JP3210510B2 - Method for manufacturing 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 a method for manufacturing a semiconductor device, and more particularly to a method for manufacturing a semiconductor device having a step of forming a highly reliable insulating film.

[0002]

2. Description of the Related Art In recent years, large-scale integrated circuits (ICs) formed by integrating a large number of transistors, resistors, and the like into an important part of a computer or a communication device so as to achieve an electric circuit are integrated on one chip. LSI) is frequently used. For this reason, the performance of the entire device is greatly related to the performance of the LSI alone.

[0003] The performance of a single LSI can be improved by increasing the degree of integration. For that purpose, it is necessary to establish a highly reliable manufacturing technique. Among the factors that degrade the performance of the semiconductor device, the following four are the largest factors related to the manufacturing process.

(A) Heavy metals typified by Fe, Cu, etc. and light metals typified by Al, Na, etc. (B) Natural oxide films formed on substrates by wet cleaning and uncontrolled atmospheres (C) Uncontrolled atmospheres (D) Micro-roughness on the semiconductor substrate surface (A) Metal impurities such as organic matter in a clean room and organic matter from a substrate storage container, such as a breakdown voltage of a gate insulating film and a leak current Etc. may cause deterioration.

[0005] The natural oxide film (B) increases as the time for which the substrate is left to stand after the wet HF treatment is increased. Further, in the case of forming a gate oxide film requiring a thin film thickness of about 10 nm or less, the presence of a natural oxide film (B) having poor film quality causes deterioration of the characteristics of the entire gate oxide film.

The organic substance (C) is adsorbed by leaving the wafer in the air. In addition, S used for dust removal
C1 cleaning (RCA cleaning) and the like use an alkaline etching solution, and therefore increase the micro roughness (D) of the substrate surface. Furthermore, in recent years, it has become clear that organic substances and metals adsorbed on the gate insulating film cause abnormal growth of crystal grains of the polycrystalline semiconductor thin film.

The micro-roughness (D) lowers the reliability of the gate oxide film such as withstand voltage characteristics. In the case of forming a thin gate oxide film, when the micro roughness (D) on the substrate surface increases, local electric field concentration occurs in the gate insulating film, resulting in dielectric breakdown.

In general, the causes of defects (A) to (C) are first removed by wet cleaning. However, although it actually varies depending on the acidity of the cleaning solution, the metal impurities (A) in the cleaning solution are presently present on the active substrate surface at 10 ^9.
There is a problem of reverse adsorption of about 10 to 10 ¹² atoms / cm ² .

Also, at present, after a gate oxide film is formed in an oxidation furnace, LP electrodes are deposited on the oxide film.
The substrate is transported to another film forming apparatus such as a CVD apparatus. Therefore, it is impossible to avoid a phenomenon in which metal impurities (A), organic substances (C) in a clean room, organic substances (C) from a wafer storage container, and the like are adsorbed on the gate oxide film.

In a semiconductor device that requires a highly reliable oxide film, as typified by a nonvolatile memory such as an EEPROM, in the manufacturing process, these failure factors are more strictly controlled than ever before, and are thoroughly implemented. It is required to eliminate them.

For this reason, in recent years, a so-called continuous processing technique has been proposed in which a required process is continuously performed after a required dry cleaning process is performed in a controlled atmosphere without exposing the semiconductor substrate to the outside air. I have.

For example, in the case of forming a gate oxide film,
The mainstream is to form a gate oxide film after the step of removing the metal impurities (A) and the natural oxide film (B) or the step of removing the organic substance (C).

The causes of the above failures (A) to (D) are the same in the case of an insulating film requiring high reliability, particularly a tunnel oxide film to which a high electric field is applied. It will bring down.

However, although a technique for individually removing each failure factor has been conventionally proposed, a technique for consistently removing all the failure factors has not been proposed. Therefore, it is difficult to form a highly reliable tunnel oxide film, and it is difficult to improve the reliability of a semiconductor device such as an EEPROM.

[0015]

As described above, in the case of forming an insulating film requiring high reliability, the above (A) to (D)
All of the failure factors up to this point result in equivalent failure or performance degradation. However, the conventional technique has a problem that the cause of the failure cannot be removed consistently, and it is difficult to form a highly reliable insulating film.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a method of manufacturing a semiconductor device having a process capable of consistently removing a cause of a defect before forming an insulating film. Is to provide.

[0017]

According to a first aspect of the present invention, there is provided a method of manufacturing a semiconductor device, comprising the steps of batching a plurality of substrates to be processed having a natural oxide film formed on a surface thereof.
A first step of removing at least one of the organic substance and the metal present in the natural oxide film by dry cleaning in a state where the plurality of substrates are housed in one processing chamber of the formula and the plurality of substrates to be processed are shielded from outside air; after the first step, a second step of removing the natural oxide film by dry cleaning, have a third step of forming an insulating film on the natural oxide film is removed region, and the first Step 3 to Step 3
A series of steps up to the above is continuously performed in the processing chamber .

