JP2000232102A - Manufacture of dielectric film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a manufacturing method of a dielectric film whose leakage current is little, as a manufacturing method of a dielectric film which is used as a capacitive insulating film of a memory cell. SOLUTION: When a BST(barium strontium titanate) film 17x containing carbon compound 25 is heat-treated, the heat treatment is performed at a temperature, e.g. of 700 deg.C wherein elimination of the carbon compound becomes active. Thereby BST can be crystallized while the carbon compound 25 in the BST film 17x is eliminated. In particular, by increasing the rate of temperature rise up to a retaining temperature, the carbon compound 25 can be effectively eliminated from the BST film 17x, before the carbon compound 25 becomes hard to be eliminated on account of crystallization of BST. Thereby a BST film as a dielectric film of high permitivity which contains no carbon compound increasing leakage current can be formed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for manufacturing a capacitor and a dielectric film used for a capacitance film of a semiconductor memory.

[0002]

[Prior Art] With the development of multimedia society,
While the size of multimedia devices is becoming more compact, the amount of digital information handled there is increasing more and more, so the semiconductor memory mounted in multimedia devices will become more and more highly integrated in the future. Is expected to evolve. However, among semiconductor memories, for example, in a dynamic random access memory (hereinafter referred to as a DRAM) having a mechanism for storing information in a capacitance insulating film, it is necessary to advance the miniaturization of cells in accordance with the high integration. so,
It is necessary to maintain the charge capacity of the capacitor insulating film of each cell at a value almost as usual (about 30 fF). For this reason, in recent years, as a material for forming a capacitive insulating film of a DRAM cell,
For example, barium strontium titanate (hereinafter referred to as B
Technology for utilizing a material having a high dielectric constant, such as ST, has been actively developed. As a method of depositing a thin film of a material such as BST containing a heavy element, metal organic chemical vapor deposition (hereinafter referred to as MOCVD) will be used in the future in view of uniformity of film thickness. Are also considered promising.

FIG. 10 is a cross-sectional view schematically showing an example of the configuration of a conventional MOCVD apparatus used for depositing a BST film on a substrate.

[0004] As shown in FIG.
A raw material supply device 101 having two liquid containers 101a to 101c, a mixer 103 for adjusting the mixing ratio of the liquid material from each of the liquid containers 101a to 101c, and a liquid pump 105 for forcibly flowing the liquid material; , A vaporizer 107 for vaporizing a liquid material, and a reaction furnace 111, and the above-mentioned devices are connected by piping.
Substrate 1 for growing a BST film in reactor 111
09 is installed. The reaction furnace 111 is provided with an exhaust system 113 for reducing the pressure in the furnace to a reduced pressure state, and a gas introduction pipe 115 for introducing an oxidizing gas such as oxygen.

Here, the liquid containers 101a, 101b, 1
01c has Ba, which is a raw material for forming a BST film,
(DPM) ₂ , Sr (DPM) ₂ , Ti (O-iPr)
₂ (DPM) ₂ is dissolved in THF at a concentration of 0.1 mol / L. FIG. 11 is a diagram showing a molecular formula of Ba (DPM) ₂ which is one of the liquid materials.

[0006] The mixer 103 includes a liquid container 101.
By adjusting the flow rates of the liquid materials from a, 101b, and 101c, the mixing ratio of each liquid material is set to a desired value. The vaporizer 107 evaporates the liquid material sent from the liquid pump 105 by elevating the temperature, mixes the carrier gas sent from the carrier gas introduction pipe 108 with the vaporized source gas, and forms a reaction furnace. Send it into 111. In general, an inert gas having low reactivity, for example, argon or nitrogen gas is often used as the carrier gas. On the other hand, in the reaction furnace 111, the substrate 109 is heated to about 450 ° C. by a heater (not shown). Then, the raw material gas vaporized in the vaporizer 107 is mixed with oxygen sent from the gas introduction pipe 115 in the reaction furnace 111 and oxidized and decomposed on the surface of the heated substrate 109, thereby causing the substrate 109 to react. Good B on top
An ST film is deposited. At this time, the pressure in the reaction furnace 111 is about 1 Torr.

The BST film immediately after being formed by the above MOCVD apparatus generally has an amorphous structure when the film forming temperature is 500 ° C. or lower.
By subjecting the BST film to a heat treatment, the BST film is crystallized.

FIG. 12 is a diagram showing the annealing temperature dependence of the crystallite size of a 30 nm-thick BST film crystallized by heat treatment (annealing). In the figure, the horizontal axis represents the annealing temperature, and the vertical axis represents the crystallite size (nm) (substantially equal to the crystal size in the film thickness direction) obtained from the analysis by X-ray diffraction. Also, the BST film is
After being deposited at 450 ° C., it has been annealed for 30 minutes. As can be seen from FIG. 12, the crystallization of the BST film is 5 times.
Starting from a temperature between 00 and 600 ° C.

FIG. 13 shows that a BST film is formed in a nitrogen atmosphere at 60 ° C.
FIG. 6 is a diagram showing a correlation between a heat treatment time when a heat treatment (annealing) at 0 ° C. is performed and a relative dielectric constant of a BST film. As shown in the figure, BS having a high relative dielectric constant of 100 or more
In order to obtain a T film, it is necessary to perform long annealing for 25 minutes or more.

