KR100789894B1 - Etching method of hardly-etched material and semiconductor fabricating method and apparatus using the method - Google Patents

Abstract

The present invention uses a film of a non-etching material formed on a substrate and a mask formed thereon, using a mask in which the sidewall of the mask is less than 90 degrees to the surface of the substrate when the film is etched using plasma. By etching, the taper angle with respect to the surface of the substrate of the film after etching is made to be equal to or greater than the taper angle of the mask.

Description

Etching method of non-etching material and semiconductor manufacturing method and apparatus using same {ETCHING METHOD OF HARDLY-ETCHED MATERIAL AND SEMICONDUCTOR FABRICATING METHOD AND APPARATUS USING THE METHOD}

1A to 1F are cross-sectional views for explaining an etching process using a mask having vertical sidewalls;

2A to 2G are cross-sectional views for explaining an etching process using a mask having vertical sidewalls;

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

4A to 4D are cross-sectional views for explaining an etching process when the taper angle θ of the mask is less than 90 degrees;

5A to 5D are cross-sectional views for explaining the relationship between the deposition state of the deposit on the mask side wall and the taper angle φ of the etching target material when the taper angle θ of the mask is gradually decreased from 90 degrees;

6 is a diagram showing a relationship between a taper angle of a mask and a taper angle of an etching target material;

7A and 7B are diagrams showing the relationship between the taper angle of the mask and the taper angle of the etching target material in a region where the taper angle of the mask is less than the threshold and the region is greater than or equal to the threshold;

8A to 8E are diagrams for explaining a method of controlling the taper angle of the mask by the component of the etching gas or the etching pressure;

9A to 9E are views for explaining a method of controlling the taper angle of the mask by wet etching;

10A to 10I are views for explaining a method of controlling a taper angle of a mask by wet etching;

11A to 11I are views for explaining another method of controlling the taper angle of the mask by wet etching;

12A to 12D are views for explaining a method of controlling a taper angle of a mask by dry etching and wet etching;

13A to 13D are views for explaining another method of controlling the taper angle of the mask by dry etching and wet etching;

14A to 14F are views for explaining a method of obtaining a substantially tapered mask effect by using a mask having a taper angle of approximately 90 degrees;

15A is a block diagram showing a configuration example of a semiconductor device manufacturing apparatus to which the present invention is applied;

15B is a block diagram showing another configuration example of a semiconductor device manufacturing apparatus to which the present invention is applied;

16A to 16D are views for explaining a method of obtaining a substantially tapered mask effect by using a mask having a taper angle of approximately 90 degrees in a ferroelectric memory;

17A to 17D are diagrams for explaining a method in which an effect of a substantially tapered mask is obtained by using a mask having a taper angle of approximately 90 degrees in an MRAM;

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

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for etching a HYRDLY-ETCHED MATERIAL such as Pt, Ru, Ir, PZT, and Hf02, a semiconductor integrated circuit device including an egg etch material, and a method for manufacturing the same. A technique effective for etching sidewalls into near vertical shapes.

Conventionally, as a means of processing the surface of a semiconductor element, the method of etching using a taper shape or a round head photoresist is known.

Methods of etching using a tapered mask are disclosed in U.S. Patent No. 5818107 (Japanese Patent Laid-Open No. Hei 10-214826) and Japanese Patent Laid-Open No. Hei 10-223855. In addition, a method of etching using a round photoresist is disclosed in U.S. Patent No. 60708701 (Japanese Patent Laid-Open No. 10-98162).                         

However, the etching of the nonvolatile material which is a material which is difficult to etch (hereinafter only referred to as an hard etching material) may be performed at a high temperature of 300 ° C. or higher, so that a photoresist may not be used.

However, with the miniaturization and speed of operation of semiconductor devices, alumina, zirconium oxide, hafnium oxide, ruthenium oxide, platinum, tantalum oxide may be applied to the gate insulating film, gate electrode, or memory capacitor of the M0S (meta1-oxide-semiconductor) transistor. , Materials such as BST, SBT, and PZT have been considered. In magnetic random acccess memory (MRAM), iron, nickel, cobalt, manganese or alloys thereof are used.

Moreover, the following are mentioned as a hard etching material, for example.

Magnetic material: (Use: Magnetic disk, MRAM, etc.) Fe, Co, Mn, Ni, etc.

Precious metals, etc. (Use: Various electrodes, etc.) Pt, Ru, Ru02, Ta, Ir, IrO ₂ , 0s, Pd, Au, Ti, TiOx, SrRuO ₃ , (La, Sr) Co0 ₃ , Cu, etc.

High-k dielectric: [Use: Capacitor of DRAM (charge)]

BST: (Ba, Sr) Ti0 3, SR0: SrTiO 3, BT0: BaTi0 3, SrTa 2 0 6, Sr 2 Ta 2 0 7, ZnO, Al 2 0 3, Zr0 2, Hf0 2, Ta 2 0 5 , etc.

Ferroelectric: (Use: Capacitor of FeRAM, etc.)

