KR20050092368A - Dielectric film forming method - Google Patents

Abstract

A method for forming a high-K dielectric film on a substrate comprises a plurality of steps, each step including a processing for modifying the properties of the formed high-K dielectric film in an atmosphere mainly containing nitrogen.

Description

Dielectric Film Forming Method

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates generally to semiconductor devices, and more particularly to semiconductor devices having a high dielectric insulating film (so-called high K dielectric film) formed of metal oxides or metal silicates, and methods of manufacturing the same.

In semiconductor integrated circuit devices such as CMOS-LSI, which require ultra-high speed operation, field effect transistors (MOSFETs) constituting semiconductor integrated circuit devices are required to have very short gate lengths. Therefore, much effort is required for miniaturization of MOSFETs. It is done.

In such a miniaturized MOSFET, the scaling law imposes restrictions on the film thickness of the gate insulating film. For example, it is required to reduce the film thickness of the gate insulating film to about 2.5 nm or less by converting it into an oxide film thickness.

Conventionally, a silicon oxide film having a good leakage current characteristic and a low interfacial density has been used as a gate insulating film. However, in the conventional gate insulating film including the silicon oxide film, the direct tunnel current increases with the decrease of the physical film thickness of the gate insulating film. As a result, the gate leakage caused by the tunnel current is increased when the film thickness of the gate insulating film is further reduced. Current became a big problem. When the gate leakage current increases, for example, a substantial leakage current occurs at the gate-off, causing a problem such that a circuit of the semiconductor device does not operate normally or power consumption increases.

Therefore, in order to solve the above problem, it has been studied to use a high dielectric film (hereinafter referred to as a high K dielectric film) having a high dielectric constant or a metal silicate as a material of the gate insulating film.

Conventionally, such a high K dielectric film has been formed by a MOCVD method or an atomic layer CVD (ALD) method at a substrate temperature of 200 to 600 占 폚. In the ALD method, a raw material compound containing a metal element constituting a high K film is supplied in the form of a raw material gas to adsorb the raw material compound molecules on the surface of the substrate to be treated, and further oxidized by an oxidizing gas such as H ₂ O to obtain a high K. The dielectric film can be grown by one atomic layer. This low temperature film formation technique enables the growth of high K dielectric films having excellent morphology of the same film thickness. Also by the MOCVD method, a high K dielectric film having the same film thickness can be obtained.

On the other hand, the manufacturing process of the semiconductor device includes not only such a high K dielectric film formation process but also an ion implantation process performed in a plurality of times, and in such an ion implantation process, impurity elements introduced into the element region in the semiconductor substrate are included. In order to be activated, a rapid heat treatment process at temperatures of around 1000 ° C., typically at 1050 ° C., must be carried out.

Therefore, in a semiconductor device having a gate insulating film containing a high K dielectric film, the high K dielectric gate insulating film needs to maintain excellent electrical characteristics even after such high temperature heat treatment is performed.

In addition, when the gate insulating film contains defects such as a fixed charge or an interface level, carriers are trapped at these fixed charges or an interface level, thereby causing problems such as variations in flat-band voltages or changes in threshold characteristics. Occurs. In addition, leakage current through these defects also increases, which lowers the reliability of the semiconductor device. Therefore, also in the high K dielectric gate insulating film, it is required that the fixed electric charge or the interface level is not included in the film as in the conventional thermal oxide film.

However, the high K dielectric film formed by the low-temperature MOCVD method or the ALD method is an amorphous film, and even at first glance, even though it has excellent morphology, the film actually contains various defects. In particular, when formed by the ALD method using H ₂ O as the oxidizing agent, the film often contains a large amount of OH groups.

Therefore, the inventor of the present invention, in the research underlying the present invention, is used to activate an impurity element in a manufacturing process of a semiconductor device in the case of an amorphous high K dielectric film containing a large amount of defects in the film as described above. The change of properties was investigated by heat-treating on condition that it becomes.

Fig. 1A shows a cross-sectional TEM image of an HfO ₂ film formed by the ALD method in a study on which the inventor of the present invention is based.

Referring to FIG. 1A, an HfO ₂ film is formed on a silicon substrate having an interfacial oxide film (thermal oxide film) having a thickness of 1 nm at a substrate temperature of 300 deg. C as shown in FIG. By repeatedly supplying the HfCl ₄ gas and the H ₂ O gas, it can be seen that the film is formed with a thickness of 3.0 nm and has the same film thickness with the characteristic of a flat surface.

1B shows the TEM image of the film cross section when the HfO ₂ film of FIG. 1A is once heat treated at 700 ° C. in a nitrogen atmosphere and further subjected to heat treatment at 1050 ° C. for 10 seconds.

