JPH11162975A - Manufacture of semiconductor device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To remove organic impurities of one of defective causes which fluctuate a characteristic prior to the formation of a gate oxide film by thermal treatment. SOLUTION: In a gate oxide film forming process by thermal treatment, a temperature at the time of putting in a semiconductor substrate into an oxide furnace is set to be within a room temperature to 400 deg.C Temperature rise speed after the semiconductor is put in the furnace is set to be 5 deg.C/min.-10 deg.C/min. When the temperature of the oxide furnace becomes 400 deg. C, after the semiconductor substrate is put in the furnace, the temperature is kept for prescribed time or the oxygen of 1%-5% is introduced to the atmosphere of the oxide furnace.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for manufacturing a semiconductor device, and more particularly to a process for forming an insulating oxide film in a method for manufacturing a semiconductor device.

[0002]

2. Description of the Related Art With the miniaturization of VLSIs, the demand for high cleanliness on the surface of semiconductor substrates has become more and more intense.
For example, in a process before forming a gate oxide film by heat treatment, if metal impurities adhere to the surface of the semiconductor substrate, the electrical characteristics of the semiconductor device are significantly deteriorated. Generally, the concentration of metal contamination on the surface of a semiconductor substrate is 1 × 10 ^{10 at.}
It is said that the level needs to be lower than ms / cm ² . As described above, adhesion of metal impurities to the surface of the semiconductor substrate must be avoided as much as possible, and cleaning of the semiconductor substrate in the manufacturing process is indispensable.

In recent years, it has been found that organic substances existing in the atmosphere in a clean room and organic substances adhering to a jig such as a storage box deteriorate the electrical characteristics of a semiconductor device depending on the kind thereof. However, it is difficult to completely control the attachment of the organic substances present in the atmosphere or jig in the clean room to the surface of the semiconductor substrate, and it is almost inevitable.

In the current situation where the gate oxide film is becoming thinner, it is necessary to reduce not only metal impurities but also organic impurities more than ever. Even a very small amount of organic impurities can cause significant fluctuations in characteristics, such as lowering the withstand voltage of a thinner gate oxide film. Therefore, it has become necessary to control organic substances in a step before forming a gate oxide film.

Conventionally, various techniques have been proposed for removing a cause of a defect prior to a step of forming a gate oxide film by heat treatment. For example, in a method of manufacturing a semiconductor device described in Japanese Patent Application Laid-Open No. 7-176504, first, a semiconductor substrate having a natural oxide film formed on its surface is housed in an oxidation furnace, and the natural oxide film is kept in a state where the semiconductor substrate is isolated from the outside air. Organic substances present on the surface and inside of the substrate are removed by incineration in an atmosphere containing oxygen. Then, after removing the natural oxide film with HF gas, the process proceeds to a gate oxide film forming process. In the case of removing an organic substance and a metal impurity at the same time, a natural oxide film is removed with an HF gas after treating the semiconductor substrate in a temperature range of 400 ° C. or more and 600 ° C. or less in an atmosphere containing a halogen gas and an oxygen gas at the same time. . An insulating film is continuously formed on the thus obtained semiconductor substrate after forming an initial insulating film of about 1 nm or less at a low temperature of 700 ° C. or less. Through these steps, a high-quality gate oxide film is formed on a clean semiconductor substrate surface.

The effect of the atmosphere inserted into the oxidation furnace on the deterioration of the reliability of the gate oxide film due to organic contamination, which is a technique described in p. It reports on the case of removing organic matter from a semiconductor substrate contaminated with a benzene derivative-based organic matter before formation. According to this report, when a semiconductor substrate contaminated with the organic substance is introduced into an oxidation furnace at 800 ° C., the furnace atmosphere is 100% nitrogen and the atmosphere is about 80% nitrogen and about 20% oxygen. As a result, the long-term reliability of the gate oxide film formed on the obtained semiconductor substrate is lower when the treatment is performed in an atmosphere of 100% nitrogen. That is, it is reported that an air-containing furnace containing oxygen is effective for removing organic substances before the step of forming a gate oxide film.

