JPH0828347B2 - Micro processing method - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a fine processing method applied to a dry etching apparatus utilizing electron cyclotron resonance (hereinafter referred to as “ECR etching apparatus”).

[Conventional technology]

FIG. 2 is a schematic configuration diagram showing a conventional ECR etching apparatus. As shown in the figure, a stage 3 for mounting and holding a semiconductor wafer 2 is provided in a cylindrical first reaction chamber 1.
Is arranged. In addition, a second reaction chamber 4 is formed continuously above the first reaction chamber 1. A gas introduction pipe 5 is inserted into the second reaction chamber 4, and the gas introduction pipe 5
The reaction gas can flow into the second reaction chamber 4 via the. Further, a quartz window 6a is formed at a position above the second reaction chamber 4, and a waveguide 6 is connected to the quartz window 6a so that the second window 6a is connected via the waveguide 6 and the quartz window 6a. A microwave having a predetermined frequency is introduced into the reaction chamber 4. further,
A coil 7 is provided on the outer peripheral portion of the second reaction chamber 4, and a magnetic field having a predetermined magnetic flux density is applied in a direction perpendicular to the surface of the semiconductor wafer 2 mounted on the stage 3. Thus, in the second reaction chamber 4, electron cyclotron resonance (EC
R) Condition is satisfied and high density gas plasma is generated.

Further, an exhaust port 8a is formed below the first reaction chamber 1,
The first and second reaction chambers are connected to a vacuum pump (not shown) via an exhaust pipe 8 connected to the exhaust port 8a.
The insides of the first and fourth reaction chambers 1 and 4 are evacuated to a vacuum, and the first and second reaction chambers 1 and 4 are kept vacuum-tight.

In the ECR etching apparatus, in order to perform the etching process on the semiconductor wafer 2, first, the first and second reaction chambers 1 and 4 are evacuated. Subsequently, while exhausting gas, the reaction gas is flown into the second reaction chamber 4 through the gas introduction pipe 5 at a predetermined flow rate to set a predetermined pressure, and
A magnetic field and a microwave are applied in the second reaction chamber 4 to generate gas plasma. Then, the gas plasma generated in the second reaction chamber 4 in this manner is moved to the first direction along the lines of magnetic force.
To the reaction chamber 1 of the semiconductor wafer 2 by this plasma.
Is etched.

[Problems to be Solved by the Invention]

Here, let us consider the movement of gas plasma, that is, chlorine ion Cl ⁺ , when chlorine gas Cl ₂ is introduced as a reaction gas and the etching treatment is performed as described above. FIG. 3 is a schematic diagram showing the movement. In the figure, 10 is a plasma region formed as described above, and chlorine ions Cl ⁺ are present in this plasma region 10. The magnitude of the vector shown in the figure indicates the magnitude of the energy of chlorine ion Cl ⁺ ,
The direction of the vector indicates the direction of motion of the chlorine ion Cl ⁺ . As can be seen from the figure, the chlorine ion Cl ⁺ has a relatively large energy and moves randomly.

In the figure, 11 is a sheath region, and a sheath electric field E is generated in the sheath region 11 in a direction perpendicular to the surface of the semiconductor wafer 2 as is well known in the art. Therefore, when chlorine ion Cl ⁺ reaches this sheath region 11,
Under the influence of the sheath electric field E, it advances into the sheath region 11,
The moving direction of the chlorine ion Cl ⁺ within the sheath region 11 is determined by the vector sum of the vector of the ion Cl ⁺ and the sheath electric field E. Therefore, the chlorine ion Cl ⁺ whose movement direction when moving from the plasma region 10 to the sheath region 11 is substantially perpendicular to the surface of the semiconductor wafer 2
Enters the semiconductor wafer 2 vertically. Further, the even movement direction in a case not perpendicular to the surface of the semiconductor wafer 2, if sufficiently larger than the energy magnitude of the sheath electric field E has a chlorine ion Cl ^+, the chlorine ions Cl ⁺ is It moves substantially along the sheath electric field E. Therefore, etching with strong anisotropy can be performed only with chlorine ions Cl ⁺ satisfying the above conditions.

