JPH0666294B2 - Dry etching method - Google Patents

Description

The present invention relates to a dry etching method, and more particularly to SiO ₂ on Si.
The present invention relates to a dry etching method suitable for etching a film.

[Conventional technology]

As the LSI becomes more and more miniaturized, the film thickness becomes thinner and the aspect ratio (aspect ratio) of the etching shape becomes larger, resulting in a deep groove shape. Began to be requested.

Conventionally, etching of insulating films such as SiO ₂ , PSG and Si ₃ N ₄ contains CF-based gas containing a large amount of C component such as C ₃ F ₈ or H such as CHF ₃ as an etching gas. The CF-based gas is used to cause CF-based deposition during etching to suppress the etching of the underlying Si, and H and F
The active species that etch Si are reduced by promoting the reaction of radicals, and the selectivity with respect to the underlying Si is increased.

In addition, related to this kind of method, Peter H.
"Dry Etching of SiO ₂ and Si ₃ N ₄ ", Semiconductor International, (May 1986), pp. 98-163 (Peter H. Singer; Dry Etching of SiO ₂ an)
d Si ₃ N ₄ ,, SEMICONDUCTOR INTERNATIONAL, (MAY−198
6), PP98-163.

[Problems to be solved by the invention]

The above-mentioned prior art does not consider cleanliness in the processing chamber. When a CF-based gas containing a large amount of C component is used, CF-based deposition occurs and suppresses etching of the underlying Si. At the same time, there has been a problem that deposition occurs around the electrodes and grows as the number of times of etching increases, causing dust and changing the discharge state.

When a CF-based gas containing H is used, the selectivity is improved by deposition, and the active species that etch Si are reduced by promoting the reaction between H and F radicals to improve the selectivity. Deposition has the same problem as described above, and further, there is a problem that the impact of H ions causes crystal defects on the Si surface and the damage of the device is increased.

An object of the present invention is to provide a dry etching method capable of cleaning the inside of a processing chamber, having low damage, and having excellent selectivity between an insulating film and a base Si.

[Means for solving problems]

The purpose of the above is to generate a gas plasma in a processing chamber in which an etching gas is introduced and decompressed to a predetermined pressure, and Si on Si
In the dry etching method of etching the O ₂ film,
The first step of etching using a mixed gas of CF-based gas and H ₂ gas as the etching gas, and the second step of etching using the CF-based gas containing a large amount of C component as the etching gas are performed separately. This will be achieved.

[Action]

In etching using a mixed gas of CF-based gas and H ₂ gas in the first step, by the action of H ₂ mixed gas, the reaction retirement the deposition film deposited on the peripheral electrode by the second step of the previous etching However, the CF-based gas promotes the etching of the target insulating film, the process is performed before the underlying Si appears, and the subsequent steps including over-etching are performed by the CF-based gas containing a large amount of C component in the second step. CF
A deposition film of the system is generated to improve the selectivity with respect to the underlying Si, and etching with less damage is performed.

〔Example〕

An embodiment of the present invention will be described below with reference to FIGS. 1 to 4.

FIG. 1 shows an example of an etching apparatus for carrying out the dry etching method of the present invention. A lower electrode 2 and an upper electrode 8 are provided facing each other in a chamber 1 which is a processing chamber, an exhaust port 6 connected to an exhaust device (not shown) is provided at the bottom of the chamber 1, and an emission spectrum is provided at the side of the chamber. A total of 10 are attached.

The lower electrode 2 is attached to the chamber 1 via an insulating material 4, and is connected to a high frequency power source 5. Reference numeral 3 is a cooling water passage provided in the lower electrode 2, and 7 is a wafer placed on the lower electrode 2.

The upper electrode 8 is attached to the chamber 1 via an insulating material 9 and is grounded to the ground potential. A gas introduction path is provided in the upper electrode 8, and the valves 11a to 11c and the flow rate controller 12 are provided.
Gas sources 13a to 13c are connected via a to 12c, respectively. In this case, C ₂ F _{6 is used} for the gas source 13a, H ₂ is used for the gas source 13b, and C ₃ F ₈ is used for the gas source 13c.

The output from the emission spectrometer 10 is sent to a control device (not shown), and the valves 11a to 11c and the flow rate control valves 12a to 12c are controlled to be opened and closed by the control device.

A dry etching method using the etching apparatus having the above configuration will be described.

The chamber 1 is evacuated from the exhaust port 6 and is supplied with an etching gas from any of the gas sources 13a to 13c, and high frequency power is applied between the lower electrode 2 and the upper electrode 8 to generate gas plasma. Occur. The wafer 7 placed on the lower electrode 2 is etched by this gas plasma, and the light emission during etching is collected by the emission spectrometer 10 to convert the light intensity into a voltage value and input to the control device.
The etching state is checked to control the etching apparatus.

At this time, as shown in FIG. 2 (a), the wafer 7 has an insulating film, in this case, an SiO ₂ film 15 formed on a Si substrate 14, and a photoresist 16 formed on the upper surface. Has become. This is shown in FIG. 2 (b) in the first stage etching 17.
As shown in FIG. 2, the etching is performed until the SiO ₂ film 15 is almost completely etched.
As shown in FIG. 3, the etching operation is performed in two steps of over-etching for completely etching the SiO ₂ film 15.

In the etching work, as shown in Table 1, the kind of etching gas is changed for each of the first and second steps. A CF-based gas with a small amount of transition, such as C ₂ F ₆ and H ₂ , is used as a mixture, and a CF-based gas with a large C component, such as C ₃ F _8, is used for the second-stage etching.

