JP4761031B2 - Ferroelectric capacitor, method of manufacturing the same, and ferroelectric memory device - Google Patents

Description

  The present invention relates to a ferroelectric capacitor, a method for manufacturing the same, and a ferroelectric memory device.

  A ferroelectric memory device (FeRAM) is a non-volatile memory capable of low voltage and high speed operation, and a memory cell can be composed of one transistor / one capacitor (1T / 1C), so that it can be integrated like a DRAM. Therefore, it is expected as a large-capacity nonvolatile memory.

In order to maximize the ferroelectric characteristics of the ferroelectric capacitor constituting the ferroelectric memory device, the crystal orientation of each layer constituting the ferroelectric capacitor is extremely important.
JP 2000-277701 A

  An object of the present invention is to provide a ferroelectric capacitor in which the crystal orientation of each layer constituting the ferroelectric capacitor is well controlled, a manufacturing method thereof, and a ferroelectric memory device.

  The ferroelectric capacitor of the present invention is provided on the first electrode provided above the first barrier layer, the ferroelectric film provided on the first electrode, and the ferroelectric film. The first barrier layer is amorphous.

  According to the ferroelectric capacitor of the present invention, since the first barrier layer is amorphous, it is possible to provide the first electrode that does not reflect the underlying crystal structure.

  Here, the ferroelectric capacitor of the present invention was provided on a plug.

  Here, in the ferroelectric capacitor of the present invention, the first barrier layer may be a nitride of titanium and aluminum. Since the material has an oxygen barrier property, it is suitable as the first barrier layer.

  Here, in the ferroelectric capacitor of the present invention, a crystalline second barrier layer can be provided between the first barrier layer and the first electrode. By providing the second barrier layer, the crystal orientation of the first electrode provided on the second barrier layer can be enhanced. As a result, a ferroelectric film having excellent crystal orientation can be provided, so that the ferroelectric capacitor of the present invention has excellent hysteresis characteristics.

  In this case, the second barrier layer may be an alloy made of titanium and aluminum. In this case, the second barrier layer may be a nitride of titanium and aluminum. Since these materials have oxygen barrier properties, they are suitable as the second barrier layer.

The manufacturing method of the ferroelectric capacitor of the present invention is as follows.
(A) forming a first barrier layer that is amorphous;
(B) forming a first electrode above the first barrier layer;
(C) forming a ferroelectric film on the first electrode;
(D) forming a second electrode on the ferroelectric film;
including.

  According to the method of manufacturing a ferroelectric capacitor of the present invention, the first electrode on which the lower layer crystal structure is not reflected is simplified by forming the first electrode above the amorphous first barrier layer. Can be formed.

  Here, in the method for manufacturing a ferroelectric capacitor according to the present invention, the first barrier layer can be formed on the plug in (a).

  Here, in the method for manufacturing a ferroelectric capacitor of the present invention, the first barrier layer is a nitride of titanium and aluminum, and in (a), the nitrogen partial pressure is 8% or more and less than 12%. In the atmosphere, the first barrier layer can be formed by a sputtering method.

  Here, in the method of manufacturing a ferroelectric capacitor according to the present invention, after (a), before (b), (e) a crystalline second barrier on the first barrier layer. The method may further include forming a layer.

  In this case, the second barrier layer may be an alloy made of titanium and aluminum. In this case, the second barrier layer is a nitride of titanium and aluminum. In (e), the second barrier layer is formed by sputtering in an atmosphere having a nitrogen partial pressure of 12% or more and 20% or less. Two barrier layers can be formed. Here, in (e), a seed layer made of an alloy of titanium and aluminum can be formed on the first barrier layer, and the second barrier layer can be formed in the presence of the seed layer.

  Here, in the method for manufacturing a ferroelectric capacitor according to the present invention, the first and second barrier layers are nitrides of titanium and aluminum, and in (a), the first nitrogen partial pressure is provided. In the first atmosphere, the first barrier layer is formed by a sputtering method. In (e), in the second atmosphere having a second nitrogen partial pressure lower than the first nitrogen partial pressure, titanium and A seed layer made of an alloy of aluminum is formed on the first barrier layer, and then in the presence of the seed layer in a third atmosphere having a third nitrogen partial pressure greater than the first nitrogen partial pressure. The second barrier layer can be formed by sputtering. According to the above method, the first barrier layer, the seed layer, and the second barrier layer can be sequentially formed by changing the nitrogen partial pressure in the atmosphere. That is, the layers can be formed by a simple method of controlling the nitrogen partial pressure.

