JP3854019B2 - Manufacturing method of semiconductor device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a dry etching apparatus and a dry etching method used for microfabrication of a semiconductor device, and more particularly to a dry etching apparatus and a dry etching method that realize high-precision dry etching processing of a silicon oxide film.
[0002]
[Prior art]
In a semiconductor device, an insulating film (SiO2) formed on a transistor structure and between wirings is used to electrically connect transistors formed on a wafer to metal wirings and between metal wirings.₂A contact hole is formed by a dry etching method, and an electrical conductor is filled in the contact hole. In dry etching, an etching gas is introduced into a vacuum vessel, a high frequency bias or μ wave is applied to the gas to generate plasma, and the oxide film is selectively etched by active species and ions generated in the plasma to form contact holes. Form. At the time of this etching, a resist thin film to which the hole pattern is transferred is formed on the oxide film. In this contact hole processing, it is necessary to etch the oxide film selectively with respect to the resist film, the wiring layer under the contact hole, and the silicon forming the transistor. In addition, in the dry etching method in which the gate electrode of the field effect transistor formed on the wafer is covered with a second insulating film made of a material different from the wiring layer, and the source and drain regions and the wiring layer are connected, Since the second insulating film appears in the hole, the selectivity to the second insulating film is also required. This contact processing is called self-aligned contact (SAC) processing, and a silicon nitride film is used as the second insulating film.
[0003]
The contact hole is processed by CF in the etching apparatus.₄, CHF₃, C₄F₈Etching is performed under the condition that high-frequency plasma discharge is performed under a gas pressure condition of 4 Pa to 10 Pa, and a Vpp voltage of 1.5 to 2.0 kV is applied to the wafer. When the oxide film between the wiring layers is thick and the aspect ratio (depth / diameter) of the contact hole is high, oxygen gas is added to improve the hole opening property, and in SAC processing, CO is added to increase the selectivity to the nitride film. Gas has been added.
[0004]
[Problems to be solved by the invention]
However, in the conventional etching apparatus, if the etching conditions such as the gas pressure and the high frequency power necessary for plasma generation are determined, the plasma density and the electron temperature are determined.₂And the amount of ions generated is fixed. In plasma, CF₂In addition, CF, CF₃, C₂In this specification, C, CF, CF₂Etc. CF₂Represented by radicals, CF₂CF radical₂The F radical is represented by F. For this reason, F and CF₂F and CF are changed under the condition that the ion generation amount is changed or the ion generation amount is constant, while the generation amount is constant.₂It was difficult to change the amount of incident light. For example, in the case of a parallel plate type etching apparatus, if the power of the high frequency bias for plasma generation is increased, the plasma density increases, so that the amount of ions generated increases, and at the same time, dissociation by plasma proceeds, so₂The amount of F generated with respect to will also change.
[0005]
Such a conventional etching apparatus has the following problems. When contact processing with a high aspect ratio is performed, under conditions where the resist selectivity is high, fluorine radicals F are reduced on the bottom surface of the contact hole, so that a polymer is formed by CF radicals and etching stops in the middle of the hole. On the other hand, under conditions where the etching does not stop, oxygen gas is added or fluorine is excessive, and the resist mask is etched by oxygen or fluorine, so that a sufficient selectivity with respect to the resist cannot be obtained. In the conventional technique, the gas dissociation in the plasma is fixed, and this problem cannot be dealt with.
[0006]
In addition, when a contact hole with a high aspect ratio is etched under a high gas pressure condition (4 Pa or higher), some ions are incident on the wafer from a tilting direction due to collision with gas molecules. Will be etched in the lateral direction, making vertical machining difficult. Collisions with gas molecules can be reduced by lowering the gas pressure, but with conventional devices, the plasma density and the electron temperature change when the gas pressure is lowered. A sufficient selection ratio could not be obtained, which was an obstacle to lowering the gas pressure.
[0007]
In the etching of the oxide film, with the miniaturization of the semiconductor device, the processing accuracy, the selectivity to the nitride film (to the nitride film selection ratio), the selectivity to the resist, etc., and the planarization of the semiconductor device and the wiring As the number of layers increases, it has become necessary to process contact holes with a high depth / hole diameter ratio (aspect ratio).
[0008]
The problem to be solved by the present invention is to control the generation amount of F and ions with respect to CF2 in plasma, and to process an oxide film that requires a high selection ratio for contact holes and silicon nitride films having a high aspect ratio. Is to realize.
