JP4160946B2 - Manufacturing method of semiconductor device - Google Patents

Description

  The present invention relates to a plasma processing method and a plasma processing apparatus, and more particularly to a dry etching process in which a raw material gas in a gas phase is converted into plasma and the surface of a semiconductor material is processed by physical or chemical reaction of activated particles. It relates to plasma processing.

With the recent miniaturization of semiconductor elements, multilayer wiring layers and three-dimensional element structures are progressing. Accordingly, it is considered that the processing of the insulating film used for maintaining the electrical insulation between the wiring and the elements becomes more and more important. For etching the silicon oxide film which is an insulating film, perfluorocarbon gases (PFC) such as CF ₄ and C ₂ F ₈ and hydrofluorocarbon gases (HFC) such as CH ₂ F ₂ and CHF ₃ have been used. It was. This is because a gas containing carbon is indispensable for breaking the Si—O bond of the silicon oxide film and generating a volatile compound.

  In recent years, however, environmental problems on a global scale have been highlighted. However, the PFC and HFC described above are easy to absorb infrared rays and have a long life in the atmosphere of over 3000 years. The impact is so great that it is expected that their use will be limited or difficult to obtain in the future.

In PFC and HFC gas plasma, fluorocarbon radicals such as F, CF ₁ , CF ₂ , and CF ₃ and ions are present. Etching of silicon oxide film is a mechanism in which these active species (radicals) adhere to the reaction surface of silicon oxide film, and volatiles are generated by chemical reaction under a pseudo high temperature state by the energy of ions incident on the silicon oxide film. Proceed with Therefore, in order to obtain good etching characteristics, it is necessary to control the active species incident on the sample and the energy and density of ions incident on the sample. Control of the density and active species of ions in the plasma is controlled by the plasma generation mechanism of these etching apparatuses.

  In addition, as a method for generating active species in a reaction vessel, for example, Patent Document 1 describes that the inside of a reaction vessel is made of a carbon-based material, and this carbon component is supplied into plasma and etched. .

  In Patent Document 2, the reaction vessel is made of ceramics to prevent a decrease in the etching action due to active species on the sample, and a heater is provided on the outer periphery of the reaction vessel to prevent thermal shock from plasma on the ceramic reaction vessel. It is described to reduce.

  On the other hand, when PFC or HFC gas plasma is used, the fluorocarbon-based or carbon-based polymer adheres to the reaction chamber wall as the sample processing proceeds. As described in Japanese Patent Application Laid-Open No. 5-62936 as a method for removing the deposit, an electrode which is insulated from the outer wall of the reaction chamber and divided into a plurality of portions is installed on the inner surface of the reaction chamber, and an electrode for plasma generation There is known a method of performing plasma cleaning by sequentially applying a high-frequency voltage between the two. Patent Document 3, Patent Document 4, and Patent Document 5 describe a plasma cleaning method by applying a voltage to an electrode insulated from the outer wall of a reaction chamber.

Japanese Patent Laid-Open No. 7-74147 Japanese Unexamined Patent Publication No. 4-3633021 JP-A-1-231320 JP-A-1-231321 JP-A-1-231322

  However, even if plasma cleaning is performed as in the conventional example, deposits are present on the reaction chamber wall before cleaning. Since fluorine in the plasma reacts with the adhesion layer on the inner wall of the reaction chamber, the fluorine density in the plasma gradually decreases and the proportion of carbon in the plasma increases. That is, as the adhesion to the reaction chamber wall progresses, the radical composition changes, which causes a change over time in that the etching characteristics change, which is a serious problem.

  On the other hand, the etching apparatus can be classified into a capacitive coupling type, an ECR (electron cyclotron resonance) type, an ICP (inductive coupling) type, a surface wave excitation type, and the like according to a plasma generation mechanism. In the capacitively coupled device, a sample is placed on the lower electrode, and plasma generation control and sample incident energy control are attempted by applying different frequencies and voltages to the upper electrode and lower electrode by two voltage application mechanisms. Because of its structure, these cannot be controlled independently. The active species control in this apparatus is considered to be performed by carbon or silicon used for the electrode, but there is no control parameter for this. Therefore, the control by the two upper and lower power sources must perform three controls: ion density, energy control of ions incident on the sample, and control of active species, and a range of various parameters (processes) for obtaining good etching characteristics. There is a problem that it is difficult to obtain stable etching conditions. Here, the parameters that determine the etching characteristics include, for example, high-frequency power, μ-wave power, gas flow rate, gas pressure, and gas composition supplied between the electrode plates in the plasma generation mechanism. In the incident ion energy control, there are a waveform, frequency, power, and the like of an applied voltage.

  On the other hand, plasma generation methods other than the capacitive coupling type can control the plasma generation control independently of the energy control of ions incident on the sample, but the mechanism for controlling the active species depends on the plasma generation control. This also has the problem that the process window is narrow. Specifically, when SAC (Self Align Contact) silicon oxide film processing is performed with a high-density plasma etching apparatus such as ECR, the trade-off between etching stop at the hole bottom and silicon nitride film scraping becomes a problem. ing. Further, when etching with high selectivity is performed using high-density plasma, a microloading phenomenon in which the etching rate decreases as the hole diameter decreases and a reverse microloading phenomenon occur, which is a problem. Further, when metal processing of a laminated film such as TiN and Al is performed with these apparatuses, there is a problem that a local abnormal side etching shape (notching) can be formed at the boundary between different materials such as TiN and Al.

  In addition, the method described in Patent Document 1 cannot control the amount of appropriate active species, and it is difficult to perform desired etching. In addition, in the method of patent document 2, there exists a problem that an active species cannot be produced | generated within reaction container.

  The above object is achieved by generating an amount of active species necessary for etching in a region where the plasma is in contact.

Specific description will be given below. In the etching of the silicon oxide film and silicon nitride film on the sample, for example, a gas containing fluorine is introduced into the reaction chamber and maintained in a low gas pressure state such as 0.3 Pa-200 Pa, and μ wave or RF wave This gas is discharged by the input power of, and plasma is generated. Then, a direct current or a high frequency voltage is applied to a carbon-containing solid placed in a region in contact with the plasma to release a desired amount of carbon, and fluorine radicals in the plasma are converted into CF, CF ₂ , CF ₃ , C _2. The sample is converted into a fluorocarbon radical such as F ₄ and etched.

Moreover, if a gas containing fluorine and not carbon is introduced as a gas to be introduced into the reaction chamber, and the fluorine-containing gas and solid carbon are reacted in the reaction chamber, a silicon oxide film or silicon is used without using PFC or HFC. A nitride film or the like can be selectively etched. That is, when plasma is generated by fluorine gas not containing carbon, and fluorine atom ions are reacted with solid carbon newly installed in the reaction chamber, carbon and fluorine of CF ₄ , CF ₂ , CF ₃ , C ₂ F ₄ Can be produced. The active species molecules which are these compounds can be directly generated from the dissociation of the PFC gas conventionally, and the silicon oxide film can be etched by the generated active species molecules. The feature of the present invention is that in the etching of the silicon oxide film and the silicon nitride film, the active species necessary for the etching is not directly supplied from the PFC or HFC gas, but is converted and generated by reaction with the solid in the plasma processing chamber. By this method, even when PFC and HFC gas are restricted and prohibited from being used, it is possible to generate active species necessary for etching and perform etching while maintaining the conventional selectivity.

On the other hand, the problem of improving the selection ratio and the process margin at the time of SAC processing can be achieved by singly seeding into CF ₂ which is an etchant of the silicon oxide film. On the other hand, the active species control material is carbon, and this is arranged on the plasma boundary surface, thereby reducing the fluorine in the plasma to 1/2, compared to the case where aluminum is used as the active species control material, the CF _1, CF _2, CF ₃ discovered the phenomenon each can be increased in 5,10,2 times. The results are shown in FIG. FIG. 2 shows the results of measurement of fluorine and CF ₂ in CF ₄ plasma when Al, SiO ₂ , and C are used as the active species control material. This result shows that when aluminum is used as the active species control material, there is no reaction with fluorine, so the fluorine density is large, but when carbon is used, the fluorine density is halved compared to aluminum. This is considered to be caused by a conversion reaction in which the active species control material carbon reacts with fluorine in the plasma and CF ₂ increases. At this time, it was confirmed that CF ₁ and CF ₂ also increased. In addition, when the active species control material is SiO ₂ , CF ₁ , CF ₂ , and CF ₃ are reduced in the same manner as fluorine in the plasma, and CF ₁ , CF ₂ , CF ₃ and the active species control material SiO ₂ chemically react. It shows that. In this way, the active species composition in the plasma can be changed by providing an active species control material that causes a chemical reaction with the active species in the plasma and volatilizes the product in the plasma region. Even when silicon or silicon carbide was used as the active species material, a chemical reaction that generated volatiles such as SiF ₂ occurred, and fluorine in the plasma could be reduced.

