JPH09312381A - Semiconductor device and manufacture thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a stable high-reliability capacitor by heat treating a dielectric film between a first and a second electrodes made of a conductive film and dielectric film having an electric flux density-electrolytic strength characteristic showing a hysteresis into a film involving a reformed film having no hysteresis. SOLUTION: 1) A Pt film is formed on a Si substrate 302 by the DC sputtering to form lower electrodes 302. 2) A material soln. is spin-coated on the whole surface by the sol-gel method to form an amorphous film 401 having a ferroelectric compsn. 3) It is dried to remove the solvent from this film 401 and the film 401 is rapidly heated to crystallize it to form a PZT film 403. 4) After forming a Pt film, upper electrodes 501 are formed and this film 403 is reformed in a N atmosphere by a second heat treatment to form a reformed PZT film 601. This eliminates the operation instability of a capacitor due to the ferroelectric property to thereby reduce the leak current.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor device and a method for manufacturing the same, and more particularly, to a small-sized and large-capacity capacitor particularly suitable for a semiconductor memory device such as a DRAM and a capacitor such as this can be easily manufactured. The invention relates to a semiconductor device and a method thereof.

[0002]

2. Description of the Related Art As is well known, a DRAM (semiconductor memory device capable of writing / reading at any time which requires rewriting)
Usually stores information by the accumulated charge of a capacitor formed on the substrate. This capacitor needs to reduce its area in order to miniaturize the DRAM, but on the other hand, in order to maintain the information signal strength and prevent malfunction, it is necessary to keep the electrostatic capacitance above a certain value. Required. For this reason, it is necessary to increase the capacitance per unit area of the capacitor in inverse proportion to the miniaturization of the DRAM. Therefore, conventionally, the electrode structure has been made three-dimensional and the dielectric film has a high dielectric constant.

Among them, tantalum pentoxide, barium strontium titanate, strontium titanate, and the like have been mainly studied as materials for increasing the dielectric constant of the dielectric film. Further, lead-containing perovskite type compounds such as lead titanate, lead zirconate titanate (PZT), lead lanthanum zirconate titanate (PLZT), etc. are also known as high dielectric constant materials. Capacitors using compounds also
Development is underway to reduce the size of capacitors.

Many of these lead-containing perovskite type oxides have a larger relative dielectric constant than tantalum pentoxide, strontium titanate, etc.
It is considered to be suitable for producing M.

However, many perovskite type compounds containing lead are in a ferroelectric phase in the temperature range of DRAM operation, and therefore exhibit ferroelectricity under normal operating conditions. That is, the polarization-electric field characteristics of the dielectric material show hysteresis characteristics. This hysteresis characteristic is due to the reversal of the direction of the ferroelectric polarization (residual polarization). Although remanent polarization is used as a data retention principle of non-volatile memory,
For the operation of the RAM, (1) a change in the amount of information charge caused by a change in polarization-electric field characteristics due to repeated polarization reversal and (2) a lift of the effective information charge amount due to polarization having a time constant in seconds ( Or, it is known to bring about an unfavorable action of (leak), which is not preferable.

Techniques for avoiding these obstacles have been studied from both aspects of operation method and material selection. The operation method is, for example, IEE Transactions on Electron Devices, 199.
Vol. 39, No. 2, pp. 2044 to 2049 (IEEE Trans
actions on Electron Devices, Vol. 39, No. 9, pp.
2044-2049 (1992)) is a typical ferroelectric substance such as PZ.
It has been proposed to use T to suppress the polarization reversal by limiting the direction of the electric field applied to the PZT to a single direction, and to avoid the fluctuation associated with the polarization reversal.

In terms of material selection, for example, 199
Proceedings of the 1st International Conference on Solid State Materials, pp. 204-206
Page (Extended Abstracts of the 1991 International C
onference onSolid State Devices and Materials, p
p.204-206 (1991)), it is proposed to add La to PZT to improve the characteristics, and it is reported that the leakage current reducing effect was obtained.

