JP2695822B2 - Plasma etching method - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a plasma etching method, and more particularly to a plasma etching method suitable for plasma etching a sample such as a semiconductor element substrate by changing an etching shape at an intermediate stage. It is about the method.

[Conventional technology]

In the case where the sample needs to be changed in an intermediate stage when performing plasma etching on the sample, for example, vertical etching is performed in a second step after taper etching in a first step.

It should be noted that related methods of this type include, for example, JP-A-57-137473 and JP-A-58-197820.

[Problems to be solved by the invention]

In the above-described conventional technology, the etching shape is changed in the middle of the process by performing different steps in a batch. That is, for example, the discharge is stopped when the taper etching is completed, and thereafter, for example, vertical etching is performed by using another etching apparatus or changing the condition by the same etching apparatus. For this reason, there is a problem that the time required for the etching process of the sample which needs to change the etching shape in the middle stage increases, and the throughput decreases.

It is an object of the present invention to provide a plasma etching method capable of shortening the time required for etching processing of a sample which needs to change an etching shape at an intermediate stage and improving throughput.

[Means for solving the problem]

The above object is to perform plasma generation and bias application to a sample independently, convert a mixed gas of an etching gas and a shape control gas into a plasma by discharging, and without stopping the discharge during etching of the sample by the plasma. This is achieved by adjusting the high-frequency power for applying a bias to change the energy acting when the sample is etched by the plasma to change the etching shape.

[Action]

A sample whose etching shape needs to be changed at an intermediate stage is carried into the etching chamber of the etching apparatus, and is set on the sample stage. On the other hand, an etching gas and a shape control gas are respectively introduced at predetermined flow rates into the etching chamber, and the inside of the etching chamber is evacuated to a predetermined pressure. In this state, a discharge is generated in the etching chamber, whereby the etching gas and the shape control gas in the etching chamber are turned into plasma. This plasma performs etching up to the middle stage of the sample.
When the etching has progressed to an intermediate stage, the subsequent etching shape is changed without stopping the discharge.
That is, by changing the energy acting on the sample when the sample is etched by the plasma without stopping the discharge during the etching of the sample, the etching shape can be changed. In addition, since the plasma generation and the bias application are performed independently, the adjustment of the high-frequency power does not affect the plasma generation, that is, the discharge state. That is, even if the high-frequency power is adjusted, the discharge state does not change and is stable. Therefore, it is possible to continuously perform favorable etching of a required etching shape, and it is possible to shorten the processing time and improve the throughput.

〔Example〕

 Hereinafter, an embodiment of the present invention will be described with reference to FIG.

FIG. 1 shows a relationship between a gas mixture ratio introduced into an etching chamber (not shown) of an etching apparatus and a taper angle (θ). Here, chlorine (Cl ₂ ) is an etching gas, and chloroform (CHCl ₃ ) is a shape control gas. As a sample (not shown), for example, a wiring film is laminated on a substrate. Here, the substrate is SiO ₂ , P
It is an insulating material such as SG, and the wiring film is aluminum. In this case, the wiring film is etched. In this case, the taper angle (θ) is an angle in which the side wall of the groove formed in the wiring film by etching is used as the substrate surface. In this case, the gas pressure in the etching chamber (hereinafter, abbreviated as etching pressure) is 10 mTorr, and in this case, the gas is turned into plasma by discharge using a magnetic field microwave.

