JPH02130822A - Method for plasma etching - Google Patents

Abstract

PURPOSE:To prevent the protection film of an etching sidewall from thinning and perform etching vertically by keeping the temperature during etching approximately constant. CONSTITUTION:A refrigerant supplying apparatus 60 supplies refrigerant to cool a sample 40 mounted on the sample mounting surface of an electrode 31 when no plasma is generated, or when etching is not yet performed. The other refrigerant supplying apparatus 61 supplies the other refrigerant required to keep the temperature of the sample 40 during etching. The refrigerant supplying apparatus 61 is connected to a controller 70. The amount of supply of the refrigerant required to keep the sample 40 mounted on the electrode 31 and etched with plasma at about a specific temperature during etching is set and stored beforehand in the controller 70 and a control signal is sent to the refrigerant supplying apparatus 61, depending upon the stored amount.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a plasma etching method, and is particularly suitable for etching samples such as conductive element substrates (hereinafter referred to as wafers) using plasma. This invention relates to a plasma etching method.

[Conventional technology]

When etching a sample such as a wafer using plasma, for example, in order to prevent thermal deterioration of the resist on the wafer, a The sample is cooled via the sample stage.

[IIJ to be solved by the invention] The 2i degree temperature of the sample placed on the sample stand and cooled through the sample stand increases due to the action of radiant heat from the plasma, reaction heat, etc. as etching progresses. Become. However, in the above-mentioned conventional technology, there is no recognition or consideration given to suppressing the temperature rise of the sample accompanying the progress of dripping. Therefore, for example, in a technique in which a daposit gas is added to the etching gas to form a protective film in the etching gas and the etching is performed almost vertically, the thickness of the protective film on the wall increases as the temperature of the sample increases. The thickness gradually becomes thinner, and as a result, the etched shape tends to become a reverse taper shape when etching is completed.

SUMMARY OF THE INVENTION An object of the present invention is to provide a plasma etching method that allows a sample to be etched into a vertical shape.

[Means to solve the problem]

The above objects include a plasma etching method in which a sample placed on a sample stage is etched using plasma, and the temperature of the sample stage is controlled so that the temperature of the sample can be maintained at a substantially constant temperature during etching of the sample. This is achieved by having the following steps.

[For production]

A sample is placed on the sample stage, and the sample is etched using plasma. The concentration of the sample tends to increase as knee pumping progresses. Therefore, the temperature of the sample stage is controlled so as to be maintained at a substantially constant temperature during etching of the sample. As a result, for example, in a technique in which a deposition gas is added to the etching gas to form a protective film on the etching side wall and the etching is performed substantially vertically, the thickness of the protective film on the etching side wall is prevented from becoming thinner.
The etched shape at the end of etching is a vertical shape.

〔Example〕

An embodiment of the present invention will be described below with reference to FIG.

In FIG. 1, a counter electrode #M2o and a sample electrode I are provided in the processing chamber 10 to face each other in the vertical direction.

The counter electrode field is composed of an electrode 21 and an electrode shaft 4. The electrode shaft n projects its lower part into the processing chamber 10,
In addition, the upper part of the processing chamber 10 is protruded outside the processing chamber 10.
It is installed on the top wall of 0. The electrode 4 is provided substantially horizontally at the lower end of the electrode axis n. The electrode unit is grounded via an electrode shaft 4. The sample electrode Wita is electric 1i31 and electrode axis! It is made up of.

The electrode shaft n has an upper portion protruding into the processing chamber 10 and a lower portion protruding outside the processing chamber 10 so that the electrode shaft n protrudes into the processing chamber 10 .
installed on the bottom wall of the The 11L pole 31 is provided substantially horizontally at the upper end of the electrode shaft support. In this case, electric wi31
serves as a sample stage, and has a sample installation surface on the surface facing the electric wire w121. In this case, the size of the sample installation surface is such that only one sample ω can be placed thereon.

In FIG. 1, a gas dispersion path and a gas discharge hole are formed inside the electric ff121. The gas release hole is
It is open toward 131. Electrode n and electrode axis n
A gas supply path 5 is formed inside the gas distribution path in communication with the gas distribution path. The gas supply device is installed outside the processing chamber IO. One end of the gas supply pipe 51 is connected to the gas supply device group, and the other end communicates with the gas supply path 3 and is connected to the electrode shaft B. The gas supply pipe 51 is provided with a gas flow rate control device (not shown) and an on-off valve (not shown).