Furthermore, it was confirmed that the single species of the active species was promoted by installing a voltage application mechanism in the active species control material and applying a voltage in parallel with the sample processing. FIG. 3 shows the results of measurement of the radical density of CF ₁ , CF ₂ , and CF ₃ when a negative DC voltage is applied to the carbon active species control material in CF ₄ gas plasma. It was newly found that CF ₃ decreases and CF ₂ increases as the applied voltage increases. This phenomenon is caused by an ion assist reaction on the active species control material. Utilizing this effect, the plasma in which the fluorine in the plasma is converted to CF ₂ and the active species is converted into a single species, the reaction product volatilizes on the silicon oxide film and the etching proceeds. Selective etching in which etching stops due to residue on the film is possible, and the problem of shoulder shaving of the nitride film due to a decrease in selectivity can be solved. It is also confirmed that the microloading and reverse microloading phenomena can be suppressed by using CF ₂ which has a lower adhesion coefficient to the etching side than carbon compared to the conventional etching mechanism based on the balance between carbon and fluorine. did it.

  In addition, when etching samples with significantly different etching rates, the active species control material is the same element as the material to be etched or a compound containing at least one element that is the same as the material to be etched, and the active species is controlled by the material to be etched. By controlling the voltage applied to the material over time or monitoring and consuming / releasing the radicals that are the active species control material, local abnormal shapes such as those occurring between different materials could be suppressed.

  Furthermore, the problem of local shape anomalies between different materials in metal etching can be solved by reducing the variation of the etchant. That is, the problem can be solved by using the active species control material as the material to be etched and controlling the active species density according to the etching time or the active species monitoring result.

On the other hand, it is possible to suppress changes in etching characteristics over time by removing deposits on the surface in contact with plasma. That is, deposits attached to the plasma contact surface could be automatically removed by arranging the active species control material so as to surround the plasma and processing the sample while applying a voltage from the outside. In addition, the effect of improving the throughput by applying a voltage during sample processing was also obtained. Here, C ₄ F ₈ 1.5 mTorr, and μ-wave power 200 W, measured in the case of applying an arbitrary voltage to the aluminum plate was placed on the surface in contact with the C ₄ F ₈ plasma, the thickness of the deposited layer in step meter The results are shown in FIG. Although the deposit depends on the plasma density, it is possible to suppress the change in etching characteristics over time because the deposited film does not adhere by applying an appropriate voltage to the plasma interface.

According to the present invention, the following effects can be obtained.
Without using PFC or HFC gas, it is possible to generate active species necessary for etching and to etch the silicon oxide film while maintaining the conventional selectivity.

In the silicon oxide film process, the fluorine in the plasma CF ₂ converts, by using the plasma obtained by single species of the active species, but progresses etching reaction products is volatilized in the silicon oxide film, a silicon Selective etching in which etching stops due to residue on the nitride film is possible, and the problem of shoulder shaving of the nitride film due to the reduction in the selection ratio and the expansion of the process margin can be solved.

In addition, the change of active species between different materials during metal etching can be kept constant, and local shape abnormality can be suppressed.
Since the deposits on the plasma boundary surface can be removed, the change with time can be suppressed, and stable and good etching characteristics can be obtained with high throughput and long term.

(Example 1)
FIG. 1 is a side view of an etching apparatus equipped with the present invention, which uses ECR plasma, which is a method for generating a plasma using the interaction between a magnetic field and an electromagnetic wave. The reaction chamber 104 includes a microwave introduction window 103, a vacuum exhaust device 108, and a gas introduction pipe 109, and a sample stage 107 for installing a sample 106 is provided therein. The plasma generation mechanism includes a microwave oscillator 101, a waveguide 102, and an electromagnet 105. The sample stage 107 is connected to an RF power source 110 for accelerating ions incident on the sample 106. The RF power source 110 oscillates a radio wave having a frequency of several hundred kHz to several tens of MHz. The ions accelerated by the radio waves are incident on the sample 106, thereby promoting the etching reaction.

The gas is introduced into the reaction chamber 104 through the gas introduction pipe 109, and plasma 113 is generated. In particular, when performing oxide film etching, fluorocarbon gas plasma is used, and in this plasma, active species such as fluorine, CF ₁ , CF ₂ , and CF ₃ generated by dissociation exist. Here, when the fluorine is excessive in the plasma, for example, in the SAC processing, since both the nitride film and the oxide film are etched, it becomes difficult to perform selective etching. Therefore, in order to perform selective etching of SAC processing, it is a necessary condition to reduce fluorine in plasma. The apparatus has an active species control material 112 including a material that newly controls the active species. The active species control material 112 is temperature controlled by a heater 116, a cooling pipe 117, and a temperature control circuit 121. The temperature is monitored by a temperature monitor 114. The temperature control will be described in the fifth embodiment. In addition, this apparatus can monitor the plasma state with an emission spectrometer provided with a feedback circuit.

  It was newly confirmed that the conversion reaction can be further promoted by applying a voltage to the active species control material 112. As means for applying a voltage to the active species control material 112, an insulator 111 is installed between the active species control material 112 and the reaction chamber 104, and a voltage application circuit 115 including a blocking capacitor 117 and an AC power source 119 is provided. . Here, the blocking capacitor serves to block the direct current from the plasma, and Vdc is generated by the blocking capacitor, so that ions can be effectively accelerated. The voltage application circuit 115 may be a direct current power source if the material of the alternating current power source 119, the pulse power source, and the active species control material is a conductor. As the insulator 111, it is preferable to use alumina or silicon nitride that can withstand a temperature of about 400 ° C. Needless to say, it is not necessary to install the insulator 111 when no voltage is applied.

  When an insulator such as quartz or silicon nitride is used as the active species control material 112, a conductive plate 401 is inserted between the active species control material 112 and the insulator 111 as shown in FIG. The voltage introduction efficiency is better when the voltage application circuit 115 is connected to the conductive plate 401.

FIG. 3 shows the results of measuring the radical density of CF ₁ , CF ₂ , and CF ₃ when a negative DC voltage is applied to the carbon active species control material 112 in CF ₄ gas plasma. It was newly found that CF ₃ decreases and CF ₂ increases as the applied voltage increases. This is because an ion-assisted reaction occurs in which ions are incident on a state where a fluorocarbon-based adhesion layer is formed on the active species control material, and a local pseudo high temperature state is created by the energy to promote a chemical reaction. Due to that.

In general, it is known that a chemical reaction product under a high temperature condition is likely to generate an unstable molecule at room temperature where the number of bonded atoms is small. For example, chlorine atoms adsorbed on a silicon substrate generate SiCl ₂ by a chemical reaction with the underlying Si at a substrate temperature of 600 ° C., but are known to generate SiCl at 900 ° C. Therefore, it is presumed that CF ₂ is easily generated stably under the ion energy obtained in this experiment. That is, if carbon is used as the active species control material 112 in a fluorocarbon gas plasma and an ion assist reaction by applying a voltage is used, F and CF ₃ in the plasma can be converted to CF ₂ , and the activity in the plasma It shows that it is possible to control the species.

