JPH0964291A - Ferroelectric memory and manufacture thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a ferroelectric memory having a good symmetry of a shape of a P-V hysteresis curve which is a relation between impressed voltage V of the ferroelectric memory and a polarization amount P to be formed in a ferroelectric film opposed thereto. SOLUTION: This memory has a constitution wherein an oxide silicon film 12 is formed on a silicon substrate 10, overlaid with a combination element 18 of a lower part electrode 14 and a ferroelectric film 16, with an upper electrode 20 piled up on the ferroelectric film 16. In addition to heat treatment after forming the ferroelectric 16, a prepared structure 22 is heat-treated again.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a ferroelectric memory and a method of manufacturing the same.

[0002]

2. Description of the Related Art When a ferroelectric film is used as a ferroelectric memory or other electronic device, it is not used by itself but as a sandwich structure in which upper and lower parts are sandwiched by electrodes. An electric field is applied to the ferroelectric film by the upper electrode and the lower electrode to control the magnitude and direction of polarization (spontaneous polarization) formed in the ferroelectric film. In general, the polarization phenomenon of a ferroelectric substance is accompanied by a history, and the relationship of the polarization with respect to the electric field in the ferroelectric substance is that the horizontal axis is the electric field,
It is known that the graph draws a hysteresis curve when the vertical axis represents the polarization amount. The response of this polarization to an electric field and its holding ability have been applied as a memory.

Regarding the recent trend of ferroelectric memories,
For example, the document “Ceramics, Vol. 30, No. 6,
pp. 499-507 (1995) "and the document" Ferroelectric thin film memory, Science Forum Co., Ltd., 199 ".
5 ”.

[0004]

However, the conventional ferroelectric memory has a problem that the symmetry of the shape of the hysteresis curve of polarization with respect to the applied electric field is not sufficient. Therefore, the positive / negative (direction) of the applied voltage
There is a difference in the absolute value of the amount of polarization formed in the ferroelectric film, so the level as digital data is not constant when reading or writing data, and it is necessary to set a large data judgment range. There are restrictions.

Therefore, conventionally, a ferroelectric memory having a good symmetry of the hysteresis curve and a manufacturing method for obtaining such a ferroelectric memory have been desired.

[0006]

According to the ferroelectric memory of the present invention, in order to solve the above-mentioned problems, an upper electrode and a lower electrode, and a ferroelectric sandwiched between these upper electrode and the lower electrode. In a ferroelectric memory having a body film, the interface structure between the upper electrode and the ferroelectric film and the interface structure between the lower electrode and the ferroelectric film are the same or substantially the same.

Here, "homogeneous" means that any part of one object is macroscopically physically and chemically equivalent, and "substantially homogeneous" is not homogeneous. Let's say that it is in a state that can be regarded as homogeneous.

The deterioration of the symmetry of the hysteresis curve is considered to be due to the difference in structure between the interface between the ferroelectric film and the upper electrode and the interface between the ferroelectric film and the lower electrode.
Further, it is considered that the difference in the interface structure is caused by the difference in the manufacturing method and the manufacturing conditions. By eliminating the difference in the physical properties and the chemical properties of these two interfaces, the symmetry of the hysteresis curve is improved. Is possible.

According to the method of manufacturing a ferroelectric memory of the present invention, in order to solve the above-mentioned problems, in the method of manufacturing a ferroelectric memory, (a) a preliminary ferroelectric film is formed on the lower electrode. Forming to obtain a combination of both,
(B) subjecting this combination to a heat treatment (first heat treatment) to change the preliminary ferroelectric film into a ferroelectric film;
(C) a step of forming an upper electrode on the ferroelectric film to obtain a structure in which the ferroelectric film is sandwiched between the upper electrode and the lower electrode; and (d) heat treatment ( (2) heat treatment).

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described below with reference to the drawings. It should be noted that the drawings are only schematically shown to the extent that the present invention can be understood, and the numerical and other conditions described below are mere preferred examples, and the present invention is embodied in the embodiments of the present invention. It is not limited to the above.

