JPH05275376A - Dry-etching device and dry-etching method - Google Patents

Abstract

PURPOSE:To performs dry-etching at high speed with the high power to select without causing the reaction to pile up by making the surface density of a high-frequency power not less than a specific value, which is radiated to a discharging section, and making the effective pumping speed of an exhaust means not less than a specific value. CONSTITUTION:A microwave is generated by a microwave generator 1 and radiated into a discharging section 25 provided within a vacuum treatment chamber 10 through a waveguide 4 and a microwave introduction window 5. The microwave is brought thereinto so that the surface density of a microwave power becomes not less than 1.6W/cm<2> with the diameter of 35cm of the discharging section. And if the flow rate of an etching treatment gas is 300 s c cm, the rate of reaction product within a gas becomes not more than 20%. Then, the flow rate of Cl2 gas is set to 300 s c cm. In order to allow the gas to flow at the flow rate of 300 s c cm under the pressure of 5m Torr, the effective pumping speed is set to 780 liter/s. Thereby, etching may be performed without the reaction to pile up being brought about.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a dry etching technique for manufacturing a semiconductor device, and relates to a dry etching technique which is high speed and highly selective.

[0002]

2. Description of the Related Art In conventional dry etching, gas pressure has been lowered to perform etching in order to increase etching anisotropy. In order to discharge the plasma even at a low gas pressure, an efficient discharge method must be used. Microwave discharge is used as such a method. As a conventional dry etching technique using microwave discharge, for example, Journal Electrochemical Society, 1982, p. 2704,
Journal Vacuum Science and Technology, 1989, p. 899, Proceedings of Dry Process Symposium, 1990,
p. There is a report example in 99.

Lowering the gas pressure usually slows down the etching rate. Therefore, in conventional dry etching,
High ionization degree of plasma has been used to use high density plasma. Incident ion current increases as the plasma density increases. Since the etching reaction is promoted by the energy of incident ions, the etching rate is increased.

In the microwave discharge, if the input microwave power is increased, the density of the plasma is increased and the incident ion current is increased. However, this does not mean that the microwave power should be increased. Journal Electrochemical Society, 1982, p. As in the example 2704, in the conventional dry etching, the increase in the etching rate with the increase in the microwave power is saturated at a certain microwave power. How much microwave power saturates the increase in etching rate depends on the equipment and conditions. For example, Journal Vacuum Science and Technology, 1989,
p. Like 899, the etching rate may not be saturated even if the input microwave power is increased to 2.5 kW.

However, usually, the increase in etching rate saturates at a microwave power of about 1 kW. Therefore, in the conventional dry etching technology, the microwave power is usually 1k.
It was about W. For example, in the microwave etching apparatus M308 manufactured by Hitachi, Ltd., a maximum of 1.5 kW of microwave was input to generate plasma. The area of the discharge part in this device was 350 mm in diameter. That is, the maximum areal density of the microwave power radiated to the plasma was 1.56 W / cm ² .

The dry etching apparatus described above performs etching by bringing a sample into contact with plasma. Therefore, in etching, not only the ion current density but also the supply of neutral particles from plasma influences the etching rate. On the other hand, in the ion extraction type plasma processing apparatus, since the etching rate strongly depends on the ion current density, the microwave power is increased to 4 kW to increase the ion current density as in JP-A-3-6813. There are also examples.

[0007]

In the conventional dry etching, even if the incident surface current density of microwaves applied to the discharge part or the input microwave current is increased by increasing the input microwave power to increase the incident ion current, the etching is performed. There was a problem that the speed would not increase. Therefore, an RF bias or the like is applied to the sample to reduce the energy of incident ions to 10
The etching rate was increased by increasing the voltage to 0 to 200 V or more. However, at this time, since the incident ion energy is high, there is a problem that the etching selection ratio is lowered.

[0008] The reason why the etching rate does not increase even if the surface area density of the microwaves applied to the discharge part or the density of the plasma is increased by increasing the applied microwave power is that the etching reaction products easily re-dissociate in the plasma. This is because The re-dissociated reaction product easily causes a deposition reaction. Since this deposition reaction cancels the etching reaction, the etching rate decreases. Not only that, the deposition reaction prevails and the deposition of foreign matter may occur. Therefore, the microwave power could not be increased so much, and the ion current density was usually as low as several mA / cm ² .

In addition, in the conventional dry etching technique, when the material to be etched contains a plurality of kinds of atoms such as AlCuSi, a substance having a low vapor pressure tends to remain as a residue even if the etching rate is increased. There was a problem.

Further, in the conventional dry etching technique, there is no method for examining the uniformity of the ion current density on the sample. Therefore, it was not possible to adjust the etching conditions while monitoring the uniformity of the ion current density during discharge.

