JP2019102508A - Method and apparatus for forming boron-based film - Google Patents

Abstract

To provide a technology capable of obtaining a boron-based film having a flat surface without film loss and impurity contamination as much as possible.SOLUTION: A method of forming a boron-based film for forming a boron-based film mainly composed of boron on a substrate, includes steps of: forming a boron-based film on a substrate by CVD using a processing gas containing a boron-containing gas; and planarizing by plasma of a rare gas a surface of the boron-based film.SELECTED DRAWING: Figure 4

Description

  The present invention relates to a method and apparatus for 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 the boron film of boron alone has excellent characteristics among the boron-based films, but the boron film formed by CVD has the surface unevenness after the film formation. Large, for example, the surface roughness represented by the average surface roughness (Ra) or the root mean square roughness (RMS) may exceed 2 nm, which is 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 the application to semiconductor devices, there is a need for a technique for obtaining a boron-based film with an RMS of 2 nm or less, and further 1 nm or less, with film loss and impurity contamination as small as possible. Has not yet been established.

  Therefore, an object of the present invention is to provide a technology capable of obtaining a boron-based film having a flat surface without film loss and impurity contamination as much as possible.

  In order to solve the above problems, a first aspect of the present invention is a method of forming a boron-based film in which a boron-based film mainly composed of boron is formed on a substrate, and a processing gas containing a boron-containing gas on the substrate Providing a step of forming a boron-based film by CVD using the following step, and thereafter a step of planarizing the surface of the boron-based film with plasma of a rare gas; Do.

In the method of forming a boron-based film, argon gas can be used as a rare gas in the step of the planarization treatment. Further, in the step of performing the planarization process, a high frequency bias voltage may be applied to the substrate to draw rare gas ions in the plasma into the substrate. In this case, the power density of the high frequency bias voltage is preferably 0.4 to 1.7 W / cm ² . The processing time of the step of planarizing may be in the range of 10 to 600 sec.

In the step of forming the boron-based film, a boron film containing boron and unavoidable impurities can be formed as the boron-based film. In the step of forming the boron-based film, a B ₂ H ₆ gas can be used as a boron-containing gas.

  In the step of forming the boron-based film, the boron film can be formed by plasma CVD. In this case, in the step of forming the boron-based film, a rare gas can be further contained as the processing gas, and argon gas and / or helium gas can be used as the rare gas. The step of forming the boron-based film and the step of performing the planarization process can be performed continuously in the same apparatus, and the steps of forming the boron-based film and the step of performing the planarization process are as follows. It can be continuously performed in the same apparatus without stopping the plasma while supplying the rare gas. The step of forming the boron-based film is preferably performed without applying a bias voltage to the substrate, and the step of planarizing is preferably performed by applying a bias voltage to the substrate. The step of forming the boron-based film and the step of performing the planarization process can be performed by microwave plasma.

  The step of forming the boron-based film and the step of performing the planarization process can be performed at a pressure of 0.67 to 33.3 Pa and a temperature of 500 ° C. or less.

  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. Further, in the step of forming the boron-based film, it is preferable to set the film thickness at one time to 10 nm or more.

  A second aspect of the present invention is a boron-based film forming apparatus for forming a boron-based film mainly composed of boron on a substrate, comprising: a chamber for accommodating the substrate; and a mounting table for supporting the substrate in the chamber. A gas supply mechanism for supplying a processing gas containing at least a boron-containing gas and a rare gas into the chamber, an exhaust device for exhausting the chamber, a plasma generating means for generating plasma in the chamber, A processing gas containing the boron-containing gas is supplied into the chamber by a gas supply mechanism, and a plasma of a gas containing the boron-containing gas is generated by the plasma generation means to form the boron-based film, A processing mechanism including the rare gas is supplied into the chamber by a supply mechanism, and the plasma generation unit is configured to plasma the gas including the rare gas. To generate providing forming apparatus boron-based film, characterized in that a control unit for controlling to perform a flattening treatment on the surface of the boron-based film.

  The apparatus for forming a boron-based film further includes high-frequency bias voltage application means for applying a high-frequency bias voltage to the substrate through the mounting table, and the control unit forms the boron-based film. The high frequency bias voltage application means may be stopped, and the high frequency bias voltage application means may be controlled to apply a high frequency bias voltage to the substrate by the high frequency bias voltage application means in the flattening process.

  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.

  According to the present invention, after a boron-based film is formed on the substrate by CVD using a processing gas containing a boron-containing gas, the surface of the boron-based film is planarized by plasma of a rare gas. The surface of the boron-based film can be planarized by the physical action of Therefore, a boron-based film having a flat surface can be obtained without occurrence of film loss and impurity contamination as much as possible, and a boron-based film suitable for the application of a semiconductor device such as a hard mask can be formed.