FIG. 1 is a sectional view of the structure of a ferroelectric memory for explaining the structure of the embodiment of the present invention.

First, the ferroelectric memory of the present invention is a ferroelectric memory having an upper electrode, a lower electrode, and a ferroelectric film sandwiched between the upper electrode and the lower electrode. It is characterized in that the interface structure with the dielectric film and the interface structure with the lower electrode and the ferroelectric film are the same or substantially the same.

In the embodiment of the present invention, the base 10 is covered with the oxide film 12, and the upper electrode 20, the lower electrode 14, and the upper electrode 2 are provided on the base, that is, the oxide film 12.
A ferroelectric film 16 sandwiched between 0 and the lower electrode 14 is formed. The interface structure between the upper electrode 20 and the ferroelectric film 16 and the lower electrode 14 and the ferroelectric film 16 are also described.
The interface structure with and is substantially the same.

In the embodiment of the present invention, the substrate 1
A silicon substrate which is a silicon (Si) wafer is used as 0, and a silicon oxide (SiO ₂ ) film is used as the oxide film 12. The upper electrode 20 and the lower electrode 14 are both formed of platinum (Pt), and the ferroelectric film 16 is formed of P (Pt).
It is formed of LZT (Pb _1.1 La _0.03 Zr _0.5 Ti _0.5 O ₃ ).

FIG. 2 is a view for explaining the manufacturing method according to the embodiment of the present invention, and each drawing is a cross section of the structure obtained at each process step.

According to the method of manufacturing the ferroelectric memory of the present invention, first, the preliminary ferroelectric film 16 is formed on the lower electrode 14 to obtain a combination 18 of the both (FIG. 2C).

Therefore, first, in the embodiment of the present invention, a silicon (Si) substrate 10 is used as a substrate, and this is subjected to, for example, thermal oxidation treatment, and a silicon oxide (SiO ₂ ) film 12 as an insulating film is formed on the substrate surface. Are formed ((A) of FIG. 2). In the embodiment of the present invention, as an example, the film thickness of the silicon oxide film 12 is set to 0.3 μm.

Next, a platinum film is formed on the silicon oxide film 12 by, for example, a sputtering method and is used as the lower electrode 14 ((B) of FIG. 2). In the embodiment of the present invention, as an example, the film thickness of the lower electrode 14 is set to 0.06 μm.

Next, a preliminary ferroelectric film 16 of PLZT is formed on the lower electrode 14 to obtain a combined body 18 (FIG. 2).
(C)).

Generally, in this case, the ferroelectric film 16 is formed in the following order. (1) A PLZT forming solution is spin-coated on a platinum film to form a coating film. (2) The coating film is dried at 150 ° C. for 30 minutes. (3) The dried coating film is pre-baked at 460 ° C. for 30 minutes to form a preliminary ferroelectric film of PLZT.

Here, the spin coating in the step (1) is
PLZT (Pb _1.1 La _0.03 Zr _0.5 Ti on the platinum film
_0.5 O ₃ ) forming solution (trade name “metal polymer solution” manufactured by Epoxy Technology Co., Ltd.) is dropped, and the substrate is immediately rotated on an axis perpendicular to the surface and blown off by the centrifugal acceleration.

In the embodiment of the present invention, the rotation speed of the substrate is 500 rpm for 5 seconds, and 2000 rpm is 30 rpm.
Seconds. In this way, first of all, PL is spun on the substrate at low speed.
The ZT forming liquid is made to fit in, and then the excess forming liquid is blown off at high speed to form a film.

Next, in the process of (2), the solvent in the PLZT film is evaporated and the organic functional groups are burned. And
By the process of (3), the organic functional groups remaining in the PLZT film are burned and the PLZT film is pre-baked.

