JPH0982697A - Thermal treatment system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a thermal treatment system which is capable of protecting a silicon wafer against contamination without causing troubles such as rut. SOLUTION: Oxygen gas is flowed through an empty space 9 located between a quartz furnace 4 and a soaking tube 5 outside a quartz inner tube 1 to make metal impurities 12 such as Cu, Fe, and the like which turn to a contaminant source adhere to the surface of the soaking tube 5 in the form of a metal oxide 12 of low vapor pressure so as to prevent metal impurities from penetrating into the quartz inner tube 1 where a silicon wafer 3 is introduced and thermally treated.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heat treatment apparatus, and more particularly to a heat treatment apparatus characterized by preventing contamination of a substrate to be heat treated.

[0002]

2. Description of the Related Art As one of semiconductor manufacturing apparatuses, there is a heat treatment apparatus for executing a process involving heat treatment such as thermal oxidation or annealing. FIG. 5 shows a schematic view of a conventional heat treatment apparatus. In FIG. 5, reference numeral 81 denotes a quartz furnace tube in which a heat-treated substrate such as a silicon wafer is housed and heat-treated. Outside the quartz furnace tube 81, there is a cauterizing tube 82 made of sintered silicon carbide or the like, an aluminum compound tube. Alternatively, a heater 83 made of an iron compound is sequentially provided. Further, a gas inlet port 84 for introducing a process gas into the quartz furnace tube 81.
Also, a gas exhaust port 85 for exhausting the process gas is provided.

In this type of heat treatment apparatus, its constituent members are exposed to a high temperature state and become a pollution source. Therefore, for example, metallic impurities 86 such as Cu or Fe contained in the cauterizing tube 82 and the heater 83 are vapor-phase-diffused into quartz. The adhered metal impurities 86 adhere to the outer wall of the furnace tube 81, and the adhered metal impurities 86 are thermally diffused to the quartz furnace tube 81.
However, there is a problem that it invades the inside of the substrate and contaminates the substrate to be heat treated.

Therefore, in this type of heat treatment apparatus, a cleaning gas 88 such as a halogen gas or a hydrogen halide gas is introduced at the same time as the process gas 87 in order to remove the metal impurities 86 invading the inside of the quartz furnace tube 81. Mouth 84
Is introduced into the quartz furnace tube 81 from the above. In the figure, the region to which the cleaning gas 88 is supplied is shown by hatching.

The cleaning gas 88 has an effect of converting the metal impurities 86 into a halide having a high vapor pressure. Therefore, the metal impurities 86 in the quartz furnace tube 81 become a halide having a high vapor pressure and are exhausted from the gas exhaust port 85, so that the substrate to be heat treated is prevented from being contaminated.

FIG. 6 is a schematic view showing another conventional heat treatment apparatus. The heat treatment apparatus is a quartz furnace tube 81 of the heat treatment apparatus of FIG. 5 and has a configuration obtained by replacing the quartz double furnace tubes 81 _2, flowing process gas 87 in the inner tube of quartz double furnace tubes 81 _2, outer tube By flowing the cleaning gas 88 to the
Contamination of the substrate to be heat treated is prevented. In the figure, the region to which the cleaning gas 88 is supplied is shown by hatching.

However, these conventional heat treatment apparatuses have the following problems. That is, the cleaning gas 88
Since halogen gas, which is a highly corrosive gas, is used as a material, rust occurs in each component of the equipment, and this rust contaminates the heat-treated substrate (reverse contamination problem). . Further, since halogen gas is used, there is a problem in that a facility for removing the halogen gas is required, and the burden becomes large in terms of cost.

Where rust occurs, specifically, a heat treatment member constituting a heat treatment portion such as a flange, a manifold, and a cap for supporting the quartz furnace tube 81 and the quartz double furnace tube 81 ₂ , and a cleaning gas 88 are introduced. A gas supply member that constitutes a gas supply unit such as a valve and a mass flow controller.