[0008]

However, when the above-mentioned conventional method is applied to the manufacture of DRAM, some problems occur. That is, when the direction of the voltage applied to the PZT is limited to a single direction, the electric field strength required to store the same amount of charge is doubled as compared with the case where the voltage is applied in both directions. Therefore, it is obvious that not only is it not desirable in terms of withstand voltage of the capacitor, but it is also undesirable in terms of long-term reliability. Further, according to the study by the present inventor, it has been found that the above method in which the direction of the applied voltage is limited to a single direction can only partially avoid the instability due to the fluctuation of the remanent polarization value. This is because the magnitude of the residual polarization changes with time even if the capacitor is driven under the condition that the polarization inversion does not occur, in other words, the relaxation phenomenon of the residual polarization cannot be avoided. Therefore, with this method, it is difficult to avoid instability due to fluctuations in the residual polarization value.

Further, the above method of adding an additive element such as La to the dielectric material has been found to be problematic in terms of mass productivity. For example, when La is added to PZT, the main characteristics such as dielectric characteristics greatly change depending on the amount of La added, and therefore the amount of La added must be strictly controlled, and process control is difficult. In addition, the usable film forming method is limited, and only the method having excellent composition reproducibility such as the sol-gel method can be used. Therefore, a method such as the CVD method, which has excellent step coverage and is suitable for high-purity films cannot be used, which is a serious limitation in application to large-scale DRAM.

Materials such as silicon dioxide and strontium titanate which do not theoretically have remanent polarization at the driving temperature of DRAM do not have these problems, but the relative permittivity of these materials is several even for barium strontium titanate. As low as about 100 (in the case of a thin film), using these films cannot achieve the purpose of DRAM miniaturization.

An object of the present invention is to solve the above-mentioned problems of the prior art, to provide a stable operation, high reliability, and a capacitor effective for downsizing a DRAM, and a capacitor such as this,
An object of the present invention is to provide a method of manufacturing a capacitor that can be manufactured easily and with high productivity.

[0012]

A semiconductor device of the present invention for achieving the above object comprises a first electrode and a second electrode made of conductive films, which are arranged to face each other, and the first electrode. There is a dielectric film formed between the electrode and the second electrode, and the dielectric film is heat-treated in a non-oxidizing atmosphere in a dielectric film that exhibits hysteresis characteristics in electric flux density-electric field strength characteristics at room temperature. It is characterized in that it comprises a capacitor which is a film including a modified film formed without the above hysteresis characteristic.

That is, in the present invention, the dielectric film of the capacitor is formed by heat-treating a dielectric film having a history of electric flux density-electric field strength characteristics at room temperature in a non-oxidizing atmosphere. It contains a modified film that does not have hysteresis characteristics. The dielectric film of the present invention having such an extremely peculiar structure has a polarization-voltage characteristic as shown in FIG. 1, for example, in the case of a PZT film. Thus, it was confirmed that they are significantly different.

That is, as is apparent from FIG. 1, even though the conventional dielectric film having ferroelectricity has a hysteresis characteristic in polarization-voltage characteristics, this dielectric film is non-oxidizing. The polarization-voltage characteristics of the dielectric film (modified film) of the capacitor of the present invention, which has been modified by heat treatment in an atmosphere, are almost linear, and the hysteresis characteristics disappear. Moreover, the relative permittivity retains the value of the ferroelectric film before the modification treatment.
It was confirmed that the dielectric film was extremely effective as a dielectric film for M.

Further, when the dielectric film according to the present invention is analyzed in the depth direction, as shown in FIG. 2, the dielectric layer 202 having hysteresis characteristics and the dielectric layer 203 having no hysteresis characteristics are shown. The laminated structure has a lower electrode 201 and an upper electrode 20.
It was found that it was formed during the period 4. The thickness of the dielectric layer 202 having the hysteresis characteristic becomes thinner as the temperature of the heat treatment performed to form the dielectric layer 203 having no hysteresis characteristic becomes higher. Especially this heat treatment temperature is 550
When the temperature is higher than or equal to ° C, the film thickness of the dielectric layer 202 having the hysteresis characteristic becomes 10 nm or less, and it is considered that the dielectric layer of the capacitor is constituted only by the dielectric layer 203 having substantially no hysteresis characteristic. It can be changed.

