JP2019062045A - Planarization method for boron-based film and formation method for boron-based film - Google Patents

Abstract

To provide a technique capable of planarizing a boron-based film so as to be applicable for a semiconductor device.SOLUTION: A planarization method for a boron-based film for the planarization of a surface of a boron-based film that is formed on a substrate and mainly made of boron includes the steps of: performing, on a boron-based film, plasma treatment in which processing gas including CF-based gas containing C and F and oxygen-containing gas is used; and, after a step of performing the plasma treatment, ashing residual carbon-based by-products.SELECTED DRAWING: Figure 8

Description

  The present invention relates to a method of planarizing a boron-based film and a method of forming a boron-based film.

Recently, with the development of semiconductor manufacturing technology, miniaturization of semiconductor devices has been advanced, and devices of 14 nm or less, and further 10 nm or less have appeared. Further, in order to further integrate a semiconductor device, a technique for constructing a semiconductor element in three dimensions has been advanced. For this reason, the number of stacked thin films formed on a semiconductor wafer increases, and, for example, in a flash memory using a three-dimensional NAND, the thickness includes a silicon oxide (SiO ₂ ) film, a silicon nitride (SiN) film, etc. A process is required to finely process a thick laminated film of 1 μm or more by dry etching.

  Conventionally, an amorphous silicon film or an amorphous carbon film is used as a hard mask for micro processing, but the etching resistance is low. Therefore, when these films are used as a hard mask, it is necessary to increase the film thickness, and it is necessary to form a film as thick as 1 μm or more.

  Further, as a next-generation hard mask material, a metal material film such as tungsten having a higher etching resistance than an amorphous silicon film or an amorphous carbon film is being studied. However, a metal material film such as a tungsten film having a very high etching resistance is difficult to take measures against peeling after the dry etching process, metal contamination, and the like.

For this reason, a boron-based film has been studied as a new hard mask material having higher dry etching resistance than an amorphous silicon film or an amorphous carbon film and having a high selectivity to an SiO ₂ film or the like. Patent Document 1 describes that a boron-based film is formed by CVD as a hard mask.

Japanese Patent Application Publication No. 2013-533376

  By the way, as a hard mask material, it is known that a boron film of boron alone has excellent characteristics among boron-based films, but the boron film has large surface irregularities after film formation, for example, an average surface roughness The surface roughness represented by the roughness (Ra) or the root mean square roughness (RMS) may show a large value of 2 nm or more, which may be a factor limiting the application to a fine pattern of 14 nm or less. In addition, as to other boron-based films in which other elements such as nitrogen (N) and carbon (C) are added to boron, the surface irregularities also become a problem. Considering application to semiconductor devices, planarization technology for boron-based films with an RMS of 1 nm or less, and even 0.5 nm or less is required, but such boron-based film planarization technology is still established. Absent.

  Therefore, an object of the present invention is to provide a technique capable of planarizing a boron-based film so as to be applicable to a semiconductor device.

  In order to solve the above-mentioned problems, a first aspect of the present invention is a method of planarizing a boron-based film for planarizing the surface of a boron-based film mainly formed of boron formed on a substrate, which is a boron-based film And a step of performing plasma processing using a CF-based gas containing C and F, and a processing gas containing an oxygen-containing gas, to provide a method of planarizing a boron-based film.

After the step of performing the plasma treatment, the method may further include a step of ashing the remaining carbon by-product. The ashing process can be performed by plasma of O ₂ gas. The method may further include the step of wet cleaning the substrate on which the boron-based film is formed after the ashing step.

The CF-based gas may be only a gas containing C and F, only a gas containing C, F and H, or both of them. As the CF-based gas, at least one selected from the group consisting of C ₄ F ₆ , C ₄ F ₈ , and CH ₂ F ₂ can be used. An O ₂ gas can be used as the oxygen-containing gas in the plasma processing step.

  The step of performing the plasma processing can be performed by a parallel plate plasma processing apparatus. In the step of performing the plasma processing, a high frequency bias voltage may be applied to the substrate on which the boron-based film is formed.

  The boron-based film is preferably a boron film containing boron and unavoidable impurities. The boron-based film is preferably a film formed by plasma CVD, and more preferably a film formed by microwave plasma CVD.

  According to a second aspect of the present invention, there is provided a step of forming a boron-based film mainly composed of boron on a substrate, and a step of planarizing the surface of the boron-based film. In the step of planarizing, the boron-based film is subjected to plasma processing using a processing gas containing a CF-based gas containing C and F and an oxygen-containing gas. provide.

  In the step of forming the boron-based film, it is preferable to form a boron film containing boron and unavoidable impurities as the boron-based film. The step of forming the boron-based film is preferably performed by plasma CVD using a boron-containing gas, and more preferably performed by microwave plasma CVD.

  In the step of forming the boron-based film, a gas selected from the group consisting of diborane gas, boron trichloride gas, and alkyl borane gas can be used as the boron-containing gas.

  The step of forming the boron-based film and the planarization step are preferably performed in situ. Further, the step of forming the boron-based film and the step of planarizing may be performed in the same chamber.

  The step of forming the boron-based film and the planarization step may be repeated a predetermined number of times. In this case, it is preferable to set the film thickness of one time to such a thickness that a desired flatness can be obtained by the flattening process.

  According to the present invention, by combining the etching effect and the deposition effect of the CF-based gas, and the ion bombardment effect and the oxidation effect by the plasma of the oxygen-containing gas, the depressions on the surface of the boron film which are not desired to be etched Of the protrusions that are to be protected from etching by deposition of metals and carbon by-products are removed by plasma of oxygen-containing gas while etching is preferentially etched by ions of F and oxygen-containing gas decomposed from CF-based gas As a result, the flatness of the surface of the boron film becomes extremely high, making it applicable to semiconductor devices.

It is a SEM photograph of a boron film of as depo formed by microwave plasma CVD on a substrate. _{H 2} plasma treatment boron film of Figure 1, and NF ₃ is an SEM picture of the plasma treatment. It is a schematic diagram showing a state of boron film in the case of performing with H ₂ plasma treatment boron film. It is a schematic diagram showing a state of boron film in the case of performing NF ₃ plasma treatment boron film. (A) is an SEM photograph of the as depo boron film and the boron film after O ₂ annealing treatment and cleaning treatment, and (b) is after the as depo boron film and O ₂ annealing plasma treatment and cleaning treatment It is a SEM photograph of a boron film of It is a schematic diagram which shows the state of a boron film at the time of performing O ₂ annealing processing or O ₂ plasma processing to a boron film. It is a flowchart which shows the planarization method of the boron film concerning the 1st Embodiment of this invention. It is a schematic diagram for demonstrating the planarization model of the boron film in the planarization method of the boron film concerning the 1st Embodiment of this invention. FIG. 1 is a cross-sectional view showing an example of a processing apparatus for performing a boron film planarization method according to a first embodiment of the present invention. It is a SEM photograph of each step in Experimental example 1 of an experimental example of the first embodiment of the present invention. It is an AFM photograph of the boron film of as depo, and the boron film surface at the time of performing the planarization process of Experimental example 1-4. It is an AFM photograph of the boron film surface of the as depo boron, the example 5 of an experiment, the example 1 of an experiment, and the example 6 of an experiment in which O ₂ gas flow rate was changed at the time of planarization processing. It is a flowchart which shows the formation method of the boron film concerning the 2nd Embodiment of this invention. It is a SEM photograph and AFM photograph of the boron film of as depo when the film thickness of a boron film is 600 nm and 1800 nm. It is a SEM photograph and AFM photograph of a boron film after planarization processing when the film thickness of a boron film is 600 nm and 1800 nm. It is a flowchart which shows the other example of the formation method of the boron film concerning the 2nd Embodiment of this invention. It is a horizontal sectional view which shows an example of the processing system for performing the formation method of the boron film concerning a 2nd embodiment of the present invention. It is sectional drawing which shows the suitable example of the film-forming apparatus for forming a boron film into a film. It is a figure which shows an example of the processing apparatus which can perform film-forming and planarization process of a boron film | membrane in the same chamber.

  Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.

<Circumstances leading to the present invention>
First, the background of the present invention will be described.
Conventionally, planarization techniques have been proposed for various materials. For example, as planarization technology of polycrystalline silicon, one using plasma etching is known (for example, JP-A-9-232285, JP-A2007-266056). In addition, as a Ge film planarization technique, one using DHF cleaning after performing O ₂ annealing is known (IEEE ELECTRON DEVICE LETTERS, VOL. 36, NO. 4, APRIL 2015). This is a technology using oxygen diffusion.

Based on such a planarization technique, first, with respect to a boron film formed by microwave plasma CVD on a substrate, the influence on the planarization by H ₂ plasma processing and NF ₃ plasma processing was investigated. FIG. 1 is an SEM photograph of an initial (as depo) boron film (stage temperature: 250 ° C., pressure: 50 mTorr, microwave power: 4 kW, B ₂ H ₆ : 500 sccm, time: 5 min). As shown in FIG. 1, the film thickness of the boron film was 180 nm, and the surface roughness RMS was 2.3 nm. 2 (a) and 2 (b) respectively show the case where H ₂ plasma treatment (stage temperature: 250 ° C., pressure: 20 mTorr, H ₂ : 60 sccm, time: 90 sec) and NF ₃ plasma treatment (stage) temperature: 0.99 ° C., _pressure: 50mTorr, NF _{3: 300sccm,} time: 10 sec) is a SEM photograph when performing the. As shown in FIG. 2A, no change was observed on the surface of the boron film in H ₂ plasma treatment, and the surface roughness RMS remained at 2.3 nm. In addition, although ion sputtering by He plasma was also performed, it was the same in that case. On the other hand, as shown in FIG. 2 (b), in the NF ₃ plasma treatment, the boron film was etched to 120 nm, and the surface roughness RMS was rather 3.7 nm and the flatness of the surface was rather deteriorated.

In the case of the H ₂ plasma processing, as schematically shown in FIG. 3, the processing is with hydrogen ions, but even if hydrogen ions are simply supplied to the boron film, the surface does not change due to the hydrogen ions. The same applies to ion processing such as He ion.

On the other hand, in the case of NF ₃ plasma treatment, as shown in FIG. 4, NF ₃ dissociates into F or NF and reacts with boron (B) to etch the boron film and to make the surface rougher. Conceivable.

Next, with respect to a boron film (stage temperature: 300 ° C., pressure: 50 mTorr) formed on a substrate by microwave plasma CVD, the influence on the planarization by O ₂ annealing and O ₂ plasma processing was investigated. . FIG. 5 (a) shows the initial (as depo) boron film, the boron film after O ₂ annealing (oxygen atmosphere, 600 ° C., 30 min), and cleaning (pure water (DIW) + ultrasonic treatment: 30 min) FIG. 5 (b) is an initial (as depo) boron film, O ₂ annealing plasma treatment (O ₂ plasma 10 min), and cleaning treatment (pure water (DIW) + sonication: 30 min). It is a SEM photograph of boron film after. From these SEM photographs, it can be seen that the flatness of the surface is hardly changed by the O ₂ annealing treatment and the O ₂ plasma treatment.

This is because, as shown in FIG. 6, the surface of the boron film is oxidized and etched by O ₂ annealing and O ₂ plasma processing, but it is only oxidized as a whole, and the oxide film is removed by cleaning. However, it is considered that the flatness of the boron film surface hardly changes.

  From this, it was found that the boron film can not be sufficiently planarized by the planarization method as conventionally performed with a polycrystalline silicon film or a Ge film. This is considered to be due to the fact that the boron film is amorphous unlike the polycrystalline silicon film or the Ge film.

  Therefore, as a result of examining a method suitable for flattening of the boron film, it was conceived that a method capable of protecting the concave portion and etching only the convex portion on the surface of the boron film having the concavo-convex portion is effective.

Conventionally, in plasma etching, a CF-based gas is used, F decomposed from the CF-based gas contributes to the etching, and C decomposed from the CF-based gas is deposited on the sidewall as a carbon-based by-product (polymer) ) Is known to be a side wall protective layer, and such etching and deposition effects of CF-based gas, and ion bombardment and oxidation effects by plasma of oxygen-containing gas (eg, O ₂ gas) are used in combination. As a result, the depressions on the surface of the boron film which are not desired to be etched are protected from etching by the deposition of carbon-based by-products, and the projections to be etched are freed of carbon-based by-products by plasma of oxygen-containing gas. Etches preferentially by ions of F- and oxygen-containing gas decomposed from the system gas, resulting in It has been found that the semiconductor device has high flatness and is applicable to semiconductor devices.

First Embodiment
Next, a first embodiment will be described.
The present embodiment is a planarization method of planarizing a boron-based film formed by a predetermined method.

  The boron-based film to be planarized in this embodiment has a characteristic of high etching resistance, and is typically applied to a hard mask as an application utilizing such characteristics, for example, a semiconductor substrate It is formed on top of the film to be etched. The boron-based film contains 50 at. % Or more and may be a film mainly composed of boron having a% or more, or may be a boron film consisting of boron and unavoidable impurities, or other boron such as nitrogen (N), carbon (C), silicon (Si), etc. It may be a film to which an element is added. However, from the viewpoint of obtaining high etching resistance, a boron film containing no other additive element is preferable.

  The boron-based film may be any film formed by a general thin film formation technique used in the manufacture of semiconductor devices, and may be any of thermal CVD, plasma CVD, ALD and PVD, but in particular, boron having a good film quality. It is preferable that the film is formed by plasma CVD to obtain a base film. Among the plasma CVD, a film formed by microwave plasma CVD which is low in electron temperature and mainly composed of radicals and which can generate high density plasma with low damage is particularly preferable. In a boron-based film formed by CVD or ALD, about 5 to 15 at% of hydrogen (H) is mainly contained in the film as an impurity derived from a film forming material or the like.

  Even if the boron-based film is formed by any of the above film forming methods, the surface roughness is large as it is formed (as depo), the surface roughness RMS exceeds 1 nm, and the value exceeds 2 nm in plasma CVD. It becomes. In the recent etching processing technology, the final pattern dimension is miniaturized to about 10 nm by double patterning, and in consideration of application to a hard mask, the surface roughness RMS is required to be 1 nm or less, and further 0.5 nm or less.

  Therefore, it is necessary to planarize the surface of the boron-based film. FIG. 7 is a flowchart showing a method of planarizing a boron film according to the first embodiment. In the method of planarizing a boron film according to the present embodiment, the boron-based film is subjected to plasma processing using a processing gas containing a CF-based gas and an oxygen-containing gas (step 1), and then using an oxygen-containing gas And a step of performing ashing (step 2).

The CF-based gas used in Step 1 is a gas containing C and F, and is a gas represented by C _x F _y consisting of C and F such as C ₄ F ₆ and C ₄ F _8. Also, it may be a gas represented by C _x H _y F _z containing H in addition to C and F such as CH ₂ F ₂ . Further, as the CF-based gas, any one may be used alone, or two or more types may be mixed. In addition, as the oxygen-containing gas used in step 1, O ₂ , O ₃ , NO ₂ , H ₂ O or the like can be used. Among these, O ₂ is preferred. As the CF-based gas has a larger amount of F, the etching property is higher, and as the amount of C is larger, the deposition property is higher. It is preferable to make ratio F / C of F and C into the range of 1-4 (F: C = 1: 1-4: 1) in consideration of these. Further, the flow rate ratio CF / _{O 2} with an oxygen-containing gas such as CF-based gas and _{O 2 1~2 (CF: O 2} = 1: 1~2: 1) is preferably in the range of. _C x _H y _{F z} gas such as CH ₂ F ₂ also has the effect of suppressing the excess polymer depot separate H radicals.

