JPH09129623A - Plasma etching - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a plasma etching method, which defeats a limit due to a conditional control of etching gas and can increase the selection ratio of a silicon oxide film to a silicon film, which is a base film, in an etching treatment of the silicon oxide film using plasma consisting of carbon fluoride gas. SOLUTION: A heat transfer medium chamber 30 is formed in the sidewall of a plasma generating chamber 10, wherein carbon fluoride gas introduced through a gas feeding device is brought into a plasma state by the action of a microwave electric field from a microwave oscillator and the action of a magnetic field generated by solenoid coils 13. When a sample 40 laminated with a silicon film and a silicon oxide film is subjected to etching treatment with the above plasma, a heat transfer medium is fed in the chamber 30 through a heat transfer medium feeding device. Thereby, the inner wall surface, which is exposed to the plasma, of the chamber 10 is warmed.

Description

Detailed Description of the Invention

[0001]

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 etching a sample in which a silicon film and a silicon oxide film are laminated by a plasma of carbon fluoride gas. Is.

[0002]

2. Description of the Related Art As a technique for selectively plasma etching a silicon oxide film of a sample, for example, Japanese Patent Application Laid-Open No.
5-164077, U.S. Pat. No. 4,162,185
Those described in the specification etc. are known.

For example, Japanese Patent Laid-Open No. 164077/55 discloses a method in which a silicon oxide film on a silicon substrate is gas plasma etched by a gas plasma etching apparatus.
It is described that a gas mixture of a hydrogen-containing fluorine compound gas and an oxidizing gas or a gas mixture of a fluorine compound gas, a hydrogen gas and an oxidizing gas is used as an etching gas.

Also, for example, US Pat. No. 4,162,185
In the specification, S with saturated and unsaturated halocarbons
In the selective etching of iO ₂ , the saturated halogenated carbon (for example, CF ₄ ) and the unsaturated halogenated carbon (including F such as C ₂ F ₄ , C ₃ F ₆ , and C ₃ F ₄ ) are mixed by the flow rate of SiO ₂ It is described that the etching rate ratio of / Si is controlled.

[0005]

The above prior art controls the composition and flow rate of etching gas (hereinafter referred to as etching gas condition) when selectively performing plasma etching on a sample silicon oxide film. However, such a conventional technique has a limit in further improving the selection ratio of the silicon oxide film, and it is difficult to control the etching gas conditions by only controlling the etching gas condition. The selection ratio of the oxide film cannot be further improved.

Further, in the above-mentioned conventional technique, the etching rate ratio between the silicon oxide film and the silicon film changes with an increase in the number of samples to be etched, that is, the selection ratio changes with time.

A first object of the present invention is to overcome the limit of the improvement of the selection ratio by controlling the etching gas conditions in the etching process of the silicon oxide film and further improve the selection ratio with respect to the silicon film which is the base film. It is to provide a plasma etching method.

A second object of the present invention is to provide a plasma etching method capable of suppressing a change with time in the selectivity with respect to a silicon film which is a base film in the etching process of a silicon oxide film.

[0009]

A first object of the present invention is to use a plasma etching method in which a carbon fluoride gas is used as an etching gas to convert the gas into plasma, and a silicon film and a silicon oxide film are laminated. Etching the silicon oxide film of the sample with the plasma,
And heating the member exposed to the plasma during the etching process.

The second object is to use a plasma etching method in which a carbon fluoride gas is used as an etching gas to convert the gas into plasma, and the silicon of a sample in which a silicon film and a silicon oxide film are laminated. This is achieved by a method including a step of etching the oxide film with the plasma and a step of adjusting the temperature of the member exposed to the plasma to a constant temperature during the etching treatment.

By the above method, the member exposed to the plasma of the fluorocarbon gas during the etching process of the silicon oxide film of the sample in which the silicon film and the silicon oxide film are laminated by the plasma of the fluorocarbon gas is used. A sample in which a silicon film and a silicon oxide film are laminated due to an increase in the ratio of the polymer present in the plasma due to a decrease in the adhesion of the plasma polymer such as CF ₂ to the member by heating. The amount of the plasma polymer deposited on the surface increases.