Further, the lower limit of the frequency of the high frequency voltage that can be applied to the active species control material is determined by the density of the plasma used. The plasma density used for etching is about 10 ¹¹ to 10 ¹² atoms / cm ³ , and the saturated ion current density I _e at that time is about 10 ⁻² to 10 ⁻⁴ A / cm ² . In general, when applying a high frequency to an electrode in plasma, a frequency of approximately I _e / (CV) or higher is required. This relational expression is derived qualitatively from the fact that the voltage change of the electrode dropped by the voltage application mechanism needs to change faster than the change of the amount of ions flowing in so as to cancel it. Here, C is a capacitance per unit area of about 10 ⁻¹¹ farad, and V is an applied voltage, which is about 10 ² volts. Therefore, in the above plasma used for etching, the frequency of the high frequency that can be applied must be 100 kHz or more. Regarding the upper limit value, the frequency at which ions can follow the voltage change and have an ion assist reaction effect was about 100 MHz. At this time, if a pulse power source and a DC power source are used as the voltage application circuit 115, the ion energy incident on the active species control material can be monochromatic, and the conversion reaction path can be unified. Selective generation of active species can be performed more efficiently. If the active species control material to be used is an insulator, the above effect can be obtained only by a pulse voltage. However, if it is a conductor, it is preferable to apply a DC voltage from the viewpoint of apparatus cost. Further, the frequency of the pulse used at this time varies depending on the electrostatic capacity of the system to which the voltage is applied. However, if the system has a capacity of about several tens of nF, 100 kHz or more is necessary.

  In the present invention, not only the fluorocarbon gas plasma but also a carbon-based gas or an organic resist is used as a mask causes an ion-assisted reaction on the deposit on the active species control material 112 to perform etching. It is possible to convert it into an active species effective for removal.

(Example 2)
An embodiment in which silicon oxide film etching is performed without using PFC or HFC gas will be described below. In the present embodiment of the ECR type microwave discharge plasma as shown in FIG. 1, no electrode facing the wafer is provided. Therefore, since the electrode facing the wafer cannot be made of carbon, in principle, etching using a gas not containing carbon is difficult.

However, as a result of using SiC as the active species control material 112, the introduced gas was flowed into the reaction chamber 104 as a gas containing Ar and SF ₆ and not containing carbon. Gas flow rate of the total set 20-300sccm, SF ₆ was changed in 1-10Sccm. The discharge pressure was set to 0.1-5 Pa. This introduced gas was turned into plasma and reacted with SiC to generate active species necessary for etching.

  In the wafer, a silicon oxide film was formed as a film to be etched, and the etching mask was made of photoresist. This photoresist used was a fine pattern formed by lithography. Further, a silicon nitride film and a silicon film were used as an underlayer for the oxide film.

  Under the condition that the etching rate of the SiC plate is 50 nm / min to 600 nm / min, the etching rate of the oxide film changes from 400 nm / min to 2000 nm / min, and the etching rate of the resist film changes from 500 nm / min to 80 nm / min. did. That is, the etching rate of the resist can be adjusted by the etching rate of the SiC wall electrode, and the selectivity can be increased. The etching rate of the silicon film also changed in the same manner as the resist. In order to most selectively etch the silicon nitride film, it is necessary to increase the etching rate of the SiC wall electrode. That is, with an etch rate of SiC 250 nm / min, the etch rate of the oxide film was 1000 nm / min, the etch rate of the silicon nitride film was 70 nm / min, and the selectivity of the silicon nitride film was 14.2.

  In this state, the effect of the temperature of the wall electrode and the wafer electrode was changed from −60 ° C. to 250 ° C., and the effect on the etching was examined. As a result, it was found that the silicon oxide film can be selectively etched with respect to the silicon nitride film by setting the temperature of the wafer electrode as high as possible. A particularly preferred temperature was 0 ° C. or higher. The selectivity of the silicon nitride film with respect to the SiC temperature of 200 ° C. was 5. As for the electrode on the wall surface, material deposition is likely to occur when the temperature is low. However, like the upper electrode, it is one of the factors that determine the etching rate of the electrode surface. Therefore, it is necessary to keep the temperature as constant as possible. In addition, the higher the temperature, the higher the etching rate, and the lower the temperature, the lower the efficiency of the active species conversion reaction. Therefore, it was possible to set and use a predetermined etching rate within the above temperature range. That is, from this example, when a plasma of a gas not containing carbon is used, carbon is contained in the solid surface that comes into contact with the plasma to generate an etching reaction of the solid, and the temperature of the solid is set to 0 ° C. or more in particular. Thus, it was clarified that the silicon oxide film can be etched at a high etching rate, and the effectiveness of the present invention was confirmed.

As an example of a gas that does not contain carbon, a mixed gas of Ar and SF ₆ is used here, but other inert gases Ne, Kr, and Xe may be used. In a gas containing fluorine, SF ₆ has a global warming potential. It is expensive and has a long lifetime, which is not desirable, but has the advantage of requiring very little consumption. Other than SF ₆ , F ₂ , HF, XeF ₂ , PF ₃ , BF ₃ , NF ₃ , SiF ₄ , halide fluorine fluoride ClF, ClF ₃ , fluorine bromide BrF, BrF ₃ , BrF ₅ , fluorine iodide IF ₅ is effective.

In addition to SiC, it has been found that a carbon-containing material such as a pyrolytic graphite plate, an organic resin film, SiCN, a diamond plate, Al ₄ C ₃ , or boron carbide may be used. Similarly, the active species necessary for etching could be formed even in the structure in which these carbides were formed on the surface of other materials.

(Example 3)
An example in which the same material as the material to be treated is used as the active species control material will be described. Use of such a material is effective in improving an abnormal shape that occurs when a laminated structure in which a sample is formed of a different material is etched in the same plasma. For example, FIG. 4A shows an etching of a laminated structure of resist 301, TiN304, Al303, and TiN304 formed on SiO ₂ 305 used in metal wiring processing in chlorine plasma with a conventional ECR plasma etching apparatus. It is an etching shape when processing is performed. Thus, in the conventional apparatus, the Al portion (notching portion) 302 that forms a boundary with the TiN 304 is abnormally shaved.

  FIG. 4B shows the change in the chlorine concentration in the plasma at this time. This graph shows that the chlorine concentration 307 in the notching portion suddenly decreases from a state where the chlorine density 306 at the time of TiN etching is large, and then changes to a state of a stable chlorine concentration 308 at the time of Al etching. This indicates that an abnormal shape occurs because the chlorine density in the plasma is excessive at the notching portion 302.

  Therefore, if Al is used as the active species control material 112 when performing this etching, the chlorine radical density 309 (FIG. 4 (b)) in which chlorine is consumed by Al on the wall surface during TiN304 etching can be obtained. Even if the etching layer changes to Al, rapid fluctuations in chlorine radicals can be suppressed. This is shown in FIG. In other words, it is considered that excessive active species stay when the active species are transferred to different layers between different materials. Therefore, when etching a layer that consumes less active species in etching the sample, a voltage is applied to the active species control material and the etchant is consumed by the active species control material, thereby stabilizing the amount of active species incident on the sample. It was possible to reduce the variation of the etchant.

  In addition, by using the same material as the mask material for the active species control material, changes in the amount of oxygen and carbon in the plasma generated from the etched mask material can be reduced, so that it is also stable in time. A sidewall protective film can be formed, and an etched shape without the undercut portion 310 (FIG. 4A) can be obtained.

The present invention can also be applied to other laminated structures, specifically, a resist-polysilicon laminated structure, a SiO ₂ —Si ₃ N ₄ structure, an Al—W—Al structure, a TiN—AlCu—TiN—Ti. structure, TiN-Cu-TiN structure, SiO ₂ mask -Pt structure, include poly-silicon -SiO ₂ structure, in which case, as the active species control materials, _{poly-silicon, Si 3 N 4, W,} Al, Cu It was confirmed that Pt and SiO ₂ should be used. In addition, if an active species control material containing the same material as the sample material is used, the effect of the present invention is certain, but another material whose reaction rate with the etchant proceeds at the same rate as the material to be processed is used. Even if applied, there is an effect.

  At this time, the variation rate of the etchant between different materials is about the area ratio between the etching surface and the active species control material. The surface of the sample to be processed when etching is made up of a mask part and a material part to be processed. By making the area of the plasma boundary part of the active species control material larger than the area of the small part, the active species It was possible to suppress the rate of change.

