JP3272823B2 - Dry cleaning method for semiconductor device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement in a dry cleaning method applied to a semiconductor device manufacturing process.

[0002]

2. Description of the Related Art In recent years, semiconductor integrated circuits have rapidly become highly integrated, and in order to improve the reliability thereof, contaminants such as heavy metals and light metals adsorbed on the surface of a semiconductor device are removed to improve electric characteristics. It is desired.

That is, when a contaminant such as a heavy metal is introduced into a semiconductor substrate (silicon substrate) during a manufacturing process of a semiconductor device, a trap center of electrons or holes is formed or a pn junction leak is caused. Or the electrical characteristics of the semiconductor element may be degraded. For example, in a DRAM, F
When heavy metals such as e, Cu, Ni, and Au are introduced, the lifetime of the MOS transistor formed on the substrate surface is reduced, and the memory retention time is shortened. In addition, it has been reported that the introduction of the heavy metal into the gate oxide film causes deterioration of electric characteristics such as dielectric strength and leakage current of the gate oxide film and an increase in defect density.

In order to increase the speed of a semiconductor device, it is necessary to reduce the capacitance between wirings, increase the insulating property of the interlayer insulating film, and reduce the amount of contamination on the surface of the underlying silicon substrate. .

Conventionally, as a method of cleaning a solid surface used in a semiconductor device manufacturing process, a wet cleaning method and a dry cleaning method are known. However, in the wet cleaning method, at present, contaminated metal at a level of 10 ⁹ to 10 ¹² atoms / cm ² is adsorbed on the wafer due to the purity of the cleaning liquid (chemical solution) and the reverse adsorption of the contaminated metal to the semiconductor substrate (silicon wafer). Problem. In addition, as a dry cleaning method, a halogen gas such as fluorine gas and chlorine gas is used in a vacuum.
A gas type using a gas containing a BR element, a silicon-based gas, or the like, or a radical thereof as a reactive species for a contaminant metal is known. However, this method has a problem that the surface of the substrate is roughened by etching the silicon substrate together with the removal of the contaminant metal.

As a technique for forming a clean oxide film (eg, a gate oxide film) on the surface of a silicon substrate, hydrogen chloride (HCl) gas or trichloroethane (TC) has conventionally been used.
A) An additional thermal oxidation method (hydrochloric acid oxidation method) is known.
It is known that this hydrochloric acid oxidation method has an effect of gettering a contaminant metal on a solid surface into a gas phase. However, this method includes a method in which the contaminant metal on the silicon substrate surface is removed in the gas phase due to the conditions of thermal oxidation, and a method in which the contaminant metal diffuses into the silicon substrate. It is difficult.

That is, when the silicon substrate 31 is thermally oxidized in an oxidizing atmosphere containing hydrogen chloride (HCl) gas as shown in FIG.
Reacts with HCl and is gettered in the gas phase in the form of a metal chloride. During this gettering, the contaminated metal 32 on the surface of the substrate 31 diffuses into the substrate 31 as shown in FIG. In addition, since heat treatment is performed at a high temperature in an oxidizing atmosphere, a part of the contaminant metal 32 is not removed and is taken in or diffused into the oxide film 33 formed as a metal oxide. There is a problem. The diffusion of the contaminated metal into the silicon substrate becomes more remarkable as the heating temperature during the oxidation with hydrochloric acid increases.

Further, the hydrochloric acid oxidation method involves a problem that the surface shape of the semiconductor substrate is changed since an oxide film is formed. On the other hand, when an insulating film such as an oxide film or a nitride film formed by a vapor deposition method such as a CVD method is etched by reactive ion etching (RIE), R
Contaminated metals in the IE chamber adhere to those films,
It is taken into the film. Most of the contaminant metal adhering to the surface of the insulating film can be removed by wet cleaning. However, the surface of the insulating film cannot be sufficiently cleaned due to the problems of purity and reverse adsorption of a chemical solution for removing the contaminant metal. Further, there is a problem that impurities taken into the insulating film cannot be removed by wet cleaning without etching.

[0009]

SUMMARY OF THE INVENTION An object of the present invention is to make it possible to easily and effectively getter in a gas phase without diffusing a contaminant metal generated during an element forming process into a semiconductor substrate. An object of the present invention is to provide a dry cleaning method for a semiconductor device.