  The plasma generation means is not particularly limited as long as the CF-based gas and the oxygen-containing gas can be effectively dissociated. In addition, it is preferable to apply a high frequency bias to a substrate to be processed on which a boron film is formed, for example, a semiconductor wafer to draw ions in plasma into the substrate to be processed. The frequency of the high frequency bias at this time is preferably in the range of 3 to 40 MHz, and the power is preferably in the range of 200 to 14,000 W. Moreover, the pressure is preferably in the range of 1.33 to 13.3 Pa (10 to 100 mTorr).

The ashing in step 2 is a step of removing C (polymer) remaining in the boron film after performing step 1. However, since planarization of the boron-based film is performed in step 1, step 2 may not be performed if it is not necessary to remove remaining C (polymer). The ashing at this time is performed in the same manner as ordinary ashing, and an excited oxygen-containing gas such as O ₂ plasma or O ₃ gas is used.

  Note that after ashing, wet cleaning with dilute hydrofluoric acid (DHF) or the like may be performed.

[Flating mechanism]
Next, the planarization mechanism of the boron film in the present embodiment will be described.
FIG. 8 is a schematic view for explaining a planarization model of a boron film in the present embodiment. Here, the case where a boron film is used as the boron-based film is shown. When a CF film such as C ₄ F ₈ , C ₄ F ₆ , or CH ₂ F ₂ or an oxygen-containing gas such as O ₂ gas is supplied to a boron film having a large surface roughness, the CF gas is activated by plasma. It is dissociated into species CF, CF ₂ and CF ₃ , and an oxygen-containing gas such as O ₂ gas is supplied to the boron film as oxygen-based ions (O ²⁺ etc.) (FIG. 8A).

C decomposed from CF, CF ₂ and CF ₃ is deposited (deposited) on the boron film as a carbon-based by-product, and F etches the boron film by chemical action to form BF ₃ . In addition, oxygen-based ions remove carbon-based by-products by the ion bombardment effect. At this time, the carbon-based by-product of C decomposed from the CF-based gas is likely to be deposited in the concave portion of the boron surface, and the portion where the carbon-based by-product is deposited has a large protective effect and boron by the chemical action of F. It is difficult for the film etching to proceed. On the other hand, carbon-based by-products are difficult to deposit in the convex portions of the boron surface, and the deposited carbon-based by-products are removed by the ion bombardment effect and oxidation effect of oxygen-based ions, and the chemical action of F Etching of boron proceeds. As described above, the surface of the boron film is not easily etched due to the protection by the carbon-based by-products in the concave portion which is not desired to be etched, and the convex portion to be removed by the etching is preferentially etched and the boron film surface is flattened. (FIG. 8 (b)). Then, carbon-based by-products remaining on the surface of the boron film are removed by ashing (FIG. 8C).

  By the planarization method of the present embodiment, the surface of a boron-based film having a film thickness of about 200 nm can be obtained with extremely high flatness such that the surface roughness RMS is 1 nm or less, and further 0.5 nm or less. It becomes applicable.

[An example of a processing apparatus for performing the flattening method of the first embodiment]
Next, an example of a processing apparatus for performing the planarization method of the present embodiment will be described.
FIG. 9 is a cross-sectional view showing an example of a processing apparatus for performing the planarization method of the present embodiment.

  The processing apparatus 100 is configured as a parallel plate type (capacitive coupling type) plasma etching apparatus in which a mounting table (stage) 20 and a gas shower head 30 are disposed opposite to each other in the chamber 10. The mounting table 20 functions as a lower electrode, and the gas shower head 30 functions as an upper electrode. The processing device 100 further includes a gas supply mechanism 40, a high frequency power supply device 50, and a control unit 60.

  The chamber 10 has a substantially cylindrical shape, and is made of, for example, aluminum whose surface is anodized, and is electrically grounded. An exhaust port 11 is formed on the bottom of the chamber 10, and an exhaust pipe 12 is connected to the exhaust port 11. The exhaust pipe 12 is connected to an exhaust device 13 including a vacuum pump, a pressure control valve, etc., and the inside of the chamber 10 is exhausted by the exhaust device 13 and the inside of the chamber 10 is controlled to a predetermined pressure (vacuum degree). Do. A wafer loading / unloading port 14 for loading / unloading a semiconductor wafer W (hereinafter, simply referred to as a wafer W), which is a substrate to be processed, on which a boron film is formed is provided on the side wall of the chamber 10. The valve G opens and closes. Then, with the gate valve G opened, loading and unloading of the wafer W to and from the chamber 10 are performed.

  The mounting table 20 is installed at the bottom of the chamber 10, and the wafer W is mounted thereon. The mounting table 20 is made of, for example, aluminum (Al), titanium (Ti), silicon carbide (SiC) or the like. An electrostatic chuck 22 for electrostatically attracting the wafer is provided on the upper surface of the mounting table 20. The electrostatic chuck 22 has a structure in which a chuck electrode 22a is sandwiched between insulators 22b. A direct current voltage source 23 is connected to the chuck electrode 22a, and a direct current voltage is applied from the direct current voltage source 23 to the chuck electrode 22a, whereby the wafer W is attracted to the electrostatic chuck 22 by electrostatic attraction force such as coulomb force. Ru.

  The mounting table 20 is supported by a support 24. A refrigerant channel 25 is formed in the inside of the support 24. A refrigerant supply pipe 25 a and a refrigerant discharge pipe 25 b are connected to the refrigerant flow path 25, and these are connected to the chiller unit 26. Then, the refrigerant (for example, cooling water, brine, etc.) output from the chiller unit 26 circulates through the refrigerant supply pipe 25a, the refrigerant flow path 25, and the refrigerant discharge pipe 25b, whereby the mounting table 20 and the electrostatic chuck 22 are It is cooled.

  The electrostatic chuck 22 is connected to a heat transfer gas supply line 27 for supplying a heat transfer gas such as helium gas (He) or argon gas (Ar) to the back surface of the wafer W thereon, thereby supplying the heat transfer gas. The heat transfer gas is supplied to the line 27 from the heat transfer gas supply source 28. The heat of the refrigerant is transferred to the wafer W by the heat transfer gas, and the temperature of the wafer W is controlled to a predetermined temperature.

  A wafer elevating pin (not shown) is provided on the mounting table 20 so as to be able to protrude from or retract from the surface of the electrostatic chuck so that the wafer W can be delivered with the wafer elevating pin protruding. It has become.

  The gas shower head 30 has a disk shape, and is fitted into an annular lid 15 provided at the top of the chamber 10 via a shield ring 35 made of an insulator, and constitutes a ceiling portion of the chamber 10. The gas shower head 30 may be electrically grounded as illustrated, or a variable DC power supply may be connected to apply a predetermined direct current (DC) voltage.

  The gas shower head 30 has a main body 31, and a gas inlet 33 for introducing a gas is formed at the upper center of the main body 1. Inside the main body 31, there are provided a first gas diffusion chamber 31a at the center and an annular second gas diffusion chamber 31b at the edge. The gas introduction port 33 is connected to the first gas diffusion space 31a, and the gas introduction path 34 branched from the gas introduction port 33 is connected to the second gas diffusion space 31b. A plurality of gas discharge holes 32 are formed at the bottom of the main body 31 so as to face the inside of the chamber 10 from the first gas diffusion space 31 a and the second gas diffusion space 31 b. A gas supply pipe 41 of a gas supply mechanism 40 to be described later is connected to the gas inlet 33, and the gas from the gas supply mechanism 40 is transmitted from the gas inlet 33 to the first gas diffusion chamber 31a and the second gas diffusion chamber. The gas is introduced into the chamber 31 b and discharged from the gas discharge holes 32 toward the mounting table 20 in the chamber 10.

