JPH09251978A - Method for manufacturing dielectric element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce damages of photoresist and to stop generating residue on a film forming substrate or an electrode film by a method wherein, after patterning of a dielectric is etched with a hydrogen fluoride acid and oxidizing agent, a preprocessing is performed with reducing agent and continuously a postprocessing is performed with an acid. SOLUTION: A lower metal electrode film 102, a dielectric film 103 and an upper metal electrode film 104 are sequentially formed on a substrate 101. Continuously, by use of the patterned upper metal film 104 as a mask, the dielectric film 103 is patterned by chemical etching. As an etchant, a substance that oxidizing agent is added to a hydrogen fluoride acid solution is used. It is impregnated in preprocessing liquid of a composition having a volume ratio of a sulfite solution to an acetic acid which is about 1 to 5. Thereafter, it is impregnated in postprocessing liquid of a composition of about 5mol/l of hydrochloric acid, and a dielectric film and etching residue are completely etched.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a dielectric element, and more particularly to fine processing of a dielectric material by chemical etching.

[0002]

2. Description of the Related Art In recent years, with the development of non-volatile memories, the importance of microfabrication technology for dielectric materials including ferroelectrics has increased.

A reactive ion etching method using a reactive gas has been mainly studied as a fine processing method for a ferroelectric substance such as PbTiO ₃ , PZT and PLZT. However, the reactivity and etching rate of these materials are low, and it has been reported that the sample temperature is heated to several hundreds of degrees Celsius.

[0004]

However, in the above reactive ion etching, the ferroelectric has a small etching rate, and the etching rate ratio (selection ratio) with the photoresist is also small. Therefore, when a ferroelectric film such as a pyroelectric device or a piezoelectric device requires a film thickness of several μm, the etching process requires one hour or more, and the photoresist is used. ,
There is a problem that the ferroelectric is completely removed by etching by the end of etching. As a result, the dielectric film was damaged.

Further, the above method has a problem that the etching residue is redeposited on the side wall of the pattern.

On the other hand, in the chemical etching of a ferroelectric substance which is a perovskite oxide, there is a problem that a residue is generated on a substrate or an electrode in the conventional process using only an etchant. Further, due to the side etching, there is a problem in reproducibility of the pattern shape.

An object of the present invention is to manufacture a dielectric element,
Microfabrication technology by chemical etching of dielectrics, which is particularly simple, has little photoresist damage, has a short process time, does not generate residues on the pattern sidewall, film formation substrate or electrode film, and has excellent pattern reproducibility. Is to supply.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment of a method for manufacturing a dielectric element of the present invention will be described below with reference to the drawings.

(First Embodiment) FIG. 1 shows a cross-sectional view of a dielectric element according to one embodiment of the present invention, and FIG. 2 shows a cross-sectional view of its manufacturing process. As the substrate 101, a MgO single crystal substrate (thickness 5
00 μm) was used. A Pt thin film was formed on the substrate 101 as the lower metal electrode film 102. The lower metal electrode film 102 was produced by a high frequency magnetron sputtering method.

The substrate temperature is 600 as the sputtering film formation condition.
℃, sputter gas mixed Ar (95%) and oxygen (5%)
Combined gas, gas pressure is 0.5Pa, high frequency input power density
Is 2.5 W / cm^Two(13.56MHz), film formation time
It was one hour. The film thickness was 0.15 μm. Sa
In addition, PbZr is formed on the lower metal electrode film 102._0.55T
i _0.45O_ThreeA dielectric film 103 having the following composition was formed. That
The film forming method will be described below.

A high frequency magnetron sputtering apparatus was used for forming a thin film of PbZr _0.55 Ti _0.45 O ₃ . The substrate was attached to a stainless steel substrate holder to form a film. As the target, powders of PbO, TiO ₂ and ZrO ₂ were mixed and put in a copper dish for use. Regarding the mixing ratio of the powder, PbO was added in an excess of 20 mol% with respect to the film composition. The sputtering film formation conditions are as follows: the substrate temperature is 650 ° C., and the sputtering gas is Ar (9
(0%) and oxygen (10%) mixed gas with a gas pressure of 0.9
Pa, high frequency input power density is 2.0 W / cm ² (13.
56 MHz). The film thickness was 3 μm.

Further, an upper metal electrode film 104, which is a Pt thin film, was formed on the dielectric film 103. The preparation method, conditions, and characteristics of the upper metal electrode film 104 are as follows.
It was carried out in the same manner as 02.

