JP2003264171A - Method for etching difficult-to-etch material and method and apparatus for manufacturing semiconductor using the same - Google Patents

Abstract

(57) [Problem] To improve the etching shape by preventing a deposit generated during etching of an etching material from adhering to a mask. SOLUTION: When etching the film using plasma using a film of a difficult-to-etch material formed on a substrate and a mask formed thereon, an angle of a side wall of the mask with respect to a surface of the substrate is increased. Etching is performed using a mask of less than 90 degrees, whereby the taper angle of the film after etching with respect to the surface of the substrate is equal to or larger than the taper angle of the mask.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to Pt, Ru, Ir and PZ.
A method for etching a difficult-to-etch material such as T or HfO2, a semiconductor integrated circuit device including the hard-to-etch material, and a method for manufacturing the same,
In particular, the present invention relates to a technique effective for etching the side wall of a difficult-to-etch material in a shape close to vertical.

[0002]

2. Description of the Related Art Conventionally, as a means for treating the surface of a semiconductor element, a method of etching using a photoresist having a tapered shape or a rounded head is known.

A method of etching using a tapered mask is described in US Pat. No. 5,818,107 (JP-A-10-2).
14826) and JP-A-10-223855. In addition, a method of etching using a round photoresist is described in USP6057081 (JP-A-10).
-98162).

However, etching of a non-volatile material, which is a material that is difficult to etch (hereinafter, simply referred to as a difficult-to-etch material), is performed at a high temperature of 300 ° C. or higher, and the photoresist cannot be used in some cases.

[0005]

By the way, with the miniaturization of semiconductor elements and the speeding up of operation, MOS (metal-oxide-s)
Alumina, zirconium oxide, hafnium oxide, ruthenium, platinum, tantalum oxide, BST, SBT, PZ for the gate insulating film of the transistor, the gate electrode, or the capacitor of the memory part, and the capacitor electrode.
The use of materials such as T has been considered. In addition, magnetic memory (MRAM; magnetic random acces)
s memory) etc., iron, nickel, cobalt, manganese or its alloys are used.

Examples of difficult-to-etch materials include the following. Magnetic material: (Use: magnetic disk, MRAM, etc.) Fe, Co, M
Noble metals such as n and Ni: (Use: Various electrodes) Pt, Ru, RuO2, Ta, Ir, IrO2, Os, Pd, Au, Ti, TiOx,
High dielectric materials such as SrRuO3, (La, Sr) CoO3, Cu: (Application: DRAM capacitor (charge storage)
Etc.) BST: (Ba, Sr) TiO3, SRO: SrTiO3, BTO: BaTiO3, SrTa2
O6, Sr2Ta2O7, ZnO, Al2O3, ZrO2, HfO2, Ta2O5 etc. Ferroelectrics: (Use: FeRAM capacitors etc.) PZT: Pb (Zr, Ti) O3, PZTN: Pb (Zr, Ti) Nb2O8, PLZT: (P
b, La) (Zr, Ti) O3, PTN: PbTiNbOx, SBT: SrBi2Ta2O9, SBTN: SrBi2 (Ta, N
b) 2O9, BTO: Bi4Ti3O12, BiSiO _x, BLOT: Bi _4-x La _x Ti ₃ O ₁₂ etc.Compound semiconductor: GaAs etc. ITO other: InTiO etc.

These difficult-to-etch materials are more difficult to etch than aluminum, silicon, silicon oxide, etc., and it is particularly difficult to process the side walls of the difficult-to-etch materials into a shape perpendicular to the substrate. Has become.

[0008] None of the above-mentioned known documents suggests processing the side wall of the difficult-to-etch material into a shape perpendicular to the substrate.

Next, when a chemically stable material such as iron, cobalt, manganese, nickel, platinum, ruthenium, tantalum, alumina, hafnium oxide, zirconium oxide, or gallium arsenide is etched using plasma, the material to be etched becomes The reason why it is difficult to obtain a vertical etching shape will be described below.

In the case of a material that is difficult to be etched, such as the above-mentioned difficult-to-etch material, a reaction product is generated by etching, and the reaction product jumps out from the surface of the sample to the gas phase and then reaches the wall of the material to be etched. It has a property of easily adhering to. Therefore, if the reaction product adheres only to the position where etching progresses in the material to be etched, the etching rate will only substantially decrease, but in reality, the reaction product will be present at all positions in the material to be etched. Adhere to. That is, in the material to be etched, the reaction products adhere to the side wall where etching hardly progresses, and as a result, the etching of the bottom surface where the etching proceeds and the deposition of the deposition material on the side wall proceed at the same time. A shape perpendicular to the substrate cannot be obtained on the side wall of the etching material. The above is the reason why the etching shape in which the side wall of the material to be etched is perpendicular to the substrate surface cannot be obtained in the etching of the difficult-to-etch material.

The reason why the etching shape perpendicular to the substrate cannot be obtained on the side wall of the material to be etched is shown in FIGS. 1A to 2G.
Will be described in more detail with reference to.

1A and 2A show the initial state of etching, in which the arrow pointing to the right indicates the deposition direction of deposits, and the arrow pointing below indicates the etching direction. Here, the angle (taper angle) θ of the side wall of the mask 10 with respect to the upper surface of the substrate is 90 degrees. When a minute unit time Δt elapses from the initial state, the bottom surface (the upper surface 2 of the etching target material 20 exposed to the plasma 2
1) is etched by Δe, and deposits 25 are deposited on the sidewalls of the mask 10 and the material to be etched 20 by Δd (FIGS. 1B and 2B). By the way, since the upper surface portion 30 of the deposited material is actually etched, the angle (taper angle) φ formed by the portion with respect to the substrate surface is the same as the deposited amount (deposition rate) Δd of the deposited material per unit time. It is determined by the etching amount (etching rate) Δe per time.