In FIG. 1, a refrigerant flow path and other refrigerant flow paths are formed inside the electric cylinder 31. In this case, the refrigerant flow path field and the other refrigerant flow path U are out of communication. Electric W131
And inside the electrode shaft, there is a refrigerant supply path and another refrigerant supply $36. A refrigerant discharge passage T and another refrigerant discharge passageway are respectively formed.

The refrigerant supply path A is communicated with the refrigerant flow path through the inlet of the refrigerant flow path, and the refrigerant discharge path is communicated with the refrigerant flow path through the outlet of the refrigerant flow path.

The other refrigerant supply path A is connected to the other refrigerant flow path through the inlet thereof, and the other refrigerant discharge path is connected to the other refrigerant flow path U through the outlet thereof. is communicated with.

In this case, the refrigerant supply device ω and the other refrigerant supply *1t61 are each installed outside the processing chamber IO. The coolant supply pipe axis mark has the function of supplying the coolant necessary to cool the sample set on the sample installation surface of the electrode 31 to a predetermined temperature in a state where plasma is not generated, that is, when it is not etched. The other coolant supply device ω has the function of supplying another coolant necessary to maintain the temperature of the sample chrysanthemum at a predetermined temperature during etching. One end of the refrigerant supply pipe shaft is the refrigerant supply *t
The other end is connected to the refrigerant supply path A and connected to the electrode metal ring. One end of the refrigerant supply pipe shaft is connected to the refrigerant discharge path a and is connected to the electrode shaft! The other end is connected to a refrigerant supply device θ. Other refrigerant supply pipe 6
One end of the refrigerant supply device 61 is connected to another refrigerant supply device 61, and the other end is connected to another refrigerant supply passageway and connected to the electrode shaft n. One end of the other refrigerant recovery pipe 6 communicates with another refrigerant discharge path and is connected to the electrode axis, and the other end is connected to another refrigerant supply device 61. The other refrigerant supply device 61 is connected to the control device. The control value W170 is set in the electrician 4131 and etched using plasma.
Another refrigerant supply lid is set in advance to correspond to the cooling rate of the electrode 31 necessary to maintain the temperature of the sample chamber substantially constant at a predetermined temperature during etching.

It has been implemented and other refrigerant supplies are based on this! j
It has a function of outputting a control signal to the Ii position 61.

In Figure WI1, a decompression exhaust system R80 is installed outside the processing chamber 10. One end of the exhaust pipe 81 communicates with the inside of the processing chamber 10 and is connected to the lower side wall of the processing chamber 10, and the other end is connected to the lower side wall of the processing chamber 10.
Connected to the intake port of the decompression exhaust device (equipment).

The exhaust pipe 81 is provided with a variable resistance valve (not shown) and an on-off valve (not shown).

In the IJI diagram, a power source for bias application, in this case a high frequency electric power N9o, is installed outside the processing chamber 10. The electric power source 31 is connected to a high frequency power source via an electrode shaft. Therefore, the bottom wall of the processing chamber 10 and the electrode axis! means electrical insulation material (
(not shown) is electrically insulated. The high frequency power source is grounded.

In the IF5 diagram, processing chamber 1 is
0 is evacuated under reduced pressure. Processing chamber 1 being evacuated under reduced pressure
Force is introduced into 0. In other words, by opening the on-off valve, the amount of gas supplied! Gas is supplied from gas supply pipe 51.1150. Gas supply path5. The gas passes sequentially through the gas distribution path Z and is emitted from the gas discharge hole toward the electric current tM3x. The amount of gas released, that is, the amount introduced into the processing chamber 10, is controlled to a predetermined amount by a gas flow rate control device.

A part of the gas introduced into the processing chamber 10 as described in step 2 is exhausted by the decompression exhaust device (equipment) by the action of the variable resistance valve, thereby adjusting the pressure inside the processing chamber 10 to a predetermined etching pressure. be done. On the other hand, one sample cut is carried into the processing chamber 10 by a known transport means (not shown), and the sample cut is placed on the sample installation surface of the electrode 31 with the surface to be etched facing upward.

