JP3681525B2 - Manufacturing method of semiconductor device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a semiconductor device having a MIS (Metal Insulator Semiconductor) structure having a semiconductor layer, an insulating film, and a conductive film sequentially formed in the vertical direction, and a method for manufacturing the same.
[0002]
[Prior art]
FIG. 19 shows a cross-sectional structure of a conventional MIS structure. For example, as shown in FIG. ^- A semiconductor substrate 1 made of silicon is formed with element isolation regions (not shown) formed by pyrogenic oxidation of the semiconductor substrate 1 at a high temperature of about 1000 ° C., and the element isolation regions are spaced from each other. , N to be source / drain ⁺ A high concentration impurity region 2 of the type is formed. A gate insulating film 3 is formed between the high-concentration impurity regions 2 on the semiconductor substrate 1, and a gate electrode made of, for example, polycrystalline silicon doped with impurities at a high concentration is formed on the gate insulating film 3. 4 is formed.
[0003]
In the transistor having the MIS structure, when a voltage is applied to the gate electrode 4 in the accumulation direction while the semiconductor substrate 1 is grounded, and the applied voltage is increased, an FN (Fowler Nordordin) tunnel current is applied to the gate insulating film 3. Flows. When an FN tunnel current of a certain current density or more flows through the gate insulating film 3, a hole trap is generated in the initial stage and a rapid voltage drop is observed. Thereafter, the applied voltage is increased as current injection continues. Rise gradually. This indicates that electron traps are generated in the gate insulating film 3 by application of the FN tunnel current. Due to the occurrence of such traps, the insulating properties of the gate insulating film 3 deteriorate. Since a significant increase in the interface state density is observed after the injection of the FN tunnel current, traps are generated by dangling bonds and broken bonds existing near the interface between the gate insulating film 3 and the semiconductor substrate 1 at the electron trap site. This is considered to be one factor.
[0004]
By the way, as the gate insulating film 3 is made thinner, the electric field applied to the gate insulating film 3 is further increased, and accordingly, traps generated inside the gate insulating film 3 and at the interface with the semiconductor substrate 1 are also increased. Therefore, there is a first problem that the deterioration of the insulating property of the gate insulating film 3 proceeds rapidly.
[0005]
Normally, the gate electrode 4 is made of a polysilicon film doped with an impurity. However, when an impurity having a large diffusion coefficient, such as boron, is doped into the polysilicon film, the impurity is gate-insulated in a subsequent heat treatment step. There is a second problem that it diffuses into the semiconductor substrate 1 through the film 3 and adversely affects the characteristics of the transistor.
[0006]
Therefore, for example, as shown in USP 5,237,188 or USP 5,489,542, a semiconductor device in which nitrogen atoms are introduced into the gate insulating film 3 has been proposed. As described above, when nitrogen atoms are introduced into the gate insulating film 3, the introduced nitrogen atoms are strongly bonded to silicon dangling bonds and broken bonds existing near the interface between the gate insulating film 3 and the semiconductor substrate 1. Therefore, dangling bonds and broken bonds that become trap sites are effectively reduced, so that there is an effect of suppressing the generation of traps due to the application of the FN tunnel current, and the introduced nitrogen atoms are added to the gate electrode 4. It also has an effect of suppressing the diffusion of the implanted impurities into the semiconductor substrate 1.
[0007]
[Problems to be solved by the invention]
However, miniaturization and high integration of semiconductor integrated circuit devices are rapidly progressing, and accordingly, the gate insulating film in the MIS structure is being thinned to a thickness of 10 nm or less. For this reason, the gate insulating film in the conventional MIS structure has been problematic in that it suppresses the generation of traps due to the application of the FN tunnel current and suppresses the diffusion of impurities contained in the gate electrode into the semiconductor substrate.
[0008]
In view of the above, the first object of the present invention is to reliably suppress the generation of traps due to the application of the FN tunnel current in a semiconductor device having a MIS structure having a thinned insulating film. A second object is to reliably suppress diffusion of impurities contained in the conductive film formed in the semiconductor layer into the semiconductor layer.
[0009]
[Means for Solving the Problems]
In order to achieve the above object, the present invention specifies the peak position of the concentration distribution of nitrogen atoms contained in the insulating film and specifies the concentration of nitrogen atoms at the peak of the concentration distribution of nitrogen atoms contained in the insulating film. Is.
[0010]
The manufacturing method of a semiconductor device according to the present invention is based on the manufacturing method of a semiconductor device having a semiconductor layer, an insulating film, and a conductive film that are sequentially formed in the vertical direction. The semiconductor layer is made of silicon and is formed on the semiconductor layer. A step of forming an insulating film; and a step of forming a conductive film on the insulating film. The step of forming the insulating film includes forming an oxide film that forms a base silicon dioxide film on the semiconductor layer. NO gas and O 2 with respect to the silicon dioxide film after the process and the oxide film forming process ₂ By performing a heat treatment in an atmosphere of a mixed gas with a gas and performing an oxidation process and a nitridation process on the silicon dioxide film in parallel, the concentration distribution of nitrogen atoms in the vicinity of the interface on the semiconductor layer side in the silicon dioxide film is increased. Formation of an oxynitride film in which a peak is formed, and a silicon oxynitride film having a nitrogen atom concentration in the range of 1.5 atomic% to 5 atomic% is formed, and the semiconductor layer is also oxynitrided The step of forming a conductive film includes a step of forming a conductive film made of polycrystalline silicon doped with impurities at a high concentration after the oxynitride film forming step.
[0011]
According to the method for manufacturing a semiconductor device described above, the step of forming the insulating film includes the steps of forming NO gas and O2 on the silicon dioxide film formed on the semiconductor layer. ₂ By performing a heat treatment in an atmosphere of a mixed gas with a gas, a silicon oxynitride film in which a peak of the concentration distribution of nitrogen atoms is formed in the vicinity of the interface on the semiconductor layer side in the silicon dioxide film can be reliably formed. .
[0012]
In the semiconductor device manufacturing method described above, the oxidizing atmosphere containing nitrogen in the oxynitride film forming step includes NO gas and O ₂ In an atmosphere of a mixed gas with a gas, the amount of nitrogen atoms introduced in the vicinity of the interface on the semiconductor layer side of the silicon oxynitride film is the amount of increase in the thickness of the insulating film by the heat treatment in the oxynitride film formation step Is almost proportional to
[0013]
In the semiconductor device manufacturing method, the heat treatment in the oxynitride film forming step is preferably performed under high pressure.