Example 4
An example of a method and mechanism for applying a voltage to the active species control material will be described. In the case where a high frequency is applied to the active species control material, if the area thereof is approximately the same as the area of the portion where the plasma potential is determined, the plasma potential 602 varies following the applied voltage 601 as shown in FIG. A phenomenon occurs. When the following phenomenon of the plasma potential 602 occurs, the sheath voltage between the plasma and the active species control material becomes 603, and the self-bias voltage 604 that is the direct current component is not applied. Since it becomes impossible to control the ion incident energy to the surface, a method for avoiding this is required. The policy of this method is to reduce the area of the active species control material to which the voltage is applied relative to the area of the portion where the plasma potential is determined, or increase the frequency to be applied and the amount of ions flowing in one cycle. A method of reducing or increasing the capacity of the blocking capacitor 118 is effective. For this purpose, a method of dividing the active species control material 112 into a plurality of mutually isolated blocks is preferable. This method is effective in avoiding the plasma potential following phenomenon because the total amount of ion current incident from the plasma during voltage application is reduced.

  An effective example is shown in FIG. FIG. 8 is a schematic diagram of the operation of the voltage application circuit in which the active species control material is divided into three blocks 802, 803, and 804 that are insulated from each other by the insulator 111 and the relay circuit 801 is incorporated. The area ratio between the block portion to which voltage is applied by the relay circuit 801 and the portion that determines the plasma potential (in this case, the ground potential) can be further reduced. At this time, the same effect can be obtained by using a plurality of small-area active species control materials.

  The operation of the relay circuit 801 when a high frequency voltage is applied to the active species control material divided into three at the timing shown in FIG. 7 is performed using time 1 in FIG. 8A and time 2 in FIG. 8B. I will explain. First, at time 1, the block a802 is connected to the high frequency power source 119, and the other blocks are grounded. Next, at time 2, the block b803 is connected to the high frequency power supply 119, and the other blocks are shown to be grounded. Similarly, at time 3, the block c804 is connected to the high frequency power supply 119, and the others are grounded. In this way, it is possible to efficiently prevent fluctuations in plasma potential by applying a voltage to a plurality of blocks sequentially and grounding blocks other than the voltage applied. In addition, although it divided | segmented into three here, if it is two or more, the same effect will be acquired.

  However, although the method of FIG. 8 is good enough to expect the effect of only removing the deposits, from the viewpoint of active species control, it is conceivable that the control efficiency decreases as the area decreases. Therefore, as shown in FIG. 9A, instead of the high frequency power supply 119, a multiphase high frequency power supply circuit 901 is connected, and high frequency having different phases is applied to each of the block a802, block b803, and block c804 divided into three blocks. By simultaneously applying (since block 802 a sine wave 902 having an initial phase of 0 °, block b803 having a sine wave 903 having an initial phase of 120 °, and block c804 having a sine wave 904 having an initial phase of 240 °), FIG. The plasma potential 602 as shown in FIG. In addition, since the voltage can be applied to a plurality of blocks at the same time, the active species control efficiency is improved as compared with the method of FIG. 8, and the deposit removal efficiency is improved. In order to implement this method, a plurality of high-frequency power sources having different phases may be used. It goes without saying that the same effect can be obtained by applying different frequencies to the divided blocks in order to control the energy of incident ions to the active species control material.

(Example 5)
An embodiment in which a temperature control mechanism is installed in the active species control material will be described with reference to FIG. The active species control in the present invention includes a method that utilizes the difference in stable products depending on the temperature under the progress of the chemical reaction and a method that controls the macroscopic temperature of the active species control material, both of which are effective. By keeping the temperature of the active species control material 112 constant regardless of the heating from the plasma during the operation of the apparatus, the desorptions of chemical species such as oxygen, water, and hydrogen from the active species control material 112 and the chemical reaction generation efficiency are always maintained. Can be constant. Examples of the means for keeping the temperature of the active species control material constant include a heater 116 as a heating means, a cooling pipe 117 as a cooling means, and a temperature monitor 114 as a temperature detection means. The temperature control circuit 121 adjusts the temperature of the heater 116 and the cooling pipe 117 based on the above. In this case, means such as an infrared lamp may be used as the heating means, and liquid nitrogen, water, or oil may be used as the cooling means.

(Example 6)
Example of a mechanism for detecting the amount of active species in plasma and the amount deposited on the active species control material 112 and controlling the voltage and frequency applied to the active species control material according to the plasma state and sample processing state Will be described. In the figure, 111 is an insulator, and 114 is a reaction chamber. First, FIG. 10 shows an embodiment provided with means for detecting the amount of active species control material deposited and the amount of sputtering. As a spatter amount detection means, a substance 1003 constituting an active species control material is vapor-deposited on a part of the quartz oscillator film thickness probe 1001, and a part of the substance 1003 is connected to a high-frequency power source 119 via a blocking capacitor 118. The structure is such that the same voltage as that of the active species control material 112 can be applied. Then, the amount adhering to or scraping off during the operation of the apparatus is captured by the change in the vibration frequency of the crystal, and the amount corresponding to the change in the vibration frequency is fed back to the voltage application circuit 115 by the feedback circuit 1002. By controlling the applied voltage and frequency so as to obtain an appropriate amount of cutting, the life of the active species control material 112 can be extended, and it is possible to cope with plasma conditions that change every moment.

  Further, as means for detecting a change in the amount of active species in the plasma, the emission spectrum 120 of FIG. 1 is installed, and an electric circuit for controlling the voltage applied to the active species control material is provided based on the increase or decrease of the detection result. As a result, the active species in the plasma can always be kept constant in real time.

FIG. 17 shows a high-frequency voltage applied according to the sample processing time and a frequency control mechanism. In order to perform time control, a control program is prepared in addition to the time control computer 1701, and the voltage and frequency applied to the active species control material 112 are temporally changed based on the programmed time sequence.
The digital signal corresponding to the voltage value and frequency from the control computer 1701 is converted into those analog voltages by the D / A converter 1702 and input to the voltage application circuit 115 to be applied to the active species control material 112, and Change the frequency. In this method, there are few mechanisms added to the reaction chamber, and arbitrary time control can be performed outside the reaction chamber. In other words, if the etching rate associated with sample processing and the film thickness of the material to be processed are known, the voltage value and frequency value associated with the processing time can be set freely by the program and realized at a relatively low cost. There is an advantage that you can. In order to realize the embodiment as described above, the voltage application mechanism 115 has a function capable of changing the voltage value or frequency applied to the active species control material 112 by an external input voltage or the like. is required.

(Example 7)
An embodiment in which the voltage of the direct current component (self-bias voltage) applied to the active species control material is set to −20 V or less will be described. First, in order to accelerate ions having a positive charge, it is necessary to apply at least a negative bias, that is, a voltage of 0 V or less. At this time, it is presumed that the chemical reaction region by the ion-assisted reaction is almost proportional to the range of incident ions. For example, it is known that the range R (Å) of Ar ions having energy E (eV) of 1000 eV or less has a relationship of R = 0.08 × E. At this time, it is necessary that at least one molecule participating in the reaction exists in the reaction region. Among the materials of the assumed active species mechanism, since the Si—O bond of quartz having a small interatomic distance is 1.62 Å, ion conversion requires at least 20 eV when performing active species conversion. Therefore, active species control can be advanced efficiently by setting the voltage applied to the active species control material to -20 V or less.

(Example 8)
An embodiment in which the voltage of the direct current component (self-bias voltage) applied to the active species control material is set to −50 V or more will be described. FIG. 5 shows the result of measuring the thickness of the deposit on the Al surface with a step gauge when an Al sample is placed in C ₄ F ₈ gas plasma using an ECR plasma apparatus and an AC voltage of 800 kHz is applied. is there. From this result, under conditions of 1.5 mTorr and μW power of 200 W, a surface is obtained in which the self-bias voltage, which is the DC component of the sheath voltage, is −45 V, no deposits adhere, and the underlying Al is not etched. I understand that In consideration of the error in the surface roughness of the Al sample used for the measurement, it is considered that there are conditions under which the active species control material is not etched when the applied voltage is set to −50 V or more. Further, such a voltage varies depending on the sputter threshold voltage unique to the attached active species, the amount of active species incident on the active species control material from the plasma, and the plasma density. It is also possible to adjust using.

