JP2003007981A - Contact hole formation method - Google Patents

Abstract

(57) [PROBLEMS] To prevent reduction deterioration of an element when forming a contact hole in an insulating film in a semiconductor manufacturing process. SOLUTION: In the first half of the contact hole forming step, F
Or forming a contact hole by chemically plasma-etching the insulating film using a gas containing Cl;
In the latter half of the contact hole forming step, the insulating film is subjected to ion sputter etching using an inert gas. In the latter half of the contact hole forming step, the insulating film is subjected to ion sputter etching using an oxidizing gas. In the first half of the resist removing step, the resist is ashed using an oxidizing gas, and in the second half of the resist removing step, the resist is ion-sputtered using an inert gas. In the latter half of the resist removing step, the resist is subjected to ion sputter etching using an oxidizing gas.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for forming contact holes in a semiconductor manufacturing process.

[0002]

2. Description of the Related Art At present, a ferroelectric memory has been attracting attention as a semiconductor element using a ferroelectric material and has been put into practical use. This ferroelectric memory is made of PZ which is a ferroelectric material.
T: Pb (Zr, Ti) O ₃ or SBT: SrBi ₂ Ta
_A ferroelectric capacitor having a structure in which a film of a metal oxide such as ₂ O ₉ is sandwiched between Pt electrodes and Ir electrodes is used as an LSI (Large Scal).
e Integration) It is built into a memory, and by utilizing the remanent polarization characteristics of this ferroelectric capacitor, it can be operated as a non-volatile memory that can retain information even when the power supply is cut off. is there.

FIG. 6 shows a method of forming a contact hole in an insulating film covering a ferroelectric capacitor in the manufacturing process of such a ferroelectric memory.

As shown in FIG. 6A, a plurality of ferroelectric capacitors 2 are formed on a substrate (Si wafer) 1 by a sputter deposition method or the like. This ferroelectric capacitor 2 has a structure in which PZT 3 is sandwiched between Pt electrodes 4a and 4b. Then, these ferroelectric capacitors 2 are formed by a plasma film forming method using a plasma CVD apparatus.
To cover the SiO _x (SiO ₂
And the like), and a photoresist 7 as a mask is provided so as to cover the SiO _x film 5. The resist 6 is provided with holes 6 a for etching the SiO _x film 5 to form contact holes at positions corresponding to the respective ferroelectric capacitors 2.

Then, as shown in FIGS. 6B and 6C, contact holes are formed and the resist is removed from the substrate 1 in such a state.

In the etching step (contact hole forming step) shown in FIG. 6B, a gas containing F or Cl such as CF ₄ or CCl ₄ is used as a chemical plasma etching gas, and this gas is brought into a plasma state. By chemically plasma-etching the SiO _x film 5 with F ions or Cl ions, Pt of each ferroelectric capacitor 2 is increased.
A contact hole 5a leading to the electrode 4a is formed.
Through these contact holes 5a, the Pt electrode 4a of each ferroelectric capacitor 2 and the electrode formed on the SiO _x film 5 later are electrically connected.

After the contact hole 5a is formed, the ashing step (resist removing step) shown in FIG. 6C is next performed.
In step 3, an oxidizing gas (O ₂ or the like) is used as an ashing gas, the oxidizing gas is brought into a plasma state, and the resist 6 is removed by ashing with oxygen plasma.

[0008]

However, in the above-mentioned conventional contact hole forming method, the ferroelectric capacitor 2 is used.
The reduction deterioration of is a problem. That is, due to F ions dissociated from the etching gas in the contact hole forming process, hydrogen gas (which is considered to be a component of the resist) generated when the resist 6 is ashed with oxygen plasma in the resist removing process, etc. The PZT film (metal oxide film) 3 of the capacitor 2 is reduced and deteriorated.

Therefore, in view of the above circumstances, it is an object of the present invention to provide a contact hole forming method capable of preventing reduction degradation of an element when forming a contact hole in an insulating film in a semiconductor manufacturing process. .

[0010]

According to the present invention, the metal oxide type ferroelectric material has a property of causing deterioration due to reduction, while it does not deteriorate against physical plasma etching such as ion sputter etching. It was made based on the finding that it has a strong resistance that is difficult and has the following characteristics.

