JP3083898B2 - Dry etching method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a dry etching method used in, for example, a semiconductor device manufacturing process.

[0002]

2. Description of the Related Art Conventionally, as a dry etching method, a method of generating a plasma of a halogen-based gas in a processing chamber and performing etching by utilizing the action of ions, radicals, electrons, and the like in the plasma is known as plasma etching. Have been.

In such an etching method, many proposals have been made to improve the etching selectivity while improving the etching rate.

For example, as a method of increasing the etching rate when etching silicon (Si) and silicon oxide (SiO ₂ ) and reducing the etching rate of a photoresist, CHF is used as an etching gas.
_A method of performing etching while controlling the substrate temperature to zero degree or less using a carbon fluoride gas such as ₃ has already been proposed. This method is very useful when it is desired to simultaneously etch the Si film or Si substrate and the SiO ₂ film.

Further, the etching rate of Si is improved,
In addition, as a method of reducing the etching rate of SiO ₂ and photoresist, there has been proposed a method of performing etching while controlling the substrate temperature at −100 to 130 ° C. using SF ₆ as an etching gas (Monthly Semicondac).
tor World 1988, 1, P58). This method is very useful when only the Si film or the Si substrate is to be etched without etching the SiO ₂ film.

[0006]

However, for example, in a manufacturing process of a semiconductor device, for example, there is a case where only SiO ₂ is etched, and Si or a photoresist is not required to be etched.

FIG. 4A is a schematic cross-sectional view showing an example of a thin film structure formed on a semiconductor wafer, and is a diagram for explaining an example of such a case.

In the figure, 52 is a Si substrate and 54 is a Si substrate.
Diffusion layers formed in the substrate 52, 56 is SiO ₂ layer formed on the Si substrate 52, 58 is a polysilicon line formed on the SiO ₂ layer in (Poly-Si), 60 is a photoresist layer is there.

FIG. 4 shows a state in which a contact hole 62 is formed by performing an etching process on such a semiconductor wafer.
(B). As described above, when etching is performed until the surface of the Poly-Si wiring 58 and the surface of the diffusion layer 54 are exposed, the amount of etching required to expose the surface of the Poly-Si wiring 58 is small, and the surface of the diffusion layer 54 is small. The amount of etching required for exposing is large. Therefore, in order to simultaneously form these contact holes 62 in one etching in a short time, the etching rate for Poly-Si becomes very slow.
To make the etching rate for O ₂ very fast,
Etching must be performed.

Conventionally, the selectivity (ratio of etching rate) of SiO _{2 to} Poly-Si has been limited to about 13. That is, even when the selectivity is the highest, the SiO ₂
Poly-Si was etched at a speed about one-third of the above.

The present invention has been made in view of the problems of the related art, and is a dry etching method that improves the etching rate of, for example, SiO ₂ and hardly etches Si or photoresist. , The etching rate is high, and the S
An object of the present invention is to provide a dry etching method excellent in selectivity to i and photoresist.

[0012]

According to one aspect of the present invention, there is provided a dry etching method in which at least a part of an etching gas in a region facing an object to be processed is turned into plasma, and the object to be processed is etched by the plasma. in the etching method, the a predetermined temperature the temperature below zero degrees of the object at the time of etching, as flop Razumagasu,
Use a mixed gas containing CO gas and halogen-based gas .
The ratio of the CO gas to the halogen-based gas is
At least one of SiO ₂ , BPSG,
_{SiN, SiON, Ta 2 O 5} , TiO 2 or TiN
The etching target layer is etched. Ma
The underlying layer of the layer to be etched may be a polysilicon layer.
Or a silicon layer.

[0013]

The temperature of the object to be processed at the time of etching is set to zero degree or less.
Speed up the etching rate of the film to be etched
In addition to the etching gas
do itA mixed gas containing a CO gas and a halogen-based gas,
The ratio of CO gas to halogen gas is 1 or more
And SiO _Two , BPSG, SiN, SiON, Ta
_Two O _Five , TiO _Two Or etch TiN layer to be etched
AndEtch Si and photoresist
Suppress.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, as an embodiment of the present invention, a case where the dry etching method of the present invention is applied to etching using a magnetron plasma etching apparatus will be described as an example.

FIG. 1 is a sectional view schematically showing a configuration of a magnetron plasma etching apparatus according to this embodiment.

The wafer 10 to be processed is mounted and fixed on the upper surface of the first susceptor 12. As a method for mounting and fixing, for example, an electrostatic chuck (not shown) method can be used. In this method, the wafer 10 is sucked and fixed by Coulomb force. The first susceptor 12 is detachably fixed to an upper surface of the second susceptor 14. The reason why the susceptor is divided into two is that only the upper first susceptor 12 needs to be replaced when the susceptor is contaminated, thereby facilitating maintenance.