Referring to FIG. 1B, it can be seen that, as a result of this heat treatment at high temperatures, significant aggregation occurs in the HfO ₂ film on the silicon substrate, and the morphology of the HfO ₂ film continuously extending to the same film thickness shown in FIG. 1A is lost. have. As a result, the leakage current is greatly increased in the structure of FIG. 1B as described later. This indicates that, as described above, even though the HfO ₂ film of FIG. 1A has a good morphology at first glance, it actually contains a large amount of defects in the film, so that large-scale movement of atoms through such defects occurs when heat treatment is performed. . Such a film cannot be used as a gate insulating film of a high speed semiconductor device.

It should also be noted that in the TEM images of Figs. 1A and 1B, the silicon substrate has a lattice shape.

Japanese Patent Publication No. 11-177057

Japanese Patent Laid-Open No. 2001-152339

1A and 1B are diagrams illustrating a high K dielectric film formed by a conventional method and problems thereof.

2 is a view showing a conventional ALD process sequence.

3A to 3D are views for explaining a method of forming a dielectric film according to the first embodiment of the present invention.

4 is a view showing an ALD process sequence used in the first embodiment of the present invention.

Fig. 5 shows a high K dielectric film formed by the first embodiment of the present invention.

FIG. 6 is a diagram illustrating a state after high temperature heat treatment of the high K dielectric film of FIG. 5.

Fig. 7 is a diagram showing the configuration of the sheet type processing apparatus used in the first embodiment of the present invention.

Fig. 8 is a diagram showing a state after high temperature heat treatment of the high K dielectric film formed by the second embodiment of the present invention.

Fig. 9 is a diagram showing the construction of a membrane reforming apparatus used in the second embodiment of the present invention.

10 is a diagram showing the configuration of a MOS diode according to a third embodiment of the present invention.

FIG. 11 is a diagram illustrating a leakage current characteristic of the MOS diode of FIG. 10.

12A and 12B are diagrams showing C-V characteristics of the MOS diode of FIG. 10 before and after the high temperature heat treatment, respectively.

Fig. 13 is a diagram showing the relationship between the temperature at the time of the modification process and the average film thickness of the obtained high K dielectric film.

Fig. 14 is a diagram showing the structure of a film reforming apparatus used in the fourth embodiment of the present invention.

15 and 16 show a schematic structure of a high K dielectric film obtained in the fourth embodiment of the present invention.

FIG. 17 shows C-V characteristics when a high K dielectric film is formed in accordance with the fourth embodiment of the present invention in the MOS diode of FIG.

FIG. 18 is a diagram showing a leakage current characteristic when a high K dielectric film is formed according to the fourth embodiment of the present invention in the MOS diode of FIG.

19A to 19F are views showing the manufacturing process of the semiconductor device according to the fifth embodiment of the present invention.

Accordingly, it is an object of the present invention to provide a novel and useful method for forming a dielectric film that solves the above problems.

A more specific object of the present invention is to provide a method of forming a high K dielectric film that is stable against heat treatment at a high temperature on a substrate surface.

According to one aspect of the invention,

Forming a dielectric film in a plurality of times on the substrate surface; and

In each dielectric film forming step of dividing the plurality of times, the treating step of modifying the formed dielectric film in an atmosphere mainly containing nitrogen.

Provided is a method of forming a dielectric film for forming a dielectric film on a surface of a substrate.

According to another aspect of the invention,

Board,

A high K dielectric gate insulating film formed on the substrate,

A gate electrode formed on the high K dielectric gate insulating film,

A pair of diffusion regions formed on both sides of the gate electrode of the substrate,

The high K dielectric gate insulating film is provided with a semiconductor device having a structure in which a high K dielectric molecular layer and a SiON molecular layer are repeatedly stacked.

According to the present invention, in the manufacturing process of a semiconductor device using a high K dielectric film as a gate insulating film, the formation of the high K dielectric film is divided into a plurality of times, and the reforming process is performed in a nitrogen atmosphere in each of the plurality of forming steps. The atoms constituting the high K film in the high K dielectric film move to the equilibrium position, and the defects in the film are eliminated. As a result, in the manufacturing process of a semiconductor device using such a high K dielectric film as a gate electrode, an activation heat treatment is performed after the formation of the high K dielectric film to perform an ion implantation step to activate the impurity element introduced into the substrate by the ion implantation process at a high temperature. Even in the case of performing the step, a high K dielectric film stable against the activation heat treatment can be obtained. In particular, by performing the reforming process by a heat treatment step in a nitrogen-added nitrogen atmosphere, the interface between the semiconductor substrate and the high K dielectric film can be stabilized and generation of oxygen vacancies in the high K dielectric film can be suppressed. have. In addition, by repeatedly introducing Si, O, and N into the high K dielectric film, the stability against high temperature heat treatment is further improved and the leakage current is reduced. In addition, the high K dielectric film in which Si, O, and N are introduced into the film can effectively control the diffusion of impurity elements such as B (boron) contained in the gate electrode. Moreover, the said modification process can also be performed by a plasma process.