[0007]

However, the above-mentioned prior art has the following problems. JP-A-7-17
According to the technique described in Japanese Patent No. 6504, there is a possibility that organic substances present in the natural oxide film may not be completely removed by incineration in an oxygen atmosphere or a mixed atmosphere of a halogen gas and oxygen. . Although the organic substance itself is decomposed, there is a possibility that molecules decomposed and reduced in mass number are combined with oxygen, halogen, or the like, and reattach to the surface of the semiconductor substrate.

Further, since the treatment is performed in an oxygen atmosphere,
It is also conceivable that an initial oxide film is formed on the substrate surface. In some cases, the formed initial oxide film cannot be completely removed even in the natural oxide film removing step using HF gas performed in the next step. When a gate oxide film is formed on the surface of a semiconductor substrate having such an initial oxide film on the surface,
It is more likely that the interface with the initial oxide film includes a structural transition layer that can be one of the causes of failure.

Further, there is a concern that inorganic molecular species (halogen) may remain on the surface of the semiconductor substrate due to a halogen gas introduced to remove organic substances simultaneously with metal removal.
The residual inorganic molecular species has a capability of selectively capturing and dissolving suspended metal atoms in the atmosphere such as SUS fine particles in the chamber. Therefore, the probability that the semiconductor substrate is contaminated with the floating metal atoms before forming the gate oxide film is increased, and the reliability of the gate oxide film formed thereafter is significantly reduced.

In the technique described in p. 772 of the second volume of the 1997 Preliminary Proceedings of the Japan Society of Applied Physics, it is considered that it is desirable that the gate oxide film enter the oxide film in an air atmosphere. However, the air atmosphere contains trace amounts of organic components and inorganic components in addition to about 80% nitrogen and about 20% oxygen. Further, even in a clean room having a high degree of cleanliness, organic substances are constantly emitted from workers and jigs in the atmosphere. Therefore, the possibility that organic impurities adhere to the surface is extremely high.

Further, even if it is assumed that all of these organic substances are ashed and removed by the heat treatment, the treatment is carried out in an atmosphere containing a large amount of oxygen.
Like the technique described in Japanese Patent No. 6504, there is a high possibility that an initial oxide film is formed on the surface of the semiconductor substrate. Therefore, the film quality of the gate oxide film obtained in the subsequent steps is not uniform, and may include a structural transition layer at the interface of the initial oxide film, which is considered to be one of the causes of the failure.

In the pre-process of forming a gate oxide film in each of the above techniques, a large amount of oxygen is introduced to remove organic substances present on the surface of the semiconductor substrate as described above. In such a heat treatment performed in an atmosphere containing a large amount of oxygen, the decomposition reaction of organic substances is considered to be accelerated, but the probability that a part remains without being decomposed or an oxide film is formed before removal is obtained. Is high. Therefore, in the subsequent gate oxide film forming step, not only the reliability is reduced due to the remaining organic substances as described above, but also the structural transition layer in which the initial oxide film formed by oxygen introduction causes a defect at the interface with the oxide film. To form If this initial oxide film is present, it is difficult to form an extremely thin gate oxide film.

An object of the present invention is to provide a method of manufacturing a semiconductor device capable of removing an organic impurity which is one of the factors causing a change in characteristics before forming a gate oxide film by heat treatment. It is in.

[0014]

In order to solve the above-mentioned problems, a method of manufacturing a semiconductor device according to the present invention is directed to a method of manufacturing a semiconductor device in which an insulating oxide film is formed on the surface of a semiconductor substrate by heat treatment. The temperature at which the semiconductor substrate enters the oxidation furnace is room temperature or higher and lower than 400 ° C.

Further, a method of manufacturing a semiconductor device according to the present invention
The rate of temperature rise after entering the semiconductor substrate is 5 ° C./min. 10 ° C./min. It is characterized by the following.

Further, in the method of manufacturing a semiconductor device according to the present invention, after the temperature of the oxidizing furnace reaches 400 ° C. after entering the semiconductor substrate, the temperature is maintained for a predetermined time.