Further, in the portion 32 immediately below the side wall of the mask, at the moment when the deposit 25 is deposited on the side wall of the mask, the bottom surface portion 33 (the portion to be etched exposed to the plasma) below the deposit on the side wall of the mask is started. The etching of the upper surface 21) of the material 20 is stopped. However, at the moment when the exposed portion of the material to be etched 20 is etched below the side wall of the deposited material 25 on the side wall of the mask and a new sidewall of the material to be etched 20 is exposed, the deposited material is deposited on the exposed surface. . Therefore, the etching proceeds obliquely downward (see FIG. 1).
C, 2C).

Next, when a unit time Δt elapses from the state shown in FIGS. 1C and 2C, the deposit 2 is further deposited on the side wall of the deposit 25.
As the deposition of No. 5 progresses, the etching also progresses at the exposed portion of the material to be etched 20 in the lower portion of the sidewall of the deposit 25 (FIGS. 1D, 1E, 2D to 2F). Thus
Etching progresses obliquely downward, and the etching shapes shown in FIGS. 1F and 2G are obtained. Thus, the side wall of the material to be etched has a taper angle φ (φ <9
0 degree) will be formed.

It is an object of the present invention to provide an etching method for a difficult-to-etch material and a semiconductor manufacturing method and apparatus using the same, which can solve the above-mentioned problems of the prior art.

Another object of the present invention is to provide a stable process for a plurality of wafers or to make the taper angle of the material to be etched close to vertical in order to meet the demand for miniaturization of semiconductor elements and the like. A method and an apparatus for surface treatment of a sample.

[0017]

A feature of the present invention resides in a surface treatment method of a sample in which a tape mask is used for etching a film formed on a substrate using plasma.

That is, according to one aspect of the present invention, a method of etching the film using plasma using a film of a difficult-to-etch material formed on a substrate and a mask formed thereon is a method of etching the mask. Etching using a mask whose sidewalls form an angle of less than 90 degrees with respect to the surface of the substrate.

Therefore, according to the present invention, in the etching of a material in which it is difficult to obtain a processed shape in which the side wall is vertical, by using a tapered mask or the like, an etched shape in which the side wall is nearly vertical can be obtained, so that a highly functional semiconductor is obtained. device,
Alternatively, a highly integrated semiconductor device can be created.

[0020]

DETAILED DESCRIPTION OF THE INVENTION Embodiments of the present invention will be described below in detail with reference to the accompanying drawings.

FIG. 3 is a diagram showing an example of the overall structure of a plasma etching apparatus to which the present invention is applied. High frequency power supply 101
From the automatic matching unit 102 (automatic matching unit) to supply high-frequency current to the coil 103,
Plasma 105 is generated in 04. Vacuum container 104
Comprises a discharge part 104a made of an insulating material and a processing part 104b grounded. An etching gas such as chlorine is introduced into the vacuum container 104 through the gas introduction unit 106, and the gas is exhausted by the exhaust device 107.

The sample 108 is placed on the sample table 109. In order to increase the energy of the ions incident on the sample 108, a bias power source 110, which is a second high frequency power source, is connected to the sample stage 109 via a high pass filter 111. An insulating film 112 made of ceramic or the like is provided on the surface of the sample table 109. Also, the sample table 1
A DC power supply 113 is connected to the sample base 09 via a low-pass filter 114, and holds the sample 108 on the sample base 109 by electrostatic force.

Further, in order to control the processing by adjusting the temperature of the sample 108, the sample stage 109 is provided with a heater 115 and a coolant channel 116.

Typical conditions for etching chemically stable materials such as iron, cobalt, manganese, nickel, platinum, ruthenium, tantalum, alumina, hafnium oxide, zirconium oxide and gallium arsenide using this apparatus. Is as follows. The device pressure is 0.5P
a. The gas to be introduced is mainly chlorine. Although the temperature of the sample 108 varies depending on the material to be etched,
It is 200 ° C. or higher and 500 ° C. or lower. This depends on the required etching rate or the semiconductor device to be manufactured, but a typical temperature for etching a silicon film, an aluminum film or a silicon oxide film is 0 ° C.
The temperature of the sample 108 is maintained at a high temperature as compared with the case of 1 to 100 ° C. Therefore, a photoresist is often not effectively used as an etching mask material, and a silicon oxide or metal hard mask is often used.

In order to carry out the above-mentioned problem in etching the difficult-to-etch material, that is, to perform the etching processing in which the taper angle φ of the material to be etched can be made close to the angle perpendicular to the surface of the substrate, the deposit attached to the sidewall of the mask It is important to keep the amount of.

As a method of suppressing the deposition of the deposits, it is conceivable to lower the pressure in the reaction vessel and increase the flow rate of the gas introduced into the reaction vessel. But,
The pressure and the flow rate of the gas are often limited to an appropriate range in order to obtain the desired etching characteristics, and the limits of the pressure and the flow rate are determined by the exhaust capacity. Therefore, the pressure,
It is difficult to suppress the deposition of deposits by the flow rate.

Next, a mask having a taper angle (an angle of the side wall of the mask 10 with respect to the upper surface of the substrate) θ of less than 90 degrees (that is, a tapered mask) is used. The reason why the processed shape in which the angle (φ) of the side wall with respect to the substrate surface is close to vertical is obtained will be described with reference to FIGS. In addition,
5A shows the case where the mask taper angle θ is 90 degrees, and the deposit 25 is deposited in parallel on the side wall of the mask 10 as described with reference to FIGS. Further, FIG. 4A shows a state before etching when the taper angle θ of the mask is 90 degrees.

First, when the process conditions are determined, the bottom surface of the sample (the surface 21 of the material to be etched exposed to plasma)
Etching rate is determined. When etching is performed using chlorine as the main etching gas, chloride (reaction product) of the material to be etched in the sample jumps out of the substrate (material) into the etching device (reaction vessel). The reaction products jumping out into the etching apparatus are again incident on the substrate, and some of the reaction products incident on the substrate are deposited as deposits on the substrate surface (side wall of the mask and side wall of the material to be etched) (FIG. 4B). . In many cases, this depot object can be approximated as isotropic. The deposition rate of the deposited material (hereinafter, simply referred to as the deposition rate) is rd. on the other hand,
Since the etching mainly depends on the action of ions, the incident direction of the ions at the etching target position has a great influence on the etching rate at that position. If the etch rate is simply determined by the ion flux, and the etch rate at the sample bottom surface where the ions are incident almost vertically is re, the etch rate when the ion incident angle is α is re
× sin α. Here, re is the true etch rate when no deposit is deposited.