The P in the present invention having such a structure
The current-voltage characteristics of the ZT film and the current-voltage characteristics of the conventional PZT film were compared at a voltage sweep rate of 0.1 V / sec. As is apparent from FIG. 3, according to the present invention, the effect of reducing the leak current in the low voltage region is particularly remarkable. However, this effect is not essentially the effect of reducing the leak current, but is the effect caused by the disappearance of the slowly inverting polarization component such that the time constant is 1 second or more. Quantity stabilization has been achieved.

FIG. 4 shows a change in shape when a silicon dioxide film is formed as a passivation film (protective film) by the CVD method after forming a dielectric film using a PZT film. Lower electrode 3 formed on silicon substrate 301
02, the dielectric film 303 having the above-mentioned laminated structure is formed, and the silicon dioxide film (not shown) is further formed thereon.
The upper electrode 304 was formed after the formation of the upper electrode. However, in the present invention, as shown in FIG.
No peeling occurred, and normal passivation could be performed. However, in the conventional case, as shown in FIG. 4B, partial peeling 305 occurs on the upper electrode 304, and it is difficult to obtain high reliability.

The modified film is formed in contact with the second electrode, and between the modified film and the first electrode, a dielectric having a history of electric flux density-electric field strength characteristics at room temperature. A film is formed in contact with the first electrode. As the temperature of the second heat treatment becomes higher, the thickness of the modified film becomes thicker, and the electric flux density-electric field strength characteristic of the dielectric film formed on the first electrode shows a hysteresis characteristic. The film thickness becomes thin.

As the dielectric film, for example, a perovskite type oxide is used, and preferable results can be obtained by containing titanium or lead as a main constituent element.

Further, as the perovskite type oxide, lead titanate, lead zirconate titanate or lead lanthanum zirconate titanate can be used.

Zirconium is further contained as one of the main constituent elements together with titanium and lead, and the composition ratio of the lead, titanium and zirconium is 45 atom% to 5 respectively.
5 atom%, 10 atom% to 30 atom% Opobi 10 atom%
A preferable result can be obtained when the content is -30 atomic%.

Although the above-mentioned capacitor can be used for many purposes, it is particularly preferable as an information recording capacitor for DRAM.

In the semiconductor device of the present invention, the step of forming a first electrode having a predetermined shape on a semiconductor substrate and the step of forming a dielectric film having a ferroelectric composition to cover the first electrode. A step of crystallizing the dielectric film by performing a first heat treatment in an oxidizing atmosphere, a step of forming a second electrode covering the dielectric film, and a second step in a non-oxidizing atmosphere. It is formed by a manufacturing method including at least a step of performing heat treatment to modify at least a portion of the dielectric film near the interface with the second electrode to lose the ferroelectricity.

That is, after forming an amorphous ferroelectric film on the first electrode by a well-known coating method or the like, a first heat treatment is performed in an oxidizing atmosphere to crystallize. The heat treatment temperature at this time is a temperature equal to or higher than the crystallization temperature peculiar to the ferroelectric material. Further, instead of performing the first heat treatment, the first electrode may be previously maintained at a predetermined high temperature, and the ferroelectric material may be applied thereon.

After the second electrode is formed thereon, a second heat treatment is performed in a non-oxidizing atmosphere. In the crystallized ferroelectric film, near the interface with the second electrode. Is modified and loses its ferroelectricity, and the above hysteresis characteristics are not exhibited. As a result, the characteristics of the capacitor also have no residual polarization and the leak current is significantly reduced. At this time, the thickness of the modified portion of the ferroelectric film is set to the second value as described above.
The higher the temperature of heat treatment is, the thicker it becomes, and when it becomes 550 ° C or higher, the thickness of the part that is left unmodified becomes 10 nm or less, and the dielectric film of the capacitor is practically composed entirely of the modified film. You will be able to consider that it was done.