[0009]
[Means for Solving the Problems]
By forming two or more plasma regions with different electron temperatures, CF in the plasma₂The production amount of F and ions with respect to can be controlled independently.
[0010]
In oxide film etching using fluorocarbon gas, CF₂The amount of F generated with respect to depends on the plasma temperature, and the amount of ions generated is determined in proportion to the power introduced into the plasma generation. C₄F₈In the case of C₄F₈CF has a threshold energy of about 6 eV, while CF₂Is about 12 eV. For this reason, when the electron temperature is low (1-4 eV), F is easily generated and F / CF₂The production ratio increases. When the electron temperature is 5-20 eV, CF₂Generation of F / CF₂The production ratio is smaller than in the case of low electron temperature. Therefore, using two types of electron temperatures, F and CF in the high electron temperature region.₂And F can be generated in a low temperature region. By varying the size of these two electron temperature regions, F / CF₂Control the ratio. The difference between these electron temperatures is 1 eV or more, preferably 5 eV or more.
[0011]
CF in plasma₂The reason why the amount of F and ions to be generated should be controlled independently is as follows. The introduced fluorocarbon gas is CF in the plasma.₂Dissociates into radicals, F radicals and ions and enters the wafer. The etching of the oxide film is CF₂Etching proceeds when ions are incident on the surface to which F and F are attached. In contrast, resist and silicon nitride films are etched mainly by F and ions, and CF₂Since a polymer is formed on the surface, it acts as an etching resistant film on a resist or silicon nitride film. For this reason, CF₂When etching is performed under a condition where the incident amount of ions and F is smaller than that of the above, a high selectivity can be obtained with respect to the resist and the silicon nitride film. However, if the ion incident amount is reduced, the etching rate of the oxide film is reduced, and if the F incident amount is reduced, the etching is stopped in a hole having a high aspect ratio. Thus, the etching process of the oxide film is generally CF.₂, F and ions, especially CF₂It depends on the incident amount of ions and the F incident amount with respect to the incident amount. Therefore, CF in plasma₂If the amount of F and ions produced can be controlled independently, the process conditions are expanded, and as a result, a finer and deeper oxide film can be processed.
[0012]
However, since F is generated in both electron temperature regions, F / CF under the condition that F is excessive as a whole.₂Will be controlled. In order to selectively exclude F, a gas containing hydrogen atoms (H₂, CH₂F₂, CH₄Etc.) can be removed by reacting F with H radicals. In addition, F can be consumed by reaction with the inner wall material. Specifically, a material that reacts with F, such as a Si plate or a SiC plate, is installed on the inner wall surface of the etching apparatus, and F is excluded by applying a high frequency bias to the plate in order to promote F consumption. In addition, CF₂F can be excluded by reacting F with the polymer formed by adhering to the wall. As the distance between the wafer and the inner wall portion is reduced, the area of the inner wall surface with respect to the volume of the plasma increases, so that the ratio of F generated by the plasma in the etching apparatus to the inner wall portion increases. That is, when the wafer and the inner wall are brought close to each other, F efficiently reacts with the polymer and is excluded. Specifically, it is possible to shorten the distance between the wafer and the wafer facing surface of the etching apparatus. By using these methods and plasma with two types of electron temperatures, F / CF₂The ratio can be controlled in a wide range.
[0013]
On the other hand, the amount of ions generated is determined by the electron density in the plasma, and the electron density is approximately proportional to the input high frequency power. F / CF₂Since the dissociation of is generated by gas collision with gas molecules, it depends on the power of the high frequency, but by changing the two electron temperature regions, the amount of ions generated is independent of F / CF.₂The generation ratio of can be controlled.
[0014]
As a specific method for generating two types of electron temperature regions, in the case of an etching apparatus using electron cyclotron resonance (ECR) as shown in FIG. 1, the electron temperature is high in the ECR region (high electron temperature region 103), In other portions, a low electron temperature region 102 is formed. The ECR region becomes narrower when the magnetic field gradient of the magnetic field applied from the outside is increased. Therefore, by controlling the magnetic field gradient in the ECR region, F / CF₂The production ratio can be varied. As shown in FIG. 2, under the condition where the magnetic field gradient is small, the high electron temperature region is widened.₂Since the generation ratio becomes smaller and the magnetic field gradient becomes larger, the high electron temperature region becomes narrower.₂The production ratio can be increased. In addition, the ECR region is generally inversely proportional to the high frequency to be introduced. For example, when the frequency is changed from 2.45 GHz to 450 MHz, the ECR region is expanded about five times. Therefore, by reducing the frequency of the high frequency to be introduced, the high electron temperature region is widened and F / CF₂The production ratio can be reduced.