In FIG. 1, when the gas mixture ratio is 10%, the taper angle (θ)
Is about 90 degrees, that is, vertical etching. When the gas mixture ratio becomes 10% or more, the taper angle (θ) decreases accordingly. When the gas mixture ratio is 10% or less, isotropic etching occurs. For example, when the gas mixture ratio is 25%, the taper angle (θ) is approximately 78 degrees, and when the gas mixture ratio is 40%, the taper angle (θ) is approximately 72 degrees.
Degree. That is, by setting the gas mixture ratio to 10% or more, the etching stops the discharge and shifts from vertical etching to taper etching without adjusting the conditions, and conversely, the gas mixture ratio is changed from 10% or more to 10%. %, It shifts from taper etching to vertical etching. For example, a groove having a side wall having a taper angle (θ) of approximately 80 degrees from the surface of the wiring film to the middle in the depth direction, and then etching a groove having a side wall having a taper angle (θ) of approximately 90 degrees to the substrate surface If processing is necessary, the gas mixture is first adjusted to about 22%. Next, the gas having such a gas mixture ratio is turned into plasma by electric discharge in the etching chamber. Etching of the wiring film is started by this plasma, and a groove having a side wall having a taper angle (θ) of approximately 80 degrees is etched from the surface of the wiring film to halfway in the depth direction. Thereafter, the gas mixture ratio is changed and adjusted to about 10%. During this time and thereafter, the discharge is not stopped,
Therefore, the gas having such a gas mixture ratio is continuously turned into plasma. With this plasma, the wiring film is continuously etched from the middle in the depth direction to the base medium surface.
A groove having 90 degree side walls is etched. When the etching to the substrate surface is completed, the discharge is stopped and the etching process of the sample is completed. Thereby, the wiring film has a side wall having a taper angle (θ) of approximately 80 degrees from the surface to the depth direction and the middle in the thickness direction, and a taper angle (θ) from the middle in the depth direction to the substrate surface. ) Is formed with a groove having a side wall of approximately 90 degrees. In addition, isotropic etching is performed halfway at a gas mixture ratio that causes isotropic etching when the gas mixture ratio is 10% or less, and then, for example, vertical etching is performed at a gas mixture ratio of about 10% to change the groove shape. be able to.

In this embodiment, since the etching of the sample whose etching shape needs to be changed at an intermediate stage can be continuously performed, the time required for the etching processing of the sample can be shortened and the throughput can be improved. In recent years, as the integration degree of LSI elements has increased, the element wiring width has become narrower and has reached the sub-micron region. However, since the wiring film thickness is required to be substantially the same as the conventional one, the wiring film thickness has been reduced. And the width of the wiring tends to increase, and the distance between the wirings is becoming smaller. When the ratio of the thickness to the width of the wiring film is large and the distance between the wirings is small, if the taper etching is performed, the lower dimension of the wiring film increases, and it is difficult to secure an insulation distance between adjacent wirings. However, according to the present embodiment, the etching shape can be made in consideration of the relationship between the thickness and width ratio of the wiring film and the wiring interval. Therefore, the insulation distance between adjacent wirings can be secured, and the electrical characteristics of the LSI element can be well maintained. In addition, it is possible to obtain a shape that does not hinder the step of depositing the insulating film after the wiring film etching process, thereby improving the productivity of the LSI element. As the etching device, a plasma etching device such as a parallel plate type reactive plasma etching device, a magnetic field type microwave plasma etching device, or a non-magnetic type microwave plasma etching device is used.

FIG. 2 illustrates another embodiment of the present invention, and shows the relationship between high-frequency power and taper angle (θ). Here, the high-frequency power governs the bias potential of the sample (not shown), that is, the energy acting on the sample at the time of etching the sample. If the sample is not an insulator, either AC or DC can be used.) For example,
When a microwave plasma etching apparatus is used as an etching apparatus, high-frequency power is applied to a sample stage on which a sample is placed, and when a parallel plate type reactive plasma etching apparatus is used, high-frequency power is applied to an electrode serving as a cathode. Is applied. As the sample, the same sample as in the above-described embodiment is used. An etching gas and a shape control gas are introduced into an etching chamber (not shown) of the etching apparatus. In this case, chlorine (Cl ₂ ) is used as the etching gas, and the shape control gas is used as the shape control gas.
Chloroform (CHCl ₃ ) is used. In this case, the gas mixture ratio, that is, the ratio of the flow rate of chloroform to the sum of the flow rate of chlorine and the flow rate of chloroform introduced into the etching chamber is 25%, and the etching pressure is 10 mTorr.
Is constant.