Another object of the present invention is to provide a dry cleaning method for a semiconductor device capable of easily and effectively gettering a contaminated light metal (particularly Al) generated during an element forming step into a gas phase. What you want to do.

[0011]

According to the present invention, there is provided a dry cleaning method for a semiconductor device, comprising: a vertical external reactor having a gas inlet at a lower portion; a gas introducing hole disposed at an upper portion of the reactor; A process comprising: a vertical internal reactor having an exhaust port formed at a lower portion thereof; a holder disposed in the vertical reactor; and a heater disposed around a side surface of the vertical external reactor. Using a device, a semiconductor substrate or a semiconductor substrate on which various films are formed on the surface is held and installed in a holder arranged in the internal reaction furnace so that most of the front and back surfaces of the semiconductor substrate are exposed. A cleaning method carried out immediately before the step of oxidizing or diffusing, wherein a gas containing a halogen or a halide is supplied from an inlet at the lower part of the vertical external reactor to the external reactor and the vertical internal reactor. Introduced into the space with the reactor and raised At the same time, the gas in the ascending process is heated by the heater, and the heated gas is exhausted from the gas introduction hole at the upper portion of the vertical internal reactor through the inside thereof through the exhaust port at the lower portion. front and back surfaces is the retained gas containing a halogen or halide is heated to a temperature of 400 to 600 ° C. in the semiconductor substrate is contacted to exposed heat treated holder in the furnace, the table of the semiconductor substrate It is characterized in that aluminum on the back surface is removed .

The semiconductor substrate has a form shown in FIGS. 1 to 5, for example. That is, in FIG. 1, 21 is a silicon substrate, and 23 is a contaminant metal attached to the surface of the substrate 21.

In FIG. 2, 21 is a silicon substrate, 25 is a natural oxide film formed on the surface of the substrate 21, and 23 is a contaminant metal adhered to the surface of the natural oxide film or taken into the inside. .

In FIG. 3, 21 is a silicon substrate, 22 is a thermal oxide film formed on the surface of the substrate 21, 26 is a CVD SiO ₂ film deposited on the surface of the thermal oxide film 22, and 27 is a CVD SiO ₂ film 26 A BPSG film deposited on the surface,
28 is a contact hole opened by, for example, RIE from the BPSG film 27 to the thermal oxide film 22;
Reference numeral 23 denotes a contaminant metal attached to the inner surface of the contact hole 28.

In FIG. 4, reference numeral 21 denotes a silicon substrate, and reference numeral 22 denotes a thermal oxide film formed on the surface of the substrate 21. In FIG. 5, 21 is a silicon substrate, 22 is a thermal oxide film formed on the surface of the substrate 21, and 24 is a silicon nitride film deposited on the thermal oxide film 22.

For example, a photoresist or the like is applied on the thermal oxide film 22 of FIG. 4 and the silicon nitride film 24 of FIG. 5 for the etching step, and the contaminant metal 23 is deposited during the resist processing step. It adheres to the surface of the film or penetrates into it.

As the halogen, for example, Cl ₂ or the like can be used, and as the halogen compound, for example, HCl, HBr, CCl ₄ , C ₂ HCl ₃ or the like can be used.

As the non-oxidizing gas for forming the non-oxidizing atmosphere, for example, nitrogen gas or argon,
An inert gas such as helium can be used. The concentration of the halogen or halide contained in the non-oxidizing atmosphere is desirably 3% or more.

The heat treatment temperature may be set to a temperature higher than the temperature at which the contaminant metal reacts with the halogen. The reason for limiting the temperature during the heat treatment is that if the semiconductor substrate in the state of FIGS. 1 to 3 is subjected to a heat treatment at a temperature exceeding 600 ° C. in a non-oxidizing atmosphere containing a halogen or a halide, as shown in FIG.
This is because the semiconductor substrate (silicon substrate) is etched by, for example, chlorine gas as shown in FIG. A more preferred heat treatment temperature is a temperature not lower than the temperature at which the contaminant metal reacts with the halogen, and
C. or lower, more preferably 500 C. or lower.