  The gas supply mechanism 40 supplies the gas from the CF-based gas supply source 42, the oxygen-containing gas supply source 43, the pipes 44 and 45 extending from these gas supply sources, and the pipes 44 and 45 to the shower head 30. And a piping 41. The pipe 44 is provided with a flow rate controller 46 such as a mass flow controller and an on-off valve 47, and the pipe 45 is provided with a flow rate controller 48 and an on-off valve 49. In addition, 1 type or multiple types of CF type gas are used, and CF type gas supply source and piping are provided only the number of the kind of the gas.

  The high-frequency power supply device 50 supplies high-frequency power of two-frequency superposition to the mounting table 20, and a first high-frequency power supply 52 for supplying a first high-frequency power of a first frequency for plasma generation; And a second high frequency power supply 54 for supplying a second high frequency power of a second frequency lower than the first frequency. The first high frequency power supply 52 is electrically connected to the mounting table 20 via the first matching unit 53. The second high frequency power supply 54 is electrically connected to the mounting table 20 via the second matching unit 55. The first high frequency power supply 32 applies, for example, a first high frequency power of 40 MHz to the mounting table 20. The second high frequency power supply 34 applies, for example, a second high frequency power of 3 MHz to the mounting table 20. The first high frequency power may be applied to the gas shower head 30.

  The first matching unit 53 matches the load impedance to the internal (or output) impedance of the first high frequency power supply 52, and when the plasma is generated in the chamber 10, the output impedance and the load impedance of the first high frequency power supply 52 Acts to match up apparently. The second matching unit 55 matches the load impedance to the internal (or output) impedance of the second high frequency power supply 54, and when the plasma is generated in the chamber 10, the internal impedance and load of the second high frequency power supply 54 It functions to match the impedance apparently.

  The high frequency power from the first high frequency power supply 52 may be applied, for example, in the form of pulse power modulation. The period of the pulse is preferably about 5 to 40 kHz.

  The control unit 60 controls each component of the processing apparatus 100, for example, valves, a flow rate controller, a first high frequency power supply 52, a second high frequency power supply 54, an exhaust device 13, supply of heat transfer gas, supply of refrigerant, and the like. . The control unit 60 includes a main control unit having a CPU, an input device, an output device, a display device, and a storage device. In the storage device, a program for controlling processing to be executed by the processing apparatus 100, that is, a storage medium storing a processing recipe is set, and the main control unit executes a predetermined processing recipe stored in the storage medium. It calls up and controls the processing apparatus 100 to perform predetermined processing based on the processing recipe.

  In the processing apparatus 100 configured as described above, first, the gate valve G is opened, the wafer W is carried into the chamber 10, and the wafer W is placed on the mounting table 20 and the gate valve G is closed. Then, the inside of the chamber 10 is exhausted by the exhaust device 13, and the pressure adjustment valve regulates the pressure in the chamber 10 to a predetermined degree of vacuum, and the direct current voltage is applied to the chuck electrode 22 a from the direct current voltage source 23. W is attracted to the electrostatic chuck 22 and held.

Next, the first high-frequency power supply 52 is supplied with the oxygen-containing gas such as a CF-based gas such as C ₄ F ₈ , C ₄ F ₆ , or CH ₂ F ₂ and an O ₂ gas as processing gases. The first high frequency power for plasma generation is supplied to the mounting table 20 to generate plasma, and the second high frequency power for bias voltage application is supplied from the second high frequency power supply 54 to the mounting table 20 to ion the wafer W. And perform plasma processing for planarization of the boron-based film of the mechanism described above. At this time, the total flow rate of the CF-based gas is preferably 10 to 100 sccm, the flow rate of the oxygen-containing gas such as O ₂ gas is preferably 1 to 100 sccm, and the pressure is preferably 1.33 to 13.3 Pa (10 to 100 mTorr).

Thereafter, plasma is generated while supplying an O ₂ gas or the like into the chamber 10, and C (polymer) remaining in the boron-based film is removed by ashing.

  After the planarization process of the boron-based film as described above, the wafer W is discharged, and the gate valve G is opened to carry the wafer W out of the chamber 10 through the loading / unloading port 14.

[Example of experiment]
Next, an experimental example of the first embodiment will be described.
Here, on the substrate, plasma CVD using a microwave plasma apparatus under the conditions of stage temperature: 250 ° C., pressure: 50 mTorr, microwave power: 4.2 kW, B ₂ H ₆ flow rate: 500 sccm, time: 5 min. Then, the boron film formed to a thickness of about 150 nm was subjected to planarization processing including the plasma processing step of step 1 and the ashing step of step 2 using the processing apparatus of FIG. In the plasma processing step of step 1, an O ₂ gas was used as the oxygen-containing gas, and the gas flow rate including the gas species of the CF-based gas and the O ₂ gas was changed as in Experimental Examples 1 to 4 below.

(A) Experimental example 1
・ CF based gas C ₄ F ₆ : 43 sccm
C ₄ F ₈ : 35 sccm
CH ₂ F ₂ : 58 sccm
-O ₂ gas: 95 sccm
(B) Experimental example 2
・ CF based gas C ₄ F ₆ : 43 sccm
-O ₂ gas: 43 sccm
(C) Experimental example 3
・ CF based gas C ₄ F ₈ : 35 sccm
-O ₂ gas: 17 sccm
(D) Experimental example 4
・ CF based gas CH ₂ F ₂ : 58 sccm
-O ₂ gas: 58 sccm

All other conditions of step 1 were the following common conditions.
・ Pressure: 20mTorr (2.7Pa)
・ High frequency power 1st high frequency power supply (40 MHz): 700 W
Second high frequency power supply (3 MHz): 7800 W
・ Plasma pulse: Yes (frequency 10kHz)
Stage temperature: 60 ° C

The conditions for the ashing process in step 2 were as follows.
・ Pressure: 100 mTorr (13.3 Pa)
・ High frequency power 1st high frequency power supply (40 MHz): 600 W
Second high frequency power supply (3 MHz): 50 W
-O ₂ gas flow rate: 600 sccm
・ Time: 60 seconds

  The flatness of the boron film after these treatments was confirmed. In Experimental Example 1, after the ashing step, the flatness after the wet cleaning treatment of dilute hydrofluoric acid (100: 1 DFH): 1 min and pure water (DIW): 5 min was also confirmed.

  FIG. 10 is a SEM photograph of each step in Experimental Example 1. As shown in FIG. 10, while the surface roughness RMS of the initial (as depo) boron film was 2.4 nm, the plasma processing step of Experimental Example 1 has progressed in planarization, and after passing through the ashing step, in fact The surface roughness was measured, and an extremely high flatness of 0.3 nm in RMS was obtained. Further, by performing a wet cleaning treatment thereafter, the RMS was 0.2 nm, and the flatness was further improved.

FIG. 11 is an AFM photograph of the boron film of initial (as depo) and the surface of the boron film when the planarization process of Experimental Examples 1 to 4 is performed. As shown in FIG. 11, in all of Experimental Examples 1 to 4, RMS was 1 nm or less, and good flatness was obtained. Among these, while Experimental Example 4 using only CH ₂ F ₂ containing H as a CF-based gas has an RMS of 0.7 nm, either or both of C ₄ F ₆ and C ₄ H ₈ are used. In Experimental Examples 1 to 3 used, the RMS was 0.3 nm.