  Therefore, when the applied voltage is between 0V and -50V, there is a voltage that can sputter only carbon-based deposits. By applying this voltage during sample processing, the effect of controlling the active species can be achieved simultaneously with the plasma boundary. Since deposits on the surface can be removed, oxygen cleaning can be shortened or omitted, leading to an improvement in total throughput. At this time, it is also conceivable to perform the sample processing time and the voltage application time to the active species control material at different timings. Further, by introducing a cleaning gas (oxygen, argon, etc.) with the above apparatus, the plasma interface can be cleaned by the same method as described above.

Example 9
Taking an example of silicon oxide film etching in a UHF wave plasma etching apparatus using a magnetic field, an effective method of using a gas according to the present invention will be described with reference to FIG. In this embodiment, ClF ₃ is used as a gas not containing carbon. Ne, Ar, Kr, and Xe were mixed as an inert gas. For gases containing fluorine, SF ₆ and NF ₃ have a high global warming potential and a long lifetime, which is not desirable, but it has the advantage of requiring very little consumption, but ClF ₃ has the same effect. there were.

In this embodiment, the UHF wave radiation antenna 71 is opposed to the wafer, and the material thereof is a pyrolytic graphite plate. It has been found that the pyrolytic graphite plate may be a carbon-containing material such as organic resin film, SiCN, diamond plate, Al ₄ C ₃ , boron carbide in addition to SiC. In addition, a structure in which these carbides are formed on the surface is also effective. When a low-path filter was installed outside the UHF wave radiating antenna 71 and an RF power supply was installed, the counter electrode structure was formed, and the generated particles were efficiently incident on the sample, and the effect of active species control could be increased.

  The total gas flow rate was set to 50-500 sccm, and SF6 was varied from 1-10 sccm. The discharge pressure was set to 0.5-5 Pa. The UHF wave is transmitted from the plasma discharge UHF wave power source 74 through the coaxial cable 79 and input from the radiation antenna 71 to generate plasma. The lower wafer electrode 107 was supplied with rf electric power 110 for accelerating ions in the plasma. The distance between the upper and lower electrodes was set to 10-200 mm, and a mechanism capable of applying rf power 119 to the pyrolytic graphite plate as the active species control material 112 was provided. Reference numeral 78 in the figure denotes a magnet. As the material for the wall surface, SiC surface-treated as a substance containing carbon was used. When power is supplied to this SiC, the SiC is etched by the plasma.

  In the wafer, similarly, a silicon oxide film is formed as a film to be etched, and the etching mask is made of photoresist. A photolithographic resist having a fine pattern formed thereon was used. Further, a silicon nitride film and a silicon film were used as an underlayer for the oxide film.

  When the oxide film is etched under the condition that the etching rate of the pyrolytic graphite plate of the upper electrode is 50 nm / min to 600 nm / min, the etching rate of the oxide film changes from 400 nm / min to 1400 nm / min, and the etching rate of the resist film Changed from 600 nm / min to 60 nm / min. That is, the etching rate of the resist can be adjusted by the etching rate of the SiC wall electrode, and the selectivity can be increased. The etching rate of the silicon film also changed in the same manner as the resist. In order to most selectively etch the silicon nitride film, it is necessary to increase the etching rate of the SiC wall electrode.

In this state, the temperature effect of the upper and lower electrodes and the wall surface electrode was changed from −60 ° C. to 250 ° C., and the effect on the etching was examined. As a result, it was found that the silicon oxide film can be selectively etched with respect to the silicon nitride film by setting the temperature of the wafer electrode as high as possible. A particularly preferred temperature was 0 ° C. or higher. The temperature of the upper electrode was one of the factors determining the etching rate of the electrode surface. Therefore, it is necessary to keep the temperature as constant as possible. In addition, the higher the temperature, the higher the etching rate, and the lower the temperature, the lower the efficiency of the active species conversion reaction by the upper electrode. Therefore, it can be used by setting a predetermined etching rate within the above temperature range. As for the electrode on the wall surface, material deposition is likely to occur when the temperature is low. However, like the upper electrode, it is one of the factors that determine the etching rate of the electrode surface. Therefore, it is necessary to keep the temperature as constant as possible. In addition, the higher the temperature, the higher the etching rate, and the lower the temperature, the lower the efficiency of the active species conversion reaction by the upper electrode. Therefore, it was possible to set and use a predetermined etching rate within the above temperature range. That is, from this example, when ClF ₃ is used as a gas not containing carbon, carbon is contained in the solid surface in contact with the plasma to generate an etching reaction of the solid, and the temperature of the solid is changed from −60 ° C. to 250 ° C. It was clarified that the silicon oxide film can be etched at a high etching rate by controlling the temperature to 0 ° C., and the effectiveness of the present invention was confirmed.

(Example 10)
FIG. 14 shows an embodiment of the present invention using surface wave excitation type plasma as a plasma generator. Electromagnetic waves from the waveguide 1402 give plasma energy through the dielectric 1401 to generate plasma. Other mechanisms and effects are the same as when the ECR type is used as the plasma generation mechanism.

(Example 11)
An example in which carbon is used as the material of the active species control material and SAC processing is performed by applying the present invention will be described. FIG. 16A shows the structure of the sample before performing SAC processing. A gate electrode 1504 made of polysilicon is formed on a silicon substrate 1505. The SAC process is an oxide film process that forms a contact hole by etching the oxide film 1502 using the nitride film 1503 as a stopper layer, and is a promising method when forming a contact hole in a DRAM of 256M or later. Reference numeral 1501 denotes a resist. There is no concept of active species control or the mechanism is not capable of independent control, for example, using a magnetic field microwave high-density plasma etching apparatus, C ₄ F ₈ 5 mTorr, microwave power 1100 W If etching is performed under the conditions, as shown in FIG. 16 (b), the shoulder portion of the nitride film is scraped to generate 1506, resulting in failure to maintain insulation of the polysilicon gate 1504, and contact as shown in FIG. 16 (c). A trade-off that etching stop 1507 occurred at the bottom of the hole occurred, and the process window for good selective etching was narrow.

By applying the present invention, the deposited film composition important for the etching reaction of the oxide film can be made suitable for selective etching. That is, the oxide film in the plasma reduces the fluorine etches both nitride film, which can be converted to CF ₂ suitable for selective etching, suppress scraping shoulder and residual deposits on nitride film, oxide film Then, it is possible to promote a good surface reaction such that etching proceeds.
Therefore, when SAC processing is performed using this method, a good etching shape as shown in FIG. 16 (d) can be obtained.

(Example 12)
An embodiment in which a silicon oxide film is etched by introducing a gas not containing carbon into a compound with a parallel plate etching apparatus will be described with reference to FIG. In this embodiment, a pyrolytic graphite plate is used for the electrode 1202 facing the wafer 106. As an example of a gas not containing carbon, a mixed gas of Ar and SF ₆ was used as the discharge gas. This mixed gas was supplied from above through the gas introduction hole of the pyrolytic graphite plate. The total gas flow rate was set to 100 to 500 sccm, and SF ₆ was changed from 1 to 10 sccm. The discharge pressure was set to 1 to 5 Pa. An rf power 1201 is applied to the upper electrode to generate plasma. The lower electrode 107 was supplied with rf power 110 for accelerating ions in the plasma. The distance between the upper and lower electrodes was varied from 5 to 50 mm.

  As the wafer, a resist, a silicon oxide film, a silicon film, and a silicon nitride film were used. Here, the silicon oxide film was etched using the photoresist as a mask.

  When the etching rate of the pyrolytic graphite plate of the upper electrode is changed from 100 nm / min to 1000 nm / min, the etching rate of the oxide film is changed from 500 nm / min to 2000 nm / min, and the etching rate of the resist film is It changed from 800 nm / min to 90 nm / min. The etching rate of the resist can be adjusted by the etching rate of the pyrolytic graphite plate, and the selectivity can be kept large. The etching rate of the silicon film also changed in the same manner as the resist. Therefore, it has been found that the etching rate of the pyrolytic graphite plate needs to be increased by 100 nm / min or more in order to most selectively etch the silicon oxide film. That is, from this example, the silicon oxide film can be etched at a high etching rate with a gas containing no carbon, and the effectiveness of the present invention was confirmed.