[0015]
When the ECR region 101 is fixed, the size of the low electron temperature region 102 can be changed by changing the distance between the wafer 6 and the wafer facing surface 103. As shown in FIG. 2, when the distance between the wafer 6 and the wafer facing surface 103 is shortened, the low electron temperature region 102 becomes narrow.₂The production ratio can be reduced.
[0016]
As described above, in the case of the ECR etching apparatus, by controlling the magnetic field gradient, the frequency of the high frequency to be introduced, and the distance between the wafer and the wafer facing surface, the F / CF is independent of the amount of ions generated.₂The production ratio of can be controlled.
[0017]
Specifically, the present invention provides the following methods.
[0018]
The present invention provides a dry etching method for etching a film using plasma having a first electron temperature region and a second electron temperature region.
[0019]
The present invention further provides a dry etching method in which a difference between the first electron temperature and the second electron temperature is 1 eV or more.
[0020]
The present invention further provides a dry etching method in which a difference between the first electron temperature and the second electron temperature is 5 eV or more.
[0021]
The present invention further provides a dry etching method in which the first electron temperature is 2 eV or more and 4 eV or less, and the second electron temperature is 5 eV or more.
[0022]
The present invention further provides a dry etching method in which the film is a silicon oxide film, and the gas for generating the plasma is a fluorocarbon gas.
[0023]
The present invention further provides a dry etching method in which the pressure of the gas for generating the plasma is 4 Pa or less.
[0024]
The present invention introduces a gas containing a fluorocarbon gas into a processing chamber, converts the gas into plasma, and independently controls the amount of fluorine radicals, fluorocarbon radicals and ions generated in the plasma during etching, A dry etching method for dry etching an insulating film using the same is provided.
[0025]
The present invention further provides a dry etching method in which the amount of the fluorine radical and the fluorocarbon radical varies during the etching.
[0026]
According to the present invention, the plasma is formed by applying a magnetic field formed by a solenoid coil from the outside of the processing chamber to the processing chamber, and controlling the magnetic field gradient of the magnetic field by the solenoid coil, thereby generating F radicals. And a dry etching method that controls the production rate of fluorocarbon radicals.
[0027]
The present invention further provides a dry etching method for increasing the magnetic field gradient with the progress of etching of the insulating film.
[0028]
The present invention further provides a dry etching method in which the gas pressure in the processing chamber is 4 Pa or less.
[0029]
The present invention further provides a dry etching method in which the plasma is formed by applying a high frequency, and the frequency of the high frequency is 300 MHz to 900 MHz.
[0030]
The present invention further provides a dry etching method in which the plasma is formed by applying at least two types of high frequencies having different input powers.
[0031]
The present invention provides a processing chamber, a table for installing a substrate to be dry-etched provided in the processing chamber, means for introducing gas into the processing chamber, means for converting the gas into plasma, Provided is a dry etching apparatus for forming first and second electron temperature regions in plasma.
[0032]
The present invention further provides a dry etching apparatus in which the means for converting to plasma is means for applying a high frequency of 300 MHz to 900 MHz.
[0033]
The present invention further provides a dry etching apparatus in which four or more solenoid coils are installed around the processing chamber.
[0034]
The present invention further provides a dry etching apparatus in which the means for converting to plasma is a means for applying a high frequency to an antenna provided in a processing chamber, and the distance between the substrate and the antenna is 100 mm or less.
[0035]
DETAILED DESCRIPTION OF THE INVENTION
(Example 1)
A dry etching apparatus used in the present invention is shown in FIG. In this apparatus, an etching gas is introduced into the etching chamber 1, a high frequency between 900 MHz and 2.45 GHz is generated in the microwave generator 2, and this high frequency is transported to the etching chamber 1 through the waveguide 3. Gas plasma is generated. Four solenoid coils for generating a magnetic field are provided around the etching chamber so that the vertical magnetic field gradient in the ECR region can be controlled over a wide range with respect to the magnetic field strength in the ECR region. These solenoid coils 4 control the four coil currents so that a magnetic field between 0 and 875 Gauss is almost directly above the processing table, and the electron density is 10 using electron cyclotron resonance (ECR).¹¹Piece / cm³The above high density plasma is generated.