After that, a mask pattern was formed on the upper metal electrode film 104 with a photoresist 105, and then the upper metal electrode film 104 was patterned by sputter etching.

FIG. 3 shows a sectional view of the etching apparatus. In FIG. 3, 301 is an etching sample, 302 is a reaction chamber, 303 is a high frequency applying electrode, 304 is a counter electrode, 305 is an exhaust system, 306 is a high frequency power source, and 307 is a gas supply source. The electrodes 303 and 304 are arranged in parallel. Further, a high frequency of 13.56 MHz is applied to the high frequency electrode 303. The high-frequency applying electrode is water-cooled from the back surface. The diameter of the electrode 303 is 1
0 inches.

The etching sample 301 is the high frequency applying electrode 3
It is arranged on 03. The degree of vacuum is 0.0
6 Torr, Ar gas flow rate 10 SCCM, plasma power 170
It took 15 minutes under the condition of W.

Then, using the patterned upper metal electrode film 104 as a mask, the dielectric film 103 was patterned by chemical etching. The etchant used was a hydrofluoric acid aqueous solution to which an oxidizing agent was added.
Then, after dipping for 0.2 to 3 minutes in a pretreatment liquid having a composition in which the volume ratio of the sulfurous acid aqueous solution (35%) and acetic acid is 1 to 5, the posttreatment liquid having a molar concentration of hydrochloric acid is 5 mol / l. The dielectric film and the etching residue were completely etched by immersion for 0.2 to 3 minutes.

Subsequently, the lower metal electrode film 101 was similarly patterned by sputter etching to manufacture a dielectric element.

[0018]

[Table 1]

The oxidizing agent added to the dielectric etchant is preferably composed of at least one of potassium permanganate, potassium dichromate, manganese dioxide, hydrochloric acid, sulfuric acid and nitric acid. It was good. The relationship between the added amount of the oxidizing agent and the etching rate of the dielectric film is shown in (Table 1). From the results shown in Table 1, the etching rate of the dielectric is significantly improved by adding the oxidizing agent to the etchant. Here, the molar ratio of hydrofluoric acid constituting the etchant to the oxidizing agent is 0.05 or more and 20 or more.
When it was less than 00, the etching rate was improved. As a result, the etching process can be shortened, which is effective in that the damage of the photoresist due to the etchant can be reduced. Further, since the side etching amount is reduced, it is effective in improving the reproducibility of the pattern.

Further, in order to clarify the optimum amount of hydrofluoric acid in the etchant, the relationship between the taper angle of the dielectric film pattern and the content of hydrofluoric acid in the etchant was examined. FIG. 5 shows the result when manganese dioxide was used as the oxidizing agent and the molar ratio of hydrofluoric acid to the oxidizing agent was 4. Here, FIG. 4 shows the definition of the taper angle of the dielectric film pattern.

As shown in FIG. 5, when the molar concentration of hydrofluoric acid constituting the etchant is in the range of 0.1 mol / l or more and 15 mol / l or less, the taper angle of the dielectric film pattern becomes 45 ° or more, and the device fabrication is as follows. Was appropriate. When the molar concentration of hydrofluoric acid is in the range of 1 mol / l or more and 10 mol / l or less, the taper angle of the dielectric film pattern becomes 65 degrees or more, the pattern side wall is sharpened, and it is particularly preferable from the viewpoint of pattern reproducibility. .

The oxidant composing the etchant is
The concentration range of hydrofluoric acid was the same for the oxidizing agents other than manganese dioxide shown in Table 1.

(Embodiment 2) FIG. 6 shows a sectional view of a dielectric element according to an embodiment of the present invention, and FIG. 7 shows a sectional view of its manufacturing process. As the substrate 601, a MgO single crystal substrate (thickness 5
00 μm) was used. A dielectric film 602 having a composition of PbTiO ₃ was formed on the substrate 601. This dielectric film 60
2 was manufactured by the high frequency magnetron sputtering method as in Example 1. As the target, powders of PbO and TiO ₂ were mixed and put in a copper dish for use. The powder mixing ratio is
PbO was added in excess of 20 mol% with respect to the film composition. The film formation conditions for sputtering are as follows: substrate temperature is 600 ° C., sputtering gas is a mixed gas of Ar (90%) and oxygen (10%), gas pressure is 0.9 Pa, and high-frequency input power density is 2.0 W / cm ^2.
(13.56 MHz). The film thickness was 3 μm.