Further, another method for manufacturing a semiconductor device of the present invention (Claim 2) has a plurality of forming a sacrificial oxide film in advance surface
The first substrate is accommodated in one batch-type processing chamber, and at least one of an organic substance and a metal present in the sacrificial oxide film is removed by dry cleaning in a state where the substrate to be processed is shielded from the outside air. And after the first ′ step, a second ′ step of removing the sacrificial oxide film by dry cleaning, and a third ′ step of forming an insulating film in a region where the sacrificial oxide film has been removed. Yes and, and the first '
A series of steps from the step to the third 'step
It is characterized in that it is performed continuously in a room .

Another method of manufacturing a semiconductor device according to the present invention.
(Claim 9) is a processing target having a natural oxide film formed on the surface.
The substrate is accommodated in a processing chamber, and the substrate to be processed is shielded from outside air.
In the disconnected state, the organic substance existing in the natural oxide film or
Removing at least one of the metals by dry cleaning
Step 1 and after the first step, dry the native oxide film.
A second step of removing by cleaning, and the natural oxide film
A third step of forming an insulating film in a region where
And between the first step and the third step,
A step of flattening the surface of the substrate to be treated.
Sign. Further, another method of manufacturing a semiconductor device according to the present invention.
(Claim 10) relates to a substrate in which a sacrificial oxide film is previously formed on the surface.
The processing substrate is accommodated in a processing chamber, and the processing target substrate is
In the state where the organic matter and the organic substances existing in the sacrificial oxide film are
And / or metal is removed by dry cleaning
A first 'process and after the first' process, the sacrificial oxide film
A second 'step of removing the sacrifice by dry cleaning;
Forming an insulating film in the region where the oxide film has been removed;
And the first 'step and the third' step
A step of flattening the surface of the substrate to be processed.
It is characterized by having . Preferred embodiments of the present invention are as follows.

Embodiment (1) After performing wet cleaning for forming a natural oxide film on the surface of the substrate to be processed, the substrate to be processed is housed in the processing chamber.

Embodiment (2) After the third (3 ') step, a step of forming an electrode on the insulating film is continuously performed while the substrate to be processed is housed in the processing chamber.

Embodiment (3) In the step of forming an insulating film on the substrate to be processed in the third (3 ′) step, after forming an initial insulating film of about 1 nm or less at a temperature of 700 ° C. or less, An insulating film is formed continuously.

Embodiment (4) In the flattening process, an oxide film (sacrificial oxide film) is formed by oxidizing the surface of the substrate to be processed, and a peeling step of the sacrificial oxide film by dry cleaning is repeated at least once. Or a step of growing a silicon epitaxial thin film on the surface of the substrate to be processed, a step of etching the surface of the substrate to be processed by chemical dry etching (CDE), or a step of cleaning the surface of the substrate to be processed in a vacuum or inert gas. 80
It comprises a step of annealing at a temperature of 0 ° C. or higher.

Embodiment (5) In the embodiment (4), the step of forming a sacrificial oxide film is performed using a gas containing at least an oxygen element and a halogen element.

Embodiment (6) In the embodiment (4), the dry cleaning step of the sacrificial oxide film is performed by exposing the sacrificial oxide film in a gas atmosphere containing HF.

Embodiment (7) Existing in the sacrificial oxide film (for example, the surface of the sacrificial oxide film,
(Internal) Before the step of removing at least one of an organic substance and a metal by dry cleaning, water, an organic solvent, fine particles in which silicone or the like is condensed on the surface of the sacrificial oxide film, or fast gas atoms or molecular beams, or low energy ions. Irradiation is performed to remove dust on the surface of the sacrificial oxide film.

Embodiment (8) The removal of the metal in the first (1 ') step by dry cleaning is performed by heat-treating the substrate to be treated in a gas atmosphere containing a halogen element. In this case, particularly 400 ° C. or more and 600 ° C. or less,
Preferably, the heat treatment is performed at a temperature of 550 ° C. or less. Further, it is preferable to perform the treatment in a non-oxidizing atmosphere.

Embodiment (9) The removal of organic substances by dry cleaning in the first (1 ') step is as follows:
Heat-treating the substrate to be processed in a gas atmosphere containing an oxygen element,
The organic matter is ashed.

Embodiment (10) The removal of the natural oxide film by dry cleaning in the second (2 ') step is performed by exposing to a gas containing HF, hydrogen or a silane-based gas, or in vacuum or The heat treatment is performed on the substrate to be processed in an inert gas atmosphere.

In the present invention, the sacrificial oxide film refers to an oxide film formed in advance on the surface of the substrate to be processed, and is formed by oxidizing the surface of the substrate to be processed by plasma oxidation, thermal oxidation, or the like. Alternatively, an oxide film such as an oxide film of a substrate constituent material may be formed on the surface of the substrate to be processed by a CVD method. In this case, it is also possible to form another insulating film such as a nitride film of the base material.

[0031]

According to the study of the present inventors, it has been found that the order of removal is important when considering the removal of defective factors in a consistent manner. That is, when all of the failure factors (A) to (C) are consistently removed, it has been found that it is sufficient to remove each failure factor in the order of the present invention (claims 1 and 2).

