KR100269320B1 - Method for forming a dielecctric film and method for fabricating a capacitor using the same - Google Patents

Abstract

PURPOSE: A method of manufacturing a dielectric layer and a capacitor using the dielectric layer is provided to increase dielectric ratio of the dielectric layer and reduce the process time. CONSTITUTION: In order to increase the crystallization of a dielectric layer, a seed layer(20) is formed on a semiconductor substrate within 60 seconds by sputtering at temperatures lower than 700 degrees centigrade. A dielectric layer(30) is deposited on the seed layer.

Description

Method for forming a dielecctric film and method for fabricating a capacitor using the same

The present invention relates to a method of manufacturing a semiconductor memory device, and more particularly, to a method of forming a dielectric film and a method of manufacturing a capacitor using the same.

As semiconductor memory devices are highly integrated, the area used as a capacitor is gradually reduced, and it is difficult to secure capacitance necessary for operation of the device with a dielectric film such as an oxide film, a nitride film, and tantalum pentoxide (Ta ₂ O ₅ ). Therefore, many methods for increasing the capacitance of a memory cell in a limited cell area have been proposed, and are generally divided into the following three. That is, (1) thinning the dielectric film, (2) increasing the effective area of the capacitor, and (3) using a material having a high dielectric constant as the dielectric film.

In the first method, that is, when the thickness of the dielectric film is reduced to 100 Å or less, the reliability of the device is degraded by the Fowler-Nodheim current, which makes it difficult to apply to a large-capacity memory device. The second method, that is, the method of three-dimensionally reducing the structure of a capacitor, involves a complicated process for manufacturing a three-dimensional capacitor, and thus, an increase in manufacturing cost is inevitable. It is difficult to obtain the capacitance value required for the operation of a memory device of more than a gigabyte DRAM.

As a result, P. G. Tee (PZT; PbZrTiO ₃ ) or ratio. s. Research into replacing dielectric films with high dielectric materials of Ti (BST; BaSrTiO ₃ ) series is actively underway. Unlike the silicon oxide film, silicon nitride film, or tantalum pentoxide (Ta ₂ O ₅ ) film, which is used as a dielectric film, these high dielectric materials exhibit spontaneous polarization without an external electric field in an arbitrary temperature range. Has a high dielectric constant of several hundred to 1,000. Therefore, when the dielectric film is formed of the high dielectric material, the capacitance required for the operation of the device may be obtained without forming the storage electrode into a complicated structure such as a cylinder or a fin structure.

However, even in such a high dielectric film, as the size of the device becomes smaller, it is necessary to increase the dielectric constant in order to obtain a capacitor having excellent characteristics in a simpler structure.

As a method of increasing the dielectric constant of a high dielectric film, a method of increasing the dielectric constant through subsequent heat treatment after forming a high dielectric film is generally described in "Appl. Phys. Lett. 67 (1995), pp. 2819". According to this method, the dielectric constant can be increased by depositing a BST film at a temperature of 640 ° C. and then performing a subsequent heat treatment in an atmosphere of 750 ° C. and nitrogen gas (N ₂ ).

Another method of increasing the permittivity of high dielectric films is disclosed in Jpn. J. Appl. Phys. Vol. 36 (1997), pp. 3564-3568. According to this method, before depositing the high dielectric film, the lower film quality is pretreated at about 1,000 ° C. in an oxygen gas (O ₂ ) atmosphere for about 5 hours to flatten the surface of the lower film quality to improve crystallinity of the high dielectric film.

Meanwhile, a method of obtaining a smooth surface by depositing a high dielectric film by two-step deposition by chemical vapor deposition (CVD) method (Jpn. J. Appl. Phys. Vol. 34 (1995). .5077-5082) have been disclosed, but there is no description of an increase in permittivity.

On the other hand, according to a recent paper, a method of increasing the capacitance by improving the crystallinity of the high dielectric film by depositing the high dielectric film in two steps has been published (SPIE Vol.2636, pp.134-141). . However, according to this method, the process proceeds by BST film deposition → annealing → BST film re-deposition → annealing, and thus, two annealing processes are required, resulting in a long process time.

