JPH1022274A - Etching method and manufacture of semiconductor device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve various problems caused by sputter etching such as removal of residue of an etching product regarding an etching method for sputter-etching a chemically stable film according to a mask pattern. SOLUTION: A mask pattern 13 is formed on an etching object 12. Then, ion which goes almost straight is cast at a first incident angle for removing the etching object 12 which is exposed from the mask pattern 13 by sputter- etching. Then, ion is cast at a second incident angle which is larger than the first incident angle for sputter-etching and an etching product 14 attaching to a side wall of the mask pattern 13 in the preceding etching process is removed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an etching method and a method for manufacturing a semiconductor device, and more particularly to an etching method for sputter-etching a chemically stable film according to a mask pattern, and a method for manufacturing a semiconductor device using the etching method. It relates to a manufacturing method.

[0002]

2. Description of the Related Art With the increase in the density of semiconductor devices, it has become necessary to use a capacitor having a high dielectric constant insulating film sandwiched between two electrodes. In this case, when an oxide film or the like having a low dielectric constant is formed on the surface of the electrode, the capacitance value decreases. Therefore, a chemically stable metal that does not form an oxide film on the surface is used as an electrode material. As such a metal, there is Pt or the like, but since it is a chemically stable metal, ordinary reactive ion etching (RIE) cannot be used to etch it.

As a method of etching a chemically stable metal film, there is considered a sputter etching method in which ions are applied to the metal film to physically perform etching so that constituent particles of the metal film are repelled by ion bombardment.

[0004]

However, there are few examples in which a chemically stable metal film such as a Pt film is etched by a sputter etching method. Further, in the case where the sputter etching method is used, since it is a physical etching method, there is a possibility that not only a film to be etched but also a base film may be etched, and it is desired to solve this problem.

[0005] In addition, there may be various problems accompanying sputter etching, and it is necessary to extract those problems and to solve them. The present invention has been made in view of the above-described problems of the conventional example, and it is possible to sputter-etch a chemically stable film according to a mask pattern, and to prevent etching of a base insulating film. It is an object of the present invention to provide an etching method capable of solving various problems associated with sputter etching and a method for manufacturing a semiconductor device using the etching method.

[0006]

The above object is achieved by the first invention.
A mask pattern is formed on the object to be etched.
And irradiating almost straight ions at the first incident angle
The object to be etched exposed from the mask pattern
First etching step for sputter etching and removal
And at a second incident angle greater than the first incident angle
Irradiation of the ions and sputter etching, the first
Adhering to the side walls of the mask pattern in the etching process
A second etching step for removing the etched products
The second invention is solved by an etching method having
The object to be etched is a Pt film, an Ir film, Ru.
Membrane, IrO _TwoMembrane or RuO_TwoSingle-layer film or this
A multilayer film comprising at least two of the above.
The third problem is solved by the etching method according to the invention of the third aspect.
Of the invention, in which reactive etching can be performed on the insulating film.
A first conductive film is formed, and a second conductive film is formed thereon.
Forming a mask pattern on the second conductive film
And irradiating substantially straight ions at a first incident angle.
The second conductive film exposed from the mask pattern by
First etching step for sputter etching and removal
And at a second incident angle greater than the first incident angle
Irradiation of the ions and sputter etching, the first
Adhering to the side walls of the mask pattern in the etching process
Etching step for removing the etched product
And etching the first conductive film by reactive etching.
Etching and removing steps.
The first conductive film according to the fourth aspect of the present invention,
i-layer, TiN single-layer film, or multi-layer film containing at least one of them
And the second conductive film is made of a Pt film, an Ir film, Ru
Membrane, IrO_TwoMembrane or RuO_TwoSingle-layer film or this
A third film characterized by being a multilayer film comprising two or more of the above.
The solution is achieved by the etching method according to
According to the etching method according to the third aspect of the invention,
The first conductive film and the second conductive film
After the electrodes are formed, a capacitor is formed on the second conductive film.
Forming an insulating film to be an insulating film;
Forming a third conductive film and a fourth conductive film on the second electrode;
Forming a semiconductor device.
The first and fourth aspects of the present invention are solved by a sixth aspect.
The electric film may be a single-layer film of a Ti film or a TiN film or may include at least one of them.
Wherein the second and third conductive films are Pt films,
Ir film, Ru film, IrO_TwoMembrane or RuO_TwoSingle layer of membrane
A fifth film characterized by being a film or a multilayer film thereof.
Solved by the method of manufacturing a semiconductor device according to the invention,
In a seventh aspect, the insulating film is a strontium titanate.
Film (SrTiO)_ThreeFilm), strontium titanate
Lithium film (Ba_xSr_1-xTiO_ThreeFilm), zirconium titanate
Lead conate membrane (PbZr_1-xTi_xO_ThreeFilm) or tantalum
Strontium bismuth acid film (SrBi_TwoTa_TwoO
₉Film) according to the fifth or sixth aspect of the present invention.
The problem is solved by the above-described semiconductor device manufacturing method.