[0011]

Means for Solving the Problems The power areal density of the high frequency radiated to the discharge part is set to 1.6 W / cm ² or more, and the effective pumping speed of the pumping means is set to 780 liter / s or more.

The conventional dry etching apparatus has an output power of 2
A high-frequency generator of kW or more, preferably 3 kW or more was provided, and the effective pumping speed was set to 780 liter / s or more.

While flowing a gas at least 5 times the desorption amount of the reaction product determined by the etching area and the etching rate,
The ionization degree of plasma is 10% or more, or the incident ion current density is
It was set to 40 mA / cm ² or more.

The wall surface of the etching chamber that is in contact with the discharge part is made of metal, and the wall surface can be cooled by a coolant. Further, a liquid or solid refrigerant was brought into direct contact with the back surface of the sample to cool the sample.

A plurality of temperature detectors were provided on the sample table. The etching parameters such as the external magnetic field condition and the microwave propagation mode were adjusted so that the temperatures of the temperature detecting portions were equalized.

The gas after the etching process was collected and generated.

The reactive gas and the inert gas were alternately discharged. A bias was applied to the sample during the discharge of the inert gas.

[0018]

If the influence of reaction products can be suppressed, the etching rate can be increased by increasing the density of plasma. Therefore, in the present invention, the effective pumping speed is set to 780 lit.
By setting the er / s or more, the reaction product was quickly exhausted to the outside of the apparatus, and the power area density of the high frequency radiated to the discharge part was set to 1.6 W / cm ² or more. The maximum power of the high-frequency generator that inputs the high-frequency power is set to 2 kW or more, preferably 3 kW or more. As a result, the plasma could be made to have a high density without causing the deposition reaction, so that the etching rate can be increased by increasing the high frequency power areal density applied to the discharge part or the applied high frequency power. ..

As a specific etching method, in the present invention, the etching treatment gas is made to flow at least 5 times the desorption amount of the reaction product determined by the etching area and the etching rate. By this method, the proportion of reaction products in the plasma could be reduced to 20% or less. As a result, it was possible to carry out etching while suppressing the influence of the re-dissociation / deposition reaction of reaction products even if the microwave power was increased and the plasma density was increased.

The amount of etching processing gas to be supplied in this dry etching method is determined as follows. For example, an 8-inch Si wafer is 1 μm
2.8 × 10 ¹⁹ / s when etching at / min
Of Si atoms flow into the plasma as reaction products.
This amount is comparable to a gas flow rate of 60 sccm. Since an etching treatment gas that is 5 times or more the desorption amount of the reaction product is flowed, the gas flow rate is 300 sccm or more.

In order to carry out etching while maintaining such a large gas flow rate and maintaining the pressure, it is necessary to increase the effective pumping speed. For example, 300sc as above
For a gas flow rate of cm and a pressure of 5 mTorr, the effective pumping speed is 780 liters.
/ S is required. In the present invention, the effective pumping speed is 780 li
Since it is ter / s or more, etching can be performed with a large gas flow rate and pressure.

By the dry etching apparatus and the dry etching method as described above, it is possible to suppress the deposition reaction of reaction products and perform high-speed etching by high-density plasma. In the present invention, since the plasma ionization degree is 10% or more or the ion current density is 40 mA / cm ² or more, the etching is performed,
The etching rate could be increased.

In the present invention, since the etching rate can be increased by increasing the plasma density to increase the ion current density, it is possible to suppress the application of the RF bias, which was required in the conventional dry etching. For example, in order to obtain a sufficient etching rate when etching with a conventional ion current density of 1 mA / cm ² , ion incident energy of 100 to 200 V or more must be applied. The current density of 1 mA / cm ² is 6.3 × 10 ¹⁵ / cm ² / s when converted into the number of incident ions. With such incident ions, for example, Si is etched at a rate of 1
To etch at μm / min, incident ion 1
It is necessary to react and desorb 10 to 20 Si atoms. In order to cause such a number of reactions with one incident ion, 100 to 200 V or more had to be applied.

However, when the incident ion energy is increased to 200 V or higher in this way, the hot spot temperature increases in both the mask and the material to be etched, so that not only the material to be etched but also the etching speed of the mask material is high. And the etching selectivity decreases. For example, in conventional Si etching in chlorine gas plasma, a resist / Si etching selection ratio of about 10 can be obtained without applying a bias. However, the etching rate at this time is slow at 200 nm / min or less. When an RF bias was applied to increase the etching rate sufficiently and the incident ion energy was set to 200 V or more, the Si etching rate increased to 300 nm / min, but the resist / Si etching selection ratio fell to 5 or less.