PZT: Pb (Zr, Ti) 0 ₃ , PZTN: Pb (Zr, Ti) Nb ₂ 0 ₈ , PLZT: (Pb, La) (Zr, Ti) O ₃ ,

PTN: PbTiNbOx, SBT: SrBi ₂ Ta ₂ O ₉ , SBTN: SrBi ₂ (Ta, Nb) ₂ 0 ₉ ,

BTO: Bi ₄ Ti ₃ 0 _l2 , BiSiO _x , BLOT: Bi _4-x La _x Ti ₃ 0 ₁₂ etc.

Compound Semiconductor: GaAs, etc

ITO and others: InTiO, etc.

These non-etching materials are more difficult to etch than aluminum, silicon, silicon oxide, and the like, and in particular, it is difficult to process the sidewalls of the non-etching material into a shape perpendicular to the substrate.

None of the above known documents suggests that the sidewall of the non-etching material is processed into a shape perpendicular to the substrate.

Next, chemically stable materials, such as iron, cobalt, manganese, nickel, platinum, ruthenium, tantalum, alumina, hafnium oxide, zirconium oxide, and gallium arsenide, are etched using plasma to obtain a vertical etching shape in the etching target material. The reason for the difficulty is explained below.

In a material that is difficult to etch, such as the hard etching material described above, the reaction product is formed by etching, and the reaction product springs from the surface of the sample to the gaseous phase, and then reaches a wall of the material to be etched. Therefore, if the reaction product adheres only to the position where etching proceeds in the etching target material, the etching rate is substantially lowered, but the reaction product is actually attached to all positions of the etching target material. That is, the reaction product adheres to the sidewall where etching is not substantially performed in the etching target material. As a result, the etching of the bottom surface where the etching proceeds and deposition of the deposition material of the sidewall proceed simultaneously. In the side wall, the shape perpendicular to the substrate is not obtained. The above is the reason that in etching of the hard etching material, the etching shape in which the side wall of the etching target material is perpendicular to the substrate surface is not obtained.

The reason why the etching shape perpendicular to the substrate is not obtained on the sidewall of the etched material described above will be described in more detail with reference to FIGS. 1A to 2G.

1A and 2A are initial states of etching, in which the arrow on the right side shows the deposition direction of the deposit and the arrow on the lower side shows the etching direction. Here, the angle (taper angle) θ with respect to the upper surface of the substrate on the sidewall of the mask 10 is 90 degrees. When the minute unit time Δt has elapsed from the initial state, the bottom surface (upper surface 21 of the etching target material 20 exposed to the plasma) is etched by Δe to form sidewalls of the mask 10 and the etching target material 20. Deposits 25 are deposited by Δd (Figs. 1B and 2B). In reality, however, since the upper surface portion 30 of the deposit is also etched, the angle (taper angle) φ formed by the portion with respect to the substrate surface is determined by the deposition amount (deposition rate) Δd of the deposit per unit time and the etching per unit time. Amount (etching rate Δe).

In the portion 32 immediately below the mask sidewall, at the moment when deposition of the deposit 25 on the sidewall of the mask starts, the lower bottom surface portion 33 (etched material 20 exposed to the plasma) of the deposit on the mask sidewall Etching on the upper surface 21 of the () stops. However, when the exposed portion of the material to be etched 20 is etched under the sidewall of the deposit 25 on the sidewall of the mask, the deposit is deposited on the exposed surface at the moment when the sidewall of the new material to be etched 20 is exposed. . The etching therefore proceeds obliquely downwards (FIGS. 1C and 2C).

Subsequently, when the unit time Δt has elapsed again from the states of FIGS. 1C and 2C, deposition of the deposit 25 proceeds again on the sidewall of the deposit 25, and etching is performed on the lower sidewall of the deposit 25. Etching advances also in the exposed part of the ash 20 (FIGS. 1D, 1E, 2D, 2F). Thus, etching progresses obliquely downward in order, and the etching shape shown to FIG. 1F and FIG. 2G is obtained. In this way, the sidewalls of the material to be etched form a taper angle φ (φ <90 degrees) with respect to the substrate surface.

SUMMARY OF THE INVENTION An object of the present invention is to provide a method for etching a hard etching material and a semiconductor manufacturing method and apparatus using the same, which can solve the problems of the prior art.

Another object of the present invention is to provide a method and apparatus for treating a surface of a sample which can stabilize the processing of a plurality of wafers or make the taper angle of the etching target material close to a vertical angle in order to meet the demand for miniaturization of semiconductor devices and the like. will be.

A feature of the present invention is a method for treating a surface of a sample which is etched using a tapered mask when 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 non-etching material formed on a substrate and a mask formed thereon, wherein the sidewall of the mask has an angle of 90 with respect to the surface of the substrate. Etching using a mask that is less than a degree.

Therefore, according to the present invention, since the sidewalls are etched close to the vertical shape by using a tapered mask or the like in the etching of materials in which the sidewalls are not vertically processed, a high-performance semiconductor device or a semiconductor having a high degree of integration You can create a device.