[0014]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, a cross-sectional structure of a semiconductor device common to the semiconductor devices according to each embodiment or each reference embodiment of the present invention will be described with reference to FIG.
[0015]
As shown in FIG. ^- A semiconductor substrate 10 made of silicon of type N is used as a source / drain with a space between each other. ⁺ A high-concentration impurity region 11 of a type is formed, and between the high-concentration impurity regions 11 on the semiconductor substrate 10, a gate insulating film 12 made of a silicon oxynitride film and having a thickness of, for example, 5 nm is formed. On the gate insulating film 12, a gate electrode 13 made of polycrystalline silicon doped with an impurity such as boron at a high concentration is formed.
(First embodiment)
The nitrogen concentration profile in the gate insulating film 12 of the semiconductor device according to the first embodiment of the present invention will be described below. The first embodiment achieves the first object of suppressing the generation of traps accompanying the application of the FN tunnel current.
[0016]
FIG. 2 shows a concentration profile of nitrogen atoms in the gate insulating film 12 of the first embodiment. In FIG. 2, the horizontal axis is the interface between the gate electrode 13 side of the gate insulating film 12 and the semiconductor substrate 10. The distance in the depth direction is shown, and the vertical axis shows the concentration profile of nitrogen atoms contained in the gate insulating film 12 and the semiconductor substrate 10.
[0017]
As shown in FIG. 2, in the first embodiment, the peak position of the concentration profile of nitrogen atoms is in the vicinity of the interface on the semiconductor substrate 10 side in the gate insulating film 12, and the nitrogen atom concentration at the peak position of the concentration profile is The concentration is about 3 atomic percent.
[0018]
Since the peak position of the concentration profile of the nitrogen atom is in the vicinity of the interface on the semiconductor substrate 10 side in the gate insulating film 12, the nitrogen atom is in the vicinity of the interface between the gate insulating film 12 and the semiconductor substrate 10. Since it is bonded to the bond, trapping in the vicinity of the interface between the gate insulating film 12 and the semiconductor substrate 10 is suppressed.
[0019]
The concentration of nitrogen atoms at the peak position of the concentration profile of nitrogen atoms is about 3 atom% in the first embodiment, but is preferably in the range of 1.5 atom% to 5 atom%. The reason is as follows. That is, the effect of reducing dangling bonds and broken bonds by introducing nitrogen atoms occurs when the dangling bonds and broken bonds are terminated by nitrogen atoms, but the peak value of the concentration profile of nitrogen atoms is 1.5 atomic%. This is because dangling bonds and broken bonds near the interface between the gate insulating film 12 and the semiconductor substrate 10 are completely terminated by nitrogen atoms. In other words, when the peak value of the concentration profile of nitrogen atoms is lower than 1.5 atomic%, dangling bonds and broken bonds are not terminated sufficiently, so that the vicinity of the interface between the gate insulating film 12 and the semiconductor substrate 10 is insufficient. The effect of improving the trap is not fully demonstrated.
[0020]
On the other hand, when the concentration of nitrogen atoms exceeds 5 atomic%, dangling bonds and broke bonds in the vicinity of the interface between the gate insulating film 12 and the semiconductor substrate 10 are completely terminated, but excessive nitrogen atoms, that is, dangling bonds and Because there are nitrogen atoms that do not contribute to the end of the broken bond, and nitrogen atoms that do not contribute to the termination act as positive fixed charges, the amount of flat band voltage shift in the capacitor or the threshold voltage in the transistor increases. is there.
[0021]
In order to suppress the diffusion of impurities such as boron introduced into the gate electrode 13 into the semiconductor substrate 10, the peak value of the concentration profile of nitrogen atoms is preferably as high as possible. However, when the concentration of nitrogen atoms exceeds 5 atomic% A new problem as described above occurs.
[0022]
For the reasons described above, in the first embodiment, the peak position of the nitrogen atom concentration profile is set in the vicinity of the interface of the gate insulating film 12 on the semiconductor substrate 10 side, and the peak position of the nitrogen atom concentration profile is set. The concentration of nitrogen atoms in is set in the range of 1.5 atomic% to 5 atomic%.
(Second reference form)
Hereinafter, the nitrogen concentration profile in the gate insulating film 12 of the semiconductor device according to the second embodiment of the present invention will be described. The second reference mode is a first purpose of reliably suppressing the generation of traps due to the application of the FN tunnel current, and the second purpose of reliably suppressing the diffusion of impurities contained in the gate electrode 13 into the semiconductor substrate 10. To achieve this goal.
[0023]
FIG. 3 shows a concentration profile of nitrogen atoms in the gate insulating film 12 of the second reference embodiment, and in FIG. 3, the horizontal axis extends from the interface on the gate electrode 13 side of the gate insulating film 12 to the semiconductor substrate 10. The distance in the depth direction is shown, and the vertical axis shows the concentration profile of nitrogen atoms contained in the gate insulating film 12 and the semiconductor substrate 10.
[0024]
As shown in FIG. 3, in the second reference embodiment, the peak position of the concentration profile of nitrogen atoms is in the vicinity of the interface on the semiconductor substrate 10 side in the gate insulating film 12 and the interface on the gate electrode 13 side in the gate insulating film 12. And the concentration of nitrogen atoms at the peak position of the concentration profile is about 3 atomic%.
[0025]
Since the peak position of the nitrogen atom concentration profile is in the vicinity of the interface on the semiconductor substrate 10 side in the gate insulating film 12 and in the vicinity of the interface on the gate electrode 13 side, in the vicinity of the interface between the gate insulating film 12 and the semiconductor substrate 10 and the gate insulation. Since nitrogen atoms are bonded to silicon dangling bonds and broken bonds near the interface between the film 12 and the gate electrode 13, traps in the gate insulating film 12 near the respective interfaces between the semiconductor substrate 10 and the gate electrode 13 are trapped. Each can be suppressed.
[0026]
Further, the concentration of nitrogen atoms at the peak position of the concentration profile of nitrogen atoms is about 3 atomic% in the second reference embodiment, but in the vicinity of the interface of the gate insulating film 12 on the semiconductor substrate 10 side and the gate electrode 13. The peak value of the concentration profile of nitrogen atoms in the vicinity of the side interface is preferably in the range of 1.5 atomic% to 5 atomic%, respectively. The reason is the same as in the first embodiment.