Other objects and features of the present invention will become apparent from the following detailed description of preferred embodiments, which will be made with reference to the drawings.

<First Embodiment>

3A to 3D show a method of forming a dielectric film according to the first embodiment of the present invention.

Referring to FIG. 3A, a high K dielectric film 13 such as an HfO ₂ film is formed on the surface of the silicon substrate 11 by an ALD method or a MOCVD method through an interfacial oxide film 12 having a thickness of about 1 nm. It is formed with a film thickness of about 0.6 nm corresponding to the film thickness of the atomic layer.

For example, in the case where the high K dielectric film 13 is formed by the ALD method, the substrate temperature is set to 300 ° C in the process of FIG. 3A, and nitrogen is intermediate as shown in "Step 1" of FIG. A gas purging process is provided, and gaseous raw materials such as HfCl ₄ and reactants such as H ₂ O are alternately supplied to the gas phase reaction apparatus. By this process, HfCl ₄ molecules are first chemosorbed on the surface of the silicon substrate 11, more precisely, on the surface of the interfacial oxide film 12, and the chemisorbed HfCl ₄ molecules are oxidized by H ₂ O gas. As a result, the HfO ₂ film 13 having the film thickness of 2 to 3 atomic layers is formed. 4 is a diagram showing a process sequence used in this embodiment. In the process of FIG. 3A, that is, the process of step 1 of FIG. 4, the chemical adsorption and oxidation treatment of the HfCl ₄ molecules are repeated about 11 times, so that the HfO ₂ film corresponds to the film thickness of 2-3 atomic layers as described above. It is formed with a film thickness of about 0.6 nm.

Thus, the high K dielectric film 13 formed at the process of FIG. 3A is 15 seconds at the temperature of 600-700 degreeC in nitrogen atmosphere in the process of FIG. 3B corresponding to "step 2" in the process sequence of FIG. As a result, the defects in the HfO ₂ film 13 are eliminated and the stress is relaxed. In addition, the HfO ₂ film in the amorphous state is crystallized by this heat treatment. Such a heat treatment of the FIG. 3B process can be easily carried out by, for example, removing the substrate to be processed from the ALD apparatus after the FIG. 3A process and moving it to a separate processing chamber through the substrate transfer chamber in a vacuum atmosphere.

Then, in this embodiment, In this way, by performing the re-ALD process for depositing _two membranes HfO In the process of Figure 3C corresponding to the "Step 3" in the phase crystallized HfO ₂ film, the process sequence of Figure 4 wherein the HfO ₂ films 13 are grown, and the HfO ₂ film 13 deposited first in the process of FIG. 3D corresponding to "Step 4" in the process sequence of FIG. 4 is again maintained at a temperature of 600 to 700 ° C for 15 seconds. The heat treatment is performed to modify the HfO ₂ film 13.

In addition, by repeating the processes of FIGS. 3C and 3D only as needed, as indicated by arrows in the figure, the film thickness is reduced through the SiO ₂ interfacial oxide film 12 on the silicon substrate 11 as shown in FIG. 5. A structure in which an HfO ₂ film of 3.0 nm is formed can be obtained.

FIG. 6 shows a state after heat-treating the structure of FIG. 5 obtained as described above, for 10 seconds at a temperature of 1050 ° C., as conventionally used to activate an impurity element introduced by an ion implantation process into a silicon substrate. TEM image.

As can be seen from FIG. 6, the HfO ₂ film 13 maintains a flat morphology even after such high temperature heat treatment, and it can be seen that the aggregation shown in FIG. 1B does not occur. Note also that the lattice image of the silicon substrate 11 is resolved also in the TEM image of FIG. 6.

Fig. 7 shows a schematic configuration of a film forming apparatus used for forming a high K dielectric film in this embodiment.

Referring to FIG. 7, the film forming apparatus is a load lock chamber 21 coupled to each other by a vacuum transfer chamber 21 having a robot transfer mechanism (not shown), the process of FIG. 3A or 3C. A deposition chamber 22 having an ALD device for carrying out the process, and a reforming processing chamber 23 for carrying out the process of FIG. 3B or 3D, wherein the substrate to be processed introduced through the load lock chamber 21 is deposited. After being transferred to the chamber 22, the reciprocating between the deposition chamber 22 and the reforming processing chamber 23 as necessary is finally returned to the load lock chamber 21.

