a technique for obtaining a clean ultrathin oxide film can also be used as a method for obtaining a clean interface after oxide film etching for forming contact holes, for example.

  In addition, the oxide film forming method of the present invention can perform various processes other than the thermal oxidation process thereafter by forming the protective oxide film on the surface of the silicon substrate as described above, and the degree of freedom of the process is increased. It also has the advantage that it can be expanded.

  Furthermore, in the present invention, means for applying an RF bias or a DC bias to the semiconductor substrate held in the chamber can be installed in the substrate holding means, for example. Thus, for example, when forming an oxide film on a semiconductor substrate having a trench, a bias can be applied from the back side of the semiconductor substrate, thereby making it easy to form the oxide film with directionality. It becomes possible.

EXAMPLES Hereinafter, although an Example is shown and this invention is demonstrated more concretely, this invention is not limited to these.
As an example, an oxide film having a thickness of 3 nm was formed on the surface of a silicon substrate having a diameter of 200 mm using the oxide film forming apparatus 1 for a semiconductor substrate shown in FIG.
First, after the silicon substrate was put into the chamber 3 and held and fixed to the holding means 4, the inside of the chamber was evacuated by the evacuation means 18, and the inside of the chamber was decompressed to 1 × 10 ⁴ Pa.

Next, argon gas was supplied from the inert gas supply means 5 and filled with the inert gas until the inside of the chamber became normal pressure. Thereafter, the valve 16 is adjusted, and argon gas is supplied from the inert gas supply means to the chamber at a flow rate of 3 l / min, while O ⁻ ions are introduced from the O ⁻ ion supply means 6 into the chamber at a flow rate of 5 μl / min. Then, the silicon substrate was cleaned for 5 minutes, and then anhydrous HF vapor was introduced from the natural oxide film removing means 7 for 5 minutes to remove the natural oxide film formed on the silicon substrate.

  After removing the natural oxide film on the silicon substrate, the argon gas is continuously supplied from the inert gas supply means 5 to the chamber at a flow rate of 3 l / min, while O- ions are again supplied from the O-ion supply means 6 at 5 μl / min. An oxide film having a thickness of 3 nm was formed on the surface of the silicon substrate 2 by introducing into the chamber at a flow rate. When the film thickness uniformity of the oxide film on the entire surface of the substrate was examined with an ellipsometer, it was found that the film had a uniformity of 3 nm ± 0.15 nm. From these results, it was found that an ultrathin oxide film can be formed with extremely uniform by the method according to the present invention.

The quality of the oxide film thus formed on the surface of the silicon substrate was evaluated by the following method. The evaluation method used this time is a method called a copper decoration method. A silicon substrate to be investigated is immersed in methanol, and an electric field of 5 MV / cm is applied between the back surface of the substrate and a copper electrode immersed in methanol to deposit copper on the oxide film of the silicon substrate. This is a method of investigating places that are easily destroyed. An oxide film having a thickness of 3 nm was formed on the surface of the silicon substrate by the method of the present invention and then inspected by the copper decoration method. As a result, 200 pieces / cm ² of black spotted copper precipitates were counted. For the copper decoration method, an oxide film having a thickness of 3 nm is formed on the surface of a silicon substrate manufactured from the same crystal lot for destructive inspection, and then lamp heating treatment (RTA treatment) is performed at 1050 ° C. for 15 seconds in an Ar atmosphere. Then, the oxide film defects were investigated by the copper decoration method as described above. As a result, 10 pieces / cm ² of black spotted copper precipitates were counted. From the above results, it was confirmed that the quality of the oxide film was very excellent.

  The present invention is not limited to the above embodiment. The above embodiment is merely an example, and the present invention has the same configuration as that of the technical idea described in the claims of the present invention, and any device that exhibits the same function and effect is the present invention. It is included in the technical scope of the invention.

  For example, in the above description, it has been described that an oxide film can be formed at normal temperature and normal pressure for the operation of the present invention. However, the present invention does not necessarily have to form an oxide film at normal temperature and normal pressure. Needless to say, the temperature and pressure can be appropriately increased or decreased according to the purpose. Further, it is needless to say that the conditions for the RTA heat treatment by lamp heating can also be adjusted and changed as appropriate according to the quality of the oxide film to be obtained. However, the holding time at a certain holding temperature needs to be adjusted appropriately in order to control the outward diffusion phenomenon of oxygen from the substrate surface. Further, the heat treatment atmosphere is preferably a non-oxidizing atmosphere because if the atmosphere is an oxidizing atmosphere, oxidation proceeds and precise control cannot be performed.