Here, in order to prevent rust from being generated in the gas supply member, for example, the water concentration in the gas should be sufficiently controlled,
Furthermore, maintenance for maintaining the apparatus, such as air tightness test of the gas control parts, may be frequently performed. However, in this case, there arises a problem that the burden on the operation and management of the device increases.

Contamination of the substrate to be heat-treated can be prevented by advancing the purification of each component and reducing the metal impurities themselves instead of using the cleaning gas 88, but a sufficient contamination prevention effect can be obtained. Was impossible.

Furthermore, since a metal halide having a high vapor pressure is formed, desorption (scattering) and adhesion (adsorption) from the outer tube to the inner tube occur (not at all). It is not a safe cleaning method or contamination prevention method.

[0012]

[Summary] As described above, in the conventional heat treatment apparatus, the metal impurities in the components exposed to the high temperature state diffuse in the vapor phase,
In order to prevent the substrate to be heat-treated from being contaminated by entering the inside of the quartz furnace tube through thermal diffusion, the metal impurities are converted into halides having a high vapor pressure by a halogen gas and then exhausted. However, there is a problem that the halogen gas causes rusting on each component, and this rusting causes the heat-treated substrate to be contaminated.

Furthermore, since a metal halide having a high vapor pressure is formed, desorption from the outer tube to the inner tube occurs, which is a problem in terms of safety. The present invention has been made in consideration of the above circumstances, and an object of the present invention is to provide a heat treatment apparatus capable of preventing contamination of a substrate to be heat treated.

[0014]

In order to achieve the above-mentioned object, a heat treatment apparatus according to the present invention (claim 1) is a treatment container for accommodating a heat-treated substrate and performing heat treatment, and a metal inside the treatment container. In order to prevent the invasion of impurities, there is provided a means for flowing a cleaning gas, which reacts with the metal impurities and produces a reactant having a vapor pressure lower than the metal impurities, to the outside of the processing container. Characterize.

Further, another heat treatment apparatus according to the present invention (Claim 2) is provided with a processing vessel composed of multiple furnace tubes, and this processing vessel is the innermost tube of the multiple furnace tubes, and the substrate to be heat treated is A first tube to be accommodated and a second tube disposed outside the first tube in the processing container are provided, and metal impurities are prevented from entering the inside of the first tube. In order to prevent the cleaning gas, a cleaning gas that reacts with the metal impurities to generate a reactant having a lower vapor pressure than the metal impurities is used as the second cleaning gas.
It is characterized in that a means for flowing into the pipe is provided.

Another heat treatment apparatus according to the present invention (claim 3) is the heat treatment apparatus (claims 1 and 2) described above.
The cleaning gas is a gas containing oxygen.

Another heat treatment apparatus according to the present invention (claim 4) is characterized in that, in the heat treatment apparatus (claims 1, 2 and 3), the water concentration in the cleaning gas is 100 ppm or less. And

Another heat treatment apparatus according to the present invention (claim 5) is characterized in that, in the heat treatment apparatus (claims 1, 2, 3, 4), the material of the processing container is synthetic quartz. To do.

In the heat treatment apparatus (claim 2), the material of the first tube is preferably synthetic quartz. [Operation] According to the present invention, a cleaning gas that reacts with metal impurities to generate a reaction product (aggregate) having a lower vapor pressure than the metal impurities is flowed to the outside of the processing container or the innermost tube thereof. Therefore, the metal impurities remain attached to the pollution source in the form of reactants having a low vapor pressure. Alternatively, it is separated from the pollution source in the form of particles in the form of a reaction product having a low vapor pressure, and is flown together with the cleaning gas and exhausted. Therefore, since the metal impurities do not enter the inside of the processing container, contamination of the heat-treated substrate can be prevented.

[0020]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments (embodiments) of the present invention will be described below with reference to the drawings. (First Embodiment) FIG. 1 is a schematic diagram showing a schematic configuration of a heat treatment apparatus according to a first embodiment of the present invention.