EMBODIMENT OF THE INVENTION Below, the Example of this invention is described in detail with reference to an accompanying drawing.

3 is a diagram showing an example of the entire configuration of a plasma etching apparatus to which the present invention is applied. The vacuum vessel 104 which supplies a high frequency current to the coil 103 from the high frequency power supply 101 via an automatic matching unit 102 to generate the plasma 105 in the vacuum vessel 104, A discharge part 104a made of an insulating material and a grounded processing part 104b. An etching gas such as chlorine is introduced into the vacuum vessel 104 through the gas introducing portion 106, and the gas is exhausted by the exhaust system 107.

The sample 108 is placed on the sample table 109. In order to increase the ion energy 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 such as ceramic is provided on the surface of the sample stage 109. In addition, the sample stand 109 is connected to the DC power supply 113 via the low pass filter 114 to hold the sample 108 to the sample stand 109 by electrostatic force.

In addition, in order to control the process by adjusting the temperature of the sample 108, the heater 115 and the refrigerant passage 116 are provided in the sample stage 109.                     

Typical conditions for etching chemically stable materials such as iron, cobalt, manganese, nickel, platinum, ruthenium, tantalum, alumina, hafnium oxide, zirconium oxide, gallium arsenide, etc. using this apparatus are as follows. The pressure of the apparatus is 0.5 Pa, and the gas to be introduced is mainly chlorine. The temperature of the sample 108 varies depending on the target material to be etched, but is 200 ° C or more and 500 ° C or less. This is determined by the required etching rate or the semiconductor device to be manufactured, but the temperature of the sample 108 is maintained at a high temperature as compared with a typical temperature of 0 ° C. to 100 ° C. when etching a silicon film, an aluminum film or a silicon oxide film. do. Therefore, a photoresist cannot be effectively used for the mask material of etching, and silicon oxide or a hard mask of a metal is used in many cases.

In order to perform the above-mentioned problem in etching of the hard etching material, that is, the etching process in which the taper angle φ of the material to be etched can be set to an angle perpendicular to the surface of the substrate, the amount of deposits attached to the sidewalls of the mask is suppressed. It is important to do.

As such a method of suppressing the deposition of 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. However, the pressure and the flow rate of the gas are often limited to an appropriate range in order to obtain desirable etching characteristics, and the limits of the pressure and the flow rate are determined by the exhaust capacity. Therefore, it is difficult to suppress deposition of deposits by pressure, flow rate, and the like.

Next, by using a mask (that is, a tapered mask) whose taper angle (angle with respect to the substrate upper surface of the mask 10 sidewall) (θ) is less than 90 degrees, the taper angle of the etching target material (the The reason why the processing shape close to perpendicular to the angle φ relative to the substrate surface is obtained will be described with reference to FIGS. 4A to 5D. In addition, in FIG. 5A, when the taper angle θ of the mask is set to 90 degrees, as described with reference to FIGS. 1A to 2G, the deposits 25 are deposited on the sidewalls of the mask 10 in parallel. 4A shows the state before etching when the taper angle θ of the mask is set to 90 degrees.

First, when the process conditions are determined, the etching rate of the bottom surface of the sample (the surface 21 of the etching target material exposed to the plasma) is determined. When etching is performed with chlorine as the main etching gas, chlorides (reaction products) of the material to be etched in the sample spring up from the substrate (data) into the etching apparatus (reaction vessel). The reaction product which jumped into the etching apparatus again enters the substrate, and some of the reaction products incident on the substrate are deposited as deposits on the substrate surface (sidewall of the mask and sidewall of the etching target material) (FIG. 4B). In most cases, this deposit can be approximate to isotropic. The deposition rate of this deposit (hereinafter simply referred to as deposition rate) is called rd. On the other hand, since etching is mainly due to the action of ions, the direction of incidence of ions at the etching target position greatly affects the etching rate at that position. In the case where the etching rate is simply determined by the flux of ions, assuming that the etch rate of the sample bottom surface on which ions are approximately perpendicularly incident is re, the etching rate when the incident angle of ions is α is re × sinα. Where re is the pure etch rate when no deposit is deposited.

That is, when the sidewall of the mask is perpendicular to the substrate surface, the deposition rate on the sidewall of the mask of the deposit is rd, and the apparent etching rate of the sample bottom surface 21 is re-rd (see FIG. 4D). At this time, the taper angle φ of the material to be etched is

tanφ = (re-rd) / rd                     

to be.

On the other hand, as shown in Figs. 4B and 5B, when the sidewall 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 with respect to the sidewall of the mask is isotropic. rd, and the etching rate of the mask sidewall is re x cos θ. Therefore, rd-re * cos (theta) is a deposition rate to the side wall when the taper angle of a mask is (theta). Accordingly, the taper angle φ of the material to be etched is shown in FIG. 4D.

tanφ = (re-rd) / ((rd-re × cosθ) × sinθ).

In this manner, under the condition that deposition of deposits proceeds on the sidewall of the mask, the smaller the taper angle θ of the mask, the larger the taper angle φ of the etching target material after etching. 4C shows a state in which deposits are removed after the etching treatment as shown in FIG. 4B.