In the present invention, first, substantially straight ions are incident on the object to be etched exposed from the mask pattern at a first incident angle to be etched, and after the etching, the second ions larger than the first incident angle are etched. Etching is performed at different incident angles. At the first incident angle, that is, when the milling angle of the object to be etched with respect to the plane is small, the object to be etched exposed from the mask pattern is mainly anisotropically etched, and the second object, which is larger than the first incident angle, is etched. At the angle of incidence, that is, when the milling angle of the etching target to the plane becomes large and the milling angle of the etching product of the side wall to the plane becomes small, the etching product attached to the side wall is mainly anisotropically etched. .

As described above, by performing etching with the incident angle changed in two stages, a chemically stable object to be etched is sputter-etched and no etching product is left on the side wall of the mask pattern. Can be. Also, a first conductive film capable of reactive etching on an insulating film as an object to be etched, for example, a Ti film, TiN
A single-layer film or a multilayer film containing one or more of these films is formed, and a second conductive film such as a Pt film, an Ir film, a Ru film,
A single-layer film of an IrO ₂ film or a RuO ₂ film, or a multilayer film thereof is formed.

[0009] Since the first conductive film is provided under the second conductive film, the insulating film can be protected from excessive etching during sputter etching of the second conductive film. Especially,
By using a Ti film or a TiN film as the first conductive film, selectivity for sputter etching with the second conductive film can be provided. In addition, since the first conductive film can be subjected to reactive etching, the first conductive film must have an etching selectivity with the insulating film by appropriately selecting an etching type when etching the first conductive film. Can be. Therefore, even when the first conductive film is excessively etched, the insulating film can be prevented from being etched.

A TiN film or the like has a high barrier property against silicon from an underlying insulating film. Further, when a high dielectric constant insulating film serving as a capacitor insulating film is formed on the second conductive film formed of a Pt film or the like, the Pt film or the like is supplied from the high dielectric constant insulating film because it is chemically stable. Oxygen can be prevented from forming a metal oxide film having a low dielectric constant on the surface of the second conductive film.

As described above, it is possible to prevent the capacitance value of the capacitor from decreasing.

[0012]

Embodiments of the present invention will be described below with reference to the drawings. (1) Investigation by the inventor of the present application First, an etching method of a chemically stable metal film was investigated, and problems related to the etching method were grasped.

An experiment in which a Pt film is etched by an ECR etching method will be described below. As an etching gas, Ar alone or a reactive gas CF
₄ was used. According to the result, as shown in Table 1, even when the reactive gas CF ₄ to Ar also added Ar alone etching rate (E.R.) does not change.

[0014]

[Table 1]

From this, it can be seen that the Pt film and the like are not chemically etched, but are only physically etched. FIGS. 10A to 10C are cross-sectional views showing a method of etching a chemically stable metal film by sputter etching which is a physical etching method. A milling device is used as an etching device, and Ar ions are used as an etching species.

First, as shown in FIG. 10A, a chemically stable metal film, for example, a Pt film 2 having a thickness of 120 nm is formed on an insulating film 1, and then a resist film having a thickness of 1.2 μm is formed. By patterning, a mask pattern 3 is formed. next,
As shown in FIG. 10B, the Ar gas pressure is 0.2 mTorr.
r, an applied DC voltage of 600 V, and an applied current of 212 mA, irradiating Ar ions and applying P
The t film 2 is etched. At this time, Ar ions reach the Pt film 2 exposed between the mask patterns 3,
The incident angle of Ar ions is set to an angle close to normal incidence.

After a predetermined time, the Pt film 2 is etched, and the Pt film 2a remains under the mask pattern 3. After that, as shown in FIG.
The mask pattern 3 is removed by ashing under the condition of rr for 10 minutes. However, in the above etching method,
When the Pt film 2 is etched according to the mask pattern 3, as shown in FIG. 10B, an etching product (fence) 4 is re-attached to the side wall of the mask pattern 3, and even if the mask pattern 3 is removed, It will remain as it is. This etching product 4 is removed in a later step to form Pt.
Short circuit between the films 2a, or as a particle, CV
This may cause contamination of the D device or the like. As shown in Table 1, this etching product 4 is also generated by the ECR etching method, and is considered to be an inevitable problem when etching a chemically stable metal film.

In addition, because of the sputter etching, selectivity between the Pt film 2 and the underlying insulating film 1 cannot be obtained.
As shown in (b), the insulating film 1 is over-etched.
Is considerably etched. For this reason, the step becomes large, and it becomes difficult to form a multilayer film thereon. Hereinafter, an embodiment of the present invention that can solve these problems will be described.