That is, a contact hole forming method of the first invention for solving the above problems is a contact hole forming method in a semiconductor manufacturing process, and an insulating film formed so as to cover an element which may be deteriorated by reduction is formed. In the contact hole forming step of forming a contact hole in the insulating film that leads to the element by etching, the first half of the contact hole forming step uses a gas containing F or Cl as a chemical plasma etching gas. In a plasma state, the insulating film is chemically plasma-etched to form the contact hole, and in the latter half of the contact hole forming step,
It is characterized in that an inert gas is used as the ion sputter etching gas, the inert gas is brought into a plasma state, and the insulating film is ion sputter etched.

The method of forming a contact hole according to a second aspect of the present invention is the method of forming a contact hole according to the first aspect of the present invention.
In the latter half of the contact hole forming step, an oxidizing gas is also used as an ion sputter etching gas, and the insulating film is ion sputter-etched in a plasma state.

A contact hole forming method of the third invention is a contact hole forming method in a semiconductor manufacturing process, wherein an insulating film formed so as to cover an element which may be deteriorated by reduction is etched, After forming a contact hole leading to the element in this insulating film, in the resist removing step of removing the resist provided so as to cover the insulating film for forming the contact hole, in the first half of the resist removing step,
An oxidizing gas is used as an ashing gas, the oxidizing gas is put into a plasma state, and the resist is ashed. In the latter half of the resist removing step, an inert gas is used as an ion sputter etching gas, and the inert gas is put into a plasma state. The resist is subjected to ion sputter etching.

The contact hole forming method of the fourth invention is the same as the contact hole forming method of the third invention,
The latter half of the resist removing step is characterized in that an oxidizing gas is also used as an ion sputter etching gas, and the resist is ion sputter-etched in a plasma state.

The contact hole forming method of the fifth invention is the contact hole forming method of the first, second, third or fourth invention, wherein Ar, He or N is used as an inert gas for performing ion sputter etching. ₂ is used as an oxidizing gas for performing ion sputter etching.
₂ or N ₂ O is used.

The contact hole forming method of the sixth invention is the contact hole forming method of the first, second, third, fourth or fifth invention, wherein the element is a metal oxide-based ferroelectric material or a high dielectric material. It is characterized by using a dielectric material.

[0017]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a block diagram of an apparatus for realizing a contact hole forming method according to an embodiment of the present invention, and FIGS. 2, 3, 4 and 5 are explanatory views of the contact hole forming method.

As shown in FIG. 1, a cylindrical vacuum chamber container 22 made of aluminum is provided on a base portion 21. A circular ceiling plate 24, which is an electromagnetic wave transmitting window, is provided above the container 22, and a substrate support 25 is provided inside the container 22.
Is provided. The substrate support base 25 has a disk-shaped substrate mounting portion (electrostatic chuck) 27 that electrostatically attracts and holds the substrate 26 of the semiconductor element, and the substrate mounting portion 27 supports the support shaft 2.
It is supported by 8.

The substrate 26 is a disk-shaped Si wafer, and as is well known, it has a diameter of 150 mm (6 inches) or a diameter of 200 mm.
There are various sizes such as mm (8 inches). A bias power supply 30 is connected to the substrate mounting portion 27 via a matching device 28 and a capacitor 29 for performing impedance matching. That is, the substrate platform 27 also functions as a bias electrode. An electrostatic power source 31 is also connected to the substrate platform 27 via the LPF 37. A high-frequency voltage is supplied from the bias power supply 30, so that a bias is applied to the substrate platform 27 (substrate 26). DC power is supplied from the electrostatic power source 31,
As a result, the substrate 26 is attracted to the substrate platform 27 by the electrostatic force generated in the substrate platform 27. Further, the substrate support base 25 can be raised or lowered as a whole or the support shaft 28 can be expanded and contracted, so that the vertical height of the substrate 26 can be adjusted to an optimum height.

Further, the base 21 is provided with an exhaust port 32, and the gas in the container 22 is exhausted to a vacuum exhaust system (not shown) through the exhaust port 32, whereby the container 22 is discharged.
Inside is a low-pressure environment, and various gases (chemical plasma etching gas, ashing gas, ion sputter etching gas) for forming a contact hole are supplied under this low-pressure environment (details will be described later). The container 22 is provided with a loading / unloading port (not shown) for the substrate 26 so that the substrate 26 can be loaded and unloaded from / to a transfer chamber (not shown).