When such a plasma polymer is adhered to the silicon oxide film of the sample, oxygen as a reducing agent exists in the silicon oxide film, so that the plasma polymer is removed from the silicon oxide film by the reducing action of the oxygen. To be done. Therefore, the etching rate of the silicon oxide film does not decrease.

On the other hand, when such a plasma polymerized substance adheres to the silicon film of the sample, since the reducing agent does not exist in the silicon film, the removal of the plasma polymerized substance adhered to the silicon film is suppressed. Therefore, the etching rate of the silicon film is reduced.

As a result, the limit of improvement of the selection ratio by controlling the etching gas conditions can be overcome, and the selection ratio between the silicon oxide film and the silicon film as the base film is further improved.

Further, during the etching process of the silicon oxide film of the sample in which the silicon film and the silicon oxide film are laminated by the plasma of carbon fluoride gas, the temperature of the member exposed to the plasma of carbon fluoride gas is kept at a constant temperature. Since the amount is adjusted, the amount of the plasma polymerized substance adhered to the member becomes constant, the change in the etching rate ratio between the silicon oxide film and the silicon film which is the base film can be suppressed, and the change in the selection ratio with time can be prevented.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment of the present invention will be described below with reference to FIGS. FIG. 1 is a vertical sectional configuration diagram of a magnetic field plasma etching apparatus according to a first embodiment of the present invention. In FIG. 1, the etching apparatus includes a plasma generation chamber 10, a microwave introduction window 11 made of quartz provided in an opening of the plasma generation chamber 10, a microwave oscillator (not shown), and a microwave oscillated by the microwave oscillator. The waveguide 12, the solenoid coil 13, the sample stage 14, which is propagated toward the opening of the plasma generation chamber 10, a vacuum exhaust device (not shown) which evacuates the plasma generation chamber 10 under reduced pressure, and the etching gas in the plasma generation chamber 10. A gas supply device (not shown) for supplying carbon fluoride gas, in this case, a heat medium supply device (not shown) and a high frequency power supply 15 are provided.

In FIG. 1, an etching gas inlet of the plasma generating chamber 10 and a gas supply device are connected by a gas supply pipe 20. A heat medium chamber 30 is formed in the side wall of the plasma generating chamber 10 in this case. The heat medium supply port of the heat medium chamber 30 and the heat medium supply device correspond to the heat medium supply pipe 21.
Are connected by At the heat medium outlet of the heat medium chamber 30,
The heat medium discharge pipe 22 is connected.

In FIG. 1, the microwave having a frequency of 2.45 GHz oscillated from the microwave oscillator propagates through the waveguide 12, passes through the microwave introduction window 11, and is supplied to the plasma generation chamber 10. The etching gas is introduced from the gas supply device into the plasma generation chamber 10 through the gas supply pipe 20 and the etching gas inlet. Inside the plasma generation chamber 10,
It is evacuated by a vacuum exhaust device. The etching gas in the plasma generation chamber 10 is turned into plasma by the magnetic field generated by the solenoid coil 13 and the electric field of microwaves. The sample 40 in which the silicon film and the silicon oxide film are laminated is installed on the sample installation surface of the sample table 14 with the silicon oxide film surface as the upper surface, in this case, one sample 40 is formed by ions and neutral molecules or atoms in the plasma. The etching process proceeds. Further, the incident energy of ions is independently controlled by applying high frequency power to the sample table 15. Further, in the heat medium chamber 30, a heat medium of a predetermined temperature is supplied from a heat medium supply device via a heat medium supply pipe 21 and a heat medium supply port via a heat medium discharge pipe 22 from the heat medium supply port. Is discharged. As a result, the inner wall surface of the plasma generation chamber 10 exposed to the plasma is heated.