[0010]

However, by heat-treating the BST film formed by the conventional MOCVD method, it is possible to improve the relative dielectric constant of the BST film, but there is a problem that the leakage current is large. was there. The cause will be discussed below.

FIG. 14 is a diagram showing a correlation between a holding time and a leak current when a heat treatment is performed at 600 ° C. in a nitrogen atmosphere. Here, the vertical axis of the figure indicates the current (A / c) when a voltage of +1 (V) is applied between the upper and lower surfaces of the BST film.
m ² ). As can be seen from a comparison between FIG. 13 and FIG. 14, even if the heat treatment is performed for only 15 minutes in which the crystallization of the BST film has not progressed much (that is, the relative dielectric constant has hardly improved), the leakage current can be reduced by 10%. ^-5 (A /
cm ² ), which is a very large value.

According to the experiments of the present inventors, the cause is as follows.
It is considered as follows. Ba (DPM) shown in FIG.
_As can be seen from the molecular formula ₂ , in order to transport one Ba atom forming the BST film, a compound having many carbon atoms bonded must be used. for that reason,
Many carbon compounds remain in the BST film to be formed, and it is considered that the carbon compounds serve as a passage for the leak current.

[0013] The above problems are caused by the M
It is common to high dielectric films and ferroelectric films formed by the OCVD method. When a BST film exhibiting such a large leak current is used as a capacitor insulating film of a DRAM cell, the frequency of refreshing must be extremely increased in order to avoid volatilization of information due to the leak current. As a result, it is practically difficult to use a high dielectric film such as a BST film as a capacitance insulating film of the DRAM cell.

An object of the present invention is to provide a MOCV such as a BST film.
An object of the present invention is to provide a method for manufacturing a dielectric film having a high dielectric constant and a small leak current by taking measures for efficiently removing carbon and carbon compounds in a high dielectric film formed by the method D. .

[0015]

According to the present invention, there is provided a method for manufacturing a dielectric film, comprising the steps of: (a) depositing a carbon-containing dielectric film on a substrate; and performing heat treatment on the dielectric film. A step of crystallizing a body film, wherein the step (b) is a method performed under a condition that a substance containing at least carbon is desorbed from the dielectric film.

According to this method, a substance containing carbon, which causes the formation of a leak path and the generation of mobile ions, can be quickly eliminated from the dielectric film, so that a dielectric film having good leak characteristics can be formed. be able to.

The maximum temperature during the heat treatment in the step (b) is preferably higher than the temperature at which the substance containing at least carbon starts to be desorbed from the dielectric film.

The maximum temperature during the heat treatment in the step (b) is preferably higher than a temperature lower by 50 ° C. than a temperature at which a substance containing at least carbon in vacuum is desorbed most.

By setting the temperature rise rate during the heat treatment in the above step (b) to 0.2 ° C. or more per minute, the material containing carbon is more quickly removed from the dielectric film before the dielectric film is crystallized. Can be separated.

In the step (a), the desorption of the carbon-containing substance is promoted by depositing an amorphous dielectric film.

It is preferable that the dielectric film is an oxide and has a perovskite structure after the step (b).

In the step (b), by performing the heat treatment in an oxidizing atmosphere, the desorption of the carbon-containing substance can be promoted by converting at least the carbon-containing substance into a gas that is easily desorbed.

The same effect can be obtained by further providing a step (c) of performing a heat treatment in an oxygen atmosphere after the step (b).

The dielectric film is made of Ba, Sr, Ti, P
By containing at least one of b, Bi, Ta, Zn, Y, Mn, Ce, and Mg, a dielectric film serving as a high dielectric film or a ferroelectric film exhibits an effect of reducing leakage current. can do.

When the dielectric film is made of barium strontium titanate, it is possible to form a dielectric film having a high dielectric constant and good leak characteristics.

In the step (a), the dielectric film is deposited by using a metal organic chemical vapor deposition method to form the dielectric film at a low temperature which does not adversely affect the characteristics of the device. It is possible to effectively prevent a substance containing carbon present in the organic substance from remaining in the dielectric film.

In the step (a), the organometallic chemical vapor deposition can be easily performed by using a β-diketone-based organometallic complex.

In the step (a), the organometallic chemical vapor deposition may be carried out using a β-diketone organic metal complex dissolved in an organic solvent.

The maximum temperature during the heat treatment in the step (b) is preferably 650 ° C. or higher.

The dielectric film may be a capacitor insulating film of a dynamic random access memory (DRAM), a capacitor insulating film of a ferroelectric memory (FeRAM), a ferroelectric film of a ferroelectric gate memory (MFS), etc. As a result, a desired capacity can be secured with a small cell area.

For example, if applied to DRAM, DRA
High integration and large capacity of M can be achieved. In addition, if the cell area is the same, the cell height can be reduced, and this is particularly effective, for example, in the mixed mounting of DRAM and logic.

If applied to FeRAM, information writing / writing
FeR with low power consumption and small heat generation during reading
It is possible to realize AM.

If the present invention is applied to the MFS, it is possible to realize an MFS that consumes less power when writing information and generates less heat.