On the other hand, a spiral feeding antenna 33 is installed on the ceiling plate 24, and a high frequency power source 35 is connected to the feeding antenna 33 via a matching device 34 for impedance matching. . Therefore, by applying high-frequency power from the high-frequency power source 35 to the power feeding antenna 33, the electromagnetic wave 36 is made incident from the power feeding antenna 33 into the container 22 via the ceiling plate 24. By the energy (high frequency power) of this electromagnetic wave 36,
Various gases supplied into the container 22 are brought into a plasma state.

The container 22 is provided with a gas supply (not shown).
Supply various gases sent from the supply system into the container 22
Nozzles 41, 42, and 43 are provided for this purpose.
O from the nozzle 41 as an oxidizing gas₂Is supplied. This
The amount of oxidizing gas supplied is MFC (Mass Flow Controller)
Adjusted by 44. The oxidizing gas is N ₂
O may be used. From the nozzle 42, an inert gas (io
Ar is supplied as a sputtering gas).
The amount of this inert gas supplied is adjusted by the MFC 45.
It An inert gas (ion sputter etching gas
He) or N₂May be used. Nozzle 43
CF as a chemical plasma etching gas_FourSupplied by
To be done. The supply amount of this chemical plasma etching gas is
Adjusted by MFC 46. Note that chemical plasma
CCl as etching gas_FourOther F and Cl
You may use the gas containing.

The controller 38 having a microcomputer, which will be described in detail later, is based on a predetermined control sequence according to the procedure for forming contact holes, and the M
By controlling ON / OFF of the FCs 44, 45, 46, the supply timing of various gases is controlled. Also,
The controller 38 also controls the power supply timing of the high frequency power supply 35, the bias power supply 30, and the electrostatic power supply 31.

Here, a method of forming a contact hole carried out by the above apparatus will be described in detail with reference to FIGS. It should be noted that these figures show a method of forming a contact hole in an insulating film in a manufacturing process of a ferroelectric memory.

As shown in FIG. 2A, a plurality of ferroelectric capacitors 51 are formed on the substrate 23 by the sputter deposition method or the like. This ferroelectric capacitor 51
Is the metal oxide film PZT52 and Pt electrodes 53a, 53
It has a structure sandwiched between b. And plasma CVD
These ferroelectric capacitors 51 are covered with an S film as an insulating film by a plasma film forming method using an apparatus.
An iO _x (SiO ₂ etc.) film 54 is formed, and the S
A photoresist 55 as a mask is provided so as to cover the iO _x film 54. This resist 55 has S
Holes 55a for forming contact holes by etching the iO _x film 54 are provided at positions corresponding to the respective ferroelectric capacitors 51.

Then, the substrate 26 in such a state is carried into the container 22, placed on the substrate placing portion 27 and adsorbed by the electrostatic force, and then, as shown in FIG. 2 (b), FIG. 2 (c), and FIG. 3 (a),
As shown in FIG. 3B, contact holes are formed and the resist is removed.

In the first half of the etching step (contact hole forming step) shown in FIG. 2B, a gas containing F or Cl such as CF ₄ or CCl ₄ is used as the chemical plasma etching gas, and this gas is stored in the container 22. To the plasma state by the high frequency power from the high frequency power supply 35,
The SiO _x film 5 is chemically plasma-etched with F ions or Cl ions. Therefore, the SiO _x film 54
Then, a contact hole 54a is formed. In the first half of this contact hole forming step, the contact hole 54a
Is not completely formed until it reaches the ferroelectric capacitor 52 (Pt electrode 53a), but is formed halfway. That is, the SiO _x film 54 is etched up to just before the ferroelectric capacitor 51 (Pt electrode 53a).

The state at this time is enlarged and shown in FIG. As shown in FIG. 4A, at this time, an oxidizing gas (O ₂ ) is also supplied into the container 22 to be in a plasma state, and an oxygen atmosphere is provided to suppress reduction deterioration of the ferroelectric capacitor 52. .