Further, the method of manufacturing a semiconductor device according to the present invention is characterized in that oxygen of 1% or more and 5% or less is introduced into the atmosphere of the oxidation furnace.

[0018]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a method for manufacturing a semiconductor device according to the present invention will be described below. The method of manufacturing a semiconductor device according to the present invention, when forming a gate oxide film by heat treatment to remove organic impurities on the surface of the semiconductor substrate,
The temperature at which the semiconductor substrate enters the oxidation furnace is set lower than in the past. Specifically, furnace input is performed in a range from room temperature to less than 400 ° C. Here, the room temperature refers to a temperature at which an operator can work comfortably in a clean room, and does not greatly deviate from about several tens of degrees Celsius.

Prior to the step of forming a gate oxide film by heat treatment, the temperature at which a semiconductor substrate is introduced into an oxidation furnace is set at a temperature in the range of room temperature to less than 400 ° C. because of the many decomposition and desorption temperatures of general organic substances. (Corresponding to the boiling point) is less than 400 ° C., which is because it can be sufficiently removed within this temperature range. Table 1 shows the boiling points of phthalic esters as examples of such organic substances. Here, DOP is dioctyl phthalate, and DBP is dibutyl phthalate.

[0020]

[Table 1]

If the organic substance is physically adsorbed on the semiconductor substrate, the boiling point of many organic substances is 4 as described above.
Since it is lower than 00 ° C., it should be sufficiently desorbed in an inert gas (poorly active gas) such as nitrogen at 400 ° C.
However, it is conceivable that the organic substance serving as an impurity is bonded to the semiconductor substrate by weak chemical adsorption. However, the boiling points of the phthalic esters shown in Table 1 are solely those of a single substance. Organic substances such as phthalic acid esters exemplified above have a higher boiling point when physically adsorbed as a single substance when chemically adsorbed on a semiconductor substrate even if they are simulated. The organic substance chemically adsorbed may not be desorbed even when the temperature exceeds about 800 ° C., which is the formation temperature of the gate oxide film.

As described above, in order to remove organic substances bonded by chemical adsorption, it is conceivable to enter a semiconductor substrate into a high-temperature oxidation furnace atmosphere. However, when rapidly entering an oxidation furnace under high-temperature conditions, although decomposition of the chemically adsorbed organic substance is promoted, Si-C bonds and amorphous carbon are formed after decomposition of the organic substance, and the semiconductor substrate and The recombination and chemisorption make it more difficult to remove organic substances on the surface of the semiconductor substrate.

Therefore, in the present invention, as described above, the semiconductor substrate is not introduced into the oxidizing furnace which has been heated to a high temperature from the beginning, but the semiconductor substrate is introduced into the oxidizing furnace within a temperature range from room temperature to less than 400 ° C. Furnace.

After the semiconductor substrate is placed in an oxidizing furnace, the temperature is 750 to 800, which is a normal gate oxide film forming temperature.
In the step of raising the temperature to about ° C., the rate of temperature rise is set lower than that in the conventional gate oxide film forming step. The heating rate was 5 ° C./min. 10 ° C./min. The following is assumed. In this case, the heating rate was 5 ° C./min. Even if it is set to less than an extremely low value, the effect of desorption of organic substances does not change.
Further, if the temperature raising rate is extremely reduced, it takes too much time to reach the gate oxide film forming temperature, which may increase the manufacturing cost of the semiconductor device.

Alternatively, the temperature is maintained at 400 ° C. for a predetermined time. The holding time must be at least 5 minutes or more. This is because if the holding time is too short, there is a high possibility that the physically adsorbed organic matter will not be desorbed satisfactorily as in a normal temperature raising step in which the temperature is not held. Also,
Since the temperature of the semiconductor substrate also reaches later after the temperature of the atmosphere reaches 400 ° C., it is necessary to sufficiently maintain the temperature. In this case, it is desirable to maintain the temperature at 400 ° C., but the same effect can be obtained by maintaining the temperature within the range of 350 ° C. to 450 ° C.

