JP2000173999A - Manufacture of semiconductor device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method of manufacturing a semiconductor device which effectively remove the etching residual liq. with avoiding dissolving a ferroelectric film and denaturing the surface. SOLUTION: The manufacturing method is such that a capacitor lower electrode layer 113, a ferroelectric film 114 and a capacitor upper electrode layer 115 are formed in this order, and a dry etching using a photo resist 116 and a patterning follow. Using an alkaline cleaning liq., etch residues 117 are removed. The cleaning liq. uses e.g. aqueous ammonia of pH 8 or more.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method of manufacturing a semiconductor device having a ferroelectric film, and more particularly, to a method of manufacturing a semiconductor device having a capacitor using a ferroelectric film as a capacitor insulating film.

[0002]

2. Description of the Related Art Metal oxide thin films whose thickness and composition are controlled at the nanometer level are being actively studied in many fields because of their wide application and industrial requirements. For example, in the semiconductor industry today, higher integration of electronic devices has become an important technical goal, and technology using ferroelectrics as capacitive insulating films instead of conventional silicon oxides or nitrogen oxides is attracting attention. I'm afraid. Furthermore, aiming at the practical use of a non-conventional non-volatile RAM with a low operating voltage and high-speed writing / reading, there is a need for a thin film manufacturing technology with higher precision. On the other hand, in spite of the development of high-precision film thickness and composition control technology, extremely high cleanliness is required in the manufacturing process of these ferroelectric films, and the adhesion of slight impurities It is known that the characteristics change due to the influence or the change of the state. For such a ferroelectric film whose film thickness and composition are controlled at the nano level, it is necessary to develop a high-precision cleaning technique in order to obtain high cleanliness.

Hereinafter, a conventional method for manufacturing a semiconductor device having a capacitance element using a ferroelectric film as a capacitance insulating film will be described with reference to the drawings.

[0004] First, using a known method, FIG.
The MOS transistor is formed on the silicon substrate 101 as described above. First, a silicon oxide film 102 is formed by thermal oxidation. Then, phosphorus-doped polysilicon 103, WS
After i104 is formed in this order, these are patterned to form a gate electrode. Next, the impurity diffusion layer 105 is formed by ion implantation to complete the MOSFET.

Next, as shown in FIG. 4B, a silicon oxide film (BPSG) 10 containing boron is used as an interlayer insulating film.
8, a contact hole is opened by etching, and a Ti film 109 and a tungsten film 110 are formed in this order in the hole. Thus, a tungsten plug is formed.

Subsequently, as shown in FIG. 4C, after forming the capacitor lower electrode layer 113, a PZT film 114 and a capacitor upper electrode layer 115 are formed in this order. For example, the capacitor lower electrode layer 113 is composed of Pt / TiN / Ti,
Reference numeral 5 denotes a layered structure of IrO ₂ / Ir. PZT film is CV
It is formed by the D method or the like.

Next, a photoresist 116 is formed on the capacitor upper electrode layer 115 (FIG. 5A). Then, using the photoresist 116 as a mask, the capacitor lower electrode layer 113, the PZT film 114, and the capacitor upper electrode layer 115
Is dry-etched into a predetermined shape (FIG. 5).
(B)). At this time, the etching residue 117 adheres to the side wall of the dielectric capacitor. The etching residue 117 is made of an etched photoresist material, a ferroelectric film material, and a reaction product between an etching gas and a ferroelectric film material.

When the photoresist 116 is removed using a resist stripper, an etching residue 117 that contacts the side surface of the capacitor lower electrode layer 113 and extends upward remains as shown in FIG. When a process by a physical / mechanical method for removing the etching residue 117 is performed, only the portion protruding upward is broken, and the etching residue 117 remains on the side surface of the capacitive element as shown in FIG. Becomes In such a state, the lower electrode and the upper electrode are electrically connected, and the function as a capacitor is impaired.

In order to avoid such a problem, the etching residue 117 is also removed by washing. Japanese Patent Application Laid-Open No. 10-12836 discloses that a cleaning solution such as hydrochloric acid, nitric acid, hydrofluoric acid, a mixed solution thereof, or 80 ° C.
A method for removing the etching residue using water and an organic solvent is disclosed. A process to which this cleaning step is added will be described with reference to FIGS.