Accordingly, the technical problem to be achieved by the present invention is to provide a method of forming a high dielectric film capable of improving the dielectric constant of the high dielectric film and reducing the processing time.

Another object of the present invention is to provide a method of manufacturing a capacitor having a high dielectric constant having improved dielectric constant.

1 is a graph showing the change in permittivity according to the thickness of the BST film,

FIG. 2 is a graph showing changes in dielectric constant according to thickness of a BST film when heat treatment is performed after the deposition of a BST film.

3 shows an XRD pattern of a BST thin film deposited under various temperature conditions.

Figure 4 shows the XRD pattern after the heat treatment for 30 minutes at 750 ℃ after depositing the BST thin film.

5 is a graph showing a change in capacitance according to the deposition temperature of the nucleation layer.

6 is a graph showing a change in capacitance with deposition time of a nucleation layer.

7 is a graph showing the XRD pattern of the BST film according to the deposition time of the nucleation layer.

8 is a cross-sectional view illustrating a method of manufacturing a capacitor using a high dielectric film according to the present invention.

Explanation of symbols on the main parts of the drawings

10 ..... bottom electrode 20 ..... seed layer

30..Dielectric film 40..Top electrode

In order to achieve the above object, a method of forming a dielectric film according to the present invention includes forming a seed layer for improving the crystallinity of a high dielectric film on a semiconductor substrate, and inherently on the seed layer. And depositing an entire film.

It is preferable to form the said nucleation layer in thickness of 100 Pa or less by the sputtering method at the temperature of 700 degrees C or less.

The nucleation layer is p. G. Ti (PZT), lead-titanium oxide (PbTiO ₃ ), lead-lanthanum-titanium oxide (PbLaTiO ₃ ), barium-titanium oxide (BaTiO ₃ ), bismuth-titanium oxide (Bi ₃ Ti ₄ O ₁₂ ), strontium-bismuth Tantalum oxide (SrBi ₂ Ta ₂ O ₉ ), b. s. T (BST; BaSrTiO ₃ ) and S. tea. Any one selected from the group consisting of oxides of perovskite structures such as STO (SrTiO ₃ ), bismuth-titanium oxide (Bi ₄ Ti ₃ O ₁₂ ) and strontium-bismuth-tantalum oxide (SrBi ₂ Ta ₂ O ₉ ) It is preferable to form one.

According to another aspect of the present invention, there is provided a method of manufacturing a capacitor, including forming a lower electrode on a semiconductor substrate, and forming a nucleation layer on the lower electrode to improve crystallinity of the dielectric film. Forming a high dielectric film on the nucleation layer, and forming an upper electrode on the high dielectric film.

The lower electrode and the upper electrode are metals such as platinum (Pt), ruthenium (Ru), iridium (Ir), palladium (Pd), osmium (Os), alloys based on these metals, and iridium oxide (IrO ₂ ). As an oxide conductor with platinum oxide, platinum oxide, osmium oxide, indium oxide, indium tin oxide (ITO), ruthenium oxide (RuO ₂ ) and perovskite structures It is preferable to form one or a combination of two or more selected from the group consisting of.

The nucleation layer is formed to a thickness of 100 kPa or less using a sputtering method at a temperature of 700 ° C or less.

And the nucleation layer is p. G. Ti (PZT), lead-titanium oxide (PbTiO ₃ ), lead-lanthanum-titanium oxide (PbLaTiO ₃ ), barium-titanium oxide (BaTiO ₃ ), bismuth-titanium oxide (Bi ₃ Ti ₄ O ₁₂ ), strontium-bismuth Tantalum oxide (SrBi ₂ Ta ₂ O ₉ ), b. s. T (BST; BaSrTiO ₃ ) and S. tea. Any one selected from the group consisting of oxides of perovskite structures such as STO (SrTiO ₃ ), bismuth-titanium oxide (Bi ₄ Ti ₃ O ₁₂ ) and strontium-bismuth-tantalum oxide (SrBi ₂ Ta ₂ O ₉ ) It is preferable to form one.

In addition, the nucleation layer or the high dielectric film may be deposited at least one step.