[0027]
In the second reference embodiment, the peak of the nitrogen atom concentration profile in the gate insulating film 12 is not only in the vicinity of the interface on the semiconductor substrate 10 side in the gate insulating film 12 but also on the gate electrode 13 side in the gate insulating film 12. Since it is also in the vicinity of the interface, the nitrogen atoms introduced into the gate insulating film 12 prevent the impurity such as boron from diffusing into the semiconductor substrate 10 from the gate electrode 13 through the gate insulating film 12 twice. Therefore, fluctuations in device characteristics can be reliably suppressed.
[0028]
As described above, in the second reference embodiment, the peak positions of the nitrogen atom concentration profile are set in the vicinity of the interface on the semiconductor substrate 10 side and in the vicinity of the interface on the gate electrode 13 side in the gate insulating film 12, respectively. In addition, since the concentration of nitrogen atoms at the peak position of the concentration profile is set to 1.5 atom% to 5 atom% or less, excess nitrogen atoms that do not contribute to the termination of dangling bonds and broken bonds act as positive fixed charges. Thus, the generation of traps due to the application of the FN tunnel current and the impurities contained in the gate electrode 13 to the semiconductor substrate 10 are not caused without increasing the amount of shift of the flat band voltage in the capacitor or the threshold voltage in the transistor. Diffusion can be suppressed more reliably.
(Third reference form)
Hereinafter, the nitrogen concentration profile in the gate insulating film 12 of the semiconductor device according to the third embodiment of the present invention will be described. The third reference mode is a first purpose of reliably suppressing the generation of traps due to the application of the FN tunnel current and a second purpose of reliably suppressing the diffusion of impurities contained in the gate electrode 13 into the semiconductor substrate 10. To achieve this goal.
[0029]
FIG. 4 shows a concentration profile of nitrogen atoms in the gate insulating film 12 of the third embodiment, and in FIG. 4, the horizontal axis extends from the interface on the gate electrode 13 side of the gate insulating film 12 to the semiconductor substrate 10. The distance in the depth direction is shown, and the vertical axis shows the concentration profile of nitrogen atoms contained in the gate insulating film 12 and the semiconductor substrate 10.
[0030]
As shown in FIG. 4, in the third reference embodiment, the peak position of the concentration profile of nitrogen atoms is in the vicinity of the interface on the semiconductor substrate 10 side in the gate insulating film 12 and in the vicinity of the interface on the gate electrode 13 side. The concentration of nitrogen atoms at the peak position of the concentration profile is about 3 atom%, and the concentration at the bottom between both peaks in the concentration profile is about 1 atom%.
[0031]
Also in the third reference embodiment, for the same reason as in the first embodiment, the peak value of the concentration profile of nitrogen atoms in the vicinity of the interface on the semiconductor substrate 10 side in the gate insulating film 12 and in the vicinity of the interface on the gate electrode 13 side. Is preferably in the range of 1.5 atomic% to 5 atomic%.
[0032]
In FIG. 4, the concentration of the bottom nitrogen atom between the peaks in the concentration profile is about 1 atomic%, but the concentration of the bottom nitrogen atom is in the range of 0.1 atomic% to 3 atomic%. It is preferable. In this way, since nitrogen atoms are bonded to silicon dangling bonds and broken bonds in the entire region of the gate insulating film 12, trapping can be further suppressed, and impurities such as boron in the entire region of the gate insulating film 12. Can be prevented from diffusing from the gate electrode 13 through the gate insulating film 12 to the semiconductor electrode 10, so that fluctuations in device characteristics can be more reliably suppressed.
[0033]
It should be noted that the entire region of the gate insulating film 12 is divided into approximately three equal parts in the depth direction, that is, a shallow region on the gate electrode 13 side, a deep region on the semiconductor substrate 10 side, and a shallow region and a deep region. Among the intermediate regions in between, the intermediate region has fewer dangling bonds and broken bonds than the shallow region and the deep region, so the concentration of nitrogen atoms may be lower than the shallow region and the deep region.
[0034]
As described above, in the third reference embodiment, the peak position of the concentration profile of nitrogen atoms is set in the vicinity of the interface on the semiconductor substrate 10 side in the gate insulating film 12 and in the vicinity of the interface on the gate electrode 13 side. The concentration of nitrogen atoms at the peak position of the concentration profile is set within the range of 1.5 atomic% to 5 atomic%, and the concentration of nitrogen atoms at the bottom between both peaks in the concentration profile is 0.1 atomic%. Since it is set within a range of ˜3 atomic%, excessive nitrogen atoms that do not contribute to the termination of dangling bonds and broken bonds act as positive fixed charges, and the shift amount of the flat band voltage in the capacitor or the threshold voltage in the transistor Generation of traps due to the application of the FN tunnel current and the gate electrode 1 It can be more reliably prevented from diffusing into the semiconductor substrate 10 of impurities in the.
(Fourth embodiment)
Hereinafter, as a fourth embodiment of the present invention, a method for manufacturing a semiconductor device according to the first embodiment will be described with reference to FIGS.
[0035]
First, as shown in FIG. 5A, P made of silicon is used. ^- After the element isolation region (LOCOS oxide film) 15 is formed on the semiconductor substrate 10 of the type, the active region surrounded by the element isolation region 15 on the surface of the semiconductor substrate 10 is washed to remove impurities and natural oxide films. FIG. 5B shows a concentration profile of silicon atoms contained in the semiconductor substrate 10 in a state where the element isolation region 15 is formed in the semiconductor substrate 10, and the horizontal axis represents the distance in the depth direction from the surface of the semiconductor substrate 10. Is shown.
[0036]
Next, as shown in FIG. 6A, the semiconductor substrate 10 is subjected to pyrogenic oxidation at 850 ° C. in an oxidizing atmosphere using, for example, an atmospheric furnace, so that the base 4 nm is formed. A silicon dioxide film 16 having a film thickness is formed. FIG. 6B shows a concentration profile of silicon atoms and oxygen atoms contained in the semiconductor substrate 10 in a state where the silicon dioxide film 16 is formed on the semiconductor substrate 10, and the alternate long and short dash line indicates the silicon dioxide film 16 and the semiconductor substrate 10. The interface is shown.