FIG. 6B shows a state where the etching residue 117 has adhered to the side wall of the capacitor. In this state, cleaning is performed by immersing the substrate in a mixed solution of hydrochloric acid and water or a mixed solution of hydrofluoric acid and nitric acid. Thereby, the etching residue 117 is dissolved and removed as shown in FIG. However, since these cleaning solutions also dissolve the PZT film, the dissolution proceeds from the exposed portion of the PZT film, and a thinned portion is generated as shown in the figure. Here, P
Although the ZT film has been described as an example, a similar film reduction occurs in the case of another ferroelectric film.

[0011]

As described above, the method using an acid as a cleaning solution disclosed in Japanese Patent Application Laid-Open No. 10-12836 dissolves a reaction product precipitated as an impurity on a ferroelectric film. In addition to the removal, the ferroelectric film itself is dissolved. Since the properties of ferroelectric films depend on the composition, film thickness, etc.,
During cleaning, if the material itself is dissolved by the chemical solution, the properties will be adversely affected. Further, when the thickness of the ferroelectric film changes due to cleaning, there is a problem that the yield is reduced. Therefore, in order to perform the cleaning without deteriorating the characteristics of the ferroelectric film, it is necessary to minimize the erosion of the film by the chemical solution and perform the cleaning without changing the composition and the surface state.

Further, since the ferroelectric material has a high reactivity to chemicals, the conventional cleaning method using an acid adsorbs an acid component on the surface of the ferroelectric film to change the surface state, and the ferroelectric film or the like is not used. In some cases deteriorated. Further, there is a problem that the acid component easily remains on the surface of the ferroelectric film or the like. Since the remaining acid component has a bad influence on the semiconductor device, it is desirable to avoid such adverse effects. However, in this case, it is necessary to sufficiently rinse with pure water or the like, and an increase in the number of steps is inevitable.

Also, Japanese Patent Application Laid-Open No. 10-12836 discloses a method in which warm water at 80 ° C. or higher or an organic solvent is used as a cleaning liquid. However, as described above, extremely high cleanliness is required in recent manufacturing processes of ferroelectric films, and a method using hot water or an organic solvent as a cleaning liquid cannot sufficiently meet such requirements. Was.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and is intended to prevent the dissolution of a ferroelectric film and the deterioration of its surface while preventing the etching of a reaction product between a ferroelectric film material and an etching gas. An object is to provide a method for effectively removing residues.

[0015]

As described above, the removal of etching residues by acid cleaning in the prior art is based on the action of dissolving the etching residues.
However, an etching residue is mainly composed of a reaction product of a ferroelectric film material or the like and an etching gas, and a cleaning solution that can dissolve the etching residue also has a strong dissolution property for the ferroelectric film. Shows sex. In fact, a mixed solution of hydrochloric acid and water or a mixed solution of hydrofluoric acid and nitric acid has strong solubility in metal oxides used as ferroelectric films, such as perovskite-based materials such as PZT, and Ta ₂ O _5. Show. Therefore, it is desirable that the cleaning of the semiconductor device including the ferroelectric film is based on another action different from the action of dissolving the etching residue.

Although different from the cleaning of the ferroelectric film, the RCA cleaning is widely used as a method of cleaning a bare wafer before forming elements. In this cleaning, APM (a mixed solution of aqueous ammonia and hydrogen peroxide) is generally used as a cleaning liquid at the stage of removing particles. In this cleaning, the vicinity of the surface of the silicon to be cleaned is dissolved, and the cleaning is performed by the action of lifting off the adhered particles, and the lifted-off adhered particles and the surface of the silicon substrate are charged to the same charge. This is to prevent re-adhesion by the electrostatic repulsion of the formed electric double layer. Since ammonia dissolves the silicon substrate, particles can be effectively removed by a lift-off action. In this case, if the dissolution of silicon by ammonia progresses too much, the unevenness of the substrate surface becomes severe. Therefore, aqueous hydrogen peroxide is also used for the purpose of avoiding this adverse effect.

However, this cleaning is premised on dissolving the object to be cleaned with the cleaning liquid to obtain a lift-off effect, as described above, and thus is applied to removing etching residues attached to the ferroelectric film. That is not appropriate. In order to obtain a lift-off effect, the ferroelectric film constituting a part of the object to be cleaned must be dissolved,
This is because the object of the present invention of removing the etching residue while suppressing the film loss of the ferroelectric film cannot be achieved.

As described above, when removing the etching residue adhering to the ferroelectric film or the like, there is a restriction that the ferroelectric film must not be dissolved. Therefore, a cleaning method not based on the lift-off function is employed. It is desirable to conduct a study from a viewpoint different from that of particle removal of a bare wafer.