To switch the etching gas for the first and second stage etching, the time until the completion of the first stage etching shown in FIG. 2 (b) is measured in advance, and the required time is input to the control device. After a predetermined time has passed from the start of etching, open the valve 11c shown in FIG.
The control device controls the closing of the valves 11a and 11b. The pressure conditions at this time may be the same.

In the subsequent second-stage etching, the end point of the etching process is controlled by detecting the etching end point using the emission spectrometer 10.

At this time, in the first-stage etching, the SiO ₂ film 15 was etched at a high speed by the C ₂ F ₆ gas plasma, and at the same time, as shown in FIG. 3, it occurred in the second-stage etching in the previous etching process. The CF system deposition around the electrode is effectively cleaned by the radical reaction in H ₂ gas plasma. Regarding the selection ratio between the photoresist 16 and the SiO ₂ film 15 in this first stage etching,
The influence of H ₂ is small, and high values can be obtained as in the conventional process. In addition, since C ₃ F ₈ gas containing a large amount of C component is used in the second-stage etching, the underlying Si substrate 14 and SiO ₂
A high selection ratio with the film 15 is obtained, and since H is not contained unlike the conventional CHF ₃ gas, the device is not damaged.

In the first-stage etching, when the ratio of the H ₂ gas flow rate Q _{H2 to} the total flow rate (QT = Q _C2F6 + Q _H2 ) (where Q _C2F6 is the flow rate of C ₂ F ₆ gas) is increased, As shown in FIG. 4, the etching rate of the SiO ₂ film decreases. This tendency is that the ratio of H ₂ gas flow rate is
It becomes sharp at 50% or more. From this, it is desirable that the proportion of H ₂ gas be 50% or less. Further, the lower limit of the proportion of H ₂ gas can be determined from the etching characteristics of the deposition around the electrode, and as shown in FIG. 4, the proportion of H ₂ gas is 10%.
In the following, the etching rate sharply decreases. From this, it is desirable that the lower limit ratio of H ₂ gas be 10% or more.

As described above, according to this embodiment, the etching is divided into two stages,
By using the mixed gas of H ₂ and CF-based gas as the first-stage etching and the CF-based gas with a large amount of C component as the second-stage etching, the SiO ₂ film is etched to adhere to the electrode periphery in the previous etching. was with the deposition removed by etching of the first step can etch the SiO ₂ film, etching of the SiO ₂ film is high selection ratio to the Si substrate without damage in the etching of the second step can be performed.

Although C ₂ F ₆ , C ₃ F ₈ and H ₂ gas are supplied from the same nozzle in this embodiment, an etching gas for an oxide film such as C ₂ F ₆ or C ₃ F ₈ is supplied to the vicinity of the wafer. It may be supplied from the periphery of the lower electrode and separately supplied so that only the H ₂ gas flows from the upper electrode. In this case, it is possible to effectively clean the periphery of the upper electrode, which has a large rate of deposition that occurs during the second-stage etching. Further, if the etching gas is supplied from the lower surface of the wafer, the thermal resistance between the wafer and the electrodes is reduced, and the cooling effect is improved.

In addition, the gas mixture with H ₂ used for the first-stage etching
As the CF-based gas, CF ₄ can be used in addition to C ₂ F ₆ . In addition to C ₃ F ₈ , C ₄ F ₈ can be used as the CF-based gas containing a large amount of C component used for the second-stage etching.

Further, as the control for switching from the first stage to the second stage etching, in addition to the method of temporal control, an emission spectrometer is used to detect and control the beginning of a change from a stable state during etching. You may do it.

In addition, the SiO ₂ film has been described as an example of the insulating film during the implementation of the present embodiment, but other insulating films such as PSG and Si ₃ N ₄ can also exhibit the same effect.

Further, in the present embodiment, the cathode coupling type etching apparatus is taken as an example, but the present invention can be applied to an arc coupling type etching apparatus, a magnetron etching apparatus using a magnetic field, a u-wave plasma etching apparatus and the like.

〔The invention's effect〕

According to the present invention, there is an effect that the inside of the processing chamber can be cleaned, and etching with low damage and excellent selectivity between the insulating film and the underlying Si can be performed.

[Brief description of drawings]

FIG. 1 is a vertical cross-sectional view of an etching apparatus for showing a dry etching method according to an embodiment of the present invention, and FIG. 2 is a detailed cross-sectional view of a wafer when the dry etching method of the present invention is used for etching. FIG. 3 is a flow chart showing the steps of the dry etching method of the present invention, and FIG. 4 is a diagram showing the relationship between the mixed gas used in the first-stage etching of the dry etching method of the present invention and the etching rate. 1 ... Chamber, 2 ... Lower electrode, 5 ... High frequency power supply,
6 ... Exhaust port, 7 ... Wafer, 8 ... Upper electrode, 11a to 11c ... Valve, 12a to 12c ... Flow controller, 13a
To 13c …… Gas source, 14 …… Si substrate, 15 …… SiO ₂ film, 1
6 ... Photoresist, 17 ... First stage etching, 18 ...
… Second stage etching

Claims (1)

[Claims] 1. A dry etching method of etching a SiO ₂ film on a Si substrate by generating a gas plasma in a processing chamber in which an etching gas is introduced and decompressed to a predetermined pressure, and a CF having less deposition in the etching gas. With system gas
A dry etching method characterized by performing a first step of etching using a mixed gas of H ₂ gas and a second step of etching using a CF-based gas having a large C component as the etching gas.