When the taper angle θ of the mask is made smaller than 90 degrees, the taper angle θ is made smaller than FIG. 5B, and as shown in FIG. 5C, the taper angle θ and the taper angle of the etching target material φ ) Matches (θ = φ). This condition is a condition in which deposits do not proceed to the mask. In other words, even when deposits adhere to the mask, the deposits are etched away instantaneously, and as a result, the deposits do not adhere to the mask. If the taper angle of the mask at this time is θ0 and the taper angle of the etched material is φm, the taper angle of the etched material may be reduced even if the taper angle θ of the mask is smaller (that is, θ <θO) as shown in FIG. 5D. Is not greater than φm. That is, as shown in Fig. 5D, when θ <θO is set, θ <φm is obtained. Therefore, the limit value at which the taper angle θ0 of the mask is the taper angle φ of the etching target material to maximum (φm) do. Moreover, in the state of FIG. 5D, a mask or an underlay (etching material) is exposed.

Moreover, the relationship between the taper angle (theta) of such a mask and the taper angle (phi) of an etched material 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 vessel, flow rate of gas introduced into the reaction vessel, etc.). In general, the higher the pressure in the reaction vessel, the smaller the rd / re, and the larger the flow rate of the gas introduced into the reaction vessel, the smaller the rd / re.

As shown in FIG. 6, for example, in the case of rd / re = 0.5, if the taper angle (theta) of a mask is reduced from 90 degrees, the taper angle (phi) of an etched material will be substantially proportional to the taper angle (theta) of a mask. ) Increases. 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), resulting in the state of FIG. 5C. That is, θ = θ0 = φ = φm. Therefore, even if the taper angle (theta) of a mask is reduced more than this ((theta) <(theta) 0), the taper angle of an etched material will remain as (phi) m.

Therefore, in FIG. 6, the line L shows the limit value (theta) 0 of the taper angle of a mask. Therefore, in the area | region A, the deposit | attachment adheres to a mask in the area | region of (theta)> (theta) 0, and the taper angle (phi) of an etching target material is set to the taper angle (theta) of a mask. On the other hand, in the region (B), in the region of θ ≦ θ0, no deposit adheres to the mask, and the taper angle φ of the etching target material becomes a constant value φ m regardless of the taper angle θ of the mask. Therefore, for example, in the case of rd / re = 0.4, when the taper angle φ of the etching target material is to be set 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 taper angle of less than 90 degrees will be described. Here, as an example, the case where Pt is etched using the hard mask of silicon oxide is demonstrated.

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

Such a taper etching is, for example, J. Vac. Sci. Techno1. A 14, 1832 (1996). According to the said document, the method of controlling the taper angle of a silicon oxide film by the component of etching gas or an etching pressure is described. Specifically, the taper angle of the silicon oxide film formed by changing the pressure from 40 mTorr to 300 mTorr under etching conditions in which the flow rate of CF4 is 20 sccm and the bias power is 100 W using a photoresist having a taper angle of 86 ° is used. Changes to ° The silicon oxide film was tapered at 66 ° to 84 ° by changing the composition ratio [CHF3 in CF4 (%)] from 0% to 50% under etching conditions of 40 mTorr and total flow rate of CHF3 and CF4 at 20 sccm. .

As described above, it can be seen that the taper angle of the oxide film can be controlled by using the etch rate in the lateral direction of the silicon oxide film that is substantially independent of the pressure and decreasing the etch rate in the vertical direction as the pressure increases.

If the taper angle of the silicon oxide film can be formed below 90 degrees (FIG. 8B), the photoresist 52 is removed (FIG. 8C). Next, the substrate is transported to a predetermined position in the etching apparatus, and etching is performed (FIG. 8D), and then the mask 51 is removed (FIG. 8E).

Another etching method for forming the taper angle of the mask below 90 degrees is shown in US Pat. No. 5,856,239.

(b) Next, the method of forming the taper angle of the silicon oxide as a mask below 90 degree by wet etching is demonstrated. Such a method is described in Jpn. J. App1. Phys., Vol. 34 (1995), pp. 2132-2136. That is, as shown in FIG. 9A, the polysilicon film 52 of a predetermined pattern is formed on the silicon oxide film 51 as a mask at the time of etching Pt 50, and this is immersed in HF aqueous solution on a fixed condition. . The polysilicon film 52 is not etched with HF aqueous solution, but the silicon oxide film 51 is isotropically etched with HF aqueous solution to form a tapered shape as shown in FIG. 9B. Thereafter, when the polysilicon film is etched using chlorine (Cl ₂ ), fluorine (F ₂ ), hydrogen hexafluoride (SF ₆ ), or the like, a mask 51 of silicon oxide having a shape as shown in FIG. 9C is finally 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 some methods for forming a mask of a silicon oxide film having different taper angles with the same width (size).