In the present invention, the ion current density is 40 mA / c.
Since the etching was performed at m ² or more, it was possible to obtain the etching rate of 1 μm / min or more only by reacting 0.4 Si per incident ion. This reaction can be sufficiently caused by the incident energy of about 10 to several tens V and acceleration by the plasma potential. Since the etching reaction can be caused with such low energy, the reaction rate difference between the etching reactions becomes large, and the etching selectivity is improved.

For example, in Si etching or metal wiring etching, side etching occurs in the Si / metal pattern even under the condition that side etching does not occur in the resist mask. This indicates that the energy required to etch the resist is greater than the energy required to etch Si-metal. That is, when the incident ion energy is lowered, the etching reaction does not occur in the resist mask, but the etching reaction occurs in Si / metal. The energy is in the energy range sufficient to break several chemical bonds, that is, about 10 to several tens of volts. When ions are incident with this energy, the resist mask is hardly etched, and the etching rate of Si / metal increases in proportion to the number of incident ions.

In the present invention, the ion current density is 40 mA / c.
By setting m ² or more, a sufficient etching rate could be obtained with an ion energy of about 10 to several tens of V without applying an RF bias, so that high speed and high selective etching could be performed. ..

In the conventional etching, when etching a material containing a plurality of atomic species such as AlCuSi, the vapor pressure of the reaction product is different, so that a substance having a low vapor pressure and difficult to desorb, for example, a Cu residue remains. There was a problem. In order not to leave this residue, etching could not be performed unless the energy of incident ions was increased. Therefore, the etching selection ratio with respect to the mask material was small.

In the present invention, the reactive gas and the inert gas are alternately discharged by using the high density plasma to perform etching, so that high selective etching can be performed without leaving a residue of a substance having a low vapor pressure. Became. The effect will be described below.

Even in a substance having a low vapor pressure of the reaction product, the etching reaction proceeds even if the incident ion energy is small. For example, in the case of Cu, the etching reaction proceeds relatively quickly even under mild conditions, so that the thickness of the deposited layer of the reaction product increases if the etching is performed under the condition that the reaction product is not desorbed.

In order to remove this reaction product, the incident energy of ions must be increased. In the past, since the incident energy of ions was increased in the plasma of the etching gas, the incident ion energy promoted not only the desorption of reaction products but also the etching reaction of the resist mask. It was

For desorption of the reaction product, only the incident energy of the ions is required, and other reaction-active etchant is not necessary. That is, inactive ions may be incident. For example, even if the inert gas plasma is discharged and the ions of the inert gas are made incident, the reaction products are desorbed.
Of course, if an RF bias is applied at this time, the reaction products can be efficiently desorbed, and the reaction products can be efficiently desorbed even if the density of the plasma is increased and the incident ion current is increased.

Since no etchant is supplied during this inert gas discharge, the etching reaction of other substances hardly occurs. Only the reaction product having a low vapor pressure is desorbed by the ion injection of the inert gas. For the above reasons, by alternately discharging the reactive gas and the inert gas for etching, it becomes possible to perform high selective etching even when the reaction product contains a substance having a low vapor pressure. It was

In the present invention, since the density of plasma is increased,
The device wall surface of the discharge part is heated by plasma more than before. In the present invention, since the device wall surface of the discharge part is made of metal and is cooled by the refrigerant, it is possible to prevent the device wall surface of the discharge part from overheating. Further, since the time change of the temperature on the device wall surface of the discharge part could be suppressed, the time change of the etching characteristics could be suppressed.

In the present invention, in order to suppress the temperature rise of the sample during etching, a liquid or solid cooling medium is brought into direct contact with the back surface of the sample for cooling. In the past, gas was used to cool the sample. Since the thermal conductivity of gas is smaller than that of liquid or solid by two digits or more, the cooling efficiency of the sample was not sufficient. In the present invention, the cooling efficiency is increased by bringing the liquid or solid coolant into direct contact with the back surface of the sample to cool the sample, so that it is possible to suppress heating of the sample due to an increase in ion current density and an increase in etching rate.

In the present invention, in order to prevent the deposition of reaction products, the etching treatment gas is flowed in an amount larger than the amount of reaction products generated. Therefore, 80% or more of the discharged gas is unused gas. In the conventional device, this gas is exhausted after removing harmful components through a scrubber or an exclusion device. However, in order to flow a large gas flow, a large scrubber was required, and the adsorbent of the exclusion device had to be frequently replaced. The present invention separates unused gas
Since the device for collecting is provided, the cost required for removing harmful components can be reduced.

In the present invention, a plurality of temperature detectors are provided on the sample table, and the discharge conditions are adjusted so that the temperatures are equal. Since the temperature rise during discharge is proportional to the ion current density, such adjustment made the ion current density uniform. Since the etching rate strongly depends on the ion current density, it was possible to improve the etching uniformity by this adjusting method. Conventionally, it was necessary to examine the in-plane distribution of etching rate for etching uniformity,
It was possible to easily obtain the conditions with good etching uniformity in a short time.