FIG. 1 shows an example of a temperature rise pattern in the method of manufacturing a semiconductor device according to the present invention. FIG. 1 (a) shows that the heating rate after the semiconductor substrate was introduced into the oxidation furnace was 10 ° C./min.
FIG. In addition, FIG. 1B shows that the temperature of the semiconductor substrate was set to 20 ° C./min.
After holding at 400 ° C. for 10 minutes,
° C / min. 5 shows a heating pattern when the temperature is increased by.

Alternatively, it is also possible to combine both of these temperature raising rates and the temperature holding step and incorporate them into the step of raising the temperature to the gate oxide film forming temperature. By slowing the rate of temperature rise or providing a holding time, it is possible to apply moderate heat energy to organic impurities adsorbed on the semiconductor substrate, which causes gentle oxidative decomposition. As a result, it is possible to prevent Si-C bonds and amorphous carbon from being formed and being recombined with the semiconductor substrate and chemically adsorbed, as in the case where the furnace is rapidly entered into the oxidation furnace under the high temperature condition.

Further, a small amount of oxygen is introduced into the atmosphere in the oxidation furnace into which the semiconductor substrate enters. This is to promote removal of the chemically adsorbed organic matter which is difficult to remove. By introducing a trace amount of oxygen into an inert gas such as nitrogen, organic impurities can be effectively removed. In this case, several percent of the amount of oxygen to be introduced is sufficient.

As described above, when the amount of oxygen to be introduced is set to several%, there is an advantage that formation of an initial oxide film is suppressed. In each of the conventional techniques, there was a possibility that an initial oxide film was formed because of a large oxygen content such as an atmosphere in an oxidation furnace being air. However, in the present invention, most of the oxygen is spent for decomposing organic substances adsorbed on the semiconductor substrate by reducing the amount of oxygen to be introduced as compared with the conventional example. As described above, in addition to the furnace input at a low temperature, almost no oxygen used for forming an unnecessary initial oxide film remains, and the formation thereof is suppressed. In this manner, a clean semiconductor substrate from which organic substances have been removed can be obtained, so that a highly reliable insulating film can be formed even when a gate oxide film is formed.

[0030]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS (First Embodiment: Oxygen Introducing Effect) An embodiment of a method of manufacturing a semiconductor device according to the present invention will be described with reference to the drawings. Example 1 In this example, the effect of removing organic impurities when oxygen was introduced into nitrogen, which is an inert gas, was examined. In this embodiment, a phthalic acid ester was used as an organic substance serving as an impurity. First, a phthalic acid ester was forcibly attached to the surface of a semiconductor substrate which had been subjected to acid cleaning or diluted hydrofluoric acid treatment, thereby causing contamination. As a method of this compulsory contamination, a plastic material containing phthalate ester and an organic solvent such as alcohol or ketones are installed in a ventilation box with a built-in chemical filter for removing organic substances in a class 1 clean room. In this case, the semiconductor substrate to be exposed is exposed to a blow box for a predetermined time.

Next, the semiconductor substrate contaminated with the phthalic acid ester was introduced into an oxidation furnace at room temperature. Thereafter, oxygen was introduced into the oxidation furnace to raise the temperature to the gate oxidation temperature. At this time, the heating rate was 20 ° C./min. And The atmosphere at this time was as follows: Example (1): oxygen 1%, nitrogen 99% Example (2): oxygen 5%, nitrogen 95% Comparative example (1): nitrogen 100% (no oxygen introduced).

FIG. 2 shows the structural formulas and mass decomposition patterns of the phthalates. FIG. 2A shows the structural formula and mass decomposition pattern of linear dioctyl phthalate (DOP), and FIG. 2B shows the structural formula and mass decomposition pattern of phthalic anhydride. FIG. 3 shows the structural formula and decomposition points of the branched dioctyl phthalate (DOP). As can be seen from these, when phthalates are adsorbed on the semiconductor substrate, the mass numbers appearing are 149, 121,
104 or the like. Therefore, the amount of phthalic acid ester having a mass number of 104 released at each temperature among the desorbed organic substances was evaluated by atmospheric pressure ionization mass spectrometry. Mass number 10
The evaluation with the phthalate ester of No. 4 is difficult to evaluate because the phthalate esters having a large mass number (149, 121, etc.) decompose at a relatively low temperature during the heating to 104 mass number. On the other hand, a phthalate having a mass number of 104 can be stably detected even at a relatively high temperature.