First, the method shown in FIGS. 10A to 10I is to form masks of different taper angles with the same width (size) in the thickness of the silicon oxide film 51 as a mask and the wet etching time according thereto. For example, as shown in FIGS. 10A, 10D, and 10G, silicon oxide films 51 having different thicknesses T1, T2, and T3 are formed, and wet etching by HF is then performed according to the thickness of the silicon oxide film. By performing for a time, masks of different taper angles can be formed as shown in FIGS. 10B, 10E, and 10H, respectively. Therefore, after the polysilicon film 52 is removed, the taper angles θ1, θ2, and θ3 have the same widths (sizes) as shown in FIGS. 10C, 10F, and 10I, respectively, where θ1> θ2> θ3. The mask of can be formed. In other words, the larger the film thickness of the silicon oxide film 51 as a mask, the smaller the taper angle of the mask can be set.

The method shown in Figs. 11A to 11I is to form masks of different taper angles with the same width (size) in the width (size) of the polysilicon film serving as the mask and the wet etching time according thereto. For example, as shown in Figs. 11A, 11D, and 11G, respectively, polysilicon film 52 serving as a foam and a resist having different widths (sizes) (W1, W2, W3) is formed and then placed in HF. When wet etching is performed for a time corresponding to the width (size) of the polysilicon film, masks of different taper angles can be formed as shown in FIGS. 11B, 11E, and 11H, respectively. Therefore, after the polysilicon film 52 is removed, the taper angles θ4, θ5, and θ6 have the same widths (sizes), respectively, as shown in Figs. 11C, 11F, and 11I (where θ4> θ5> θ6). ) Mask can be formed. That is, as the width (size) of the polysilicon film 52 is smaller, the taper angle of the mask can be set smaller.

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

In the method shown in Figs. 12A to 12C, first, the polysilicon film 52 is patterned to a predetermined width (size) W4 (Fig. 12A), and then a part of the silicon oxide film 51 by dry etching. Is cut by a thickness Th1 that is approximately vertical (FIG. 12B), and then wet etching is performed to taper the silicon oxide film 51 (FIG. 12C).

In the method shown in FIGS. 13A to 13D, first, the polysilicon film 52 is patterned to a predetermined width (size) W5 different from the width (size) W4 (Fig. 13A), and then dry By etching, a part of the silicon oxide film 51 was cut substantially vertically by a thickness Th2 different from the thickness Th1 (FIG. 13B), and then wet etching was performed to taper the silicon oxide film 51. (FIG. 13C).

As described above, if the thickness of the polysilicon film 52 used in FIGS. 12A and 13A is the same Th, the taper angle of the mask can be set smaller as the width (size) of the polysilicon film 52 is smaller. The thinner the cut thickness of the film 51, the smaller the taper angle of the mask can be set.

By combining these taper mask formation methods mentioned above, it is also possible to control the taper angle of a mask.

Specifically, a case where the Pt film having a thickness of 0.5 μm is etched using the mask of SiO ₂ will be described with reference to FIG. 18.

As described above, the gas used for etching is mainly chlorine and is etched by applying a bias voltage to the wafer. At this time, since the etching rate of Si0 _{2 and} the etching rate of Pt are about the same, the thickness of the Si0 ₂ mask is Pt. The thickness is equal to or greater than 0.5, and the thickness is 0.5 탆 here.

In the apparatus of FIG. 1, rd / re becomes more than a predetermined fixed value on the conditions which can maintain plasma stably, and let the minimum value be 0.4 here. At this time, according to FIG. 6, when the taper angle of the Si0 ₂ mask is 90 °, the taper angle of the Pt film is 57 ° by etching Pt.

That is, the width y of the bottom surface of Pt is larger by about 0.3 占 퐉 on each of one side (x1, x2) than the width of the Si0 ₂ mask. This is obtained from x1 = x2 = 0.5 µm ÷ tanφ = 0.5 µm ÷ tan57 °. Therefore, assuming that the full width of the mask is 0.5 mu m, when the Pt film is etched by 0.5 mu m, the width y of the bottom surface of Pt is y = 0.5 mu m + x 1 + x 2 = 1.1 mu m.

By the way, if the taper angle of 80 degrees is attached to the mask of Si02 by any of the above methods, and the etching is carried out under the same conditions, the taper angle of the Pt film after etching is 70 degrees, and the width y of the bottom surface of the Pt film is masked. It is larger by about 0.2 占 퐉 on one side. Therefore, the full width y of the bottom surface of the Pt film is about 0.9 mu m (y = 0.5 mu m + 0.2 mu m + 0.2 mu m).

By reducing the taper angle of the mask in this manner, the taper angle of the Pt film after etching is increased. In other words, the etching shape can be controlled by the taper angle of the mask.

In addition, if the taper angle of the mask is made small (for example, 60 °), the taper angle of etching becomes large, but the mask is shaved because it is a condition that deposits do not adhere to the mask.

Therefore, the condition that a taper angle becomes large and the bottom surface of a mask maintains the magnitude | size before an etching is set to taper angle of (theta) 0.