[0034]

DESCRIPTION OF THE PREFERRED EMBODIMENTS (First Embodiment) Hereinafter, a method for manufacturing a dielectric film according to a first embodiment of the present invention will be described with reference to the drawings.

FIG. 1 shows a structure of a dielectric film using the dielectric film of the present embodiment.
FIG. 3 is a cross-sectional view showing only a memory cell of a RAM. As shown in FIG. 1, an element isolation 12 surrounding an active region is formed on a Si substrate 11, and a MOS serving as a memory cell transistor of a DRAM is formed in the active region.
A transistor is provided. The MOS transistor has an insulated gate 14 provided on a Si substrate 11,
It comprises a source / drain diffusion layer 13 formed in a region located on both sides of the insulated gate 14 in the Si substrate 11. In addition, a first interlayer insulating film 15 made of a silicon oxide film is deposited on the substrate, and a capacity portion of a memory cell is provided on the first interlayer insulating film 15. The capacitance portion includes a lower electrode 16 made of a Pt film formed on the first interlayer insulating film 15, a capacitance insulating film 17 made of a BST film having a thickness of about 25 nm provided on the lower electrode 16, and And an upper electrode 18 provided on the capacitance insulating film 17. The lower electrode 16 of the capacitor is connected to one of the source / drain diffusion layers 13 of the memory cell transistor by a plug 19 penetrating the first interlayer insulating film 15. In addition,
As shown by the broken line in FIG. 1, a DRAM bit line 21 is provided on a second interlayer insulating film 20 deposited on the first interlayer insulating film 15, and this bit line 21 Plug 22 penetrating first and second interlayer insulating films 15 and 20
Is connected to the other of the source / drain diffusion layers 13.

Here, the manufacturing process of the DRAM memory cell according to the present embodiment will be described with reference to FIGS.

In the step shown in FIG. 2A, an element isolation 12 surrounding the active region is formed on the Si substrate 11 by using the LOCOS method or the like. Further, after depositing a silicon oxide film and a polysilicon film on the substrate, these are patterned to form an insulating gate 14 composed of a gate oxide film and a gate electrode on the active region. Then, arsenic ions are implanted into the Si substrate 11 using the insulating gate 14 as a mask, and the insulating gate 1 in the Si substrate 11 is implanted.
The source / drain diffusion layers 13 are located on both sides of
To form Further, a first interlayer insulating film 15 made of SiO ₂ is deposited on the substrate to a thickness of about 200 nm by, for example, low pressure chemical vapor deposition. Further, after the first interlayer insulating film 15 is flattened by reflow or CMP or the like, a contact window reaching one of the source / drain diffusion layers 13 is opened in the first interlayer insulating film 15. Then, for example, after polycrystalline silicon is formed by a low pressure chemical vapor deposition method, polysilicon is embedded in the contact window by dry etching with anisotropy strengthened to form a plug 19.

Next, in the step shown in FIG. 2B, a substrate temperature of 30 is formed on the substrate by using, for example, DC sputtering.
At 0 ° C., a first Pt film 16x is formed by depositing Pt with a thickness of 100 nm. Thereafter, the BST film 17x is deposited on the substrate by using the MOCVD apparatus described in the above-mentioned conventional technique. That is, Ba (DPM) ₂ , Sr (DP
M) ₂ , and liquid materials prepared by dissolving Ti (O-iPr) ₂ (DPM) ₂ in n-butyl acetate at a concentration of 0.1 mol / L each were mixed, and the mixture was heated to 220 ° C. The raw material gas is heated and vaporized, and the vaporized raw material gas is transported by Ar gas, thereby introducing the raw material gas into the reaction furnace. In the reaction furnace, the first Pt is reacted by reacting the source gas on a substrate heated to, for example, 450 ° C. in an atmosphere of a pressure of 5 Torr and an oxygen partial pressure of 25%.
A BST film 17x is formed on the film 16x.

Next, in the state shown in FIG.
The temperature is held at 00 ° C. for about 1 minute, and a heat treatment for crystallization of the BST film is performed.

Next, in the step shown in FIG. 2C, Pt is deposited to a thickness of 100 nm on the substrate by sputtering to form a second Pt on the BST film 17x.
The film 18x is formed.

Next, in the step shown in FIG. 2D, the first electrode 16x, the BST film 17x, and the second Pt film 18x are patterned to form the lower electrode 16,
A capacitance portion including the capacitance insulating film 17 and the upper electrode 18 is formed. The lower electrode 16 in this capacitance portion is connected to the source / drain diffusion layer 1 of the memory transistor by the plug 19.
3 is connected to one of them.

Although illustration of subsequent steps is omitted, deposition of a second interlayer insulating film, formation and embedding of contact windows,
Steps such as formation of a bit line are performed to form a memory cell of the DRAM.

Here, FIG. 2 is a characteristic of this embodiment.
The heat treatment step shown in (b) will be described in detail below.

In the film formation method by the MOCVD method, a compound containing a large amount of carbon is used as a liquid raw material.
A large amount of carbon compound also remains in the BST film 17x, which is a high dielectric film formed by the CVD method. Then, based on the experimental data shown below, the present inventors made the BST film with the carbon compound remaining on the BST film.
It has been found that when ST is crystallized, the leakage current of the BST film increases.