In the figure, reference numeral 1 denotes an inner quartz tube (processing container), and a wafer board 2 is housed inside the inner quartz tube 1. A plurality of silicon wafers 3 are placed on the wafer board 2.

A quartz furnace tube 4, a burning tube 5, and a heater 6 are sequentially provided outside the inner quartz tube 1. Quartz inner tube 1,
The quartz furnace tube 4 and the cauterizing tube 5 form a heat treatment chamber.
The inner quartz tube 1, the quartz furnace tube 4 and the ablation tube 5 are attached to a flange 7 and are covered with a heat insulating material 8. The ablation tube 5 is made of, for example, sintered silicon carbide, and has a heater 6
Is formed of, for example, metal silicide such as molybdenum silicide, boron nitride, iron compound, or the like.

A gas is introduced into the flange 7 for flowing an oxygen gas (O ₂ gas) as a cleaning gas into a space 9 (a shaded area in the drawing) between the quartz furnace tube 4 and the ablation tube 5. A port 10 and a gas exhaust port 11 for exhausting gas are provided.

The oxygen gas is supplied from, for example, an oxygen cylinder (not shown). Here, the water concentration in the oxygen gas is preferably 100 ppm or less in order to sufficiently exert the effects of the present invention. More preferably, it is 5 ppm or less. This is because water exposed to high temperature dissociates to generate hydrogen having a reducing power with respect to the metal oxide. The gas exhaust port 11 is connected to an exhaust pump (not shown). The gas introduction port 10, the gas exhaust port 11, the oxygen cylinder, the exhaust pump, and the like constitute a means for flowing oxygen gas to the outside of the quartz inner tube 1. Further, the quartz inner tube 1 is provided with a gas introduction port for introducing a process gas and a gas exhaust port for exhausting the process gas, which are not shown.

The main body of the heat treatment apparatus configured as described above is housed in a furnace outer frame provided with an exhaust duct (not shown). In this type of heat treatment apparatus, for example, the cauterization tube 5 provided outside the quartz furnace tube 4 becomes a pollution source.
That is, since the ablation tube 5 is exposed to a high temperature state, metal impurities such as Cu and Fe in the ablation tube 5 are vapor-phase-diffused and thermally diffused to the inside of the quartz inner tube 1 through the quartz furnace tube 4. invade.

Therefore, in the present embodiment, oxygen gas is caused to flow in the space 9 between the quartz furnace tube 4 and the ablation tube 5 to react metal impurities such as Cu and Fe in the ablation tube 5 with oxygen to react with the metal. Change to oxide (aggregate) 12. This kind of metal oxide 12
Since its vapor pressure is low, it remains attached to the surface of the cauterization tube 5 and does not enter the inside of the quartz furnace tube 4.

In addition, from the surface of the ablation tube 5 to the metal oxide 12
Even if peeled off, the peeled metal oxide 12 is exhausted from the gas exhaust port 11 to the outside of the space 9 because it is in the form of particles, so that the metal oxide 12 does not accumulate in the space 9 and remains inside the quartz furnace tube 4. There is no intrusion.

During the heat treatment, oxygen gas is introduced through the gas inlet 10 and exhausted through the gas outlet 11, so that the space 9 is always supplied with a sufficient amount of oxygen gas.
Therefore, the metal impurities in the ablation tube 5 and the oxygen gas can be sufficiently reacted, and the metal impurities can be surely converted into the metal oxide 12.

Thus, according to the present embodiment, it is possible to prevent the metal impurities from entering the inside of the quartz furnace tube 4 by changing the metal impurities into the metal oxide 12 having a low vapor pressure by using oxygen gas. The contamination of the silicon wafer 3 can be prevented.

Further, since oxygen gas is less likely to cause rust in the constituent members than halogen gas, the above-mentioned conventional problems associated with preventing rust are not present. (Second Embodiment) FIG. 2 is a schematic diagram showing a schematic configuration of a heat treatment apparatus according to a second embodiment of the present invention. In addition,
In the following figures, the same reference numerals (including those with different subscripts) as in the above figures indicate the same or corresponding parts, and detailed description thereof will be omitted.