The taper angle θ0 of this mask can be estimated from the etching result using the vertical mask. In other words, φ (for example, 60 °) was obtained as a result of etching using a vertical mask. At this time, the value (0.37) of rd / re in the conditions can be estimated by FIG. Equation to predict the taper angle of the etching

tanφ = (re-rd) / ((rd-re × cosθ) × sinθ)

Is substituted by a value estimated in rd / de (0.37 in this case), and θ (77 °) satisfying φ = θ may be obtained.

(c) Next, a method of using a silicon oxide mask whose sidewalls are substantially vertical (that is, having a taper angle of approximately 90 degrees), but the effect of the taper mask is obtained will be described with reference to FIGS. 14A to 14F. . First, only a predetermined amount, for example, half of the desired etching amount of Pt 50 as an etching target material is etched using a mask of silicon oxide 51 whose sidewalls are substantially vertical (FIG. 14B). As described above, the deposit 55 is attached to the side wall of the mask of the silicon oxide 51 (FIG. 14B). Next, the deposit is removed (Fig. 14C). As a removal method of this deposit, the wet process using pure water, aqueous ammonia, sulfuric acid, hydrochloric acid, alcohol, or this mixture is typical. After removal of the deposit 55, the taper angle of the convex part 50a of Pt50 which is an etching target material becomes (phi) 1. After removal of the deposit, the Pt 50 is etched again by the remaining amount to perform the desired amount of etching (FIG. 14D). At this time, a deposition film 56 is deposited on the mask of the silicon oxide 51 and on the sidewalls of the convex portion 50a of the Pt 50, and the deposition film is deposited in substantially 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 shaved by the second etching. Thus, the taper angle of the convex part 50b of Pt50 obtained becomes (phi) 2 ((phi1 <phi2) here). In this manner, the first etching and the removal of the deposit immediately thereafter yield a substantially tapered mask having a taper angle φ1 composed of the silicon oxide 51 and the convex portions 50a of the Pt 50, as shown in FIG. 14C. . By using such a substantial taper mask, the taper angle of an etching target material can be made into the angle close to a perpendicular | vertical.

In addition, by repeating such etching and deposit removal a plurality of times, the taper angle of the etching target material can be made closer to the vertical angle. In the shape obtained immediately after etching, if Pt, which is the etching target material, is exposed on the sidewall, the Pt is etched immediately upon overetching. When the deposited film is exposed, the deposited film is first etched at the time of overetching, and then Pt, which is the etching target material, is etched. Therefore, the over etching time can be shortened.

Next, a method for removing the deposit will be described.

As a method for removing the deposit, in addition to the wet treatment, a treatment using supercritical water or C02, or a dry treatment using an appropriate gas system may be considered. This dry treatment may be performed using the same treatment apparatus (same reaction vessel) as the etching treatment of Pt. In addition, the etching of a predetermined number of times and the etching of a different number of times may use the same etching apparatus (the same reaction container), or may use another etching apparatus (other reaction container).

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

As another method of the wet treatment, for example, a method of exposing ammonia, alcohol, hydrochloric acid, hydrogen peroxide solution, etc. to supercritical carbon dioxide can be exposed, whereby chloride attached to the sidewall can be removed.

Moreover, you may rinse before and after a removal process of a deposit, and put it into a drying process as needed. For example, when the wet process using a chemical liquid is performed as a method of removing a deposit, the washing process using pure water may be performed after that, and the drying process may be performed after that. When etching is performed in this way, there exists a point where the taper angle changes (in a sharp way) in the middle of the side wall of a mask or an etching target material. Or it becomes possible to provide the part in which the taper angle differs clearly in the middle of the side wall of a mask or an etching target material. In addition, 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 multichamber semiconductor device manufacturing apparatus, which 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. Have 907. The cassette 908 is placed in the stocker 907. When the wafer is processed in the processing chamber 901, the wafer 105 placed in the cassette 908 under approximately atmospheric pressure is transferred to the load lock chamber 904 under approximately atmospheric pressure by the loader 906 to close the load lock chamber. do. After the pressure of the load lock chamber 904 is reduced to an appropriate pressure, the wafer 105 is transferred to the processing chamber 901 by the wafer transfer robot 903 and etched to the middle. Thereafter, the wafer 105 is transferred to the deposit removal processing chamber 902 by the wafer transfer robot 903, and the deposit attached to the sidewall is removed. Next, the wafer 105 is again transferred to the etching processing chamber 901 'by the wafer transfer robot 903 and etched by a desired amount. Thereafter, the wafer 105 is transferred to the deposit removal processing chamber 902 'to remove deposits adhering to the sidewalls. The wafer 105 is then transferred to the unload lock chamber 905 by the wafer transfer robot 903. The pressure of the unload lock chamber 905 is raised to approximately atmospheric pressure, and then inserted into the cassette 908 by the loader 906.