The side and bottom surfaces of the first susceptor 12 and the second susceptor 14 are covered with an insulating ceramic 16. On the lower surface of the insulating ceramic 16, a liquid nitrogen storage unit 20 as a cooling unit is provided. The bottom surface of the inner wall of the liquid nitrogen storage section 20 is formed, for example, in a porous manner so that nucleate boiling can occur.
Can be maintained.

A chamber for forming a reaction chamber is formed of an upper chamber 30 and a lower chamber 32. The lower chamber 32 contains the first susceptor 12.
Has a bottomed cylindrical portion that exposes only the wafer mounting surface of the above into the chamber chamber and covers other portions. That is, the first and second susceptors 12, 14, the insulating ceramic 1
6, a side wall 32a that covers a side surface of the liquid nitrogen storage unit 20,
And a support wall 32b. On the other hand, the upper chamber 30 is formed in a cylindrical shape so as to cover the periphery of the side wall 32 a of the lower chamber 32, and the lower end thereof is connected and fixed to the lower chamber 32. Further, the upper chamber 30 has a surface 30 a facing the upper surface of the first susceptor 12. The etching gas is introduced by a mechanism (not shown) through an etching gas inlet 30b provided on the surface 30a.

The inside of the reaction chamber constituted by the upper chamber 30 and the lower chamber 32 can be evacuated by a pipe 34.

As shown in FIG. 1, the second susceptor 14, the insulating ceramic 16, and the liquid nitrogen accommodating section 20 are each provided with a through hole, and a pipe 36 is disposed in the through hole. ing. A cooling gas (for example, H ₂ gas or the like) having a predetermined pressure is introduced into the pipe 36, thereby cooling the first susceptor 12, and lowering the temperature of the wafer 10 to zero degree or less through the first susceptor 12. Can be controlled to a predetermined temperature. A gas inlet (not shown) is provided in the first susceptor 12, and the gas inlet causes fine irregularities on the back surface of the wafer 10 from the joint surface between the wafer 10 and the first susceptor 12. The introduction into the gap can also prevent the occurrence of temperature unevenness in the wafer 10 due to minute irregularities on the back surface of the wafer 10.

In the magnetron etching apparatus of the present embodiment, the surface 30a of the upper chamber 30 functions as a cathode electrode, and the surface of the first susceptor 12 functions as an anode electrode. doing. And
An etching gas is introduced while the inside of the chamber is evacuated, and plasma is generated between the opposed electrodes by the etching gas. As described above, in this embodiment, since the surface 30a of the upper chamber 30 is used as an anode electrode, the configuration of the apparatus can be simplified, and further, a permanent magnet 38 described later is disposed outside the upper chamber 30. Can be arranged. Further, by disposing the permanent magnet 38 outside the upper chamber 30 in this manner, the volume of the reaction chamber can be reduced, so that the load on a vacuum pump (not shown) connected to the pipe 34 is reduced. Alternatively, the time required for evacuation can be reduced.

In the magnetron etching apparatus of this embodiment, a rotating magnetic field can be formed between the surface 30a of the upper chamber 30 and the first susceptor 12 by rotating the permanent magnet 38. Permanent magnet 38
The formation of a magnetic field between the surface 30a of the upper chamber 30 and the first susceptor 12 due to the electric field generated between the surface 30a of the upper chamber 30 and the first susceptor 12 and the electric field orthogonal to the electric field This is because, due to the action with the magnetic field component, the cycloidal motion of the electrons is performed in a direction orthogonal to each other according to Fleming's left-hand rule, thereby increasing the frequency of collision between the electrons and gas molecules.

As an etching gas introduced into the chamber from the etching gas inlet 30b, a mixed gas of a gas containing at least carbon (C) and oxygen (O) having an oxidation number of less than 4 and a halogen-based gas is used. However, in this embodiment, at least carbon (C) and oxygen (O) having an oxidation number of less than 4 are used.
Is used as a gas containing carbon monoxide (CO) gas, and CHF ₃ gas is used as a halogen-based gas.

The mixing ratio of these two gases is
It is necessary to determine the mixing ratio in consideration of the influence on the etching rate and the selection ratio. For example, in the case of the dry etching method according to the present embodiment, when the ratio of the CO gas to the CHF ₃ gas is increased, the selectivity increases in proportion to the increase, and the etching rate decreases. According to the study by the semi-inventor, the ratio of the CO gas to the CHF ₃ gas is desirably set to “1” or more in order to secure a sufficient etching rate and selectivity.

FIG. 2 is a graph showing the measurement results of the etching rate when etching is performed by using the etching gas with the magnetron plasma etching apparatus shown in FIG. 1 using such an etching gas. In the figure, the vertical axis represents the etching rate, but the etching rates of BPSG (SiO ₂ doped with phosphorus (P) and boron (B)) and SiO ₂ are on the left, and the etching of Poly-Si and photoresist is shown on the left. The speed is shown on the right. The horizontal axis is the surface temperature of the wafer 10.
Table 1 shows the etching conditions at this time.