[0038]

[Embodiment 1] An embodiment of the dry etching apparatus according to the present invention will be described. FIG. 1 is a configuration diagram of an embodiment of a dry etching apparatus according to the present invention. In this device, a microwave is generated by the microwave generator 1, and the microwave is passed through the waveguide 4 and the microwave introduction window 5,
It radiates to the discharge part 25 provided in the vacuum processing chamber 10. In the present invention, the power is applied so that the power area density of the microwave is 1.6 W / cm ² or more with respect to the diameter 35 cm of the discharge part 25. For this reason, the microwave generator 1 has a maximum input power of 2 kW or more, preferably 3 kW or more, and the high density plasma is discharged. Therefore, the microwave generator 1, the waveguide 4, and the wall surface of the discharge unit 25 generate more heat than the conventional dry etching apparatus. A cooling mechanism 2 was provided to cool this heat, and a cooling medium was flown into the cooling mechanism 2 to cool the apparatus. The tuner rod 3 is provided in the middle of the waveguide 4 in order to efficiently radiate the input microwave power to the discharge section 25.

The flow rate of the etching process gas is controlled by the gas flow rate controller 7 from the gas pipe 6 and introduced into the discharge section 25 through the gas introduction port 8. A buffer chamber 9 was provided between the gas inlet 8 and the discharge part 25 in order to make the gas flow rate small and to uniformly flow the gas into the discharge part 25. A large number of small holes on the mesh are opened on the wall surface of the buffer chamber 9,
Gas was made to flow into the discharge part 25 through this small hole.

In order to efficiently discharge the introduced etching treatment gas by microwaves, a magnetic field is generated by the solenoid coil 24, and the microwaves are efficiently absorbed by plasma by electron cyclotron resonance (ECR). I did it.

The gas after the etching process is exhausted from the vacuum processing chamber 10 by the turbo molecular pump 18 via the conductance valve 17. In this apparatus, a large gas flow rate is supplied so that 20% or less of the total gas flow rate is consumed in the etching reaction. The turbo molecular pump 18 exhausts 80% or more of the gas as unused processing gas. Therefore, in the present invention, means for recovering the unused processing gas in the exhausted gas is provided. In this example,
The processing gas was liquefied by the liquefier 19, the liquefied gas was purified by the purifier 20, and the separated unused processing gas was collected in the collection container 21. In the liquefier 19, the pressure and temperature were adjusted so that the unused processing gas was liquefied. In the purifier 20, the unused processing gas and other gases were separated by distillation. The used gas (reaction product) separated by the liquefier 19 and the purifier 20 is a detoxification device 22,
After passing through the scrubber 23, it is released into the atmosphere. Since the unused processing gas is collected as described above, the harmful etching processing gas hardly passes through the abatement device 22. Therefore, the frequency of exchanging the adsorbent in the abatement device 22 can be reduced from 12 times / year to once / year or less. In addition, since the recovered gas can be reused, the cost for gas and detoxification can be suppressed.

The wafer 14 to be etched is the sample stage 11
Is installed in. A sample cooling line 12 is provided on the sample table 11.
Is provided. The sample cooling line 12 is opened at the upper part of the sample table so that the coolant directly contacts the back surface of the wafer 14. The refrigerant is cooled by the circulator 13 and circulates in the sample cooling line 12. Since the cooling medium comes into direct contact with the back surface of the wafer 14, it must be prevented from leaking into the vacuum processing chamber 10. Therefore, in this embodiment, the dielectric 15 and the DC power supply 26 are used so that the sample table 11 and the wafer 14 are brought into close contact with each other by electrostatic attraction.

An RF power source 16 is connected to the sample table 11,
An RF bias can be applied to the wafer 14.

How to obtain high-density plasma by using this apparatus and how to realize the ion current density of 40 mA / cm ² will be described. FIG. 2 shows the relationship between the pressure and the ion current density when the ionization degree of plasma is constant. When the ionization degree of plasma is 1%, the ion current density is 40 mA / cm ² or more because the pressure is 100 mTo
It is the time of rr or more. 1 if the ionization degree is increased to 10%
Ion current density is 40mA / at pressure over 0mTorr
cm ² or more. 1mTorr if ionization degree is 100%
The above pressure may be used. Since the upper limit of the degree of ionization is 100%, at least the pressure must be 1 mTorr or more in order to set the ion current density to 40 mA / cm ² or more.