Subsequently, after forming a patterned photoresist 603 on the dielectric film 602 as a mask, the dielectric film 602 was patterned by chemical etching. The etchant used was an aqueous solution of hydrofluoric acid to which potassium dichromate was added as an oxidizing agent.
The molar concentration of hydrofluoric acid was 5 mol / l, and the molar ratio of hydrofluoric acid to potassium dichromate was 4. Then, it was immersed in a pretreatment liquid composed of a reducing agent for 0.2 to 3 minutes. Subsequently, the dielectric film and the etching residue were completely etched by immersing in a post-treatment liquid having a hydrochloric acid molar concentration of 5 mol / l for 0.2 to 3 minutes. Finally, the photoresist was chemically removed.

[0025]

[Table 2]

Here, as the reducing agent constituting the pretreatment liquid, hydrogen peroxide, oxalic acid, potassium iodide, sulfurous acid,
It was preferred to consist of at least one of tin (II) chloride, formaldehyde. The results are shown in (Table 2). Here, the concentration of the reducing agent constituting the pretreatment liquid is
In the range of 0.05 mol / l or more and 5 mol / l or less, the dielectric could be patterned without generating a residue. Further, it has been revealed that when the molar concentration of the reducing agent is in the range of 0.1 mol / l or more and 1 mol / l or less, the immersion time in the pretreatment liquid can be shortened and it is particularly effective. As a comparative experiment, a typical oxidizing agent, potassium permanganate, was added to the pretreatment solution instead of the reducing agent, but even after the post-treatment solution, a large number of dielectric film etching residues were present on the substrate. It could not be removed.

(Embodiment 3) FIG. 8 shows a sectional view of a dielectric element according to an embodiment of the present invention, and FIG. 9 shows a sectional view of its manufacturing process. As the substrate 801, a Si single crystal substrate (thickness 50
0 μm) was used. A Ti thin film was formed as an adhesion layer 802 on the substrate 801 by a high frequency magnetron sputtering method, and then a Pt thin film was formed as a lower metal electrode film 803 on the adhesion layer 802. The lower metal electrode film 803 is
It was created in the same manner as in Example 1. In addition, the adhesion layer 80
The film forming conditions of No. ² are as follows: substrate temperature is 600 ° C., sputter gas is Ar gas, gas pressure is 0.7 Pa, high frequency input power density is 5.0 W / cm ² (13.56 MHz), film forming time is 5 minutes. Met.

Then, on the lower metal electrode film 803,
Dielectric film 8 having a composition of BaTiO ₃ or SrTiO ₃
04 was formed. The method for forming the dielectric film is shown below.

The dielectric film having the composition of BaTiO ₃ was formed by the high frequency sputtering method as in the first embodiment. As the target, a sintered body having a composition of BaTiO ₃ was used. The substrate temperature is 700 as the film formation condition of sputtering.
C., the sputtering gas was a mixed gas of Ar (90%) and oxygen (10%), the gas pressure was 0.9 Pa, and the high frequency input power density was 2.0 W / cm ² (13.56 MHz). The film thickness was 3 μm.

Further, the dielectric film having the composition of SrTiO ₃ was formed by the high frequency sputtering method as in the first embodiment. As the target, a sintered body having a composition of SrTiO ₃ was used. The substrate temperature is 50 when the film is formed by sputtering.
0 ° C, sputter gas is Ar (90%) and oxygen (10%)
The gas pressure was 0.9 Pa, and the high frequency input power density was 2.0 W / cm ² (13.56 MHz).
The film thickness was 3 μm.

After forming a mask pattern on the dielectric film 804 with a photoresist 805, the dielectric film 804 was patterned by chemical etching. The etchant used was an aqueous solution of hydrofluoric acid to which potassium permanganate was added as an oxidant. The molar concentration of hydrofluoric acid was 5 mol / l, and the molar ratio of hydrofluoric acid to potassium permanganate was 5. Then, after dipping for 0.2 to 3 minutes in a pretreatment solution having a composition of a potassium iodide aqueous solution (0.1 mol / l) and acetic acid in a volume ratio of 1: 5, the posttreatment solution is treated for 0.2 to 3 minutes. The dielectric film and the etching residue were completely etched by immersion. Finally, after chemically removing the photoresist, Example 1
The metal electrode film was patterned by the same process as described above to produce a dielectric element.