(2) First Embodiment of the Present Invention It has been found from the above investigation that etching of chemically stable metal is limited to sputter etching. Since the ions used for the sputter etching have high directivity, the etching rate is expected to change in the sputter etching depending on the incident angle of the ions on the surface to be etched. This was confirmed using the following sputter etching apparatus. The survey method and results are described below.

First, as an example of a sputter etching apparatus, a milling apparatus capable of changing an incident angle of ions on a surface to be etched will be described with reference to FIG. FIG. 5 is a schematic diagram showing a schematic configuration of the milling device. 3
1 is a partition wall in which the inside becomes the etching chamber 31a. Reference numeral 34 denotes an object to be etched attached to the partition wall 31 which generates Ar ions and which is to be etched 35 in the etching chamber 31a.
This is an ion gun that emits light toward.

Reference numeral 32 denotes an electron supply plate provided in the etching chamber 31a. Electrons emitted from the electron supply plate 32 neutralize Ar ions reaching the etching target 35, and charge the etching target 35. To prevent. Reference numeral 33 denotes a holder for the object 35 to be etched, which is provided at a position facing the ion gun 34. The holder 33 is an object 35 to be etched.
Is rotated around an axis parallel to the mounting surface of the object 35 to be etched, and the incident angle α of Ar ions on the surface to be etched can be changed.
Here, the incident angle α is an angle between a direction perpendicular to the mounting surface of the holder 33 and the irradiation direction of Ar ions. The holder 33 rotates around a central axis perpendicular to the mounting surface. By rotating the holder 33 during Ar ion irradiation, Ar ions are maintained while maintaining a constant incident angle α in all directions. Irradiation.

Using this device, the milling angles θ ₁ , θ ₂
Was examined for the etching rate of the Pt film. The milling angle θ ₁ is equal to the incident angle α. The milling angle θ ₂ is equal to the incident angle of Ar ions on the side wall perpendicular to the plane, and is expressed by 90 ° −α (= θ ₁ ). FIG. 6 shows the result. As shown in the figure, usually milling angle theta ₁
Increases as the etching rate increases,
When the milling angle θ ₁ is 45 °, it becomes almost maximum. When milling angle theta ₁ is becomes large beyond the 45 ° etching rate is decreased to the contrary, the etching rate is small at 60 ° or more. However, the etching rate of Pt, Ir, etc., decreases as the milling angle θ ₁ increases.

On the basis of the results of such investigations, the following etching methods are conceivable in order to etch the Pt film (object to be etched) and to remove etching products adhering to the side walls of the mask pattern. That is,
First, in order to etch the Pt film exposed between the mask patterns, Ar ions are incident from a direction substantially perpendicular to the plane of the Pt film so as not to be disturbed by the mask pattern.
In this case, the milling angle θ ₁ is small, and the incident angle on the side wall perpendicular to the plane of the Pt film (milling angle θ ₂ ) is large. As a result, Pt exposed between mask patterns
Mainly anisotropic etching of the film.

After the etching is completed, the incident angle α of Ar ions is increased. That is, the milling angle θ ₁ is increased, and the milling angle θ ₂ to the side wall perpendicular to the plane of the Pt film is increased.
Smaller. Thereby, the anisotropic etching for the etching product attached to the side wall is mainly performed. FIG.
2A to 2C are cross-sectional views showing a method for etching a chemically stable metal film according to the first embodiment of the present invention. FIG. 2B is a plan view, and a cross-sectional view taken along a line II corresponds to the cross-sectional view of FIG. The milling device shown in FIG. 5 was used as an etching device, and Ar ions were used as an etching species.

First, as shown in FIG. 1A, a Pt film (to-be-etched) 12 having a thickness of 120 nm is formed on a silicon oxide film (insulating film) 11 on a silicon substrate (not shown). 0.3 μm width × 0.8 μ length on Pt film 12
A plurality of mask patterns 13 having a thickness of m and a thickness of 0.76 μm are formed at an interval of 0.3 μm. Next, the holder 3 shown in FIG.
The silicon substrate is placed on 3 and the holder 33 is rotated.
Subsequently, as shown in FIG.
Under the conditions of V and an applied current of 212 mA, Ar ions are irradiated, and the Pt film 12 is etched according to the mask pattern 13. At this time, as shown in FIG. 5B, the incident angle α of the Ar ions is set to 15 ° so that the Ar ions reach the Pt film 12 exposed between the mask patterns 13. The reason why the angle of incidence α of the Ar ions is slightly inclined from the vertical direction is to prevent backflow to the ion gun 34 due to recoil of the Ar ions. As a result, the milling angle θ ₁ is small and the milling angle θ ₂ is large, and the anisotropic etching of the Pt film 12 exposed between the mask patterns 13 is mainly performed.