FIG. 2 shows the plasma generation chamber 10 when the silicon oxide film of the sample 40 is etched using CHF ₃ (gas flow rate 50 cc / min), which is one kind of carbon fluoride gas, as the etching gas. The influence of the temperature of the inner wall surface on the selection ratio with the silicon film was investigated, and the vertical axis was set to 1.0 with respect to the silicon film when the temperature of the inner wall surface of the plasma generation chamber 10 was 20 ° C. In this case, the relative value of the selection ratio (hereinafter, abbreviated as relative selection ratio) is shown. The other etching conditions at this time are as follows: microwave power 1 kW, etching pressure 10 mTorr, high frequency power 2
00W, the temperature of the cooling water supplied to the sample stage is 20 ° C.

As can be seen from FIG. 2, the plasma generation chamber 1
By increasing the temperature of the inner wall surface of 0, the relative selectivity is improved. For example, when the temperature of the inner wall surface of the plasma generation chamber 10 is 40 ° C., the relative selectivity is about 1.7 times, and when the temperature of the inner wall surface of the plasma generation chamber 10 is 60 ° C., the relative selectivity ratio is about 2.
It tripled. That is, by heating the inner wall surface of the plasma generation chamber 10, the adhesion of the plasma polymer such as CF ₂ to the inner wall surface of the generation chamber 10 decreases, so that the proportion of the polymer present in the plasma increases. Therefore, the amount of the plasma polymerized material attached to the sample 40 increases. When such a plasma polymerized substance adheres to the silicon oxide film of the sample 40,
Since oxygen that is a reducing agent is present in the silicon oxide film,
The plasma polymer is removed from the silicon oxide film by the reducing action of the oxygen. Therefore, the etching rate of the silicon oxide film does not decrease. On the other hand, when such a plasma polymerized product adheres to the silicon film of the sample 40, since the reducing agent does not exist in the silicon film, the removal of the plasma polymerized product adhered to the silicon film is suppressed. Therefore, the etching rate of the silicon film is reduced. As a result,
The selection ratio between the silicon oxide film and the silicon film that is the base film is improved. The relative selectivity increases as the temperature of the plasma generation chamber 10 increases, but the improvement tends to be saturated when the temperature of the inner wall surface of the plasma generation chamber 10 is about 200 ° C.

In this embodiment, the following effects can be obtained. (1) It is a base film that can overcome the limitation due to the control of etching gas conditions in the etching treatment by the carbon fluoride gas plasma generated by the action of the magnetic field and the microwave electric field of the sample in which the silicon film and the silicon oxide film are laminated. The selection ratio with respect to the silicon film can be further improved.

(2) Plasma polymerization on the inner wall surface of the plasma generation chamber in the etching treatment by the carbon fluoride gas plasma generated by the action of the magnetic field and the microwave electric field of the sample in which the silicon film and the silicon oxide film are laminated. Since the adhesion of the substance can be suppressed, it is possible to suppress the generation of dust due to the plasma polymer adhered to the inner wall surface of the plasma generation chamber coming off from the inner wall surface, and to prevent the yield of the sample from decreasing due to the dust.