[0037]
Next, as shown in FIG. 7A, the semiconductor substrate 10 is oxidized in an atmosphere containing nitrogen (for example, N ₂ An oxynitride film 17 having a thickness of 5 nm is formed by performing an oxynitriding process at a temperature of 800 to 1150 ° C. in an atmosphere of O gas or NO gas.
[0038]
FIG. 7B shows that N is applied to the semiconductor substrate 10 using an electric furnace at normal pressure. ₂ The concentration profiles of silicon atoms, oxygen atoms, and nitrogen atoms contained in the semiconductor substrate 10 in a state where oxynitriding is performed at a temperature of 1050 ° C. in an O gas atmosphere are shown. In the fourth embodiment, an oxynitride film 17 having a thickness of 5 nm is formed by performing an oxynitriding process after forming a silicon dioxide film 16 having a thickness of 4 nm serving as a base. The peak position of the concentration profile can be formed in the vicinity of the interface of the gate insulating film 12 on the semiconductor substrate 10 side. That is, as shown in FIG. 7B, the peak position of the concentration profile of nitrogen atoms is in the vicinity of the interface on the semiconductor substrate 10 side in the gate insulating film 12, and the concentration of nitrogen atoms at the peak position of the concentration profile is about 2 atomic percent.
[0039]
N ₂ The oxynitriding treatment with O gas has the disadvantages that the film forming speed is slow and the film thickness is not uniform, but N is formed after forming the base silicon dioxide film 16 as in the fourth embodiment. ₂ When the oxynitriding process using O gas is performed, the film thickness formed by the film forming process using the oxynitriding process is small, so that the throughput can be improved while compensating for the disadvantage that the film forming speed is slow. The uniformity of the film thickness of 17 can be improved. The reason is N ₂ N in oxynitriding with O gas ₂ O and NO at high temperatures ₂ And O ₂ And decomposed into O ₂ Since the oxynitride film 17 is formed while simultaneously performing the oxidation treatment with gas and the nitridation treatment with NO gas, it is considered that the uniformity of the film thickness of the oxynitride film 17 is improved.
[0040]
Next, as shown in FIG. 8, after forming the gate electrode 13 on the gate insulating film 12 made of the oxynitride film 17, N-type impurities are implanted using the gate electrode 13 as a mask. N as drain ⁺ When the high concentration impurity region 11 of the mold is formed, the semiconductor device according to the first embodiment is obtained.
[0041]
As described above, according to the fourth embodiment, the peak position of the nitrogen atom concentration profile can be set in the vicinity of the interface of the gate insulating film 12 on the semiconductor substrate 10 side. Since dangling bonds and broken bonds existing in the vicinity of the interface can be reliably terminated with nitrogen atoms, trapping characteristics can be improved.
[0042]
In addition, since the amount of nitrogen atoms introduced in the vicinity of the interface on the semiconductor substrate 10 side in the gate insulating film 12 is substantially proportional to the amount of increase in film thickness due to the oxynitriding treatment, the concentration of nitrogen atoms in the vicinity of the interface can be easily controlled. It is. For example, when the thickness of the oxynitride film formed by oxynitriding is determined, the ratio between the thickness of the silicon dioxide film serving as the base and the thickness of the oxynitride film increased by the oxynitriding By controlling, the amount of nitrogen atoms introduced into the interface can be controlled to some extent. In addition, since the concentration of nitrogen atoms at the interface is not sensitive to process conditions such as the temperature of the oxynitriding treatment, the conditions of the oxynitriding treatment can be determined by taking into account the thermal budget.
[0043]
The step of forming the silicon dioxide film 16 serving as a base by the oxidation treatment and the step of forming the oxynitride film 17 by the oxynitridation treatment are continuously performed in the same electric furnace, so that the oxidation treatment step and the acid treatment are performed. Metal contamination and particle adhesion can be prevented during the nitriding treatment step, and the throughput of the oxynitride film forming step can be improved. For example, by adding an oxynitriding process sequence to a sequence for forming a silicon dioxide film in an electric furnace, a two-stage process can be easily performed.
(5th reference form)
Hereinafter, as a fifth reference embodiment of the present invention, a method for manufacturing a semiconductor device according to the first embodiment will be described with reference to FIGS.
[0044]
First, as shown in FIG. 5A, P made of silicon is used. ^- After forming the element isolation region 15 in the semiconductor substrate 10 of the type, the active region surrounded by the element isolation region 15 on the surface of the semiconductor substrate 10 is washed to remove impurities and natural oxide films.
[0045]
Next, as shown in FIG. 6A, the semiconductor substrate 10 is subjected to dry oxidation in an oxidizing atmosphere using, for example, a high-pressure electric furnace, so that silicon dioxide having a base film thickness of 4 nm is formed. A film 16 is formed.
[0046]
Next, as shown in FIG. 7A, an oxidizing atmosphere containing nitrogen (for example, N) is applied to the semiconductor substrate 10 using, for example, a high-pressure electric furnace. ₂ An oxynitride film 17 having a thickness of 5 nm is formed by performing an oxynitriding process under a pressure of 5 atm or higher and a relatively low temperature of 750 to 850 ° C. in an atmosphere of O gas or NO gas).
[0047]
In the fifth reference embodiment, after forming a silicon dioxide film 16 having a film thickness of 4 nm as a base, an oxynitride film 17 having a film thickness of 5 nm is formed by performing oxynitriding under high pressure. Therefore, the peak position of the concentration profile of nitrogen atoms can be formed in the vicinity of the interface on the semiconductor substrate 10 side in the gate insulating film 12, and the concentration of nitrogen atoms at the peak position of the concentration profile can be set to about 3 atomic%. .
[0048]
Next, as shown in FIG. 8, after forming the gate electrode 13 on the gate insulating film 12 made of the oxynitride film 17, N-type impurities are implanted using the gate electrode 13 as a mask. N as drain ⁺ When the high concentration impurity region 11 of the mold is formed, the semiconductor device according to the first embodiment is obtained.
[0049]
According to the fifth reference embodiment, since oxynitriding is performed under high pressure, nitrogen atoms are contained in a relatively high concentration throughout the oxynitride film 17, so that trap generation is reliably suppressed. In addition, the effect of suppressing diffusion of impurities contained in the gate electrode 13 into the semiconductor substrate 10 is improved as compared with the semiconductor device obtained by the fourth embodiment.