According to the present invention, by forming the nucleation layer before depositing the high dielectric film, the dielectric constant of the high dielectric film can be improved, and the capacitance of the memory cell can be easily increased.

Hereinafter, the present invention will be described in more detail with reference to the accompanying drawings.

The embodiments described below may be modified in many different forms, and the scope of the present invention is not limited to the embodiments described below. The embodiments of the present invention are provided to more completely explain the present invention to those skilled in the art. In the drawings illustrating embodiments of the present invention, the thicknesses of certain layers or regions are exaggerated for clarity of specification, and like numerals in the drawings refer to like elements. In addition, where a layer is described as being "top" of another layer or substrate, the layer may be present directly on top of the other layer or substrate, with a third layer intervening therebetween.

In the present invention, the dielectric constant of the high dielectric film is increased by depositing a high dielectric film (main layer) after depositing the initial nucleation layer under a predetermined condition in the process of depositing the high dielectric film during the formation of the capacitor using the high dielectric film. It provides a method to make it.

Experimental Example 1

In order to examine the increase in dielectric constant of the dielectric film in the case of depositing the initial nucleation layer and then depositing the main layer, experiments were performed under the conditions shown in Table 1 below.

Condition Nucleation Layer (Deposition Temperature / Thickness) High dielectric film (deposition temperature) A none 400 ℃ B none 480 ℃ C 400 ℃ / 20Å 480 ℃

Under the above experimental conditions, a BST film was used as the high dielectric film, and both the initial seed layer and the BST main layer were known. F. Deposition was performed by magnetron sputtering. In addition, a mixed gas of argon (Ar) / oxygen (O ₂ ) was used as the sputtering gas, and capacitors using platinum (Pt) were formed as upper and lower electrodes and measured.

1 and 2 are graphs showing the change in permittivity according to the thickness of the BST film as a result of the experiment of Table 1 above.

Referring to FIG. 1, the dielectric constant of the BST film is increased when the deposition temperature of the BST is increased from 400 ° C. to 480 ° C. in the entire thickness region. In addition, the BST thin film deposited at 480 ° C. after forming a nucleation layer of 20 Å at 400 ° C. has a larger dielectric constant than the thin film deposited at the same temperature (480 ° C.) in the entire thickness region.

Referring to FIG. 2, it can be seen that the dielectric constant of the BST thin film deposited after forming the nucleation layer even after the heat treatment at 750 ° C. for 30 minutes was significantly increased compared to the thin film deposited under other conditions.

Experimental Example 2

Next, the XRD (X-Ray Diffraction) pattern of the BST thin film deposited under the conditions of (Experimental Example 1) was examined to examine the cause of the increase in the dielectric constant. 3 shows an XRD pattern of a BST thin film having a thickness of 800 GPa deposited under the conditions of (Experimental Example 1).

When comparing (a) and (b) of Figure 3, it can be seen that as the deposition temperature of the BST increases from 400 ℃ to 480 ℃, the crystallization of the BST is improved to increase the peak intensity of the XRD pattern (peak intensity) have. In particular, the XRD pattern of the BST thin film deposited after the nucleation layer was formed can be seen that the maximum strength was significantly increased when the crystal direction is (110) and (200) than the BST thin film deposited at the same temperature.

As described above, when the high dielectric film is deposited after the initial nucleation layer is formed, the dielectric constant is greatly increased, and the increase in the dielectric constant is due to the improved crystallinity of the thin film.

Figure 4 shows the XRD pattern after the heat treatment for 30 minutes at 750 ℃ after depositing the BST thin film. The conditions for depositing the BST thin film are also the same as in Experimental Example 1.

As can be seen in Figure 4, the dielectric constant was increased by the subsequent heat treatment process after deposition of the BST film, but did not show a large increase on the XRD pattern. These results indicate that the heat treatment after the deposition of the BST film does not improve the crystallization of the BST thin film, but results in an increase in the dielectric constant by forming a Schottky contact between the BST film and the electrode to improve the contact characteristics. Can be.

Experimental Example 3

Next, in order to examine the relationship between the deposition conditions of the nucleation layer and the increase in the dielectric constant of the dielectric film, the capacitance was measured while changing the deposition conditions of the nucleation layer.