In the latter half of the etching step (contact hole forming step) shown in FIG. 2C, an inert gas (Ar, He or N ₂ ) is used for ion sputter etching without using a gas containing F or Cl. The contact hole 54a is formed by supplying this inert gas into the container 22, making it into a plasma state by the high frequency power from the high frequency power source 35, and ion sputter etching the SiO _x film 54 with the inert gas ions. . That is, in the latter half of this contact hole forming step, the contact hole 54a is formed until it reaches the Pt electrode 53a of the ferroelectric capacitor 52. Thus, the contact holes 54a leading to the ferroelectric capacitor 52 (Pt electrode 53a) are completed, and these contact holes 54a are formed.
Through the Pt electrode 53a of each ferroelectric capacitor 51
Then, the electrode formed on the SiO _x film 54 later is electrically connected.

The state at this time is enlarged and shown in FIG. As described above, in the latter half of the contact hole forming step, the SiO _x film 54 is ion-sputter-etched with the inert gas ions to form the contact hole 54a, which is strengthened by F ions dissociated from the etching gas as in the conventional case. Dielectric capacitor 51 (PZT film 5
It is possible to prevent the reduction deterioration of 2). That is, the contact hole 54a can be formed without reducing and deteriorating the ferroelectric capacitor 51.

Further, in the latter half of this contact hole forming step, as shown in FIG. 4C, an oxidizing gas (O ₂ or N ₂ O) is also used as an ion sputter etching gas,
The oxidizing gas may be supplied into the container 22 to be in a plasma state by the high frequency power from the high frequency power source 35, and the SiO _x film 54 may be ion sputter etched by O ₂ ions. In this case, by performing ion sputter etching with O ₂ ions, the reduction deterioration of the ferroelectric capacitor 52 can be prevented, and the effect of reducing the reduction reaction of the ferroelectric capacitor 52 in an oxygen atmosphere can be obtained.

In the above contact hole forming step, the substrate mounting portion 27 (the substrate 2) is driven by the bias power source 30.
By applying a bias to 6), ions such as F ions and inert gas ions have directivity, and these ions are drawn into the contact holes 54a, so that the SiO _x film 54 is efficiently etched. To form a contact hole 54a.

When the contact hole 54a is formed,
Next, in the first half (ashing step) of the resist removing step shown in FIG. 3A, an oxidizing gas (O 2) is used as an ashing gas.
₂ or N ₂ O), the oxidizing gas is supplied into the container 22 to be in a plasma state by the high frequency power from the high frequency power source 35, and the resist 6 is removed by ashing with oxygen plasma. In the first half of this resist removal process,
The resist 55 is not completely removed, but is removed halfway. That is, the resist 55 is formed just before the SiO _x film 54.
To remove.

The state at this time is enlarged and shown in FIG. In FIG. 5A, the resist 55 before the removal is started
The state is shown by the one-dot chain line, and the state of the resist 55 partially removed is shown by the solid line.

Then, in the latter half of the resist removing step shown in FIG. 3B, an inert gas (Ar, He or N ₂ ) is used for the ion sputter etching, and this inert gas is supplied into the container 22 for high frequency. A high-frequency power from the power source 35 is used to bring the plasma state, and the resist 55 is removed by ion sputter etching with inert gas ions. That is, the resist 55 is completely removed in the latter half of this resist removing step.

The state at this time is enlarged and shown in FIG. As described above, by removing the resist 55 by ion sputter etching with the inert gas ions in the latter half of the resist removing step, the ferroelectric capacitor is removed by hydrogen gas generated when the resist is ashed by oxygen gas plasma as in the conventional case. It is possible to prevent the reduction deterioration of 51 (PZT film 52). That is, the resist 55 can be removed without reducing and deteriorating the ferroelectric capacitor 51.

In the latter half of this resist removing step,
As shown in FIG. 5C, an appropriate amount of oxidizing gas (O ₂ or N ₂ O) is also used as an ion sputter etching gas, and this oxidizing gas is supplied into the container 22 to supply the high frequency power source 3
O ₂ from the plasma state by the high frequency power from 5
The resist 55 may be removed by ion sputter etching with ions. In this case, by performing ion sputter etching with O ₂ ions, the reduction deterioration of the ferroelectric capacitor 52 can be prevented, and the effect of reducing the reduction reaction of the ferroelectric capacitor 52 in an oxygen atmosphere can be obtained. At this time, if the amount of the oxidizing gas with respect to the inert gas is too large, the oxygen plasma ashes the resist 55, and hydrogen gas or the like is generated, which may cause reduction and deterioration of the ferroelectric capacitor 21. In consideration of this, it is necessary to appropriately adjust the supply amount of oxidizing gas at this time.