By using the film forming apparatus of such a configuration, the process shown in Figs. 2A to 2D can be repeated as many times as necessary without exposing the substrate to be processed to the atmosphere.

In the present embodiment, as the reforming treatment chamber 23, a heat treatment furnace is maintained at a temperature of 500 to 800 ° C, preferably 600 to 700 ° C, and supplied with nitrogen gas to heat-treat the substrate in a nitrogen atmosphere. In such a heat treatment furnace, the oxygen concentration in the atmosphere can be suppressed, and the heat treatment in the oxygen-free atmosphere can be substantially performed. If necessary, as indicated by the dotted line in the figure, oxygen gas may be supplied to control the oxygen partial pressure in the atmosphere.

Second Embodiment

By the way, in the TEM image of FIG. 6, a defect occurs in a part of the SiO ₂ interfacial oxide film 12, and a reaction layer or a transition layer is formed in the silicon substrate 11 in response to the defect.

The composition of the transition layer is unclear at present, but this is due to the reduction of a portion of the very thin interface oxide film 12 upon heat treatment in a nitrogen atmosphere substantially free of oxygen in FIG. 3B or 3D, resulting in Si formed. And Hf in the HfO ₂ film 13 may react to form silicide.

On the other hand, FIG. 8 performs the reforming process of FIG. 3B or 3D in the reforming process chamber 23 of FIG. 7 at the temperature of 650 degreeC in the plasma nitridation apparatus 30 shown in FIG. The TEM image of the obtained sample is shown when a small amount of oxygen gas is added. However, the structure shown is a state after heat-processing the obtained sample further at 1050 degreeC for 10 second.

Referring to Fig. 9, the plasma nitriding apparatus 30 has a processing container 31 having a substrate holder 31B for holding an exhaust port 31A and a substrate W to be processed, wherein the processing container ( 31) is provided with a nitrogen gas and an oxygen gas, and a remote plasma source 32 is provided which excites this with an RF wave of 13.56 MHz to form nitrogen radicals and oxygen radicals. In the remote plasma source 32, a diluent gas such as He gas or Ar gas may be supplied as the plasma gas. By using such a remote plasma processing apparatus, insertion of charged particles due to plasma into the high K dielectric film can be effectively suppressed.

In the apparatus of FIG. 9, a high K dielectric film such as an HfO ₂ film on the substrate W to be exposed is exposed to nitrogen radicals or oxygen radicals formed by the remote plasma source 32, resulting in nitrogen on the surface of the HfO ₂ film. An atom or an oxygen atom is introduced.

Referring back to FIG. 8, in this embodiment, the interface between the silicon substrate 11 and the interfacial oxide film 12 is stabilized by adding oxygen in the atmosphere during the modification treatment of FIG. 3B or 3D. It can be seen that the defects shown were not generated.

In the structure of FIG. 8, since oxygen is contained in the atmosphere at the time of the modification process in this manner, the film thickness of the SiO ₂ interfacial oxide film 12 is increased to 1.75 nm after the high temperature heat treatment. However, such film increase of the interfacial oxide film 12 is minimized by appropriately controlling the oxygen partial pressure during the reforming process using the apparatus of FIG. 9, that is, suppressing the film increase of the SiO ₂ interfacial oxide film 12 from occurring. It is possible to do

In the present embodiment, since active radicals are generated by the plasma nitriding treatment device 30 and reforming is performed using such radicals, the reforming treatment at a low temperature of 650 ° C. or lower is possible. When the reforming treatment is performed at a low temperature in this manner, formation of crystal grain boundaries in the crystallized film can be suppressed by eliminating vacancy dangling bonds of the high K dielectric film 13 due to the reforming treatment.

Third Embodiment

FIG. 10 shows the configuration of the MOS diode 10 using the high K dielectric film formed on the silicon substrate in this manner as the capacitor insulating film. However, the same reference numerals are given to the above-described parts in FIG. 10 and the description thereof is omitted.

Referring to FIG. 10, in this embodiment, an n-type silicon substrate is used as the silicon substrate 11, and a platinum electrode 14 having a diameter of 200 μm is formed on the HfO ₂ film 13. .

In FIG. 10, the SiO ₂ interfacial oxide film 12 and the HfO ₂ film 13 constituting the MOS diode 10 have a film thickness of 1 nm and 3 nm, respectively, in a state immediately after deposition corresponding to FIG. 1A. Have

11 shows the leakage current characteristics of the MOS diode 10 thus formed. In Fig. 11,? Indicates the leakage current characteristics of the structure formed by dividing the HfO ₂ film 13 into two ALCVD deposition processes, and performing heat treatment at 700 DEG C in a nitrogen atmosphere in each deposition process. ② shows the leakage current characteristic after the high temperature heat treatment of the structure of ① at 1050 ° C. for 10 seconds. 3 indicates the leakage current characteristics when the HfO ₂ film 13 is divided into 11 cycles by the ALD method and heat-treated at 700 ° C. in a nitrogen atmosphere in each deposition cycle. 11, the vertical axis represents leakage current, and the horizontal axis represents voltage applied to the electrode 14.