[0032]

[Table 3]

The acid constituting the post-treatment liquid is hydrochloric acid,
It was suitable to consist of at least one of acetic acid, sulfuric acid or nitric acid. The dielectric film 804 is shown in (Table 3).
The results are shown for the case where the composition is BaTiO ₃ .
Here, when the concentration of the acid constituting the post-treatment liquid was in the range of 0.1 mol / l or more and 12 mol / l or less, the dielectric could be patterned without generating a residue. In particular, the concentration of acid
It has been revealed that in the range of 1.0 mol / l or more and 6.5 mol / l or less, the immersion time in the post-treatment liquid can be shortened, and it is particularly effective from the viewpoint of pattern reproducibility. Also,
Similar results were obtained when the dielectric film 804 was SrTiO ₃ .

In the first, second and third embodiments,
As a _{dielectric, PbZr 0.55 Ti 0.4 5 O 3} , PbTi
O ₃ , BaTiO ₃ , and SrTiO ₃ were taken as an example, and the film forming method was also a high frequency sputtering method. However, it is clear that the present invention is also effective for dielectrics having other compositions or dielectric films formed by other film forming methods such as the CVD method and the sol-gel method. Furthermore, it is clear that the present invention is effective even when the dielectric is a form other than a thin film.

Further, although Pt is exemplified as the metal electrode film in the first and third embodiments, it is obvious that the present invention is effective for other metal materials.

Further, in Examples 1, 2, and 3, the MgO single crystal substrate and the Si single crystal substrate were illustrated as the substrate material. However, the present invention is not limited to other single crystal substrates,
It is clear that it is also effective for non-single crystal substrates such as glass substrates and stainless metal substrates.

Furthermore, in Examples 1, 2 and 3, as oxidizing agents added to the etchant, potassium permanganate, potassium dichromate, manganese dioxide,
Hydrochloric acid, sulfuric acid and nitric acid were used. However, it is clear that other oxidizing agents can achieve the same effect.

In the first, second and third embodiments,
Hydrogen peroxide, oxalic acid, potassium iodide, sulfurous acid, tin (II) chloride, and formaldehyde were used as reducing agents added to the pretreatment liquid. However, it is clear that other reducing agents have similar effects.

Further, in Examples 1, 2 and 3, hydrochloric acid, acetic acid, sulfuric acid or nitric acid was used as the acid added to the post-treatment liquid. However, it is clear that other acids have similar effects.

[0040]

As described above, according to the method of manufacturing a dielectric element of the present invention, the patterning of the dielectric is performed after etching with an etchant composed of hydrofluoric acid and an oxidant and before formation of the reducing agent. The method includes a step of removing an etching residue with a treatment liquid and then a post-treatment liquid composed of an acid.

Further, the dielectric has a composition of any one of lead titanate type, lead zirconate type, lead zirconate titanate type, barium titanate type, strontium titanate type, and strontium barium titanate type. ing.

Further, a step of forming a metal electrode film on the substrate, a step of forming a patterned electrode by etching the metal electrode film, and a dielectric film having the above-described composition on the patterned metal electrode film. And a step of patterning the dielectric film by the chemical etching method described above.

Furthermore, the method further comprises the steps of forming a dielectric film having the above-described composition on the substrate and forming a dielectric film by patterning the dielectric film by the chemical etching method described above.

Further, a step of forming a dielectric film having the above composition on the substrate, a step of forming a metal electrode film on the dielectric film, and a metal electrode film formed by etching and patterning the metal electrode film. And a step of patterning the dielectric film by the chemical etching method described above.

Further, a step of forming a metal electrode film on the substrate, a step of forming a dielectric film having the above-described composition on the metal electrode film, and the dielectric film is patterned by the chemical etching method described above. And a step of forming a patterned metal electrode film by etching the metal electrode film.

Furthermore, a step of forming a lower metal electrode film on the substrate, a step of forming a dielectric film having the above composition on the lower metal electrode film, and an upper metal electrode film on the dielectric film. Forming step, forming an upper metal electrode film by etching and patterning the upper metal electrode film, patterning the dielectric film by the chemical etching method described above, and finally etching and patterning the lower metal electrode film The method includes a step of forming a lower metal electrode film.

According to the present invention, by adding at least one oxidizing agent selected from potassium permanganate, potassium dichromate, manganese dioxide, hydrochloric acid, sulfuric acid and nitric acid to the dielectric etchant, The etching rate of the dielectric has been greatly improved. Therefore, the etching process can be shortened. As a result, it is effective in reducing the damage of the photoresist due to the etchant. Further, since the side etching amount is reduced, it is effective in improving the reproducibility of the pattern.