Further, after the ferroelectric film is dry-etched, an etching residue adhering to an exposed surface of the ferroelectric film or the like may be formed of a resist material, an etched ferroelectric film or a refractory metal material, or a metal and a refractory metal. Various substances such as reaction products with an etching gas are mixed. Since the object to be removed is different, it is necessary to perform cleaning by an operation different from that of the particle removal of the bare wafer from this point.

The present invention has been made based on the above points.

According to the present invention for solving the above problems, a step of forming a ferroelectric film on a semiconductor substrate, a step of forming a mask on the ferroelectric film, and using the mask to form the ferroelectric film There is provided a method of manufacturing a semiconductor device including a step of dry-etching a body film and a step of performing cleaning using an alkaline cleaning liquid.

Further, according to the present invention, a step of forming a laminated film including a refractory metal film and a ferroelectric film on a semiconductor substrate, forming a mask on the laminated film, and using the mask There is provided a method of manufacturing a semiconductor device including a step of dry-etching the stacked film and a step of cleaning with an alkaline cleaning liquid.

According to the method of manufacturing a semiconductor device described above, after the ferroelectric film or the laminated film including the ferroelectric film is dry-etched, cleaning is performed using an alkaline cleaning solution. As a result, the etching residue adhering to the resist, the ferroelectric film, and the refractory metal film is effectively removed.

The ferroelectric film is generally a metal oxide film and hardly dissolves in an alkaline liquid. Therefore, even if the ferroelectric film is cleaned with an alkaline cleaning solution, a lift-off effect is hardly obtained. However, as described below, as a result of experiments using various cleaning solutions, it was found that the alkaline cleaning solution exhibited an excellent particle removing effect. This is considered to indicate that the cleaning action by electrostatic repulsion plays a more important role in removing the etching residue attached to the ferroelectric film, unlike the removal of particles on the silicon substrate. Although the mechanism of cleaning the ferroelectric film with an alkaline cleaning solution is not always clear, the alkaline cleaning solution acts on the etching residue, the ferroelectric film, and the like, and the adhesion of the etching residue to the ferroelectric film and the adhesion of the etching residue to each other. It is presumed that the adhesive force is effectively reduced, whereby a remarkable cleaning effect is exhibited.

[0025]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention has a feature in cleaning an etching residue adhered to an exposed surface of a ferroelectric film. Therefore, the semiconductor device in the present invention is not particularly limited as long as it includes a ferroelectric film patterned by dry etching. Specifically, a capacitance element and the like can be given. In a capacitive element, the required level of prevention of composition deviation and surface modification of a ferroelectric film is high, and the effect of the present invention is more remarkably exhibited. In addition, since the present invention is characterized by cleaning the etching residue attached to the ferroelectric film, the type of the semiconductor substrate is not particularly limited. In addition to a silicon substrate, an SOI substrate or a III-V semiconductor material may be used. A substrate or the like can also be used.

The ferroelectric film of the present invention is used, for example, as a capacitive insulating film of a capacitive element. What is ferroelectric?
A material that has spontaneous polarization and has the property that it can be inverted by an electric field. Typically, a metal oxide having a perovskite structure can be given.

The ferroelectric film in the present invention refers to, for example, a metal oxide film having a relative dielectric constant of 10 or more. Among them, an oxide containing at least one selected from strontium, titanium, barium, zirconium, lead, bismuth, and tantalum is preferable. Specifically, BST (Ba
_x Sr _1-x TiO ₃ ), PZT (PbZr _x Ti _1-x O ₃ ),
_{PLZT (Pb 1-y La y} Zr x Ti 1-x O 3), SrBi 2
It is preferable that the film is a film made of a perovskite-based material such as Ta ₂ O ₉ .
0 ≦ x ≦ 1 and 0 <y <1. ). Alternatively, Ta ₂ O ₅ or the like can be used. When such a material is selected, the effects of the present invention are more remarkably exhibited. That is,
When these materials are applied to a capacitor, a large storage capacitance can be obtained, but there is a problem that it is difficult to remove an etching residue while suppressing a film loss and a characteristic deterioration of a ferroelectric film. . According to the method of the present invention, since such a problem is solved, the excellent characteristics of the above-mentioned material can be fully utilized.