First, FIG. 5 is a graph showing the change in capacitance according to the deposition temperature of the nucleation layer. The BST nucleation layer is deposited at temperatures of 550 ° C. and 750 ° C. for 30 seconds, and then the main BST film is deposited at 480 ° C. to form the entire dielectric film ( The thickness of the nucleation layer + main dielectric film) was formed to be 400 GPa.

As shown in FIG. 5, the capacitance was increased as compared with the normal deposition condition, that is, the case where the BST film was formed without depositing the nucleation layer, but the capacitance did not change with the deposition temperature of the nucleation layer.

Next, Figure 6 is a graph showing the change in capacitance according to the deposition time of the nucleation layer, the deposition time of the BST nucleation layer at a temperature of 550 ℃, 750 ℃ respectively 30 seconds, 1 minute, 2 minutes, 3 minutes After the deposition, the main BST film was deposited at 400 ° C. to form a thickness of the entire dielectric film (nucleation layer + main dielectric film) of 400 Å.

Referring to FIG. 6, the capacitance was greatly changed according to the deposition time of the nucleation layer. In particular, when the deposition time was 60 seconds or less, the capacitance was higher than normal conditions, that is, when the dielectric film was formed without deposition of the nucleation layer.

7 is a graph showing the XRD pattern of the BST film according to the deposition time of the nucleation layer, the deposition of the nucleation layer at a temperature of 400 ℃ with the deposition time of 30 seconds, 60 seconds, 120 seconds, 180 seconds respectively, and then the main BST The film was deposited at 480 ° C. to form a thickness of 400 kPa of the entire dielectric film (nucleation layer + main dielectric film).

As shown, it can be seen that when the deposition time is 30, the maximum strength of the BST film is greatest.

In the above results, it can be seen that when the high dielectric film is deposited after the initial nucleation layer is deposited, the crystallinity is improved compared to other thin films deposited at the same temperature, thereby increasing the dielectric constant. In addition, it can be seen that the crystallinity of the high dielectric thin film depends on the initial nucleation layer rather than the subsequent heat treatment performed at high temperature.

In addition, the dielectric constant of the high dielectric film was closely related to the deposition time of the nucleation layer deposited initially, and was independent of the deposition temperature. In particular, when the deposition time of the nucleation layer is 60 seconds or less, the dielectric constant can be greatly increased as compared with the normal case.

Example

Next, the manufacturing method of the capacitor provided with a high dielectric film is demonstrated using the result of Experimental example 1, 2, 3.

8 is a cross-sectional view illustrating a method of manufacturing a capacitor using a high dielectric film according to the present invention.

First, a conductive layer is formed on a semiconductor substrate (not shown) to a thickness of about 100 to 3,000 Å, and then the conductive layer is patterned using a conventional photolithography process to form the lower electrode 10 of the capacitor. do.

As a material for forming the lower electrode 10 of the capacitor, a conductive material having high conductivity and oxidation resistance, that is, platinum (Pt), ruthenium (Ru), iridium (Ir), palladium (Pd), and osmium (Os) Metals such as these and alloys based on these metals, ie, iridium oxide (IrO ₂ ), platinum oxide, osmium oxide, indium oxide, indium tin oxide (ITO) ), Any one of ruthenium oxide (RuO ₂ ) and an oxide conductor having a perovskite structure or a combination of these materials is used.

As the deposition method of the conductive layer, it is preferable to use sputtering or chemical vapor deposition (CVD). For example, in the case of platinum (Pt) -based metal, using the metal as a target to maintain a substrate temperature of room temperature ~ 500 ℃ and chamber pressure of 1 ~ 10mTorr in argon (Ar) atmosphere Deposit using a DC sputtering method. When using an oxide of platinum-based metal, RF sputtering is carried out in an atmosphere in which 5-100% of oxygen (O ₂ ) is mixed with argon (Ar) gas while maintaining a chamber pressure of 1 to 10 mTorr using a platinum-based metal as a target. Or by using a reactive sputtering method. In the case of depositing platinum (Pt) using the CVD method, using a platinum-hexafluoroacetylacetonate (Pt-HFA) ₂ as a platinum source (substrate), the substrate temperature of 100 ~ 500 ℃ and 10mTorr ~ 10Torr It can be deposited by flowing 100 ~ 1,000sccm of argon (Ar) to the carrier gas under the pressure of.