Further, as a reducing agent constituting the pretreatment liquid, hydrogen peroxide, oxalic acid, potassium iodide, sulfurous acid, tin chloride are used.
By using at least one of (II) and formaldehyde, the dielectric could be patterned without generating a residue. Furthermore, by using at least one of hydrochloric acid, acetic acid, and nitric acid as the acid that constitutes the post-treatment liquid, the dielectric could be patterned without generating a residue. As a result, it is effective in that the pattern of the dielectric element can be miniaturized. Furthermore, when an insulating layer or an electrode film is formed on the dielectric film after patterning, it is effective in that it is possible to prevent the occurrence of disconnection and cracks.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a dielectric element of Example 1.

FIG. 2 is a cross-sectional view of the manufacturing process of the dielectric element of Example 1.

FIG. 3 is a sectional view of an etching apparatus used in Examples 1 and 3.

FIG. 4 is a sectional view showing a taper angle of a dielectric film pattern.

5 is a graph showing the relationship between the molar concentration of hydrofluoric acid in the etchant and the taper angle of the pattern in Example 1. FIG.

FIG. 6 is a cross-sectional view of a dielectric element of Example 2.

FIG. 7 is a cross-sectional view of the manufacturing process of the dielectric element of Example 2.

FIG. 8 is a cross-sectional view of a dielectric element of Example 3

FIG. 9 is a sectional view of the manufacturing process of the dielectric element of Example 3;

[Explanation of symbols]

 101 substrate 102 lower metal electrode film 103 dielectric film 104 upper metal electrode film 105 photoresist 301 etching sample 302 reaction chamber 303 high frequency applying electrode 304 counter electrode 305 exhaust system 306 high frequency power supply 307 gas supply source 601 substrate 602 dielectric film 603 photo Resist 801 Substrate 802 Adhesive layer 803 Lower electrode 804 Dielectric film 805 Photoresist

Continuation of the front page (51) Int.Cl. ⁶ Identification number Office reference number FI Technical indication location H01L 21/8247 H01L 29/78 371 29/788 29/792 (72) Inventor Atsushi Tomozawa Kadoma, Osaka Prefecture 1006 Matsushita Electric Industrial Co., Ltd.

Claims (6)

[Claims] 1. A patterning of a dielectric material is carried out by etching with an etchant composed of hydrofluoric acid and an oxidant, followed by etching with a pretreatment liquid composed of a reducing agent and subsequently a post-treatment liquid composed of an acid. A method of manufacturing a dielectric element, which comprises removing a residue. 2. The dielectric material is lead titanate type, lead zirconate type,
2. The dielectric material according to claim 1, wherein the dielectric material is a lead zirconate titanate-based, barium titanate-based, strontium titanate-based, or strontium barium titanate-based dielectric material. Method. 3. A step of forming a metal electrode film on a substrate, a step of etching the metal electrode film to form a patterned electrode, wherein a dielectric film is formed on the patterned metal electrode film. Claim 1 or 2 characterized
A method for manufacturing the dielectric element according to 1. 4. The method for manufacturing a dielectric element according to claim 3, wherein the etching of the metal electrode film is performed after the etching of the dielectric. 5. A dielectric having a lead titanate-based, lead zirconate-based, lead zirconate titanate-based, barium titanate-based, strontium titanate-based, or strontium barium titanate-based composition on a substrate. A step of forming a film, a step of forming a metal electrode film on the dielectric film, a step of forming a metal electrode film by etching and patterning the metal electrode film, and a step of forming the dielectric film with hydrofluoric acid and an oxidizing agent. After etching with an etchant composed of the above, a step of patterning is performed by removing an etching residue with a pretreatment liquid composed of a reducing agent and then a posttreatment liquid composed of an acid. Method of manufacturing dielectric element. 6. A step of forming a lower metal electrode film on a substrate,
A dielectric film having any of lead titanate-based, lead zirconate-based, lead zirconate titanate-based, barium titanate-based, strontium titanate-based, and strontium barium titanate-based compositions on the lower metal electrode film. Forming step, forming an upper metal electrode film on the dielectric film,
Forming a patterned upper metal electrode film by etching the upper metal electrode film, etching the dielectric film with an etchant composed of hydrofluoric acid and an oxidizing agent, and then performing a pretreatment composed of a reducing agent And a step of patterning by removing an etching residue with a post-treatment solution composed of an acid, and a step of finally etching and patterning the lower metal electrode film. And a method for manufacturing a dielectric element.