In the present invention, the method for forming the ferroelectric film is not particularly limited. For example, in the case of a PZT film, it can be formed by a known method such as a sol-gel method, a sputtering method, and a CVD method.

In the present invention, after forming a laminated film including a high melting point metal film and a ferroelectric film, these may be dry-etched and then cleaned using an alkaline cleaning solution. At this time, the above-mentioned refractory metal film material, its compound, and the like are included as etching residues. In this case, a sufficient removal effect can be obtained by the alkaline cleaning liquid. Here, the high melting point metal film refers to a film used as a lower electrode and an upper electrode of a capacitor, for example. When used as an electrode of a capacitor, it is desirable that the material of the high melting point metal film be appropriately selected according to the material of the capacitor insulating film.

Various materials are used for the high melting point metal film, and Pt, Ir, Ru, TiN, WN, IrO ₂ ,
And one or more materials selected from the group consisting of RuO ₂ . This is because it has excellent chemical stability, heat resistance, and conductivity, and has characteristics suitable as an electrode material of a capacitor.

In the present invention, a mask is formed above the ferroelectric film or the laminated film. However, another film such as a high melting point metal may be formed between the ferroelectric film and the mask. Good. Further, the mask material is not particularly limited, and a mask containing SiO ₂ , Ta, Ti, SiN, W, or the like may be used in addition to the photoresist.

The alkaline cleaning liquid of the present invention is used for removing an etching residue by an electrostatic repulsion caused by being alkaline. Therefore, an etching residue can be removed with an alkaline liquid regardless of the type of the cleaning component.

The alkaline cleaning solution in the present invention may be any alkaline solution, but is preferably 8 or more, more preferably 9 or more, so that the etching residue can be more effectively prevented while preventing the ferroelectric film from being thinned. Can be removed. Further, by setting the pH to 13 or less, more preferably 12 or less, dissolution and surface roughness of the surface of the silicon oxide film formed on the semiconductor substrate can be suppressed.

The alkaline cleaning solution of the present invention preferably has an oxidation-reduction potential lower than the oxidation-reduction potential of the components of the ferroelectric film, and more preferably has a negative oxidation-reduction potential. A ferroelectric film having an oxidation-reduction potential higher than the oxidation-reduction potential of a composition component has a function of oxidizing an incompletely oxidized composition component existing near the surface of the ferroelectric film. In some cases, the surface of the body film may be deteriorated and its characteristics may be deteriorated. For example, APM
The oxidation-reduction potential of (ammonia-hydrogen peroxide solution) is a positive value and is higher than the oxidation-reduction potential of a metal oxide used as a ferroelectric film. For this reason, the surface of the ferroelectric film may be deteriorated and its characteristics may be impaired.

For the same reason as described above, it is preferable that the alkaline cleaning solution in the present invention does not contain an oxidizing agent or a reducing agent. In particular, when hydrogen peroxide, which can act as both an oxidizing agent and a reducing agent, is used in combination with the ferroelectric film, the hydrogen peroxide reacts with the ferroelectric film to cause self-decomposition and is included in the ferroelectric film In order to form a complex with a specific element (for example, Ti or the like) to cause a composition deviation on the surface, it is preferable to avoid using the same together.

As the alkaline cleaning solution in the present invention,
For example, a cleaning solution containing aqueous ammonia, amines, ammonium salts, and the like is used. Whichever one of them is selected, an electrostatic repulsion action due to being alkaline can be obtained, and an etching residue can be removed. However, more advantages can be obtained by selecting particular ones of the above. For example, it is preferable to contain one or more components selected from the group consisting of ammonia, tetramethylammonium hydroxide (TMAH), and trimethyl (2-hydroxy) ethylammonium hydroxide. By using a cleaning solution containing such components, it is possible to more effectively remove etching residues while preventing the ferroelectric film from being reduced in thickness. Further, there is little residual cleaning liquid, and the cleaning liquid is less likely to be adsorbed on the ferroelectric film and adversely affect the characteristics. Another advantage is that the rinsing step after washing can be simplified. Of these, aqueous ammonia is particularly preferred. The residual cleaning solution can be particularly reduced, and the rinsing step after cleaning can be significantly simplified. Further, it is easy to control the concentration of the cleaning liquid and the like, and it is possible to reduce the variation in the processing due to the fluctuation of the cleaning liquid composition.