The above (1) to (3) were repeated 4 times to adjust the film thickness. In addition, since calcination with a required film thickness at one time will cause cracking, it is necessary to divide into several times to avoid this. In the embodiment of the present invention, the thickness of the ferroelectric film 16 is 0.38 μm.

Then, in the present invention, the first heat treatment is performed on the combined body having the preliminary ferroelectric film. Therefore, in this embodiment, this first heat treatment is mainly performed as firing for the preliminary ferroelectric film 16. This firing is performed in the air at 650 ° C. for 60 minutes to fire and crystallize the PLZT film to change the preliminary ferroelectric film into the ferroelectric film. In the figure, the ferroelectric film is shown by the same reference numeral 16 as the preliminary ferroelectric film 16.

After forming the ferroelectric film 16 as described above, in the present invention, the upper electrode 20 is formed on the ferroelectric film 16 to obtain the structure 22 ((D) of FIG. 2). In this case, in the embodiment of the present invention, a platinum film is formed as the upper electrode 18 by, for example, the sputtering method. Then, the film thickness of the upper electrode 20 is set to 0.3 μm as an example. Further, the electrode shape is cylindrical, and its diameter is, for example, 1 mm.

Finally, in the present invention, the structure 22 produced in the above steps is subjected to the heat treatment again. This heat treatment is called "second heat treatment". In this embodiment, the second heat treatment is performed in the air at 650 ° C. for 60 minutes.

The heat treatment temperature and the heat treatment time of the first and second heat treatments mentioned above may be appropriately determined on the basis of the thermal analysis data. Although each heat treatment in the embodiment of the present invention is performed in the air, it may be performed in an oxygen atmosphere.

Next, the characteristics of the prepared ferroelectric memory will be described. FIG. 3 is a diagram schematically showing the relationship between the applied voltage V and the polarization amount P formed in the ferroelectric film.
The horizontal axis represents the voltage value V of the upper electrode 20 when the lower electrode 14 is used as a reference, and the vertical axis represents the polarization amount P for each voltage value V. Coordinate point F from point A, respectively _{A (V max, P max)} B (0, P r) C (-V c, 0) D (-V max, -P max) E (0, -P r ) F (V _c , 0). The arrow in the figure indicates that the polarization state of the ferroelectric film changes in the direction of the arrow. For example, starting from point A, A → B → C → D → E → F → A. It shows that it is a changing PV hysteresis curve. In the figure,
The maximum value of the applied voltage in the positive direction is V _max, and the polarization amount corresponding to V _max is the maximum polarization amount P _max . The maximum value of the applied voltage in the negative direction is −V _max, and the polarization amount corresponding to −V _max is −P _max . Further, the values of the polarization amount when the applied voltage is zero are the residual polarization amounts P _r and −P _r . Further, the polarization amount is coercive electric field V _c the value of the applied voltage when the zero and -V _c. When the value of the maximum applied voltage V _max is different when measuring the hysteresis curve, the size and shape of the hysteresis curve, that is, the maximum polarization amount P depending on the value of the V _max.
The values of _max , the residual polarization amount P _r , and the coercive electric field V _c change. The data of FIGS. 4 to 8 shown below are the maximum applied voltage V _max.
The hysteresis curve is measured by changing the value of, and the physical quantity such as the residual polarization amount and the coercive electric field is measured from each of the hysteresis curves, and these are plotted on the vertical axis and the value of V _{max on} the horizontal axis. is there.

FIG. 4 shows the maximum voltage value V _max (unit: volt (V)) applied to the ferroelectric film and the polarization amount P _max (unit: μC / cm) formed in the ferroelectric film at that time. It is a figure which shows the relationship with ² ). As described in FIG. 3, from the P-V hysteresis curve was measured by varying the maximum applied voltage V _max, reads the amount of polarization P _max for V _max, it took P _max on the horizontal axis V _max, the vertical axis It is a thing.