That is, when the side wall of the mask is perpendicular to the surface of the substrate, the deposition rate of the deposited material on the side wall of the mask is rd, and the apparent etch rate of the sample bottom surface 21 is r.
e-rd (see FIG. 4D). At this time, the taper angle φ of the material to be etched is tan φ = (re-rd) / rd.

On the other hand, as shown in FIGS. 4B and 5B, when the side wall of the mask is slightly inclined from the direction perpendicular to the substrate surface (the taper angle θ of the mask is less than 90 degrees), the deposition rate to the side wall of the mask is small. Rd because it is isotropic,
The etching rate of the side wall of the mask is re × cos θ.
Therefore, rd−re × cos θ is the deposition rate on the side wall when the taper angle of the mask is θ. Therefore,
The taper angle φ of the material to be etched is tan φ = (re-rd) / ((rd-re × cos) as shown in FIG. 4D.
θ) × sin θ).

Under such a condition that deposition of deposits on the side wall of the mask proceeds, the smaller the taper angle θ of the mask, the smaller the taper angle φ of the material to be etched after etching.
Grows. Note that FIG. 4C shows a state in which deposits have been removed after the etching treatment as shown in FIG. 4B.

When the taper angle θ of the mask is made smaller than 90 degrees and the taper angle θ is further made smaller than that of FIG. 5B, the taper angle θ is as shown in FIG. 5C.
And the taper angle φ of the material to be etched match (θ = φ).
This state is a condition under which deposition matter does not adhere to the mask. That is, even if the deposited matter adheres to the mask, the deposited matter is instantly removed by etching, and as a result, the deposited matter does not adhere to the mask. The taper angle of the mask at this time is θ0,
Assuming that the taper angle of the material to be etched is φm, as shown in FIG. 5D, even if the taper angle θ of the mask is further reduced (that is, θ <θ0), the taper angle of the material to be etched does not become larger than φm. That is, as shown in FIG. 5D, when θ <θ0, θ <φm, and therefore, the taper angle θ0 of the mask is the maximum (φm) of the taper angle φ of the material to be etched. It becomes a value. In the state of FIG. 5D, the mask or the base (material to be etched) is exposed.

The taper angle θ of such a mask
The relationship between and the taper angle φ of the material to be etched is as shown in FIG. Here, rd / re is uniquely determined by the mask, the material of the material to be etched, and the etching conditions (pressure in the reaction container, flow rate of gas introduced into the reaction container, etc.). Generally, the higher the pressure in the reaction vessel, the rd / re
Becomes smaller, and rd / re becomes smaller as the flow rate of the gas introduced into the reaction vessel increases.

As shown in FIG. 6, for example, rd / r
When e = 0.5, the mask taper angle θ is 90
When the taper angle φ is decreased, the taper angle φ of the material to be etched increases substantially in proportion to the taper angle θ of the mask. When the taper angle θ of the mask is reduced to about 72 degrees, the taper angle φ of the material to be etched also increases to about 72 degrees (θ =
φ), the state shown in FIG. 5C is obtained. That is, θ = θ0 = φ = φm
Becomes Therefore, even if the taper angle θ of the mask is further reduced (θ <θ0), the taper angle of the material to be etched is φ.
It remains m.

Therefore, in FIG. 6, the line L indicates the limit value θ0 of the taper angle of the mask. Therefore, the region A is a region where θ> θ0, and the deposits adhere to the mask, and the taper angle φ of the material to be etched is determined by the taper angle θ of the mask. On the other hand, the region B is a region of θ ≦ θ0, in which no deposits are attached to the mask, and the taper angle φ of the material to be etched becomes a constant value φm regardless of the taper angle θ of the mask. Therefore,
For example, in the case of rd / re = 0.4, when it is desired to set the taper angle φ of the material to be etched to 70 degrees, the taper angle θ of the mask may be set to about 82 degrees.

Next, a method of forming a mask having a side wall taper angle of less than 90 degrees will be described.

Here, as an example, a case where Pt is etched using a silicon oxide hard mask will be described.

(A) First, a method of controlling the taper angle of the side wall of the silicon oxide film as a mask by the composition of the etching gas and the etching pressure will be described with reference to FIGS. 8A-8E. A hard mask material 51 such as a silicon oxide film or a metal film is formed on Pt 50, and a photoresist 52 is patterned in a predetermined pattern on the hard mask material 51 (FIG. 8A). Next, silicon oxide is etched into a tapered shape mainly using a fluorocarbon-based gas and an additive gas such as oxygen (FIG. 8B). At this time, switching the composition of the gas introduced into the etching chamber,
By changing the etching pressure, it is possible to etch the silicon oxide into a tapered shape.

Etching into such a tapered shape is performed, for example, by J. Vac. Sci. Technol. A 14, 1832 (199
It is described in 6). This document describes a method of controlling the taper angle of a silicon oxide film by the composition of etching gas and etching pressure. Specifically, using a photoresist with a taper angle of 86 °, C
F4 flow rate is 20 sccm, bias power is 100W
Under the etching conditions of 40 mTorr
To 300 mTorr changes the taper angle of the formed silicon oxide film from 80 ° to 51 °. Also, the pressure is 40 mTorr, CHF3 and CF
Under the etching condition that the total flow rate of No. 4 is 20 sccm, its composition ratio (CHF3 in CF4 (%)) is changed from 0% to 50.
%, The taper angle of the silicon oxide film is changed from 66 ° to 84 °.

As described above, while the etching rate in the lateral method of the silicon oxide film is almost independent of the pressure, the taper angle of the oxide film is controlled by utilizing the fact that the etching rate in the vertical direction decreases as the pressure increases. I know that I can do it.