Further, the refrigerant is supplied from the refrigerant supply device ω to the refrigerant supply pipe.

The refrigerant passes sequentially through the refrigerant supply passages and is supplied to the refrigerant channel fittings. The refrigerant supplied to the refrigerant flow path vanes passes through the refrigerant flow path vanes and then sequentially passes through the refrigerant discharge path n and the refrigerant recovery pipe group, and is recovered by the refrigerant supply device ω. As a result, the field 11 is cooled, and the sample shaft installed on the sample installation surface is cooled to a predetermined temperature.

For example, when the surface of the sample to be etched is a Po1y-8i film and the film is etched using a mixed gas of 8P6 and c2cJ3F3, the sample is cooled to 10 to 30°C. In this state, the high frequency power source is started to operate, and a high frequency wave of a predetermined power is applied to the electric wire via the electrode shaft 31. Thereby, the gas in the processing chamber 10 is turned into plasma. The surface to be etched of the sample cut, which is placed on the sample installation surface of the electrode 1131 and cooled to a predetermined temperature, is knee-etched using the plasma. In this state,
As etching progresses, plasma radiant heat and knee
The temperature of the sample chrysanthemum increases due to the heat of the etching reaction, and in some cases, the difference of 1 degree between before and after etching exceeds 50°C. Therefore, in order to prevent such a rise in temperature of the sample ψ, the other refrigerant is passed from the other refrigerant supply device 61 through the other refrigerant supply pipes and other refrigerant supply pipes to other refrigerant channel fittings. Supplied.

The other refrigerant supplied to the other refrigerant passage U flows through the other refrigerant passage U, and then flows through the other refrigerant discharge passage 38. The refrigerant passes sequentially through other refrigerant supply sections and is collected by another refrigerant supply device 61. In this case, the supply amount of the other coolant is set in advance to correspond to the cooling rate required to maintain the temperature of the sample specimen placed on the electrode 31 and etched using plasma at a predetermined concentration during etching.

The amount of other refrigerant supplied to other refrigerant passage devices is controlled by the control signal output from the embedded control device 170. As a result, the sample cut placed on the electrode m and to be etched using plasma is cooled at a cooling rate necessary to maintain the temperature of the sample cut approximately constant at a predetermined concentration during etching. For example, Po1y-3i film is mixed with SFs and C2C13.
When etching is performed using a mixed gas with F2, the cooling rate is 30 to 50°C/min. By the way, if etching between samples is completed in 1 minute under these conditions, the temperature of the electrode 31 at the end of etching will be approximately -20°C compared to the temperature of the electrode 31 of 20°C before the start of nibbuting. .

By cooling the electrode 31 during etching in this manner, the temperature of the sample φ during etching is maintained substantially constant at a predetermined temperature. After the etching between the samples is completed, the temperature of the electrode 31 is restored to the cooling temperature by the coolant from the coolant supply device ω. After the etching has been completed, the sample is transferred from the electric wire W131 to a known transport means and transported out of the processing chamber IO. Thereafter, a new sample is transported into the processing chamber IO by a known transport means.

The sample carried in is placed on the sample installation surface of the electrode 31 with an upward direction of the surface to be etched.

Thereafter, the above operation is performed again.

According to this embodiment, the following effects can be obtained.

(1) Since the concentration of the sample during etching can be maintained at a substantially constant temperature, the etched shape of the sample can be vertical.

(2) Adding a depositing mushroom gas to the etching gas,
Since the temperature of the sample to be etched during etching can be maintained substantially constant at a predetermined temperature while forming a protective film on the etching gas, thinning of the protective film on the etching sidewall can be prevented and the etching shape can be made vertical.

+31 Since the temperature during etching of a sample with a Poly-5i film etched using a mixed gas of SF6 and C2C1!3F3 can be maintained at 10 to 30°C, the etched shape of the Poly-8i film can be made into a vertical shape. .