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. (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 flow chart which shows a boron system film formation method concerning a 1st embodiment of the present invention. It is a SEM image which shows the state of a boron film when the high frequency bias applied to a board | substrate is 0 W, 50 W, and 150 W at the time of film-forming of a boron film. It is a flow chart which shows a boron system film formation method concerning a 2nd embodiment of the present invention. It is sectional drawing which shows an example of the boron type film formation apparatus used for implementation of the boron type film formation method of this invention. It is a chart which shows an example of the processing sequence in the boron system film formation apparatus of FIG. It is sectional drawing which shows the other example of the boron type film formation apparatus used for implementation of the boron type film formation method of this invention. It is a SEM photograph of the sample which formed the boron film into a film formation, and the sample which performed Ar plasma processing. It is an AFM image of a sample on which a boron film is formed, a sample subjected to He plasma processing, and a sample subjected to Ar plasma processing. It is a figure which shows the relationship between the processing time of Ar plasma processing of boron film, and surface roughness RMS. It is a figure which shows the relationship between the high frequency bias and surface roughness RMS of Ar plasma processing of a boron film. A SEM photograph of a 1.5 μm thick film in the as depo state deposited by plasma CVD and a boron film having a thickness of 300 nm deposited by plasma CVD, followed by five cycles of repeated Ar plasma processing set It is a SEM photograph of a boron film of A change in RMS due to the thickness of the boron film as depo and a change in RMS due to the thickness after Ar film processing after forming the boron film, and after a boron film with a thickness of 300 nm is formed Ar It is a figure which shows the value of RMS at the time of repeating the set which performs a plasma processing 5 cycles.

  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.
A boron-based film is considered promising as a hard mask, and is conventionally deposited by CVD. Among boron-based films, it is known that a boron-only film having boron alone has particularly excellent characteristics, but the boron-based film formed by CVD has large surface irregularities after film formation, for example, an average The surface roughness represented by the surface roughness (Ra) and the root mean square roughness (RMS) may exceed 2 nm in some cases, which is a factor limiting the application to a fine pattern of 14 nm or less. Therefore, a technique for forming a boron-based film having a flat surface is required.

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. 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.

This is because, in the case of H ₂ plasma processing, even if hydrogen ions generated by H ₂ plasma are supplied to the boron film, they do not react with the boron film, so the surface state of the boron film does not change, while NF ₃ plasma In the case of the treatment, it is considered that NF ₃ dissociates into F and NF and reacts with boron (B) to etch the boron film and to make the surface rougher.

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. 3A 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) + ultrasonication: 30 min) Fig. 3 (b) shows the initial (as depo) boron film, O ₂ annealing plasma treatment (O ₂ plasma 10 min), and cleaning treatment (pure water (DIW) + ultrasonic treatment: 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 the surface of the boron film is oxidized to form an oxide film on the surface in the O ₂ annealing process and the O ₂ plasma process, but it is only oxidized as a whole, and the oxide film is removed by cleaning. Also, it is considered that the flatness of the surface of the boron film 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.

  In addition, when it is intended to planarize a boron-based film by a chemical method, it is expected that film reduction and impurity contamination will occur, but in applications of semiconductor devices, it is also required that film reduction and impurity contamination be minimized.

  In view of the above, the present inventors have considered carrying out a planarization process after forming a boron-based film by using a physical method instead of a chemical method which might cause film loss or impurity contamination. As a result, it was thought that physical treatment with noble gas ions was effective.

  That is, after forming a boron-based film by CVD, plasma of a rare gas is generated, and rare gas ions are caused to act on the surface of the boron-based film under predetermined conditions, thereby minimizing film loss and impurity contamination. It has been found that a boron-based film having a flat surface is obtained and is applicable to a semiconductor device.

First Embodiment of Method of Forming Boron-Based Film
Next, a first embodiment of a method of forming a boron-based film will be described. FIG. 4 is a flowchart showing a first embodiment of a method of forming a boron-based film.

  In the method of forming a boron-based film according to the present embodiment, a step of forming a boron-based film on a target substrate by CVD (step 1), and then, the surface of the formed boron-based film is treated with a rare gas. And (2) performing a planarization process by plasma.

  The film formation of the boron-based film by CVD in step 1 may be either thermal CVD or plasma CVD, but plasma CVD is particularly preferable in which a boron-based film having a good film quality can be obtained. The plasma CVD plasma is not particularly limited, and may be a capacitively coupled plasma or an inductively coupled plasma, but it is a low electron temperature and radical-based, and can be formed by microwave plasma CVD capable of generating high-density plasma with low damage. Particularly preferred are membranes.

  A boron-based film formed by CVD, particularly plasma CVD, has a characteristic of high etching resistance, and is applied to a hard mask taking advantage of such a characteristic. Such a boron-based film is formed on a semiconductor wafer (hereinafter simply referred to as a wafer) in which a film to be etched is formed on a semiconductor substrate such as Si as a substrate to be processed.

  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 formed by CVD mainly contains about 5 to 15 at% of hydrogen (H) as an unavoidable impurity derived from a film forming material and the like in the film.

  When forming a boron-based film by CVD, a processing gas containing a boron-containing gas is used. When forming a boron-based film by plasma CVD, it is preferable to contain a rare gas for plasma excitation as a processing gas. In the case of using a boron-based film in which another element is added to boron, a gas containing an element to be further added is used as a processing gas. The processing gas may further contain hydrogen 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.