Thus, Fig. 15A shows a wafer transfer apparatus 903, a plurality of processing chambers 901 and 901 'and a plurality of post-processing chambers 902 and 902' connected to the wafer transfer apparatus, and a plurality of lock chambers 904, 905 and a large base conveying apparatus 906 adjacent to the lock chamber, wherein the large base conveying apparatus is a semiconductor manufacturing apparatus connectable to the plurality of lock chambers and a wafer cassette 908 adjacent to the large substrate conveying apparatus. After the treatment material is etched in any one of the plurality of processing chambers, the post-treatment is performed in any one of the plurality of after-treatment chambers, and then etched in any one of the plurality of processing chambers, and then any one of the plurality of post-processing chambers Is to do post-processing.

In the example of FIG. 15A, a standby cassette is used, but a vacuum cassette may be used as in FIG. 15B. That is, Fig. 15B shows a wafer transfer apparatus 903, a plurality of processing chambers 901 and 901 'connected to the wafer transfer apparatus, a plurality of lock chambers 904 and 905, and a large base transfer apparatus adjacent to the lock chamber. 906, wherein the large base conveying apparatus is a semiconductor manufacturing apparatus connectable to the plurality of lock chambers, the post-processing chamber 902 adjacent to the large base conveying apparatus, and the wafer cassette 908, wherein the plurality of target materials are processed. After the etching in any one of the processing chambers, the post-treatment may be performed in the post-treatment chamber, and thereafter, the post-treatment may be performed in any one of the plurality of process chambers, and then post-treated in the post-treatment chamber.

In addition, although the deposit removal process is performed by the vacuum condition for description, you may carry out by atmospheric pressure conditions.

In the above example, although two etching treatments were performed using different etching treatment chambers 901 and 901 ', only the same treatment chamber 901 may be used multiple times. An advantage of using another processing chamber as the etching processing chamber is that, when etching the laminated film, it can be etched stably under different conditions for each film type. Etching and deposit removal can also be performed in the same chamber.

Next, using the method (c) shown in Figs. 14A to 14F described above, a method of etching a laminated film such as Pt / PZT / Pt, which is a memory portion of the ferroelectric memory, using a substantially tapered mask is shown in Fig. 16A. This will be described with reference to FIG. 16D. In this case, when the Pt / PZT / Pt films 61 to 63 shown in Fig. 16A are processed by one etching, deposition of deposits on the sidewalls of these layers 61 to 63 inevitably proceeds, and the shape shown in Fig. 16D. Becomes That is, the difference between the dimension of the mask 64 and the dimension of the to-be-etched material obtained becomes large. This dimension difference is an obstacle to miniaturization.

Therefore, immediately before etching the conductor (for example, Pt) film 61 located under the insulating film (PZT) 62, the etching is stopped to remove the deposit (FIG. 16B). Then, the taper angle of the PZT / Pt films 62 and 63 is φ3. After the etching is performed again, a shape as shown in Fig. 16C is obtained. In this case, the taper angle of the Pt film 61 is φ4 (where φ3 <φ4). Characteristically, although conductors (for example, Pt films 61 and 63) of the same material are formed above and below the insulating film (PZT) 62, these taper angles? 3 and? 4 are different. Of course, the taper angle φ 4 can be set larger than the taper angle φ 5 shown in FIG. 16D.

Thus, as shown in FIG. 16C by the 1st etching and the removal of the deposit immediately after that, the taper angle which consists of the insulating film (PZT) 62 and the conductor (for example, Pt) film 63 is a substantially taper mask of (phi) 3. Is obtained. By using such a substantial taper mask, the taper angle of the etching target material in the laminated film can be made to be close to the vertical angle.

Further, by using the method (c) shown in Figs. 14A to 14F described above or the method shown in Figs. 16A to 16C described above, the laminated film of magnetic random access memory (MRAM) expected as a next-generation memory device is substantially tapered. A method of etching using a mask having a shape 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 (e.g., Co) 76, an insulating film (e.g., Al 2 O 3) 75, a ferromagnetic material (e.g., Co) 74, and an anti-ferromagnetic material (e.g., FeMn) 73 from above. Base material (for example, Co and Si) (72, 71). In addition, 70 is the silicon oxide film 70, for example. In MRAM, it is required to etch these films 71 to 76 using one mask.

In this case, when, for example, adhesion of the reaction product of the FeMn film 73 is severe as compared with adhesion of other materials, the etching is stopped just before starting the etching of the FeMn film 73 to remove deposits (FIG. 17B). . In doing so, the taper angle of the films 74 to 76 is φ6. If etching is resumed after that, the FeMn film 73 can also be etched in a shape close to the vertical (FIG. 17C). At this time, the taper angle of the FeMn film 73 is φ7 where φ6 <φ7. Thus, as shown in FIG. 17C by the first etching and immediately after deposit removal and the second etching and immediately after deposit removal, a substantial taper mask having a taper angle changed in the films 73 to 76 is obtained. Obtained. By using such substantial taper masks 73 to 77, the paper angles φ8 of the material to be etched 71 and 72 can be made to be close to the vertical angle in the laminated film such as MRAM (here, φ6 < φ7 <φ8).