When the taper angle of the silicon oxide film can be formed to less than 90 degrees (FIG. 8B), the photoresist 52 is removed (FIG. 8C). Next, this substrate is conveyed to a predetermined position in the etching apparatus and is etched (FIG. 8D).
After that, the mask 51 is removed (FIG. 8E).

As another etching method for forming a mask taper angle of less than 90 degrees, US Patent
No. 5, 856, 239.

(B) Next, a method of forming the taper angle of silicon oxide as a mask to less than 90 degrees by wet etching will be described. Such methods are described, for example, in Jp
n. J. Appl. Phys., Vol. 34 (1995), pp.2132-2136
Is disclosed in. That is, as shown in FIG. 9A, Pt5
A polysilicon film 52 having a predetermined pattern is formed on the silicon oxide film 51 as a mask for etching 0, and this is immersed in an HF aqueous solution under constant conditions. Although the polysilicon film 52 is not etched with the HF aqueous solution, the silicon oxide film 51 is isotropically etched with the HF aqueous solution to form a tapered shape as shown in FIG. 9B. Then, the polysilicon film is etched by using chlorine Cl2, fluorine F2, hydrogen hexafluoride SF6, or the like, so that finally a silicon oxide mask 51 having a shape as shown in FIG. 9C is formed. Therefore, etching is performed using such a tapered mask (FIG. 9D), and then the mask 51 is removed (FIG. 9E).

10A to 13D are views showing several methods of forming masks of silicon oxide films having the same width (size) and different taper angles.

First, in the method shown in FIGS. 10A-10I, masks having the same width (size) and different taper angles are formed by the film thickness of the silicon oxide film 51 as a mask and the wet etching time corresponding thereto. Is. For example,
As shown in FIGS. 10A, 10D, and 10G, silicon oxide films 51 having different thicknesses T1, T2, and T3 are formed, and then wet etching with HF is performed for a time corresponding to the thickness of the silicon oxide film. , 10B, 1
Masks having different taper angles can be formed as shown in 0E and 10H, respectively. Therefore, when the polysilicon film 52 is removed thereafter, as shown in FIGS. 10C, 10F, and 10I, the taper angles θ1 and θ are the same width (size), respectively.
2, a mask of θ3 (here, θ1>θ2> θ3) can be formed. That is, the larger the film thickness of the silicon oxide film 51 as the mask, the smaller the taper angle of the mask can be set.

The methods shown in FIGS. 11A to 11I form masks having the same width (size) and different taper angles by the width (size) of the polysilicon film as the mask and the wet etching time corresponding to the width. Is. For example, as shown in FIGS. 11A, 11D, and 11G, foams having different widths (sizes) W1, W2, and W3 and a polysilicon film 52 as a resist are formed in advance, and then wet etching with HF is performed to remove the polysilicon film. Width (size)
11B, 11E, 11H
Masks having different taper angles can be formed as shown in FIGS. Therefore, after that, when the polysilicon film 52 is removed, as shown in FIGS. 11C, 11F, and 11I, masks having the same width (size) and taper angles θ4, θ5, and θ6 (here, θ4>θ5> θ6) are formed. Can be formed. That is, the smaller the width (size) of the polysilicon film 52, the smaller the taper angle of the mask can be set.

12A to 13D show a method of controlling the mask taper angle by dry etching and wet etching.

In the method shown in FIGS. 12A-12C,
First, the polysilicon film 52 is patterned to have a predetermined width (size) W4 (FIG. 12A), and then a part of the silicon oxide film 51 is dry-etched to a substantially vertical thickness T.
Only h1 is shaved (FIG. 12B), and then wet etching is performed to taper the silicon oxide film 51 (FIG. 12C).

In the method shown in FIGS. 13A-13D,
First, the polysilicon film 52 is patterned into a predetermined width (size) W5 different from the width (size) W4 (see FIG. 1).
3A), and then a silicon oxide film 5 is formed by dry etching.
1 has a thickness T that is different from the above-mentioned thickness Th1 in a substantially vertical direction.
Only h2 is removed (FIG. 13B), and then wet etching is performed to taper the silicon oxide film 51 (FIG. 13C).

As described above, assuming that the polysilicon films 52 used in FIGS. 12A and 13A have the same thickness Th, the smaller the width (size) of the polysilicon film 52, the smaller the taper angle of the mask can be set. The thinner the silicon oxide film 51 is shaved, the smaller the taper angle of the mask can be set.

It is also possible to control the taper angle of the mask by combining these taper mask forming methods.

Here, a case where a Pt film having a thickness of 0.5 μm is specifically etched using the etching apparatus of FIG. 3 using a mask of SiO 2 will be described with reference to FIG.

As described above, the gas used for etching is mainly chlorine, and a bias voltage is applied to the wafer for etching. At this time, since the etching rate of SiO2 and the etching rate of Pt are about the same, SiO2 is used. The thickness of the mask needs to be equal to or larger than the thickness of Pt, and here, it is 0.
5 μm.

In the apparatus of FIG. 1, rd / re is a certain value or more under the condition that the plasma can be stably maintained, and its minimum value is 0.4 here. At this time, according to FIG. 6, when the taper angle of the SiO2 mask is 90 °,
By etching Pt, the taper angle of the Pt film becomes 57 °.

That is, the width y of the bottom surface of Pt is larger than the width of the SiO 2 mask by about 0.3 μm on each side x1 and x2. This is x1 = x2 = 0.5 μm ÷ tan φ
= 0.5 μm ÷ tan 57 ° Therefore, if the total width of the mask is 0.5 μm and the Pt film is etched by 0.5 μm, the width y of the bottom surface of Pt is y = 0.5 μm.
It becomes m + x1 + x2 = 1.1 μm.

However, if the SiO 2 mask is made to have a taper angle of 80 ° by any of the above-mentioned methods and etching is performed under the same conditions, the taper angle of the Pt film after etching is 70 °, and the bottom surface of the Pt film is The width y is larger than the width of the mask by about 0.2 μm on one side. Therefore, Pt
The total width y of the bottom surface of the film is about 0.9 μm (y = 0.5 μm +
0.2 μm + 0.2 μm).