As the alkaline cleaning solution in the present invention,
A solution containing electrolytic cathode water can also be used. Electrolytic cathode water refers to a liquid generated on the cathode side when, for example, pure water or water containing ammonium ions is electrolyzed. Since the electrolytic cathode water has a high reducing property due to the active hydrogen generated at the cathode, both the surface potential of the ferroelectric film and the surface potential of the etching residue can be negatively charged without deteriorating the surface of the ferroelectric film. Thereby, the etching residue can be effectively removed.

Electrolytic cathode water has a smaller etching effect on a silicon oxide film and the like than ammonia water and the like. Therefore, when it is necessary to minimize dissolution of the silicon oxide film and surface modification, use the electrolytic cathode water. It is desirable to do. For example, in the manufacturing process of a capacitive element,
In cleaning after the formation of the ferroelectric film and the electrodes sandwiching it,
As shown in FIG. 2B, cleaning is often performed with the silicon oxide film 108 (interlayer insulating film) exposed. If it is desired to particularly suppress the dissolution of the silicon oxide film 108, it is desirable to use electrolytic cathode water. DRA
In the manufacture of M, etc., SOG (Spin
On Glass) film or HSQ (Hydrogen Silisesquioxane)
Low dielectric constant films such as films are often used. Although the SOG film and the HSQ film have an advantage that the capacitance between wirings can be reduced because of their low dielectric constant, they also have a problem that their resistance to a chemical solution is low. For this reason, when an SOG film or the like is used as an interlayer insulating film, there may be a problem that the surface of the SOG film or the like is etched by the cleaning liquid or the surface is denatured to increase the dielectric constant. Therefore, in such a case, it is desirable to use electrolytic cathode water.

As a generator for obtaining electrolytic cathode water, a two-tank electrolysis type apparatus is generally used (1).
Electrochemical Handbook, 4th Edition, p. 277 etc.).
Raw water of electrolytic cathode water, that is, pure water or water containing a small amount (0.5% by weight or less) of ammonium ions is sent to each electrolytic cell, where it is electrolyzed by applying a DC voltage. Since the electrolytic cathode water obtained from the cathode side has a high reducing property due to active hydrogen generated at the cathode, etching residues can be effectively removed without adversely affecting the ferroelectric film, the SOG film and the like.

As the alkaline cleaning solution in the present invention,
Those containing a chelating agent can be used. The chelating agent refers to a compound having the ability to form a chelate complex with a metal or metal oxide, particularly an etching residue. Specifically, ethylenediaminetetraacetic acid (EDT
A), trans-1,2-cyclohexanediaminetetraacetic acid (CyDTA), nitrilotriacetic acid (NTA), diethylenetriaminepentaacetic acid (DTPA), N- (2-
(Hydroxyethyl) ethylenediamine-N, N ′, N ′
-Compounds such as triacetic acid (EDTA-OH), or salts thereof. When a salt is used, a salt that does not adversely affect the characteristics of the semiconductor device is preferable, and a salt that does not contain a metal such as an ammonium salt is particularly preferable. The content of the chelating agent is preferably 1 to 10,000 ppm, more preferably 10 to 1,0 ppm with respect to the alkaline washing liquid.
00 ppm. If the concentration is too low, a sufficient chelating effect cannot be obtained. Conversely, if the concentration is too high, organic substances remain on the substrate surface, deteriorating the performance of the semiconductor device, and costly waste liquid treatment is required. The use of such a chelating agent not only enhances the effect of removing the etching residue, but also can effectively prevent reattachment of the etching residue once removed.

When cleaning is performed in the present invention, it is preferable to apply ultrasonic waves. By doing so, the cleaning effect can be further enhanced. At this time, the frequency of the ultrasonic wave is preferably 800 kHz or more. 800
If the frequency is lower than kHz, the wafer may be damaged, and a sufficient cleaning effect by ultrasonic waves may not be obtained.

Various cleaning methods can be applied to the cleaning using the alkaline cleaning liquid in the present invention. For example, it can be performed by a dipping method, a spray method, a roll coating method, a spin coating method, or another mechanical method.

[0043]

EXAMPLES (Example 1) In this example, a model experiment was performed using a PZT film having a polystyrene latex adhered thereto. Using pure water or ammonia water as the cleaning liquid,
Washing by changing pH to various values, its washing effect and PZT
The degree of film reduction of the film was evaluated.