(Example 13)
In this embodiment, an example of etching using the apparatus in which the third electrode 112 is installed near the wall surface of the plasma processing chamber in the parallel plate type plasma processing apparatus as in Embodiment 12 will be described with reference to FIG. To do. As the third electrode, surface-treated SiC 112 is used, and when power 119 is applied to the SiC, the SiC is etched by the plasma. In addition, the temperature of SiC 112 is adjusted by a heater 116 and a cooling pipe 117. Other than that is the same as Example 12.

  Under the condition that the etching rate of the pyrolytic graphite plate of the upper electrode 1202 is from 100 nm / min to 400 nm / min, power 119 is applied to the SiC 112, and the resist, silicon oxide film, silicon on the wafer according to the etching rate of the SiC wall electrode Changes in the etching rate of the film and the silicon nitride film were measured. As a result, as the SiC electrode etching rate increased, the oxide film etching rate changed from 500 nm / min to 1500 nm / min, and the resist film etching rate changed from 300 nm / min to 60 nm / min. That is, the etching rate of the resist can be adjusted by the etching rate of the SiC wall electrode, and the selectivity can be kept large. The etching rate of the silicon film also changed in the same manner as the resist. It has been found that the etching rate of the SiC wall electrode needs to be increased in order to most selectively etch the silicon nitride film. In other words, from this example, when using plasma of a gas that does not contain carbon, the silicon oxide film is etched at a high etching rate by containing carbon on the solid surface in contact with the plasma and generating an etching reaction of this solid. It was clear that this was possible and the effectiveness of the present invention was confirmed.

  There are several effective means for applying power to the wall of the plasma processing chamber. One of them was a method in which the wall surface was divided into several parts and operated with different bias powers. Second, there is an effect even if the wafer bias power supply is shared between the wafer and the wall surface by changing the phase of the power.

  Even in a very narrow situation where the distance between the upper and lower electrodes is 30 mm or less, the wall surface bias application method was effective.

  In order to control the etching rate of the wall electrode with high accuracy, it is necessary to control the waveform and frequency of the bias power on the wall surface, and the ion energy distribution can be set to be small and uniformly etched.

(Example 14)
The silicon oxide film etching with a parallel plate etching apparatus using a magnetic field will be described with reference to FIG. In this embodiment, a pyrolytic graphite plate is used for the electrode 1202 facing the wafer 106. As the discharge gas, a mixed gas of Ar and SF ₆ was used. This mixed gas was supplied from above through the gas introduction hole of the pyrolytic graphite plate. The total gas flow rate was set to 20 to 500 sccm, and SF ₆ was changed from 1 to 10 sccm. The discharge pressure was set to 0.1-5 Pa. The distance between the upper and lower electrodes was set to 10 to 200 mm. A surface-treated SiC 112 was used in the vicinity of the wall surface. When power is supplied to this SiC, the SiC is etched by the plasma. Other than that is the same as Example 12.

  Under the condition that the etching rate of the pyrolytic graphite plate of the upper electrode is 50 nm / min to 600 nm / min, power is applied to SiC, and the resist, silicon oxide film, silicon film, silicon on the wafer according to the etching rate of this SiC electrode Changes in the etching rate of the nitride film were measured. As a result, as the etching rate of the SiC wall electrode increased, the etching rate of the oxide film changed from 400 nm / min to 1600 nm / min, and the etching rate of the resist film changed from 500 nm / min to 60 nm / min. That is, the etching rate of the resist can be adjusted by the etching rate of the SiC wall electrode, and the selectivity can be kept large. The etching rate of the silicon film also changed in the same manner as the resist. It has been found that the etching rate of the SiC wall electrode needs to be increased in order to most selectively etch the silicon nitride film. In other words, from this example, when using plasma of a gas that does not contain carbon, the silicon oxide film is etched at a high etching rate by containing carbon on the solid surface in contact with the plasma and generating an etching reaction of this solid. It was clear that this was possible and the effectiveness of the present invention was confirmed.

  As in Example 2, there were some effective means for applying power to the wall surface of the plasma processing chamber. One of them was a method in which the wall surface was divided into several parts and operated with different bias powers. Second, there is an effect even if the wafer bias power source is shared by changing the phase of the power between the wafer and the wall surface. The wall surface bias application method was effective even in a very narrow situation where the distance between the upper and lower electrodes was 30 mm or less, but it was particularly effective under the condition where the electrode distance exceeded 30 mm.

(Example 15)
In the present embodiment, a method for etching while controlling the temperature of the electrode by further providing a temperature adjusting mechanism 48 in the embodiment 14 will be described with reference to FIG.

  The effect of the temperature on the upper and lower electrodes and the electrode on the wall surface was changed from -60 ° C. to 250 ° C. to examine the effect on the etching. As a result, it was found that the silicon oxide film can be selectively etched with respect to the silicon nitride film by setting the temperature of the wafer electrode as high as possible. A particularly preferred temperature was 0 ° C. or higher. The temperature of the upper electrode was one of the factors determining the etching rate of the electrode surface. Therefore, it is necessary to keep the temperature as constant as possible. In addition, the higher the temperature, the higher the etching rate, and the lower the temperature, the lower the efficiency of the active species conversion reaction by the upper electrode. Therefore, it can be used by setting a predetermined etching rate within the above temperature range. As for the electrode on the wall surface, material deposition is likely to occur when the temperature is low. However, like the upper electrode, it is one of the factors that determine the etching rate of the electrode surface. Therefore, it is necessary to keep the temperature as constant as possible. In addition, the higher the temperature, the higher the etching rate, and the lower the temperature, the lower the efficiency of the active species conversion reaction by the upper electrode. Therefore, it was possible to set and use a predetermined etching rate within the above temperature range. That is, from this example, when a plasma of a gas not containing carbon is used, carbon is contained in the solid surface in contact with the plasma to generate an etching reaction of the solid, and the temperature of the solid is changed from −60 ° C. to 250 ° C. It was confirmed that the silicon oxide film can be etched at a high etching rate by controlling the above.

(Example 16)
The silicon oxide film etching in the inductively coupled rf wave discharge etching apparatus according to the present invention will be described with reference to FIG. The wafer 106 is placed on a wafer table 107 that also serves as a bias high-frequency application lower electrode, and the wafer table 107 is connected to a bias high-frequency power source 110. In this embodiment, unlike Embodiments 12 to 15, an electrode facing the wafer is not installed, and an insulating window 51 is arranged. SiC was used as the active species control material 112 in the vicinity of the wall surface. A bias application power source 119 is connected to the SiC. As in Example 14, the total gas flow rate was set to 20 to 500 sccm, and SF ₆ was varied from 1 to 10 sccm. The discharge pressure was set to 0.3 to 5 Pa. The rf power was supplied from a plasma discharge high frequency power supply 54 to an antenna formed on the coil in the discharge part of the plasma processing chamber, and plasma was generated in the discharge window plate 58 or discharge tube made of alumina or quartz.

  The other conditions are the same as in Example 14. As a result, similarly to Example 4, the etching rate of the resist could be adjusted by the etching rate of the SiC wall surface electrode, and the selection ratio could be kept large. The etching rate of the silicon film also changed in the same manner as the resist. It has been found that the etching rate of the SiC wall electrode needs to be increased in order to most selectively etch the silicon nitride film.

  Further, as in Example 15, it was found that the silicon oxide film can be selectively etched with respect to the silicon nitride film by setting the temperature of the wafer electrode as high as possible.

(Example 17)
The silicon oxide film etching in the UHF wave plasma etching apparatus not using a magnetic field according to the present invention will be described with reference to FIG. In this embodiment, a pyrolytic graphite plate is used as the electrode 71 facing the wafer.

The introduced gas was a mixed gas of SF ₆ and Ar, the total gas flow rate was set to 50 to 500 sccm, and SF ₆ was varied from 1 to 10 sccm. The discharge pressure was set to 0.5 to 5 Pa. The distance between the upper and lower electrodes was set to 10 to 200 mm. A surface-treated SiC 76 was used as the active species control mechanism in the vicinity of the wall surface of the plasma processing chamber. When power is supplied to this SiC, the SiC is etched by the plasma.