By making the taper angle of the mask small in this way, the taper angle of the Pt film after etching becomes large. In other words, the etching shape can be controlled by the taper angle of the mask.

Further, if the taper angle of the mask is made small (for example, 60 °), the taper angle of the etching becomes large, but it becomes a condition that deposits do not adhere to the mask, so that the problem of scraping the mask becomes a problem.

Therefore, the taper angle becomes large,
Moreover, the condition for keeping the size of the bottom surface of the mask before etching is to set the taper angle of the mask to θ0.

The taper angle θ0 of this mask can be predicted from the results of etching using a vertical mask. That is, as a result of etching using a vertical mask,
It is assumed that φ (for example, 60 °) is obtained. At this time
Thus, the value of rd / re (0.37) under that condition can be estimated. Formula to predict the taper angle of the above etching

Tan φ = (re-rd) / ((rd-r
The estimated value (0.37 in this case) for rd / de may be substituted for e × cos θ) × sin θ) to obtain θ (77 °) satisfying φ = θ.

(C) Next, a silicon oxide mask whose sidewalls are almost vertical (that is, the taper angle is about 90 degrees) is used, and FIGS. 14A to 14F show a method in which the effect of the taper mask is substantially obtained. It will be described with reference to FIG. First,
Using a mask of silicon oxide 51 whose side walls are substantially vertical, a predetermined amount, for example, half, of the desired etching amount of Pt50 as the material to be etched is etched (FIG. 14).
B). As described above, in this state, the silicon oxide 51
Deposits 55 are attached to the side wall of the mask of FIG.
B). Next, the deposits are removed (FIG. 14C). As a method for removing the deposit, a wet treatment using pure water, ammonia water, sulfuric acid, hydrochloric acid, alcohol, or a mixture thereof is typical. After removing the deposit 55, the taper angle of the protrusion 50a of the Pt 50, which is the material to be etched, is φ1. After removing the deposit, the remaining amount of Pt50 is etched again to perform the desired amount of etching (FIG. 14D). At this time, the deposition film 56 is deposited on the mask of the silicon oxide 51 and the side wall of the convex portion 50a of the Pt 50, and the deposition film is deposited almost in the same manner as the first deposition film 55. Pt is exposed on the side wall of the convex portion 50b of the Pt 50 that is cut by the second etching. The taper angle of the protrusion 50b of the Pt 50 thus obtained is φ2 (here, φ1 <φ2). Thus, by the first etching and the removal of deposits immediately after that, as shown in FIG. 14C, the taper angle formed by the silicon oxide 51 and the protrusion 50a of the Pt 50 is φ1.
, A substantially tapered mask can be obtained. By using such a substantial taper mask, the taper angle of the material to be etched can be made close to vertical.

By repeating such etching and removal of deposits a plurality of times, the taper angle of the material to be etched can be made closer to a vertical angle. If Pt, which is the material to be etched, is exposed on the side wall instead of the deposit in the shape obtained immediately after etching, there is an advantage that Pt is immediately etched during overetching. When the deposition film is exposed, the deposition film is first etched during overetching, and then Pt, which is the material to be etched, is etched. Therefore,
There is also an advantage that the overetch time can be shortened.

Next, a method for removing deposits will be described.

As a method of removing the deposits, in addition to wet treatment, treatment using water or CO 2 in a supercritical state, or dry treatment using an appropriate gas system can be considered. This dry treatment may be performed using the same processing apparatus (same reaction container) as the Pt etching treatment. Further, the etching of a certain number of times and the etching of another number of times may use the same etching apparatus (the same reaction container) or another etching apparatus (another reaction container).

As the dry treatment, for example, oxygen, hydrogen, ammonia, chlorine, hydrogen chloride or alcohol may be introduced to generate plasma, and the sample may be subjected to plasma treatment.

As another method of wet treatment, for example, there is a method of exposing carbon dioxide in a supercritical state to a material to which ammonia, alcohol, hydrochloric acid, hydrogen peroxide solution or the like is added. Can be removed.

If necessary, a rinsing and drying step may be added before or after the deposit removal step. For example, when a wet process using a chemical solution is performed as a method for removing deposits, a cleaning process using pure water may be performed, and then a drying process may be performed. When the etching is performed in this manner, there is a point where the taper angle changes (abruptly) in the middle of the side wall of the mask or the material to be etched. Alternatively, it is possible to provide a portion having a clearly different taper angle in the middle of the side wall of the mask or the material to be etched. It should be noted that most metal chlorides are water-soluble.

Next, a case where the present invention is applied to a semiconductor device manufacturing apparatus will be described with reference to FIGS. 15A and 15B.

The semiconductor manufacturing apparatus shown in FIG. 15A is a multi-chamber semiconductor device manufacturing apparatus, and includes an etching processing chamber 901, a wafer transfer robot 903, a load lock chamber 904, an unload lock chamber 905, a loader 906, and a stocker 907. Have. Stocker 907
A cassette 908 is placed in. Wafer processing chamber 901
Cassette 9 under almost atmospheric conditions
The wafer 105 placed in 08 is carried by the loader 906 to the load lock chamber 904 under almost atmospheric pressure, and the load lock chamber is closed. After the pressure in the load lock chamber 904 is reduced to an appropriate pressure, the wafer transfer robot 903
Then, the wafer 105 is transferred to the processing chamber 901 and etched halfway. After that, the wafer 105 is transferred to the deposit removal processing chamber 902 by the wafer transfer robot 903, and the deposit on the side wall is removed. Then, again, the wafer 105 is transferred to the etching processing chamber 901 ′ by the wafer transfer robot 903, and is etched by a desired amount. After that, the wafer 105 is transferred to the deposition removal processing chamber 902 ′ to remove the deposition on the side wall. Then, the wafer 105 is transferred to the unload lock chamber 905 by the wafer transfer robot 903. After raising the pressure of the unload lock chamber 905 to almost atmospheric pressure, the cassette 90 is loaded by the loader 906.
Insert in 8.