In the first embodiment, only the inner wall surface of the plasma generating chamber exposed to the plasma is heated. However, for example, a machine is used for mounting the sample on the sample mounting surface of the sample table. When a conventional clamp means is used, the clamp means is also exposed to the plasma, and therefore, from the viewpoint of improving the relative selectivity, it is preferable to heat the clamp means as well. That is, from the viewpoint of improving the relative selectivity, it is preferable to heat the member exposed to the plasma (the member to which the plasma polymer can be attached, excluding the sample). Further, in the first embodiment, the sample is placed in the plasma generation chamber, but in addition to this, the plasma generated in the plasma generation chamber is transferred to the outside of the plasma generation chamber and the sample is etched by the plasma. The sample may be arranged. In any case, by heating the member exposed to the plasma, the same action as that in the first embodiment is produced, and the relative selectivity is improved. Further, in the first embodiment, the carbon fluoride gas is turned into plasma by the action of the magnetic field and the microwave electric field, and the silicon oxide film of the sample in which the silicon film and the silicon oxide film are laminated is etched by the plasma. Although the case has been described as an example, the present invention can be similarly applied to the case where the above sample is etched by using a parallel plate type plasma etching apparatus. In this case, the inner wall surface of the processing chamber, the electrodes provided inside the processing chamber, and the like are members exposed to plasma. However, in this case, the etching pressure is 1 as compared with the case where the plasma is generated by the action of the magnetic field and the microwave electric field in the first embodiment.
Since it is about an order of magnitude higher (relationship between the flow rate of the etching gas introduced into the plasma generating chamber and the outgas amount), the remarkable effect as in the first embodiment cannot be obtained. Further, in the above-described first embodiment, a carbon fluoride gas is used as an etching gas, and a sample in which a silicon film and a silicon oxide film are laminated is used as a sample. In this case, the plasma polymer adhered to the silicon oxide film is removed from the silicon oxide film by the oxygen reducing action of the silicon oxide film, while the plasma polymer adhered to the silicon film does not cause such an action, so that it is removed from the silicon film. Not removed. That is, any sample can be effectively applied as long as it is a sample in which a film containing a component capable of removing the plasma polymerized product even if the plasma polymerized product adheres and a film that cannot remove the adhered plasma polymerized product are laminated.

Next, a second embodiment of the present invention will be described with reference to FIGS.
This will be described below. FIG. 3 is a vertical sectional configuration diagram of a magnetic field plasma etching apparatus according to the second embodiment of the present invention. FIG.
The difference from the magnetic field plasma etching apparatus of the first embodiment of the present invention shown in FIG. 1 is that the heat medium supply device 50 has a function of changing the temperature of the heat medium, and Terminal 51 for detecting temperature and heat medium supply device 50
Is the point where the heat medium temperature control device 52 connected to each is provided. It is to be noted that, in FIG. 3, the same devices and the like as those in FIG.

In FIG. 3, as in the case of the first embodiment, the etching gas in the plasma generation chamber 10 is turned into plasma by the action of the magnetic field and the microwave electric field. The sample 40 placed on the sample table 14 is etched by the plasma. The inner wall surface of the plasma generation chamber 10 is heated by a heat medium and the temperature is adjusted.
That is, the temperature of the inner wall surface of the plasma generation chamber 10 changes during the etching process of the sample 40, and when the sample 40 is continuously etched one by one, the plasma generation chamber 10
The temperature of the inner wall surface of the changes. As described above, when the temperature of the inner wall surface of the plasma generation chamber 10 changes, the amount of the adhered plasma polymerized substance on the inner wall surface changes, and accordingly, the silicon oxide film of the sample 40 and the silicon film as the base film are changed. The etching rate ratio changes and the selection ratio changes. Therefore, the temperature of the inner wall surface of the plasma generation chamber 10 is detected by the temperature detection terminal 51, and the detected value is the heat medium temperature control device 52.
Is input to In the heat medium temperature control device 52, the temperature, which is the temperature of the inner wall surface of the plasma generation chamber 10 and should be kept constant, is compared with the detected value, and the temperature of the heat medium is set by the comparison result. The set temperature is input to the heat medium supply device 50 as a control signal. As a result, the heat medium that has reached the set temperature from the heat medium supply device 50 is
The temperature of the inner wall surface of the plasma generation chamber 10 is adjusted to a predetermined constant temperature. Such temperature control of the inner wall surface of the plasma generation chamber 10 is performed during the etching process of the sample 40 or when the sample 40 is continuously etched one by one.

FIG. 4 shows the plasma generation chamber 40 as described above.
In this case, with respect to the temperature of the inner wall surface of, the change ratio with time of the silicon film with and without the temperature control at 20 ° C. is shown. In FIG. 4, the vertical axis represents the relative value of the selection ratio (hereinafter, abbreviated as a time-dependent relative selection ratio) when the selection ratio to the first processed silicon film is 1.0. Other etching treatment conditions are as follows: Micro power 1 kW, etching pressure 10 mTorr, etching gas (CHF ₃ ) flow rate 50 cc / min, high frequency power 20.
The temperature of the cooling water supplied to the sample table is 0 W and 20 ° C.