The heat treatment apparatus of this embodiment differs from that of the first embodiment in that a quartz double tube 4 ₂ is used instead of the quartz furnace tube 4. Quartz double tube 4 ₂ outer tube 4
_The oxygen gas (cleaning gas) shown in the first embodiment flows through _2out . Quartz double tube 4 ₂
The inner tube 4 _{2 in} is made of synthetic quartz.
Therefore, the content of impurities in the inner pipe ₄₂ in becomes sufficiently low.

The outer tube 4 _2out of the quartz double tube 4 ₂ may be either normal quartz or synthetic quartz. Further, in the case of using multiple quartz tubes having three or more layers, it is assumed that at least the innermost tube is made of synthetic quartz. When using multiple tubes of triple tubes or more, it is most preferable that the cleaning gas flows in the tube immediately outside the innermost tube. However, at least one of the outer tubes
It is only necessary to flow the cleaning gas, and it is most effective to flow it through all the tubes.

In this embodiment, the same effect as that of the previous embodiment can be obtained. Further, in the present embodiment, the inner tube _{42 in made} of synthetic quartz is used. This is because it was found that Fe contamination can be effectively prevented when synthetic quartz is used, as will be described later. (Third Embodiment) FIG. 3 is a schematic diagram showing a schematic configuration of a heat treatment apparatus according to a third embodiment of the present invention.

The heat treatment apparatus of this embodiment differs from that of the first embodiment in that the gas inlet 1 is provided under the heat insulating material 8.
Oxygen gas is supplied to the heat insulating material 8 by providing a flange 7a having 0 formed therein.

Since the heat insulating material 8 is formed of a foam material, the surroundings of the ablation tube 5 and the heater 6 as well as the heat insulating material 8 are in an oxygen atmosphere. The oxygen gas introduced from the gas inlet 10 is exhausted from the exhaust duct of the frame outside the furnace body. In the figure, the region to which oxygen gas is supplied is shown by hatching.

According to this embodiment, the heat insulating material 8 and the burning tube 5 are provided.
Further, since oxygen gas is supplied to the heater 6, it is possible to prevent contamination by metal impurities contained in these. The inventors of the present invention performed hydrogen combustion oxidation on the surface of a silicon wafer in the heat treatment apparatus (heat treatment diffusion furnace) of the conventional and the present invention,
Form an oxide film with a thickness of 300 nm on a silicon wafer,
Wet analysis of the amount of metal impurities in each oxide film (VPD
Method). The quartz furnace tube is made of ordinary quartz.

As a result, in the conventional heat treatment diffusion furnace, the surface concentration of Cu was detected at about 1 × 10 ¹¹ atoms / cm ² , whereas in the heat treatment diffusion furnace of the present invention, the surface concentration of Cu was below the detection limit (1 × 10 ⁹ atoms / cm ² or less)
Met.

Further, the low electric field leakage current of the tunnel oxide film which causes the excessive erase mode error of the NOR type flash memory was examined by using the heat treatment diffusion furnaces of the prior art and the present invention. FIG. 4 is a characteristic diagram showing the relationship between the gate voltage V _G and the leak current I as the result. As shown in FIG. 4, when the conventional heat treatment diffusion furnace is used, a low electric field leakage current is generated in the tunnel oxide film when the gate voltage V _G is in the range of −6 to −10 V, unlike the case where the heat treatment diffusion furnace of the present invention is used. You can see that

Further, hydrogen annealing was performed on the silicon wafers in the conventional heat treatment apparatus (hydrogen annealing furnace) and the amount of metal impurities on the surface of each silicon wafer was examined by wet analysis (WAS method). . The quartz furnace tube is made of ordinary quartz.

As a result, in the conventional hydrogen annealing furnace, Cu
The surface concentration of Cu was detected at about 5 × 10 ¹⁰ atoms / cm ² , whereas the surface concentration of Cu was below the detection limit (1 × 10 ⁹ atoms / cm ² or less) in the heat treatment diffusion furnace of the present invention.