Thus, FIG. 15A shows a wafer transfer device (903), a plurality of processing chambers (901, 901 ') connected to the wafer transfer device, and a plurality of post-processing chambers (90).
2, 902 ') and a plurality of lock chambers (904,
905) and an atmospheric transfer device (906) adjacent to the lock chamber, the atmospheric transfer device being connectable to the plurality of lock chambers and a wafer cassette (908) adjacent to the atmospheric transfer device. A device,
After etching a material to be processed in any one of the plurality of processing chambers, post-processing is performed in any one of the plurality of post-processing chambers, and then etched in any one of the plurality of processing chambers. In addition, the post-treatment is performed in any one of the plurality of post-treatment chambers.

Although the atmospheric cassette is used in the example of FIG. 15A, a vacuum cassette may be used as shown in FIG. 15B. That is, FIG. 15B shows a wafer transfer device (903),
A plurality of processing chambers (901, 9) connected to the wafer transfer apparatus.
01 ') and a plurality of lock chambers (904, 90
5) and an atmospheric transfer device (906) adjacent to the lock chamber, the atmospheric transfer device including the plurality of lock chambers and a post-treatment chamber (9) adjacent to the atmospheric transfer device.
02) and a wafer cassette (908), which is a semiconductor manufacturing apparatus, in which a material to be processed is etched in any one of the plurality of processing chambers, and post-processing is performed in the post-processing chamber. Etching may be performed in any one of the plurality of processing chambers, and post-processing may be performed in the post-processing chamber.

Furthermore, for the sake of explanation, the deposit removal process is performed under vacuum conditions, but it may be performed under atmospheric pressure conditions.

In the above example, the etching process is performed twice using the different etching process chambers 901 and 901 ', but only the same process chamber 901 may be performed multiple times. The advantage of using another processing chamber as the etching processing chamber is that when the laminated film is etched, it can be stably etched under different conditions for each film type. It is also possible to perform the etching and the removal treatment of the deposits in the same chamber.

Next, using the method (c) shown in FIGS. 14A to 14F, the laminated film of Pt / PZT / Pt, which is the memory portion of the ferroelectric memory, is formed using a substantially tapered mask. 16A
This will be described with reference to -16D. In this case, if the Pt / PZT / Pt films 61-63 shown in FIG. 16A are processed by one-time etching, deposition of deposits inevitably progresses on the sidewalls of these layers 61-63, and the shape shown in FIG. 16D is formed. Becomes That is, the difference between the size of the mask 64 and the size of the material to be etched obtained becomes large. This dimensional difference hinders miniaturization.

Therefore, immediately before etching the conductor (for example, Pt) film 61 located under the insulating film (PZT) 62, the etching is interrupted to remove the deposit (FIG. 16).
B). Then, the taper angle of the PZT / Pt films 62-63 becomes φ3. After that, when etching is performed again,
A shape as shown in FIG. 16C is obtained. In this case, P
The taper angle of the t film 61 is φ4 (here, φ3 <
φ4). A characteristic is that conductors (for example, Pt films 61 and 63) of the same material are formed above and below the insulating film (PZT) 62, but the taper angles φ3 and φ4 thereof are different. Of course, the taper angle φ4 can be set larger than the taper angle φ5 shown in FIG. 16D.

As shown in FIG. 16C, the first etching and the removal of deposits immediately after the first etching, as shown in FIG.
A substantial taper mask having a taper angle of φ3, which is composed of the insulating film (PZT) 62 and the conductor (for example, Pt) film 63, can be obtained. By using such a substantial taper mask, the taper angle of the material to be etched can be made close to vertical in the laminated film.

Further, by using the method (c) shown in FIGS. 14A-14F or the method shown in FIGS. 16A-16C, MRA expected as a next-generation memory device.
A method of etching a laminated film of M (magnetic random access memory) using a substantially tapered mask will be described with reference to FIGS. 17A to 17D.

The MRAM has a laminated film as shown in FIG. 17A. That is, a ferromagnetic material (for example, Co) from above
76, an insulating film (for example, Al2O3) 75, a ferromagnetic material (for example, Co) 74, an antiferromagnetic material (for example, FeMn) 73,
Base materials (for example, Co and Si) 72 and 71. In addition,
70 is, for example, a silicon oxide film 70. In MRAM, it is required to etch these films 71-76 using one mask.

In this case, for example, when the adhesion of the reaction product of the FeMn film 73 is stronger than the adhesion of other materials, F
Immediately before starting the etching of the eMn film 73, the etching is interrupted to remove the deposit (FIG. 17B). Then, the taper angle of the films 74-76 becomes φ6. After that, when the etching is restarted, the FeMn film 73 can also be etched into a nearly vertical shape (FIG. 17C). Fe at this time
As for the taper angle of the Mn film 73, φ7 is φ6 <φ7.
Thus, by the first etching and the removal of the deposits immediately thereafter, and the second etching and the removal of the deposits immediately thereafter, as shown in FIG. 17C, films 73-76 are formed.
A substantially tapered mask having the taper angle changed in the above is obtained. By using such a substantial taper mask 73-77, the taper angle φ8 of the material to be etched 71, 72 can be made close to vertical in the laminated film such as MRAM (here,
φ6 <φ7 <φ8).

The ferromagnetic material is considered to be
Mainly Fe, Co, Ni, Mn or their compounds, all of which are known as difficult-to-etch materials. In the figure, reference numeral 77 is a mask.

In the above example, the method of devising the mask shape or the substantial taper mask shape in order to make the side wall of the material to be etched substantially vertical has been described. This is a method in which the sidewall of the material to be etched can be formed into a vertical shape by changing the conditions.

As described above, the etching taper angle is determined by the ratio rd / re of the mask or the deposition rate rd to the side wall of the material to be etched and the etching rate re of the bottom surface. The smaller the rd / re, the material to be etched. The side wall taper angle can be made close to vertical.