  When forming a boron-based film, the pressure is preferably in the range of 0.67 Pa to 33.3 Pa (5 mTorr to 250 mTorr), and the temperature is preferably 500 ° C. or less (more preferably in the range of 60 to 500 ° C.).

  The boron-based film formed by CVD, particularly plasma CVD, has a large surface roughness as deposited (as depo), and the surface roughness RMS becomes a value exceeding 2 nm. In the recent etching processing technology, the final pattern dimension is miniaturized to about 10 nm by double patterning, and considering application to a hard mask, the surface roughness RMS is required to be 2 nm or less, and further 1 nm or less.

  Therefore, the planarization process using the rare gas plasma in step 2 is performed on the boron-based film formed by CVD. The planarization process is performed by generating plasma of a rare gas under predetermined conditions and causing rare gas ions to act on the surface of the boron-based film. Thus, the surface of the boron-based film is planarized by the physical action of the rare gas ions. The pressure and temperature at this time are preferably 0.67 Pa to 33.3 Pa (5 mTorr to 250 mTorr), 500 ° C. or less (more preferably in the range of room temperature (25 ° C.) to 500 ° C.). Moreover, 10 to 600 sec is preferable, and 60 to 180 sec is more preferable.

  Ar, Kr, Xe, He or the like can be used as a rare gas in the planarization treatment. In order to exert the flattening effect effectively, it is preferable that the number of atoms is large, and Ar is preferable in terms of availability and the like.

Further, from the viewpoint of enhancing the action of the rare gas ions to the boron-based film, it is preferable to apply a high frequency bias to the substrate to be treated to draw the rare gas ions into the substrate to be treated. The power of the high frequency bias at this time is preferably high, and is preferably 300 W or more, more preferably 600 W or more. Moreover, although an upper limit is based also on the restriction | limiting on an apparatus, 10 kW or less is preferable and 1200 W or less is more preferable. Power density is preferably ^{0.4~14W / cm 2, 0.4~1.7W / cm} 2 is more preferable. More preferably, it is 0.8 to 1.7 W / cm ² .

  However, when depositing the boron-based film in step 1 by plasma CVD, it is preferable not to apply a high frequency bias. By applying the high frequency bias, there is a possibility that deterioration of film quality and surface roughness of the boron-based film or film peeling from the vicinity of the interface may occur. Actually, the state of the boron film when the high frequency bias applied to the substrate is 0 W, 50 W, and 150 W using the apparatus of FIG. 7 described later and the boron film is formed by microwave plasma CVD is the SEM of FIG. As shown in the photograph, it was confirmed that the application of the high frequency bias resulted in deterioration of the film quality and surface roughness and film peeling from the vicinity of the interface.

  As described above, after forming the boron-based film, the surface roughness RMS of the boron-based film is 2 nm in the range of up to about 300 nm by performing the flattening process with a rare gas plasma. Further, the thickness can be made 1 nm or less. In addition, since the planarization treatment is treatment with a rare gas ion, no chemical reaction occurs, and film reduction and impurity contamination hardly occur. In addition, by using Ar gas having a large atomic weight as a rare gas, the planarization effect can be increased. Also, Ar gas is easy to obtain.

  Steps 1 and 2 can be performed continuously in the same chamber. Thus, a boron-based film can be formed with high throughput. In particular, when a boron-based film is formed by plasma CVD, the plasma of a rare gas is ignited in step 1 to introduce a boron-containing gas or the like to form a boron-based film, and then the plasma of the noble gas is maintained. The planarization process using the rare gas ions in step 2 can be performed only by stopping the boron-containing gas or the like.

  At this time, the pressure is within the range of 0.67 Pa to 33.3 Pa (5 mTorr to 250 mTorr), and the temperature is 500 ° C. It is preferable to carry out within the following range, and it is preferable to carry out step 1 and step 2 continuously at the same temperature.

Second Embodiment of Method of Forming Boron-Based Film
Next, a second embodiment of a method of forming a boron-based film will be described. FIG. 6 is a flowchart showing a second embodiment of a method of forming a boron-based film.

  As described in the first embodiment, if the film thickness of the boron-based film is about 300 nm or less, if the film formation of the boron-based film in step 1 and the planarization process in step 2 are performed once, the RMS is 2 nm Although the thickness can be made 1 nm or less, if the thickness of the boron-based film to be formed becomes thicker, the growth of nuclei proceeds, the surface waviness and the like become larger, and the surface roughness tends to become larger. When the thickness becomes 1 μm or more, the value of RMS may exceed 5 nm at as depo. In such a case, it is difficult to reduce the RMS to 2 nm or less even if the flattening process using the rare gas plasma of step 2 is performed after the formation of the boron-based film of step 1.

  Therefore, in the present embodiment, a step (step 11) of depositing a predetermined thickness, preferably a thickness of a boron-based film on a substrate to be treated to a desired flatness by a planarization process (step 11) And the step of planarizing the surface of the formed boron-based film with plasma of a rare gas (step 12) is repeated a predetermined number of times. As a result, even if the total thickness of the boron-based film is large, it is possible to form a boron-based film having high RMS surface flatness of 2 nm or less.