For carrying out the dry cleaning method according to the present invention, for example, a vertical processing apparatus shown in FIG. 8 is used. For reference, the horizontal processing apparatus shown in FIG.
This will be described below. That is, the processing apparatus shown in FIG. 7 is formed with a horizontal reaction tube made of, for example, quartz in which an introduction pipe 1 for introducing a non-oxidizing gas and HCl gas is formed at one end and a cap 3 having an exhaust pipe 2 is attached at the other end. Furnace 4
And a heater 5 arranged around the reaction furnace 4. Reference numeral 6 in the drawing denotes a quartz boat on which a large number of silicon wafers 7 are leaned, and the quartz boat 6
Is carried into the reactor 3 from the side where the cap 3 is attached.

The processing apparatus shown in FIG. 8 has a vertical external reaction furnace 13 made of quartz having an inlet 11 for introducing a non-oxidizing gas and HCl gas at a lower part, a gas introducing hole 12 at an upper part, and a gas introducing hole 12 at a lower part. A vertical internal reactor 15 made of quartz having an exhaust port 14 formed therein, and the vertical external reactor 13
And a heater 16 arranged around the side of the heater. In the drawing, reference numeral 17 denotes a wafer holder which is carried into the vertical internal reaction furnace 15 and in which a large number of silicon wafers 18 are stored in a horizontal state in the vertical direction.

The inside of the reaction furnace shown in FIGS. 7 and 8 may be a reduced pressure atmosphere or a pressurized atmosphere. Another dry cleaning method for a semiconductor device according to the present invention is the dry cleaning method for a semiconductor device for reducing contaminating light metal adsorbed on a semiconductor substrate or a semiconductor substrate having various films formed on a surface thereof. In a gas atmosphere containing halogen or halide at a temperature of 400 ° C. or more and 700 ° C. or less.

As the light metal, for example, Al, Ca,
Na, K and the like can be mentioned. As the halogen, for example, Cl ₂ or the like can be used. As the halogen compound, for example, HCl, HBr, CCl ₄ , C ₂
HCl ₃ or the like can be used.

It is desirable that the concentration of the halogen or the halide contained in the oxidizing atmosphere is 3% or more. The reason why the heat treatment temperature is limited is that if the temperature deviates from the temperature range (400 ° C. or more and 700 ° C. or less), light metals, particularly Al, cannot be effectively removed.

The above-mentioned dry cleaning method according to the present invention is carried out immediately before a step such as an oxidation treatment, a diffusion treatment or a film deposition treatment. In particular, it is preferable that the dry cleaning method of the present invention employs an in-line process in which the next step is continuously performed without exposure to the atmosphere after being performed immediately before the above-described step.

[0026]

The present inventors investigated the thermal behavior of Fe, a typical contaminant element adsorbed on the surface of a Si substrate, in a HCl oxidizing atmosphere at normal pressure in a range from room temperature (RT) to 1000 ° C. Was. As a result, a relationship between the amount of Fe in the natural oxide film or the thermal oxide film and the amount of Fe diffused in the Si substrate at each processing temperature as shown in FIG. 17 was obtained. The following facts have been clarified from FIG. In the following description, reference is made to FIGS. 18A to 18D showing the thermal behavior of Fe when heat treatment is performed at different temperatures in the HCl oxidizing atmosphere at normal pressure.

(1) As shown in FIG. 17, Fe on the native oxide film is hardly removed when heat-treated in a temperature range (I) of not less than RT and less than 200 ° C. This state is shown in FIG. That is, Fe23 remains on the native oxide film 25 of the substrate 21.

(2) As shown in FIG.
When heat-treated in a temperature range (II) lower than 400 ° C., Fe
Begins to be removed in the gas phase, but mostly remains on the Si substrate surface. 400 ° C to 600 ° C temperature range (II
When the heat treatment is performed in step I), Fe on the substrate surface is efficiently removed in the gas phase. This state is shown in FIG. That is, Fe23 on the natural oxide film 25 reacts with the halide to become a metal chloride and is removed in the gas phase.
However, when heat treatment is performed at a temperature exceeding 550 ° C., Fe on the substrate surface starts to diffuse into the substrate. Therefore, 55
The heat treatment is preferably performed at a temperature of 0 ° C. or less. In addition, 3
Even at a temperature of 00 ° C. or more, a certain amount of Fe and Ni can be removed.