In the figure, the data points represented by the circles are the case where only the first heat treatment was applied, and the data points represented by the diamonds were the both the first heat treatment and the second heat treatment. This is the case (this symbol is used in FIGS. 4 to 8). Thus, it can be seen that the relationship between V _max and P _max increases linearly in both cases and there is almost no difference, and they can be approximated by a common straight line. Therefore, it is understood that the second polarization has no effect on the maximum polarization amount.

FIG. 5 is a diagram showing the relationship between the maximum applied voltage V _max (unit: volt (V)) and the residual polarization amount P _r (unit: μC / cm ² ).

In FIG. 5A, the maximum voltage value V
_The voltage was gradually lowered from _max, and the value of the polarization amount when the voltage became zero was defined as P _r . That is, in FIG. 3, the state of the point A is changed to the state of the point B, and the value of the polarization amount at the point B is set to P _r . On the other hand, (B) of FIG.
The voltage is changed from V _max (state at point D in FIG. 3) toward zero, and the value of the amount of polarization when the voltage becomes zero (state at point E in FIG. 3) is −P _r . Similar to FIG. 4, the residual polarization amount P _r is read from each PV hysteresis curve measured by changing the maximum applied voltage V _max , and V _{ab is} plotted on the horizontal axis and P _r is plotted on the vertical axis.

In FIG. 5 (A), when the maximum applied voltage V _max is around 7 (V) and above, only the first heat treatment is performed (curve indicated by a circle), the first heat treatment and the first heat treatment. There is a large difference from the case where both the heat treatment and the heat treatment (curve indicated by ⋄) are performed.
In addition, in FIG. 5B, the maximum applied voltage is 2
The difference between the two is large except near (V). 5A and 5B are compared with respect to the curve indicated by a circle, the shapes of the curves are different, and the magnitude of the applied voltage required to cancel the polarization having the same magnitude and opposite direction. Show that they are very different. On the other hand, when the curves indicated by ⋄ are compared between FIGS. 5A and 5B, the shapes of the curves are similar to each other, and there is no great difference even when the magnitudes of the data values are compared. Therefore, when both the first heat treatment and the second heat treatment are performed, P-V is higher than that when only the first heat treatment is performed.
The hysteresis curve has good symmetry.

FIG. 6 shows the coercive electric field V _c (unit: volt (V)) with respect to the maximum applied voltage V _max (unit: volt (V)).
It is a figure which shows the relationship of.

FIG. 6A shows -V _max (point D in FIG. 3).
Was changed toward zero from 0 to 0, and the value of the applied voltage when the polarization amount became zero (point F in FIG. 3) was defined as V _c .
Further, in FIG. 6B, the applied voltage is lowered from the state of V _max (point A in FIG. 3) and the polarization amount is zero (C in FIG. 3).
The value of the applied voltage when it is the point) was -V _c. V
By changing the value of _max and measuring the hysteresis curve, V _max
Are plotted on the horizontal axis and V _c for each is plotted on the vertical axis.

In both of FIGS. 6A and 6B, the case where only the first heat treatment is applied (curve with a circle) and the case where both the first heat treatment and the second heat treatment are performed (marked with ⋄) Curve) and the situation is very different. Also, the curve indicated by ⋄ can be approximated by a straight line, but the curve indicated by ∘ has a large variation in data and poor continuity. Comparing (A) and (B) of FIG. 6 with respect to the curve indicated by a circle, the shapes of the curves are significantly different, and the voltage required to cancel the polarization formed in the ferroelectric film is applied. The magnitude of the voltage depends on the direction of its polarization. On the other hand, ◇
Comparing (A) and (B) of FIG. 6 with respect to the curve indicated by a mark, the shapes of both curves can be approximated by a straight line, and there is no great difference even if the magnitudes of the data values are compared. Therefore, when both the first heat treatment and the second heat treatment are performed, the symmetry of the shape of the PV hysteresis curve is better than when only the first heat treatment is performed.