Referring to Fig. 11, it can be seen that in the sample formed by dividing the HfO ₂ film 13 in two times, the leakage current increased greatly from ① to ② as a result of the high temperature heat treatment. In contrast, in the sample formed by dividing the HfO ₂ film 13 into 11 times, it can be seen that the leakage current does not change very much even when the high temperature heat treatment is performed, but rather decreases from ③ to ④.

As described above, in forming a high K dielectric film 13 such as HfO ₂ , FIG. 11 is not necessarily limited to the ALD method, but the film formation is divided into a plurality of times, and the modification process is performed every time. It is shown that the leakage current characteristics of the dielectric film 13 can be improved, and the film quality can be further improved by increasing the repetition cycle at the time of film formation.

12A and 12B show the capacitance characteristics (C-V characteristics) of the MOS diodes obtained when the atmosphere of the modification process was variously changed during the manufacture of the MOS diodes of FIG. 10. 12A shows the characteristics before performing the high temperature heat treatment for 10 seconds at 1050 ° C. for this MOS diode, and FIG. 12B shows the properties after the high temperature heat treatment.

12A and 12B,? Corresponds to the example of FIG. 1A, and forms the HfO ₂ film 13 with a thickness of about 3 nm by the ALD method of FIG. It is understood that leakage current measurement becomes impossible after the high-temperature heat treatment for 10 seconds. This indicates that aggregation seen in FIG. 1B occurs in the HfO ₂ film.

12A and 12B, (2) shows an example in which the HfO ₂ film 13 is formed by dividing the HfO ₂ film 13 into three times of 0.6 nm as shown in FIG. 4, wherein the modification treatment is performed in an NH ₃ atmosphere. Even in the case, the capacitance measured after the high temperature heat treatment at 1050 ° C. for 10 seconds was zero, and oxygen deficiency occurred in the HfO ₂ film 13 by the strongly reducing NH ₃ atmosphere.

On the other hand, (3) shows the case where the HfO ₂ film 13 is formed by dividing the HfO ₂ film 13 in three steps of 0.6 nm in accordance with the process sequence of FIG. In this case, it can be seen that the MOS diode has almost the same capacitance as before the heat treatment even after the heat treatment for 10 seconds at 1050 ° C.

In Figs. 12A and 12B,? Indicates that the HfO ₂ film 13 is formed by dividing the HfO ₂ film 13 in three steps of 0.6 nm in accordance with the process sequence of Fig. 4, and the remote plasma nitridation treatment described above with reference to Fig. 9 is performed. It shows the case where it is executed by the device. In this case, it can be seen that the capacitance of the MOS diode is further increased after the modification process.

In Fig. 12B,? Represents the result when the HfO ₂ film 13 is formed by dividing the HfO ₂ film 13 in three steps of 0.6 nm in accordance with the process procedure of Fig. 4, and the reforming process is performed in a nitrogen atmosphere.

As described above, according to the present invention, a high K dielectric film is formed by dividing the high K dielectric film as many times as possible, and the modification process is performed every time, thereby obtaining a high K dielectric film having excellent stability at high temperature and excellent electrical characteristics. The results of Figs. 12A and 12B show that when the formation of such a high K dielectric film is divided into a plurality of times, if the number of recovery is three or more times, a high K dielectric film of substantially sufficient film quality may be obtained.

FIG. 13 shows the relationship between the heat treatment temperature when the modification of the HfO ₂ film 13 is performed by heat treatment in a nitrogen atmosphere in the processes of FIGS. 3A to 3D and the average film thickness of the obtained HfO ₂ film 13. It is shown by comparing the before and after the high temperature heat treatment for 10 seconds at 1050 ℃.

Referring to FIG. 13, it is suggested that when the reforming temperature exceeds 800 ° C., the average film thickness before the high temperature heat treatment is slightly increased, and aggregation of the HfO ₂ film described above with reference to FIG. 1B occurs during the reforming process. On the other hand, in the case where the modification treatment is performed by heat treatment, when the treatment temperature is less than 500 ° C., it can be seen that the average film thickness after the modification treatment is greatly increased, so that an effective modification treatment cannot be performed.

On the other hand, when the temperature of the said modification process is made into 500 degreeC or more and less than 800 degreeC, it turns out that there is little change of the average film thickness before and behind the said high temperature heat processing, and the original flat morphology is maintained. Among these, it is the conclusion that especially the range of 600-700 degreeC is preferable from a viewpoint of an average film thickness change.