  The wafer used was a silicon nitride film, silicon film, silicon oxide film and photoresist formed on a substrate.

  The etching rate of the oxide film changes from 400 nm / min to 1400 nm / min under the condition that the etching rate of the pyrolytic graphite plate of the upper electrode is 50 nm / min to 600 nm / min, and the etching rate of the resist film changes from 600 nm / min. It changed to 60 nm / min. That is, the etching rate of the resist can be adjusted by the etching rate of the SiC wall electrode, and the selectivity is increased. The etching rate of the silicon film also changed in the same manner as the resist. In order to most selectively etch the silicon nitride film, it is necessary to increase the etching rate of the SiC wall electrode.

  Further, as in Example 15, it was found that the silicon oxide film can be selectively etched with respect to the silicon nitride film by setting the temperature of the wafer electrode as high as possible.

(Example 18)
Taking an example of silicon oxide film etching in a UHF wave plasma etching apparatus using a magnetic field, an effective method of using a gas according to the present invention will be described with reference to FIG. In this embodiment, ClF ₃ is used as a gas not containing carbon. Ne, Ar, Kr, and Xe were mixed as an inert gas. Similar to fluorine-containing gas, ClF ₃ has a high global warming potential and a long lifetime, which is not preferable, but has the advantage of requiring very little consumption. Other conditions are the same as in Example 17.

As a result, even when ClF ₃ is used, the same effect as in Example 17, that is, the effect that the silicon oxide film can be etched at a high etching rate by controlling the temperature of the active species control material from −60 ° C. to 250 ° C. Obtained.

(Example 19)
The silicon oxide film was etched using a gas containing a small amount of carbon as an etching gas in addition to ClF ₃ in an inductively coupled high-frequency discharge plasma etching apparatus.

  In this example, since the inductive coupling type is used, an electrode facing the wafer is not installed, but as a result of using SiC for the electrode 112 (FIG. 13) in the vicinity of the wall surface, the effect of the present invention was recognized. However, it is quite difficult to selectively etch the silicon oxide film with respect to the silicon nitride film. The present embodiment is a method for compensating for this. As the gas containing carbon, in addition to C, a gas containing any of H, F, and Cl may be used.

The total gas flow rate was set to 20 to 500 sccm, and ClF ₃ was changed from 0 to 10 sccm. Chloroform was used for a small amount of additive gas. The amount introduced was set so as not to exceed ClF ₃ . The discharge pressure was set to 0.3 to 5 Pa. The rf power was supplied to the antenna formed on the coil in the discharge part of the plasma processing chamber, and plasma was generated in a discharge window plate or discharge tube made of alumina or quartz. The wafer electrode was supplied with rf power for accelerating ions in the plasma.

  The wafer used was a silicon nitride film, silicon film, silicon oxide film, and photoresist formed on a substrate.

  Assuming that the SiC etching rate is 50 nm / min to 600 nm / min, the oxide film etching rate changes from 400 nm / min to 1600 nm / min, and the resist film etching rate changes from 500 nm / min to 60 nm / min. did. The etching rate of the silicon nitride film is 40 to 200 nm / min, and it is clear that the addition of chloroform improves the selectivity by 20% or more, and the effect of adding a small amount of gas is large. This is an example where the effectiveness is further utilized. That is, by adding a small amount of gas containing carbon, the etching rate of the resist can be adjusted, and the selectivity is increased. This carbon-containing gas is effective when it is flowed at 1% or less, preferably about 0.4 to 0.8% of the total gas flow rate. That is, in this embodiment, the above-described effect is obtained when a gas containing carbon is flowed at 5 sccm or less. The etching rate of the silicon film also changed in the same manner as the resist. The etching of the silicon nitride film could be selectively performed very effectively.

In this state, the temperature effect of the upper and lower electrodes and the wall surface electrode was changed from −60 ° C. to 250 ° C., and the effect on the etching was examined. As a result, the temperature of the wafer electrode is about 10 ° C. at which the silicon oxide film can be selectively etched with respect to the silicon nitride film when the carbon-containing gas is added compared to when the carbon-containing gas is not added. It turned out that it may be low. A particularly preferable temperature was −10 ° C. or higher. The temperature of the upper electrode was one of the factors determining the etching rate of the electrode surface. Therefore, it is necessary to keep the temperature as constant as possible. In addition, the higher the temperature, the higher the etching rate, and the lower the temperature, the lower the efficiency of the active species conversion reaction by the upper electrode. Therefore, it can be used by setting a predetermined etching rate within the above temperature range. As for the electrode on the wall surface, material deposition is likely to occur when the temperature is low. However, like the upper electrode, it is one of the factors that determine the etching rate of the electrode surface. Therefore, it is necessary to keep the temperature as constant as possible. In addition, the higher the temperature, the higher the etching rate, and the lower the temperature, the lower the efficiency of the active species conversion reaction by the upper electrode. Therefore, it was possible to set and use a predetermined etching rate within the above temperature range. That is, from this example, when ClF ₃ is used as a gas not containing carbon, and the gas containing carbon is added with a gas containing any of H, F and Cl in addition to C, In addition, carbon is contained in the solid surface in contact with the plasma to generate an etching reaction of the solid, and the temperature of the solid is controlled from -60 ° C. to 240 ° C., so that the silicon oxide film is highly selected at a high etching rate. It was clarified that etching can be performed by the ratio, and the effectiveness of the present invention was confirmed.

(Example 20)
The effective use of the gas according to the present invention will be described by taking silicon oxide film etching in an inductively coupled high frequency discharge plasma etching apparatus as an example. In this embodiment, ClF ₃ is used as an etching gas, but in addition, a gas containing oxygen, for example, O ₂ is used. At the same time, as in Example 19, a gas containing a trace amount of carbon may be used. Any of Ne, Ar, Kr, and Xe was mixed as an inert gas. Of gases containing fluorine, OF ₆ , NF ₃ , and ClF ₃ can also be used. The important point of this embodiment is that O ₂ , CO, CO ₂ , NO, NO ₂ , H ₂ O, etc. can be used.

  In this example, as a result of using pyrolytic graphite as an electrode in the vicinity of the wall surface, the effect of the present invention was recognized. However, it is quite difficult to selectively etch the silicon oxide film with respect to the silicon nitride film. The present embodiment is a method for compensating for this. As the gas containing carbon, in addition to C, a gas containing any of H, F, and Cl may be used.

The total gas flow rate was set to 20 to 500 sccm, and ClF ₃ was changed from 1 to 10 sccm. The additive gas traces were using O _2. The amount introduced was set so as not to exceed ClF ₃ . The discharge pressure was set to 0.3 to 5 Pa. The rf power was supplied to the antenna formed on the coil in the discharge part of the plasma processing chamber, and plasma was generated in a discharge window plate or discharge tube made of alumina or quartz. The wafer electrode was supplied with rf power for accelerating ions in the plasma. In this embodiment, unlike the previous examples, carbon oxide gases such as CO, CO ₂ , C ₃ O ₂ , and C ₅ O ₂ are formed as a result of this etching reaction. As a result, it becomes extremely effective to selectively etch the silicon oxide film with respect to the silicon nitride film, and the effectiveness of the present invention can be further enhanced.

  The wafer used was a silicon nitride film, silicon film, silicon oxide film, and photoresist formed on a substrate.

  The etching rate of the oxide film changes from 400 nm / min to 1600 nm / min under the condition that the etching rate of graphite of the upper electrode is 50 nm / min to 600 nm / min, and the etching rate of the resist film changes from 500 nm / min to 60 nm / min. Changed. Further, the etching rate of the silicon nitride film is 30 to 150 nm / min, and the selectivity is improved by 15% or more by adding oxygen, and it is clear that the effect of adding a small amount of gas is large, and the effectiveness of the present invention is further improved. It was an example to be utilized. That is, by adding a small amount of a gas containing oxygen, the etching rate of the resist can be adjusted, and the selectivity is increased. The etching rate of the silicon film also changed in the same manner as the resist. The etching of the silicon nitride film could be selectively performed very effectively.