FIG. 7 is a graph showing the relationship between the maximum applied voltage V _max (unit: volt (V)) and the residual polarization amount P _r (unit: μC / cm ² ). It is the figure which plotted the data of B) on the same graph.

The horizontal axis of FIG. 7 represents the maximum applied voltage V _max ,
The vertical axis represents the residual polarization amount P _r . In the figure, the ○ and ◇ marks
Corresponding to the data represented by the ○ and ◇ marks in FIG. 5A, the △ and □ marks are the ○ and ◇ marks in FIG. 5B. Corresponds to the data represented. Thus, by comparing the difference between the ⋄ and □ marks and the difference between the ○ and Δ marks, it can be clearly seen that the former is smaller than the latter. In addition, the curve represented by ○ has only a positive slope, whereas the curve represented by Δ has V _max of 2 (V) to 5
It can be seen that the region (V) has a negative slope. As described above, when only the first heat treatment is performed, the ferroelectric characteristics differ according to the direction of the applied voltage. On the other hand, ◇ and □
It can be said that there is no great difference in the ferroelectric characteristics according to the direction of the applied voltage when the curve represented by the mark, that is, when the second heat treatment is performed in addition to the first heat treatment. Therefore, the symmetry of the shape of the PV hysteresis curve is better when the second heat treatment is performed in addition to the first heat treatment than when only the first heat treatment is performed.

FIG. 8 is a diagram showing the relationship between the maximum applied voltage V _max (unit: volt (V)) and the coercive electric field V _c (unit: volt (V)). It is the figure which plotted the data of) on the same graph.

The horizontal axis of FIG. 8 represents the maximum applied voltage V _max ,
The vertical axis represents the coercive electric field V _c . In the figure, the ○ and ◇ marks indicate
Corresponding to the data indicated by ○ and ◇ in (A), △ and □ are indicated by ○ and ◇ in (B) of FIG. Corresponding data. Thus, by comparing the difference between the ⋄ and □ marks and the difference between the ○ and Δ marks, it can be clearly seen that the former is smaller than the latter. Also, in terms of continuity, the former is superior to the latter, and the data represented by ◯ marks and Δ marks are on a common straight line. Therefore, it can be said that the variation in the ferroelectric characteristics is much smaller in the case of performing the second heat treatment in addition to the first heat treatment than in the case of only the first heat treatment, depending on the direction of the applied voltage. The symmetry of the shape of the PV hysteresis curve is also better when the second heat treatment is performed in addition to the first heat treatment.

Numerical values of the data shown in FIGS. 4 to 8 are shown in Tables 1 to 5. (A) of Table 1 is the first of FIG.
9 is a table showing numerical values of data (indicated by circles) when only heat treatment is performed. (B) of Table 1 is a table showing numerical values of data (indicated by ⋄) when the second heat treatment of FIG. 4 is performed.

Table 2 (a) is a table showing numerical values of data (indicated by a circle) when only the first heat treatment of FIG. 5 (A) is performed. (B) of Table 2 is the second of (A) of FIG.
6 is a table showing numerical values of data (indicated by ⋄) when heat treatment is performed.

Table (3) (b) is a table showing numerical values of data (indicated by ◯) when only the first heat treatment of FIG. 5 (B) is performed. (B) of Table 3 is the second of (B) of FIG.
6 is a table showing numerical values of data (indicated by ⋄) when heat treatment is performed.

Table 4 (a) is a table showing numerical values of data (indicated by a circle) when only the first heat treatment of FIG. 6 (A) is performed. (B) of Table 4 is the second of (A) of FIG.
6 is a table showing numerical values of data (indicated by ⋄) when heat treatment is performed.

Table (a) of Table 5 is a table showing numerical values of data (indicated by a circle) when only the first heat treatment of FIG. 6 (B) is performed. (B) of Table 5 is the second of (B) of FIG.
6 is a table showing numerical values of data (indicated by ⋄) when heat treatment is performed.