FIG. 3 shows the relationship between the ionization degree of plasma and the ion current density when the pressure is constant. As described above, at a pressure lower than 1 mTorr, the ionization degree becomes 1
Even if it is set to 00%, an ion current density of 40 mA / cm ² or more cannot be obtained. When the pressure is 10 mTorr, the ion current density is 40 mA / cm ² or more at an ionization degree of 10% or more. At a pressure of 100 mTorr, the degree of ionization may be about 1%.

The range shown by the thick line in this figure is the range of the ion current density in the conventional dry etching apparatus. Up to 15m by NEC at 0.5mTorr
An ion current density of A / cm ² has been obtained and is 1 mTo
The maximum ion current density of 30 mA / cm ² is obtained for rr. These values correspond to a high ionization degree of 75% when converted into plasma ionization degree. Actually, the whole plasma is not ionized with such a high degree of ionization. In the conventional dry etching system, the external magnetic field is EC
Since the microwave absorption occurs in the portion satisfying the R condition, the ionization degree of this portion becomes extremely higher than that of the other portions. Therefore, if a portion satisfying the ECR condition is brought close to the wafer, a high ion current density can be obtained even if the ionization degree of the whole plasma is low. Then, the ionization degree of the portion satisfying the ECR condition depends on the microwave power.

FIG. 4 is a diagram showing the relationship between microwave power and ion current density. As shown in this figure, the microwave power and the ion current density have a linear relationship, and the ion current density increases as the microwave power increases. However, the ion current density does not increase indefinitely, and as shown in FIG. 2, under a certain pressure, the value with an ionization degree of 100% is the upper limit. Therefore, in this embodiment, etching is performed at a pressure of 5 mTorr. At this pressure,
An ion current density of 200 mA / cm ² can be obtained at an ionization degree of 100%. The relationship between the microwave power and the ion current density at this time is also shown in FIG. Ion current density is 40mA / cm when microwave power is over 3kW
It became ² or more.

As described above, even if the high density plasma is used, the etching can be carried out while suppressing the influence of the reaction products, so that the high speed etching can be performed without applying the RF bias. .. For example, in Si etching, in an 8-inch wafer, an etching rate of 1 μm / min could be obtained without applying an RF bias. If RF bias is applied to this,
Further, the etching rate becomes faster. For example, R at 2MHz
When F bias of 30W is applied, the etching rate is 2μ
Go up to m / min. By applying a bias, the directionality of ions is also increased, so that etching with better anisotropy can be performed. These effects are higher when the applied bias is increased, but the selection ratio becomes worse as the bias is increased. In the present example, the resist / Si etching selection ratio when the bias was not applied was 50, whereas when the bias was applied at 2 MHz and 30 W, the selection ratio was 25. The frequency and power of the RF bias vary depending on the etching conditions and the required etching characteristics. Therefore, if the optimum value is used in each case, more accurate etching can be performed.

As for the gas pressure, the frequency of collision between incident ions and gas particles decreases, so a lower pressure is, for example, 1 to
Etching at 5 mTorr enables highly anisotropic etching. For example, a trench having an opening width of 0.5 μm can be processed with an aspect ratio of 10 or more. in this case,
In order to obtain a high ion current density, it is necessary to increase the ionization degree of plasma as compared with the case where the pressure is high, and therefore it is necessary to increase the input high frequency power. In this example, the input microwave power of 3 kW or more was required. This is 3.1 W / cm ² or more when converted to power surface density.

In the region where the gas pressure is about 5 to 10 mTorr, a high ion current density can be obtained even with an ionization degree of about 10%, so that the input power may be small. Although the anisotropy is lower than in the case of low pressure, the etching rate also increases because the number of incident etchants increases. With the apparatus of this embodiment, the pressure is 10 mTorr,
When the microwave input power was 3 kW, the etching rate could be 5 μm / min or more. A trench having an opening width of 0.5 μm can be etched up to an aspect ratio of about 5 without decreasing the etching rate. An etching rate of 1 μm / min could be obtained even when the input microwave power was 2 kW. In this case, the surface density of input power is 2.1 W / cm ² .

When the gas pressure is 10 mTorr or more,
The frequency of collision between ions and gas particles increases, and the etching anisotropy deteriorates. However, since the ion current density can be increased even if the input microwave power is low, isotropic, high-speed and high-selective etching can be performed. Therefore, residue removal and the like during overetching can be effectively performed. For example, at a pressure of 100 mTorr, if the input power is increased to 3 kW or more, high-speed etching is possible. However, even if it is 2 kW or less, for example 1.6 kW (power surface density 1.7 W / cm ² ), the etching rate is 1 μm / mi.
n could be obtained. At this time, overetching could be performed with a selection ratio of 100 or more with respect to the underlying SiO ₂ . This effect can be obtained similarly even when the gas pressure is increased to 1000 mTorr.