In the above-described embodiments, pyrolytic graphite and SiC are used as the carbon-containing substance. However, other carbon-containing materials such as organic resin films, SiCN, diamond plates, Al ₄ C ₃ , and boron carbide can be used. Good. In addition, a structure in which these carbides are formed on the surface is also effective.

  In the above-described embodiments, Ar is used as a gas not containing carbon, but other inert gases Ne, Kr, and Xe may be used.

In the above-described embodiment, SF ₆ or ClF ₃ is used as the fluorine-containing gas. However, although the global warming potential is high and the lifetime is not favorable, there is an advantage that only a very small amount of consumption is required. is there. In any _{other, F 2, HF, XeF 2} , PF 3, BF 3, NF 3, SiF 4, fluorine chloride halide ClF, bromine fluoride BrF, BrF _3, BrF _5, an iodide fluorine IF ₅ Also good.

It is a figure which shows the cross section of the plasma etching apparatus carrying the active species control material of Example 1 of this invention. Al to the active species control material is a diagram showing the fluorine and CF ₂ density in CF ₄ plasma when using SiO _2, C. In CF ₄ gas plasma, a diagram illustrating a CF _1, the change in radical density CF _2, CF ₃ at the time of applying a negative DC voltage to the active species control material carbon. It is the figure which showed the shape when the laminated structure of a resist-TiN-Al-TiN was etched with the conventional ECR plasma etching apparatus, and the change of the chlorine concentration in the plasma at that time. Is a diagram showing the thickness of the deposited layer when a voltage is applied to the aluminum plate was placed on the surface in contact with the C ₄ F ₈ plasma. FIG. 5 is a waveform diagram of a plasma potential, an applied voltage, a plasma sheath voltage, and a self-bias voltage when the area of an active species control material is approximately the same as the area of a portion that determines the plasma potential. It is a figure which shows the example of the timing which applies a voltage to each block at the time of dividing an active species control material into three. It is the schematic of operation | movement of the voltage application circuit incorporating the relay circuit at the time of dividing an active species control material into three. It is a block diagram when a multi-phase power supply circuit is connected, and a waveform diagram of plasma potential, applied voltage, plasma sheath voltage, and self-bias voltage. It is a figure which shows the Example of the means to detect the adhesion amount or sputter | spatter amount to an active species control material. It is the schematic of the ECR type | mold UHF wave plasma etching apparatus using the gas composition and active species control material by this invention. It is sectional drawing of the etching apparatus which applies capacitive coupling type plasma to a plasma generation mechanism and mounts this invention. It is sectional drawing of the etching apparatus which applies inductively coupled plasma to a plasma generation mechanism, and mounts this invention. It is sectional drawing of the etching apparatus which applies surface wave excitation type plasma to a plasma generation mechanism, and mounts this invention. It is sectional drawing of the etching apparatus which applies a magnetic field parallel plate plasma to a plasma generation mechanism, and mounts this invention. A diagram showing a sample structure before performing SAC processing by oxide film etching, a diagram showing a shoulder shaving state at the time of SAC processing in the conventional method, a diagram showing an etching stop state at the time of SAC processing in the conventional method, and the case of using the present invention It is a figure showing the etching shape at the time of performing SAC processing in. It is a figure which shows the control mechanism of the high frequency voltage and frequency applied by sample processing time. It is a figure which shows having inserted the electrically conductive board between the active species control material and the insulator, and having connected the voltage application circuit to the electrically conductive board. It is sectional drawing of the etching apparatus which applies a magnetic field parallel plate plasma to a plasma generation mechanism, and mounts this invention. It is sectional drawing of the etching apparatus which applies parallel plate plasma to a plasma generation mechanism and mounts this invention. It is a figure which shows the process shape at the time of applying this invention and performing the metal wiring process of TiN-Al-TiN.

Explanation of symbols

48: Temperature control mechanism, 51: Upper window, 54: High frequency power supply, 58: Coiled antenna, 71: Upper electrode, 74: UHF wave power supply, 78 ... Magnet, 79 ... Coaxial cable, 101 ... Microwave oscillator, 102 ... Waveguide, 103 ... Microwave introduction window, 104 ... Reaction chamber, 105 ... Electromagnet, 106 ... Sample, 107 ... Sample stand, 108 ... Vacuum exhaust device, 109 ... Gas introduction tube, 110 ... RF power supply, 111 ... Insulator 112 ... Active species control material, 113 ... Plasma, 114 ... Temperature monitor, 115 ... Voltage application circuit, 116 ... Heater, 117 ... Cooling tube, 118 ... Blocking capacitor, 119 ... AC power supply, 120 ... Light emission provided with feedback circuit Spectrometer 121 ... Temperature control circuit 301 ... Resist 302 ... Notch part 303 ... Aluminum 304 ... Nitriding Tan, 305 ... SiO _2, 306 ... (abnormal shape occurs) chlorine concentration at the titanium nitride etch, 307 ... chlorine density in notching portions, 308 ... stable chlorine concentration during aluminum etching, at 309 ... titanium nitride etch Chlorine density (when the present invention is applied), 310 ... undercut portion, 401 ... conductive plate, 601 ... applied voltage, 602 ... plasma potential, 603 ... sheath voltage, 604 ... self-bias voltage, 801 ... relay circuit, 802 ... block a , 803..., Block b, 804... Block c, 901... Multiphase high frequency power supply circuit, 902... Sine wave with initial phase of 0 degree, 903. ... sheath voltage to block a, 906 ... sheath voltage to block b, 907 ... sheath electricity to block c , 1001 ... Quartz crystal thickness meter probe, 1002 ... Feedback circuit, 1003 ... Substance constituting the active species control material, 1201 ... High frequency power source, 1202 ... Ground counter electrode, 1401 ... Dielectric, 1402 ... Waveguide, 1501 ... resist, 1502 ... oxide film, 1503 ... nitride film, 1504 ... polysilicon gate, 1505 ... silicon substrate, 1506 ... nitride shoulder shaving part, 1507 ... etching stop part, 1701 ... time control computer, 1702 ... D / A converter.

Claims (6)

Installing a wafer in the processing chamber;
Introducing a gas into the processing chamber;
The first and second active species provided in the processing chamber and provided along the direction perpendicular to the etching surface of the wafer, or the first and second active species when the control material of the insulator against the conductive plate each disposed between the first and second active species control material and the insulating film, a step of applying respective different phases of the high-frequency voltage,
Converting the gas into plasma and reacting the gas with the first and second active species control materials;
And a step of generating a plasma atmosphere in which active species are controlled by the reaction in the processing chamber and etching the wafer in the plasma atmosphere.   2. The method of manufacturing a semiconductor device according to claim 1, wherein the high-frequency voltages applied to the first and second active species control materials have different frequencies.   2. The method of manufacturing a semiconductor device according to claim 1, wherein the first and second active species control materials are the same material. Wherein the first and second active species control material, carbon, Si, _{polysilicon, Si 3 N 4, W,} Al, Cu, Pt, according to claim 1, wherein a is either SiO ₂ A method for manufacturing a semiconductor device. Installing a wafer in the processing chamber;
Introducing gas into the processing chamber;
The first and second active species provided in the processing chamber and provided along the direction perpendicular to the etching surface of the wafer, or the first and second active species When the control material is an insulator, applying a high-frequency voltage to the first and second conductive plates respectively disposed between the first and second active species control materials and the insulating film; ,
While the high-frequency voltage is applied to the first active species control material or the first conductive plate, the second active species control material or the second conductive plate is grounded, and the second active species control material or the first conductive plate is grounded. Grounding the first active species control material or the first conductive plate while the high frequency voltage is applied to the active species control material or the second conductive plate;
Converting the gas into plasma and reacting the gas with the first and second active species control materials;
And a step of generating a plasma atmosphere in which active species are controlled by the reaction in the processing chamber and etching the wafer in the plasma atmosphere . Wherein the first and second active species control material, carbon, Si, _{polysilicon, Si 3 N 4, W,} Al, Cu, Pt, according to claim 5, wherein a is either SiO ₂ A method for manufacturing a semiconductor device.

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