First, a plurality of 6-inch silicon wafers are prepared, and each of the silicon wafers has a thickness of 300 n
m PZT films were formed. The wafer was immersed in a dispersion of polystyrene latex. After drying the wafer surface, it was immersed in 1500 ml of a cleaning solution shown in Table 1 for 60 minutes to perform cleaning. The temperature of the cleaning liquid was 25 ° C. Then, it was thoroughly rinsed with pure water.

The wafer was evaluated for the amount of the ferroelectric film dissolved before and after the cleaning and the degree of removal of the polystyrene latex. The evaluation method is described below.

(Amount of Ferroelectric Film Dissolved) The cleaning solution after the completion of the cleaning was subjected to an ICP mass spectrometer (SPQ manufactured by SII).
6500) to determine Pb, Zr, and Ti. Based on this result, the amount of each element dissolved when the amount of each element contained in the ferroelectric film before cleaning was set to 100% was calculated. The average value of the dissolved amount of each element is referred to as “PZ
The results are shown in Table 1 and FIG.

(Remaining amount of latex) The appearance of the surface before and after washing was observed using a scanning electron microscope (SEM). The residual amount of latex was evaluated according to the following criteria. 5: The residue is remarkable. 4 ... The residue is slightly remarkable. 3 .... A little residue. 2 .... A little residue. 1 .... No residual latex is observed.

[0048]

[Table 1]

From the above results, the dissolution amount of the PZT film strongly depends on the pH of the cleaning solution, and it is necessary that the cleaning solution is alkaline in order to suppress the dissolution of the film, and it is particularly preferable that the pH is 9 or more. I understood. It was also found that within the above range, the higher the pH, the higher the effect of washing the latex.

Example 2 The temperature of the cleaning solution was set to 65 ° C.
Except that the pH value was changed, in the same manner as in Example 1,
Washing experiments and evaluations were performed. Table 2 shows the results.

[0051]

[Table 2]

From the above results, the amount of PZT film dissolved strongly depends on the pH of the cleaning solution, and it is necessary that the cleaning solution is alkaline in order to suppress the dissolution of the film. I understood. It was also found that within the above range, the higher the pH, the higher the effect of washing the latex.

(Embodiment 3) This embodiment shows an example of a method of manufacturing a semiconductor device provided with a capacitor including a ferroelectric film. This embodiment will be described with reference to FIGS.

First, a MOS transistor was formed on a silicon substrate 101 as shown in FIG. A silicon oxide film 102 serving as a gate oxide film was formed on the surface of the silicon substrate 101 by thermal oxidation to a thickness of about 10 nm. Next, a phosphorus-doped polysilicon 103 and a WSi 104
Were each formed to a thickness of 100 nm by the CVD method. Subsequently, the silicon oxide film 102, the phosphorus-doped polysilicon 103 and the WSi 104 were patterned to form a gate electrode. The gate length was 0.3 μm. Next, the impurity diffusion layer 105 was formed by ion implantation. As described above, the MOSFET was completed in the region separated by the element isolation oxide film 107 (FIG. 1).
(A)).

Next, as shown in FIG. 1B, a contact plug was formed. First, a silicon oxide film (BPSG) 108 containing boron was formed as an interlayer insulating film by a CVD method, and then planarized by a CMP method. Next, after opening the contact hole by etching, a Ti film 109 was formed as a barrier metal, and a tungsten film 110 was formed thereon. Thus, a tungsten plug was formed.

Next, as shown in FIG. 1C, a layer constituting a ferroelectric capacitor was formed. First, a Ti film and a TiN film were successively sputtered, and a 100 nm Pt film was formed thereon to form the capacitor lower electrode layer 113. Next, a PZT film 114 (film thickness 100 nm) was formed by a CVD method. As raw material gas, lead bis dipivaloyl methanate, titanium isopolopoxide, zirconium butoxide,
NO ₂ was used as an oxidizing agent. The substrate temperature during film formation is 40
0 ° C. and the total pressure of the gas in the vacuum vessel during film formation was 5 × 10
^-3 Torr. Subsequently, IrO ₂ and Ir were deposited by a sputtering method to form the capacitor upper electrode layer 115.

Next, as shown in FIG. 2A, a photoresist 116 was formed on the capacitor upper electrode layer 115. As a resist material, a cresol novolak resin was used.

Then, using the photoresist 116 as a mask, the capacitor lower electrode layer 113, the PZT film 114, and the capacitor upper electrode layer 115 were dry-etched into a predetermined shape (FIG. 2B). At this time, the etching residue 1 composed of a photoresist material, a ferroelectric film material, a reaction product of an etching gas and a ferroelectric film material, and the like.
17 adhere to the sidewalls of the dielectric capacitor.