However, in reality, the chlorine ions Cl ⁺ move in a disordered manner as described above, so that there are only a few chlorine ions Cl ⁺ moving in the same direction as the sheath electric field E direction. In addition, since the energy of chlorine ion Cl ⁺ is considerably larger than the magnitude of the sheath electric field E, the chlorine ion Cl ⁺ which reaches the surface of the semiconductor wafer 2 as shown in FIG. The rate of vertical incidence on the surface is limited to a certain limit, and etching with sufficient anisotropy cannot be performed.

The present invention has been made to solve the above problems, and an object of the present invention is to provide a fine processing method capable of performing etching with stronger anisotropy.

[Means for solving the problem]

According to the microfabrication method of the present invention, a halogen-containing gas is flown into a reaction chamber that has been evacuated, and a microwave and a magnetic field are applied to the reaction chamber to form a plasma by electron cyclotron resonance. A microfabrication method of etching the semiconductor wafer with halogen reactive active species flowing out of the plasma along the sheath electric field only by the action of the sheath electric field formed between the halogen and the halogen contributing to the etching treatment. The mass is smaller than that of the reactive species, and the additive gas stable in the plasma state is mixed with the halogen-containing gas so as to flow into the reaction chamber.
As the additive gas, He, H2, N2, and Ne are used alone or as a mixture selectively.

[Action]

In this invention, in forming plasma by electron cyclotron resonance, the mass is smaller than the halogen reactive species contributing to the etching process, and the additive gas stable in the plasma state, that is, He, H2, N2, Ne alone, Alternatively, since the selectively mixed mixture is made to flow into the reaction chamber while being mixed with the halogen-containing gas, the plasma region to be generated is constituted by the halogen-reactive active species and the gas plasma of the additive gas. Therefore, the energy of the halogen reactive species in the plasma region can be suppressed low. As a result, the halogen-reactive active species are incident on the surface of the semiconductor wafer substantially along the sheath electric field generated near the surface of the semiconductor wafer, and the highly anisotropic etching process is performed.

〔Example〕

The microfabrication method according to the present invention is the EC shown in FIG.
Applicable to R etching equipment. Since we have already mentioned the configuration of the ECR etching system,
The description is omitted here.

Next, an embodiment of a fine processing method according to the present invention will be described with reference to FIGS. 1 and 2. In this example, first, chlorine gas Cl ₂ is prepared as a reaction gas, and helium gas He having a smaller mass than chlorine Cl and being stable even in a plasma state is prepared as an additive gas. In addition to chlorine gas Cl ₂ as reaction gas, H
A gas of F, HCl, HBr, HI, F ₂ , Br ₂ or I ₂ may be used. Further, a mixed gas in which an appropriate gas such as HF gas and chlorine gas Cl ₂ is mixed may be used. On the other hand, as an additive gas, H ₂ , N ₂ instead of helium gas He
Alternatively, Ne gas may be used. Further, a mixed gas obtained by mixing an appropriate gas among those gases such as H ₂ and helium gas He may be used. However, the additive gas must have a smaller mass than the halogen-reactive active species of the reaction gas and must be stable in the plasma state for the reason described below. In short, the reaction gas and additive gas can be appropriately selected as long as they satisfy these conditions.

Then, using a gas mixer (not shown), chlorine gas Cl
₂ (reaction gas) and He gas (additive gas) are mixed at an appropriate ratio to generate a mixed gas (Cl ₂ + He).

On the other hand, in parallel with the generation of the mixed gas (Cl ₂ + He),
The first and second reaction chambers 1 and 4 are evacuated. Subsequently, while exhausting gas, the mixed gas (Cl ₂ + He) is flown into the second reaction chamber 4 at a predetermined flow rate through the gas introduction pipe 5 to set a predetermined pressure, and the second reaction chamber A magnetic field and a microwave are applied to the inside of 4 to generate gas plasma.

FIG. 1 is a diagram schematically showing the movement of the gas plasma formed as described above. Also in this figure, as described above, the direction of the vector indicates the moving direction of each ion, and the magnitude thereof indicates the magnitude of energy possessed by each ion. As can be seen by comparing FIGS. 1 and 3, the energy of chlorine ions Cl ⁺ in the plasma region 10 of this embodiment is considerably smaller than that of the conventional example.