  The present embodiment is effective when the total film thickness of the boron-based film is 1 μm or more in which the growth of nuclei proceeds and the surface roughness increases. The number of repetitions is preferably 5 or more, although it depends on the total thickness of the boron-based film.

  In the present embodiment, step 11 can be performed in the same manner as step 1 of the first embodiment, and step 12 can be performed in the same manner as step 2 of the first embodiment. The film thickness of one film forming process in step 11 is preferably 300 nm or less. However, if the thickness of one film is too thin, the number of repetitions increases and the process takes time, so 10 nm or more is preferable.

<Example of boron-based film forming apparatus>
Next, an example of a boron-based film forming apparatus will be described.
FIG. 7 is a cross-sectional view showing an example of a boron-based film forming apparatus. The boron-based film forming apparatus 100 of this example is configured as a microwave plasma apparatus for performing a planarization process after forming a boron film as a boron-based film.

  The boron-based film forming apparatus 100 has a substantially cylindrical chamber 1 which is airtight and grounded. The chamber 1 is made of, for example, a metal material such as aluminum and its alloy. A microwave plasma source 20 is provided at the top of the chamber 1. The microwave plasma source 20 is configured, for example, as an RLSA (registered trademark) microwave plasma source.

  A circular opening 10 is formed in a substantially central portion of the bottom wall of the chamber 1, and the bottom wall is provided with an exhaust chamber 11 communicating with the opening 10 and projecting downward.

  In the chamber 1, a disk-shaped mounting table 2 made of ceramic such as AlN for horizontally supporting a wafer W as a substrate to be processed is provided. The mounting table 2 is supported by a support member 3 made of ceramic such as cylindrical AlN which extends upward from the center of the bottom of the exhaust chamber 11. In addition, a heater 5 of a resistance heating type is embedded in the mounting table 2, and the heater 5 generates heat when power is supplied from a heater power supply (not shown), whereby the wafer W is transferred via the mounting table 2. It is heated to a predetermined temperature. Further, an electrode 7 is embedded in the mounting table 2, and a high frequency power supply 9 for bias voltage application is connected to the electrode 7 via a matching unit 8. The bias voltage application high frequency power source 9 applies high frequency power (high frequency bias) of 3 to 13.56 MHz, for example, 3 MHz, to the mounting table 2. The matching unit 8 matches the load impedance to the internal (or output) impedance of the high frequency power supply 9 for bias voltage application, and when the plasma is generated in the chamber 1, the internal impedance of the high frequency power supply 9 for bias voltage application And the load impedance appear to match.

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

  An exhaust pipe 23 is connected to the side surface of the exhaust chamber 11, and an exhaust device 24 including a vacuum pump, an automatic pressure control valve, and the like is connected to the exhaust pipe 23. By operating the vacuum pump of the exhaust device 24, the gas in the chamber 1 is uniformly discharged into the space 11a of the exhaust chamber 11, and exhausted through the exhaust pipe 23, and the inside of the chamber 1 is predetermined by the automatic pressure control valve. Controlled to the degree of vacuum.

  A loading / unloading port 25 for loading / unloading the wafer W to / from a vacuum transfer chamber (not shown) adjacent to the boron-based film forming apparatus 100 is provided on the side wall of the chamber 1. Is opened and closed by the gate valve 26.

  The upper portion of the chamber 1 is an opening, and the peripheral edge of the opening is a ring-shaped support 27. The microwave plasma source 20 is supported by the support 27.

The microwave plasma source 20 includes a disk-shaped microwave transmitting plate 28 made of a dielectric such as quartz or ceramic such as Al ₂ O ₃ , a planar slot antenna 31 having a plurality of slots, and a wave retarding member 33. A coaxial waveguide 37, a mode converter 38, a waveguide 39, and a microwave generator 40 are provided.

  The microwave transmission plate 28 is airtightly provided on the support 27 via the seal member 29. Therefore, the chamber 1 is kept airtight.

  The planar slot antenna 31 has a disk shape corresponding to the microwave transmission plate 28, and is provided in close contact with the microwave transmission plate 28. The planar slot antenna 31 is locked to the upper end of the side wall of the chamber 1. The planar slot antenna 31 is formed of a disc made of a conductive material.

  The planar slot antenna 31 is made of, for example, a copper plate or an aluminum plate whose surface is plated with silver or gold, and a plurality of slots 32 for radiating microwaves are formed to penetrate in a predetermined pattern. The pattern of the slots 32 is suitably set so that the microwaves are radiated evenly. For example, as an example of the pattern, it can be mentioned that a plurality of pairs of slots 32 are concentrically arranged with the two slots 32 arranged in a T-shape as a pair. The length and arrangement interval of the slots 32 are determined according to the effective wavelength (λg) of the microwaves, and for example, the slots 32 are arranged such that their interval is λg / 4, λg / 2 or λg. The slot 32 may have another shape such as a circular shape or an arc shape. Further, the arrangement form of the slots 32 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 member 33 is provided in close contact with the upper surface of the planar slot antenna 31. The wave retarding member 33 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 33 has a function to make the planar slot antenna 31 smaller by shortening the wavelength of the microwave than in vacuum.