FIG. 4 shows the amount of phthalate ester having a mass number of 104 released at each temperature. FIG. 4A shows the amount of phthalate ester having a mass number of 104 at each temperature when the semiconductor substrate is contaminated after acid cleaning. The surface of the semiconductor substrate that has been subjected to the acid cleaning treatment has a chemical oxide film. FIG. 4B shows the release amount of the phthalate ester having a mass number of 104 at each temperature when the semiconductor substrate is contaminated after being subjected to diluted hydrofluoric acid treatment. The surface of the semiconductor substrate subjected to the diluted hydrofluoric acid treatment has a hydrogen termination. Comparing FIGS. 4A and 4B, it can be seen that the surface state of the semiconductor substrate does not depend much on the difference between the acid cleaning and the diluted hydrofluoric acid treatment.

As can be seen from the results of both FIGS. 4A and 4B, the nitrogen 10 of Comparative Example (1) (indicated by ■ in the figure)
In the case of the 0% atmosphere, the emission amount of the phthalic acid ester having a mass number of 104 becomes maximum around 500 ° C.
Desorption continues even when the temperature exceeds 800 ° C. On the other hand,
In Example (1) (indicated by □ in the figure) and Example (2) (indicated by ▲ in the figure) in which oxygen was introduced, the release amount of the phthalate ester having a mass number of 104 was larger than that in the case of 100% nitrogen. And has decreased by about one digit. Further, at around 800 ° C., which is close to the temperature at which the gate oxide film is formed, the detection limit is almost reached.

This phenomenon is caused by introducing a small amount of oxygen into the atmosphere as in the embodiments (1) and (2) before raising the temperature to the film formation temperature of the gate oxide film of about 800 ° C. This is because the decomposition of the phthalic acid ester by oxygen has occurred. On the other hand, when oxygen is not introduced as shown in Comparative Example (1), the gate oxide film forming temperature is 80.
This is because organic matter remains up to about 0 ° C.

At a high temperature near the temperature at which the gate oxide film is formed, the amount of phthalate decreases. Also, when comparing the release amount of phthalic acid ester due to the difference in the amount of introduced oxygen between Example (1) and Example (2), no significant difference is observed. From this, it can be said that even if the oxygen introduction amount is increased, the effect of removing the phthalic acid ester is not so different. From this point, it can be understood that, from the viewpoint of suppressing the formation of the unnecessary initial oxide film, it is desirable that the introduction amount is about 1%, which is smaller.

As described above, a semiconductor substrate from which organic substances have been successfully removed can be obtained by introducing a small amount of oxygen at the time of entering the furnace, so that the gate oxide film obtained in the subsequent film forming step by heat treatment has high reliability. Show.

(Second Embodiment: Effect of Lowering the Temperature Rising Speed) Next, another embodiment of the method of manufacturing a semiconductor device according to the present invention will be described with reference to the drawings. In the present example, the effect of removing organic impurities by selecting a slower rate of temperature increase for the difference in the temperature increase to the gate oxide film formation temperature due to the heat treatment was examined. Also in this example, a phthalic acid ester was used as an organic substance serving as an impurity. The method for forcibly contaminating the surface of the semiconductor substrate with a phthalic acid ester in advance was based on the same method as in the first embodiment.

Next, the semiconductor substrate contaminated with the phthalic ester was introduced into an oxidation furnace at room temperature. At this time, the atmosphere was 100% nitrogen, and the heating rate was as follows: Example (3): 10 ° C./min. Comparative Example (2): 20 ° C./min. And

FIG. 5 shows the amount of phthalate ester released at each temperature. FIG. 5A shows the release amount of the phthalic ester having a mass number of 104 at each temperature. As can be seen from the results, in the case of Comparative Example (2) (shown by ◆ in the figure) in which the rate of temperature rise is high, the release amount becomes maximum around 500 ° C., and the release continues even when the temperature exceeds 800 ° C. . On the other hand, the embodiment in which the heating rate is reduced (3) (indicated by ■ in the figure)
In the case of (1), the release amount of the phthalate was lower by about half an order as compared with Comparative Example (2). When the temperature exceeded 700 ° C., the temperature decreased to a level close to the detection limit.