Further, in FIG. 7, the circles and the diamonds in the figure correspond to the data represented by the circles and the diamonds shown in FIG. And correspond to the data represented by the circles and the diamonds in FIG. 5B. Therefore, the numerical values of each data are shown in Tables 2 and 3.

Further, in FIG. 8, the circles and the diamonds in the figure correspond to the data represented by the circles and the diamonds shown in FIG. 6A, and the triangles and the squares. And correspond to the data represented by the circles and the diamonds in FIG. 6B. Therefore, the numerical values of each data are shown in Tables 4 and 5.

[0049]

[Table 1]

[0050]

[Table 2]

[0051]

[Table 3]

[0052]

[Table 4]

[0053]

[Table 5]

The ferroelectric memory of the present invention is a ferroelectric memory having an upper electrode, a lower electrode, and a ferroelectric film sandwiched between the upper electrode and the lower electrode. It is characterized in that the interface structure with the film and the interface structure between the lower electrode and the ferroelectric film have the same or substantially the same quality.

The deterioration of the symmetry of the P-V hysteresis curve of the ferroelectric film is caused by the difference in structure between the interface between the ferroelectric film and the upper electrode and the interface between the ferroelectric film and the lower electrode, that is, physical. It is believed that this is due to the difference in physical properties and chemical properties. Further, it is considered that the difference in the interface structure is caused by the difference in the manufacturing method and the manufacturing conditions when forming each interface. Therefore, it is possible to improve the symmetry of the hysteresis curve by forming these two interfaces to have the same or substantially the same quality and eliminating the difference in physical properties and chemical properties. In the above-described embodiment, by performing the second heat treatment in addition to the first heat treatment, the formation conditions of each interface are made the same or substantially the same, and as a result,
The two interfaces are considered to be homogeneous or substantially homogeneous.

Next, a case where a ferroelectric substance other than PLZT is used as the ferroelectric film 16 will be described.

When a lead-containing ferroelectric substance such as PZT or PTO is used as the ferroelectric film 16, 400 ° C. to 7 ° C.
It is desirable to determine the first heat treatment temperature and the second heat treatment temperature in the temperature range of 00 ° C. In order to obtain good characteristics as a ferroelectric substance, it is desirable to perform heat treatment at a high temperature, but in this case, lead evaporates at 700 ° C. or higher, so it is determined from the above temperature range. On the contrary, in the process of forming the ferroelectric film, at least 400 ° C. is required to evaporate the organic functional groups remaining in the ferroelectric film, so the above temperature range is set.

When a lead-free ferroelectric substance such as a Bi layered compound is used as the ferroelectric film 16, the first heat treatment temperature and the second heat treatment temperature are set in the temperature range of 700 ° C. to 900 ° C. To decide. In this case, the heat treatment can be performed at a relatively high temperature without considering the evaporation of lead. Further, since it is difficult to crystallize the Bi layered compound outside this temperature range, the above temperature range is provided.

Ferroelectric substances other than PLZT are
Even when used as the ferroelectric film 16, it has been confirmed that the symmetry of the shape of the PV hysteresis loop is good.

The embodiments of the present invention have been described above. According to the embodiment of the present invention, the symmetry of the shape of the PV hysteresis curve is improved as compared with the conventional one. That is, the difference in the absolute value of the polarization amount formed in the ferroelectric film due to the positive / negative (direction) of the applied voltage is small, and the level as digital data at the time of reading or writing data is constant, There is no need to set a large data judgment range. Therefore, it can be seen that the application as the ferroelectric memory is further facilitated, the performance is improved, and the range of use is expanded.