Further, it has been found that when all of the failure factors (A) to (D) are consistently removed, each failure factor may be removed in the order of the present invention (claim 3). Hereinafter, the contents of the present invention and embodiments will be described.

First, a cleaning process for forming a natural oxide film is performed as wet cleaning in order to remove the cause of failure of the metal impurities (A) and organic substances (C) adsorbed on the semiconductor substrate. Store in a reaction chamber where the atmosphere is controlled.

At this time, if the final finishing is performed by HF-based wet cleaning + water cleaning processing, the surface of the active silicon substrate is exposed in a solution or a gaseous phase. The reverse contamination of C) becomes a problem.

For example, some metals such as Cu and Ni
When present in an F-based solution, it is reversely adsorbed on the surface of an active silicon substrate. These metals have a disadvantage that they form a stable metal silicide when they are adsorbed on the substrate surface.

When removing the semiconductor substrate from the cleaning solution, dust and organic substances in the clean room are adsorbed on the surface of the active silicon substrate. Organic substances adsorbed on the surface of the active silicon substrate are temporarily converted into silicon carbide (Si-
When a stable bond such as C) is formed, even if dry cleaning is performed thereafter, removal is very difficult by a cleaning method that does not involve etching of the semiconductor substrate. Furthermore, when a cleaning method involving etching is performed,
Micro-roughness (D), another factor of failure, increases from the difference in etching rates.

Therefore, if a natural oxide film is formed in the final finish, the above-mentioned problem that the metal impurities (A) and the organic substance (C) are directly adsorbed on the semiconductor substrate can be solved. By dry cleaning, it can be removed without adversely affecting the semiconductor substrate.

Next, the metal impurities (A) and the organic substances (C) which have been removed to some extent by wet cleaning are completely removed by in-line dry cleaning. For these, any method may be used.

For example, in an oxidizing atmosphere to which a gas containing a halogen atom (eg, HCl gas) is added, for example, about 60
By performing the heat treatment at a temperature of about 0 ° C. or less, the metal impurities (A) and the organic substances (C) on the semiconductor substrate can be removed.

In this case, the metal impurity (A) is removed as a metal chloride having a high vapor pressure in the gas phase, while the organic matter (C) is burned in an oxidizing atmosphere to form carbon dioxide gas. Removed during phase.

Next, the natural oxide film (C) is removed. Dry cleaning of the natural oxide film is performed by exposure to an atmosphere of a gas containing HF, hydrogen or a silane gas, or heat treatment in a vacuum or an inert gas atmosphere.

It is important to remove the above-mentioned failure factors (A) to (C) in this order. This is because, as described above, when the natural oxide film (B) is removed before the removal of the metal impurities (A) and the organic substance (C), these impurities are bonded to the active silicon substrate surface ( This is because some of them are diffused into the silicon substrate), making removal difficult.

In particular, when the natural oxide film (C) is removed with a gas containing HF, a part of the metal impurities (A) remaining on the surface of the silicon substrate becomes a stable fluoride as described above. It cannot be removed in the subsequent dry cleaning. When the natural oxide film (C) is removed by silane reduction, high-temperature annealing in vacuum or an inert gas, the metal impurities (A) on the silicon substrate are removed from the silicon substrate due to the high-temperature treatment. In the subsequent removal of the metal impurities (A) and organic substances (C), they cannot be efficiently removed.

As another reason, if the removal of the metal impurity (A) using a halogen-based gas after the removal of the natural oxide film (C) is performed first, the silicon substrate is also etched at the same time. Therefore, the micro roughness (D) on the substrate surface increases.

Due to the above problems, in the present invention, the natural oxide film is removed after removing the metal impurities (A) and the organic substances (C). After removing the metal impurities (A) and the organic matter (C), the micro roughness (D) is removed.
Before or after the removal of the natural oxide film (B), the process including the step of forming the sacrificial oxide film and the step of removing the sacrificial oxide film by dry cleaning is repeated one or more times, so that the substrate surface can be planarized.

Alternatively, a metal impurity (A) and an organic substance (C)
After removing the above, the surface of the substrate can be flattened by performing high-temperature annealing at about 800 ° C. or more in a vacuum or an inert gas atmosphere.

Other micro-roughness (D) can be removed by removing a native oxide film (B), epitaxially growing a silicon thin film on a silicon substrate, or by flattening CDE.

By removing the defective factors (A) to (D) in this order, the defective factors (A) to (D) are removed consistently and effectively. Further, in addition to the above-described dry cleaning step, a step of forming an insulating film (oxidizing step) and a step of forming a semiconductor thin film for an electrode (electrode film forming step), which is a depressurizing process, are continuously performed in the same reaction chamber. Thereby, for example, abnormal growth of crystal grains in the polycrystalline semiconductor thin film as the semiconductor thin film for the electrode, which is caused by the metal impurity (A) or the organic substance (C) adsorbed on the gate insulating film, can be prevented.

Therefore, for a device requiring a highly reliable insulating film, such as a flash memory, as described above, various causes of failure can be consistently and effectively determined before the insulating film forming step. It is very important that a series of MOS manufacturing steps including a dry cleaning step for removing, a gate insulating film forming step, and an electrode film forming step be continuously performed in a controlled process atmosphere.