Up to now, the etching has been performed under the condition that the deposits are less likely to adhere to the wall of the vacuum container (104 in FIG. 3). However, in order to reduce the deposits of the deposits, the reaction product in the vacuum container is reduced. It is effective to reduce the concentration of. Under conditions where the depot does not adhere to the walls of the vacuum container, in order to reduce the concentration of the reaction products in the gas phase, exhaust the reaction products in the gas phase to the outside of the vacuum container or use a mask or a material to be etched. There is no way but to attach it to the side wall. Therefore, in reality, the concentration of the reaction product in the gas phase is kept high under the condition that the depot does not adhere to the wall of the vacuum container.

However, in FIG. 3, by lowering the impedance of the load 115 and decreasing the current flowing through the electrostatic coupling antenna 118, the reaction product can be easily attached to the wall of the vacuum container 104. At this time, the concentration of the reaction product in the vapor phase is reduced by adhering to the wall of the vacuum container, so that the amount of the reaction product entering the wafer from the vapor phase is reduced. As a result, deposition of deposits on the sidewalls of the mask and the material to be etched is reduced, and therefore, even if a mask having sidewalls of about 90 degrees is used, the sidewalls of the material to be etched are almost vertical.

However, if deposits adhere to the wall of the vacuum container, the state of plasma may change or particles may be generated, so it is necessary to remove deposits regularly. Therefore, for example, the deposit removal process (that is, the process of increasing the current flowing through the electrostatic coupling antenna 118) is performed every time one or a plurality of wafers are processed.

At this time, the wafer support table (sample table) 109
The temperature of the wafer is set higher than that at the time of etching so that the deposits are not attached to the wafer support base 109.
The deposit may be quickly evacuated to the outside of the vacuum container 104. Alternatively, conversely, the temperature of the wafer support base 109 is lowered, and the deposit is positively attached to the support or the wafer placed on the support so that the deposit is placed on the support or the support. It is also possible to prevent the deposits from adhering to the wall of the vacuum container again by promoting the evacuation of the deposits by preventing the deposits from being reflected from the wafer.

[0088]

According to the present invention, in the etching of a material in which it is difficult to obtain a processed shape in which the side wall is vertical, the etching shape in which the side wall is almost vertical can be obtained by using a tapered mask or the like. A device or a highly integrated semiconductor device can be produced.

[Brief description of drawings]

FIG. 1 is a cross-sectional view for explaining an etching process using a mask whose sidewalls are vertical.

FIG. 2 is a cross-sectional view for explaining an etching process using a mask whose sidewalls are vertical.

FIG. 3 is a diagram showing an example of the overall configuration of a plasma etching apparatus to which the present invention is applied.

FIG. 4 is a sectional view for explaining an etching process when the taper angle θ of the mask is less than 90 degrees.

FIG. 5 is a cross-sectional view for explaining the relationship between the deposition state of deposits on the sidewall of the mask and the taper angle φ of the material to be etched when the taper angle θ of the mask is gradually decreased from 90 degrees.

FIG. 6 is a diagram showing a relationship between a taper angle of a mask and a taper angle of a material to be etched.

FIG. 7 is a diagram showing the relationship between the taper angle of the mask and the taper angle of the material to be etched in the region where the taper angle of the mask is less than the limit value and the region where the mask taper angle is greater than the limit value.

FIG. 8 is a diagram for explaining a method of controlling the taper angle of a mask by the composition of etching gas and etching pressure.

FIG. 9 is a diagram for explaining a method of controlling the mask taper angle by wet etching.

FIG. 10 is a diagram for explaining a method of controlling the taper angle of the mask by wet etching.

FIG. 11 is a view for explaining another method of controlling the taper angle of the mask by wet etching.

FIG. 12 is a diagram for explaining a method of controlling the taper angle of a mask by dry etching and wet etching.

FIG. 13 is a diagram for explaining another method of controlling the taper angle of the mask by dry etching and wet etching.

FIG. 14 is a diagram for explaining a method in which the effect of a substantially tapered mask is obtained by using a mask having a taper angle of about 90 degrees.

FIG. 15A is a block diagram showing a configuration example of a semiconductor device manufacturing apparatus to which the present invention is applied, and FIG. 15B is a block diagram showing another configuration example of a semiconductor device manufacturing apparatus to which the present invention is applied.

FIG. 16 is a diagram for explaining a method of obtaining the effect of a substantially tapered mask by using a mask having a taper angle of about 90 degrees in a ferroelectric memory.

FIG. 17 is a diagram for explaining a method in which the effect of a substantially tapered mask is obtained by using a mask having a taper angle of about 90 degrees in MRAM.

FIG. 18 is a cross-sectional view for explaining an etching process using a mask whose sidewalls are vertical.

[Explanation of symbols]

10 masks 20 Etching material 21 Upper surface of material to be etched 25 Depot 30 Top surface of deposit

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Ryoji Nishio             Higashi-Toyoi 794, Kudamatsu City, Yamaguchi Prefecture             Standing High Technologies Design & Manufacturing Division             Kasado Office (72) Inventor Taketo Usui             502 Kintatemachi, Tsuchiura City, Ibaraki Japan             Tate Seisakusho Mechanical Research Center F-term (reference) 5F004 AA04 AA12 BD07 CA02 CA06                       CA08 DA01 DA16 DB08 DB12                       DB13 EA10 EA28 EA40 EB01                       FA07

Claims (21)