After a lapse of 3 minutes, the Pt film 12 at a portion not covered by the mask pattern 13 is etched, and the Pt film 12a remains under the mask pattern 13. As a result, a line and space of about 0.3 μm is formed. At this time, it is assumed that the etching products 14 adhere to the side walls of the mask pattern 13 again. Then, as shown in FIG. 1 (c), the incident angle α of Ar ions is changed to 60 °, and Ar ions are further irradiated under the conditions of an applied DC voltage of 1000 V and an applied current of 0.5 mA. As a result, the milling angle θ ₂ is small and the milling angle θ ₁ is large,
The anisotropic etching of the etching products 14 on the side walls is mainly performed.

As the etching products 14 begin to be removed by the irradiation of Ar ions, the upper portion of the mask pattern 13 which is not shadowed by the adjacent mask pattern is etched. When the incident angle α is large, at the early stage of the etching, the incidence on the side wall of the mask pattern 13 is hindered by the adjacent mask pattern, and the etching products 14 attached to the lower side of the side wall of the mask pattern 13
Does not reach the Ar ion irradiation. However, when the upper portion of the adjacent mask pattern is removed with the passage of time, the irradiation of Ar ions reaches the lower portion of the side wall of the mask pattern 13, and all the etching of the side wall of the mask pattern 13 is performed. Product 14 is removed.

Thereafter, as shown in FIG. 2A, when the mask pattern 13 is removed by ashing under the condition of an oxygen gas pressure of 1.5 Torr for 10 minutes, it becomes approximately 0.3 μm.
Line and space appears. As described above, according to the first embodiment of the present invention, first, Ar ions are incident from a direction almost perpendicular to the surface of the Pt film 12 exposed between the mask patterns 13, and etching is performed. After the etching, the etching is continued by changing the incident angle α to a large angle. When the milling angle θ ₁ is small, the Pt film 12 exposed between the mask patterns 13 is mainly anisotropically etched, and when the milling angle θ ₂ is small, the etching products 14 attached to the side walls are mainly anisotropically etched. .

As described above, by performing etching in which the incident angle α is changed in two stages, chemically stable Pt is obtained.
The film 12 is sputter-etched and the mask pattern 1
The etching product 14 can be prevented from being left on the side wall of the third. In the above-described first embodiment, although the etching products 14 on the side walls of the mask pattern 13 can be removed, the underlying insulating film 1 is formed by a physical etching method.
1 is etched. In order to prevent this, it has been considered that the object to be etched should have a multilayer structure including a plurality of different types of conductive films, and each conductive film should have a necessary role. For example, a Ti film, T
An iN film, an Ir film, and a Pt film are stacked. The Pt film is a chemically stable film, and can suppress bonding with oxygen when in contact with a high dielectric insulating film. The Ir film is also a film stable to chemical determination, but its main role is to prevent oxygen diffusion. The TiN film is a film that can be chemically etched, and has a barrier property to silicon. The Ti film is also a film that can be chemically etched, and also has a role to adhere to the insulating film.

In the case of the above-mentioned structure, it is important to determine whether the Pt film and the Ir film and the TiN film have selectivity for sputter etching, and whether the film has dependency on the incident angle. The following experiment was performed to confirm these. An experimental sample in which a TiN film, an Ir film, and a Pt film were respectively formed on an insulating film, and an experimental sample of a TEOS-SiO ₂ film itself were prepared, and the etching rate (nm /
Min) was investigated. Incident angle α is 15 °, 30 °, 45 °
And 60 °.

FIG. 6 shows the experimental results. The vertical axis indicates the etching rate (nm / min) on a linear scale, and the horizontal axis indicates the milling angle α (°) on a linear scale.
As shown in the figure, when α = 15 ° to 45 °, the etching rate of the TiN film is less than half the etching rate of the Pt film and the Ir film, and the selective etching is possible. It can be used as a base film of an Ir film. Note that α = 3 for the TEOS-SiO ₂ film.
At 0 °, the etching rate was almost the same as that of the Pt film or the Ir film, and it was confirmed that there was no selectivity to the Pt film or the Ir film.

(2) Second Embodiment of the Present Invention FIGS. 3A to 3C, 4A and 4B are cross-sectional views showing an etching method according to a second embodiment. is there. What is different from the first embodiment is that a film that protects the insulating film from being excessively etched when the Pt film is etched between the Pt film and the insulating film and has a high barrier property against silicon from the underlying insulating film. That is sandwiched between.

First, as shown in FIG. 3A, a 20 nm thick Ti film 22 and a 50 nm thick TiN film 2 are formed on a silicon oxide film (insulating film) 21 on a silicon substrate (not shown).
3. 100 nm thick Ir film 24 and 50 nm thick P
The t film 25 is formed. Note that the Ti film 22 and the TiN film 2
3 constitutes a first conductive film, and an Ir film 24 and a Pt film 25
Constitute the second conductive film.