Next, another method (claim 2) of the present invention will be described. In this method, except for a wet cleaning process for removing a certain amount of metal impurities and dust adsorbed on a sacrificial oxide film formed on a gate oxide film formation region, a wet cleaning pretreatment is performed on a portion where a gate oxide film is to be formed. It is characterized by not performing it at all.

First, the semiconductor substrate is wet-cleaned in order to remove a certain amount of dust adsorbed on the sacrificial oxide film formed on the gate oxide film formation region. Next, the semiconductor substrate is housed in a film forming apparatus in which dust, impurities and the like are controlled.
After that, if necessary, the surface of the sacrificial oxide film is irradiated with fine particles obtained by condensing water, an organic solvent, silicone, or the like, or any of high-speed gas atoms, high-speed gas molecular beams, or low-energy ions, to perform wet cleaning. The dust on the surface of the sacrificial oxide film that has been reversely adsorbed before the film device is carried in is removed.

Next, after removing the metal impurities (A) and the organic substance (C) on the sacrificial oxide film by dry cleaning, the sacrificial oxide film is removed by dry cleaning in a gas atmosphere containing HF.

Next, in order to flatten the micro-roughness (D) on the substrate surface, a process including the formation of a sacrificial oxide film and the step of removing the sacrificial oxide film by dry cleaning is repeated one or more times. Alternatively, the micro-roughness (D) on the substrate surface can be flattened by performing high-temperature annealing at about 800 ° C. or more in a vacuum or an inert gas.

Thereafter, a gate oxide film and a polycrystalline semiconductor film for an electrode are formed. Instead of flattening by the above method, after removing the sacrificial oxide film, an epitaxial thin film may be grown on a silicon substrate, or by flattening CDE.
Micro-roughness (D) can be flattened.

Unlike the conventional process sequence of performing a wet cleaning process as a pretreatment before forming a gate oxide film after removing the sacrificial oxide film by wet cleaning, the present invention manages the sacrificial oxide film. Since the gate oxide film is peeled off by dry cleaning in a process atmosphere, the gate oxide film can be formed only by dry cleaning without exposing the region where the gate oxide film is formed to any outside air. Therefore, the occurrence of the causes of the defects (A) to (D) can be completely prevented, and the causes of the defects can be consistently removed, so that a highly reliable gate oxide film can be formed.

[0056]

Embodiments will be described below with reference to the drawings. A process sequence according to the first embodiment of the present invention will be described with reference to FIGS. FIG. 1 is a film forming apparatus for realizing the method of manufacturing a semiconductor device according to the present invention, FIG. 2 is a process sequence, and FIG. The above-mentioned film forming apparatus is of a batch type / hot wall type and comprises one reaction chamber.

First, a plurality of semiconductor substrates 1 (FIG. 3 (a)) on which a field oxide film 22 is formed on the surface and dust and impurities have been removed to some extent by wet cleaning are loaded on a heat treatment boat 7. It is inserted into the reaction chamber 5.
(FIG. 1 (a), FIG. 2 (substrate carry-in)).

At this time, the temperature of the reaction chamber 5 is maintained by the heater 6 at a temperature at which the substrate surface is not oxidized during the substrate carrying-in processing time, for example, about 400 ° C. or less. Next, after the reaction chamber 5 is sealed from outside air (FIG. 1B), the gas in the reaction chamber 5 is sufficiently replaced with an inert gas such as nitrogen.
After that, the semiconductor substrate 1 is placed in a controlled and controlled process gas atmosphere.

Next, a first process gas is introduced from the introduction system 8, the atmosphere in the reaction chamber 5 is set to the first atmosphere 1, and metal impurities and organic substances 3 on the substrate surface are removed (impurity removal) (FIG. 2, FIG. 3 (b)).

Next, after sufficiently replacing the first process gas with an inert gas or the like, a second process gas is introduced from the introduction system 8, the atmosphere in the reaction chamber 5 is changed to the second atmosphere 2, and the semiconductor The natural oxide film 4 on the surface of the substrate 1 is removed (natural oxide film removal) (FIGS. 2 and 3C).

Next, after sufficiently replacing the second process gas with an inert gas or the like, a third process gas is introduced from the introduction system 8, and the atmosphere in the reaction chamber 5 is changed to the third atmosphere 3.
Next, the temperature of the semiconductor substrate 1 and the third atmosphere 3 in thermal equilibrium with the reaction chamber 5 are raised at a high speed to an oxidation temperature, for example, about 900 ° C., and maintained for a predetermined time, and the gate oxide film 23 is formed on the semiconductor substrate 1. Is formed (oxide film formation) (FIGS. 2 and 3D).

At this time, in order to prevent re-formation of the natural oxide film, it is preferable that the temperature is raised at a rate of at least about 100 ° C. per minute. After the oxidation for forming the gate oxide film is completed, the third atmosphere 3 may be replaced with an inert gas or the like, and then the gate oxide film 23 may be annealed.