FIG. 3 is a diagram showing data on the desorption behavior of a carbon compound from a BST film obtained as a result of an experiment conducted by the inventor. In the figure, the horizontal axis represents the heat treatment temperature, and the vertical axis represents the detected ion current intensity (arbitrary unit) according to the amount of the carbon compound desorbed by the heat treatment. Here, as the carbon compounds to be monitored, especially desorption behavior using CO ₂ as a carbon compound of a molecular weight 28 prominent, 450 ° C., respectively, the two types of BST film formed at 600 ° C. The amount of CO ₂ desorbed due to the temperature rise is measured. The measured mass range of gas analysis is 1 to 100 (amu)
And the rate of temperature rise is 10 ° C./min.

As shown in FIG. 3, the desorption of the carbon compound starts from a little over 600 ° C.
It can be seen that the peak value of the desorption amount is shown around 00 ° C.
This is a fact common to the BST film formed at 450 ° C. and the BST film formed at 600 ° C., indicating that there is little relationship between the desorption phenomenon of the carbon compound and the film formation temperature. Have been.

FIG. 4 is a diagram showing the correlation between the holding time and the relative dielectric constant of the BST film when a heat treatment for crystallization is performed at 700 ° C. in a nitrogen atmosphere. That is, since the desorption amount of the carbon compound peaks at around 700 ° C. from the data in FIG. 3, it is considered that many carbon compounds are desorbed at around 700 ° C. 9 shows the data of the experiment.
As shown in FIG. 4, the holding time is about one minute,
It can be seen that a BST film having a relative dielectric constant exceeding 150 can be obtained. In the heat treatment for crystallization of the BST film by the conventional MOCVD method, a BST film having a relative dielectric constant of 150 is used.
In order to obtain a film, it was necessary to perform heat treatment at 600 ° C. for 30 minutes. In contrast, as in the present embodiment, 70
When the heat treatment at 0 ° C. is performed, it is considered that the crystallization of the BST film proceeds at a much higher speed than the conventional method. Further, FIG.
It is also shown that a BST film having a relative dielectric constant as high as 200 can be obtained in about 5 minutes.

FIG. 5 shows the correlation between the retention time when a heat treatment for crystallization is performed at 700 ° C. in a nitrogen atmosphere and the leak current density (A / cm ² ) when +1 [V] is applied. FIG. As shown in the figure, the leakage current of the BST film does not increase even if the holding time is longer, and the leakage current is 10 ⁻⁶ (A / cm).
Good leak characteristics slightly exceeding ² ) are obtained.

As described above, when the heat treatment temperature is 600.degree.
At 00 ° C., the crystallization process that affects the relative dielectric constant and the desorption process of the carbon compound that affects the leak current seem to be different. Hereinafter, this point will be considered.

FIGS. 6A to 6C are cross-sectional views showing the difference in the residual state of the carbon compound in the high dielectric film depending on the heat treatment conditions. In the following, the high dielectric film is the BST film 17x of the present embodiment, and the base is the first Pt film 1
6 (a) to 6 (c), the state of the carbon compound in the high dielectric film will be described.

FIG. 6A shows an example of as-depo. B in
FIG. 5 is a cross-sectional view for conceptually explaining the structure of an ST film 17x. As shown in FIG. 6A, BS formed at a low temperature
The T film 17x has an as-depo. Is in an amorphous state, and many carbon compounds 2 are contained in the BST film 17x.
5 is included as described above. However, since the BST film 17x is amorphous, a leak path is difficult to be formed in this state, and the BST film 17x is not formed.
The leakage current density of x is small. This is shown in FIG. 5 and FIG.
4, as-depo. It is also evident from the fact that the amount of leakage current at the time of is extremely small at 10 ^-8 (A / cm ^-2 ).

FIG. 6B is a sectional view conceptually illustrating the structure of the BST film 17x when the amorphous BST film 17x is heat-treated at 600 ° C. As can be seen from the data shown in FIG. 3, the carbon compound 25 hardly desorbs by the heat treatment at 600 ° C.
The BST film 17x is crystallized while containing many carbon compounds 25. At this time, it is considered that the remaining carbon compound 25 generally tends to segregate at crystal grain boundaries of the crystallized BST film 17x. Then, when segregated at the crystal grain boundaries, the current is particularly likely to flow, thereby forming a leak path. Further, even if the carbon compound 25 exists in the crystal grain boundary, it can be a source for generating mobile ion species. As a result, it is considered that the leakage characteristic of the BST film 17x is deteriorated by the remaining carbon compound 25.

FIG. 6C is a cross-sectional view for conceptually explaining the structure of the BST film 17x when the BST film 17x in the amorphous state is heat-treated at 700 ° C. As can be easily inferred from the data shown in FIGS.
The carbon compound 25 in the BST film 17x is desorbed from the BST film 17x by the high-temperature heat treatment of ° C. At this time, in the BST film 17x after the carbon compound 25 has been desorbed, if the crystallization of BST is not completed, the bonding between each element in BST is unstable, and since the temperature is high, the BST BST crystals are formed in a short time because of an active state in which a reaction occurs easily inside. That is, 70
In the high-temperature heat treatment at 0 ° C., the desorption of the carbon compound and the crystallization of the BST progress in a short time in the BST film 17x, and as a result, a BST film having good leak characteristics can be obtained because the carbon compound content is small. Is possible.