Fourth Example

14 shows the configuration of a reforming apparatus 40 used in the fourth embodiment of the present invention. However, in FIG. 14, the same reference numeral is attached | subjected to the part demonstrated previously, and abbreviate | omits description.

Referring to FIG. 14, in the reforming treatment apparatus 40, in addition to introducing nitrogen radicals or oxygen radicals from the remote plasma nitriding treatment apparatus 32 into the processing vessel 31, SiH ₄ or the like may be introduced from the line 33. Silicon compound gas is introduced to modify the surface of the high K dielectric film or the like formed on the surface of the substrate W to be processed.

When the reforming apparatus 40 of FIG. 14 is used in the processing chamber 23 of FIG. 7, for example, in the process of FIG. 3B or 3D, a layer having a Si-ON bond on the surface of the HfO ₂ film 13 Is formed, and the stability to the high temperature heat treatment of the film 13 is remarkably improved.

15 and 16 schematically show the structure of the HfO ₂ film formed by performing such a modification treatment at a temperature of 650 ° C.

Referring to FIG. 15, in the HfO ₂ film thus obtained, the HfO ₂ layer and the SiON layer shown in FIG. 16 are repeatedly formed in accordance with the processes of FIGS. 2A to 2D. In the illustrated example, two molecules of HfO ₂ are shown. A pair of SiON molecular layers is formed above and below the layer.

By repeatedly forming such a structure as shown in Fig. 15, it is possible to form a high K dielectric film containing N-Si-O bonds in the film. In such films, high-K dielectric films containing N-Si-O bonds are particularly stable against high temperature heat treatment because the atomic transport in the films is blocked by the SiON layer, and the diffusion of B (boron) and the like from the gate electrode is prevented. Excellent resistance can be obtained.

FIG. 17 shows capacitance (CV) characteristics in the case of using a 3 nm thick HfO ₂ film in which a Si-N bond is introduced into a film by a remote plasma treatment in the MOS diode of FIG. 10. The result measured at the frequency is shown.

Referring to Fig. 17, ① and ③ are comparative examples, and ① is a case where the HfO ₂ film 13 formed with the film thickness of 3 nm by the ALD method shown in Fig. 2 is heat-treated at 700 ° C. in a nitrogen atmosphere after film formation. Denotes the CV characteristic at the frequency of 100 kHz, and? Denotes the CV characteristic at the frequency of 1 MHz of the MOS diode having the same HfO ₂ film 13. That is, in (1) and (3), the high temperature heat treatment for 10 seconds at 1050 degreeC is not performed.

On the other hand, (2) forms a 3 nm HfO ₂ film 13 divided into three steps of 0.6 nm in accordance with the process sequence of FIG. 4, and for each film formation, the modification process is performed by Si, O and performed by introducing a N in the film, it indicates a CV characteristic of the frequency 100 kHz in the case of HfO ₂ film obtained in 1050 ℃ 10 chogan high temperature heat treatment. In addition,? Indicates CV characteristics at a frequency of 1 MHz of the MOS diode having the same HfO ₂ film 13.

As can be seen from Fig. 17, when the frequency is 100 kHz, the characteristic of ② is about the same as the characteristic of ①, whereas when the frequency is 1 MHz, the characteristic of ④ subjected to high temperature heat treatment at 1050 ° C. is obtained. It is understood that it is superior to the characteristic of (3) not performed. In the case of (2) and (4), even though the film contains a SiON layer which may lower the dielectric constant of the HfO ₂ film 13, the film defects are eliminated in such a structure, and therefore, particularly when high temperature heat treatment is performed. It shows that electrical properties can be obtained that surpasses the HfO ₂ film of defective ① or ③.

FIG. 18 compares and shows leakage currents in the MOS diodes 1 and 3 of FIG. 17 and the MOS diodes 2 and 4. 18 indicates a leakage current in the MOS diode of FIG. 10 when the HfO ₂ film formed with a thickness of 3 nm by the ALD method of FIG. 2 is heat-treated only at 700 ° C. in a nitrogen atmosphere. In the process sequence of FIG. 4, when the reforming process is performed by the remote plasma nitriding apparatus of FIG. 14, N, O, and Si are introduced into the film, and the HfO ₂ film thus modified is subjected to high temperature heat treatment at 1050 ° C. for 10 seconds. Indicates a leakage current.

As can be seen from FIG. 18, it can be seen that the leakage current characteristics are improved when the HfO ₂ film is formed in a plurality of times and subjected to high temperature heat treatment.