FIG. 5B shows the amount of phthalate ester having a mass number of 149 released at each temperature. The phthalic acid ester having a mass number of 149 is considered to be physically adsorbed, and is obtained in Example (3) (indicated by ■ in the figure) and Comparative Example (2) (indicated by ◆ in the figure) at 400 ° C. or lower, which is close to the boiling point of the phthalic ester. Most of them are released. Mass number 14
The release amount of No. 9 is smaller by about one digit in the comparative example (2) in which the heating rate is fast, as compared with the example (3) in which the heating rate is slow. In the embodiment (3) in which the rate of temperature rise is slow, thermal desorption is performed with physical adsorption because the temperature is raised slowly. On the other hand, in Comparative Example (2) in which the rate of temperature rise is high, excess heat energy is consumed for the transition from physical adsorption to weak chemical adsorption.

In this way, by entering the furnace at a low temperature at the time of entering the furnace and lowering the heating rate, it is possible to obtain a controlled and clean surface of organic substances on the surface of the semiconductor substrate before the gate oxide film is formed. it can. A gate oxide film obtained in a film forming step by a subsequent heat treatment shows high reliability.

(Third Embodiment: Temperature Holding Effect) Next, still another embodiment of the method of manufacturing a semiconductor device according to the present invention will be described with reference to the drawings. In the present embodiment, before the temperature is increased to the temperature at which the gate oxide film is formed by the heat treatment, the temperature is maintained at a temperature lower than the formation temperature for a predetermined time.
The desorption effect of organic impurities was studied. Also in this example, a phthalic acid ester was used as an organic substance serving as an impurity. The method for forcibly contaminating the surface of the semiconductor substrate with a phthalic acid ester in advance was based on the same method as in the first embodiment and the second embodiment.

Next, the semiconductor substrate contaminated with the phthalate ester was introduced into an oxidation furnace at room temperature. At this time, the atmosphere was 100% nitrogen, and the temperature was raised at a rate of 20 ° C./min. And When the temperature in the oxidation furnace reached 400 ° C., the temperature was once stopped, and the temperature was kept constant for 10 minutes. Then again, 20
° C / min. The temperature is increased up to the gate oxide film forming temperature at the temperature increasing speed. The gate oxide film forming temperature varies depending on conditions, but is generally about 750 to 800 ° C.

The semiconductor substrate contaminated with the phthalic acid ester was placed in an oxidation furnace, and the amount of organic substances released when the temperature was raised was measured using a gas chromatograph mass spectrometer.
FIG. 6 shows the results of measurement of the amount of organic substances released when the semiconductor substrate was contaminated after acid cleaning, using a gas chromatograph mass spectrometer. FIG. 6 (a) shows that 400 to 400
The amount of organic substances released in the temperature range up to ° C is shown in FIG.
(B) shows the amounts of organic substances released in a temperature range from 800 ° C. after holding the temperature at 400 ° C. for 10 minutes, respectively. FIG. 7 shows the results of measuring the amount of organic substances released when the semiconductor substrate was contaminated after dilute hydrofluoric acid treatment using a gas chromatograph mass spectrometer. FIG. 7A shows the amount of organic substances released in the temperature range from room temperature to 400 ° C., and FIG.
The amounts of the organic substances released in the temperature range from 800 ° C. after holding the temperature at 10 ° C. for 10 minutes are shown.