Next, using a quartz furnace tube made of synthetic quartz, heat treatment apparatuses (hydrogen annealing furnace) of the conventional and the present invention are similarly used.
Hydrogen annealing is applied to each silicon wafer in the
The amount of metal impurities on the surface of each silicon wafer was examined by wet analysis (WAS method).

As a result, not only the surface concentration of Cu but also F
Similar results were obtained for the surface concentration of e. That is, in the conventional case, the surface concentration of Cu is 5 × 10 ¹⁰ atom.
Although about s / cm ² was detected, in the case of the present invention, C
The surface concentration of u and Fe is below the detection limit (1 × 10 ⁹ a
(Toms / cm ² or less).

The present invention is not limited to the above embodiment. For example, in the above embodiment, as the heat treatment apparatus, it is desired to explain one for forming an oxide film or annealing, but the present invention is not limited to this, and the present invention has other applications, for example, LP
(Low Pressure) -Applicable to a heat treatment apparatus such as deposition film formation represented by CVD.

The cleaning gas is not limited to oxygen gas, and any gas can be used as long as it is a gas that reacts with metal impurities to produce a reaction product having a vapor pressure lower than that of the metal impurities.
Other gas may be used. In addition, various modifications can be made without departing from the scope of the present invention.

[0045]

As described above in detail, according to the present invention, a cleaning gas such as oxygen gas is used to convert metal impurities into metal oxides having a low vapor pressure, so that the metal impurities penetrate into the processing container. Since this can be prevented, contamination of the heat-treated substrate can be prevented.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing a schematic configuration of a heat treatment apparatus according to a first embodiment of the present invention.

FIG. 2 is a schematic diagram showing a schematic configuration of a heat treatment apparatus according to a second embodiment of the present invention.

FIG. 3 is a schematic diagram showing a schematic configuration of a heat treatment apparatus according to a third embodiment of the present invention.

FIG. 4 is a characteristic diagram showing a relationship between a gate voltage and a leak current for explaining the effect of the present invention.

FIG. 5 is a schematic diagram showing a schematic configuration of a conventional heat treatment apparatus.

FIG. 6 is a schematic diagram showing a schematic configuration of another conventional heat treatment apparatus.

[Explanation of symbols]

1 ... quartz inner tube (processing container) 2 ... wafer board 3 ... silicon wafer (to be thermally substrate) 4 ... inner tube 4 _2out ... quartz dual quartz furnace tube 4 ₂ ... a quartz double tube 4 _2in ... quartz double tube Outer tube 5 ... Burning tube 6 ... Heater 7 ... Flange 8 ... Insulating material 9 ... Space 10 ... Gas inlet 11 ... Gas exhaust 12 ... Metal oxide

Claims (5)

[Claims] 1. A processing container for accommodating a substrate to be heat-treated and performing a heat treatment, and a vapor pressure higher than that of the metal impurities by reacting with the metal impurities in order to prevent metal impurities from entering the inside of the processing container. Cleaning gas, which produces a low reactant
A heat treatment apparatus comprising: a means for flowing out of the processing container. 2. A processing vessel comprising multiple furnace tubes, the processing vessel being the innermost tube of the multiple furnace tubes and containing a substrate to be heat treated, and a first vessel of the first tube. A second pipe disposed outside, and the processing container includes
In order to prevent the metal impurities from entering the inside of the first pipe, a cleaning gas that reacts with the metal impurities to generate a reactant having a vapor pressure lower than that of the metal impurities is supplied to the second pipe. A heat treatment apparatus provided with a flow means. 3. The heat treatment apparatus according to claim 1, wherein the cleaning gas is a gas containing oxygen. 4. The water concentration in the cleaning gas is 100.
The heat treatment apparatus according to any one of claims 1 to 3, which has a ppm order or less. 5. The heat treatment apparatus according to claim 1, wherein the processing container is made of synthetic quartz.