Moreover, what can be considered as a ferromagnetic material is mainly Fe, Co, Ni, Mn, or its compound, and all of them are known as a non-etching material. In the figure, 77 is a mask.

In the above example, a method of studying a mask shape or a substantially tapered mask shape has been described in order to make the sidewall of the etching target material substantially vertical. However, the present invention described below changes the sidewall of the etching target material by changing etching conditions. This can be done vertically.

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

Until now, etching has been performed under conditions where deposits are hard to adhere to the walls of the vacuum vessel (104 in FIG. 3). However, in order to reduce the deposition of the deposit, it is effective to lower the concentration of the reaction product in the vacuum vessel. Under conditions where deposits do not adhere to the walls of the vacuum vessel, in order to reduce the concentration of the reaction product in the gas phase, the only option is to exhaust the reaction product in the gas phase out of the vacuum vessel or to attach it to the sidewall of the mask or etching target material. none. Therefore, in reality, the concentration of the reaction product in the gas phase is maintained under the condition that the deposit does not adhere to the wall of the vacuum vessel.

However, in FIG. 3, by lowering the impedance of the load 115 to reduce the current flowing through the electrostatic coupling antenna 118, the reaction product can be easily attached to the wall of the vacuum vessel 104. At this time, since the concentration of the reaction product in the gas phase is reduced by adhering to the wall of the vacuum vessel, the amount of the reaction product incident on the wafer from the gas phase is reduced.

As a result, deposition of deposits on the sidewalls of the mask and the etched material is reduced, so that even when the sidewall is used with a mask of approximately 90 degrees, the shape of the sidewall of the etched material close to vertical is obtained.

However, when deposits adhere to the walls of the vacuum vessel, the state of the plasma changes or causes the generation of particles. Therefore, the deposits need to be removed periodically. Therefore, for example, each time one or more wafers are finished, a deposit removal process (that is, a process such as increasing the current flowing through the electrostatic coupling antenna 118) is performed.

At this time, by making the temperature of the wafer support (sample stand) 109 higher than at the time of etching, the deposit may not be attached to the wafer support 109 so that the deposit can be quickly exhausted out of the vacuum vessel 104. Or conversely, by lowering the temperature of the wafer support 109 and actively depositing the deposit on the support or wafers on the support so that the deposits are not reflected from the support or wafers on the support, the deposits again adhere to the walls of the vacuum vessel. It may be prevented from accelerating to accelerate the evacuation of the deposit.

According to the present invention, the etching of the sidewalls close to vertical is obtained by using a tapered mask or the like in the etching of a material in which the sidewalls are not vertically processed. Thus, a highly functional semiconductor device or a highly integrated semiconductor device can be obtained. You can write

Claims (24)

delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete At least Fe, Co, Mn, Ni, Pt, Ru, RuO ₂ , Ta, Ir, IrO ₂ , Os, Pd, Au, Ti, TiO _x , SrRuO ₃ , (La, Sr) CoO ₃ , Cu (Ba, Sr) TiO ₃ , SrTiO ₃ , BaTiO ₃ , SrTa ₂ O ₆ , Sr ₂ Ta ₂ O ₇ , ZnO, Al ₂ O ₃ , ZrO ₂ , HfO ₂ , Ta ₂ O ₅ , Pb (Zr, Ti) O ₃ , Pb (Zr, Ti) Nb ₂ O ₈ , (Pb, La) (Zr, Ti) O ₃ , PbTiNbO _x , SrBi ₂ Ta ₂ O ₉ , SrBi ₂ , (Ta, Nb) ₂ O ₉ , Bi ₄ Ti ₃ O ₁₂ , BiSiO _x , Bi _4-x La _x Ti ₃ O ₁₂ , In the etching method of the egg etching material which etches this film using a plasma using the hard-mask which consists of a film of the egg etching material containing GaAs and InTi, and the silicon oxide or metal formed on it, The taper (θ) angle with respect to the surface of the substrate at the portion in contact with the film of the hard mask sidewall is tanφ = (re-rd) / ((rd-re × cosθ) × sinθ), where φ is the taper of the hard etching material. Etch the film by a gas containing at least chlorine using a hard mask of less than 90 degrees given by the angle, re is the etching rate of the egg etch material, rd is the deposition rate of the reaction product on the sidewall of the egg etch material). And the taper angle (phi) with respect to the surface of the said board | substrate of the said film after etching is made more than the taper angle (phi) of the said hard mask. The method of claim 22, The hard mask made of silicon oxide or metal contains at least one of silicon oxide, silicon nitride, titanium, titanium nitride, titanium oxide, and alumina. The method of claim 22, The taper (θ) angle with respect to the surface of the substrate in a portion in contact with the film on the sidewall of the hard mask is tanφ = (re-rd) / ((rd-re × cosθ) × sinθ), where φ is a hard etching material. A combination of dry etching and wet etching forming the hard mask to be less than 90 degrees given by the taper angle, re is the etching rate of the hard etching material, and rd is the deposition rate of the reaction product on the sidewall of the hard etching material). Etching the film by at least a gas containing chlorine using the hard mask.

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