For efficient removal of the carbon compound, heat treatment at a temperature of 50 ° C. or lower than the temperature at which the peak value of the amount of desorption occurs was particularly effective.

However, even if the holding temperature of the heat treatment is high, if the rate of temperature rise until the holding temperature is too slow, the crystallization start temperature of BST is lower than the desorption temperature of the carbon compound. Before elimination proceeds, thermal crystallization of BST proceeds. Then, when the entire BST film is brought into a stable state by crystallization of BST, it seems that the carbon compound is hard to be desorbed. Therefore, it is considered that the desorption of the carbon compound and the crystallization of BST are effectively performed by increasing the heating rate. Experiments on the present embodiment have shown that it is desirable to increase the temperature at a rate of 0.2 ° C. or more per minute. In particular, rapid thermal annealing (R
TA) was an effective heat treatment method.

Further, since a large amount of the carbon compound is desorbed in a molecular state containing oxygen such as carbon monoxide or carbon dioxide, in an oxide such as BST, a crystal lacking oxygen is easily formed. . Such a state in which oxygen vacancies exist is a potential state in which positive ions are formed in the crystal, and thus electrons tend to stay in a portion having oxygen vacancies. Therefore, the presence of oxygen deficiency is one factor that causes a leak current. Therefore, by performing a heat treatment for crystallization on the BST film 17x, and further performing a heat treatment in an oxidizing atmosphere to compensate for oxygen deficiency,
Leakage current can be effectively reduced. The heat treatment for eliminating such oxygen defects is performed, for example, in an oxygen atmosphere at atmospheric pressure, at 550 ° C., for 30 minutes. Similar effects can be obtained even if the first heat treatment is performed in an oxidizing atmosphere.

In this embodiment, the lower electrode 1
6 is formed from the first Pt film 16x,
Even with a short-time heat treatment such as A, Pt migration to the BST film 17x occurred at a high temperature of 900 ° C. or higher, and the insulating property of the BST film 17x deteriorated. However, this phenomenon is due to the characteristics of the material of the lower electrode Pt, and does not limit the method for manufacturing the dielectric film of the present embodiment. For example, if the lower electrode was formed of a conductive material having excellent stability at high temperatures such as strontium titanate doped with Nb, the insulating property did not deteriorate.

According to the method of manufacturing the BST film according to the present embodiment, the carbon compound can be efficiently removed from the BST film by forming the BST film by the MOCVD method and then performing a heat treatment at a high temperature. A BST film with small leakage current can be formed. In particular, by increasing the heating rate up to the high temperature holding, the BST
It is possible to promote crystallization of BST while efficiently removing the carbon compound from the film. As a result, a BST film having a high relative dielectric constant and a small leak current can be formed.

If the BST film formed by the method of manufacturing a BST film according to the present embodiment is used as a capacitor insulating film of a DRAM cell or the like, a desired capacity can be secured with a small cell area. In the DRAM, high integration and large capacity can be achieved. If the cell area is the same, the cell height can be reduced.
This is particularly effective for mixed mounting of AM and logic.

In this embodiment, the high dielectric film is formed of BS.
Although constituted by T, the dielectric film of the present invention is not limited to the structure of this embodiment. Even when using a high dielectric film as a dielectric film, as the material constituting the high dielectric film, other than BST, for example, a dielectric material having a perovskite structure is a structure of a composite oxide represented by the chemical formula RMX ₃ ( BaTiO ₃ , SrTiO ₃ , PbTi
O _3, etc.) and, cerium oxide, tantalum oxide, zinc oxide, manganese oxide, yttrium can be used high-dielectric material such as magnesium oxide. Even with such a material, as-depo. In some cases, a carbon compound may be contained in the state described above, but by applying the method of the present invention, the effect of reducing leakage of the formed high dielectric film can be exerted. Further, by appropriately selecting the materials and conditions, an effect of improving the relative dielectric constant can be exerted.

Further, the dielectric film is made of a dielectric material other than a high dielectric material, such as lead zirconate titanate, strontium bismuth tantalate, and titanium as described in a third embodiment described later. It may be a ferroelectric film such as bismuth acid. By applying the method of the present invention to such a method of manufacturing a ferroelectric film, it is possible to form a good ferroelectric film having a small leak. Also,
By appropriately selecting the materials and conditions, the effect of improving the magnitude of the dielectric polarization can also be exerted.

In this embodiment, the MOC
Although the case where the heat treatment for crystallization is performed on the dielectric film formed by the VD method has been described as an example, the method of the present invention is formed by a deposition method in which a residual carbon compound remains in the dielectric film. It can be applied to all dielectric films. For example, even in a dielectric film formed by coating and sintering by a so-called sol-gel method or MOD method, a large amount of a carbon compound remains in the dielectric film. Also, in a dielectric film formed by a sputtering method,
Depending on the target material and the structure of the device, the carbon compound may remain in the dielectric film due to the incorporation of a carbon compound other than the target. Even in such a case, a dielectric film having a small leak can be obtained by applying the method for manufacturing a dielectric film of the present invention.