Next, the influence of O ₂ gas in the plasma processing of step 1 was confirmed.
Here, only the flow rate of O ₂ gas in the plasma processing in experimental example 1 is changed to 75 sccm and 115 sccm with respect to the boron film formed under the same conditions as above as Experimental Example 5 and Experimental Example 6, and other conditions The plasma treatment and the ashing treatment were performed under the same conditions as in Experimental Example 1 to evaluate the flatness of the boron film.

The results are shown in FIG. Figure 12 is a boron film initials (as depo), _{O 2} experimental examples the gas flow rate was 75 sccm 5, _{O 2} Experimental Example 1 the gas flow rate was 95 sccm, _{O 2} gas flow rate of Example 6 was 115sccm It is an AFM photograph of the boron film surface at the time of performing a planarization process. As shown in FIG. 13, while the surface roughness RMS of the initial (as depo) boron film is 2.4 nm, in the experimental example 5 in which the flow rate of O ₂ gas is 75 sccm, RMS = 1.0 nm, O ₂ In Experimental Example 1 in which the gas flow rate is 95 sccm, RMS = 0.3 nm, and in Experimental Example 6 in which the O ₂ gas flow rate is 115 sccm, RMS is 0.2 nm, and the O ₂ gas flow rate in the plasma processing in Step 1 contributes to flatness. You can see that That is, it is considered that the flatness of the surface of the boron film is improved by optimizing the flow ratio of the CF gas and the O ₂ gas and appropriately removing the carbon by-product by the O ₂ plasma.

Second Embodiment
Next, a second embodiment will be described.
FIG. 13 is a flowchart showing a method of forming a boron-based film according to the second embodiment. In the method of forming a boron-based film according to the present embodiment, a step of forming a boron-based film on a substrate (step 11), and a step of planarizing the surface of the formed boron-based film (step 12) Have.

  The film formation of the boron-based film in step 11 can be performed by a general thin film formation technique used for manufacturing a semiconductor device, and any of thermal CVD, plasma CVD, ALD and PVD may be used, but in particular, the film quality is good. It is preferable to use plasma CVD which can provide a boron-based film. Among plasma CVD, microwave plasma CVD which is low in electron temperature and mainly composed of radicals, and which can generate high-density plasma with low damage is particularly preferable. The boron-based film contains 50 at. % Or more and may be a film mainly composed of boron having a% or more, or may be a boron film consisting of boron and unavoidable impurities, or other boron such as nitrogen (N), carbon (C), silicon (Si), etc. It may be a film to which an element is added. From the viewpoint of obtaining high etching resistance, a boron film containing no other additive element is preferable. In the case of forming a boron-based film by CVD or ALD, hydrogen (H) is mainly contained in the film as an impurity derived from a film forming raw material or the like at about 5 to 15 at%.

  The planarization process of step 12 is performed in the same manner as the planarization method of the first embodiment. That is, as in step 1 of the first embodiment, the boron-based film formed in step 11 is subjected to plasma processing using a processing gas containing a CF-based gas and an oxygen-containing gas, and then in the same manner as step 2. Do ashing on Also, as in the first embodiment, after ashing, wet cleaning with dilute hydrofluoric acid (DHF) or the like may be performed.

  According to the present embodiment, it is possible to form a boron-based film having extremely high flatness, i.e., a surface roughness RMS of 1 nm or less, and further 0.5 nm or less, at a film thickness of up to about 200 nm.

By the way, when the boron-based film to be formed is thick, the growth of nuclei proceeds, the surface waviness and the like become large, and the surface roughness tends to become large. For example, as shown in the above-mentioned experimental example 1, a boron film formed by plasma CVD (stage temperature: 250 ° C., pressure: 50 mTorr, microwave power: 4.2 kW, B ₂ H ₆ : 500 sccm, time: 5 min) When the film thickness is 150 nm, the surface roughness RMS is 2.4 nm in as depo, but when the film formation time is increased and the film thickness is increased to 600 nm and 1800 nm, respectively, as shown in FIGS. As shown in the SEM photograph and the AFM photograph of A), the surface roughness at as depo is generally rough, and when the film thickness is 600 nm, RMS = 3.9 nm and when the film thickness is 1800 nm, RMS = 6.7 nm. .

  Therefore, when the film thickness is 150 nm, an extremely high flatness of RMS = 0.3 nm is obtained after the planarization process, but with the film thickness of 600 nm and 1800 nm, the surface after the planarization process is as shown in FIG. As shown in the SEM photograph and AFM photograph of (b), although microscopically very flat, large irregularities in the as depo state remain, and when the film thickness is 600 nm, the RMS = 0.9 nm, the film thickness When the film thickness is 1800 nm, RMS = 3.1 nm and the film thickness become rough as compared with 0.3 nm in the case of 150 nm.

  Therefore, the formation of the boron-based film and the planarization process are repeated a predetermined number of times. Preferably, as shown in FIG. 16, a step (step 21) of depositing a boron-based film on the substrate to a film thickness that can obtain a desired flatness by a planarization process; The step of planarizing the surface of the substrate (step 22) is repeated a predetermined number of times. Thus, a boron-based film having a large film thickness and high surface flatness can be formed.

  At this time, in order to form a film with good continuity, wet processing or plasma processing for the purpose of removing the C that could not be removed by ashing processing or the oxide layer formed in step 22 etc. You may go.

[An example of a processing system for performing the method of forming a boron-based film of the second embodiment]
Next, an example of a processing system for performing the method of forming a boron-based film of the present embodiment will be described.
FIG. 17 is a horizontal sectional view showing an example of a processing system for performing the method of forming a boron-based film according to the present embodiment.

  As shown in FIG. 17, the processing system 300 has two processing apparatuses 100 for planarization processing and two film forming apparatuses 200 for forming a boron-based film. The processing device 100 has the same configuration as the processing device 100 of the first embodiment. These are connected to the four walls of the vacuum transfer chamber 301 having a heptagonal shape in plan view via gate valves G, respectively. The inside of the vacuum transfer chamber 301 is evacuated by a vacuum pump and held at a predetermined degree of vacuum. That is, the processing system 300 is a multi-chamber type vacuum processing system, and can continuously perform the film forming process of step 11 and the planarization process of step 12 described above without breaking the vacuum.

  The film forming apparatus 200 may be any apparatus that can perform a thin film forming method that is usually used, and as described above, may be any apparatus that performs thermal CVD, plasma CVD, ALD, or PVD. A plasma CVD apparatus capable of obtaining a good boron-based film is preferable, and a microwave plasma CVD apparatus as described later is preferable among them.

  Further, three load lock chambers 302 are connected to the other three walls of the vacuum transfer chamber 301 via a gate valve G1. An air transfer chamber 303 is provided on the opposite side of the vacuum transfer chamber 301 across the load lock chamber 302. The three load lock chambers 302 are connected to the atmosphere transfer chamber 303 via the gate valve G2. The load lock chamber 302 performs pressure control between atmospheric pressure and vacuum when transferring the silicon wafer W between the atmosphere transfer chamber 303 and the vacuum transfer chamber 301.

  On the wall opposite to the load lock chamber 302 mounting wall of the atmosphere transfer chamber 303, there are provided three carrier mounting ports 305 for mounting a carrier (FOUP or the like) C for storing the wafer W therein. Further, an alignment chamber 304 for aligning the silicon wafer W is provided on the side wall of the atmosphere transfer chamber 303. In the atmosphere transfer chamber 303, a downflow of clean air is formed.