It is not clear why a dielectric film having a ferroelectric composition loses its properties as a ferroelectric when it is heat-treated in a non-oxidizing atmosphere, but a part of oxygen in the composition is lost by the heat treatment. It is presumed that it was lost. In this way, the dielectric film having the ferroelectric composition is modified by heat treatment in a non-oxidizing atmosphere, and the electric flux density-
The dielectric film that has lost the history of electric field strength characteristics is referred to as a modified film in this specification.

Further, in the modified film of the present invention formed by performing the second heat treatment, the charge amount, that is, the charge / discharge charge amount when not switching is almost the same as that in the conventional case where the heat treatment is not performed, or It has a big feature that it is larger than the conventional case. Conventionally, for example, when a dielectric film having a laminated structure using TiO ₂ as a paraelectric material is used for a capacitor, the hysteresis characteristic can be erased as in the present invention, but since the dielectric constant of TiO ₂ is low, The capacity of the capacitor will decrease.

FIG. 6 shows an example of changes in current-voltage characteristics depending on the heat treatment temperature. As the measurement method, first, the maximum voltage in the measurement range is applied, and the residual polarization is aligned in the voltage sweep direction for measurement, and then the voltage is swept from 0 V to the maximum voltage,
The current value was measured. As a result, in principle, it is possible to measure the leakage current that does not include the displacement current due to the polarization reversal.

As is apparent from FIG. 6, when the heat treatment temperature increased, the leak current decreased up to 525 ° C. It is considered that, of the decrease in the leak current, the decrease in the leak current in the relatively low voltage portion corresponds to the disappearance of the relaxation component of the remanent polarization. That is, in the case of a dielectric material having a normal ferroelectric property not according to the present invention, the remanent polarization generated by the voltage applied prior to the current measurement is mitigated by lowering the voltage once to 0 V during the current measurement, Lost. Since the current measurement is performed after this, a displacement current flows due to the lost remanent polarization being generated again.
In the present invention in which the ferroelectricity is suppressed, the leakage current in the low voltage portion can be suppressed because the current component based on the remnant polarization relaxation can be removed.

In the present invention, the leak current is reduced even in the portion where the current value sharply rises. As shown in FIG.
As compared with the case of the conventional dielectric having ferroelectricity, the voltage at the rising portion was improved by more than 1 V on both the positive voltage side and the negative voltage side. However, when the heat treatment temperature was 550 ° C. or higher, a slight increase in leak current was observed. Therefore, it has been found that the heat treatment temperature is preferably 550 ° C. or lower.

The step of forming the dielectric film having the above ferroelectric composition can be carried out by a coating method, and the coating solution used at this time is, for example, lead acetate, zirconium impropoxide and titanium. A solution of impropoxide in methoxymethanol can be used.

The first heat treatment in the oxidizing atmosphere after the coating can be performed at a temperature of 600 ° C to 750 ° C. By this first heat treatment,
The amorphous film is crystallized into a polycrystalline film.

In the second heat treatment performed in the non-oxidizing atmosphere after forming the second electrode, the dielectric film is one of the main constituent elements in the non-oxidizing atmosphere such as nitrogen or inert gas. 450 ° C when it does not contain lead
It can be performed at a temperature of ˜750 ° C., but when the dielectric film contains lead as one of the main constituent elements, the second heat treatment temperature is preferably 450 ° C. to 550 ° C. Is obtained.