(Second Embodiment) Hereinafter, a second embodiment of the present invention will be described with reference to the drawings.

In the present embodiment, a method for manufacturing a memory cell having the same structure as the memory cell of the DRAM in the first embodiment will be described. The method of manufacturing a memory cell according to this embodiment is basically the same as that of FIG.
The steps shown in (a) to (d) are the same, but FIG.
Only the heat treatment conditions in the process shown in (1) are different from those in the method of the first embodiment.

FIG. 7 shows a BST film formed at 600 ° C.
FIG. 4 is a view showing the desorption behavior of a carbon compound when the temperature of the film is increased. In the figure, the horizontal axis represents the heat treatment temperature, and the vertical axis represents the detected ion current intensity (arbitrary unit) according to the amount of the carbon compound desorbed by the heat treatment. Here, as a carbon compound to be monitored, CO ₂ which is a carbon compound having a molecular weight of 28, whose desorption behavior was particularly remarkable, was used, and heat treatment at 700 ° C. for 30 minutes was performed under a nitrogen atmosphere at atmospheric pressure or atmospheric pressure. A BST film formed in an oxygen atmosphere of as-depo. Is compared with the BST film. The measured mass range of gas analysis is 1 to 100
In (amu), the heating rate is 10 ° C./min. As is clear from the figure, in the case where the heat treatment was performed in an oxygen atmosphere, the easily desorbed carbon compound was almost completely desorbed even at a heat treatment temperature of 700 ° C. In addition,
It has been confirmed that even when heat treatment is performed at a temperature lower by at least 20 ° C. than in a nitrogen atmosphere, a desorption effect equivalent to that in a nitrogen atmosphere is exhibited. This is because in the oxidizing gas atmosphere, the carbon compounds is oxidized attached in an unstable form of C _x H _y O _z with BST film, CO
_It is considered that they are chemically changed into gas molecules such as ₂ and H ₂ O.

As a result, according to the heat treatment method of the present embodiment, the carbon compound in the BST film is oxidized by performing the heat treatment on the
The carbon compound can be more efficiently desorbed by utilizing the change into gas molecules that are easily desorbed from the T film.

In particular, in a semiconductor device using a Si substrate, high-temperature processing adversely affects the characteristics of transistors and wirings. Therefore, it is important to manage the thermal history during device manufacturing. In this regard, in the heat treatment method of the present embodiment, since the heat treatment temperature can be lowered, it can be said that it is a process advantageous method for manufacturing a device formed using a Si substrate such as a DRAM.

An experiment was also conducted on a heat treatment in a vacuum. At present, a result that the carbon compound removal effect is slightly larger than that of a heat treatment in a nitrogen atmosphere at atmospheric pressure is obtained. There was no significant difference from the effect on This is presumably because no special change can be made to the carbon compound itself in a vacuum.

(Third Embodiment) Next, a third embodiment of the present invention will be described with reference to the drawings.

FIG. 8 is a sectional view showing only a memory cell of a ferroelectric memory (hereinafter referred to as FeRAM) using the dielectric film of the present embodiment. As shown in FIG. 8, an element isolation 12 surrounding an active region is formed on a Si substrate 11, and a MOS transistor serving as a memory cell transistor of a DRAM is provided in the active region. The MOS transistor includes an insulated gate 14 provided on a Si substrate 11 and source / drain diffusion layers 13 formed in regions located on both sides of the insulated gate 14 in the Si substrate 11.
A first interlayer insulating film 15 made of a silicon oxide film is deposited on the substrate.
5 is provided with a capacitor portion of a memory cell. This capacitance portion is formed by the Pt formed on the first interlayer insulating film 15.
A lower electrode 26 made of a film, and strontium bismuth tantalate (hereinafter referred to as SBT) which is a ferroelectric film having a thickness of about 150 nm provided on the lower electrode 26
And a top electrode 28 provided on the capacitor insulating film 27. And
The lower electrode 16 of the capacitance section is connected to one of the source / drain diffusion layers 13 of the memory cell transistor by a plug 19 penetrating the first interlayer insulating film 15. As shown by a broken line in FIG. 1, a DRAM is formed on the second interlayer insulating film 20 deposited on the first interlayer insulating film 15.
Bit line 21 is provided.
Is connected to the other of the source / drain diffusion layers 13 by plugs 22 penetrating the first and second interlayer insulating films 15 and 20.

Here, also in the present embodiment, the method of forming each part of the memory cell transistor, the first interlayer insulating film 15, the lower electrode 26, the upper electrode 28, the plug 19, and the like are the same as those in the first embodiment. However, only the method of forming the capacitive insulating film 27 is different, and only the portion will be described below.