As described above, also in the present embodiment, since the active radicals are generated by the plasma nitriding treatment device 40 and the reforming treatment is performed using such radicals, the reforming treatment at a low temperature of 650 ° C. or lower becomes possible. . In this way, when the reforming treatment is performed at a low temperature, crystallization of the high K dielectric film 13 due to the reforming treatment can be suppressed, and formation of crystal grain boundaries in the crystallization film can be suppressed. As a result, the leakage current path formed according to such grain boundaries can be interrupted.

At this time, in this embodiment, by introducing a SiON component that forms an amorphous film alone in the high dielectric film, crystallization of the high K dielectric film can be suppressed even after high temperature heat treatment used for impurity activation treatment, and leakage due to grain boundary formation. Formation of a current, defect formation such as an interface level can be suppressed.

Fifth Embodiment

19A to 19F show a semiconductor device manufacturing process according to the fifth embodiment of the present invention.

Referring to Fig. 19A, an element isolation region 51B for partitioning the element region 51A is formed in the p-type silicon substrate 51, and As or P is ionized in the element region 51A in the process of Fig. 19B. The channel doping region 51a is formed by implantation.

Further, in the process of FIG. 19C, a thermal oxide film having a thickness of about 1 nm is formed on the structure of FIG. 19B corresponding to the interfacial oxide film 12, and thereafter, HfO ₂ is formed on the structure of FIG. The gate insulating film 52 is formed by forming a high K dielectric film such as a thickness of about 3 nm.

In the process shown in Fig. 19D, the polysilicon film is deposited on the gate insulating film 52 in the same manner, and the polysilicon gate electrode 53 is formed by patterning it. In the present embodiment, the polysilicon gate electrode 53 has a gate length of 0.1 μm or less.

Incidentally, in the process of Fig. 19D, inclined pocket injection of As or P is performed using the polysilicon gate electrode 53 as a mask, followed by diffusion injection, whereby the gate electrode 53 is in the element region 51A. Source diffusion regions 51b and drain diffusion regions 51c are formed on both sides of the substrate.

In the process of Fig. 19E, after forming the sidewall insulating film 53a on both sides of the gate electrode 53, the gate electrode 53 and the sidewall insulating film 53a are masked in the process of Fig. 19F. By ion implantation of As or P, the source region 51d and the drain region 51e are formed.

In the present embodiment, when the high K dielectric film in the gate insulating film 52 is formed in the process of Fig. 19C, it is executed by the step of repeatedly performing the modification process in the middle as described above with reference to Fig. 4. In this case, Step 1 and Step 3 may be an ALD process, may be a MOCVD process, Step 2 and Step 3 may be a heat treatment in a nitrogen atmosphere, a heat treatment in a nitrogen atmosphere with oxygen, plasma nitridation treatment Or a plasma nitridation treatment in which oxygen is added, or a plasma nitridation treatment in which Si compounds such as SiH ₄ and oxygen are added.

By forming the gate insulating film 52 in this manner, the high K dielectric film in the gate insulating film 52 has improved resistance to heat treatment, and the source diffusion region 51a, drain diffusion region 51b, and source region ( When the impurity elements such as As and P injected into the 51d) and the drain region 51e are activated by high temperature heat treatment, defect formation such as aggregation of the film does not occur. Further, in the gate insulating film 52 thus formed, excellent electrical characteristics, which are characterized by low leakage current and excellent C-V characteristics, are maintained even after the high temperature thermal activation treatment.

In the above description, the HfO ₂ film was formed by the ALD method, but it can also be formed by the MOCVD method. In this case, TDEAH, TDMAH, etc. can be used as an organic metal raw material. Further, not limited to HfCl ₄ as a raw material is also at the time of forming a film HfO ₂ by the ALD method may be used such as TDMAH.

In addition, in the present invention, the high K dielectric film is not limited to the HfO ₂ film, but a metal oxide or transition metal oxide such as a ZrO ₂ film, an Al ₂ O ₃ film, Ta ₂ O ₅ , Y ₂ O ₃ , or a rare earth oxide, HfSiO, etc. ₄ , a silicate of transition metals such as ZrSiO ₄ films, rare earth metals, and aluminates thereof may be used.

In addition, in FIG. 7, the example in which the formation and modification of the high K dielectric film is carried out by moving the substrate in a separate processing chamber using a sheet type processing apparatus is described. However, the formation and modification of the high K dielectric film are performed in the same processing apparatus. It can also be performed, replacing a process gas in the process.

In the present invention, the reforming process may be performed in an atmosphere in which any one of oxygen, NO, O ₃ , SiH ₄ , Si ₂ H ₆ , NH ₃ , H ₂ , and He is added to nitrogen gas.

In addition, although the above description demonstrated the example which uses a high K dielectric film for the gate insulating film of a high speed semiconductor device, this invention is applicable also to manufacture of DRAM which uses a high K dielectric film as a capacitor insulating film.