After the second heat treatment, a second dielectric film covering the second electrode is formed as an interlayer insulating film, but it is preferable to form this second dielectric film by plasma CVD. Results are obtained, and the plasma CVD can be performed using a silicon hydride or an alcoholate compound as a source gas. When plasma CVD is performed using these raw material gases after forming the conventional dielectric film having the above ferroelectric composition, the dielectric film is reduced by hydrogen, which is not preferable, but in the present invention, This kind of obstacle does not occur.

[0035]

BEST MODE FOR CARRYING OUT THE INVENTION In the present invention, the sectional structure of the capacitor can be applied not only to the planar type shown in FIG. 2 but also to various types of capacitors such as a trench type or a stack type. Also, a DRAM using this capacitor
Not only the structure shown in FIG. 7 but also DR of various structures
It can be applied to AM and other semiconductor memory devices.

In the present invention, the total thickness of the dielectric film of the capacitor is selected within the range of 20 nm to 200 nm. If the total film thickness is larger than 200 nm, the meaning of using the ferroelectric film is lost. It is needless to say that the smaller the total film thickness is, the more preferable in order to increase the capacitance of the capacitor. However, it is difficult to manufacture a ferroelectric film having a thickness of less than 20 nm without any trouble in the present technology. is there.
In addition to the above compounds, films of some compounds can be used as the ferroelectric film, and platinum films can be used as the first and second electrodes.

As described above, the dielectric film having the above ferroelectric composition is not limited to the sol-gel type, but may be formed by the sputtering method or the C method.
It can be formed by the VD method.

That is, it is possible to use a sputtering method in an oxygen atmosphere using a target formed by sintering an oxide of lead, zirconium and titanium. In this case, if the substrate temperature is kept at 600 ° C. to 750 ° C. and the sputtering is performed, the first heat treatment after the film formation is unnecessary, and if the sputtering is performed at a temperature lower than 600 ° C., the first heat treatment is performed. It is necessary to perform the heat treatment of.

Further, the CVD method may be used for forming the dielectric film having the above ferroelectric composition. For example, P
b (DPM) ₂ , Zr (DPM) ₄ and Ti (i-OC)
_A CVD method in which ₃ H ₇ ) ₄ is used as a raw material and these raw materials are decomposed in an oxygen atmosphere can be used. In this case, if the film is deposited at a substrate temperature of 500 ° C. or higher, the first heat treatment is unnecessary.

[0040]

【Example】

<Embodiment 1> As shown in FIG. 5A, a silicon substrate 302 having a thickness of 200 is formed by a known DC sputtering method.
After forming a platinum film having a thickness of nm, unnecessary portions were removed by well-known sputter etching using a photoresist film as a mask to form a lower electrode 302 having a predetermined shape.

Next, as shown in FIG. 5B, a raw material solution was spin-coated on the entire surface by using a well-known sol-gel method to form an amorphous film 401 having a ferroelectric composition. At this time, the exposed portion of the silicon substrate 301 is covered with SiO 2.
₂ reacts with the amorphous film 401 to form a reaction layer 402.
Was formed.

Drying treatment is performed to remove the solvent contained in the amorphous film 401, and 650 is further applied by a rapid heating method.
The amorphous film 401 is subjected to crystallization heat treatment at 15 ° C. for 15 seconds.
Is crystallized, and as shown in FIG. 5C, the PZT film 40
3 was formed. The composition ratio of Zr and Ti of the obtained PZT film 403 was Zr / Ti = 50/50.

After a platinum film having a thickness of 100 nm is formed by the well-known DC sputtering method, unnecessary portions are removed by well-known sputter etching using the photoresist film as a mask, and as shown in FIG. 5 (4). The upper electrode 501 having a predetermined shape was formed. Further, a second heat treatment at 500 ° C. was performed in a nitrogen atmosphere. By this heat treatment, the PZT film 403 was modified and the modified PZT film 601 was formed.