  In the vacuum transfer chamber 301, a transfer mechanism 306 is provided. The transport mechanism 306 transports the silicon wafer W to the oxide film removal apparatus 100, the metal film deposition apparatus 200, and the load lock chamber 302. The transport mechanism 306 has two transport arms 307 a and 307 b which can move independently.

  In the atmosphere transfer chamber 303, a transfer mechanism 308 is provided. The transport mechanism 308 transports the silicon wafer W to the carrier C, the load lock chamber 302, and the alignment chamber 304.

  The processing system 300 has an overall control unit 310. The general control unit 310 sends control commands to the control units provided in the processing apparatus 100 and the film forming apparatus 200, and also the exhaust mechanism of the vacuum transfer chamber 301, the gas supply mechanism and transfer mechanism 306, and the exhaust of the load lock chamber 302. A mechanism, a gas supply mechanism, a transport mechanism 308 of the atmosphere transport chamber 303, a drive system of the gate valves G, G1, G2, and the like are controlled.

  In the processing system 300 configured as described above, first, the wafer W, which is a substrate to be processed, is taken out of the carrier C connected to the atmosphere transfer chamber 303 by the transfer mechanism 308 and any of the wafers W is transferred via the alignment chamber 304. After carrying in the load lock chamber 302 and evacuating the load lock chamber 302, the wafer W is taken out of the load lock chamber 302 by either of the transfer arms 307a and 307b of the transfer mechanism 306, and any film forming apparatus 200 To carry out film formation processing of a boron-based film.

  After completion of the film forming process, the wafer W contained therein is unloaded by one of the transfer arms 307a and 307b of the transfer mechanism 306, transferred into the processing apparatus 100, and the boron-based film is planarized.

  The film forming process by the film forming apparatus 200 and the planarization process by the processing apparatus 100 may be repeated on the wafer W as necessary.

  The processed wafer W is transferred into one of the load lock chambers 302 by one of the transfer arms 307 a and 307 b of the transfer mechanism 306, the load lock chamber 302 is returned to the atmosphere, and the load lock is performed by the transfer mechanism 308. The wafer W in the chamber 302 is returned to the carrier C. The above process is performed on all the wafers W in the carrier C.

  According to this processing system 300, film formation and planarization processing of a boron film can be performed in situ.

[Deposition apparatus]
Next, an example of a film forming apparatus 200 for forming a boron-based film will be described.
FIG. 18 is a cross-sectional view showing an example of the film forming apparatus 200. As shown in FIG. The film forming apparatus 200 is configured as a microwave plasma CVD apparatus for forming a boron film as a boron-based film.

  The film forming apparatus 200 has a substantially cylindrical chamber 101 which is airtight and grounded. The processing container 101 is made of, for example, a metal material such as aluminum and its alloy. At the top of the chamber 101, a microwave plasma source 120 is provided. The microwave plasma source 120 is configured, for example, as an RLSA (registered trademark) microwave plasma source.

  A circular opening 110 is formed substantially at the center of the bottom wall of the chamber 101, and the bottom wall is provided with an exhaust chamber 111 which communicates with the opening 110 and protrudes downward.

  In the chamber 101, a disk-shaped mounting table 102 made of ceramics such as AlN for supporting the wafer W horizontally is provided. The mounting table 102 is supported by a support member 103 made of ceramic such as cylindrical AlN which extends upward from the center of the bottom of the exhaust chamber 111. In addition, a heater 105 of a resistance heating type is embedded in the mounting table 102. The heater 105 is supplied with power from a heater power supply (not shown) to heat the mounting table 102, and the wafer W is heated to a predetermined temperature. It is heated. Further, an electrode 107 is embedded in the mounting table 102, and a high frequency power source 109 for applying a bias voltage is connected to the electrode 107 via a matching unit 108.

  A wafer support pin (not shown) for supporting and elevating the wafer W is provided on the mounting table 102 so as to be able to protrude and retract with respect to the surface of the susceptor 2.

  An exhaust pipe 123 is connected to a side surface of the exhaust chamber 111, and an exhaust mechanism 124 including a vacuum pump, an automatic pressure control valve, and the like is connected to the exhaust pipe 123. By operating the vacuum pump of the exhaust mechanism 124, the gas in the chamber 1 is uniformly discharged into the space 111a of the exhaust chamber 111, exhausted through the exhaust pipe 123, and the inside of the chamber 101 is specified by the automatic pressure control valve. The degree of vacuum is controllable.

  A loading / unloading port 125 for loading / unloading the wafer W between the vacuum transfer chamber 301 adjacent to the film forming apparatus 200 is provided on the side wall of the chamber 101, and the loading / unloading port 125 is opened and closed by the gate valve G. Be done.

  An upper portion of the chamber 101 is an opening, and a peripheral portion of the opening is a ring-shaped support portion 127. The microwave plasma source 120 is supported by the support portion 127.

The microwave plasma source 120 includes a disk-shaped microwave transmitting plate 128 made of a dielectric such as quartz or ceramic such as Al ₂ O ₃ , a planar slot antenna 131 having a plurality of slots, and a wave retarding member 133. A coaxial waveguide 137, a mode converter 138, a waveguide 139, and a microwave generator 140 are included.

  The microwave transmission plate 128 is airtightly provided on the support member 127 via the seal member 129. Therefore, the chamber 101 is kept airtight.

  The planar atron antenna 131 has a disk shape corresponding to the microwave transmission plate 128 and is provided so as to be in close contact with the microwave transmission plate 128. The planar slot antenna 131 is locked to the upper end of the side wall of the chamber 101. The planar antenna 31 is formed of a disc made of a conductive material.

  The planar antenna 131 is made of, for example, a copper plate or an aluminum plate whose surface is plated with silver or gold, and has a configuration in which a plurality of slots 132 for radiating microwaves penetrate in a predetermined pattern. The pattern of the slots 132 is appropriately set so that the microwaves are radiated uniformly. For example, as an example of the pattern, it can be mentioned that a plurality of pairs of slots 132 are concentrically arranged with the two slots 132 arranged in a T-shape as a pair. The length and arrangement interval of the slots 132 are determined according to the effective wavelength (λg) of the microwaves, and for example, the slots 132 are arranged such that their interval is λg / 4, λg / 2 or λg. The slot 132 may have another shape such as a circular shape or an arc shape. Further, the arrangement form of the slots 132 is not particularly limited, and in addition to the concentric form, the form may be, for example, a spiral form or a radial form.

The wave retarding material 133 is provided in close contact with the upper surface of the planar antenna 131. The wave retarding material 133 is made of a dielectric having a dielectric constant larger than that of vacuum, for example, a resin such as quartz, ceramics (Al ₂ O ₃ ), polytetrafluoroethylene, or polyimide. The wave retarding member 133 has a function of shortening the wavelength of the microwave than in vacuum to make the planar antenna 131 smaller.

  The thicknesses of the microwave transmission plate 128 and the retardation member 133 are adjusted such that the retardation plate 133, the planar slot antenna 131, the microwave transmission plate 128, and the equivalent circuit formed of plasma satisfy the resonance condition. By adjusting the thickness of the wave retarding material 133, the phase of the microwave can be adjusted, and by adjusting the thickness so that the junction of the planar antenna 131 becomes a "flapping" of the standing wave, The reflection of the microwaves is minimized and the radiant energy of the microwaves is maximized. In addition, by making the retardation plate 133 and the microwave transmission plate 128 of the same material, interface reflection of microwaves can be prevented.

  The planar antenna 131 and the microwave transmitting plate 128 and the wave retarding member 133 and the planar antenna 131 may be spaced apart from each other.

  A cooling jacket 134 made of a metal material such as aluminum, stainless steel, copper or the like is provided on the upper surface of the chamber 101 so as to cover the planar antenna 131 and the wave retarding material 133. A cooling water flow path 134 a is formed in the cooling jacket 134, and cooling water flows through the cooling water flow path 134 a to cool the wave retarding member 133, the planar antenna 131, and the microwave transmission plate 128.