If it is necessary to stabilize the active semiconductor substrate 1 after the removal of the metal impurities and organic substances 3 and the natural oxide film 4 and before the next step of forming the gate insulating film 23, the temperature is set at 700 ° C. It is also possible to form a clean initial oxide film having a thickness of about several nm at a low temperature of about not more than that, and to stabilize an active surface.

It is possible in principle to sufficiently dilute the third atmosphere 3 during the temperature rise with an inert gas such as nitrogen or argon to suppress the growth of a natural oxide film on the semiconductor substrate. In this case, it is necessary to make the dilution ratio extremely high in order to completely prevent the influence of the natural oxide film, and it is difficult to avoid non-uniformity of the gas composition ratio in the reaction chamber. Impossible. Further, in this case, heating the semiconductor substrate having an exposed surface to an ordinary oxidation temperature in an atmosphere containing no oxidizing species leads to a fatal defect in device manufacture due to surface roughness of the semiconductor substrate.

Next, the temperature of the reaction chamber 5 is lowered in the third process gas to a temperature required for the step of depositing the polycrystalline semiconductor film to be the gate electrode. The temperature may be lowered in an oxidizing atmosphere or after replacing the third atmosphere 3 with an inert gas or the like. After the temperature is lowered, the third process gas or the inert gas is heated to a pressure at which the polycrystalline semiconductor can be deposited, for example, 10
After sufficiently exhausting to a reduced pressure atmosphere of about ^-3 Torr or less, a fourth process gas is introduced from the introduction system 8, the atmosphere in the reaction chamber 5 is changed to the fourth atmosphere 4, and the polycrystalline semiconductor serving as the gate electrode is formed. The film 24 is deposited (electrode film deposition).
(FIGS. 2 and 3 (e)).

Finally, the fourth process gas is sufficiently evacuated, purged with an inert gas or the like, and cooled down.
The semiconductor substrate 1 on which the S structure is formed is unloaded from the reaction chamber 5 (substrate unloading).

The manufacturing method of this embodiment includes a step of removing metal impurities and organic substances 3 on the semiconductor substrate 1 on which the native oxide film 4 is formed, a step of removing the native oxide film 4 on the semiconductor substrate 1, The step of forming the gate oxide film 23 and the step of forming the polycrystalline semiconductor film 24 on the gate oxide film 23 are continuously performed in one reaction chamber 5 while the semiconductor substrate 1 is kept out of the outside air. It is characterized by:

Further, in the case of flattening the micro roughness on the semiconductor substrate 1, it is necessary to repeat the step of forming and removing the sacrificial oxide film at least once before or after the removal of the native oxide film 4. . Alternatively, it is necessary to perform high-temperature annealing at about 800 ° C. or more in a vacuum or an inert gas atmosphere. The planarization can also be performed by performing silicon epitaxial growth after removing the native oxide film 4 or performing planarization CDE after removing the native oxide film 4.

From the process leading up to the present invention, all of the above series of processing should be performed continuously. However, considering the structure of the device or the performance of the device, the continuous processing up to the formation of the insulating film (gate oxide film) is performed. Good ones can be taken out of the reaction chamber 5 after the formation of the insulating film.

In order to realize the method of manufacturing a semiconductor device according to the present invention, as shown in this embodiment, a case where all of the above steps are performed by a film forming apparatus including one reaction chamber which is cut off from the outside air. Since there is no substrate transport other than loading and unloading, unstable elements such as contamination from the outside and generation of dust can be completely eliminated during the creation of the MOS structure, for example.

Further, since the process can be carried out in one reaction chamber, impurities such as moisture (p
(pb or less) can be continuously processed in a high temperature state of several hundred degrees Celsius or more, for example, in a state where the reaction chamber and the semiconductor substrate are kept at 200 ° C. or more, so that the substrate is hardly adsorbed on the substrate surface.

Next, heavy metal Fe which is a typical metal impurity
A MOS capacitor was formed on a semiconductor substrate contaminated with Cu and Cu by the manufacturing method of the present invention described in this embodiment, and the effect was examined.

A MOS capacitor was manufactured according to the method of this embodiment using a silicon substrate whose natural oxide film was contaminated with Fe and Cu. As a sample of Comparative Example 1, a metal capacitor (Fe, Cu) and a natural oxide film were simultaneously removed to form a MOS capacitor. Further, as a sample of Comparative Example 2, a MOS capacitor was prepared by reversing the metal impurity removing step and the natural oxide film removing step.

FIGS. 4 and 5 show the results of comparing the electrical characteristics of these MOS capacitors. FIG. 4 shows the results of comparing the dielectric breakdown lifetime with time of the present invention and the MOS capacitors of Comparative Examples 1 and 2 using Weibull plots. It can be seen from FIG. 4 that the life of the present invention is improved by one digit or more by one digit or more, respectively, as compared with Comparative Examples 1 and 2.

FIG. 5 shows the result of comparing the generation lifetimes (Ct) of the MOS capacitors. Also in this case, it can be seen that the carrier generation time is longer in the present invention than in Comparative Examples 1 and 2.