[0036]
The magnetic field gradient in the ECR region has a magnetic field gradient / magnetic field strength value of 0.1 cm.^-1To 0.01 cm^-1Control within the range. The etching processing chamber 1 has a processing table 5 on which an object to be processed 6 is placed and etched by gas plasma. The etching gas is introduced into the etching processing chamber 1 through the gas flow rate control device, and is exhausted out of the etching processing chamber 1 by the exhaust pump 7. The processing table 5 on which the object to be processed is provided is provided with a high frequency power source 12 and can apply a high frequency bias from 400 KHz to 13.56 MHz. The position of the processing table can be fixed within a range of 20 mm to 150 mm from the opposing surface (gas introduction port 11) of the processing table.
[0037]
An 8-inch silicon wafer is transferred to this apparatus as an object to be processed. An oxide film having a thickness of 2 mm is formed on the silicon wafer, and a resist mask to which a mask pattern is transferred is formed thereon. A 200 nm diameter hole is formed in the resist mask.
[0038]
Ar400 sccm, C₄F₈10 sccm, CH₂F₂Is introduced into the processing chamber through the 5 sccm gas inlet and the gas pressure is set to 2 Pa. A high frequency of 2.45 GHz and 1 kW is generated from a microwave generator, a bias of 800 KHz and 1000 W is applied to the processing table, and the oxide film is etched. The position of the processing table is set to 100 mm from the microwave introduction window, and the coil current is adjusted so that the magnetic field strength is 875 gauss at the position 6 cm directly above the wafer and the magnetic field gradient at that position is 50 gauss / cm. Under the conditions, the thickness of the ECR region is about 10 mm and the electron temperature is about 10 eV. The electron temperature outside the ECR region is about 3 eV. That is, a high electron region having a thickness of about 10 mm and a low electron region having a thickness of about 90 mm are formed. Part of F is CH₂F₂It is excluded by reacting with H produced from. For this reason, C₄F₈The amount of F produced from CF is CF₂F / CF that is incident on the wafer₂The ratio can be estimated to be about 0.6. The electron density is 3 × 10¹¹Piece / cm³The ion current density is 5 mA / cm²It will be about. Under this condition, the etching rate of the oxide film is about 700 nm / min and the selection ratio to the resist is 5. Although the machined shape is almost vertical, if the gas pressure is increased to 5 Pa under the same conditions, the cut is seen in the hole about 20 nm laterally due to ions incident obliquely. A nearly vertical machining shape is obtained at a gas pressure of 4 Pa or less.
[0039]
When the magnetic field gradient is 15 G / cm, the thickness of the ECR region increases to about 20 mm. As a result, the F / CF incident on the wafer₂The ratio is reduced to about 0.3. On the other hand, the plasma density hardly changes even when the magnetic field gradient is changed. In both cases, the ion current density is 5 mA / cm.²It will be about. For this reason, the etching rate of the oxide film is almost unchanged, and is about 700 nm / min in the plane portion. On the other hand, the resist selection ratio is improved to 30 because the F ratio is small.₂Therefore, the oxide film is etched to a depth of about 1 mm and stops.
[0040]
If the magnetic field gradient is changed from 15 Gauss / cm to 50 G / cm at a rate of 12 G / cm during etching, the etching rate is about 700 nm / min, and the etching is completed in about 3 minutes without stopping. To do. The selectivity with respect to the resist is about 20, and the resist selectivity is greatly improved as compared with etching with a magnetic field gradient of 50 G / cm.
[0041]
When the magnetic field gradient is controlled in this way, the F / CF is maintained while keeping the ion current constant.₂The ratio can be changed. By reducing the magnetic field gradient, the selectivity to the resist is increased. However, reducing the magnetic field gradient means that a uniform magnetic field is formed in the etching apparatus, and in order to achieve this with the same magnetic field strength, it is necessary to install many coils around the etching apparatus. There is. On the other hand, when the magnetic field strength is reduced, the magnetic field gradient is also reduced in proportion thereto, so that the magnetic field gradient can be easily reduced. Since the magnetic field strength that forms the ECR is determined by the frequency of the microwave, lowering the frequency of the microwave is advantageous to reduce the magnetic field strength and the magnetic field gradient.