[0050]
In the fourth embodiment, oxynitridation was performed in an electric furnace at normal pressure, and oxynitridation was performed in a high-pressure electric furnace in the fifth reference embodiment. Instead, silicon dioxide serving as a base was used. An oxidizing atmosphere containing nitrogen (for example, N) is applied to the film 16 using an RTP (Rapid Thermal Process) device such as a light irradiation heating device. ₂ An oxynitride film 17 may be formed by performing an oxynitriding process in an atmosphere of O gas or NO gas), or an RTP apparatus having a shower head and a substrate rotation mechanism for the silicon dioxide film 16 serving as a base An oxidizing atmosphere containing nitrogen (for example, N ₂ The oxynitride film 17 may be formed by performing oxynitriding in an O gas atmosphere. According to the latter, N ₂ Since O gas can be introduced uniformly, the film thickness uniformity of the oxynitride film 17 is further improved.
[0051]
As the silicon dioxide film 16 serving as a base, a thermal oxide film by thermal oxidation by a general electric furnace or rapid thermal oxidation by an RTP apparatus, a deposited film by low pressure CVD, or the like can be used.
(Sixth reference form)
Hereinafter, as a sixth reference embodiment of the present invention, a method for manufacturing a semiconductor device according to the first embodiment will be described with reference to FIGS.
[0052]
First, as shown in FIG. 9A, P made of silicon is used. ^- After forming the element isolation region 15 in the semiconductor substrate 10 of the type, the active region surrounded by the element isolation region 15 on the surface of the semiconductor substrate 10 is washed to remove impurities and natural oxide films. FIG. 9B shows a concentration profile of silicon atoms contained in the semiconductor substrate 10 in a state where the element isolation region 15 is formed on the semiconductor substrate 10, and the horizontal axis represents the distance in the depth direction from the surface of the semiconductor substrate 10. Is shown.
[0053]
Next, as shown in FIG. 10A, an oxidizing atmosphere containing nitrogen (for example, N) is applied to the semiconductor substrate 10 using an RTP apparatus, such as a light irradiation heating apparatus. ₂ O gas atmosphere or NO and O ₂ The oxynitride film 17 having a thickness of 5 nm is formed by performing an oxynitriding process at a temperature of 1000 ° C. or lower in a mixed gas atmosphere).
[0054]
N ₂ When oxynitriding is performed using O gas, N ₂ O and NO at high temperatures ₂ And O ₂ Since it decomposes into ₂ Oxidation with gas and nitridation with NO gas are performed simultaneously. However, N ₂ Since the O gas decomposition reaction does not proceed rapidly, the film thickness uniformity of the oxynitride film 17 is not good. ₂ It is necessary to devise such that the O gas reaches the surface of the semiconductor substrate 10 uniformly. In a normal resistance heating furnace, N ₂ In addition, it is difficult to uniformly introduce O gas, and the oxynitridation reaction is difficult to proceed. Therefore, N ₂ In the case of using O gas, an RTP apparatus equipped with a shower head is used, and a rotation mechanism is provided on the semiconductor substrate 10, so that N is formed on the semiconductor substrate 10. ₂ It is preferable to improve the uniformity of the thickness of the oxynitride film 17 by introducing O gas uniformly.
[0055]
NO and O ₂ In the case of performing oxynitriding using a mixed gas of, for example, 5 vol% NO gas and 95 vol% O ₂ Oxynitriding treatment can be performed at a temperature of 1000 ° C. or lower using a gas mixture with gas. In this way, N ₂ O and NO at high temperatures ₂ And O ₂ Therefore, the temperature of the oxynitriding treatment can be set low and the time for the decomposition reaction can be reduced.
[0056]
N ₂ O gas atmosphere or NO and O ₂ In any of the mixed gas atmospheres, the thermal budget can be reduced by performing the oxynitriding treatment at a temperature of 1000 ° C. or lower.
[0057]
FIG. 10B shows a case where N is applied using a light irradiation heating device. ₂ The concentration profile of silicon atoms, oxygen atoms, and nitrogen atoms contained in the semiconductor substrate 10 when the oxynitride film 17 is formed by performing oxynitridation treatment in an atmosphere of O gas is shown, and the peak of the concentration profile of nitrogen atoms is shown. The position can be formed in the vicinity of the interface of the gate insulating film 12 on the semiconductor substrate 10 side, and the concentration of nitrogen atoms at the peak position of the concentration profile can be set to about 2 atomic%.
[0058]
Next, as in the fourth embodiment, after forming the gate electrode 13 on the gate insulating film 12 made of the oxynitride film 17, an N-type impurity is implanted using the gate electrode 13 as a mask. N to be source / drain ⁺ When the high concentration impurity region 11 of the mold is formed, the semiconductor device according to the first embodiment is obtained.
[0059]
According to the sixth reference embodiment, the semiconductor substrate 10 is subjected to an oxynitriding process in an oxidizing atmosphere containing nitrogen using a light irradiation heating device, so that the film thickness uniformity of the oxynitride film 17 is improved and the nitrogen is improved. The peak position of the atomic concentration profile can be reliably formed in the vicinity of the interface on the semiconductor substrate 10 side in the gate insulating film 12.
(Seventh reference form)
Hereinafter, as a seventh reference embodiment of the present invention, a method for manufacturing a semiconductor device according to the first embodiment will be described with reference to FIGS.
[0060]
First, as shown in FIG. 9A, P made of silicon is used. ^- After forming the element isolation region 15 in the semiconductor substrate 10 of the type, the active region surrounded by the element isolation region 15 on the surface of the semiconductor substrate 10 is washed to remove impurities and natural oxide films.
[0061]
Next, as shown in FIG. 10A, an oxidizing atmosphere containing nitrogen (for example, N) is applied to the semiconductor substrate 10 using a high-pressure electric furnace. ₂ O gas or NO and O ₂ The oxynitride film 17 having a thickness of 5 nm is formed by performing oxynitridation under a pressure of 5 atm or higher and a relatively low temperature of 750 to 850 ° C. in a mixed gas atmosphere).
[0062]
By the way, N ₂ When oxynitriding is performed using O gas, N ₂ O gas is NO and N ₂ And O ₂ However, there is a drawback that the reaction rate is slow if not treated at high temperature, but recently there is a demand for further reduction of the thermal budget (thermal history). Long processing is difficult. Therefore, the treatment temperature and the treatment time can be reduced by performing the oxynitriding treatment at a high pressure of about 25 atm. For example, N ₂ When processing is performed using O gas at a pressure of 25 atm, the oxynitride film 17 can be formed at a relatively low temperature of about 750 to 850 ° C.