[0052]

Example 2 With the apparatus of Example 1, the ion current density could be 40 mA / cm ² or more. In order to perform etching with good uniformity using this high ion current density, the uniformity of ion current density must be improved. The uniformity of the ion current density can be adjusted by etching parameters such as external magnetic field conditions. In this embodiment, these adjusting means and their methods will be described.

Since the ions are accelerated by the plasma potential and enter, the ions are heated by Joule heat at the incident part and the temperature rises. If the ion current densities are equal, the calorific value is also equal. Therefore, by providing a plurality of temperature detectors on the sample table 11 and adjusting the external magnetic field conditions so that the respective temperatures are equal, the uniformity of the ion current density can be increased. FIG. 5 is a layout view of the temperature detection unit on the sample table. As shown in the figure, a plurality of temperature detection units 27 are provided on the sample table 11.
In this embodiment, the temperature detection unit 27 has SiO ₂ as a cover, and the temperature of the SiO ₂ is measured from the back surface by a contact type fluorescent thermometer. The temperature of each part was measured during discharge, and the external magnetic field conditions were adjusted so that those temperatures were equal. The external magnetic field conditions were adjusted by the amount of current flowing through the solenoid coil 24 and the coil position. By performing the adjusting means and the adjusting method as described above, it was possible to improve the uniformity of the ion current density. As a result, etching can be performed with good uniformity.

In order to improve the etching uniformity by the conventional dry etching technique, it was necessary to actually etch the sample and obtain the in-plane distribution of the etching rate.
Therefore, it took time and effort to optimize the external magnetic field conditions. By using the method of the present invention, it is possible to optimize the external magnetic field condition for each process in a short time, so that the time and cost required for the adjustment can be reduced.

As the adjustment parameter, in addition to the external magnetic field condition, the setting position of the tuner rod for matching the microwave is changed, the propagation mode of the microwave is converted, a dielectric or the like is installed in the discharge part. It may change its position, change the microwave input power, or radiate different types of electromagnetic waves. The method of the present embodiment is also effective for these adjustments.

[0056]

[Third Embodiment] The present invention enables high-speed and high-selective etching. As one example thereof, Si etching using a resist mask will be described.

The idea of the present invention is to perform high-speed etching even with low incident ion energy by increasing the density of the plasma and increasing the ion current density. By setting the ion current density to 40 mA / cm ² or more, which is 10 times or more the conventional ion current density, the incident ion energy is 10 to 10 V, which is about 1/10 of the conventional ion current density, and high-speed etching can be performed even if the plasma potential is about the same. can do. Since the incident ion energy is low as described above, the difference in reactivity between substances becomes large, and an effect of obtaining an extremely high selection ratio can be obtained.

High-density plasma cannot be used in the conventional dry etching technique. The reason for this is that when the plasma density is increased, reaction products are re-dissociated and redeposited, so that the etching reaction and the deposition reaction compete with each other. This is because there are problems that the etching rate does not increase, the pattern becomes tapered, and foreign matter adheres. In the present invention, since the partial pressure of the reaction product can be lowered by increasing the effective pumping speed and increasing the flow rate of the etching processing gas, it becomes possible to perform the etching by the high density plasma without causing the deposition reaction. It was

That is, if a gas component that easily causes a deposition reaction is included, the effect of the present invention cannot be effectively utilized even if the plasma density is high. For example, when a deposition gas such as CF ₄ gas is used as the etching processing gas, the etching processing gas itself causes a deposition reaction. In order to effectively use the effects of the present invention, it is better to use a non-depositing gas as the etching processing gas. Any non-depositing gas such as a fluorine-based gas, a chlorine-based gas, or a bromine-based gas may be used. In this example, Cl ₂ gas was used as the etching processing gas.

As described in Example 1, the gas pressure is 1 m.
If it is lower than Torr, the ion current density cannot be increased to 40 mA / cm ² or more even if the plasma density is high. Therefore, in this embodiment, the etching is performed at a pressure of 5 mTorr.

As a sample, a poly Si layer deposited to a thickness of 1 μm on a SiO ₂ layer was etched by a resist mask having a thickness of 1 μm. The size of the sample is an 8-inch wafer, and the ratio of the Si exposed portion is 50%. Wafer 1
The processing time per sheet is around 30 seconds, and since the throughput is high and processing is easy, the etching rate is 2 μm / min.
The degree is desirable. In the present invention, the ion current density is 40 mA.
/ Cm ² or more, a sufficient etching rate could be obtained without applying a bias.