  In this case, the first nitrogen partial pressure in the first atmosphere is 8% or more and less than 12%, the second nitrogen partial pressure in the second atmosphere is less than 8%, The third nitrogen partial pressure in the atmosphere 3 can be 12% or more and 20% or less.

  A ferroelectric memory device of the present invention includes a switching transistor, a plug electrically connected to the switching transistor, and the ferroelectric capacitor of the present invention provided on the plug.

  According to the ferroelectric memory device of the present invention, since the ferroelectric capacitor of the present invention provided on the plug is included, the crystal structure of the conductive layer constituting the plug is not reflected. An electrode is provided. Accordingly, since the ferroelectric film having excellent crystal orientation is provided on the first electrode, the hysteresis characteristics are excellent.

  Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings.

1. Ferroelectric Memory Device FIG. 1 is a cross-sectional view schematically showing a ferroelectric memory device 100 according to an embodiment of the present invention. As shown in FIG. 1, the ferroelectric memory device 100 includes a ferroelectric capacitor 30, a plug 20, and a switching transistor 18 of the ferroelectric capacitor 30. Note that in this embodiment, a 1T / 1C type memory cell is described, but the present invention is not limited to a 1T / 1C type memory cell.

  The transistor 18 includes a gate insulating layer 11, a gate conductive layer 13 provided on the gate insulating layer 11, and first and second impurity regions 17 and 19 which are source / drain regions. The plug 20 is electrically connected to the switching transistor 18.

  The ferroelectric capacitor 30 is provided on the first electrode 32 provided above the first barrier layer 12, the ferroelectric film 34 provided on the first electrode 32, and the ferroelectric film 34. Second electrode 36 formed. The first barrier layer 12 is amorphous. More specifically, the ferroelectric capacitor 30 is provided on the first and second barrier layers 12 and 14.

  The ferroelectric capacitor 30 is provided on the plug 20 provided on the insulating layer 26. The plug 20 is formed on the second impurity region 19. The plug 20 includes an opening 24 and a conductive layer 22 provided in the opening 24. The conductive layer 22 is made of, for example, a refractory metal such as tungsten, molybdenum, tantalum, titanium, or nickel, and is preferably made of tungsten.

The first barrier layer 12 is at least partially provided on the plug 20. The first barrier layer 12 is made of a material having an oxygen barrier property, and is not particularly limited as long as it is amorphous. More preferably (TiAlN). When the first barrier layer 12 is made of TiAlN, the composition (atomic ratio) of titanium, aluminum, and nitrogen in the first barrier layer 12 is the chemical formula of Ti _(1-x) Al _x N _y . In this case, 0 <x ≦ 0.4 and 0 <y. In order not to be affected by the crystal structure of the lower layer, the film thickness of the first barrier layer 12 is preferably at least 20 nm, and more preferably, for example, 100 to 200 nm.

The second barrier layer 14 is provided on the first barrier layer 12, and the first electrode 32 is provided on the second barrier layer 14. The second barrier layer 14 is made of a material having an oxygen barrier property, and is not particularly limited as long as it is crystalline. More preferably, it is an alloy or a nitride of titanium and aluminum. Moreover, when the 2nd barrier layer 14 consists of TiAlN, it is preferable that the crystal orientation of the 2nd barrier layer 14 is (111) orientation. When the second barrier layer 14 is made of TiAlN, the composition (atomic ratio) of titanium, aluminum, and nitrogen in the second barrier layer 14 is the same as the composition of the second barrier layer 14 Ti _(1-x) Al _x N _y. In the chemical formula, 0 <x ≦ 0.4 and 0 <y. In order to control the orientation of the first electrode 32, the thickness of the second barrier layer 14 is preferably at least 20 nm, and more preferably, for example, 100 to 200 nm.