  The thicknesses of the microwave transmission plate 28 and the retardation member 33 are adjusted such that the retardation plate 33, the planar slot antenna 31, the microwave transmission plate 28, and the equivalent circuit formed of plasma satisfy the resonance condition. By adjusting the thickness of the wave retardation member 33, the phase of the microwave can be adjusted, and the thickness of the junction of the planar slot antenna 31 can be adjusted so that it becomes a "flapping" of the standing wave. The reflection of microwaves is minimized, and the radiant energy of microwaves is maximized. Moreover, the interface reflection of a microwave can be prevented by making the wave retarding material 33 and the microwave transmission board 28 into the same material.

  The planar slot antenna 31 and the microwave transmission plate 28, and the wave retarding member 33 and the planar slot antenna 31 may be spaced apart.

  A cooling jacket 34 made of a metal material such as aluminum, stainless steel, copper or the like is provided on the upper surface of the chamber 1 so as to cover the planar slot antenna 31 and the wave retardation member 33. In the cooling jacket 34, a cooling water channel 34a is formed, and the retardation material 33, the planar slot antenna 31, and the microwave transmitting plate 28 are cooled by allowing the cooling water to flow therethrough. .

  The coaxial waveguide 37 is inserted from above the center formed opening of the upper wall of the cooling jacket 34 toward the microwave transmission plate 28. The coaxial waveguide 37 is formed by concentrically arranging a hollow rod-like inner conductor 37a and a cylindrical outer conductor 37b. The lower end of the inner conductor 37 a is connected to the planar slot antenna 31. The coaxial waveguide 37 extends upward. The mode converter 38 is connected to the upper end of the coaxial waveguide 37. One end of a horizontally extending rectangular waveguide 39 is connected to the mode converter 38. The microwave generator 40 is connected to the other end of the waveguide 39. A matching circuit 41 is interposed in the waveguide 39.

  The microwave generator 40 generates microwaves having a frequency of 2.45 GHz, for example, and the generated microwaves propagate in the waveguide 39 in the TE mode, and the mode converter 38 starts the vibration mode of the microwaves from the TE mode It is converted to the TEM mode and propagates toward the wave retarding member 33 through the coaxial waveguide 37. Then, the microwaves radially spread radially outward in the inside of the retardation member 33, are radiated from the slots 32 of the planar slot antenna 31, pass through the microwave transmission plate 28, and are transmitted through the microwaves in the chamber 1. An electric field is generated in the region directly below the plate 28 to generate microwave plasma. In a part of the lower surface of the microwave transmitting plate 28, an annular recess 28a is formed on a taper to facilitate generation of a standing wave by the introduced microwave, and the microwave plasma is efficient It can be generated well.

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 microwave power is preferably 2000 to 5000 W, and the power density is preferably 2.8 to 7.1 W / cm ² .

The boron-based film forming apparatus 100 has a gas supply mechanism 6 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.

In addition, the processing gas contains a rare gas for plasma excitation and planarization processing. It may further contain hydrogen gas or the like. As a rare gas, He gas or Ar gas is used. In the following, the case of using a processing gas containing B ₂ H ₆ gas as the boron-containing gas and Ar gas and He gas as the rare gas will be described as an example.

The gas supply mechanism 6 includes a first gas supply unit 61 that discharges gas toward the center of the wafer W, and a second gas supply unit 62 that discharges gas from the outside of the wafer W. The first gas supply unit 61 includes a mode converter 38 and a gas passage 63 formed inside the inner conductor 37 a of the coaxial waveguide 37, and the gas supply port 64 at the tip of the gas passage 63 is For example, the central portion of the microwave transmission plate 28 is opened in the chamber 1. The pipes 65, 66 and 67 are connected to the gas flow path 64. The pipe 65 is connected to _B 2 _{H 6} gas supply source 68 for supplying the _B 2 _{H 6} gas is boron-containing gas, Ar gas supply source 69 for supplying Ar gas as a rare gas in the pipe 66 Connected to the pipe 67 is a He gas supply source 70 for supplying He gas which is a rare gas. The pipe 65 is provided with a flow controller 65a such as a mass flow controller and an on-off valve 65b, the pipe 66 is provided with a flow controller 66a and an on-off valve 66b, and the pipe 67 is provided with a flow controller 67a and an on-off valve A valve 67 b is provided.

  The second gas supply unit 62 includes a shower ring 71 provided in a ring shape along the inner wall of the chamber 1. The shower ring 71 is provided with a buffer chamber 72 provided annularly, and a plurality of gas discharge ports 73 provided so as to face the inside of the chamber 1 at equal intervals from the buffer chamber 72. The pipes 74, 75, and 76 are branched from the pipes 65, 66, and 67, respectively, and the pipes 74, 75, and 76 join together and are connected to the buffer chamber 72 of the shower ring 71. The pipe 74 is provided with a flow rate controller 74a and an on-off valve 74b, the pipe 75 is provided with a flow rate controller 75a and an on-off valve 75b, and the pipe 76 is provided with a flow rate controller 76a and an on-off valve 76b. ing.