[0063]
NO and O ₂ In the case of performing oxynitriding using a mixed gas of, for example, 5 vol% NO gas and 95 vol% O ₂ Oxynitriding treatment can be performed at a temperature of 1000 ° C. or lower using a gas mixture with gas. In this way, N ₂ O and NO at high temperatures ₂ And O ₂ Therefore, the temperature of the oxynitriding treatment can be set low and the time for the decomposition reaction can be reduced.
[0064]
Next, as in the fourth embodiment, after forming the gate electrode 13 on the gate insulating film 12 made of the oxynitride film 17, an N-type impurity is implanted using the gate electrode 13 as a mask. N to be source / drain ⁺ When the high concentration impurity region 11 of the mold is formed, the semiconductor device according to the first embodiment is obtained.
[0065]
According to the seventh embodiment, the peak position of the nitrogen atom concentration profile is gated in order to form the oxynitride film 17 having a thickness of 5 nm by subjecting the semiconductor substrate 10 to oxynitridation under high pressure. The insulating film 12 can be formed in the vicinity of the interface on the semiconductor substrate 10 side, and the concentration of nitrogen atoms at the peak position of the concentration profile can be set to about 3 atomic%.
(Eighth reference form)
Hereinafter, as an eighth reference embodiment of the present invention, a method for manufacturing a semiconductor device according to the second reference embodiment will be described with reference to FIGS.
[0066]
First, as shown in FIG. 11A, P made of silicon is used. ^- After forming the element isolation region 15 in the semiconductor substrate 10 of the type, the active region surrounded by the element isolation region 15 on the surface of the semiconductor substrate 10 is washed to remove impurities and natural oxide films. FIG. 11B shows a concentration profile of silicon atoms contained in the semiconductor substrate 10 in a state where the element isolation region 15 is formed in the semiconductor substrate 10, and the horizontal axis represents the distance in the depth direction from the surface of the semiconductor substrate 10. Is shown.
[0067]
Next, as shown in FIG. 12A, the base substrate is formed by subjecting the semiconductor substrate 10 to pyrogenic oxidation in an oxidizing atmosphere using, for example, a rapid thermal oxidation method (RTO method) by lamp heating. A silicon dioxide film 16 having a thickness of 4 nm is formed. FIG. 12B shows a concentration profile of silicon atoms and oxygen atoms contained in the semiconductor substrate 10 in a state where the silicon dioxide film 16 is formed on the semiconductor substrate 10, and the alternate long and short dash line indicates the silicon dioxide film 16 and the semiconductor substrate 10. The interface is shown.
[0068]
Next, laughing gas (N ₂ As shown in FIG. 13A, the first nitridation process (RTN process) is performed on the semiconductor substrate 10 in the laughing gas at a temperature of, for example, 1000 ° C. for 30 seconds. Then, a previous oxynitride film 17 having a thickness of 5 nm is formed.
[0069]
FIG. 13B shows the concentration profile of silicon atoms, oxygen atoms, and nitrogen atoms contained in the semiconductor substrate 10 in a state where the previous stage oxynitride film 17 is formed on the semiconductor substrate 10, and the concentration profile of nitrogen atoms. In the vicinity of the interface of the gate insulating film 12 on the semiconductor substrate 10 side, and the concentration of nitrogen atoms at the peak position of the concentration profile is about 2 atomic%.
[0070]
Next, the introduced gas is switched to nitrous oxide gas (NO gas) in the same chamber, and the semiconductor substrate 10 is subjected to, for example, rapid thermal oxidation (RTO method) by lamp heating in nitrous oxide gas. By performing a second nitriding process (RTN process) for 10 seconds at a temperature of 850 ° C., a final oxynitride film 18 having a thickness of 5 nm is formed as shown in FIG.
[0071]
FIG. 14B shows the concentration profile of silicon atoms, oxygen atoms, and nitrogen atoms contained in the semiconductor substrate 10 in a state where the final oxynitride film 18 is formed on the semiconductor substrate 10. The peak position is not only near the interface of the gate insulating film 12 on the semiconductor substrate 10 side, but also near the interface of the gate insulating film 12 on the gate electrode 13 side, and the concentration of nitrogen atoms at each peak position of the concentration profile. Is about 2 atomic percent.
[0072]
Next, as in the fourth embodiment, after forming the gate electrode 13 on the gate insulating film 12 made of the oxynitride film 17, an N-type impurity is implanted using the gate electrode 13 as a mask. N to be source / drain ⁺ When the high concentration impurity region 11 of the type is formed, the semiconductor device according to the second embodiment is obtained.
[0073]
According to the eighth embodiment, after the silicon dioxide film 16 as the base is formed, the first nitriding treatment in the laughing gas and the second nitriding treatment in the nitrous oxide gas are performed. The peak of the nitrogen atom concentration profile at 12 can be both near the interface on the semiconductor substrate 10 side and near the interface on the gate electrode 13 side.
[0074]
In the eighth reference embodiment, the silicon dioxide film 16 serving as the base is formed by the RTO method, but instead of this, a deposited oxide film such as a conventional thermal oxide film, HTO film, or TEOS film may be used. Needless to say, similar results can be obtained.
[0075]
Further, the semiconductor substrate 10 is directly heat-treated in the laughing gas or nitrous oxide gas without forming the base silicon dioxide film 16, so that the interface of the gate insulating film 12 on the semiconductor substrate 10 side is treated. A peak of the concentration profile of nitrogen atoms may be formed in the vicinity.
(Ninth Reference Form)
Hereinafter, as a ninth reference embodiment of the present invention, a method for manufacturing a semiconductor device according to the third reference embodiment will be described with reference to FIGS.
[0076]
First, as shown in FIG. 15A, P made of silicon is used. ^- After forming the element isolation region 15 in the semiconductor substrate 10 of the type, the active region surrounded by the element isolation region 15 on the surface of the semiconductor substrate 10 is washed to remove impurities and natural oxide films. FIG. 15B shows a concentration profile of silicon atoms contained in the semiconductor substrate 10 in a state where the element isolation region 15 is formed in the semiconductor substrate 10, and the horizontal axis represents the distance in the depth direction from the surface of the semiconductor substrate 10. Is shown.