[0042]
(Example 2)
Next, a case where the microwave frequency is set to 900 MHz using the same apparatus will be described. The coil current is adjusted so that the magnetic field strength is 320 gauss at a position 60 mm directly above the wafer and the magnetic field gradient at that position is 20 gauss / cm. Under these conditions, the thickness of the ECR region is about 20 mm, and the ECR region expands about twice as much as 2.45 GHz when the magnetic field gradient / magnetic field strength is substantially constant. Therefore, when the gas is introduced under the same conditions, the ion current density is 5 mA / cm.²The F / CF incident on the wafer is approximately the same as that of 2.45 GHz.₂The ratio can be estimated to be about 0.7. For this reason, the etching rate of the oxide film is about 700 nm / min and the selection ratio to the resist is 15.
[0043]
(Example 3)
Next, another embodiment using the apparatus of FIG. 5 will be described. In this apparatus, an etching gas is introduced into the etching process chamber 1, and a high frequency between 300 MHz and 900 MHz generated by the high frequency power source 503 is introduced from the antenna 502 into the etching process chamber 1 to generate gas plasma. Three solenoid coils 4 for generating a magnetic field are arranged around the etching process chamber for high-efficiency discharge, and the two coil currents are controlled so that the magnetic field between 0 and 320 gauss is almost directly above the processing table. The electron density is 10 using electron cyclotron resonance (ECR). ¹¹ Piece / cm³The above high density plasma is generated. The etching processing chamber 1 has a processing table 5 on which an object to be processed 6 is placed and etched by gas plasma. The etching gas is introduced into the etching processing chamber 1 through the gas flow rate control device, and is exhausted out of the etching processing chamber 1 by the exhaust pump 7. The processing table 5 on which the object to be processed is provided is provided with a high frequency power source 12 and can apply a high frequency bias from 400 KHz to 13.56 MHz. The position of the processing table can be fixed within a range of 20 mm to 150 mm from the microwave introduction window.
[0044]
An 8-inch silicon wafer is transferred to this apparatus as an object to be processed. A silicon nitride film having a thickness of 0.1 mm is formed on the silicon wafer, an oxide film having a thickness of 1.5 mm is formed thereon, and a resist mask having a mask pattern transferred thereon is formed thereon. A hole having a diameter of 150 nm is formed in the resist mask.
[0045]
Ar200sccm, C₄F₈10 sccm is introduced into the processing chamber through the gas inlet and the gas pressure is set to 1 Pa. Gas plasma is generated at a high frequency of 450 MHz and 1 kW, a bias of 800 KHz and 800 W is applied to the processing table, and the oxide film is etched. The position of the processing stage is set to 60 mm from the antenna 502, and the coil current is adjusted so that the magnetic field strength is 160 gauss at the position 40 mm directly above the wafer and the magnetic field gradient at that position is 4 gauss / cm. Under these conditions, the thickness of the ECR region is about 50 mm, and the electron temperature is about 8 eV. The electron temperature outside the ECR region is about 2 eV. C₄F₈F / CF due to dissociation of₂However, the amount of F incident on the wafer decreases due to the reaction between the polymer on the wafer facing surface and F. For this reason, the F / CF incident on the wafer₂The ratio is estimated to be about 0.5. Ion current density is 5 mA / cm²It will be about. Under these conditions, the etching rate of the oxide film is about 700 nm / min, the selection ratio to the resist is 20, and the selection ratio to the underlying nitride film is 30.
[0046]
Under these conditions, if etching is performed with an oxide film thickness of 3 mm and a contact hole diameter of 150 nm, the etching stops at a depth of about 2 mm. In the prior art, in such a case, it was necessary to add an oxygen gas to prevent etching from being stopped. In the case where oxygen gas is added, the resist selectivity is reduced to about 5 under the condition that etching does not stop. On the other hand, when the magnetic field gradient is increased from 4 gauss / cm to 10 gauss / cm and the generation amount of F is increased, the etching is stopped halfway in the etching with the oxide film thickness of 3 mm and the contact hole diameter of 150 nm. A substantially vertical machining shape can be obtained without any problems. At this time, the selection ratio with respect to the resist is reduced to about 10, but is increased as compared with oxygen addition.
[0047]
In this way, changing the magnetic field gradient even under the same gas conditions, F / CF₂By controlling the ratio, it becomes easy to cope with different etching conditions, and addition of oxygen gas or the like becomes unnecessary.