The reason why such a result is obtained will be described with reference to FIG. As shown in FIG. 6A, in the case of the present invention, the natural oxide film is removed after Fe and Cu are effectively removed in the first impurity removal step, so that the cause of the failure is matched. Removed. Therefore, a high quality MOS capacitor is produced.

On the other hand, as shown in FIG.
In the case of, even if the metal impurities (Fe, Cu) 3 and the natural oxide film are removed at the same time, the Fe, Cu
3 is a region where the gate oxide film 23 is formed.
Will be combined with In addition, some metal impurities 3 react with anhydrous HF gas used for removing the native oxide film, and are converted into stable metal fluorides. If the gate oxide film 23 is formed in such a state, the metal impurities 3 are known in the silicon substrate 1 or the gate oxide film 23, and the electrical characteristics deteriorate.

Further, as shown in FIG.
In the case of (1), since the natural oxide film is removed first, metal impurities 3 such as Fe and Cu remain on the surface of the active silicon substrate 1 as compared with the comparative example 1 or more.
Alternatively, they are taken into the gate oxide film 23 and the electrical characteristics are degraded. Further, when the natural oxide film is removed by silane reduction, the treatment needs to be performed at a high temperature, so that most of the Fe and Cu adsorbed on the surface of the silicon substrate 1 diffuses into the semiconductor substrate.

A method of continuously performing the metal impurity removing step and the oxidizing step is described in Japanese Patent Application Laid-Open No. HEI 3-12973.
5, and a method of continuously performing the step of removing the natural oxide film and the step of oxidizing are disclosed in JP-A-3-55838, JP-A-3-55840, and the like. However,
As can be seen from the above results, a highly reliable MOS semiconductor device cannot be manufactured even by performing such a partial continuous processing process.

Next, a method of manufacturing a MOS type semiconductor device according to a second embodiment of the present invention will be described. An example of the manufacturing process of this embodiment will be specifically described with reference to FIGS.

First, in order to remove dust adsorbed on the sacrificial oxide film 25 formed in the formation region of the gate oxide film, the semiconductor substrate 1 is subjected to an alkaline wet cleaning process.
Next, the semiconductor substrate 1 is housed in a film forming apparatus whose atmosphere is controlled (FIG. 7A).

Thereafter, if necessary, fine particles of water, organic solvent, silicone, etc. condensed on the surface of the sacrificial oxide film 25,
Irradiation with any of high-speed gas atoms, high-speed gas molecular beams, and low-energy ions is performed to remove dust adsorbed on the surface of the sacrificial oxide film 25 during transport by dry cleaning.

Next, in order to remove the metal impurities 3 and the organic impurities 26 on the sacrificial oxide film 25, dry cleaning is performed by heat treatment in an oxidizing atmosphere containing HCl gas, for example (FIG. 7B).

Next, in order to remove the sacrificial oxide film 25, for example, dry cleaning using anhydrous HF gas is performed (FIG. 7).
(C)). Next, in order to flatten the micro-roughness of the substrate surface, for example, the formation of a sacrificial oxide film and the peeling step are repeated one or more times (FIG. 8A). At this time, in the step of removing the sacrificial oxide film, for example, anhydrous HF gas is used.

Next, a gate oxide film 23 is formed (FIG. 8B). At this time, before forming the gate oxide film 23,
In order to stabilize the active substrate surface after the removal of the sacrificial oxide film, an insulating film having a thickness of about 1 nm or less is formed once at a low temperature of 700 ° C. or less, and then the gate insulating film 23 is formed. Leakage current when applying an electric field can be sufficiently reduced.

Finally, a polycrystalline semiconductor film 24 serving as a gate electrode is formed on gate insulating film 23 (FIG. 8).
(C)). In the above process, a dry process for removing metal impurities on the sacrificial oxide film or the semiconductor substrate is performed between the step of forming the sacrificial oxide film for planarization and the peeling step thereof, or after the peeling of the sacrificial oxide film. A cleaning process may be performed.

The semiconductor substrate to be first inserted into the film forming apparatus can be processed not only with the sacrificial oxide film described in this embodiment but also with the natural oxide film. .

According to this method, the region where the gate oxide film is formed is not exposed to the outside air and is not exposed to the wet cleaning process. All can be removed consistently.

FIG. 9 shows the relationship between the number of times of the micro-roughness flattening process and the average in-plane roughness. The average in-plane roughness was measured using an atomic force microscope (AFM). In the figure, the vertical axis represents the average surface roughness Ra observed by AFM.
(Nm), and the horizontal axis indicates the number of times of sacrificial oxidation / peeling. It can be seen from FIG. 9 that the flatness is improved to some extent by repeating the process of forming the sacrificial oxide film and the process of removing the same.

The MOS fabricated according to the method of this embodiment
Capacitors (invention) and conventionally made MOS
The reliability of the capacitor (Comparative Example 3) was evaluated.