Next, after forming a resist film on the Pt film 25, patterning is performed, and the width is 0.3 μm × length 0.8 μm.
A plurality of mask patterns 26 each having a thickness of m and a thickness of 0.76 μm are formed at intervals of 0.3 μm. Next, the silicon substrate is placed on the holder 33 of FIG. 5, and the holder 33 is rotated. Subsequently, as shown in FIG. 3B, Ar ions are irradiated at an applied DC voltage of 1000 V and an applied current of 0.5 A, and the Pt film 25 and the Ir film 24 are etched according to the mask pattern 26. At this time, A ions are formed so that Ar ions reach the Pt film 25 and the Ir film 24 exposed between the mask patterns 26.
The incident angle α of the r ion is 15 °. In this case, the milling angle theta ₁ is as small as 15 °, whereas, milling angle theta ₂ to the membrane surface of the side wall is as large as approximately 75 °. Therefore, the Pt film 25 and the Ir film 24 exposed between the mask patterns 26 are mainly anisotropically etched.

After a lapse of 3 minutes, the Pt film 25 and the Ir film 24 exposed between the mask patterns 26 are etched, and the Pt film 25a and the Ir film 24a are formed under the mask pattern 26.
Remains. At this time, since the underlying TiN film 23 has a low etching rate, it is hardly etched even if there is some over-etching. It is assumed that the etching product 27 adheres again to the side wall of the mask pattern 26.

Next, as shown in FIG. 3C, the incident angle α of the Ar ions was changed to 60 °, and the applied DC voltage was further increased.
Ir ions are irradiated at 1000 V and an applied current of 0.5 A. In this case, the milling angle theta ₁ to the horizontal of the film surface becomes large and 60 °, whereas, milling angle theta ₂ to the membrane surface of the side wall is approximately 30 ° smaller. Therefore, the etching products on the side walls are mainly anisotropically etched.

The irradiation of Ar ions removes the etching products 27 on the mask pattern 26 which are not shadowed by the adjacent mask pattern, and the adjacent mask pattern is also etched from above. When the incident angle α is large, the adjoining mask pattern impedes the incidence on the side wall of the mask pattern 26 at the beginning of the etching, and the etching product 27 attached to the lower side of the side wall is irradiated with Ar ions. Does not arrive.
However, as the time elapses, when the upper part of the adjacent mask pattern is removed, the Ar ion irradiation also reaches the lower part of the side wall of the mask pattern 26, and after about three minutes, the side wall of the side wall is removed. All etching products 27
Is removed.

Next, as shown in FIG.
By RIE using a mixed gas of Cl ₂ of 0 ccm and CHCl ₃ at a flow rate of 200 ccm, a gas pressure of 20 mTorr,
Under the condition of RF power of 200 W, the TiN film 23 is kept for 1.5 minutes.
And the Ti film 22 is etched. At this time, the mask pattern 26, the Pt film 25a, and the Ir film 24a function as a mask, and the TiN
The film 23a and the Ti film 22a remain. As a result, a laminated structure 30 of the conductive film is formed, and a line and space of 0.3 μm is formed. The underlying silicon oxide film 2
No. 1 is hardly etched by a mixed gas of Cl ₂ + CHCl ₃ .

Thereafter, as shown in FIG. 4B, when the mask pattern 26 is removed by ashing for 10 minutes under the condition of an oxygen gas pressure of 1.5 Torr, a line and space appears. As described above, according to the second embodiment, the object to be etched is Ti from the silicon oxide film 21 side.
It has a laminated structure of a film 22, a TiN film 23, an Ir film 24, and a Pt film 25.

When the Pt film 25 and the Ir film 24 are etched, the TiN film 23 having etching selectivity is used as a base, so that over-etching and an increase in level due to the over-etching are prevented, and the silicon oxide film 21 is removed. It can protect against over-etching. Further, since the TiN film 23 and the like have a high barrier property against silicon from the underlying silicon oxide film 21, it is possible to prevent a silicon oxide film or the like from being formed on the surface of the Pt film 25.

(3) Third Embodiment of the Present Invention Based on the above-described embodiment, a high-dielectric-constant insulating film is sandwiched between the electrodes having the above-mentioned laminated structure according to the third embodiment of the present invention. A method of manufacturing a semiconductor device having a capacitor having a flexible structure will be described with reference to FIGS. 7 (a) to 7 (c), 8 (a), (b) and FIG.