In the above embodiment, two refrigerant supply devices are used: a refrigerant supply device and another refrigerant supply device, but one additional refrigerant supply device is used.
Only the refrigerant supply device may be used. In this case, the refrigerant supply device has two functions: one to supply the refrigerant necessary to cool the sample installed on the electrode to a predetermined temperature when no plasma is generated, that is, before etching, and one to cool the sample to a predetermined temperature during etching. A device that has the function of supplying the refrigerant necessary to maintain the temperature at a predetermined temperature is used. This refrigerant may be the same refrigerant or may be a different refrigerant. In this case, the control device controls the supply amount of refrigerant corresponding to the temperature of the electrode necessary to cool the sample to a predetermined temperature when not being etched, and the temperature of the sample installed on the electrode and being etched using plasma. The amount of refrigerant supplied necessary to maintain a substantially constant predetermined temperature is set in advance.

A device having a function of inputting the information and outputting a control signal to one refrigerant supply device based on these signals is used. In such a case, only one refrigerant supply device is required, as well as one set of refrigerant flow path, refrigerant supply/discharge path, and refrigerant supply/recovery pipe. The l1tR price can be reduced and its configuration can be simplified. Further, as the refrigerant supply device, one having a cold stage, such as a regenerator type refrigerator, is used. In this case, the cold stage can itself is used as the sample stage, or the sample stage is provided in a stacked manner with the cold stage can. In such a case, the above-mentioned temperature control of the sample, that is, the sample stage, is performed by controlling the flow lid and pressure of the working gas using a control device.

Note that, instead of maintaining the temperature of the sample during etching substantially constant as in the above embodiment, by controlling the temperature of the sample during etching so that it tends to decrease, the etching shape can be made into a forward tapered shape.

In this case, the control device is an i installed on the electrode (sample stage).
Supply of another coolant corresponding to the cooling rate of the electric current 41 (sample stage) that can adjust the temperature of the sample to be etched using plasma to a temperature such that the etched shape of the sample becomes a predetermined forward tapered shape. The amount is preset and input,
A refrigerant supply device having a function of outputting a control signal to other refrigerant supply devices based on this is used. Further, by combining such temperature control during sample etching with the temperature control during sample etching in the above embodiment, vertical etching and forward taper etching can be performed on the same sample or separate samples. Can be done.

Furthermore, in the above embodiment, an apparatus using a so-called high-frequency glow discharge type means as a plasma generating means was described, but in addition to this, a so-called non-magnetic microwave plasma generating means that generates plasma by the action of a microwave electric field is also available. Similar effects can be achieved with a device using a generation means, a so-called magnetic field microwave plasma generation means, a magnetron discharge type plasma generation means, etc., which generate plasma by the action of a microwave electric field and a magnetic field. In an apparatus that uses a non-magnetic field microwave plasma generation means or a magnetic field microwave plasma generation means, a DC power source or an AC (including high frequency) power source for bias potential control is connected to the sample stage on which the sample to be etched is placed. It also includes things that are.

Further, in the above embodiment, the sample is placed on the electrode to which high frequency is applied, but the sample may be placed on the grounded electrode.

〔Effect of the invention〕

According to the present invention, since the temperature of a sample etched using plasma can be maintained at a substantially constant temperature during etching, the etched shape of the sample can be made vertical.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the configuration of a plasma etching apparatus according to an embodiment of the present invention. 10...Processing chamber, 31...IE pole, Adjustment...Other refrigerant flow path, Ah...Other refrigerant supply path, holder... ...Other refrigerant discharge path, Xun...Sample, Father...Gas supply device, 61...Other refrigerant supply device, U...Other refrigerant Supply pipe, house...
...Other refrigerant recovery pipe, 70...Control device,
(Capital)・・・Decompression exhaust device, 匍・・・High frequency power supply

Claims (1)

[Claims] 1. A step of etching a sample placed on a sample stage using plasma, and a step of controlling the temperature of the sample stage so that the temperature of the sample during etching can be maintained at a substantially constant temperature. A plasma etching method comprising: 2. The plasma etching method according to claim 1, wherein the sample stage is cooled at a cooling rate that can maintain the concentration of the sample at a substantially constant temperature during etching. 3. Etch the sample Poly-Si using plasma of a mixed gas of SF_6 and C_2Cl_3F_3, and reduce the concentration of the sample to 10 to 30°C during the etching.
The plasma etching method according to claim 1, wherein the plasma etching method maintains the following.