  In this example, in the first gas supply unit 61 and the second gas supply unit 62, the flow rates of the same kind of boron-containing gas and rare gas from the same gas supply sources 68, 69 and 70 are respectively adjusted. , And discharged into the chamber 1 from the center of the microwave transmission plate 28 and the periphery of the chamber 1, respectively. Depending on the type of film forming process, separate gases can be supplied from the first gas supply unit 61 and the second gas supply unit 62, and the flow ratio and 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 61 and 62 in order to improve the deposition rate of the boron film, for example. .

The gas supply mechanism 6 includes the first and second gas supply units 61 and 62, a B ₂ H ₆ gas supply source 68, an Ar gas supply source 69, a He gas supply source 70, piping, a flow rate controller, a valve, etc. Includes all

  The boron-based film forming apparatus 100 has a control unit 50. The control unit 50 controls each component of the boron-based film forming apparatus 100, such as valves, a flow rate controller, a microwave generator 40, a heater power supply, a high frequency power supply 9 for bias voltage application, and the like. The control unit 50 includes a main control unit having a CPU, an input device, an output device, a display device, and a storage device. The storage device is set with a program for controlling processing to be executed by the boron-based film forming apparatus 100, that is, a storage medium storing a processing recipe, and the main control unit is configured to store predetermined data stored in the storage medium. A processing recipe is called, and based on the processing recipe, control is performed to cause the boron-based film forming apparatus 100 to perform predetermined processing.

  In performing the method of the first embodiment in the boron-based film forming apparatus 100 configured as described above, first, the gate valve 26 is opened, and the wafer W is carried into the chamber 1 and the mounting table 2 And the gate valve 26 is closed.

  Then, for example, the boron film is formed and planarized by a processing sequence as shown in FIG.

As shown in FIG. 8, the mounting table temperature is set to 500 ° C. or less (60 to 500 ° C.), for example 300 ° C., and Ar gas and He gas are first flowed into the chamber 1 to perform cycle purge (ST1). After stabilizing the temperature of the wafer W by setting the pressure in the chamber 1 by He and He gas to, for example, about 400 mTorr, 2000 to 5000 W (2.8 to 7.1 W / cm ² ), for example, 3500 W from the microwave generator 40 Plasma ignition (ST2) is performed by introducing a microwave of (5.0 W / cm ² ), and then the microwave power is maintained at the same value as at the time of ignition, and the pressure in the chamber 1 is 0.67 Pa to 33. The pressure is adjusted to 3 Pa (5 mTorr to 250 mTorr), for example, 6.7 Pa (50 mTorr), and the first gas supply unit 61 and the second gas supply A boron film is formed (ST3) by supplying B ₂ H ₆ gas (B ₂ H ₆ concentration: 10 vol%, diluted with He gas) at a flow rate of 100 to 1000 sccm, for example 500 sccm, from the supply unit 62. At this time, Ar gas and He gas are supplied at a total flow rate of 100 to 1000 sccm, for example, 500 sccm. The deposition time of the boron film is appropriately set in accordance with the film thickness. In addition, when the boron film is formed, deterioration of the film quality and surface roughness of the boron film and film peeling from the vicinity of the interface occur without applying the high frequency bias from the high frequency power supply 9 for bias voltage application. To prevent that.

After completion of the formation of the boron film, the B ₂ H ₆ gas is stopped while maintaining the plasma, and He gas and Ar gas are introduced while evacuating the chamber 1 to purge the chamber 1 (ST 4), At that time, the microwave power is set to 2000 to 5000 W (power density 2.8 to 7.1 W / cm ² ), for example 3000 W (4.2 W / cm ² ), and 300 to 1200 W (from high frequency power source for bias voltage application). High frequency bias of 0.4 to 1.7 W / cm ² ), for example 600 W (0.8 W / cm ² ) is applied, and gas is supplied at a flow rate of 100 to 2000 sccm, for example 500 sccm as Ar gas only, in Ar plasma The planarization process (ST5) by Ar ion of The time for the planarization process is 10 to 600 sec, for example, 60 sec. At this time, pressure and temperature are 0.67 Pa to 33.3 Pa (5 mTorr to 250 mTorr), 500 ° C. or less (room temperature (25 ° C. to 500 ° C. range), for example, 6.7 Pa (50 mTorr), 300 ° C. Do. The temperature at this time is preferably the same as that for forming the boron film.

  After completion of the planarization process, the microwave generator 40 and the high frequency power supply 9 for bias voltage application are turned off to stop the plasma, purge with He gas and Ar gas in the chamber 1 (ST6) is performed, and the process is completed.

  As described above, the surface roughness RMS of the boron film can be reduced to 2 nm or less, and further to 1 nm or less by performing planarization by plasma of a rare gas after forming the boron film. In addition, by using Ar gas having a large atomic weight as the rare gas, the planarization effect is large.