  The coaxial waveguide 137 is inserted from above the centrally formed opening of the upper wall of the cooling jacket 134. The coaxial waveguide 137 is formed by concentrically arranging a hollow rod-shaped inner conductor 137a and a cylindrical outer conductor 137b. The lower end of the inner conductor 137 a is connected to the planar slot antenna 131. The coaxial waveguide 137 extends upward. The mode converter 138 is connected to the upper end of the coaxial waveguide 137. Connected to the mode converter 138 is one end of a horizontally extending rectangular waveguide 139. The microwave generator 140 is connected to the other end of the waveguide 139. A matching circuit 141 is interposed in the waveguide 139.

  The microwave generator 140 generates microwaves having a frequency of 2.45 GHz, for example, and the generated microwaves propagate in the waveguide 139 in the TE mode, and the vibration mode of the microwave is changed from the TE mode in the mode converter 138 The light is converted to the TEM mode and propagates toward the wave retarding member 133 via the coaxial waveguide 137. Then, the microwave radially spreads radially outward in the inside of the retardation member 133, is radiated from the slot 132 of the planar slot antenna 131, passes through the microwave transmission plate 128, and transmits the microwave in the chamber 101. An electric field is generated in the region directly below the plate 128 to generate microwave plasma. In a part of the lower surface of the microwave transmitting field 128, an annular recess 128a is formed on a taper to facilitate generation of a standing wave by the introduced microwave, and microwave plasma It can be generated efficiently.

  In addition to 2.45 GHz, various frequencies such as 8.35 GHz, 1.98 GHz, 860 MHz, 915 MHz, and the like can be used as the microwave frequency.

The film forming apparatus 200 has a gas supply unit 106 for supplying a processing gas containing a boron-containing gas. Examples of the boron-containing gas include diborane (B ₂ H ₆ ) gas, boron trichloride (BCl ₃ ) gas, alkyl borane gas, decaborane gas and the like. As the alkyl borane gas, trimethyl borane (B (CH ₃ ) ₃ ) gas, triethyl borane (B (C ₂ H ₅ ) ₃ ) gas, B (R 1) (R 2) (R 3), B (R 1) (R 2) _{) H, B (R1) H} 2 (R1, R2, R3 may be given gas and the like represented by an alkyl group). Among these, B ₂ H ₆ gas can be suitably used.

Further, the processing gas contains an inert gas for plasma excitation or hydrogen (H ₂ ) gas, and as the inert gas, a rare gas such as He gas or Ar gas is used. Although N ₂ gas can be used, it is preferable to use He gas or Ar gas from the viewpoint of suppressing the formation of boron nitride. In the following, the case of using a reaction gas containing B ₂ H ₆ gas as a boron-containing gas and He gas as an inert gas for plasma excitation will be described as an example.

The gas supply unit 106 includes a first gas supply unit 161 that discharges gas toward the center of the wafer W, and a second gas supply unit 162 that discharges gas from the outside of the wafer W. The first gas supply unit 161 includes a mode converter 138 and a gas flow path 163 formed inside the inner conductor 37 a of the coaxial waveguide 37, and the gas supply port 164 at the tip of the gas flow path 163 is For example, the central portion of the microwave transmission plate 128 is opened into the chamber 101. Piping lines 165 and 166 are connected to the gas flow path 164. The pipe 165 is connected to _B 2 _{H 6} gas supply source 167 for supplying the _B 2 _{H 6} gas is boron-containing gas, the pipe 166 for supplying the He gas is an inert gas, He gas supply source 168 Is connected. The pipe 165 is provided with a flow control 165a such as a mass flow controller and an on-off valve 165b, and the pipe 166 is provided with a flow controller 166a and an on-off valve 166b.

  The second gas supply unit 162 includes a shower ring 170 provided in a ring shape along the inner wall of the processing container 1. The shower ring 170 is provided with a buffer chamber 171 provided annularly, and a plurality of gas discharge ports 172 provided so as to face the inside of the chamber 101 at equal intervals from the buffer chamber 171. In the buffer chamber 171, a gas supply path 173 toward the chamber 101 is formed. The pipes 174 and 175 are branched from the pipes 165 and 166, respectively, and the pipes 174 and 175 join together and are connected to the buffer chamber 171 of the shower ring 170. The pipe 174 is provided with a flow rate control 174 a and an on-off valve 174 b, and the pipe 175 is provided with a flow rate controller 175 a and an on-off valve 175 b.

  In this example, in the first gas supply unit 161 and the second gas supply unit 162, the flow rates of the boron-containing gas and the inert gas of the same type are adjusted from the same gas supply sources 167 and 168, respectively. The gas is supplied and discharged into the chamber 101 from the center of the microwave transmitting plate 128 and the periphery of the chamber 101, respectively. Note that, depending on the type of film formation process, separate gases can be supplied from the first gas supply unit 161 and the second gas supply unit 162, and the flow ratio or the like of them can be adjusted individually.

  For example, a processing gas having a flow rate in the range of 1000 to 10000 sccm is preferably supplied from the first and second gas supply units 161 and 162, for example, in order to improve the deposition rate of the boron film. .

The gas supply unit 106 includes all of the first and second gas supply units 161 and 162, the B ₂ H ₆ gas supply source 167, the He gas supply source 168, piping, a flow rate controller, a valve, and the like.

  The film forming apparatus 200 has a control unit 150. The control unit 150 controls each component of the film forming apparatus 200, such as valves, a flow rate controller, a microwave generator 140, a heater power supply, a high frequency power supply 109, and the like. The control unit 150 includes a main control unit having a CPU, an input device, an output device, a display device, and a storage device. In the storage device, a program for controlling a process to be executed by the film forming apparatus 200, that is, a storage medium storing a processing recipe is set, and the main control unit determines a predetermined processing recipe stored in the storage medium. Are controlled to cause the film forming apparatus 200 to perform predetermined processing based on the processing recipe.

  In the film forming apparatus 200 configured as described above, first, the gate valve G is opened, the wafer W is carried into the chamber 101, and the wafer W is placed on the mounting table 102 and the gate valve G is closed. Then, the inside of the chamber 10 is exhausted by the exhaust device 13, and the pressure in the chamber 101 is regulated to, for example, 0.67 Pa to 33.3 Pa (5 mTorr to 250 mTorr) by the pressure adjustment valve. Then, the wafer W is stabilized at the film forming temperature, for example, a temperature within the range of 60 ° C. to 500 ° C. by the heater 105 in the mounting table 120.

Next, B ₂ H ₆ gas (B ₂ H ₆ concentration: 10 vol%, He gas dilution) and He gas are flowed from the first gas supply unit 161 and the second gas supply unit 162 at, for example, 200 sccm and 800 sccm, respectively. , And introduce microwaves of, for example, 2 to 5 kW into the chamber 101 from the microwave generator 140 of the microwave plasma source 120. At this time, a bias voltage is applied from the high frequency power supply 109 to the mounting table 102.

  A region directly below the lower surface of the dielectric window 41 is a plasma generation region where plasma is generated, and the plasma electron temperature is relatively high in that region. The plasma in the plasma generation region diffuses downward to form a plasma diffusion region. The plasma diffusion region is a region where the plasma electron temperature is relatively low, and the wafer W on the mounting table 102 is present in the diffusion region. The microwave plasma is essentially radical-based and can generate a high-density plasma, so the wafer W has a low electron temperature and a radical-based, low damage and high-density plasma acting to form a good boron film. It can be membrane.