(3) As shown in FIG. 17, when the heat treatment is performed in a temperature range (IV) higher than 600 ° C. and lower than 800 ° C.,
Since the treatment is performed in an oxidizing atmosphere, Fe on the surface contaminated by oxidation of the Si substrate starts to diffuse into the oxide film partially formed. This state is shown in FIG. Note that reference numeral 22 in the drawing denotes an oxide film generated by oxidation of the Si substrate 21. Therefore, in the temperature range (IV), the contaminated surface Fe is removed in the gas phase, the Fe is diffused into the oxide film and left in the film, and the Fe is further diffused into the Si substrate. Coexist.

(4) As shown in FIG.
When heat treatment is performed in a temperature range (V) lower than 1000 ° C., most of the Fe diffuses into the Si substrate. This state is shown in FIG.
(D) of FIG. The Fe once diffused into the oxide film is sucked out of the film due to the large diffusion coefficient of Fe in the oxide film, unlike the case where the heat treatment is performed in the temperature range of 600 ° C. or more and less than 800 ° C. Does not remain. However, the reason why Fe cannot be removed to the detection limit is that the Si substrate is treated in an oxidizing atmosphere, so that part of Fe is taken in as an oxide (eg, Fe ₂ O ₃ ) in an oxide film. Because.

For the reasons explained in the above (1) to (4), S
In order to effectively remove Fe adsorbed on the substrate surface without diffusing Fe into the i-substrate, the temperature is higher than the temperature at which Fe reacts with the halide in the normal pressure process, for example, 4
It can be seen that it is necessary to perform the heat treatment in a temperature range from 00 ° C. to 600 ° C. Further, from the viewpoint of suppressing the contamination metal from becoming a metal oxide and being taken into an oxide film formed on the substrate surface, it is understood that the gas to which HCl is added needs to be a non-oxidizing gas. . Therefore, the present invention includes a step of heat-treating the semiconductor substrate in a non-oxidizing atmosphere containing halogen or halide at a temperature of 600 ° C. or less, so that the semiconductor substrate is more effectively adsorbed on the substrate surface than the conventional hydrochloric acid oxidation method. It is possible to remove the contaminated elements.

By subjecting the semiconductor substrate or the semiconductor substrate having various films formed on its surface to a heat treatment in a non-oxidizing atmosphere containing a halogen or a halide (eg, HCl), for example, as shown in FIG. The contaminant metal 23 attached to the surface of the thermal oxide film 22 on the silicon substrate 21 easily reacts with HCl in the heated atmosphere, and the gaseous phase in a state of a metal chloride having a significantly higher vapor pressure than the metal. Gettered inside. Further, the contaminant metal taken into the film is diffused to the surface of the film by the heat treatment, and is gettered in the gas phase by the same mechanism as described above. In addition, by performing the treatment in a non-oxidizing atmosphere, the amount of contaminant metals taken into the oxide film as oxide without being gettered in the gas phase can be significantly reduced.

When the dry cleaning treatment according to the present invention is performed in a state where the surface of the semiconductor substrate or the natural oxide film is exposed in the gas phase, the heat treatment is performed at a temperature of 600 ° C. or less, for example, as shown in FIG. As shown in FIG. 1, the contaminated metal 23 on the surface of the silicon substrate 21 can be gettered in the gas phase in the state of a metal chloride while suppressing the occurrence of etch pits on the surface of the silicon substrate 21. However, as shown in FIG.
3. The contaminated metal 23 attached to the inner surface of the contact hole 28 shown in FIG. 3 is also gettered in the gas phase by the same process. Furthermore, for example, by performing pre-treatment of gate oxidation on the surface of the semiconductor substrate and continuously performing gate oxidation without exposure to the air, contaminant metals on the surface of the semiconductor substrate can be removed at a low temperature. It is possible to manufacture a semiconductor device having good characteristics with less contamination on a semiconductor substrate and an oxide film as compared with a semiconductor device formed by a conventional hydrochloric acid oxidation method, because external recontamination accompanying the above can be prevented. Can be.