In the above description, an element using a metal oxide-based ferroelectric material has been described as an example. However, the present invention is not limited to this, and the present invention is applied to an element which may cause reduction deterioration. Can be widely applied. For example, the present invention can be applied also when forming a contact hole in an insulating film in a manufacturing process of a semiconductor element using a metal oxide-based high dielectric material or the like.

[0040]

As described above in detail with the embodiments of the invention, the contact hole forming method of the first invention is a contact hole forming method in a semiconductor manufacturing process, and is an element which may be deteriorated by reduction. By etching the insulating film formed so as to cover the contact hole in the step of forming a contact hole leading to the element in the insulating film, the first half of the contact hole forming step uses a chemical plasma etching gas. A gas containing F or Cl is used, the gas is brought into a plasma state, and the insulating film is chemically plasma-etched to form the contact hole,
The latter half of the contact hole forming step is characterized in that an inert gas is used as an ion sputter etching gas, the inert gas is brought into a plasma state, and the insulating film is ion sputter etched.

Therefore, according to the contact hole forming method of the first aspect of the present invention, the contact holes are formed by ion sputter etching with the inert gas ions in the latter half of the contact hole forming step to form the contact holes as in the conventional case. It is possible to prevent the element from being reduced and deteriorated due to F ions dissociated from the inside. That is, the contact hole can be formed without reducing and deteriorating the element.

The contact hole forming method of the second invention is the same as the contact hole forming method of the first invention,
In the latter half of the contact hole forming step, an oxidizing gas is also used as an ion sputter etching gas, and the insulating film is ion sputter-etched in a plasma state.

Therefore, according to the contact hole forming method of the second aspect of the present invention, since the oxidizing gas is also used as the ion sputter etching gas, the reduction deterioration of the element is prevented by performing the ion sputter etching with O ₂ ions, and at the same time, oxygen is eliminated. The effect of suppressing the reduction reaction of the device by setting the atmosphere is also obtained.

The contact hole forming method of the third invention is a method of forming a contact hole in a semiconductor manufacturing process, in which an insulating film formed so as to cover an element which may be deteriorated by reduction is etched, After forming a contact hole leading to the element in this insulating film, in the resist removing step of removing the resist provided so as to cover the insulating film for forming the contact hole, in the first half of the resist removing step,
An oxidizing gas is used as an ashing gas, the oxidizing gas is put into a plasma state, and the resist is ashed. In the latter half of the resist removing step, an inert gas is used as an ion sputter etching gas, and the inert gas is put into a plasma state. The resist is subjected to ion sputter etching.

Therefore, according to the contact hole forming method of the third aspect of the present invention, the resist is removed by ion sputter etching with the inert gas ions in the latter half of the resist removing step to remove the resist from oxygen gas plasma as in the conventional case. It is possible to prevent the element from being reduced and deteriorated due to hydrogen gas or the like generated during the ashing. That is, the resist can be removed without reducing and deteriorating the element.

The contact hole forming method of the fourth invention is the same as the contact hole forming method of the third invention.
The latter half of the resist removing step is characterized in that an oxidizing gas is also used as an ion sputter etching gas, and the resist is ion sputter-etched in a plasma state.

Therefore, according to the contact hole forming method of the fourth aspect of the present invention, since the oxidizing gas is also used as the ion sputter etching gas, the reduction deterioration of the element is prevented by performing the ion sputter etching with O ₂ ions, and at the same time, the oxygen is eliminated. The effect of suppressing the reduction reaction of the device by setting the atmosphere is also obtained.

The contact hole forming method of the fifth invention is the contact hole forming method of the first, second, third or fourth invention, wherein Ar, He or N is used as an inert gas for performing ion sputter etching. ₂ is used as an oxidizing gas for performing ion sputter etching.
₂ or N ₂ O is used.

Therefore, according to the contact hole forming method of the fifth invention, the contact hole is formed without reducing and deteriorating the element as in the contact hole forming method of the first, second, third or fourth invention. In addition, the resist can be removed.

The contact hole forming method of the sixth invention is the contact hole forming method of the first, second, third, fourth or fifth invention, wherein the element is a metal oxide-based ferroelectric material or a high dielectric material. It is characterized by using a dielectric material.