FIG. 9 is a sectional view showing the structure of the whole semiconductor device. As shown in the figure, gate electrodes G1 and G2 are formed on a silicon substrate 41 with gate insulating films GI1 and GI2 interposed therebetween.
Are formed. A source region S1 and a drain region D1 are formed on the silicon substrate 41 on both sides of one gate electrode G1, and a source region S2 and a drain region D2 are formed on the silicon substrate 41 on both sides of the other gate electrode G2. These are covered with an insulating film 42a made of a silicon oxide film, and lower electrodes 51a and 51b of the capacitor are formed on the insulating film 42a. Lower electrode 51
a, 51b are connected to the source regions S1, S2 via plugs 43a, 43b embedded in the openings of the insulating film 42a.

Further, a high dielectric constant insulating film 42b having a thickness of 50 to 300 nm is formed on the lower electrodes 51a and 51b.
An upper electrode 52 is formed to cover the entire surface. The lower electrodes 51a and 51b, the high dielectric constant insulating film 42b, and the upper electrode 52 constitute a capacitor. As the high dielectric constant insulating film 42b, a strontium titanate film having a relative dielectric constant of 200 to 300 (STO film: SrTiO ₃
Film) and a strontium barium titanate film having a relative dielectric constant of 500 (BST film: Ba _x Sr _1-x TiO 2)
₃ film), or strong zirconate titanate San'namarimaku a dielectric _{(PZT: PbZr 1-x Ti} x O 3 film) or strontium bismuth tantalate film (SBT: SrBi ₂ Ta ₂
O ₉ film) can be used. Also, the lower electrode 51
Reference numerals a and 51b denote a 50 nm-thick Pt film from the side in contact with the high dielectric constant insulating film 42b,
It is an Ir film, a TiN film and a Ti film having a thickness of 100 nm. The total thickness of both the TiN film and the Ti film is 50 nm.
It is. Each metal film has a role as described in the second embodiment.

Next, a method of manufacturing the above semiconductor device will be described. 7A to 7C, 8A,
FIG. 4B is a cross-sectional view illustrating a step of manufacturing the lower electrode of the capacitor. First, as shown in FIG. 7A, after plugs 43a are buried in openings of an insulating film 42a made of a silicon oxide film, a Ti film 4 is formed thereon by sputtering.
4, a TiN film 45, an Ir film 46, and a Pt film 47 are sequentially formed. Note that the Ti film 44 and the TiN film 45 constitute a first conductive film, and the Ir film 46 and the Pt film 47 constitute a second conductive film.

Subsequently, after a resist film is formed on the lower electrode 51a, it is patterned and a mask pattern 48 having a thickness of about 760 nm covering a region where the lower electrode 51a is to be formed.
To form Next, as shown in FIG. 7B, the Pt film 47 is formed by ion milling using Ar ions under the conditions of an applied DC voltage of 1000 V and an applied current of 0.5 A according to the mask pattern 48 while rotating the holder 33. And I
The r film 46 is etched. At this time, Ar ions are irradiated at an incident angle α of about 15 ° on the film surface of the object to be etched. In this case, the milling angle θ ₁ is as small as 15 °, while the milling angle θ ₂ to the film surface of the side wall is approximately 7 °.
It becomes as large as 5 °. Therefore, the Pt film 47 and the Ir film 46 exposed between the mask patterns 48 are mainly anisotropically etched.

By maintaining this state for 3 minutes, the exposed Pt film 47 and the Ir film 46 are removed, and the Pt film 47a and the Ir film 46a are left in the portion covered by the mask pattern 48. At this time, the underlying TiN film 45 is exposed in the traces of removal of the Pt film 47 and the Ir film 46, and is exposed to Ar ions. However, since the etching rate is low, the TiN film 45 hardly remains even if there is some over-etching. Not etched. After the etching, the mask pattern 48 is formed.
It is assumed that an etching product 49 adheres to the side wall of.

Next, as shown in FIG.
3, the angle of incidence of Ar ions on the film surface of the object to be etched is set to about 60 °, and the etching is continued for 3 minutes under the conditions of an applied DC voltage of 1000 V and an applied current of 0.5 A. With increasing the milling angle theta ₁ by the incident angle α of about 60 °, to reduce the milling angle θ ₂ (30 °). Thus, the etching product 49 on the side wall of the mask pattern 48 is mainly anisotropically etched.

At this time, when the adjacent mask patterns 48 are separated from each other, one of the mask patterns 48 does not form a shadow of the other mask pattern 48. Is exposed to Ar ions from the beginning of etching, and is anisotropically etched. On the other hand, if the distance between adjacent mask patterns 48 is not so large, one mask pattern becomes a shadow of the other mask pattern 48, and only the etching products 49 on the upper side walls of the mask pattern 48 are initially formed. Not exposed to Ar ions. As time elapses, the upper part of the adjacent mask pattern is removed, and the removed part gradually moves to the lower part. As a result, the etching products 49 under the side walls of the mask pattern 48 that were not exposed to Ar ions in the initial stage of etching are also exposed to Ar ions and removed.