FIG. 6 shows the result of measuring the relationship between the temperature and the polarization characteristic of the second heat treatment in the nitrogen atmosphere. As is clear from FIG. 6, when the heat treatment temperature is 450 ° C. or higher, the charges due to the hysteresis characteristic decrease and the heat treatment temperature is 4
It has been confirmed that it is effective to set the temperature to 50 ° C or higher.
However, since the leakage current slightly increases at 550 ° C. or higher, the heat treatment temperature is preferably in the range of 450 ° C. to 550 ° C.

In this embodiment, as the dielectric material,
Although PZT with Zr / Ti = 50 is used, the same effect can be obtained even if the element composition changes. However, in order to obtain a large capacity, it is preferable to suppress the compositional variation within a certain range, such as 45 to 55 atomic% of lead and 10% of zirconium.
It was confirmed that a high dielectric constant was obtained within the ranges of atomic% to 30 atomic% and titanium 10 atomic% to 30 atomic%, and therefore the effect of the present invention was also high. In addition, PbTiO ₃ and B
The ATiO ₃ A ferroelectric material with original materials and that several elements were added in less than 10 atomic%, Pb, Ba
The effect of the present invention was similarly confirmed for a ferroelectric material in which a part or all of the above was replaced with Sr or Ca.

<Embodiment 2> As described above, according to the present invention, both the leakage current reduction and the instability caused by remanent polarization can be solved, but it also has the effect of improving the process flexibility in the wiring process. This example shows this effect.

After the formation of the upper electrode, a wiring layer for connecting each memory cell and the peripheral circuit is provided. Usually, in order to secure insulation between the wiring layer and the upper electrode layer, an S layer is usually formed.
An insulating film containing iO ₂ as a main component is formed. This insulating film is formed by CVD from the viewpoint of throughput and step coverage.
A suitable method is a CVD method using silane or TEOS as a raw material. This decomposition of the raw material requires a temperature of 300 to 400 ° C. When a silicon hydrogen compound such as silane is used, hydrogen is generated as a by-product. Even in the case of TEOS, when a film is formed by using the plasma assist method, hydrogen-related by-products are also generated. These hydrogen or hydrogen-related byproducts are 30
Even at relatively low temperatures of 0 ° C to 400 ° C, PZT
The high dielectric constant film is reduced to deteriorate the characteristics. When the reduction is remarkable, peeling occurs at the interface between the high dielectric constant film and both electrodes, making it impossible to continue the process.

[0048]

[Table 1]

Table 1 shows various interlayer insulating film forming methods.
It is a comparison of the applicability of the present invention and the prior art capacitor. Both the sputter method and the sol-gel method are not exposed to a reducing atmosphere in principle, so that peeling does not occur even in the conventional technique. However, the sputtering method cannot be applied to a microfabricated capacitor because the electrical characteristics are deteriorated due to exposure to plasma and the step coverage is poor. Since the sol-gel method has a heat resistance of the capacitor of about 600 ° C., it cannot be densified at high temperature. Therefore, for example, the etching rate for buffered hydrofluoric acid is several times that of ordinary high-density SiO _2, and a through hole for electrical connection between the electrode and the wiring layer, which is performed after the interlayer insulating film is formed. The formation step by dry etching cannot be performed because damage to the underlying electrode that occurs at that time cannot be removed.

In the CVD method using a silane-based material, even if atmospheric pressure thermal CVD or plasma assisted CVD is used, peeling occurs at the electrode-high dielectric constant film interface in the capacitor of the prior art, and the actual capacitor is used. It was impossible to apply to the manufacturing process. In atmospheric pressure thermal CVD created under high oxygen partial pressure and in plasma assisted CVD performed at a pressure of 0.1 Torr or less, peeling did not occur, but deterioration of the dielectric itself centered on reduction of dielectric constant occurred and it was applicable. There wasn't.

On the other hand, according to the present invention, as is clear from Table 1, problems such as peeling did not occur in all insulating film forming methods. Further, no deterioration of the dielectric constant was observed except for the atmospheric pressure thermal CVD method and the high temperature plasma assisted CVD method. This is an extremely advantageous feature in forming an interlayer insulating film, and the improvement of throughput, reduction of the number of steps, and common use of manufacturing equipment have enabled a significant reduction in manufacturing cost.