This etching residue 117 was treated with 1 mM, pH
Washing was performed using 10 aqueous ammonia as a washing solution. The apparatus shown in FIG. 8 was used for cleaning. The cleaning tank 124 of the apparatus shown in the figure was filled with the above-mentioned ammonia water 121, and the wafer held by the holder 120 was immersed in the cleaning tank for 10 minutes. The temperature of the cleaning liquid was 25 ° C. At this time, the wafer 12 is controlled by the ultrasonic oscillator 123 installed in the lower part of the cleaning tank.
Ultrasonic waves having a frequency of 900 kHz were applied to No. 2. By performing the above cleaning, the etching residue 117 shown in FIG. 2B was removed (FIG. 3A).

Subsequently, the photoresist 116 was stripped off using a resist stripping solution to complete the PZT capacity.

In this embodiment, the capacitor lower electrode, the PZT film,
The method of patterning the capacitor by dry etching after forming the IrO ₂ / Ir capacitor upper electrode has been described. First, the capacitor lower electrode is patterned by dry etching, and then PZT is formed. An electrode may be formed and the upper electrode may be patterned. By using this method, a film to be subjected to dry etching becomes thin, and a finer pattern can be formed.

(Example 4) As the cleaning liquid for performing the cleaning after the step shown in FIG. 2B, the ammonia water (1) used in Example 3 was used.
500 mM EDTA as a chelating agent.
A semiconductor device was manufactured in the same manner as in Example 3 except that the one added with ppm (weight basis) was used.

Example 5 The cleaning solution used for the subsequent cleaning shown in FIG. 2B was changed to an aqueous solution of trimethyl (2-hydroxy) ethylammonium hydroxide (pH
A semiconductor device was manufactured in the same manner as in Example 3 except that 9) was used.

(Example 6) The same procedure as in Example 3 was carried out except that the electrolytic solution obtained by electrolysis was used instead of ammonia water as the cleaning solution for the subsequent cleaning shown in FIG. 2B. Thus, a semiconductor device was manufactured. This electrolytic cathode water was obtained by electrolyzing 0.5% by weight of aqueous ammonia.

(Comparative Example 1) A semiconductor device was manufactured in the same manner as in Example 3 except that dilute hydrochloric acid of pH 3 was used instead of ammonia water as the cleaning solution for the subsequent cleaning shown in FIG. 2B. .

(Comparative Example 2) The cleaning liquid used for the subsequent cleaning shown in FIG. 2B was changed to pure water (pH 7.0) instead of ammonia water.
A semiconductor device was manufactured in the same manner as in Example 3 except that the method (0) was used.

With respect to the semiconductor devices obtained in Examples 3 to 6 and Comparative Examples 1 and 2, the effect of removing the etching residue 117 and the degree of reduction of the ferroelectric film were evaluated. The evaluation was performed by observing a cross section with a scanning electron microscope (SEM). Table 3 shows the results. In Table 3, the dissolved amount of the PZT film and the remaining amount of the etching residue were evaluated according to the following criteria.

(Dissolved amount of PZT film) 5: Significantly reduced film 4: Slightly reduced film 3: Slightly reduced film 2: Slightly reduced film 1: Slightly reduced film * Not evaluated * 2 "And" 1 "are considered to be within the allowable range. (Residual amount of etching residue) 5: Remarkably residual 4 ... Remaining slightly excessive 3 ... Slight residual amount 2 ... Slight residual amount 1 ... No residual observed

[0069]

[Table 3]

In the method of Comparative Example 1, the etching residue 1
Although 17 was removed, the film thickness of the ferroelectric film was reduced. In the method of Comparative Example 2, although less than that of Comparative Example 1, a decrease in the ferroelectric film was observed. Further, the etching residue 117 was not sufficiently removed. On the other hand, according to the methods of Examples 3 to 6, the etching residue was sufficiently removed while suppressing the loss of the ferroelectric film.

According to the present invention, since cleaning after dry etching is performed using an alkaline cleaning liquid, effective cleaning can be performed without deteriorating the characteristics of the ferroelectric film.

[Brief description of the drawings]

FIG. 1 is a process sectional view illustrating a method for manufacturing a semiconductor device of the present invention.

FIG. 2 is a process sectional view illustrating the method for manufacturing the semiconductor device of the present invention.