After the etching products 49 on the side walls of the mask pattern 48 are removed, as shown in FIG.
The TiN film 45 and the Ti film 44 exposed between the mask patterns 48 are etched by RIE using a mixed gas of l ₂ + CHCl _{3 under} the same conditions as in the second embodiment. Thus, the lower electrode 51a is formed. At this time, the insulating film 42a is hardly etched by Cl ₂ + CHCl ₃ .

Next, as shown in FIG. 8B, when the mask pattern 48 is removed under the same conditions as in the first embodiment by ashing using oxygen, the lower electrode 51a is removed.
Is completed. Thereafter, as shown in FIG. 9, after forming a high dielectric constant insulating film 42b, the lower electrode 51 is formed thereon.
The same Pt film, Ir film, etc. as those of a and 51b are formed. Thereby, a capacitor is created.

As described above, according to the method of manufacturing a semiconductor device of the third embodiment, when forming the lower electrodes 51a and 51b, no etching product 49 remains. Thereby, the lower electrode 5 due to the etching product 49 is formed.
It is possible to prevent short-circuiting between 1a and 51b or contamination of a CVD apparatus or the like due to generation of particles.

Moreover, the underlying TiN film 45 and insulating film 42a
Is not etched, it is possible to avoid the problem that the step becomes large and it becomes difficult to form a multilayer film thereon. Further, when the high dielectric insulating film 42b and the upper electrode 52 are formed on the lower electrodes 51a and 51b, the gap between the upper electrode 52 and the lower electrodes 51a and 51b becomes narrow due to an increase in the level difference. Accordingly, it is possible to avoid problems such as a decrease in insulation, an increase in parasitic capacitance, and a variation in capacitance value of the capacitor.

In the second and third embodiments, a stacked structure of the Ti films 22, 44 and the TiN films 23, 45 is used as the first conductive film to be the lower electrodes 30, 51a, 51b. However, a single-layer film of a TiN film or a Ti film or a multilayer film containing one or more of these may be used. Also, the second
Pt films 24 and 47 and Ir films 25 and 4
6 is used, but has other oxidation-resistant and oxygen-barrier properties and is chemically stable, such as another conductive film, Pt film, Ir film, or the like.
A single-layer Ru film, an IrO ₂ film, a RuO ₂ film, or a multilayer film of two or more of these may be used.

Further, a silicon oxide film 21 as an insulating film,
42a is used, but another insulating film, for example, a PSG film,
A BPSG film or a silicon nitride film may be used. Further, although Ar ions are used as ions for sputter etching, other various ions may be used regardless of activity or inactivity. Further, the first incident angle is set to 15 ° and the second incident angle is set to 60 °, but the present invention is not limited to this. Furthermore, if the objects to be etched are different,
Since it is considered that the dependence of the etching rate on the incident angle shown in FIG. 6 also differs, in such a case, it is necessary to appropriately change the first incident angle and the second incident angle to appropriate values.

Further, if the ion incidence angle (anisotropic) can be appropriately changed by RIE, it can be used.

[0056]

As described above, according to the present invention, the etching of the object to be etched and the etching of the etching product adhering to the side wall can be selectively performed by performing the etching at two different incident angles. It can be carried out. Therefore, the object to be etched can be sputter-etched and no etching product remains on the side wall of the mask pattern. Accordingly, a short circuit between the patterned objects to be etched due to the etching product can be prevented, and the contamination of the CVD apparatus or the like by particles or the like can be prevented.

A first conductive film that can be reactively etched is formed on an insulating film as an object to be etched, and a second conductive film is formed thereon. Therefore, at the time of sputter etching of the second conductive film, the insulating film can be protected from excessive etching by the first conductive film. Further, since etching selectivity can be provided between the first conductive film and the insulating film, the insulating film is prevented from being etched even when the first conductive film is excessively etched. Can be. Thereby, the formation of steps can be prevented, so that it is easy to form a multilayer film thereon, and a second conductive film or the like is used as a lower electrode,
When a capacitor insulating film and an upper electrode are formed on them, the distance between the upper and lower electrodes is maintained, so that a decrease in insulating properties and a variation in the capacitance value of the capacitor are prevented. Can be.

Further, the TiN film and the like as the first conductive film prevent the diffusion of silicon from the underlying insulating film.
A low dielectric constant silicon oxide film or the like can be prevented from being formed on the surface of the conductive film. Further, since the Pt film or the like as the second conductive film is chemically stable, when a high dielectric constant insulating film serving as a capacitor insulating film is formed thereon, the second conductive film is formed by oxygen supplied from the high dielectric constant insulating film. A low dielectric constant metal oxide film or the like can be prevented from being formed on the surface of the conductive film.

As described above, it is possible to prevent the capacitance value of the capacitor from decreasing.