[0077]
Next, as shown in FIG. 16A, the semiconductor substrate 10 is subjected to pyrogenic oxidation at 850 ° C. in an oxidizing atmosphere using, for example, an atmospheric furnace, so that the base 4 nm is formed. A silicon dioxide film 16 having a film thickness is formed. FIG. 16B shows a concentration profile of silicon atoms and oxygen atoms contained in the semiconductor substrate 10 in a state where the silicon dioxide film 16 is formed on the semiconductor substrate 10, and the alternate long and short dash line indicates the silicon dioxide film 16 and the semiconductor substrate 10. The interface is shown.
[0078]
Next, by performing a first nitriding treatment (RTN treatment) for 20 minutes at a high pressure of 25 atm and a temperature of 800 ° C. in a laughing gas atmosphere, as shown in FIG. A pre-stage oxynitride film 17 having a thickness of 5 nm is formed.
[0079]
FIG. 17B shows a concentration profile of silicon atoms, oxygen atoms, and nitrogen atoms contained in the semiconductor substrate 10 in a state where the previous-stage oxynitride film 17 is formed on the semiconductor substrate 10, and the concentration profile of the nitrogen atoms. In the vicinity of the interface of the gate insulating film 12 on the semiconductor substrate 10 side, and the concentration of nitrogen atoms at the peak position of the concentration profile is about 3 atomic%.
[0080]
Next, a second nitriding treatment (RTN treatment) is performed on the semiconductor substrate 10 in a nitrous oxide gas at a temperature of, for example, 850 ° C. for 10 seconds using a rapid thermal processing apparatus (RTP apparatus) having an irradiation lamp. As a result, a final oxynitride film 18 having a thickness of 5 nm is formed as shown in FIG.
[0081]
FIG. 18B shows the concentration profile of silicon atoms, oxygen atoms, and nitrogen atoms contained in the semiconductor substrate 10 in a state where the final oxynitride film 18 is formed on the semiconductor substrate 10. The peak position is not only near the interface of the gate insulating film 12 on the semiconductor substrate 10 side, but also near the interface of the gate insulating film 12 on the gate electrode 13 side, and the concentration of nitrogen atoms at each peak position of the concentration profile. Is about 3 atomic percent.
[0082]
Next, as in the fourth embodiment, after forming the gate electrode 13 on the gate insulating film 12 made of the oxynitride film 17, an N-type impurity is implanted using the gate electrode 13 as a mask. N to be source / drain ⁺ When the type high concentration impurity region 11 is formed, the semiconductor device according to the third embodiment is obtained.
[0083]
According to the ninth embodiment, the nitriding process is performed on the semiconductor substrate 10 under a high pressure of 25 atm to form the oxynitride film 17 having a thickness of 5 nm. Can be set to about 3 atomic%, and the concentration of nitrogen atoms at the bottom between both peaks of the concentration profile can be set high.
[0084]
Similarly to the eighth embodiment, after the silicon dioxide film 16 serving as the base is formed, the first nitriding treatment in the laughing gas and the second nitriding treatment in the nitrous oxide gas are performed. The peak of the nitrogen atom concentration profile in the insulating film 12 can be both near the interface on the semiconductor substrate 10 side and near the interface on the gate electrode 13 side.
[0085]
In the ninth embodiment, the silicon dioxide film 16 serving as the base is formed by the RTO method. However, instead of this, a deposited oxide film may be used, or the silicon dioxide film 16 serving as the base may be formed. Without forming, the semiconductor substrate 10 is directly heat-treated in laughing gas or nitrous oxide gas, and a peak of the nitrogen atom concentration profile is formed in the vicinity of the interface of the gate insulating film 12 on the semiconductor substrate 10 side. It may be formed.
[0086]
【The invention's effect】
According to the method for manufacturing a semiconductor device of the present invention, a silicon oxynitride film in which a peak of the concentration distribution of nitrogen atoms is formed in the vicinity of the interface on the semiconductor layer side in the silicon dioxide film can be reliably formed. The first semiconductor device that can suppress the generation of traps in the vicinity of the interface between the insulating film and the semiconductor layer can be reliably manufactured.
[0087]
According to the first semiconductor device, since nitrogen atoms are bonded to dangling bonds or broken bonds of silicon in the vicinity of the interface between the insulating film and the semiconductor layer, an FN tunnel current is applied in the vicinity of the interface between the insulating film and the semiconductor layer. Since the generation of traps associated with the above can be suppressed, deterioration of the insulating film can be reliably prevented.
[0088]
In the first semiconductor device, when the nitrogen atom concentration at the peak of the nitrogen atom concentration distribution is 1.5 atomic% or more and 5 atomic% or less, the nitrogen atom reliably terminates the dangling bond or the broken bond. Therefore, it is possible to reliably suppress the generation of traps near the interface between the insulating film and the semiconductor layer, and excessive nitrogen atoms that do not contribute to the termination of dangling bonds and broken bonds become positive fixed charges in the capacitor. The shift amount of the flat band voltage or the threshold voltage of the transistor can be prevented from increasing.
[0089]
In the semiconductor device manufacturing method described above, the oxidizing atmosphere containing nitrogen in the oxynitride film forming step includes NO gas and O ₂ In the mixed gas atmosphere with gas, nitriding action by NO gas, and O ₂ Since the oxidizing action by the gas proceeds simultaneously, the silicon oxynitride film can be reliably grown.
[0090]
According to the above method for manufacturing a semiconductor device, the amount of nitrogen atoms introduced in the vicinity of the interface on the semiconductor layer side in the silicon oxynitride film is the increase in the thickness of the insulating film due to the heat treatment in the oxynitride film formation step. Since it is almost proportional, it is easy to control the concentration of nitrogen atoms in the vicinity of the interface.
[0091]
In the semiconductor device manufacturing method described above, when the heat treatment in the oxynitride film forming step is performed under high pressure, the amount of nitrogen atoms contained in the silicon dioxide film can be reliably increased.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view of a semiconductor device common to each embodiment or each reference embodiment of the present invention.
FIG. 2 is a view showing a nitrogen concentration distribution in a gate insulating film of the semiconductor device according to the first embodiment of the present invention.
FIG. 3 is a view showing a nitrogen concentration distribution in a gate insulating film of a semiconductor device according to a second embodiment of the present invention.
FIG. 4 is a view showing a nitrogen concentration distribution in a gate insulating film of a semiconductor device according to a third embodiment of the present invention.