Therefore, according to the contact hole forming method of the sixth aspect of the present invention, as in the contact hole forming method of the first, second, third, fourth or fifth aspect, the metal oxide type ferroelectric material or The contact hole can be formed and the resist can be removed without reducing and deteriorating the high dielectric material.

[Brief description of drawings]

FIG. 1 is a configuration diagram of an apparatus that realizes a contact hole forming method according to an embodiment of the present invention.

FIG. 2 is an explanatory diagram of a method of forming the contact hole.

FIG. 3 is an explanatory diagram of a method of forming the contact hole.

FIG. 4 is an explanatory diagram of a method of forming the contact hole.

FIG. 5 is an explanatory diagram of a method for forming the contact hole.

FIG. 6 is an explanatory diagram of a conventional contact hole forming method.

[Explanation of symbols]

21 Base 22 Container 24 Ceiling Plate 25 Substrate Support 26 Substrate 27 Substrate Placement 28 Support Shaft 29 Capacitor 30 Bias Power Source 31 Electrostatic Power Source 32 Exhaust Port 33 Feed Antenna 34 Matching Device 35 High Frequency Power Source 36 Electromagnetic Wave 37 LPF 38 Controller 41, 42, 43 nozzles 44, 45, 46 MFC 51 ferroelectric capacitor 52 PZT film 53a, 53b Pt electrode 54 SiO _x film 54a contact holes 55 resist 55a hole

Front page continuation (51) Int.Cl. ⁷ Identification code FI theme code (reference) H01L 21/30 572A F term (reference) 2H096 AA25 HA23 HA24 JA04 LA07 LA08 5F004 AA16 BA09 BA20 BB13 BB22 CA09 DA00 DA01 DA05 DA22 DA23 DA25 DA26 DB03 DB13 DB26 EB01 5F033 KK31 QQ09 QQ12 QQ14 QQ15 QQ21 QQ37 RR04 VV10 VV16 XX00 5F046 MA12 MA13 5F083 GA27 GA30 JA15 JA38 JA56 PR03 PR04 PR21 PR22

Claims (6)

[Claims] 1. A method of forming a contact hole in a semiconductor manufacturing process, comprising etching an insulating film formed so as to cover an element which may be deteriorated by reduction, thereby forming a contact through the insulating film to the element. In the step of forming a contact hole for forming a hole, in the first half of the step of forming the contact hole, a gas containing F or Cl is used as a chemical plasma etching gas, and this gas is brought into a plasma state to chemically plasma-etch the insulating film. Thus, the contact hole is formed, and in the latter half of the step of forming the contact hole, an inert gas is used as an ion sputter etching gas, the inert gas is brought into a plasma state, and the insulating film is ion sputter etched. And a method of forming a contact hole. 2. The method of forming a contact hole according to claim 1, wherein in the latter half of the contact hole forming step, an oxidizing gas is also used as an ion sputter etching gas, and the oxidizing gas is brought into a plasma state to ion-sputter the insulating film. A method for forming a contact hole, which comprises etching. 3. A method of forming a contact hole in a semiconductor manufacturing process, wherein an insulating film formed so as to cover an element which may be deteriorated by reduction is etched to form a contact that leads to the element. After forming the hole, in the resist removing step of removing the resist provided so as to cover the insulating film for forming the contact hole, in the first half of the resist removing step, the oxidizing gas is used as the ashing gas. In the latter half of the resist removing step, an inert gas is used as an ion sputter etching gas, and the inert gas is put in a plasma state to ion sputter etch the resist. Characteristic contact hole forming method. 4. The contact hole forming method according to claim 3, wherein in the latter half of the resist removing step, an oxidizing gas is also used as an ion sputter etching gas, and the oxidizing gas is brought into a plasma state to ion sputter-etch the resist. A method of forming a contact hole, comprising: 5. The method for forming a contact hole according to claim 1, 2, 3 or 4, wherein Ar, He or N ₂ is used as an inert gas for performing ion sputter etching, and ion sputter etching is performed. A method of forming a contact hole, characterized in that O ₂ or N ₂ O is used as an oxidizing gas. 6. The method of forming a contact hole according to claim 1, 2, 3, 4 or 5, wherein the element is made of a metal oxide type ferroelectric material or a high dielectric material. And a method of forming a contact hole.