Next, a nucleation layer 20 is formed on the lower electrode 10 to improve the crystallinity of the high dielectric film.

The nucleation layer 20 is the same material as the material for forming the dielectric film. G. Ti (PZT), lead-titanium oxide (PbTiO ₃ ), lead-lanthanum-titanium oxide (PbLaTiO ₃ ), barium-titanium oxide (BaTiO ₃ ), bismuth-titanium oxide (Bi ₃ Ti ₄ O ₁₂ ), strontium-bismuth Tantalum oxide (SrBi ₂ Ta ₂ O ₉ ), b. s. T (BST; BaSrTiO ₃ ), S. tea. Selected from the group consisting of perovskite-structured oxides such as O (STO; SrTiO ₃ ), and bismuth-titanium oxide (Bi ₄ Ti ₃ O ₁₂ ) and strontium-bismuth-tantalum oxide (SrBi ₂ Ta ₂ O ₉ ) It can be formed by either. In addition, the nucleation layer 20 is preferably formed to a thickness of 100 kPa or less at a temperature of 700 ℃ or less using a sputtering method. In addition, as shown in FIG. 6, it is preferable to deposit the nucleation layer 20 for a time of 60 seconds or less in order to most effectively increase the capacitance.

Next, a high dielectric film is continuously deposited on the nucleation layer 20 to form a dielectric film 30 of a capacitor. More specifically, the dielectric film 30 is formed by depositing a high-k dielectric film such as BST on the resultant substrate on which the lower electrode of the capacitor is formed by sputtering or CVD.

The dielectric film 30 is formed of the same material as the nucleation layer 20, p. G. Ti (PZT), lead-titanium oxide (PbTiO ₃ ), lead-lanthanum-titanium oxide (PbLaTiO ₃ ), barium-titanium oxide (BaTiO ₃ ), bismuth-titanium oxide (Bi ₃ Ti ₄ O ₁₂ ), strontium-bismuth Tantalum oxide (SrBi ₂ Ta ₂ O ₉ ), b. s. T (BST; BaSrTiO ₃ ), S. tea. Selected from the group consisting of perovskite-structured oxides such as O (STO; SrTiO ₃ ), and bismuth-titanium oxide (Bi ₄ Ti ₃ O ₁₂ ) and strontium-bismuth-tantalum oxide (SrBi ₂ Ta ₂ O ₉ ) Either one can be used.

For example, when the BST is deposited by the sputtering method, the substrate temperature of 550 to 650 ° C. and the chamber pressure of 1 to 10 mTorr are maintained by using the BST target, and the atmosphere containing argon (Ar) and oxygen (O ₂ ) is contained. Deposition at In the case of vapor deposition using the CVD method, Ba (DPM) ₂ , Sr (DPM) ₂ and Ti (DPM) ₂ are used as main components as CVD sources, and oxygen (O ₂ ) is dissolved in oxygen (O ₂ ) as the oxidizing gas. A source containing 10 to 50% of N ₂ O) is loaded into argon (Ar), which is a carrier gas, and deposited by flowing into a chamber maintained at a substrate temperature of 550 to 800 ° C. and a chamber pressure of 0.1 to 10 Torr.

The nucleation layer 20 and the dielectric film 30 may be formed in one step or multiple steps.

Next, a platinum metal or an oxide of platinum metal is deposited on the dielectric film 30 in the same manner as the method of forming the lower electrode 10 to form a conductive layer for the upper electrode. Subsequently, after forming the upper electrode 40 by patterning by a photolithography process, a capacitor is completed according to a conventional capacitor manufacturing process.

Although the present invention has been described in detail above, the present invention is not limited to the above-described embodiments, and many modifications are possible by those skilled in the art within the technical idea of the present invention.