  The first electrode 32 can be made of at least one metal selected from platinum, ruthenium, rhodium, palladium, osmium, and iridium, preferably made of platinum or iridium, and more preferably made of iridium. The first electrode 32 may be a single layer film or a laminated multilayer film. When at least a part of the first electrode 32 a is crystalline, it is preferable that the crystalline orientation in the crystalline is equal to the crystalline orientation of the second barrier layer 14. In this case, it is preferable that the crystal orientation of the ferroelectric film 34 is equal to the crystal orientation of the crystalline material of the first electrode 32a. For example, when the second barrier layer 14 is made of TiAlN and the crystal orientation of the second barrier layer 14 is (111) orientation, at least a part of the first electrode 32 is crystalline, and the crystal orientation is (111). The orientation is preferable. According to this configuration, when the ferroelectric film 34 is formed on the first electrode 32, the crystal orientation of the ferroelectric film 34 can be easily set to the (111) orientation.

The ferroelectric film 34 includes a ferroelectric material. This ferroelectric material has a perovskite crystal structure and can be represented by the general formula A _1-b B _1-a X _a O ₃ . A includes Pb. Here, a part of Pb can be replaced with La. B consists of at least one of Zr and Ti. X consists of at least one of V, Nb, Ta, Cr, Mo, W, Ca, Sr, and Mg. As the ferroelectric substance contained in the ferroelectric film 102, a known material that can be used as a ferroelectric film can be used. For example, (Pb (Zr, Ti) O ₃ ) (PZT), SrBi can be used. ₂ Ta ₂ O ₉ (SBT), (Bi, La) ₄ Ti ₃ O ₁₂ (BLT).

  Among these, the material of the ferroelectric film 34 is preferably PZT. In this case, the first electrode 32 is more preferably iridium from the viewpoint of device reliability.

  Further, when PZT is used as the ferroelectric film 34, it is more preferable that the content of titanium in the PZT is greater than the content of zirconium in order to obtain a larger amount of spontaneous polarization. PZT having such a composition belongs to a tetragonal crystal, and its spontaneous polarization axis is c-axis. However, since an a-axis orientation component orthogonal to the c-axis is present at the same time, when PZT is c-axis oriented, this a Since the axial alignment component does not contribute to polarization reversal, the ferroelectric characteristics may be impaired. On the other hand, by making the crystal orientation of PZT used for the ferroelectric film 34 the (111) orientation, the a-axis orientation component can contribute to the polarization inversion. Therefore, when the ferroelectric film 34 is made of PZT and the titanium content in the PZT is larger than the zirconium content, the crystal orientation of the PZT is preferably the (111) orientation in terms of good hysteresis characteristics. .

  The second electrode 36 can be made of the above-described materials exemplified as materials usable for the first electrode 32, or can be made of aluminum, silver, nickel, or the like. The second electrode 36 may be a single layer film or a laminated multilayer film. Preferably, the second electrode 36 is made of platinum or a laminated film of iridium oxide and iridium.

  According to the ferroelectric capacitor 30 of the present invention, the first electrode 32 is provided on the plug 20 via the first barrier layer 12 and the first barrier layer 12 is amorphous, so that the lower layer (plug 20 ), The first electrode 32 that does not reflect the crystal structure can be provided. That is, the ferroelectric capacitor 30 of the present embodiment is provided on the plug 20, but the first electrode 32 does not reflect the crystal structure of the lower layer (plug 20).

  Here, it is assumed that the first electrode 32 of the ferroelectric capacitor 30 is directly disposed on the conductive layer 22 of the plug 20. In this case, when the conductive layer 22 is made of a material having high crystallinity, the crystal orientation of the conductive layer 20 may affect the crystal orientation of the first electrode 32. For example, when the conductive layer 22 of the plug 20 is made of tungsten, since tungsten has high crystallinity, when the first electrode 32 is directly provided on the conductive layer 22 made of tungsten, the crystal structure of the conductive layer 22 is the first. It affects the crystal structure of the electrode 32 and makes it difficult to make the first electrode 32 have a desired crystal structure. Further, since the ferroelectric film 34 is provided on the first electrode 32, the crystal orientation of the first electrode 32 may affect the crystal orientation of the ferroelectric film 34. In this case, as a result of polarization occurring in an undesired direction due to the crystal orientation of the ferroelectric film 34 reflecting the crystal orientation of the first electrode 32, the hysteresis characteristics of the ferroelectric capacitor 30 may deteriorate.