As mentioned above, although preferred embodiment of this invention was described, this invention is not limited to this specific embodiment, A various deformation | transformation and a change are possible within the summary of this invention.

According to the present invention, in the manufacturing process of a semiconductor device using a high K dielectric film as a gate insulating film, the formation of the high K dielectric film is divided into a plurality of times, and a reforming process is carried out in a nitrogen atmosphere in each of the forming steps of the plurality of times. By doing so, the stress in the high K dielectric film is reduced, and the defect of the film is eliminated. As a result, in the manufacturing process of the semiconductor device using such a high K dielectric film as the gate electrode, it is stable to the activation heat treatment process at high temperature of the impurity element introduced into the substrate by the ion implantation process, which is performed after the formation of the high K dielectric film. A K dielectric film can be obtained. In particular, by performing the above modification treatment step in a heat treatment step in a nitrogen-added nitrogen atmosphere, the interface between the semiconductor substrate and the high K dielectric film can be stabilized and generation of oxygen vacancies in the high K dielectric film can be suppressed. . In addition, by repeatedly introducing Si, O, and N into the high K dielectric film, the stability against high temperature heat treatment is further improved and the leakage current is reduced. In addition, the high K dielectric film in which Si, O, and N are introduced into the film can effectively control diffusion of impurity elements such as B (boron) contained in the gate electrode. Moreover, the said modification process can also be performed by a plasma process.

Claims (20)

Forming a dielectric film by dividing it into a plurality of times on the substrate surface; and A method of forming a dielectric film for forming a dielectric film on the surface of a substrate, comprising the step of modifying the dielectric film formed by dividing the plurality of times, wherein the formed dielectric film is modified in an atmosphere mainly containing nitrogen. The method of forming a dielectric film according to claim 1, wherein the atmosphere further contains oxygen. The method of forming a dielectric film according to claim 1, wherein the atmosphere further contains gaseous molecules of a Si compound. The method of claim 1, wherein one or more gases selected from the group consisting of NO, O ₃ , SiH ₄ , Si ₂ H ₆ , NH ₃ , H ₂ and He are further added to the atmosphere in the heat treatment step. A method of forming a dielectric film, characterized by the above-mentioned. The method of forming a dielectric film according to claim 1, wherein the modification treatment step includes a heat treatment step. The method of forming a dielectric film according to claim 5, wherein the heat treatment step is performed at a temperature of 500 ° C or more and less than 800 ° C. The method of forming a dielectric film according to claim 5, wherein said heat treatment step is performed at a temperature of 600 to 700 캜. The method of forming a dielectric film according to claim 1, wherein the modification treatment step includes a plasma treatment step. The method of forming a dielectric film according to claim 8, wherein said plasma processing step comprises exposing said dielectric film to nitrogen radicals. 10. The method of claim 9, wherein said plasma treatment step further comprises exposing said dielectric film to oxygen radicals. The method of claim 10, wherein the plasma treatment process further comprises exposing the dielectric film to Si compound molecules. 9. The method of forming a dielectric film according to claim 8, wherein said plasma processing step is performed by a remote plasma processing step. The method of forming a dielectric film according to claim 8, wherein said plasma treatment step is performed at a temperature of 650 DEG C or lower. The method of forming a dielectric film according to claim 1, wherein each dielectric film forming step of dividing the plurality of times is performed by an ALD method. The method of forming a dielectric film according to claim 1, wherein each dielectric film forming step of dividing the plurality of times is performed by a MOCVD method. A substrate, a high K dielectric gate insulating film formed on the substrate, a gate electrode formed on the high K dielectric gate insulating film, and a pair of diffusion regions formed on both sides of the gate electrode of the substrate; Forming a high K dielectric gate insulating film on the substrate in a plurality of times; and A method of manufacturing a semiconductor device, comprising: a step of forming a high K dielectric film divided into a plurality of times, wherein the formed high K dielectric film is modified in an atmosphere mainly containing nitrogen. The manufacturing method of a semiconductor device according to claim 16, wherein the atmosphere further contains oxygen. The method of manufacturing a semiconductor device according to claim 16, wherein the atmosphere further comprises gaseous molecules of a Si compound. Board, A high K dielectric gate insulating film formed on the substrate, A gate electrode formed on the high K dielectric gate insulating film, and A pair of diffusion regions formed on both sides of the gate electrode of the substrate, The high K dielectric gate insulating film has a structure in which a high K dielectric molecular layer and a SiON molecular layer are repeatedly stacked. 20. The semiconductor device of claim 19, wherein the high K dielectric molecular layer is selected from any one of metal oxides, transition metal oxides, metal silicates, and metal aluminates.