[0061]

As is clear from the above description, according to the ferroelectric memory of the present invention, the interface structure between the upper electrode and the ferroelectric film and the interface structure between the lower electrode and the ferroelectric film are provided. Are the same or substantially the same, the polarization amount P formed in the ferroelectric film with respect to the applied voltage V has good symmetry in the shape of the PV hysteresis curve, and as a result, the positive / negative of the applied voltage ( The difference in the absolute value of the amount of polarization formed in the ferroelectric film becomes extremely small depending on the (orientation), the level as digital data during data read or write operation is constant, and the data judgment range is large. There is no need, and therefore, the application as a ferroelectric memory is further facilitated, its performance is improved, and the range of utilization is expanded, which is a significant effect.

Further, according to the method of manufacturing the ferroelectric memory of the present invention, as a result of adding the step of performing the second heat treatment in addition to the conventional manufacturing step, as described above, the upper electrode and the ferroelectric film are formed. A ferroelectric memory having the same or substantially the same interfacial structure as in (1) and the interfacial structure between the lower electrode and the ferroelectric film can be obtained, and therefore, the above-described effects can be obtained.

[Brief description of drawings]

FIG. 1 is a cross-sectional view for explaining a configuration of an embodiment of the present invention.

FIG. 2 is a cross-sectional view for explaining the manufacturing method according to the embodiment of the present invention.

FIG. 3 is a diagram showing a relationship between an applied voltage and a polarization amount.

FIG. 4 is a diagram showing a relationship between a maximum applied voltage and a maximum polarization amount.

5A is a diagram showing the relationship between the maximum applied voltage and the residual polarization amount (the residual polarization amount at point B in FIG. 3), FIG.
FIG. 4B is a diagram showing the relationship between the maximum applied voltage and the residual polarization amount (the residual polarization amount at point E in FIG. 3).

6A is a diagram showing the relationship between the coercive electric field (coercive electric field at point F in FIG. 3) with respect to the maximum applied voltage, and FIG. 6B is the coercive electric field with respect to the maximum applied voltage (resistive field at point C in FIG. 3). It is a figure which shows the relationship of (electric field).

FIG. 7 is a diagram showing the relationship between the maximum applied voltage and the residual polarization amount.

FIG. 8 is a diagram showing a relationship between a maximum applied voltage and a coercive electric field.

[Explanation of symbols]

 10: Silicon Substrate 12: Silicon Oxide Film 14: Lower Electrode 16: Ferroelectric Film 18: Combination 20: Upper Electrode 22: Structure

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI technical display location H01L 29/788 29/792

Claims (5)

[Claims] 1. A ferroelectric memory having an upper electrode, a lower electrode, and a ferroelectric film sandwiched between the upper electrode and the lower electrode, wherein an interface structure between the upper electrode and the ferroelectric film is provided. And the interface structure between the lower electrode and the ferroelectric film is the same or substantially the same. 2. A method of manufacturing a ferroelectric memory, comprising:
(A) a step of forming a preliminary ferroelectric film on the lower electrode to obtain a combination of both, and (b) a heat treatment (first heat treatment) on the combination to enhance the preliminary ferroelectric film. Changing to a dielectric film; and (c) forming an upper electrode on the ferroelectric film to obtain a structure in which the ferroelectric film is sandwiched between the upper electrode and the lower electrode, (D) a step of subjecting the structure to a heat treatment (second heat treatment), a method of manufacturing a ferroelectric memory. 3. The method of manufacturing a ferroelectric memory according to claim 2, wherein the heat treatment temperature of the first heat treatment and the heat treatment temperature of the second heat treatment are the same temperature. Memory manufacturing method. 4. The method of manufacturing a ferroelectric memory according to claim 3, wherein when the ferroelectric film is a lead-containing ferroelectric substance, the first heat treatment and the second heat treatment are 400 times.
A method for manufacturing a ferroelectric memory, which is performed at a heat treatment temperature in the range of ℃ to 700 ℃. 5. The method of manufacturing a ferroelectric memory according to claim 3, wherein the first heat treatment and the second heat treatment are performed when the ferroelectric film is a lead-free ferroelectric substance.
A method for manufacturing a ferroelectric memory, which is performed at a heat treatment temperature in the range of 0 ° C to 900 ° C.