  On the other hand, according to the ferroelectric capacitor 30 of the present embodiment, since the first barrier layer 12 is amorphous, the crystal orientation of the conductive layer 22 of the plug 20 changes between the first electrode 32 and the ferroelectric material. Reflecting the crystal orientation of the film 34 can be prevented. Thereby, the ferroelectric capacitor 30 having excellent hysteresis characteristics can be obtained.

  If the cross-sectional area of the plug 20 is the same, the smaller the plane area of the ferroelectric capacitor 30 is, the smaller the ratio of the plane area of the ferroelectric capacitor 30 to the cross-sectional area of the plug 20 is. Due to the crystal orientation of the layer 22, the problem of crystal orientation exerted from the first electrode 32 to the ferroelectric film 34 becomes serious. Therefore, according to the ferroelectric capacitor 30 of the present embodiment, it is useful in that it is possible to prevent a decrease in hysteresis characteristics even when it is further miniaturized for the reason described above.

  Further, according to the ferroelectric capacitor 30 of the present invention, the crystalline second barrier layer 14 is provided between the first barrier layer 12 and the first electrode 32. Thereby, the crystal orientation of the 1st electrode 32 provided on the 2nd barrier layer 14 can be improved. As a result, since the ferroelectric film 34 having excellent crystal orientation can be provided on the first electrode 32, the hysteresis characteristics are excellent.

  In particular, as described above, when the ferroelectric film 34 is made of PZT and the content of titanium in the PZT is larger than the content of zirconium, the crystal orientation of the PZT is (111) oriented in that the hysteresis characteristics are good. Is preferred. According to the ferroelectric capacitor 30 of the present embodiment, since the amorphous first barrier layer 12 is provided on the plug 20, the crystal orientation of the conductive layer 22 (tungsten) of the plug 20 is reflected on the upper layer. Can be prevented. Furthermore, according to the ferroelectric capacitor 30 of the present embodiment, since the second barrier layer 14 having the (111) orientation is provided, the crystals of the first electrode 32 and the ferroelectric film 34 are provided. It is easy to make the orientation (111) orientation. Thereby, the ferroelectric capacitor 30 of the present embodiment is excellent in hysteresis characteristics.

  Furthermore, according to the ferroelectric capacitor 30 of the present embodiment, since the barrier layer is a laminated film of the first and second barrier layers 12 and 14, the oxidation resistance can be ensured.

2. Method for Manufacturing Ferroelectric Memory Device Next, a method for manufacturing the ferroelectric memory device 100 shown in FIG. 1 will be described with reference to the drawings. 2A to 2F are cross-sectional views schematically showing one manufacturing process of the ferroelectric capacitor 30 included in the ferroelectric memory device 100 shown in FIG. 2A to 2F show only the vicinity of the insulating layer 26 and the plug 20 in the ferroelectric memory device 100 of FIG.

  First, the transistor 18 and the plug 20 are formed (see FIG. 1). More specifically, the transistor 18 is formed on the semiconductor substrate 10, and then the insulating layer 26 is stacked over the transistor 18. Next, an opening 24 is formed in the insulating layer 26, and the conductive layer 22 is embedded in the opening 24, thereby forming the plug 20. The conductive layer 22 can be embedded using, for example, a CVD method or a sputtering method.

  Next, the ferroelectric capacitor 30 is formed. The manufacturing method of the ferroelectric capacitor 30 according to the present embodiment includes (a) a step of forming the amorphous first barrier layer 12a, and (b) forming the first electrode 32a above the first barrier layer 12a. (C) forming a ferroelectric film 34a on the first electrode 32a, and (d) forming a second electrode 36a on the ferroelectric film 34a.

  First, as shown in FIG. 2A, the first barrier layer 12 a is formed on the insulating layer 26 and the plug 20. A method for forming the first barrier layer 12a can be appropriately selected depending on the material, and examples thereof include a sputtering method and a CVD method.