Therefore, since the method of the present invention is of a dry type, it is possible to solve the problems of chemical cleaning such as purity and reverse adsorption, which are problems in wet cleaning, and to prevent the contamination metal taken in the film from being etched. Can be removed.
In addition, since the treatment is performed in a non-oxidizing atmosphere, a change in the shape of the semiconductor substrate due to oxidation can be suppressed.

Further, according to another dry cleaning method according to the present invention, when reducing contaminating light metals adsorbed on a semiconductor substrate or a semiconductor substrate having various films formed on its surface, the semiconductor substrate is treated with a halogen or halide. By performing heat treatment at a specific temperature of 400 ° C. or more and 600 ° C. or less in a gas atmosphere containing, the contaminated light metal (particularly, Al) can be effectively gettered in the gas phase.
Also, for example, if the gate oxidation is performed as a pre-treatment on the surface of the semiconductor substrate and the gate oxidation is continuously performed without being exposed to the air, the semiconductor substrate and the oxide film can be compared with the semiconductor device formed by the conventional hydrochloric acid oxidation method. A semiconductor device having good characteristics with less Al contamination can be manufactured.

According to the present invention as described above, heavy metals such as Fe, can reduce the light metal contamination level of Al or the like, in particular 10 ¹² atoms / cm ² order or less, more 1
It can be suppressed to the order of 0 ¹⁰ atoms / cm ² or less.

[0037]

Embodiments of the present invention will be described below in detail with reference to the drawings. Example 1 and Comparative Examples 1 to 3 A heat treatment at 550 ° C. for 1 hour in a N ₂ atmosphere (Comparative Example 1) was performed on a silicon substrate on which a thick thermal oxide film forcibly contaminated with Fe was formed (Comparative Example 1). In an atmosphere, at the same temperature, simultaneous oxidation treatment (Comparative Example 2), in an oxygen atmosphere containing HCl, at the same temperature, in a simultaneous hydrochloric acid oxidation treatment (Comparative Example 3), and in an N ₂ atmosphere containing 10% HCl, the same. Temperature and simultaneous heat treatment (Example 1) were performed.

With respect to the silicon substrates after the treatments of Comparative Examples 1 to 3 and Example 1, the thermal oxide film on the surface was dissolved with a dilute hydrofluoric acid solution, and the amount of Fe contained in the solution was analyzed by atomic absorption analysis. FIG. 9 shows the result.

As is clear from FIG. 9, Fe is not removed at all by heat treatment in N ₂ atmosphere (Comparative Example 1) or ordinary dry oxidation (Comparative Example 2). This is because the vapor pressure of Fe alone or the vapor pressure of Fe oxide is low,
Cannot be removed from the oxide film into the gas phase. On the other hand, in the hydrochloric acid oxidation method of Comparative Example 3, Fe is gettered in the gas phase, and the amount of Fe incorporated in the film is reduced as compared with the contamination level. It can be seen that the amount of Fe taken in can be reduced.
This is because, in the hydrochloric acid oxidation method, since the silicon substrate is treated at a high temperature in an oxidizing atmosphere, a part of Fe compulsorily contaminated on the surface of the thermal oxide film is not removed, and the Fe oxide remains in the oxide film. It is due to being taken in. In contrast, in the present invention, since the treatment is performed in a non-oxidizing atmosphere, the formation of Fe oxides is suppressed, only Fe chloride having a high vapor pressure can be generated, and gettering can be easily performed in the gas phase. It is considered something.

Example 2 and Comparative Example 4 A silicon substrate having a thick thermal oxide film forcibly contaminated with Fe formed on a surface thereof was placed in an oxygen atmosphere containing HCl in an oxygen atmosphere.
In a temperature range of 0 ° C. or more and 600 ° C. or less, a 1-hour hydrochloric acid oxidation treatment (Comparative Example 4) and a simultaneous heat treatment (Example 2) in an N ₂ atmosphere containing 10% HCl in the same temperature range were performed. did.

With respect to the silicon substrates treated in Example 2 and Comparative Example 4, the thermal oxide film on the surface was dissolved in a dilute hydrofluoric acid solution, and the amount of Fe contained in the solutions was analyzed by atomic absorption analysis. The results are shown in FIG. 10 as a relationship between temperature and Fe amount.