[0048]
Even if the frequency of the high-frequency power source for plasma formation is changed within the range of 300 MHz to 900 MHz, the same result as 450 MHz can be obtained by controlling the magnetic field gradient. When the frequency is lowered, the solenoid coil becomes smaller and the condition of the low magnetic field gradient is easily realized. Therefore, a frequency of 300 MHz to 600 MHz is particularly desirable. As for the gas pressure, when the gas pressure is increased to about 5 Pa, the oxide film is scraped in the lateral direction, and at a low gas pressure of 0.1 Pa or less, CF₂Therefore, it becomes difficult to obtain a sufficient etching rate while maintaining a high selection ratio. Therefore, the gas pressure is particularly preferably 0.1 Pa to 4 Pa.
[0049]
Under the same etching conditions that the frequency of the high frequency applied to the antenna is 450 MHz and the magnetic field gradient is 4 gauss / cm, the distance between the wafer and the antenna is changed from 60 mm to 100 mm, a 1.5 mm silicon oxide film, and a contact hole diameter of 150 nm. Process. By increasing the distance, the low electron temperature region increases and the influence of F consumption on the wafer facing surface decreases, so the relative incident amount of F increases. For this reason, the selection ratio with respect to a resist and a nitrided film becomes 10 and 12, respectively. When the distance between the wafer and the antenna was 100 mm or more, no change in the selectivity was observed. In this condition, CH₂F₂When gas is added at about 5 sccm, the resist selectivity is 20 and the nitride film selectivity is about 25.₂F₂Is highly deposited and adheres to the inner wall surface, so the frequency of cleaning increases and throughput decreases. That is, it is advantageous in terms of throughput to shorten the distance between the wafer and the antenna to 60 mm and improve the selection ratio. Conversely, if the distance between the wafer and the antenna is shortened to 40 mm, the incident amount of F decreases and the selectivity increases, but the etching stops at a depth of about 1.2 mm. Thus, by controlling the relative incident amount of F by controlling the distance between the wafer and the antenna and the magnetic field gradient, desired etching conditions can be achieved without adding a gas.
[0050]
Next, another embodiment using the apparatus of FIG. 6 will be described. In this apparatus, an etching gas is introduced into the etching chamber 1 to generate a high frequency of 10 to 100 MHz in the first high frequency power source 601 and the second high frequency power source 602, and this high frequency is etched from the ring antennas 603 and 604, respectively. Gas plasma is generated by introducing the gas into the processing chamber 1. The electron density of the plasma is 10¹¹Piece / cm³It becomes the above high-density plasma. The etching processing chamber 1 has a processing table 5 on which an object to be processed 6 is placed and etched by gas plasma. The etching gas is introduced into the etching processing chamber 1 through the gas flow rate control device, and is exhausted out of the etching processing chamber 1 by the exhaust pump 7. The processing table 5 on which the object to be processed is provided is provided with a high frequency power source 12 and can apply a high frequency bias from 400 KHz to 13.56 MHz.
[0051]
An 8-inch silicon wafer is transferred to this apparatus as an object to be processed. An oxide film having a thickness of 2 mm is formed on the silicon wafer, and a resist mask to which a mask pattern is transferred is formed thereon. A 200 nm diameter hole is formed in the resist mask.
[0052]
Ar400 sccm, C₄F₈Is introduced into the processing chamber through the gas inlet and the gas pressure is set to 3 Pa. A high frequency of 1500 W of 13.56 MHz is applied to the first ring antenna 603, a high frequency of 1000 W of 13.56 MHz is applied to the second ring antenna 604, gas plasma is generated, and a bias of 800 kHz and 1200 W is applied to the processing table. Is applied to etch the oxide film. Under this condition, the electron temperature near the height of the first ring antenna is about 10 eV, and 4 eV near the wafer. Although the etching rate of the oxide film is about 700 nm / min and the selectivity to the resist is about 25, the etching is stopped in the middle of the contact hole.
[0053]
When the high frequency power applied to the second ring antenna 604 is 500 W, the electron temperature near the wafer is reduced to about 2 eV. Since the plasma density is almost determined by the first ring antenna, the ion current density is not changed and the etching rate of the oxide film is 700 nm / min. However, the resist selectivity is reduced to about 10 by the decrease of the electron temperature. However, the etching does not stop under this condition.