  For example, when the first barrier layer 12a made of nitride of titanium and aluminum is formed, the first barrier layer 12a can be formed by a sputtering method in a first atmosphere having a first nitrogen partial pressure. Note that the atmospheres (first to third atmospheres) used here are, for example, a mixture of nitrogen and an inert gas (for example, argon). Here, the first nitrogen partial pressure is preferably 8% or more and less than 12%. Here, if the first partial pressure of nitrogen is less than 8%, nitride cannot be obtained. On the other hand, if it exceeds 12%, crystalline nitride is generated.

  In addition, the substrate temperature at the time of forming the first barrier layer 12a is not particularly limited, and can be appropriately selected between room temperature and 400 ° C., for example.

  Next, as shown in FIG. 2B, a seed layer 14s is formed on the first barrier layer 12a. The seed layer 14s can be formed by the method exemplified as the method for forming the first barrier layer 12a, and the sputtering method is particularly preferable. The seed layer 14s is provided to form the crystalline second barrier layer 14, and is made of a crystalline material (crystal nucleus). The seed layer 14 s is not particularly limited as long as it is crystalline, but is preferably a material containing atoms constituting the second barrier layer 14. For example, when the second barrier layer 14 is made of TiAlN, the seed layer 14s can be made of TiAl.

  For example, when the seed layer 14s made of an alloy of titanium and aluminum is formed, the seed layer 14s is formed by a sputtering method in a second atmosphere having a second nitrogen partial pressure lower than the first nitrogen partial pressure. be able to. Here, the second nitrogen partial pressure is preferably less than 8%. When the second partial pressure of nitrogen is less than 8%, a crystalline seed layer 14s made of an alloy of titanium and aluminum can be obtained.

  Next, as shown in FIG. 2C, the second barrier layer 14a is formed in the presence of the seed layer 14s. A method for forming the second barrier layer 14a can be appropriately selected according to the material, and examples thereof include a sputtering method and a CVD method.

  For example, when the second barrier layer 14a made of titanium and aluminum nitride is formed, the second barrier layer is formed by sputtering in a third atmosphere having a third nitrogen partial pressure higher than the first nitrogen partial pressure. Layer 14a can be formed. Here, the third nitrogen partial pressure is preferably 12% or more and 20% or less. When the third partial pressure of nitrogen is within this range, TiAlN having a (111) orientation can be obtained. When the second barrier layer 14 a has the (111) orientation, the crystal orientation can be changed to the (111) orientation in at least a part of the first electrode 32. Thereby, the ferroelectric film 34 formed on the first electrode 32 can be (111) oriented.

  As described above, when the ferroelectric film 34 is made of PZT and the content of titanium in the PZT is larger than the content of zirconium, the crystal orientation of PZT is the (111) orientation in that the hysteresis characteristics are good. Is preferred. Therefore, by setting the crystal orientation of the second barrier layer 14a to the (111) orientation, both the first electrode 32a and the ferroelectric film 34a can be set to the (111) orientation. The capacitor 30 can be obtained.

  On the other hand, when the third nitrogen partial pressure exceeds 20%, (200) -oriented TiAlN is obtained, and when the third nitrogen partial pressure is 12% or less, amorphous TiAlN is obtained. Since the crystal orientation of the barrier layer 14a cannot be (111) orientation, it is not preferable.

  Alternatively, for example, when forming the second barrier layer 14a that is an alloy of titanium and aluminum, the second barrier layer 14a can be formed by a sputtering method in an atmosphere having a nitrogen partial pressure of less than 8%.

  In addition, the substrate temperature at the time of forming the second barrier layer 14a is not particularly limited, and can be appropriately selected between room temperature and 400 ° C., for example. A seed layer (not shown) may be formed on the second barrier layer 14a in order to improve the crystal orientation at the interface between the second barrier layer 14a and the first electrode 32a. For example, when the second barrier layer 14a is made of TiAlN, a layer made of Ti or TiN may be formed as a seed layer (not shown).

  Next, as shown in FIG. 2D, the first electrode 32a is formed on the second barrier layer 14a. Here, by forming the first electrode 32a on the crystalline second barrier layer 14a, the crystallinity of the first electrode 32a is remarkably improved and the crystal orientation of the second barrier layer 14a is improved. 32a can be reflected. For example, when the crystal orientation of the second barrier layer 14a is the (111) orientation, at least a part of the first electrode 32a can be formed in a crystalline material having the (111) orientation.