[Table 1] As can be seen from FIG. 2, by setting the surface temperature of the wafer 10 to zero degree or less, the etching rate of SiO ₂ could be dramatically improved. At this time, Poly-S
The etching rate of i and the photoresist also increases, but S
The etching rate was very slow as compared with the etching rate of iO ₂ , and a sufficient selectivity was obtained. For example, the selectivity in the conventional etching method is limited to about 13 as described above, whereas the etching method of this embodiment is
When the temperature of 0 is −50 ° C., the selectivity is about 45.

It is to be noted that a very good result can be obtained with respect to the anisotropy of the etching, and the microloading effect (the effect of decreasing the etching depth by reducing the etching diameter) was hardly observed.

FIG. 3 is a graph showing the results of etching using the above-described etching gas while changing the RF power. As described above, by performing the etching by increasing the RF power, the etching rate can be further improved.

As described above, according to this embodiment,
A magnetron plasma etching apparatus was used as an etching apparatus, and the wafer 10 was controlled at a temperature of zero degree or less, and CHF ₃ gas and CO 2 were used as etching gases.
By using the mixed gas of the gas, the etching rate of SiO ₂ is faster, better selectivity to Si or photoresist of the SiO ₂ etching, and, little plasma etching anisotropy good micro-loading effect Was realized.

The present invention is not limited to the above embodiment, and various modifications can be made within the scope of the present invention.

For example, in the magnetron plasma etching apparatus of this embodiment, the surface 30a of the upper chamber 30 is used as a cathode electrode, and the permanent magnet 38 is arranged outside the upper chamber 30. A configuration in which a cathode electrode and a magnetic field generator are arranged may be adopted.

In this embodiment, a mixed gas of CHF ₃ gas and CO gas is used as an etching gas.
The effect of the present invention can be obtained as long as it is a mixed gas of a gas containing at least C and O having an oxidation number of less than 4 and a halogen-based gas.

For example, at least C and O having an oxidation number of less than 4
As the gas containing, in addition to CO gas, COOH gas,
HCHO gas, CH ₃ COOH gas, CH ₃ OH gas and the like can be mentioned.

As the halogen-based gas, for example, a fluorine-based gas such as CHF ₃ , CBrF ₃ , SF ₆ ,
NF _3, F _2, etc. may also be used. In addition, chlorine (Cl), bromine (B
r) or a gas containing iodine (I) or the like.

In addition, in this embodiment, the case where the SiO ₂ film and the BPSG film are etched by the dry etching method of the present invention has been described.
Similar effects can be obtained in etching of a SiON film or a film in which these are laminated. Furthermore, Ta
The same effect can be obtained in etching of a ₂ O ₅ film, a TiO ₂ film, a TiN film and the like.

[0035]

As described above in detail, according to the present invention, it is possible to provide a dry etching method in which the etching rate is high and the selectivity of the film to be etched to Si or photoresist is excellent.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view of a magnetron plasma etching apparatus used in an embodiment of a dry etching method according to the present invention.

FIG. 2 is a graph showing measurement results of an etching rate when etching is performed by the magnetron plasma etching apparatus shown in FIG. 1 using the dry etching method according to the present invention.

3 is a graph showing measurement results of an etching rate when etching is performed by the magnetron plasma etching apparatus shown in FIG. 1 using the dry etching method according to the present invention.

FIGS. 4A and 4B are diagrams for explaining a conventional dry etching method.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Wafer 12,14 Susceptor 20 Cooling part (liquid nitrogen storage part) 30 Upper chamber 30a Upper surface of upper chamber 30b Etching gas inlet 32 Lower chamber 34,36 Piping 38 Permanent magnet

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor, Yukihiro Hasegawa 1 Kosuka Toshiba-cho, Saiwai-ku, Kawasaki-shi, Kanagawa Prefecture Within Toshiba Research Institute, Inc. No. 1 Toshiba Research Institute, Inc. (56) References JP-A-63-161620 (JP, A) JP-A-1-200627 (JP, A) JP-A-57-49236 (JP, A) JP-A-3 -276626 (JP, A) JP-A-56-111229 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H01L 21/3065

Claims (2)

(57) [Claims] 1. A dry etching method in which at least a part of an etching gas in a region facing an object to be processed is turned into plasma, and the plasma is used to etch the object, wherein the temperature of the object at the time of etching is zero degrees or less. and the predetermined temperature, the flop Razumagasu, using <br/> mixed gas containing a CO gas and a halogen gas, and, with respect to the halogen-containing gas
By setting the ratio of the CO gas to 1 or more, SiO ₂ , BPSG, SiN, SiO 2
N, dry etching method characterized by etching the Ta ₂ O _5, TiO ₂ or etched layer of TiN <br/>. 2. The method according to claim 1, wherein the underlayer of the layer to be etched is a polysilicon layer or
A dry etching method characterized by being a silicon layer .