When the etching rate is 2 μm / min, the number of Si atoms desorbed from the wafer is 2.8 × 10 ¹⁹ /
s. This is 60 sccm when converted into a unit of gas flow rate sccm. If the flow rate of the etching gas is 300 sccm, the ratio of reaction products in the gas is 2
It will be 0% or less. Therefore, in this embodiment, the flow rate of Cl ₂ gas is set to 300 sccm. Further, if the flow rate of Cl ₂ gas is increased, the deposition reaction can be suppressed more completely, so that a higher density plasma can be used. How much gas flow rate and how much high-density plasma is used differ depending on the etching gas species, the sample and the mask type.

Gas flow rate of 300 scc at a pressure of 5 mTorr
To pump m, the effective pumping speed is 780 liters
/ S is required. In the present invention, the effective pumping speed of the device is 7
Since it is increased to 80 liter / s or more, the large gas flow as described above can be passed.

In the present invention, the etching is performed so that the deposition reaction does not occur. Therefore, the side etching cannot be suppressed by the side wall protective film which is automatically formed during the etching. Therefore, it is necessary to suppress the side etching by adding a process of forming the side wall protective film or by low temperature etching. Therefore, in this embodiment, the sample temperature is set to −60.
By keeping the temperature below ℃, the reaction on the side wall due to radicals was suppressed. As a result, it was possible to perform etching without side etching even without the sidewall protective film.

Under the above conditions, microwave power of 3 kW was applied to the discharge part for etching. As a result, the etching rate of poly Si is 2 μm / min.
On the other hand, the etching rate of the resist mask is 40 nm /
It was possible to perform etching with a selection ratio of 50 and min. Since the sample was cooled efficiently by directly contacting it with a liquid coolant from the back surface, the wafer temperature during etching could be kept at -60 ° C or lower. I was able to make a high selection.

The above-mentioned effects are effective not only for etching the resist mask and Si, but also for other substances. Al,
Even under the condition that side etching occurs in metals such as W, Cu and GaAs or in semiconductors, side etching does not occur in insulators such as SiO ₂ . That is, in the etching of metal or semiconductor, the etching reaction occurs even when the incident ion energy is lower than the etching of the insulator. Therefore, when etching a metal or a semiconductor using an insulator as a mask, the same effect as that of this embodiment can be obtained.

[0067]

Fourth Embodiment As described in the third embodiment, in the present invention, by increasing the amount of incident ions and lowering the energy,
High-speed and highly selective etching can be performed.
However, when the agent to be etched contains a plurality of kinds of atoms, there is a problem that a reaction product having a low vapor pressure remains as a residue. For example, in etching AlCuSi, Cu
The reaction product of is likely to remain as a residue. Therefore, in the conventional dry etching technique, a high RF bias is applied so that a reaction product having a low vapor pressure does not remain as a residue. At this time, there is a problem that the selection ratio with respect to the mask becomes small because the energy of incident ions is high.

In order to desorb a reaction product having a low vapor pressure, the amount of incident ions may be increased instead of increasing the energy of incident ions. However, at that time, a reaction product having a high vapor pressure is more likely to be desorbed, so that a reaction product having a low vapor pressure remains as a residue.

Therefore, in this embodiment, the steps of low incident ion energy and high incident ion energy were alternately repeated. At this time, the reactive gas was discharged in the step where the incident ion energy was low, and the inert gas was discharged in the step where the incident ion energy was high.
By this method, it was possible to perform etching at high speed and with high selectivity and without leaving a residue. This dry etching method will be described below by taking AlCuSi etching with a resist mask as an example.

In the step of low incident ion energy, Cl ₂ gas was discharged as described in Example 3. The discharge conditions and sample temperature were the same as in Example 3.
By increasing the plasma density, the etching reaction of the resist mask was suppressed and the etching reaction of AlCuSi was able to occur. At this time Al and Si
Since the reaction product of (1) has a high vapor pressure, it is desorbed in this step. However, since the reaction product of Cu has a low vapor pressure,
A considerable amount remains as a residue.

In order to desorb this residue, high energy ion injection is required. Therefore, the inert gas was discharged and an RF bias was applied so that high-energy inert gas ions were incident. The energy desorbs the residue of the reaction product. However, since the etching reaction does not occur in the discharge of the inert gas, substances other than the reaction product of Cu are not desorbed. In the conventional dry etching technique, the reactive ion that causes the etching reaction is injected with high energy under the condition that the etching reaction occurs, so that the etching selection ratio is small. On the other hand, in this embodiment, the etching reaction is caused by low ion energy, and the reaction product is desorbed by the high energy of the inert ion in the inert atmosphere, so that the high speed and high selective etching is performed. It could be done without residue.

In this example, Xe gas discharge was used as the discharge of this inert gas. The reason why Xe is used is that the incident energy can be efficiently transferred to the reaction product because of its close mass to Cu. The pressure is 5 mtorr, the gas flow rate is 500 sccm, and the microwave power is 3 kW.
The ion current density was set to 40 mA / cm ² or more so as not to be affected by the reaction product. The RF bias was 100 W at 2 MHz.