More specifically, the silicon substrate on which the sacrificial oxide film is formed is not exposed to outside air at all in the region where the gate oxide film shown in this embodiment is formed, and the impurities and the natural oxide film are removed by all-dry cleaning. Is removed, and the MOS substrate (the present invention) formed after the silicon substrate in the region where the gate oxide film is formed is planarized, and the sacrifice oxide film is removed by an HF wet cleaning process. R
After performing the CA wet cleaning, the silicon substrate was carried into a film forming apparatus, a halogen gas was activated using ultraviolet light (UV light), and metal impurities and a natural oxide film on the substrate surface were removed. Later, for a MOS capacitor (Comparative Example 3) formed by a conventional continuous process of forming a gate insulating film,
The aging dielectric breakdown life was evaluated.

FIG. 10 shows the results of comparing the dielectric breakdown lifetime with time of the gate insulating film by using a Weibull plot.
From FIG. 10, it can be seen that the present invention has a longer dielectric breakdown life with time and a higher reliability of the gate insulating film than the comparative example 3.

The first reason is that, in Comparative Example 3, since the gate oxide film formation region is processed by the conventional wet cleaning process including the HF-based wet cleaning process, impurities in the chemical solution are transferred to the gate active region. This is because the problem of reverse adsorption or diffusion into the silicon substrate cannot be essentially solved.

Second, a comparative example 3 in which a wet cleaning treatment is performed for dusts of 0.1 μm or less or organic substances composed of hydrocarbons, which is difficult to detect with a particle counter.
This is because the adsorption amount cannot be sufficiently controlled.

Third, it is conceivable that a process for flattening the micro roughness on the substrate surface is not performed. From the above results, when the wet cleaning step was performed immediately before the formation of the gate oxide film as in Comparative Example 3, the impurities and the natural oxide film on the surface of the silicon substrate were thereafter removed by dry cleaning, and then the gate insulating film was removed. It can be seen that even if a conventional continuous process for forming a film is performed, the cause of the defect that lowers the reliability of the device cannot be removed consistently.

On the other hand, in the case of this embodiment, the problem is that the sacrificial oxide film is located on the region where the gate insulating film is formed, and the gate active region is not exposed to the wet cleaning step and the outside air which cause instability. Only dust, organic matter, and metal impurities on the sacrificial oxide film are formed. For this reason, when these are removed in a consistent manner, the gate oxide film formation region is not exposed to the instability factor, so that a high-quality gate insulating film is formed.

FIG. 11 shows the dependence of the charge retention characteristics of the present invention and the conventional DRAM on the high-temperature leaving time. FIG.
Therefore, in the case of the conventional example, the charge retention characteristics deteriorate as the high-temperature retention time elapses, but in the case of the present invention, there is no dependency on the high-temperature storage time, and good charge retention characteristics are maintained. I understand. This indicates that the conventional method has impurity contamination inside the substrate and in the oxide film (gate oxide film).
On the other hand, the present invention shows that impurity contamination inside the substrate and in the oxide film is suppressed.

The present invention is not limited to the embodiment described above. For example, in the above embodiment, the case of the insulating film (gate oxide film) by thermal oxidation has been described.
The present invention can be applied to a deposited insulating film formed by CVD or the like.

Specifically, in addition to a nitride film made of dichlorosilane and ammonia, a high dielectric film such as tantalum oxide and strontium titanate may be used. In addition, not only an insulating film such as a single-layer silicon thermal oxide film and a nitride film but also an insulating film to which impurities are added, for example, a thermal oxide film is nitrided by a nitriding gas such as ammonia or nitrogen monoxide (N ₂ O). The present invention can also be applied to a modified oxynitride film. Similarly, the present invention can be applied to an insulating film to which a halogen element is added.

In the above embodiment, only the thermal oxidation of the silicon semiconductor substrate has been described. However, the present invention can be applied to a semiconductor thin film such as a polysilicon film or an amorphous silicon film.

Furthermore, taking into account the method of introducing the process gas, surface treatment by chemical dry etching such as CDE can be performed in the manufacturing apparatus according to the present invention. Further, in the above-described embodiment, the case where a batch-type / hot-wall-type / single-processing chamber film forming apparatus is used has been described.
A film forming apparatus including a single-wafer / cold-wall processing chamber or a single-wafer / hot-wall processing chamber may be used. In addition, various modifications can be made without departing from the scope of the present invention.

[0102]

As described in detail above, according to the present invention, the cause of a defect can be removed in a consistent manner, so that a highly reliable insulating film can be formed.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing a schematic configuration of a film forming apparatus for realizing a method of manufacturing a semiconductor device according to the present invention.

FIG. 2 is a process sequence showing a method for manufacturing a semiconductor device according to the present invention.

FIG. 3 is a process sectional view showing the manufacturing method according to the first embodiment of the present invention;

FIG. 4 is a diagram showing the time-dependent dielectric breakdown life of the MOS capacitors of the present invention and a comparative example.

FIG. 5 is a diagram showing the generation lifetimes of the MOS capacitors of the present invention and a comparative example.

FIG. 6 is a diagram showing a difference in the state of contamination between the present invention and a comparative example.

FIG. 7 is a process sectional view showing the first half of the manufacturing method according to the second embodiment of the present invention;

FIG. 8 is a process sectional view showing the latter half of the manufacturing method according to the third embodiment of the present invention.