[Brief description of the drawings]

FIGS. 1A to 1C are cross-sectional views (part 1) illustrating an etching method according to a first embodiment of the present invention.

FIG. 2A is a sectional view (part 2) illustrating an etching method according to the first embodiment of the present invention; FIG. 2B is a plan view, and corresponds to a cross-sectional view taken along line II of FIG. 2A.

FIGS. 3A to 3C are cross-sectional views (part 1) illustrating an etching method according to a second embodiment of the present invention.

FIGS. 4A and 4B are cross-sectional views (part 2) illustrating an etching method according to a second embodiment of the present invention.

FIG. 5A is a configuration diagram of a milling apparatus used in an etching method according to an embodiment of the present invention,
FIG. 5B is a partial cross-sectional view of a portion to be etched during ion milling.

FIG. 6 is a characteristic diagram showing a milling angle dependency of an etching rate of an object to be etched used in the etching method according to the embodiment of the present invention.

FIGS. 7A to 7C are cross-sectional views (part 1) illustrating an etching method according to a third embodiment of the present invention.

FIGS. 8A and 8B are cross-sectional views (part 2) illustrating an etching method according to a third embodiment of the present invention.

FIG. 9 is a cross-sectional view illustrating a semiconductor device manufactured by an etching method according to a third embodiment of the present invention.

FIGS. 10A to 10C are cross-sectional views illustrating sputter etching of a Pt film according to an experiment performed by the present inventor.

[Explanation of symbols]

 11, 21, 42a silicon oxide film, 12, 12a, 25, 25a, 47, 47a Pt film, 13, 26, 48 mask pattern, 14, 27, 49 etching product, 15 concave portion of silicon oxide film, 22, 44 , 44a Ti film, 23, 45, 45a TiN film, 24, 46, 46a Ir film, 28 laminated structure of chemically stable film, 29 laminated structure of barrier film, 30 laminated structure of object to be etched, 31 partition wall 31a etching chamber, 32 electron supply plate, 33 holder, 34 ion gun, 41 silicon substrate, 42b high dielectric constant insulating film, 43a, 43b plug, 51a, 51b lower electrode, 52 upper electrode, S1, S2 source region, D1, D2 drain region, G1, G2 gate electrode, GI1, GI2 gate insulating film.

Continued on the front page (51) Int.Cl. ⁶ Identification code Agency reference number FI Technical indication H01L 21/8242

Claims (7)

[Claims] 1. A step of forming a mask pattern on an object to be etched, and irradiating substantially straight ions at a first incident angle to sputter-etch and remove an object to be etched exposed from the mask pattern. (1) an etching step, and irradiating the ions at a second incident angle larger than the first incident angle to perform sputter etching, and removing an etching product adhered to a side wall of the mask pattern in the first etching step. And a second etching step for removing. 2. The object to be etched is a Pt film, Ir
Film, Ru film, IrO ₂ film, or single layer film of RuO ₂ film,
2. The etching method according to claim 1, wherein the etching method is a multilayer film composed of two or more of these. Forming a first conductive film capable of reactive etching on the insulating film, forming a second conductive film thereon; and forming a mask pattern on the second conductive film. A first etching step of irradiating substantially straight ions at a first incident angle to sputter-etch and remove a second conductive film exposed from the mask pattern; and forming the first incident angle. A second etching step of irradiating the ions at a second incident angle larger than the second angle to perform sputter etching, and removing an etching product attached to a side wall of the mask pattern in the first etching step; Etching and removing the first conductive film. 4. The first conductive film is a single-layer film of a Ti film or a TiN film or a multilayer film containing at least one of them.
The conductive film, Pt film, Ir film, Ru film, IrO ₂ film, or etching according to claim 3, characterized in that RuO ₂ film of a single layer film or a multilayer film composed of two or more thereof Method. 5. After forming a first electrode made of the first conductive film and the second conductive film by the etching method according to claim 3, a capacitor insulating film is formed on the second conductive film. Forming a third conductive film and a fourth conductive film on the insulating film, and forming a second electrode. 6. The first and fourth conductive films are made of Ti film, T film,
a single-layer film of iN film or a multilayer film containing one or more of them;
The second and third conductive films are a Pt film, an Ir film, a Ru film,
The method of manufacturing a semiconductor device according to claim 5, wherein the IrO ₂ film, or RuO ₂ film of a single layer film, or a these multilayer films. 7. The insulating film includes a strontium titanate film (SrTiO ₃ film), a strontium barium titanate film (Ba _x Sr _{1 -x} TiO ₃ film), and a lead zirconate titanate film (PbZr _{1 -x} Ti _x). The method according to claim 5, wherein the semiconductor device is an O ₃ film or a strontium bismuth tantalate film (SrBi ₂ Ta ₂ O ₉ film).