[0054]
If the high frequency power applied to the second ring antenna 604 is changed from 1000 W to 500 W with the lapse of the etching time during etching, contact holes are formed without stopping the etching, and the average resist selectivity during etching is changed. Will be around 20.
[0055]
【The invention's effect】
According to the present invention, F / CF₂Therefore, the oxide film etching can be performed with a high selection ratio with respect to the resist and the nitride film without largely depending on the gas pressure and the gas flow rate. By using the present invention, it is possible to process a contact hole having a high aspect ratio and an oxide film at a high selectivity with respect to a resist and a silicon nitride film. Since the etching can be performed even under a low gas pressure condition of 1 Pa to 4 Pa, a vertical processing shape can be obtained with a contact hole having a high aspect ratio.
[Brief description of the drawings]
FIG. 1 is a conceptual diagram showing the formation of two types of electron temperature regions of the present invention.
FIG. 2 shows formation of two types of electron temperature regions and F / CF by controlling the magnetic field gradient of the present invention.₂It is a figure which shows the relationship of a production | generation ratio.
FIG. 3 shows formation of two types of electron temperature regions and F / CF by controlling the distance between the wafer and the wafer facing surface of the present invention₂It is a figure which shows the relationship of a production | generation ratio.
FIG. 4 is a cross-sectional view of a dry etching apparatus used in the present invention.
FIG. 5 is a cross-sectional view of another dry etching apparatus used in the present invention.
FIG. 6 is a cross-sectional view of another dry etching apparatus used in the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Etching processing chamber, 2 ... Microwave generator, 3 ... Waveguide, 4 ... Solenoid coil, 5 ... Processing stand, 6 ... Processing base, 7 ... Exhaust pump, 8 ... Exhaust valve, 9 ... Conductance valve, DESCRIPTION OF SYMBOLS 10 ... Gas flow controller, 11,501 ... Gas introduction port, 12 ... High frequency power supply for process tables, 13 ... Quartz chamber, 101 ... High electron temperature area, 102 ... Low electron temperature area, 103 ... Wafer facing surface, 201 ... Magnetic field gradient and F / CF₂Curve showing relationship of generation ratio, 301 ... high electron temperature region, 302 ... distance between wafer facing surface of etching apparatus and wafer, F / CF₂Curves showing the relationship of the generation ratio, 502 ... antenna, 503 ... high frequency power supply, 601 ... first high frequency power supply, 602 ... second high frequency power supply, 603 ... first ring antenna, 604 ... second ring antenna.

Claims (3)

In a dry etching method for etching a wafer in which a silicon oxide film is formed on a silicon nitride film by generating high-frequency and magnetic fields in an etching chamber and generating plasma.
The distance between the wafer facing surface and the wafer is set to 20 mm or more and 150 mm or less,
The pressure in the etching chamber is set to a low gas pressure in the range of 0.1 Pa to 4 Pa;
The high frequency is set to 300 MHz or more and 600 MHz or less,
Set the magnetic field gradient to a low gradient from 4 Gcm ⁻¹ to 50 Gcm ⁻¹ ;
Setting the value of the magnetic field gradient / magnetic field strength in the range of 0.1 cm ⁻¹ to 0.01 cm ⁻¹ ;
Introducing a gas containing a fluorocarbon gas into the processing chamber;
Forming a plasma of the gas introduced into the processing chamber using electron cyclotron resonance;
A first electron temperature region and a second electron temperature region are generated in a vertical direction between the opposite surface of the wafer and the wafer, and a magnetic field gradient of a magnetic field applied to the plasma is changed to change the first magnetic temperature region. Varying the size of the electron temperature region and the second electron temperature region, thereby independently controlling the amount of fluorine radicals, fluorocarbon radicals and ions generated in the plasma,
A method of manufacturing a semiconductor device, characterized in that dry etching of silicon oxide of the object to be processed is performed using the controlled plasma.   2. The method of manufacturing a semiconductor device according to claim 1, wherein the amount of the fluorine radical and the fluorocarbon radical changes during the etching.   The plasma is formed by applying a magnetic field formed by a solenoid coil from the outside of the processing chamber to the processing chamber, and generating a fluorine radical and a fluorocarbon radical by controlling a magnetic field gradient of the magnetic field by the solenoid coil. 2. The method of manufacturing a semiconductor device according to claim 1, wherein the ratio is controlled.

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