As is clear from FIG. 10, in the hydrochloric acid oxidation method of Comparative Example 4, Fe was gettered in the gas phase, and the amount of Fe incorporated in the film was reduced as compared with the contamination level. In the second embodiment, furthermore, Fe incorporated in the thermal oxide film
It can be seen that the amount can be reduced on the high temperature side. This indicates that, as the vapor pressure of the metal oxide generally increases as the temperature increases, the treatment of the present invention increases the Fe removing effect. However, in this case, since the thermal oxide film acts as a protective film, the silicon substrate may be H
It is prevented from being etched by Cl (Cl ₂ ). In contrast, in the hydrochloric acid oxidation method of Comparative Example 4, at a temperature of 400 ° C. or more, a part of Fe becomes an oxide in the oxide film and cannot be removed.

Example 3 A silicon substrate having a thick thermal oxide film forcibly contaminated with Ni formed on a surface thereof in an N ₂ atmosphere containing 10% HCl in a temperature range of 100 ° C. to 600 ° C. Time heat treatment was applied.

With respect to the silicon substrate after the treatment in Example 3, the thermal oxide film on the surface was dissolved in a dilute hydrofluoric acid solution, and the amount of Ni contained in the solution was analyzed by atomic absorption analysis. The results are shown in FIG. 11 as a relationship between temperature and Ni amount.

As is apparent from FIG. 11, in the third embodiment, the amount of Ni taken in the thermal oxide film can be reduced to the detection limit on the high temperature side. Example 4 A silicon substrate having a natural oxide film forcibly contaminated with Fe formed on a surface thereof in an N ₂ atmosphere containing 10% HCl was used.
Heat treatment was performed for 1 hour in a temperature range of 300 to 500 ° C. The natural oxide film is a thin oxide film formed on a silicon substrate surface by a wet cleaning method or a thin oxide film of 50 Å or less formed gradually on a silicon substrate treated with hydrofluoric acid with time. It is.

With respect to the silicon substrate after the treatment in Example 4, the natural oxide film on the surface was dissolved with a dilute hydrofluoric acid solution, and the amount of Fe contained in the solution was analyzed by atomic absorption analysis. Also,
The amount of Fe diffused into the Si substrate was measured. The results are shown in FIG. 12 as a relationship between temperature and Fe amount.

As is apparent from FIG. 12, in the fourth embodiment, since the treatment is performed at a low temperature, Fe diffused in the silicon substrate.
It can be seen that the amount of Fe in the natural oxide film can be reduced to the detection limit in the gas phase.

Example 5 A silicon substrate having a surface contaminated with Fe was subjected to dry cleaning at 400 ° C. for 1 hour in an N ₂ atmosphere containing 10% HCl, and then oxygen containing HCl was exposed without being exposed to the air. A gate oxide film was formed on the surface of the substrate by performing hydrochloric acid oxidation treatment at 800 ° C. for 1 hour in an atmosphere.

Comparative Example 5 A silicon oxide substrate whose surface was contaminated with Fe was directly subjected to a hydrochloric acid oxidation treatment at 800 ° C. for 1 hour in an oxygen atmosphere containing HCl to form a gate oxide film on the substrate surface.

The gate oxide film formed by the treatments of Example 5 and Comparative Example 5 and the surface layer of the silicon substrate under the gate oxide film were dissolved in a dilute hydrofluoric acid solution, and the Fe content in the solution was determined by atom. Absorbance analysis was performed. Further, the amount of Fe diffused into the Si substrate was measured. The result is shown in FIG.

As is apparent from FIG. 13, in the fifth embodiment, the contamination to the silicon substrate and the gate oxide film can be suppressed, and a good result can be obtained as compared with the comparative example 5 in which the gate oxide film is formed by directly performing the hydrochloric acid oxidation method. A MOS semiconductor device having characteristics can be manufactured.

Embodiment 6 As shown in FIG. 5, a contact hole 28 is opened by RIE over the thermal oxide film 22, the CVD SiO ₂ film 26 and the BPSG film 27 on the silicon substrate 21, and then contains 10% HCl. Heat treatment was performed at 400 ° C. for 1 hour in an N ₂ atmosphere.