In FIG. 4, when the temperature of the inner wall surface of the plasma generating chamber 10 was adjusted, the relative selectivity with time with silicon hardly changed (line A). On the other hand, when the temperature control of the inner wall surface of the plasma generation chamber 10 is not performed (line B), the relative selectivity with time with respect to silicon is the 25th processed number and the selection ratio with the first processed silicon film. It is about 2.4 times.

In the second embodiment, the temperature of only the inner wall surface of the plasma generation chamber exposed to the plasma is controlled. However, for example, a machine is used for mounting the sample on the sample mounting surface of the sample table. When a conventional clamp means is used, the clamp means is also exposed to the plasma, and therefore it is preferable to similarly control the temperature of the clamp means from the viewpoint of improving the relative selectivity over time. That is, from the viewpoint of improving the temporal relative selectivity, it is preferable to control the temperature of the member exposed to the plasma (the member to which the plasma polymer can be attached, excluding the sample). The temperature control technique of the member exposed to the plasma for preventing the change of the relative selection ratio over time is not particularly limited to the second embodiment. For example, the temperature of a member exposed to plasma may be adjusted in order to prevent a change in relative selectivity with time, as described below. (1) For example, a heat generating means such as a heater is provided in the plasma generating chamber, and the heat generating means is determined based on the result of comparison between the detected temperature of the plasma generating chamber and the set temperature that should be maintained at a constant temperature in order to prevent changes in the relative selection ratio over time. Adjust the amount of heat generated in. (2) For example, in the case where the temperature of the plasma generation chamber rises above a set temperature that should be maintained at a constant temperature in order to prevent changes in the relative selection ratio over time due to heating by plasma,
A cooling unit is provided in the plasma generation chamber, and the cooling capacity of the cooling unit is adjusted according to the result of comparison between the detected temperature of the plasma generation chamber and the set temperature. As the cooling means, for example, one using a refrigerant or one utilizing the Peltier effect can be adopted. In the case where the cooling means uses a refrigerant, the heat medium supply device in the second embodiment is replaced with a refrigerant supply device, and the heat medium temperature control device is replaced with a refrigerant temperature or a refrigerant supply amount control device. . (3) For example, by adjusting the temperature of the etching gas introduced into the plasma generation chamber, the temperature of the plasma generation chamber rises above a set temperature that should be maintained at a constant temperature in order to prevent changes in the relative selectivity over time. Prevent. (4) For example, by adjusting the amount of heat medium supplied to the heat medium chamber, the temperature of the plasma generating chamber is adjusted to a set temperature that should be maintained at a constant temperature in order to prevent changes in the relative selection ratio over time.

In the second embodiment, the sample is placed in the plasma generating chamber. In addition to this, the plasma generated in the plasma generating chamber is transferred to the outside of the plasma generating chamber and the sample is etched by the plasma. The sample may be arranged so that In any case, by controlling the temperature of the member exposed to the plasma, the same action as the action in the second embodiment occurs and the temporal relative selectivity is improved. Further, in the second embodiment, the carbon fluoride gas is turned into plasma by the action of the magnetic field and the microwave electric field, and the silicon oxide film of the sample in which the silicon film and the silicon oxide film are laminated is etched by the plasma. Although the case has been described as an example, the present invention can be similarly applied to the case where the above sample is etched by using a parallel plate type plasma etching apparatus. In this case, the inner wall surface of the processing chamber, the electrodes provided inside the processing chamber, and the like are members exposed to plasma. However, in this case, the etching pressure is about one digit higher than that in the second embodiment in which the plasma is generated by the action of the magnetic field and the microwave electric field, so that it is remarkable as in the second embodiment. You can't achieve that effect. Further, in the second embodiment described above, a carbon fluoride gas is used as an etching gas, and a sample in which a silicon film and a silicon oxide film are laminated is used as a sample. In this case, the plasma polymer adhered to the silicon oxide film is removed from the silicon oxide film by the oxygen reducing action of the silicon oxide film, while the plasma polymer adhered to the silicon film does not cause such an action, so that it is removed from the silicon film. Not removed. That is, any sample can be effectively applied as long as it is a sample in which a film containing a component capable of removing the plasma polymerized product even if the plasma polymerized product adheres and a film that cannot remove the adhered plasma polymerized product are laminated. Furthermore, the first embodiment and the second embodiment are combined, that is, the member exposed to the plasma is heated during the etching process of the sample, and the temperature of the member is adjusted to a constant temperature. By doing so, it is possible to overcome the limit due to the control of the etching gas conditions in the etching process of the silicon oxide film, further improve the selectivity of the silicon oxide film, and prevent the selectivity from changing with time. Furthermore, in the second embodiment, the case where the samples are etched one by one has been described. However, when a plurality of samples are simultaneously etched in one processing chamber, or the etching is repeated. The same can be applied to the case. Although CHF ₃ is used as an etching gas in each of the above-described embodiments, the same action and effect as above can be obtained by using other carbon fluoride gas or a mixed gas thereof. .