  A method for forming the first electrode 32a can be selected as appropriate according to the material of the first electrode 32a, and examples thereof include a sputtering method and a CVD method.

  Next, as shown in FIG. 2E, a ferroelectric film 34a is formed on the first electrode 32a. Here, by forming the ferroelectric film 34a on the first electrode 32a, the crystal orientation of the first electrode 32a can be reflected in the ferroelectric film 34a. For example, when at least a part of the first electrode 32a is crystalline having (111) orientation, the crystal orientation of the second barrier layer 14a can be formed in (111) orientation.

  A method of forming the ferroelectric film 34a can be selected as appropriate according to the material, and examples thereof include a spin-on method, a sputtering method, and an MOCVD method.

  Next, as shown in FIG. 2F, a second electrode 36a is formed on the ferroelectric film 34a. A method for forming the second electrode 36a can be appropriately selected according to the material of the second electrode 36a, and examples thereof include a sputtering method and a CVD method. Thereafter, a resist layer R1 having a predetermined pattern is formed on the second electrode 36a, and patterning is performed by photolithography using the resist layer R1 as a mask. Thus, the first electrode 32 provided on the first and second barrier layers 12, 14, the ferroelectric film 34 provided on the first electrode 32, and the ferroelectric film 34 are provided. A stacked ferroelectric capacitor 30 having the second electrode 36 is obtained (see FIG. 1).

  As described above, according to the method for manufacturing the ferroelectric capacitor 30 of the present embodiment, the lower electrode crystal structure is reflected by forming the first electrode 32a above the amorphous first barrier layer 12a. The first electrode 32a that is not formed can be formed by a simple method. Further, the method may further include a step of forming a crystalline second barrier layer 14a on the first barrier layer 12a.

3. Examples Hereinafter, the present invention will be described more specifically based on examples, but the present invention is not limited to these examples.

3.1. Example 1
In this embodiment, the transistor 18, the insulating layer 26, and the plug 20 are formed according to the steps shown in FIGS. 1 and 2A, and then the barrier layer (“barrier layer A”) on the plug 20 is formed. The optimum nitrogen partial pressure for the film formation was investigated.

  First, the transistor 18 was formed on the semiconductor substrate (silicon substrate) 10, and then the insulating layer 26 was stacked on the transistor 18. Next, an opening 24 is formed in the insulating layer 26, and the opening 24 is filled with tungsten by a CVD method, and then the tungsten above the surface of the insulating layer 26 is polished by chemical mechanical polishing, thereby providing a conductive layer. Layer 22 was formed. The plug 20 was formed by the above process (see FIG. 1).

  Next, a barrier layer A containing titanium and aluminum was formed on the insulating layer 26 and the plug 20 by sputtering. In this film forming step, the barrier layer A was formed by using a mixed gas of argon and nitrogen as an atmosphere, selecting titanium and aluminum as targets, and changing the nitrogen partial pressure. Here, conditions other than the nitrogen partial pressure were the same. The conditions other than the nitrogen partial pressure were an atmospheric flow rate of 50 [sccm], a deposition power of 1.0 [kW], and a substrate temperature of 400 [° C.].

  The XRD (X-ray diffraction) patterns of the barrier layer A formed at each nitrogen partial pressure are shown in FIGS. 3 (a) to 3 (f) and FIGS. 4 (a) to 4 (c). 3 (a) to 3 (f) and FIGS. 4 (a) to 4 (c), the nitrogen partial pressures are 0%, 6%, 8%, 10%, 12%, 14%, and 16%, respectively. , 20% and 40% of the XRD pattern of the barrier layer A formed in an atmosphere. In FIGS. 3A to 3F and FIGS. 4A to 4C, the peak observed in the vicinity of 2θ = 33 ° is Si of the substrate 10.

  According to FIG. 3A and FIG. 3B, a new peak was observed around 2θ = 37 ° in the barrier layer A formed in an atmosphere with a nitrogen partial pressure of 6%. This peak is presumed to be crystalline TiAl having a (111) orientation. Further, according to FIGS. 3C to 3E, no peak other than Si was observed in the barrier layer A formed in an atmosphere having a nitrogen partial pressure of 8% and 10%. Therefore, it is estimated that the barrier layer A formed in an atmosphere with a nitrogen partial pressure of 8% and 10% is amorphous TiAlN.