It was confirmed that the treatment of Example 6 successfully removed contaminant metal adhered to the inner surface of the contact hole during the RIE. Although silicon substrate surface exposed in the contact hole bottom is when treated with conventional hydrochloric acid oxidation method is changed the shape of the contact hole to be oxidized, the method of the present embodiment 6 is made in an atmosphere of N ₂ Therefore, oxidation did not progress, and the shape change of the contact hole could be prevented.

Example 7 A silicon substrate on which a natural oxide film adsorbing Al as a contaminating light metal was formed was placed in a gas atmosphere containing 10% HCl.
Heat treatment was performed for 1 hour in a temperature range of 00 to 1000 ° C. The natural oxide film is formed by the RCA cleaning SC1 process.

With respect to the silicon substrate after the treatment in Example 7, the oxide film on the surface was dissolved with a dilute hydrofluoric acid solution, and the amount of Al contained in the solution was analyzed by atomic absorption analysis. The results are shown in FIG. 14 as a relationship between temperature and Al amount.

As is apparent from FIG. 14, Al is hardly removed by the treatment at a temperature lower than 400 ° C. or higher than 700 ° C. On the other hand, 400 ° C or higher, 600 ° C or lower
In particular, by performing the treatment at a temperature lower than 600 ° C.,
Can be effectively removed. This is because the heat treatment in the above temperature range suppresses the formation of Al oxide,
This is because the formation of 1 chloride can be promoted and Al can be favorably gettered in the gas phase.

Examples 8 and 9 and Comparative Example 6 A silicon substrate on which a natural oxide film adsorbing Al as a contaminated light metal was formed was placed in an oxygen atmosphere containing 10% HCl.
Heat treatment at 00 ° C. for 1 hour (Example 8) in an oxygen atmosphere containing 10% HCl, 800 ° C., heat treatment for 1 hour (Comparative Example 6), and 500 ° C. in an oxygen atmosphere containing 10% HCl.
After the heat treatment at 1 ° C. for 1 hour, the silicon substrate was subjected to a heat treatment at 800 ° C. for 1 hour (Example 9) without being exposed to the air.

With respect to the silicon substrates treated in Examples 8 and 9 and Comparative Example 6, the oxide film on the surface was dissolved with a dilute hydrofluoric acid solution, and the amount of Al contained in the solutions was analyzed by atomic absorption analysis. The result is shown in FIG.

As is apparent from FIG. 15, in Comparative Example 6 in which the treatment was performed at a high temperature of 800 ° C., Al was hardly getterable in the gas phase. In contrast, it can be seen that in Example 8 in which the treatment is performed at a low temperature of 500 ° C., Al can be effectively removed. In the ninth embodiment, after the treatment at the low temperature of 500 ° C., the oxidation treatment is continuously performed at a high temperature of 800 ° C. without being exposed to the air, a clean oxide film from which Al has been removed is formed on the surface of the silicon substrate. I understand. Therefore, it is possible to manufacture a good semiconductor device with less oxide film contamination than the conventional hydrochloric acid oxidation method.

[0060]

As described above in detail, according to the dry cleaning method of the present invention, the contaminant metal adsorbed on the substrate surface during the element forming step can be easily and effectively gettered in the gas phase, and the reliability is high. And a remarkable effect such as the ability to manufacture a high-speed semiconductor device.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing a state in which a contaminant metal is attached to the surface of a silicon substrate and gettering into a gas phase.

FIG. 2 is a cross-sectional view showing a state in which a contaminant metal is taken into the surface and inside of a natural oxide film on a silicon substrate.

FIG. 3 is a cross-sectional view showing a state in which a contaminant metal is attached to the inner surface of a contact hole of an insulating film on a silicon substrate.

FIG. 4 is a cross-sectional view showing a state in which a contaminant metal is attached to the surface of a thermal oxide film on a silicon substrate and gettering into a gas phase.

FIG. 5 is a sectional view showing a state in which a contaminant metal is attached to the surface of a silicon nitride film on a silicon substrate.

FIG. 6 is a characteristic diagram showing the relationship between the temperature when a silicon substrate is heat-treated in a non-oxidizing atmosphere containing HCl and the occurrence of etch pits on the substrate surface.

FIG. 7 is a schematic view showing a horizontal processing apparatus used in the dry cleaning treatment of the present invention.