[Claims] 1. In a method of etching the film using plasma, using a film of a difficult-to-etch material formed on a substrate and a mask formed on the film, wherein a sidewall of the mask has an angle with respect to a surface of the substrate. 90
An etching method comprising the step of etching using a mask having a degree of less than 100 degrees. 2. The etching method according to claim 1, wherein the film is Fe, Co, Mn, Ni, Pt, Ru, RuO2, Ta, Ir, IrO.
2, Os, Pd, Au, Ta2O5, PZT, BST, SBT, Al2O3, HfO2,
An etching method characterized by being one of ZrO2, GaAs, and ITO. 3. A method of etching a film using plasma using a film of a difficult-to-etch material formed on a substrate and a mask formed on the film, wherein a taper angle of a sidewall of the mask with respect to a surface of the substrate. Etching using a mask with (θ) less than 90 degrees,
Thereby, the etching method is characterized by including a step of setting the taper angle (φ) of the film after etching with respect to the surface of the substrate to be equal to or larger than the taper angle (θ) of the mask. 4. A method of etching the film using plasma using a film of a difficult-to-etch material formed on a substrate and a mask formed on the film, wherein the side wall of the mask is relative to the surface of the substrate. An etching method comprising: a step of shaping the mask so that a taper angle formed is less than 90 degrees; and a step of etching using the mask. 5. The etching method according to claim 4, wherein the step of forming the mask includes a step of etching the mask. 6. The method of etching a difficult-to-etch material according to claim 5, wherein the step of etching the mask includes a step of adjusting a taper angle of the mask by adjusting etching conditions of the mask. Etching method. 7. The etching method for a difficult-to-etch material according to claim 6, wherein the etching condition is at least one of a composition of a gas introduced into the etching chamber and an etching pressure. 8. The method of etching a difficult-to-etch material according to claim 5, wherein the step of etching the mask adjusts the taper angle of the mask by adjusting at least one of the thickness of the film and the etching time of the mask. An etching method comprising the step of adjusting. 9. The method of etching a difficult-to-etch material according to claim 5, wherein in the step of etching the mask, at least one of a size of a photoresist film formed on the mask and an etching time of the mask is adjusted. Thus, the etching method comprising the step of adjusting the taper angle of the mask. 10. The method of etching a difficult-to-etch material according to claim 5, wherein the step of etching the mask includes a step of performing cleaning during the etching of the mask, and then performing the etching of the mask again. Etching method characterized by. 11. The method for etching a difficult-to-etch material according to claim 10, wherein the step of etching the mask comprises the size of the photoresist film formed on the mask and the etching time of the mask before the cleaning. An etching method comprising the step of adjusting the taper angle of the mask by adjusting at least one of them. 12. The etching method according to claim 4, wherein the film comprises Fe, Co, Mn, Ni, Pt, Ru, RuO2, Ta, Ir, IrO2, Os, Pd, Au, Ti, TiOx, SrRuO3, ( La, Sr) Co O3, Cu (Ba, Sr) TiO3, SRO: SrTiO3, BTO: BaTiO3, SrTa2O6, Sr2Ta2O7, ZnO, Al2O3, ZrO2, HfO2, Ta2O5 Pb (Zr, Ti) O3, Pb (Zr, Ti) Characterized by being any one of Nb2O8, (Pb, La) (Zr, Ti) O3, PbTiNbOx, SrBi2Ta2O9, SrBi2 (Ta, Nb) 2O9, Bi4Ti3O12, BiSiO _x , Bi _4-x La _x Ti ₃ O ₁₂ InTiO Etching method. 13. A method of manufacturing a semiconductor using at least one layer of a hard-to-etch material formed on a substrate and a mask formed thereon, wherein the hard-to-etch material is etched using the mask, Cleaning is performed during the etching, and then
A method for manufacturing a semiconductor, comprising a step of etching the difficult-to-etch material again using the mask. 14. A semiconductor device manufactured by the semiconductor manufacturing method according to claim 13, comprising a substrate and at least one layer of a difficult-to-etch material formed on the substrate, and a sidewall of the hard-to-etch material. A semiconductor device characterized in that a taper angle changes in the middle of the side wall. 15. A semiconductor device manufactured by the semiconductor manufacturing method according to claim 13, comprising a substrate and at least two layers of a difficult-to-etch material formed on the substrate, and a layer having the hard-to-etch material. The taper angle of the side wall of the semiconductor device is different from the taper angle of the side wall of another layer of the difficult-to-etch material. 16. An etching method for depositing a reaction product on a wall of an etching apparatus, wherein the reaction product is continuously deposited on the wall of the etching apparatus until the processing of at least one wafer is completed, whereby a substrate is formed. An etching method comprising the step of forming an angle of the sidewall of the material to be etched formed on the substrate with respect to the surface of the substrate to be substantially 90 degrees. 17. The etching method according to claim 16, further comprising the step of periodically removing the reaction product adhering to the wall of the etching apparatus. 18. The etching method according to claim 16, further comprising the step of etching using a mask in which a sidewall of the mask forms an angle of less than 90 degrees with respect to the surface of the substrate. 19. A wafer transfer device, a plurality of processing chambers and a plurality of post-processing chambers connected to the wafer transfer device, a plurality of lock chambers, and an atmosphere transfer device adjacent to the lock chambers, the atmosphere being provided. In a method of performing etching using a semiconductor manufacturing apparatus in which a transfer device is connectable to the plurality of lock chambers and a wafer cassette adjacent to the atmospheric transfer device, the method comprises: After etching in any one, after-treatment is performed in any one of the plurality of post-treatment chambers, then etched in any one of the plurality of treatment chambers, further An etching method comprising a step of performing a post-treatment with any one of them. 20. A wafer transfer device, a plurality of processing chambers connected to the wafer transfer device, a plurality of lock chambers, and an atmospheric transfer device adjacent to the lock chamber, wherein the atmospheric transfer device includes the plurality of processing chambers. In a method of performing etching using a semiconductor manufacturing apparatus connectable to a wafer chamber and a post-processing chamber adjacent to the lock chamber and the atmospheric transfer device, the method comprises: After etching with one, post-treatment is performed in the post-treatment chamber, then,
An etching method comprising a step of performing etching in any one of the plurality of processing chambers and further performing post-processing in the post-processing chamber. 21. Pt, Ru, Ir, PZ formed on a substrate
T, SBT, Co, Mn, using a film formed of any one of Fe and a mask formed thereon, in the method of etching the film using plasma, the sidewall of the mask is the surface of the substrate Angle to 80
An etching method comprising the step of etching using a hard mask of less than 100 degrees.