In this embodiment, similarly to the manufacturing method described in the first embodiment, the SBT film is subjected to a heat treatment at a temperature at which the desorption of the residual carbon compound is active, for example, 800 ° C. After desorbing the residual carbon compound, SBT can be crystallized. As a result, the carbon compound can be efficiently desorbed according to the same principle as that of the first embodiment.
The leakage current of the capacitor insulating film 27 formed by patterning the film can be reduced. In particular, in the FeRAM, information is written by changing the polarization direction of the capacitor insulating film 27, which is a ferroelectric film, by the potential difference between the upper electrode 28 and the lower electrode 26. The information is read out by measuring the value of the current flowing when a predetermined voltage is applied between the information processing device and the device. At this time,
Since the leak current of the capacitor insulating film 27 is small, the leak current at the time of voltage application at the time of writing / reading can be reduced, so that the power consumption of each cell can be reduced. Therefore, by using the ferroelectric film of the manufacturing method of the present embodiment, the power consumption is small and the heat generation amount is small.
It is possible to realize AM.

(Fourth Embodiment) Next, a fourth embodiment of the present invention will be described with reference to the drawings.

FIGS. 9A and 9B are views showing the operation principle of a ferroelectric gate memory (hereinafter, referred to as MFS) using a ferroelectric film of the present embodiment. It is sectional drawing which extracts and shows only a part.

As shown in FIGS. 9A and 9B, the MFS memory cell according to the present embodiment is made of an SBT film having a thickness of about 150 nm formed on a P-type Si substrate 55 doped with B. Ferroelectric film 51 and a gate electrode 53 made of a Pt (platinum) film formed on the ferroelectric film 51
And a source region 57a and a drain region 57b formed by doping P (phosphorus) into regions located on both sides of the ferroelectric film 51 in the Si substrate 55.

Here, the Si substrate 55 is electrically grounded, and the ferroelectric film 51 is formed in accordance with the direction of the electric field applied immediately before to the gate electrode 53 as shown in FIG. It is polarized to one of the states indicated by “+” and “−” in FIG. Then, depending on the polarization state of the ferroelectric layer 51,
An induced charge 59 of a polarity that cancels this is induced in a region near the surface of the Si substrate 55. In the state shown in FIG. 9A, when the voltage applied to the gate electrode 53 changes from positive to 0, a negative induction which cancels this change is generated in a region near the surface of the Si substrate 55. Since a charge 59 is generated, when a potential difference is applied between the source portion 57a and the drain portion 57b, a drain current ID flows. However, in the state shown in FIG.
Is changed from negative to 0, so that S
In a region near the surface of the i-substrate 55, a positive induced charge 60 that cancels out this change is generated.
The drain current ID stops flowing even if a potential difference is applied between the drain current and the drain portion 57b. Therefore, this drain current ID
, The polarization state of the ferroelectric film 51 can be identified, and the ferroelectric film 51 can be used as a nonvolatile information storage unit.

In this embodiment, as in the manufacturing method described in the third embodiment, the SBT film is subjected to a heat treatment at a temperature at which desorption of the residual carbon compound is active, for example, 800 ° C. After desorbing the residual carbon compound, SBT can be crystallized. As a result, the carbon compound can be efficiently desorbed from the SBT film according to the same principle as in the first embodiment, so that the leakage current of the ferroelectric film 51 formed by patterning the SBT film is reduced. be able to. In particular, MF
In S, the polarization direction of the ferroelectric film 51 is determined based on the potential difference between the gate electrode 53 and the semiconductor substrate 55, and information is written. At this time, since the leakage current of the ferroelectric film 51 is small, It is possible to reduce the power consumption of each cell. For this reason, by using the ferroelectric film formed by the manufacturing method of the present embodiment as an information storage unit, it is possible to realize an MFS with low power consumption and small heat generation.

Such a non-volatile memory is in great demand especially for portable terminals such as notebook personal computers. In such a case, since these products are driven by a battery, if the leakage is large, the service life of the battery is shortened and the practical value is impaired.However, the use of the ferroelectric film formed by the manufacturing method of the present invention is not preferable. Thereby, it can contribute to long-term driving.

[0079]

According to the method for producing a dielectric film of the present invention,
By performing a heat treatment for crystallization on the carbon-containing dielectric film under the condition that at least a substance containing carbon is separated from the dielectric film, a dielectric film with small leakage current can be formed.

In particular, by increasing the temperature at a rate of at least 0.2 ° C. per minute, the desorption of the substance containing carbon can be promoted before the crystallization of the dielectric film is completed.

The method of manufacturing a dielectric film according to the present invention
DRAM, Fe that can secure desired capacity in a small cell area
It can be used for forming a capacitive insulating film of a memory cell of a RAM or MFS.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view illustrating a structure of a DRAM memory cell using a BST film according to a first embodiment of the present invention.

FIG. 2 is a cross-sectional view illustrating a manufacturing process of the memory cell according to the first embodiment.

FIG. 3 is a view showing data on a desorption behavior of a carbon compound from a BST film in the first embodiment.

FIG. 4 is a diagram illustrating a correlation between a holding time and a relative dielectric constant of a BST film when a heat treatment is performed in the first embodiment.

FIG. 5 is a diagram illustrating a correlation between a holding time when a heat treatment is performed and a leakage current density when +1 [V] is applied in the first embodiment.

FIG. 6 is a cross-sectional view showing a difference in a residual state of a carbon compound in a high dielectric film according to a heat treatment condition in the first embodiment.