In FIG. 2, when the high frequency power is about 60 W, the taper angle (θ) is approximately 90 degrees, that is, vertical etching is performed. When the high frequency power becomes about 60 W or more, the taper angle (θ) becomes smaller accordingly. For example, when the high frequency power is 90 W, the angle is approximately 78 degrees, and when the high frequency power is 120 W, the angle is approximately 71 degrees. When the high frequency power is 60 W or less, isotropic etching occurs. In other words, by setting the high-frequency power to about 60 W or more, the etching stops the discharge and shifts from vertical etching to aper etching without adjusting the conditions, and conversely, the high-frequency power is reduced from about 60 W or more to about 60 W or more. By setting the power to 60 W, the mode shifts from taper etching to vertical etching. For example, a groove having a side wall having a taper angle (θ) of approximately 80 degrees from the surface of the wiring film to the middle in the depth direction, and then etching a groove having a side wall having a taper angle (θ) of approximately 90 degrees to the substrate surface If processing is necessary, first the RF power is adjusted to about 82W. The gas having the above gas mixture ratio is turned into plasma by electric discharge in the etching chamber, and the etching of the wiring film is started by this plasma. In the wiring film, a groove having a side wall having a taper angle (θ) of approximately 80 degrees is etched from the surface to a point in the depth direction. When the etching proceeds to a predetermined depth, the high frequency power is adjusted to about 60W. During this period and thereafter, the discharge is not stopped, and the wiring film is continuously etched from the middle of the depth direction to the substrate surface by the plasma, whereby the taper angle (θ) is approximately 90 degrees from the middle of the depth direction to the substrate surface. The groove having the side wall is etched. When the etching to the substrate surface is completed, the discharge is stopped and the etching process of the sample is completed. As a result, the wiring film has a side wall having a taper angle (θ) of approximately 80 degrees from the surface to the middle in the depth direction in the thickness direction, and a taper angle (θ) from the middle in the depth direction to the substrate surface. ) Is formed with a groove having a side wall of approximately 90 degrees. Note that high-frequency power is 60 W or less, isotropic etching is performed halfway with high-frequency power that causes isotropic etching, and then, for example, high-frequency power is reduced to 60 W
Vertical etching to change the groove shape.

In this embodiment, the same effects as those of the above-described embodiment can be obtained. In the case of using an etching apparatus such as a magnetic field type microwave plasma etching apparatus or a non-magnetic field type microwave plasma etching apparatus which can perform plasma generation and bias application independently, adjustment of high frequency power is performed. This does not affect the plasma generation, that is, the discharge state, that is, the discharge state can be stably maintained without fluctuation even if the high frequency power is adjusted. Therefore, even if the high-frequency power is adjusted, the etching can be performed immediately and satisfactorily, and the throughput can be further improved. Also, in this embodiment, the adjusting operation is simpler than in the above-mentioned one embodiment in which the gas mixture ratio is adjusted.
It is easy and the operability of the etching process can be further improved. By adjusting the etching pressure during the etching in addition to the above embodiment, the same effect as that of the above embodiment can be obtained. That is, at a certain etching pressure, the taper angle (θ) becomes minimum,
In particular, as the etching pressure is increased, the taper angle (θ)
Becomes larger. Further, by adjusting the temperature of the sample during the etching, the same effects as those of the other embodiments can be obtained. That is, as the temperature of the sample increases, the taper angle (θ) decreases accordingly. Further, in the case of microwave plasma etching, by adjusting the microwave power during the etching, the same effect as the above-described embodiment can be obtained. That is, the taper angle (θ) increases as the microwave power decreases.

〔The invention's effect〕

According to the present invention, it is possible to continuously perform etching of a sample whose etching shape needs to be changed at an intermediate stage, so that the time required for etching the sample can be shortened and the throughput can be improved.

[Brief description of the drawings]

FIG. 1 is a relationship diagram between a gas mixture ratio and a taper angle in one embodiment of the present invention, and FIG. 2 is a relationship diagram between a high-frequency power and a taper angle in another embodiment of the present invention.

Claims (1)

(57) [Claims] 1. A method according to claim 1, wherein the plasma generation and the bias application to the sample are performed independently, a mixed gas of the etching gas and the shape control gas is turned into plasma by discharge, and the discharge is stopped during the etching of the sample by the plasma. A plasma etching method characterized by changing the energy acting when the sample is etched by the plasma by adjusting the high-frequency power for applying the bias, thereby changing the etching shape.