Among the high oxygen partial pressure CVD methods,
In particular, if the oxygen partial pressure is increased, it may be possible to achieve the same stabilization and high breakdown voltage as in the present technique.
For example, the oxygen flow rate is set to about 10 times the raw material silane flow rate,
By lowering the substrate temperature to about 350 ° C., it is possible to form an interlayer insulating film while suppressing a decrease in dielectric constant. However, in the CVD by this method, the corresponding oxygen flow rate and substrate temperature conditions vary depending on the process conditions of the ferroelectric film, so that it is difficult to apply it to manufacturing. By using the present invention, the process of forming the interlayer insulating film can be made constant and the process can be standardized.

<Embodiment 3> The reduction of the leak current according to the present invention is effective for the basic performance improvement such as the improvement of the refresh interval when applied to the DRAM. An example of a DRAM using the capacitor of the present invention is shown in FIG.

In FIG. 7, reference numeral 901 is a silicon substrate, 902 is an element interlayer isolation oxide film, 903 is a conductive plug layer, 904 is an interlayer isolation film, 905 is a lower electrode, and 906.
Is a modified ferroelectric film, 907 is an upper electrode, and 908 is a reaction layer formed by the mutual reaction between the interlayer isolation film and the ferroelectric composition film.

The capacitance of this capacitor is 100 fF / μm
² , and the withstand voltage at 0.1 μA / cm ² was 3 V, which was confirmed to be suitable for practical use.

[0056]

As is apparent from the above description, according to the present invention, it is possible to eliminate the operational instability of the capacitor due to the ferroelectricity and reduce the leakage current, and at the same time, the limitation on the passivation is reduced. It is extremely useful for reducing power consumption, improving reliability, and lowering the cost of semiconductor memory devices.

[Brief description of drawings]

FIG. 1 is a diagram comparing polarization-voltage characteristics of the present invention and a conventional capacitor,

FIG. 2 is a cross-sectional view for explaining the structure in the depth direction of the capacitor of the present invention,

FIG. 3 is a diagram comparing current-voltage characteristics of the present invention and a conventional capacitor,

FIG. 4 is a diagram comparing the electrode shapes of the present invention and a conventional capacitor after passivation,

FIG. 5 is a process drawing for explaining the first embodiment of the present invention,

FIG. 6 is a graph showing processing temperature dependence of polarization value change according to the present invention;

FIG. 7 is a sectional view showing an example of a semiconductor memory device of the present invention.

[Explanation of symbols]

201 ... Lower electrode, 202 ... Dielectric layer having hysteresis characteristics,
203 ... Dielectric layer having no hysteresis characteristic, 204 ... Upper electrode, 301 ... Silicon substrate, 302 ... Lower electrode, 303
... dielectric film, 304 ... upper electrode, 305 ... peeling, 401
... amorphous film, 402 ... reactive layer, 403 ... crystalline film, 501 ... upper electrode, 601 ... reformed PZT film,
901 ... Silicon substrate, 902 ... Element isolation oxide film, 90
3 ... Conductive plug layer, 904 ... Interlayer separation film, 905 ... Lower electrode, 906 ... Modified ferroelectric film, 907 ... Upper electrode, 908 ... Mutual reaction layer.