FIG. 7 is a view showing a desorption behavior of a carbon compound when a temperature of a BST film is increased in a second embodiment.

FIG. 8 shows an FeRAM using an SBT film according to a third embodiment.
FIG. 3 is a cross-sectional view showing only the memory cell of FIG.

FIG. 9 is a cross-sectional view showing only a memory cell portion in order to explain the operation principle of an MFS using an SBT film according to a fourth embodiment.

FIG. 10 is a cross-sectional view schematically showing a configuration of a conventional MOCVD apparatus used for depositing a BST film on a substrate.

FIG. 11: Ba (DPM) which is one of the liquid materials
₂ is a diagram showing a molecular formula of FIG.

FIG. 12: B crystallized by heat treatment (annealing)
FIG. 4 is a diagram showing the annealing temperature dependence of the crystallite size of the ST film.

FIG. 13 is a diagram showing a correlation between a heat treatment time and a relative dielectric constant of the BST film when a heat treatment (annealing) at 600 ° C. is performed on the BST film in a nitrogen atmosphere.

FIG. 14 is a diagram showing a correlation between a holding time and a leak current when heat treatment is performed at 600 ° C. in a nitrogen atmosphere.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 11 Si substrate 12 Element isolation 13 Source / drain diffusion layer 14 Insulated gate 15 First interlayer insulating film 16 Lower electrode 17 Capacitive insulating film 18 Upper electrode 19 Plug 20 Second interlayer insulating film 21 Bit line 22 Plug 25 Carbon compound 26 Lower electrode 27 capacitive insulating film 28 upper electrode 51 ferroelectric film 53 gate electrode 55 Si substrate 57a source region 57b drain region 59 induced charge 60 induced charge

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) H01L 21/31 C04B 35/46 C 27/108 H01L 27/10 651 21/8242

Claims (17)

[Claims] A step of depositing a dielectric film containing carbon on a substrate; and a step of crystallizing the dielectric film by subjecting the dielectric film to a heat treatment. The method of manufacturing a dielectric film, wherein the step (b) is performed under a condition that a substance containing at least carbon is desorbed from the dielectric film. 2. The method for manufacturing a dielectric film according to claim 1, wherein the maximum temperature during the heat treatment in the step (b) is higher than a temperature at which a substance containing at least carbon starts to be desorbed from the dielectric film. A method for producing a dielectric film, comprising: 3. The method of manufacturing a dielectric film according to claim 2, wherein the maximum temperature during the heat treatment in the step (b) is higher than the temperature at which the amount of at least carbon-containing substance desorbed in vacuum is highest. A method for producing a dielectric film, wherein the temperature is higher than a temperature lower by 50 ° C. 4. The method for manufacturing a dielectric film according to claim 1, wherein the rate of temperature increase during the heat treatment in the step (b) is 0.1 minute per minute.
A method for producing a dielectric film, wherein the temperature is 2 ° C. or higher. 5. The method for producing a dielectric film according to claim 1, wherein in the step (a), an amorphous dielectric film is deposited. A method for manufacturing a dielectric film. 6. The method for manufacturing a dielectric film according to claim 1, wherein the dielectric film is an oxide, and the step (b) is performed.
Having a perovskite structure after completion of the process. 7. The method of manufacturing a dielectric film according to claim 1, wherein in the step (b), the heat treatment is performed in an oxidizing atmosphere. Manufacturing method of membrane. 8. The method of manufacturing a dielectric film according to claim 1, further comprising a step (c) of performing a heat treatment in an oxygen atmosphere after the step (b). A method of manufacturing a dielectric film. 9. The method for manufacturing a dielectric film according to claim 1, wherein said dielectric film is made of Ba, Sr, Ti, Pb, Bi, T
A method for manufacturing a dielectric film, comprising at least one of a, Zn, Y, Mn, Ce and Mg. 10. The method of manufacturing a dielectric film according to claim 9, wherein said dielectric film is made of barium strontium titanate. 11. The method for manufacturing a dielectric film according to claim 10, wherein in said step (a), said dielectric film is deposited by using a metal organic chemical vapor deposition method. Manufacturing method of membrane. 12. The method for producing a dielectric film according to claim 11, wherein in the step (a), the organometallic chemical vapor deposition is performed using a β-diketone-based organometallic complex. A method for manufacturing a dielectric film. 13. The method for producing a dielectric film according to claim 11, wherein in the step (a), the metal organic chemical vapor deposition is performed by using a β-diketone organic metal complex dissolved in an organic solvent. A method of manufacturing a dielectric film. 14. The method for producing a dielectric film according to claim 13, wherein the maximum temperature during the heat treatment in the step (b) is 650.
A method for producing a dielectric film, wherein the temperature is not less than ° C. 15. The method for manufacturing a dielectric film according to claim 1, wherein said dielectric film is formed by a dynamic random access method.
A method of manufacturing a dielectric film, which is a capacitive insulating film of a memory (DRAM). 16. The method for manufacturing a dielectric film according to claim 1, wherein said dielectric film is a capacitor insulating film of a ferroelectric memory (FeRAM). 17. The method for manufacturing a dielectric film according to claim 1, wherein the dielectric film is a ferroelectric film of a ferroelectric gate memory (MFS). Method.