FIG. 9 is a diagram showing a relationship between the number of times of flattening processing of micro roughness and an average in-plane roughness.

FIG. 10 is a diagram showing the dielectric breakdown lifetime over time of the MOS capacitors of the present invention and the comparative example.

FIG. 11 is a diagram showing a difference in charge retention characteristics between the present invention and a conventional DRAM.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Semiconductor substrate 3 ... Impurity (metal impurity, organic substance) 4 ... Natural oxide film 5 ... Reaction chamber (processing chamber) 6 ... Heater 7 ... Heat treatment board 8 ... Process gas introduction system 23 ... Gate oxide film 24 ... Polycrystalline semiconductor film 25: sacrificial oxide film 26: organic substance

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-1-226159 (JP, A) JP-A-64-4026 (JP, A) JP-A-2-151031 (JP, A) JP-A-3- 229415 (JP, A) JP-A-5-21459 (JP, A) JP-A-3-129735 (JP, A) JP-A-3-55838 (JP, A) JP-A-3-55840 (JP, A) (58) Field surveyed (Int. Cl. ⁷ , DB name) H01L 21/304 645 H01L 21/3065

Claims (10)

(57) [Claims] 1. A accommodates a plurality of the processed substrate from which the natural oxide film is formed on the surface in one process chamber of a batch type, a plurality
A first step of removing at least one of an organic substance and a metal present in the natural oxide film by dry cleaning in a state where the substrate to be processed is shielded from the outside air; and after the first step, removing the natural oxide film by dry cleaning. a second step of removing by washing, the natural oxide film is removed region third forming an insulating film and a process possess, and from the first step the third
A method for manufacturing a semiconductor device, wherein a series of steps up to the step are continuously performed in the processing chamber . 2. A plurality of substrates to be processed, on which a sacrificial oxide film is formed in advance, are housed in one batch-type processing chamber, and are present in the sacrificial oxide film in a state where the substrates to be processed are shielded from outside air. A first 'step of removing at least one of an organic substance and a metal by dry cleaning, a second' step of removing the sacrificial oxide film by dry cleaning after the first 'step, and removing the sacrificial oxide film. and third forming an insulating film in a region 'possess the steps of, and the first' wherein the step of the
A series of steps up to the step 3 ′ are continuously performed in the processing chamber.
A method of manufacturing a semiconductor device. 3. The method of claim 3, wherein the third step or the third 'step is performed.
And a fourth step of forming a film as an electrode on the insulating film.
Further comprising a step or a 4 ′ step, and the first step
Process or the first 'process to the fourth process or
A series of steps up to the fourth step is linked in the processing chamber.
3. The method according to claim 1 or claim 2, wherein
A method for manufacturing a semiconductor device. 4. The method according to claim 3, wherein the third step or the third 'step is performed.
In the region where the natural oxide film has been removed.
After forming an initial insulating film thinner than the film, the insulating film is formed
The semiconductor device according to claim 1 or 2, wherein
Manufacturing method of body device. 5. A film forming temperature of said initial insulating film is 700 ° C. or less.
Below, the film thickness of the initial insulating film is 1 nm or less.
The method for manufacturing a semiconductor device according to claim 4. 6. The method according to claim 1, wherein said first step or said first 'step is performed.
Dry cleaning is an oxidation with the addition of gas containing halogen atoms.
Characteristic is heat treatment at 600 ° C or less in neutral atmosphere
A method for manufacturing a semiconductor device according to claim 1 or claim 2.
Law. 7. The temperature of the substrate to be processed and the processing chamber
While maintaining the temperature at 200 ° C. or higher, the first step or
From the first 'step to the third step or the third' step
A series of steps in step 1 or 2,
A method for manufacturing a semiconductor device according to claim 2. 8. The processing chamber is provided with a batch type hot
Claims characterized by a single-wall type single processing chamber
3. The method for manufacturing a semiconductor device according to claim 1 or 2. 9. A substrate to be processed having a natural oxide film formed on its surface.
Is housed in a processing chamber, and the substrate to be processed is shut off from the outside air.
In a state where the organic material or metal present in the natural oxide film is at least
A first step of removing one of them by dry cleaning, and after this first step, the natural oxide film is removed by dry cleaning.
A second step of forming an insulating film in a region where the natural oxide film has been removed.
And a third step, and the third Engineering and the first step
A step of flattening the surface of the substrate to be processed.
A method for manufacturing a semiconductor device, comprising: 10. A process in which a sacrificial oxide film is formed on the surface in advance.
The substrate is accommodated in a processing chamber, and the substrate to be processed is shielded from outside air.
In the disconnected state, at least the amount of organic substances and metals existing in the sacrificial oxide film is reduced.
Process and this is also the first 'for removing one by dry cleaning
After the first 'step, the sacrificial oxide film is dry-cleaned.
A second 'step of removing the sacrificial oxide film by removing an insulating film in a region where the sacrificial oxide film has been removed.
3 ′ step , and the first ′ step and the
Between the step 3 ′, the surface of the substrate to be treated is flattened.
Semiconductor device manufacturing method characterized by having a process
Law.