  Further, according to FIGS. 3 (e), 3 (f), 4 (a), and 4 (b), the nitrogen partial pressure is 12%, 14%, 16%, and 20%. In the formed barrier layer A, a new peak was observed around 2θ = 37.4 °. This peak is presumed to be crystalline TiAlN having a (111) orientation.

  Note that, according to FIG. 4C, in the barrier layer A formed in an atmosphere having a nitrogen partial pressure of 40%, a new peak appears at 2θ = 43.5 °, along with a peak near 2θ = 37.4 °. A strong peak was observed. This peak is presumed to be crystalline TiAlN having a (200) orientation.

  From the above results, when the nitrogen partial pressure in the atmosphere is less than 8%, a crystalline layer made of TiAl can be formed, and when the nitrogen partial pressure in the atmosphere is 8% or more and less than 12%, When the nitrogen partial pressure in the atmosphere is 12% or more and 20% or less, a crystalline layer made of TiAlN having (111) orientation can be formed, and the nitrogen partial pressure in the atmosphere is 20%. It has been clarified that a crystalline layer made of TiAlN having a (200) orientation is formed when the content exceeds 100%. In particular, when the nitrogen partial pressure in the atmosphere was 16%, it was revealed that the crystalline orientation of the crystalline layer made of TiAlN having (111) orientation was the best.

  A crystalline layer made of TiAl is suitable for the seed layer 14s of FIG. 2B, and an amorphous layer made of TiAlN is suitable for the first barrier layer 12a of FIG. 2A, and TiAlN having a (111) orientation. It is estimated that the crystalline layer made of is suitable for the second barrier layer 14a of FIG.

  Therefore, in order to form the amorphous first barrier layer 12a (see FIG. 2A), it was confirmed that the nitrogen partial pressure in the atmosphere is preferably 8% or more and less than 12% ( (Refer FIG.3 (c)-FIG.3 (e)). Further, since the crystalline layer made of TiAl was obtained by making the nitrogen partial pressure in the atmosphere less than 8%, in order to form the seed layer 14s made of TiAl (see FIG. 2B), It was confirmed that the nitrogen partial pressure in the atmosphere is preferably less than 8% (see FIGS. 3A to 3C). Furthermore, in order to form the crystalline second barrier layer 14 made of TiAlN having (111) orientation, it has been confirmed that the nitrogen partial pressure in the atmosphere is preferably 12% or more and 20% or less. (See FIG. 3 (e), FIG. 3 (f), FIG. 4 (a), and FIG. 4 (b)).

  Further, the barrier layer A (see FIG. 3C and FIG. 3D) obtained when the nitrogen partial pressure is 8% or more and less than 12% is the conductive layer 22 (see FIG. 3C and FIG. 3D). The ferroelectric capacitor 30 formed on the first barrier layer 12a is formed by forming the amorphous first barrier layer 12a on the plug 20 because it is amorphous without depending on the crystal structure of tungsten. It is presumed that the crystal orientation can be prevented from being affected.

  Furthermore, it can be understood from the above results that the seed layer 14s, the first plug layer 12a, and the second plug layer 14a can be separately formed by changing the nitrogen partial pressure in the atmosphere.

3.2. Example 2
In this example, the barrier layer A was formed by changing the substrate temperature during film formation while fixing the nitrogen partial pressure at 16% in Example 1. Conditions other than the nitrogen partial pressure and the substrate temperature were the same as in Example 1.

  FIGS. 5A to 5C show XRD (X-ray diffraction) patterns of the barrier layer A formed at each substrate temperature. FIGS. 5A to 5C are XRD patterns of the barrier layer A formed at substrate temperatures of room temperature, 150 ° C., and 400 ° C., respectively.

  According to FIGS. 5A to 5C, a peak was observed in the vicinity of 2θ = 37 ° in the obtained barrier layer A even at different substrate temperatures. This peak is presumed to be crystalline TiAl having a (111) orientation.

  From the above results, since the crystalline layer made of TiAl having (111) orientation was obtained in any of the cases where the substrate temperature was room temperature, 150 ° C., and 400 ° C., the composition of the barrier layer A was the substrate It was confirmed that it did not change depending on the temperature.