  When the method of the second embodiment is carried out in the boron-based film forming apparatus 100, after performing the above-mentioned ST1 to ST5, the microwave generator 40 and the high frequency power supply 9 are turned off to stop the plasma, and the plasma is stopped again. ST1 to ST5 may be repeated a predetermined number of times to carry out the ST1 to ST5, and the purge of ST6 may be finally performed, or after the ST1 to ST5 are performed, without cutting the microwave generator 40. The steps ST3 to ST5 may be repeated a predetermined number of times, and the purge of the step ST6 may be finally performed, such that the steps ST3 to ST5 are performed again while maintaining the plasma.

  After the boron film is formed to a thickness of about 300 nm, the boron film is formed by plasma CVD, and then plasma of Ar gas which is a rare gas is generated to perform the flattening process of the boron film once, thereby surface roughness. Flattening with an RMS of 2 nm or less, or even 1 nm or less can be realized. Further, since the treatment is performed with a rare gas ion, no chemical reaction occurs, and film reduction and impurity contamination hardly occur.

  When the thickness of the boron film is larger, for example, 1 μm or more, the boron film should be formed to a thickness that can obtain a desired flatness by planarization processing by plasma CVD. By repeating the planarization process of the boron film a plurality of times, planarization with an RMS of 2 nm or less can be realized.

  Furthermore, in the boron-based film forming apparatus 100, since the film formation and the planarization process of the boron film can be performed in one chamber 1, these processes can be performed with high throughput. At this time, by making the temperatures of these processes the same, the time for changing the temperature becomes unnecessary, and the throughput is further improved. In addition, since the film formation and the planarization process of the boron film can be continuously performed only by switching the gas in a state where the plasma of the rare gas such as Ar gas is generated, the throughput is also high in that respect.

  Furthermore, since a high frequency bias is not applied to the wafer W (mounting table 2) during the film formation of the boron film by plasma CVD, and a high frequency bias is applied during the planarization process, Deterioration of the film quality and surface roughness of the boron-based film due to high frequency bias and film peeling from the vicinity of the interface do not occur, and Ar ion or the like to the boron film is generated by applying the high frequency bias at the time of planarization. The action of the rare gas ions can be enhanced to further enhance the effect of planarization.

<Another Example of Boron-Based Film Forming Apparatus>
Next, another example of the boron-based film forming apparatus will be described.
FIG. 9 is a cross-sectional view showing another example of a boron-based film forming apparatus. The boron-based film forming apparatus 200 of this example is configured as a capacitively coupled parallel plate plasma apparatus for performing a planarization process after forming a boron film as a boron-based film.

  The boron-based film forming apparatus 200 of this example has a substantially cylindrical chamber 101 which is airtight and grounded. The chamber 101 is made of, for example, a metal material such as aluminum and its alloy.

At a bottom portion in the chamber 101, a mounting table 102 which functions as a lower electrode for horizontally supporting a wafer W which is a substrate to be processed is provided. The mounting table 102 is supported via a metal supporting member 103 and an insulating member 104 disposed on the bottom surface of the chamber 101. A resistance heating type heater 105 is embedded in the mounting table 102. The heater 105 generates heat when power is supplied from a heater power supply (not shown), whereby the wafer W is transferred through the mounting table 102. It is heated to a predetermined temperature.

  At an upper portion in the chamber 101, a gas shower head 110 functioning as an upper electrode is provided to face the mounting table 102. The gas shower head 110 is made of metal and has a disk shape. A gas diffusion space 111 is formed inside the gas shower head 110. A plurality of gas discharge holes 112 are formed on the lower surface of the gas shower head 110.

  A gas flow path 113 is connected to a central portion of the upper surface of the gas shower head 110. A gas pipe 113a constituting the gas flow path 113 is fixed to the chamber 101 via the insulating member 114, and the gas shower head 110 is supported by the chamber 101 by the gas pipe 113a.

Piping lines 165, 166 and 167 are connected to the gas flow path 113. The pipes 165 are _B 2 _{H 6} for supplying gas _B 2 _{H 6} gas supply source 168 is a boron-containing gas is connected, Ar gas supply source 169 for supplying Ar gas as a rare gas in pipe 166 Connected to the pipe 167 is a He gas supply source 170 for supplying a rare gas, He gas. The B ₂ H ₆ gas, Ar gas, and He gas reach the gas diffusion space 111 of the shower head 110 from the gas supply sources 168, 169, 170 through the pipes 165, 166, 167 and the gas flow path 113, and the gas discharge holes The wafer 112 is discharged toward the wafer W in the chamber 101.

  The pipe 165 is provided with a flow controller 165a such as a mass flow controller and an on-off valve 165b, the pipe 166 is provided with a flow controller 166a and an on-off valve 166b, and the pipe 167 is provided with a flow controller 167a and an on-off valve A valve 167 b is provided.

  The gas shower head 110, the gas supply sources 168, 169, 170 and the pipes 165, 166, 167 constitute a gas supply mechanism 106.

  An exhaust port 122 is provided at the lower side wall of the chamber 101, and an exhaust pipe 123 is connected to the exhaust port. The exhaust pipe 123 is connected to an exhaust device 124 including a vacuum pump, an automatic pressure control valve, and the like. By operating the vacuum pump of the exhaust device 124, the gas in the chamber 101 is exhausted through the exhaust pipe 123, and the inside of the chamber 101 is controlled to a predetermined degree of vacuum by the automatic pressure control valve.