FIG. 8 is a schematic view showing a vertical processing apparatus used in the dry cleaning treatment of the present invention.

FIG. 9 shows the amount of Fe on the surface and inside of the thermal oxide film after the silicon substrate having a thick thermal oxide film forcibly contaminated with Fe formed on the surface in Comparative Examples 1 to 3 and Example 1; Characteristic diagram.

FIG. 10 shows the temperature and the amount of Fe remaining on the surface and inside of the thermal oxide film when a silicon substrate having a thick thermal oxide film forcibly contaminated with Fe formed on the surface is treated in Comparative Example 4 and Example 2. FIG. 3 is a characteristic diagram showing a relationship with the graph.

FIG. 11 shows the relationship between the temperature and the amount of residual Ni on the surface and inside of the thermal oxide film when a silicon substrate having a thick thermal oxide film forcibly contaminated with Ni formed on the surface is treated in Example 3. FIG.

FIG. 12 shows the relationship between the temperature and the amount of Fe remaining on the surface and inside the natural oxide film when a silicon substrate having a natural oxide film forcibly contaminated with Fe formed on the surface is treated in Example 4. Characteristic diagram.

FIG. 13 shows a surface layer of the silicon substrate and a F in the gate oxide film when the silicon substrate whose surface is contaminated with Fe is processed in Example 5 and Comparative Example 5 to form a gate oxide film.
FIG. 4 is a characteristic diagram showing an e amount.

FIG. 14 shows the temperature and the A in the oxide film when a silicon substrate on which a natural oxide film on which Al was adsorbed was treated in Example 7.
FIG. 4 is a characteristic diagram showing a relationship with an l amount.

FIG. 15 is a characteristic diagram showing the amount of Al in an oxide film formed by processing a silicon substrate on which a natural oxide film on which Al is adsorbed is formed in Examples 8 and 9 and Comparative Example 6.

FIG. 16 is a sectional view showing a problem of the conventional hydrochloric acid oxidation method.

FIG. 17 is a characteristic diagram showing a thermal behavior of Fe adsorbed on a substrate surface in an HCl oxidizing atmosphere.

FIG. 18 is a cross-sectional view showing the thermal behavior of Fe adsorbed on the substrate surface when heat treatment is performed in an HCl oxidizing atmosphere at different temperatures.

[Explanation of symbols]

21 silicon substrate, 22 thermal oxide film, 23 contaminated metal, 24 silicon nitride film, 25 natural oxide film, 28
Contact hole.

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-3-64024 (JP, A) JP-A-3-127830 (JP, A) JP-A-2-49428 (JP, A) JP-A-4- 157161 (JP, A) JP-A-5-121394 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H01L 21/304 645 H01L 21/306

Claims (3)

(57) [Claims] 1. A vertical external reactor having a gas inlet at a lower portion, a gas inlet hole disposed at an upper portion of the reactor, and a gas inlet hole at an upper portion.
A vertical internal reactor with an exhaust port formed at the bottom,
A semiconductor device having a semiconductor substrate or a surface on which various films are formed using a processing apparatus including a holder disposed in the vertical reactor and a heater disposed around a side surface of the vertical external reactor. The cleaning performed immediately before the step of performing oxidation or diffusion after holding and installing the substrate in the holder disposed in the internal reaction furnace so that most of the front and back surfaces of the semiconductor substrate are exposed. A method comprising: introducing a gas containing a halogen or a halide into a space between the external reactor and the vertical internal reactor from an inlet at a lower portion of the vertical external reactor and raising the same; The gas is heated by the heater, and the heated gas is exhausted from the gas introduction hole in the upper part of the vertical internal reactor through the inside thereof through the lower exhaust port, thereby displaying the gas on the holder in the internal reactor. Back side Contacting a gas containing retained the heated to a temperature of the semiconductor substrate to 400 to 600 ° C. was a halogen or halide as exposed to heat treatment, Al of front and back surfaces of the semiconductor substrate
A dry cleaning method for a semiconductor device, comprising removing minium . 2. The dry cleaning method for a semiconductor device according to claim 1, wherein the gas containing a halogen or a halide is a non-oxidizing gas containing a halogen or a halide. 3. A dry cleaning method for a semiconductor device according to claim 1, wherein said halide is HCl.