  As described above, the embodiments of the present invention have been described in detail. However, those skilled in the art can easily understand that many modifications can be made without departing from the novel matters and effects of the present invention. . Accordingly, all such modifications are intended to be included in the scope of the present invention.

  For example, the ferroelectric capacitor and the manufacturing method thereof according to the present embodiment can be applied to a capacitor included in a piezoelectric element or the like, for example.

1 is a cross-sectional view schematically showing a ferroelectric memory device according to an embodiment of the present invention. (A)-(f) is sectional drawing which shows typically one manufacturing process of the ferroelectric capacitor contained in the ferroelectric memory device shown by FIG. (A)-(f) shows the XRD pattern of the barrier layer formed into a film in Example 1 by different nitrogen partial pressure, respectively. (A)-(c) shows the XRD pattern of the barrier layer formed into a film in Example 1 by different nitrogen partial pressure, respectively. (A)-(f) each shows the XRD pattern of the barrier layer formed into a film in Example 2 at different substrate temperature.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 Semiconductor substrate, 11 Gate insulating layer, 12, 12a 1st barrier layer, 13 Gate conductive layer, 14, 14a 2nd barrier layer, 14s seed layer, 15 Side wall insulating layer, 16 Element isolation region, 17 1st impurity region , 18 transistor, 19 second impurity region, 20 plug, 22 conductive layer, 24 opening, 26 insulating layer, 30 ferroelectric capacitor, 32, 32a first electrode, 34, 34a ferroelectric film, 36, 36a first 2 electrodes, 100 ferroelectric memory device, R1 resist layer

Claims (7)

An amorphous first barrier layer made of titanium and aluminum nitride ;
A crystalline second barrier layer provided on the first barrier layer and having a (111) orientation and made of an alloy of titanium and aluminum;
A first electrode having a (111) orientation provided on the second barrier layer ;
A ferroelectric film having a (111) orientation provided on the first electrode;
The second electrode and the including provided on the ferroelectric film, a ferroelectric capacitor. An amorphous first barrier layer made of titanium and aluminum nitride ;
A crystalline second barrier layer provided on the first barrier layer and having a (111) orientation and made of a nitride of titanium and aluminum;
A first electrode having a (111) orientation provided on the second barrier layer ;
A ferroelectric film having a (111) orientation provided on the first electrode;
The second electrode and the including provided on the ferroelectric film, a ferroelectric capacitor. In claim 1 or 2 ,
A ferroelectric capacitor provided on the plug. (A) forming an amorphous first barrier layer made of a nitride of titanium and aluminum by a sputtering method in an atmosphere having a nitrogen partial pressure of 8% or more and less than 12% ;
(B) A crystalline second barrier layer having a (111) orientation and made of an alloy of titanium and aluminum is formed on the first barrier layer by sputtering in an atmosphere having a nitrogen partial pressure of less than 8%. Forming the step,
( C ) forming a first electrode having a (111) orientation on the second barrier layer;
( D ) forming a ferroelectric film having a (111) orientation on the first electrode;
( E ) forming a second electrode on the ferroelectric film;
A method for manufacturing a ferroelectric capacitor, comprising: (A) forming an amorphous first barrier layer made of a nitride of titanium and aluminum by a sputtering method in an atmosphere having a nitrogen partial pressure of 8% or more and less than 12% ;
(B) A seed layer made of an alloy of titanium and aluminum is formed on the first barrier layer in an atmosphere where the nitrogen partial pressure is less than 8%, and then the nitrogen partial pressure is 12% or more and 20% or less. Forming a second barrier layer having a (111) orientation and a nitride of titanium and aluminum on the first barrier layer by sputtering in the presence of the seed layer,
( C ) forming a first electrode having a (111) orientation on the second barrier layer;
( D ) forming a ferroelectric film having a (111) orientation on the first electrode;
( E ) forming a second electrode on the ferroelectric film;
A method for manufacturing a ferroelectric capacitor, comprising: In claim 4 or 5 ,
In the method (a), the first barrier layer is formed on a plug. A switching transistor;
Said plug said is switching transistor electrically connected,
The ferroelectric capacitor according to claim 3 provided on the plug;
Including a ferroelectric memory device.

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