The discharge of Cl ₂ gas and the discharge of Xe gas were alternately repeated for 1 second each. As a result, AlCuS
The etching rate of i was 1 μm / min, while the etching rate of the resist mask was 40 nm / min.

By repeating the above two steps, it is possible to perform high-speed and highly selective etching even if the reaction product contains a plurality of types of atoms and the reaction product has a low vapor pressure. I can do it. Although the example of AlCuSi is described in the present embodiment, other substances are also effective. Also in Cu etching, not only reactive gas plasma etching as in Example 3 but reactive gas and inert gas discharge are alternately performed as in this Example to remove reaction products. Desorption may be promoted.

[0075]

According to the present invention, high-speed and highly selective dry etching can be performed. Further, even when the vapor pressure of the reaction product is low, the etching rate of the mask can be suppressed and high-speed and highly selective etching can be performed.

[Brief description of drawings]

FIG. 1 is a configuration diagram of an embodiment of a dry etching apparatus according to the present invention.

FIG. 2 is a diagram showing a relationship between plasma pressure and ion current density.

FIG. 3 is a diagram showing a relationship between an ionization degree of plasma and an ion current density.

FIG. 4 is a diagram showing a relationship between input microwave power and ion current density.

FIG. 5 is a layout view of a temperature detection unit on a sample table which is an embodiment of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Microwave generator, 2 ... Cooling mechanism, 3 ... Tuner rod, 4 ... Waveguide, 5 ... Microwave introduction window, 6 ... Gas piping, 7 ... Gas flow controller, 8 ... Gas introduction port, 9 ...
Buffer chamber, 10 ... Vacuum processing chamber, 11 ... Sample stage, 12 ...
Sample cooling line, 13 ... Circulator, 14 ... Wafer, 15 ... Dielectric, 16 ... RF power supply, 17 ... Conductance valve, 18 ... Turbo molecular pump, 19 ... Liquefaction device,
20 ... Purifier, 21 ... Recovery container, 22 ... Harmful device, 23
... Scrubber, 24 ... Solenoid coil, 25 ... Discharge section, 26 ... DC power supply, 27 ... Temperature detection section.

Claims (12)

[Claims] 1. A dry etching apparatus having a high frequency generating means, a discharge part, and an exhaust means, wherein a plasma is generated by radiating a high frequency to the discharge part, and etching is performed by the plasma. The dry etching apparatus is characterized in that the power areal density of the high frequency radiated to the substrate is 1.6 W / cm ² or more, and the effective exhaust speed of the exhaust means is 780 liter / s or more. 2. A dry etching apparatus having a high frequency generating means, a discharge part, and an exhaust means, wherein plasma is generated in the discharge part and etching is performed by the plasma,
The maximum output power of the high frequency generator is 2 kW or more,
And the effective pumping speed of the pumping means is 780 liter /
A dry etching apparatus characterized by being s or more. 3. A dry etching apparatus having a high frequency generating means, a discharge part and an exhaust means, wherein plasma is generated in the discharge part and etching is performed by the plasma,
The maximum output power of the high frequency generator is 3 kW or more,
And the effective pumping speed of the pumping means is 780 liter /
A dry etching apparatus characterized by being s or more. 4. A dry etching method in which an etching treatment gas is brought into a plasma state by electric discharge, and an incident ion from the plasma promotes an etching reaction and desorption of a reaction product, which is 5 times or more the desorption amount of the reaction product. The ionization degree of the plasma is set to 1 while flowing the etching treatment gas of
The dry etching method is characterized in that the current density of the incident ions is set to 0% or more or the current density of the incident ions is set to 40 mA / cm ² or more. 5. The dry etching apparatus according to claim 1, wherein a wall surface of the etching chamber in contact with the discharge part is made of metal and a mechanism for cooling the wall surface is provided. 6. A dry etching apparatus comprising means for bringing a liquid or solid cooling medium into direct contact with the back surface of the sample. 7. A dry etching apparatus comprising means for collecting and purifying gas after etching processing. 8. A dry etching apparatus comprising a plurality of temperature detecting parts provided on a sample table. 9. A dry etching method characterized in that a plurality of temperature detecting portions are provided on a sample table, discharge is generated, and etching parameters are adjusted so that the temperatures of these thermometers become equal. 10. A dry etching method in which different types of gases are alternately and periodically discharged, wherein a reactive gas and an inert gas are alternately discharged. 11. The dry etching method according to claim 10, wherein a bias is applied to the sample during discharge of the inert gas. 12. A Cl ₂ gas is used as a reactive gas, and an Xe gas is used as an inert gas.
The dry etching method according to 0 or 11.