[0030]

According to the present invention, there is an effect that the etching gas condition control in the etching process of the silicon oxide film can be overcome to further improve the selectivity with respect to the underlying silicon film.

Further, according to the present invention, there is an effect that it is possible to prevent the selection ratio with respect to the silicon film as the base film from changing with time in the etching process of the silicon oxide film.

[Brief description of the drawings]

FIG. 1 is a vertical cross-sectional configuration diagram of a magnetic field plasma etching apparatus according to a first embodiment of the present invention.

FIG. 2 is a relationship diagram between the inner wall surface temperature of the plasma generation chamber and the relative selectivity obtained using the etching apparatus of FIG.

FIG. 3 is a vertical cross-sectional configuration diagram of a magnetic field plasma etching apparatus according to a second embodiment of the present invention.

FIG. 4 is a relationship diagram of the number of processed samples and the relative selectivity over time obtained by using the etching apparatus of FIG.

[Explanation of Codes] 10 ... Plasma generation chamber, 11 ... Microwave introduction window, 12 ... Waveguide, 13 ... Solenoid coil,
14 ... Sample stand, 20 ... Gas supply pipe, 21 ...
Heat medium supply pipe, 22 ... Heat medium discharge pipe, 30 ... Heat medium chamber, 40 ... Sample, 50 ... Heat medium supply device,
51 ... Temperature detection terminal, 52 ... Heat medium temperature control device.

Continuation of front page (51) Int.Cl. ⁶ Identification number Office reference number FI Technical display location H05H 1/46 H05H 1/46 R H01L 21/302 B (72) Inventor Yoshie Sato Higashi-Toyo, Kumamatsu City, Yamaguchi Prefecture Address 794, Hitachi Ltd., Kasado Plant (72) Inventor Satoshi Ito, Higashi-Toyoi, Kudamatsu City, Yamaguchi Prefecture 794 Address, Hitachi Ltd., Kasado Plant

Claims (5)

[Claims] 1. A step of plasma-converting a carbon fluoride gas as an etching gas, and a step of etching the silicon oxide film of a sample in which a silicon film and a silicon oxide film are laminated with the plasma. Heating the plasma generation chamber exposed to the plasma during the etching process. 2. The plasma etching method according to claim 1, wherein the gas is made into plasma by the action of a magnetic field and a microwave electric field. 3. A step of using a carbon fluoride gas as an etching gas to convert the gas into plasma, and a step of etching the silicon oxide film of a sample in which a silicon film and a silicon oxide film are laminated with the plasma. Adjusting the temperature of the plasma generation chamber exposed to the plasma to a constant temperature during the continuous etching process. 4. The plasma according to claim 3, wherein the plasma generation chamber exposed to the plasma is heated and the temperature of the plasma generation chamber is adjusted to a constant temperature during continuous etching of the sample. Etching method. 5. The method according to claim 3, wherein each sample is continuously subjected to an etching treatment, the plasma generation chamber is heated during the continuous treatment, and the temperature of the generation chamber is adjusted to a constant temperature. Plasma etching method.