A comparison between FIGS. 6 and 7 shows that the amount of organic substances released does not depend much on the surface state of the semiconductor substrate based on the difference between acid cleaning and dilute hydrofluoric acid treatment. In addition, in FIGS. 6A and 7A, which are the results of the amount of release from room temperature to 400 ° C., the presence of a large number of organic substances containing phthalic anhydride is confirmed. On the other hand, as can be seen from FIGS. 6 (b) and 7 (b), which are the results after holding the temperature at 400 ° C. for 10 minutes, the peak of the organic substance containing phthalic anhydride becomes small, and most of the organic substance is thermally decomposed. Indicates that they are desorbed.

In these results, the ratio of the amount of organic substances released at a temperature rise to 800 ° C. to the amount of organic substances released up to 400 ° C. is based on phthalic anhydride,
It is 3.5% in the example after the acid cleaning shown in FIG. 6 and 5% in the example after the dilute hydrofluoric acid treatment shown in FIG.

As described above, by keeping the temperature at about 400 ° C. for a certain period of time before raising the temperature to the gate oxide film forming temperature, the organic substance on the semiconductor substrate surface can be controlled to have a clean surface. . A gate oxide film obtained in a film forming step by a subsequent heat treatment shows high reliability.

In the above three embodiments, in the method of manufacturing a semiconductor device according to the present invention, a method of changing a temperature rising pattern of an oxidation furnace before a gate oxide film forming step in order to remove organic substances attached to a semiconductor substrate, Alternatively, a method of mixing a small amount of oxygen into the atmosphere introduced into the oxidation furnace has been individually described. However, any two of the methods shown in these embodiments, or a combination of all three methods, can be employed in the temperature raising step before the gate oxide film forming step. By the combination, the organic substances can be more effectively desorbed from the semiconductor substrate.

In the above three examples, phthalic acid esters were used as the organic substances forcibly contaminating the semiconductor substrate.
On the other hand, the organic substances that actually adhere are not limited to these phthalates. However, as described above, in the temperature raising step up to the gate oxide film forming temperature, other general organic substances also behave similarly to the phthalic esters described in the examples of the present invention. An organic substance adsorbed on a semiconductor substrate can be favorably desorbed by a method for manufacturing a semiconductor device.

[0051]

As described above, the present invention has the following excellent effects. According to the method of manufacturing a semiconductor device of the present invention, an organic substance which causes a defect can be eliminated from a semiconductor substrate, and an insulating film such as a gate oxide film formed on the semiconductor substrate can be made of high quality. This facilitates the manufacture of a high-performance semiconductor device.

[Brief description of the drawings]

FIG. 1 is a diagram showing an example of a temperature rise pattern in a method of manufacturing a semiconductor device according to the present invention.

FIG. 2 is a view showing the structural formulas and mass decomposition patterns of phthalic esters.

FIG. 3 is a diagram showing the structural formula and decomposition mass points of branched dioctyl phthalate (DOP).

FIG. 4 is a diagram showing the amount of phthalate ester having a mass number of 104 released at each temperature.

FIG. 5 is a graph showing the amount of phthalate released at each temperature.

FIG. 6 is a view showing the results of measuring the amount of organic substances released when a semiconductor substrate is contaminated after acid cleaning using a gas chromatograph mass spectrometer.

FIG. 7 is a graph showing the results of measuring the amount of released organic substances using a gas chromatograph mass spectrometer when a semiconductor substrate is contaminated after dilute hydrofluoric acid treatment.

Claims (4)

[Claims] In a method of manufacturing a semiconductor device in which an insulating oxide film is formed on a surface of a semiconductor substrate by heat treatment, a temperature at which a semiconductor substrate enters an oxidation furnace during a temperature raising step is equal to or higher than room temperature and lower than 400 ° C. A method for manufacturing a semiconductor device, comprising: 2. A heating rate of the semiconductor substrate after entering the furnace,
5 ° C / min. 10 ° C./min. The method for manufacturing a semiconductor device according to claim 1, wherein: 3. The method for manufacturing a semiconductor device according to claim 1, wherein after the temperature of the oxidation furnace reaches 400 ° C. after entering the semiconductor substrate, the temperature is maintained for a predetermined time. 4. The method for manufacturing a semiconductor device according to claim 1, wherein oxygen of 1% or more and 5% or less is introduced into the atmosphere of the oxidation furnace.