The present invention can be applied to a case where a gate oxide film is formed on a semiconductor substrate. Besides, for example, pad oxidation, LOCOS oxidation, sidewall oxidation, etc. during LSI manufacturing process, or tunnel oxidation during EEPROM manufacturing process, etc. The present invention can be applied to all oxidation processes such as oxidation on a floating gate, and can also be applied as a pretreatment for a deposition process of all SiO ₂ films such as BPSG and TEOS. It can also be used as an oxide film sandwiched between silicon substrates at the time of SOI creation by a bonding method.

It is the structure schematic which shows an example of the oxide film formation apparatus of the semiconductor substrate of this invention. O ^- it is a configuration schematic diagram showing an example of the ion generating device.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Semiconductor substrate oxide film formation apparatus, 2 ... Semiconductor substrate (silicon substrate),
3 ... chamber, 4 ... holding means, 5 ... inert gas supply means,
6 ... O ^- ion supply means, 7 ... Natural oxide film removal means,
8 ... O ^- ion generator, 9 ... Ion introduction nozzle,
10 ... C12A7 tube, 11 ... electrode, 12 ... collecting electrode, 13 ... heater,
14 ... Supply tank, 15 ... Natural oxide removal substance introduction nozzle,
16 ... valve, 17 ... exhaust port, 18 ... exhaust means.

Claims (15)

An apparatus for forming an oxide film on the surface of a semiconductor substrate, comprising at least a chamber into which the semiconductor substrate is placed, a holding means for holding the semiconductor substrate in the chamber, and an inert gas in the chamber supplying an ion supply means, a material for removing a natural oxide film, wherein formed in the semiconductor substrate in a chamber ^- and an inert gas supply means for supplying, O into the chamber a ^- O supplying ions An oxide film forming apparatus for a semiconductor substrate, comprising: a natural oxide film removing unit. The apparatus for forming an oxide film on a semiconductor substrate according to claim 1, wherein the O ^- ion supply means generates the O-ions from 12CaO.7Al ₂ O ₃ and supplies the O ^- ions into the chamber. .   The apparatus for forming an oxide film on a semiconductor substrate according to claim 1 or 2, further comprising exhaust means for exhausting the chamber.   4. The apparatus for forming an oxide film on a semiconductor substrate according to claim 1, wherein the natural oxide film removing means supplies anhydrous HF.   5. The oxide film forming apparatus for a semiconductor substrate according to claim 1, wherein the inert gas supply means supplies argon gas or helium gas.   6. The apparatus for forming an oxide film on a semiconductor substrate according to claim 1, wherein the semiconductor substrate on which the oxide film is formed is a silicon substrate. A method of forming an oxide film on a surface of a semiconductor substrate, wherein after the semiconductor substrate is held in a chamber, the semiconductor substrate is cleaned by first introducing O ⁻ ions while supplying an inert gas to the chamber. and then to introduce the natural oxide film removing material to remove a natural oxide film formed on the semiconductor substrate, then again O ^- that by introducing ions to form an oxide film on a surface of the semiconductor substrate A method for forming an oxide film on a semiconductor substrate. The method for forming an oxide film on a semiconductor substrate according to claim 7, wherein O ⁻ ions introduced into the chamber are generated from 12CaO · 7Al ₂ O ₃ . 9. The method of forming an oxide film on a semiconductor substrate according to claim 8, wherein O ⁻ ions generated from the 12CaO · 7Al ₂ O ₃ are introduced into the chamber using an inert gas as a carrier gas.   10. The method of forming an oxide film on a semiconductor substrate according to claim 7, wherein the chamber is evacuated before an inert gas is supplied to the chamber. 11.   11. The method of forming an oxide film on a semiconductor substrate according to claim 7, wherein the natural oxide film removing material is anhydrous HF.   12. The method of forming an oxide film on a semiconductor substrate according to claim 7, wherein the inert gas is argon gas or helium gas.   13. The method of forming an oxide film on a semiconductor substrate according to claim 7, wherein the semiconductor substrate is a silicon substrate.   14. The method of forming an oxide film on a semiconductor substrate according to claim 13, wherein the diameter of the silicon substrate is 150 mm or more.   15. The lamp heat treatment (RTA treatment) for 15 seconds or less is performed at a temperature of 500 ° C. to 1100 ° C. after forming an oxide film on the surface of the semiconductor substrate. The method for forming an oxide film on a semiconductor substrate according to one item.

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