FIG. 3 is a process sectional view illustrating the method for manufacturing the semiconductor device of the present invention;

FIG. 4 is a process sectional view illustrating a conventional method for manufacturing a semiconductor device.

FIG. 5 is a process sectional view illustrating a conventional method for manufacturing a semiconductor device.

FIG. 6 is a process sectional view showing a conventional method for manufacturing a semiconductor device.

FIG. 7 is a process cross-sectional view showing a conventional method for manufacturing a semiconductor device.

FIG. 8 is a schematic view of a cleaning apparatus that can be used in the method of manufacturing a semiconductor device according to the present invention.

FIG. 9 is a graph showing the relationship between the pH of a cleaning solution and the amount of PZT film dissolved and the amount of latex remaining.

[Explanation of symbols]

 Reference Signs List 101 silicon substrate 102 silicon oxide film 103 phosphorus-doped polysilicon 104 WSi 105 impurity diffusion layer 107 element isolation oxide film 108 silicon oxide film (BPSG) 109 Ti film 110 tungsten film 113 capacitor lower electrode layer 114 PZT film 115 capacitor upper electrode layer 116 Photoresist 117 Etching residue 120 Holder 121 Ammonia water 122 Wafer 123 Ultrasonic oscillator 124 Cleaning tank

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 5F004 AA09 DB08 DB13 5F083 AD24 FR02 JA14 JA15 JA35 JA38 JA40 JA43 JA53 JA56 MA06 MA17 PR03 PR05 PR21 PR40

Claims (15)

[Claims] A step of forming a ferroelectric film on a semiconductor substrate; a step of forming a mask on the ferroelectric film; and a step of dry-etching the ferroelectric film using the mask. Performing a cleaning using an alkaline cleaning liquid. A step of forming a laminated film including a refractory metal film and a ferroelectric film on a semiconductor substrate; forming a mask on the laminated film; and drying the laminated film using the mask. A method for manufacturing a semiconductor device, comprising: a step of performing etching; and a step of performing cleaning using an alkaline cleaning liquid. 3. The method according to claim 1, wherein the pH of the alkaline cleaning liquid is 8 or more. 4. The pH of the alkaline cleaning solution is 9 or more and 1 or more.
The method according to claim 3, wherein the number is 3 or less. 5. The method for manufacturing a semiconductor device according to claim 1, wherein said alkaline cleaning liquid has an oxidation-reduction potential lower than an oxidation-reduction potential of a component of said ferroelectric film. . 6. The alkaline cleaning liquid comprises ammonia,
6. The semiconductor device according to claim 1, further comprising one or more components selected from the group consisting of tetramethylammonium hydroxide and trimethyl (2-hydroxy) ethylammonium hydroxide. Production method. 7. The method for manufacturing a semiconductor device according to claim 1, wherein said alkaline cleaning liquid is ammonia water. 8. The method according to claim 1, wherein the alkaline cleaning liquid is a solution containing electrolytic cathode water. 9. The method for manufacturing a semiconductor device according to claim 1, wherein said alkaline cleaning liquid contains a chelating agent. 10. The chelating agent is ethylenediaminetetraacetic acid, trans-1,2-cyclohexanediaminetetraacetic acid, nitrilotriacetic acid, diethylenetriaminepentaacetic acid, N- (2-hydroxyethyl) ethylenediamine-N, N ′, N ′. 10. The method for manufacturing a semiconductor device according to claim 9, wherein the method is triacetic acid or a salt thereof. 11. The ferroelectric film comprises strontium,
The method according to claim 1, wherein the method is a metal oxide containing at least one selected from titanium, barium, zirconium, lead, bismuth, and tantalum. 12. The ferroelectric film is made of BST, PZT,
PLZT, SrBi _TwoTa_TwoO₉, And Ta_TwoO_FiveFrom
Characterized in that it is any membrane selected from the group consisting of
A method of manufacturing the semiconductor device according to claim 1.
Law. 13. The refractory metal film is made of Pt, Ir, R
_{u, TiN, WN, IrO 2} , and a manufacturing method of a semiconductor device according to any claims 2 to 12, characterized in that it comprises one or more materials selected from the group consisting of RuO _2. 14. The method of manufacturing a semiconductor device according to claim 1, wherein an ultrasonic wave is applied when the cleaning is performed. 15. A semiconductor device manufactured by the method for manufacturing a semiconductor device according to claim 1.