5A is a cross-sectional view showing an element isolation region forming step in a method for manufacturing a semiconductor device according to a fourth embodiment or a fifth reference embodiment of the present invention, and FIG. 5B is a fourth embodiment. It is a figure which shows the density | concentration profile of the silicon atom contained in the semiconductor substrate in the state in which the element isolation region was formed in the form.
6A is a cross-sectional view showing a silicon dioxide film forming step in a method of manufacturing a semiconductor device according to a fourth embodiment or a fifth reference embodiment of the present invention, and FIG. 6B is a fourth embodiment. It is a figure which shows the concentration profile of the silicon atom and oxygen atom which are contained in the semiconductor substrate in the state in which the silicon dioxide film was formed in the form.
7A is a cross-sectional view showing an oxynitride film forming step in a method for manufacturing a semiconductor device according to a fourth embodiment or a fifth reference embodiment of the present invention, and FIG. 7B is a fourth embodiment. It is a figure which shows the concentration profile of the silicon atom, oxygen atom, and nitrogen atom which are contained in the semiconductor substrate in the state in which the oxynitride film was formed in the form.
FIG. 8 is a cross-sectional view showing a gate electrode forming step in a method for manufacturing a semiconductor device according to a fourth embodiment or a fifth reference embodiment of the present invention.
9A is a cross-sectional view showing an element isolation region forming step in a method for manufacturing a semiconductor device according to a sixth or seventh reference embodiment of the present invention, and FIG. 9B is an element view in the sixth reference embodiment; It is a figure which shows the density | concentration profile of the silicon atom contained in the semiconductor substrate in the state in which the isolation region was formed.
10A is a cross-sectional view showing an oxynitride film forming step in a method for manufacturing a semiconductor device according to a sixth or seventh reference embodiment of the present invention, and FIG. 10B is an acid diagram in the sixth reference embodiment. It is a figure which shows the concentration profile of the silicon atom, oxygen atom, and nitrogen atom which are contained in the semiconductor substrate in the state in which the nitride film was formed.
11A is a cross-sectional view showing an element isolation region forming step in a method for manufacturing a semiconductor device according to an eighth reference embodiment of the present invention, and FIG. 11B is an element isolation region in the eighth reference embodiment; It is a figure which shows the density | concentration profile of the silicon atom contained in the semiconductor substrate in the formed state.
12A is a cross-sectional view showing a silicon dioxide film forming step in a method for manufacturing a semiconductor device according to an eighth embodiment of the present invention, and FIG. 12B is a diagram showing a silicon dioxide film formed in the eighth embodiment. It is a figure which shows the concentration profile of the silicon atom and oxygen atom which are contained in the semiconductor substrate in the formed state.
13A is a cross-sectional view showing a previous step of forming an oxynitride film in a method for manufacturing a semiconductor device according to an eighth embodiment of the present invention, and FIG. It is a figure which shows the concentration profile of the silicon atom, oxygen atom, and nitrogen atom which are contained in the semiconductor substrate in the state in which the oxynitride film of the previous step was formed.
14A is a cross-sectional view showing a final oxynitride film forming step in the method for manufacturing a semiconductor device according to the eighth embodiment of the present invention, and FIG. 14B is a final view in the eighth embodiment. It is a figure which shows the density | concentration profile of the silicon atom, oxygen atom, and nitrogen atom which are contained in the semiconductor substrate in the state in which this oxynitride film was formed.
15A is a cross-sectional view showing an element isolation region forming step in a semiconductor device manufacturing method according to a ninth reference embodiment of the present invention, and FIG. 15B is an element isolation region in the ninth reference embodiment; It is a figure which shows the density | concentration profile of the silicon atom contained in the semiconductor substrate in the formed state.
FIG. 16A is a cross-sectional view showing a silicon dioxide film forming step in a method for manufacturing a semiconductor device according to a ninth reference embodiment of the present invention, and FIG. It is a figure which shows the concentration profile of the silicon atom and oxygen atom which are contained in the semiconductor substrate in the formed state.
FIG. 17A is a cross-sectional view showing a previous step of forming an oxynitride film in a method for manufacturing a semiconductor device according to a ninth reference embodiment of the present invention, and FIG. It is a figure which shows the concentration profile of the silicon atom, oxygen atom, and nitrogen atom which are contained in the semiconductor substrate in the state in which the oxynitride film of the previous step was formed.
18A is a cross-sectional view showing a final oxynitride film forming step in the method for fabricating a semiconductor device according to the ninth embodiment of the present invention, and FIG. 18B is a final view in the ninth embodiment. It is a figure which shows the density | concentration profile of the silicon atom, oxygen atom, and nitrogen atom which are contained in the semiconductor substrate in the state in which this oxynitride film was formed.
FIG. 19 is a cross-sectional view of a conventional semiconductor device.
[Explanation of symbols]
10 Semiconductor devices
11 High concentration impurity region
12 Gate insulation film
13 Gate electrode
15 Device isolation region
16 Silicon dioxide film
17 Pre-stage oxynitride film
18 Final oxynitride film

Claims (3)

Forming an insulating film on the semiconductor layer made of silicon, in the manufacturing method of a semiconductor device in which example Bei and forming a conductive film on the insulating film,
The step of forming the insulating film includes an oxide film forming step for forming a silicon dioxide film as a base on the semiconductor layer, and an NO gas and an O ₂ gas for the silicon dioxide film after the oxide film forming step. the concentration of nitrogen atoms in the vicinity of the interface of the semiconductor layer side facilities to heat treatment in an atmosphere of a gas mixture, by the oxidation treatment and the nitriding process on the silicon dioxide film are performed in parallel, in the silicon dioxide film with A silicon oxynitride film in which a distribution peak is formed and the concentration of nitrogen atoms at the peak position is in the range of 1.5 atomic% to 5 atomic% and the semiconductor layer is also oxynitrided Including a nitride film forming step,
The method of manufacturing a semiconductor device , wherein the step of forming the conductive film includes forming a conductive film made of polycrystalline silicon doped with impurities at a high concentration after the step of forming the oxynitride film . The amount of nitrogen atoms introduced in the vicinity of the interface on the semiconductor layer side in the silicon oxynitride film is substantially proportional to the amount of increase in the thickness of the insulating film due to heat treatment in the oxynitride film formation step. A method for manufacturing a semiconductor device according to claim 1.   3. The method of manufacturing a semiconductor device according to claim 1, wherein the heat treatment in the oxynitride film forming step is performed under high pressure.

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