Now let's think about the reason. As is well known in the art, when a plurality of ions having different masses exist in the plasma region, the energy of each ion is proportional to the reciprocal of each mass. Therefore, as described above, in the plasma region 10, chlorine ions Cl ⁺ and helium ions H
In the presence of e ⁺ , the energy of the helium ion He ⁺ is relatively large, whereas that of the chlorine ion Cl ⁺ is kept quite low. In other words, chlorine ion Cl ⁺
If a part of the energy is absorbed by the helium ions He ⁺ which is formed as described above, the chloride ion Cl ⁺ only conventional case (the plasma region 10 is present: 3
The energy of chlorine ion Cl ⁺ is lower than that of (Fig.).

Chlorine ion Cl whose energy is suppressed low in this way
^{When +} enters into the sheath region 11, even if the moving direction of the chlorine ion Cl ⁺ does not match that of the sheath electric field E,
The vector sum of the chlorine ions Cl ⁺ and the sheath electric field E is close to the vector of the sheath electric field E. That is,
The chlorine ions Cl ⁺ are guided to the surface of the semiconductor wafer 2 substantially along the sheath electric field E and are incident on the semiconductor wafer 2 substantially vertically. As a result, the chlorine ions Cl ⁺ etch the semiconductor wafer 2 with a stronger anisotropy than in the conventional case.

In the above example, chlorine gas Cl ₂ was used as the reaction gas.
In addition, although the case where helium gas He is selected as the additive gas is taken up and explained, the halogen and the halogen gas are selected for the same reason even when the reaction and the additive gas are selected with an appropriate combination satisfying the predetermined conditions as described above. It is possible to keep the energy of reactive species low.
A highly anisotropic etching process is possible.

Further, in the above embodiment, the mixed gas (Cl ₂
+ He) is generated and the mixed gas thereof is allowed to flow into the second reaction chamber 4, but both the reaction gas and the added gas are simultaneously flowed into the second reaction chamber 4, or the gas introduction pipe 5 Alternatively, the reaction gas may flow into the second reaction chamber 4 via the gas and then the additional gas may further flow in, or vice versa.

〔The invention's effect〕

As described above, according to the present invention, the mass is smaller than that of the halogen reactive species that contribute to the etching process, and the additive gas that is stable in the plasma state, that is, He and H
Since 2, N2, and Ne are used alone or selectively mixed with the halogen-containing gas while flowing into the reaction chamber, the energy of the halogen-reactive species in the generated plasma region must be suppressed. You can as a result,
Only by the action of the sheath electric field, the halogen-reactive active species can be made to enter the surface of the semiconductor wafer substantially vertically along the sheath electric field, and etching treatment with higher anisotropy can be performed.

[Brief description of drawings]

FIG. 1 is an explanatory view for explaining a fine processing method according to the present invention, and FIG. 2 is an ECR to which the fine processing method can be applied.
FIG. 3 is a configuration diagram of an etching apparatus, and FIG. 3 is an explanatory diagram for explaining a conventional fine processing method. In the figure, 1 is a first reaction chamber, 2 is a semiconductor wafer, 4
Is the second reaction chamber. In the drawings, the same reference numerals indicate the same or corresponding parts.

Continuation of the front page (56) Reference JP-A 64-47028 (JP, A) JP-A 2-299227 (JP, A) JP-A 3-162592 (JP, A) JP-A 1-183822 (JP , A)

Claims (1)

[Claims] 1. A microwave and a magnetic field are applied to the reaction chamber while flowing a halogen-containing gas into the reaction chamber which is evacuated to form plasma by electron cyclotron resonance, and the plasma is formed between the plasma and the semiconductor wafer. In the microfabrication method of etching the semiconductor wafer with the halogen reactive active species flowing out of the plasma along the sheath electric field only by the action of the formed sheath electric field, the mass of the halogen reactive active species contributing to the etching treatment is higher than that of the halogen reactive active species. Is small, and the additive gas that is stable in the plasma state is mixed with the halogen-containing gas and flows into the reaction chamber, and as the additive gas, He, H2, N2, and Ne are individually or selectively mixed. A microfabrication method characterized by being used.