At this time, when the reaction gas is formed by diluting the boron-containing gas with an inert gas (He gas or Ar gas) or hydrogen gas using a boron-containing gas such as B ₂ H ₆ gas, for example, the above-described film formation The boron film formed on the surface of the wafer W under the conditions (film forming pressure, film forming temperature) inevitably includes hydrogen in the range of about 5 to 15 atomic% in addition to boron. On the other hand, oxygen and nitrogen are in such an extent that these components present in the atmosphere are taken as unavoidable components, and the atomic concentration in the boron film is less than 1.0 atomic%.

  After forming a boron film having a predetermined thickness, the supply of B 2 H 6 gas from the gas supply unit 106 is stopped, and the inside of the chamber 101 is purged with He gas. Subsequently, the inside of the processing container 2 is evacuated to a predetermined pressure, the inside of the chamber 101 is set to a predetermined vacuum atmosphere, the gate valve G is opened, and the wafer W on which the boron film is formed Take it out.

  Note that another additive gas may be supplied in addition to the boron-containing gas to form a boron-based film in which another element is intentionally added in addition to boron. Further, as the film forming apparatus, in addition to the apparatus for performing microwave plasma CVD as described above, using a parallel plate type plasma processing apparatus as shown in FIG. it can.

[Example of processing apparatus capable of forming a boron film and planarizing treatment]
Next, an example of a processing apparatus capable of forming a boron film and performing planarization processing in the same chamber will be described.
FIG. 19 is a cross-sectional view showing such a processing apparatus. The basic configuration of the processing apparatus 400 of FIG. 19 is the same as that of the processing apparatus 100 of FIG. 10, and the same components as those of the processing apparatus 100 of FIG.

A different point from the processing apparatus 100 of the processing apparatus 400 of this example is that, in addition to the CF-based gas and the oxygen-containing gas, a boron-containing gas (B ₂ H ₆ gas) and an inert gas (He) Gas supply mechanism 410 capable of supplying gas).

That is, like the gas supply mechanism 40, the gas supply mechanism 410 is provided in the CF-based gas supply source 42, the oxygen-containing gas supply source 43, the pipes 44 and 45 extending from these gas supply sources, and the pipe 44 Besides having a flow controller 46 and an on-off valve 47, a flow controller 48 and an on-off valve 49 provided in the pipe 45, a B ₂ H ₆ gas supply source 411, a He gas supply source 412, these gas supply sources The pipes 413 and 414 respectively extending therefrom, the flow controller 415 and the on-off valve 416 provided on the pipe 413, and the flow controller 417 and the on-off valve 418 provided on the pipe 414.

With such a configuration, a boron film is formed by plasma generated by applying high frequency power from the first high frequency power supply 52 to the mounting table 20 while supplying B ₂ H ₆ gas and He gas into the chamber 10, Next, after the chamber 10 is purged, the planarization process can be performed by plasma generated by applying high-frequency power from the first high-frequency power supply 52 to the mounting table 20 while supplying CF-based gas and oxygen-containing gas.

  According to the processing apparatus 400, the deposition of the boron film and the planarization process can be performed in one chamber, and the boron film with excellent flatness can be formed with extremely high efficiency.

<Other application>
As mentioned above, although embodiment of this invention was described, this invention can be variously deformed within the range of the thought of this invention, without being limited to the said embodiment.

  For example, although the hard mask is shown as the application of the boron-based film in the above embodiment, the present invention is not limited to this, and the thin film application can also be applied to other applications such as a barrier film for diffusion prevention.

  In the above embodiments, the boron film has been mainly described, but in the principle of the present invention, a boron-based film in which another additive element is intentionally added to boron, such as a boron-rich BN film or a boron-rich film It is needless to say that even a BC film can provide a surface with good flatness according to the present invention.

  Furthermore, the processing apparatus for planarization described in the above embodiment, the film formation apparatus for forming a boron-based film, the processing system for processing and forming a boron-based film, and the processing apparatus It goes without saying that the present invention can be practiced with devices having other various configurations, which are merely illustrative.

10, 101; chamber 13, 124; exhaust device 20, 102; mounting table 30; shower head 40; gas supply mechanism 50; high frequency power supply device 60, 150; control unit 100, 400; processing device 106; gas supply unit 120 Microwave plasma source 200; film forming apparatus 300; processing system W; semiconductor wafer

Claims (21)

A boron-based film planarization method for planarizing the surface of a boron-based film mainly composed of boron formed on a substrate, comprising:
What is claimed is: 1. A method of planarizing a boron-based film, comprising the step of performing plasma processing using a processing gas containing a CF-based gas containing C and F and an oxygen-containing gas to a boron-based film.   The method for planarizing a boron-based film according to claim 1, further comprising the step of ashing the remaining carbon-based by-product after the step of performing the plasma treatment. _{3. The} method according to claim 2, wherein the ashing process is performed by plasma of O ₂ gas.   4. The method for planarizing a boron-based film according to claim 2, further comprising the step of wet-cleaning the substrate on which the boron-based film is formed after the ashing step.   The said CF type | system | group gas is only the gas containing C and F, only the gas containing C, F, and H, or these both, The any one of Claim 1 to 4 characterized by the above-mentioned. The planarization method of the boron-type film | membrane as described in a term. 6. The method according to claim 5, wherein the CF gas is at least one selected from the group consisting of C ₄ F ₆ , C ₄ F ₈ , and CH ₂ F _2. . The method for planarizing a boron-based film according to any one of claims 1 to 6, wherein the oxygen-containing gas in the plasma processing step is an O ₂ gas.   8. The method of planarizing a boron-based film according to any one of claims 1 to 7, wherein the step of performing the plasma processing is performed by a parallel plate type plasma processing apparatus.   9. The flat surface of a boron-based film according to any one of claims 1 to 8, wherein in the step of performing the plasma processing, a high frequency bias voltage is applied to a substrate on which the boron-based film is formed. Method.   10. The method of planarizing a boron-based film according to any one of claims 1 to 9, wherein the boron-based film is a boron film containing boron and unavoidable impurities.   11. The method of planarizing a boron-based film according to any one of claims 1 to 10, wherein the boron-based film is a film formed by plasma CVD.   12. The method of claim 11, wherein the boron-based film is a film formed by microwave plasma CVD. Forming a boron-based film mainly composed of boron on a substrate;
Planarizing the surface of the boron-based film;
The step of planarizing the surface of the boron-based film is characterized in that the boron-based film is subjected to plasma processing using a processing gas containing a CF-based gas containing C and F and an oxygen-containing gas. Method of forming a boron-based film.   14. The method of forming a boron-based film according to claim 13, wherein the step of forming the boron-based film comprises forming a boron film containing boron and unavoidable impurities as the boron-based film.   15. The method for forming a boron-based film according to claim 13, wherein the step of forming the boron-based film is performed by plasma CVD using a boron-containing gas.   The method for forming a boron-based film according to claim 15, wherein the step of forming the boron-based film is performed by microwave plasma CVD.   17. The process according to claim 15, wherein in the step of depositing the boron-based film, a gas selected from the group consisting of diborane gas, boron trichloride gas, and alkyl borane gas is used as a boron-containing gas. Of forming a boron-based film.   The method of forming a boron-based film according to any one of claims 13 to 17, wherein the step of forming the boron-based film and the step of planarizing are performed in situ.   The method for forming a boron-based film according to claim 18, wherein the step of forming the boron-based film and the step of forming the boron-based film are performed in the same chamber.   The method for forming a boron-based film according to any one of claims 13 to 19, wherein the step of forming the boron-based film and the step of planarizing are repeated a predetermined number of times.   21. The boron-based film according to claim 20, wherein in the step of forming the boron-based film, the film thickness of one time is set to such a thickness that a desired flatness can be obtained by the planarization process. How it is formed.