According to the method of forming the dielectric film and the method of manufacturing the capacitor according to the present invention described above, a high-k dielectric layer (main layer) is deposited after the initial nucleation layer is deposited in the step of depositing a high-k dielectric during the formation of the capacitor using the high-k dielectric film. ), The dielectric constant of the dielectric film can be increased. Thus, it is possible to increase the capacitance of a capacitor without a complicated process. In addition, when the deposition time of the nucleation layer is 60 seconds or less, the capacitance can be greatly increased than in the normal case, and the capacitance can be improved even without adding an annealing process after deposition of the nucleation layer.

Claims (13)

Forming a seed layer on the semiconductor substrate in a time range of less than 60 seconds using sputtering to improve the crystallinity of the dielectric film; And And depositing a dielectric film on the seed layer. The method of claim 1, wherein the forming of the nucleation layer comprises: A method of forming a dielectric film, characterized in that at a temperature of 700 ° C or less. The method of claim 1, wherein the nucleation layer, A method of forming a dielectric film, characterized by forming a thickness of 100 kPa or less. The method of claim 1, wherein the nucleation layer, A dielectric film formed of any one selected from the group consisting of a perovskite oxide, bismuth-titanium oxide (Bi ₄ Ti ₃ O ₁₂ ), and strontium-bismuth-tantalum oxide (SrBi ₂ Ta ₂ O ₉ ). Formation method. The method of claim 4, wherein the oxide of the perovskite structure, blood. G. Ti (PZT), lead-titanium oxide (PbTiO ₃ ), lead-lanthanum-titanium oxide (PbLaTiO ₃ ), barium-titanium oxide (BaTiO ₃ ), bismuth-titanium oxide (Bi ₃ Ti ₄ O ₁₂ ), strontium-bismuth Tantalum oxide (SrBi ₂ Ta ₂ O ₉ ), b. s. T (BST; BaSrTiO ₃ ) and S. tea. A method of forming a dielectric film, characterized in that any one selected from the group consisting of (STO; SrTiO ₃ ). Forming a lower electrode on the semiconductor substrate; Forming a nucleation layer on the lower electrode in a time range within 60 seconds using sputtering to improve crystallinity of the dielectric film; Forming a dielectric film on the nucleation layer; And And forming an upper electrode on the dielectric film. The method of claim 6, wherein the lower electrode and the upper electrode, Metals such as platinum (Pt), ruthenium (Ru), iridium (Ir), palladium (Pd), and osmium (Os), and alloys based on these metals, iridium oxide (IrO ₂ ), and platinum oxide Any one selected from the group consisting of an oxide conductor having an osmium oxide, indium oxide, indium tin oxide (ITO), ruthenium oxide (RuO ₂ ), and a perovskite structure; or Method for producing a capacitor, characterized in that formed by two or more combinations. The method of claim 6, wherein forming the nucleation layer, Method for producing a capacitor, characterized in that at a temperature of 700 ℃ or less. The method of claim 6, wherein the nucleation layer, A method for producing a capacitor, characterized in that formed to a thickness of less than 100 kPa. The method of claim 6, wherein the nucleation layer, A capacitor having a perovskite structure, bismuth-titanium oxide (Bi ₄ Ti ₃ O ₁₂ ) and strontium-bismuth- tantalum oxide (SrBi ₂ Ta ₂ O ₉ ) formed of any one selected from the group consisting of Manufacturing method. The method of claim 10, wherein the oxide of the perovskite structure, blood. G. Ti (PZT), lead-titanium oxide (PbTiO ₃ ), lead-lanthanum-titanium oxide (PbLaTiO ₃ ), barium-titanium oxide (BaTiO ₃ ), bismuth-titanium oxide (Bi ₃ Ti ₄ O ₁₂ ), strontium-bismuth Tantalum oxide (SrBi ₂ Ta ₂ O ₉ ), b. s. T (BST; BaSrTiO ₃ ) and S. tea. The manufacturing method of a capacitor, characterized in that any one selected from the group consisting of (STO; SrTiO ₃ ). The method of claim 6, wherein in the forming of the nucleation layer, At least one step of depositing the nucleation layer. The method of claim 6, wherein in the forming of the dielectric film, At least one step of depositing the dielectric film.

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