Claims (21)

[Claims] 1. A first electrode and a second electrode made of conductive films, which are arranged to face each other, and a dielectric film formed between the first electrode and the second electrode. The dielectric film is a film including a modified film having no hysteresis characteristic formed by heat-treating the dielectric film having a hysteresis characteristic of electric flux density-electric field strength characteristic at room temperature in a non-oxidizing atmosphere. A semiconductor device comprising a capacitor. 2. The modified film is formed in contact with the second electrode, and between the modified film and the first electrode, the electric flux density-electric field strength characteristic shows a hysteresis characteristic at room temperature. The semiconductor device according to claim 1, wherein a dielectric film is formed in contact with the first electrode. 3. The semiconductor device according to claim 1, wherein the first electrode and the second electrode are a lower electrode and an upper electrode of a capacitor, respectively. 4. The semiconductor device according to claim 1, wherein the film thickness of the dielectric film having the hysteresis characteristic of the electric flux density-electric field strength characteristic is 10 nm or less. 5. The semiconductor device according to claim 1, wherein the dielectric film is a perovskite type oxide. 6. The semiconductor device according to claim 5, wherein the dielectric film contains titanium or lead as a main constituent element. 7. The semiconductor device according to claim 5, wherein the perovskite oxide is selected from the group consisting of lead titanate, lead zirconate titanate, and lead lanthanum zirconate titanate. 8. Zirconium is further contained as one of the main constituent elements, and the composition ratio of lead, titanium and zirconium is 45 atom% to 55 atom% and 10 atom% to, respectively.
The semiconductor device according to claim 6, wherein the content is 30 atom% and 10 atom% to 30 atom%. 9. The semiconductor device according to claim 1, wherein the capacitor is a DRAM information recording capacitor. 10. A first semiconductor device having a predetermined shape on a semiconductor substrate.
The step of forming the electrode, the step of forming the dielectric film having the ferroelectric composition covering the first electrode, and the first heat treatment in an oxidizing atmosphere to crystallize the dielectric film. A step of forming a second electrode covering the dielectric film, and performing a second heat treatment in a non-oxidizing atmosphere to remove at least a portion of the dielectric film near an interface with the second electrode. A method of manufacturing a semiconductor device, comprising at least a step of modifying a portion to lose ferroelectricity. 11. The step of forming a dielectric film having a ferroelectric composition is performed by applying a methoxymethanol solution of lead acetate, zirconium impropoxide and titanium impropoxide to the entire surface. The method of manufacturing a semiconductor device according to claim 10, wherein 12. The first heat treatment comprises 600 ° C. to 750 ° C.
The method of manufacturing a semiconductor device according to claim 10 or 11, wherein the method is performed at a temperature of ° C. 13. The method of manufacturing a semiconductor device according to claim 10, wherein the second heat treatment is performed at a temperature of 450 ° C. to 750 ° C. in a nitrogen or inert gas atmosphere. 14. The semiconductor device according to claim 10, wherein the second heat treatment is performed at a temperature of 450 ° C. to 550 ° C. in a nitrogen or inert gas atmosphere. Production method. 15. The step of forming a second dielectric film, which covers the second electrode, by plasma CVD after the second heat treatment is added.
15. The method for manufacturing a semiconductor device according to any one of 1 to 14. 16. The method for manufacturing a semiconductor device according to claim 15, wherein the plasma CVD is performed using a silicon hydride or an alcoholate compound as a source gas. 17. The step of forming a dielectric film having the ferroelectric composition is performed by a sputtering method in an oxidizing atmosphere using an oxide of lead, zirconium and titanium as a target. Item 11. A method for manufacturing a semiconductor device according to item 10. 18. The sputtering method uses a substrate having a temperature of 6
18. The method of manufacturing a semiconductor device according to claim 17, wherein the first heat treatment is omitted while the temperature is maintained at 00 [deg.] C. to 750 [deg.] C. 19. The semiconductor device according to claim 10, wherein the step of forming the dielectric film having the ferroelectric composition is performed by a CVD method of decomposing the raw material in an oxidizing atmosphere. Production method. 20. The raw materials are Pb (DPM) and Zr (DP).
M) and Ti (method of manufacturing a semiconductor device according to claim 19 which comprises using a -Oc ₃ H _{7) 4} as a raw material. 21. In the CVD method, the temperature of the substrate is set to 60.
21. The method for manufacturing a semiconductor device according to claim 19, wherein the temperature is 0 ° C., and the first heat treatment is omitted.