  A loading / unloading port 125 for loading / unloading the wafer W with a vacuum transfer chamber (not shown) adjacent to the boron-based film forming apparatus 200 is provided on the side wall of the chamber 101. Is opened and closed by the gate valve 126.

  The mounting table 102 includes a plasma generation high frequency power source 107 for supplying a first high frequency power of a first frequency for plasma generation, and a second high frequency power for applying a bias voltage and having a second frequency lower than the first frequency. And a high frequency power supply 109 for supplying a bias voltage. The plasma generation high frequency power source 107 is electrically connected to the mounting table 102 via the first matching unit 106. The bias voltage application high frequency power source 109 is electrically connected to the mounting table 102 via the second matching unit 108. The plasma generation high frequency power supply 107 applies a first high frequency power of 40 MHz or more, for example, 60 MHz to the mounting table 102. The bias voltage application high frequency power source 109 applies a second high frequency power of 3 to 13.56 MHz, for example, 3 MHz to the mounting table 102. The first high frequency power may be applied to the gas shower head 110. An impedance adjustment circuit 130 is connected to the gas shower head 110.

  The first matching unit 106 matches the load impedance to the internal (or output) impedance of the plasma generation high frequency power supply 107, and outputs the output impedance of the plasma generation high frequency power supply 107 when plasma is generated in the chamber 101. The load impedances function to seemingly match. The second matching unit 108 matches the load impedance to the internal (or output) impedance of the high frequency power supply 109 for bias voltage application, and generates plasma of the high frequency power supply 109 for bias voltage when plasma is generated in the chamber 101. It functions so that internal impedance and load impedance seem to be in agreement.

  By increasing the frequency of the plasma generation high frequency power source 107 to 40 MHz or more and providing the impedance adjustment circuit 130, the impact of ions on the wafer W can be reduced, and the increase in the surface roughness of the boron film can be suppressed. Can.

  The boron-based film forming apparatus 200 has a control unit 150. The control unit 150 controls each component of the boron-based film forming apparatus 200, such as valves, a flow rate controller, a heater power supply, and high frequency power supplies 107 and 109. 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. A program for controlling processing to be executed by the boron-based film forming apparatus 200, that is, a storage medium storing a processing recipe is set in the storage device, and the main control unit is configured to store predetermined data stored in the storage medium. A processing recipe is called, and based on the processing recipe, control is performed to cause the boron-based film forming apparatus 200 to perform predetermined processing.

  When the method of the first embodiment is carried out in the boron-based film forming apparatus 200 configured as described above, first, the gate valve 126 is opened, and the wafer W is carried into the chamber 101 and the mounting table 102. And the gate valve 126 is closed.

  Then, the boron film is formed and planarized in the same sequence as ST1 to ST6 in the above-described example. The gas flow rate, pressure, and temperature at this time are also the same as in the above-described example, and only the plasma generation method and conditions are different.

In the apparatus of this embodiment, when forming a boron film, the B ₂ H ₆ gas and Ar gas and He gas which are rare gases are supplied into the chamber 101 at a predetermined flow rate, and from the high frequency power supply 107 for plasma generation. A first high frequency power for plasma generation is applied to the mounting table 102 to form a high frequency electric field between the gas shower head 110 as the upper electrode and the mounting table 102 as the lower electrode to generate capacitively coupled plasma. A boron film is formed by plasma CVD. At this time, the bias voltage (high frequency bias) from the high frequency power supply 109 for bias voltage application is not applied.

During the planarization process, the B ₂ H ₆ gas and the He gas are purged after the chamber 101 is purged while the plasma in the chamber 101 is maintained without stopping the high frequency power supply 107 for plasma generation as in the above-described example. After stopping, the plasma is changed to Ar plasma, and planarization treatment is performed by Ar ions in Ar plasma. At this time, the high frequency power supply 109 for bias voltage application is turned on, and a high frequency bias is applied to the mounting table 102.

  When the method of the second embodiment is performed in the boron-based film forming apparatus 200, ST1 to ST5 are similarly repeated a predetermined number of times, and the purge of ST6 is finally performed, or ST1 to ST5 are performed. After the above, ST3 to ST5 are repeated a predetermined number of times, and the purge of ST6 is finally performed, so that the above ST3 to ST5 are performed again while maintaining the plasma without turning off the high frequency power supply 107 for plasma generation.

  Also in the apparatus of this example, as in the above apparatus, by performing the film formation of the boron film and the flattening process once until the film thickness of the boron film is about 300 nm, the RMS is 2 nm or less, and further 1 nm or less Can be realized. Further, since the treatment is performed with a rare gas ion, no chemical reaction occurs, and film reduction and impurity contamination hardly occur.

  When the thickness of the boron film is larger, for example, 1 μm or more, the boron film should be formed with a predetermined thin thickness and the boron film flat as in the case of the above device. By repeating the conversion process a plurality of times, planarization with an RMS of 2 nm or less can be realized.

  Furthermore, even in the boron-based film forming apparatus 200 of this example, similar to the boron-based film forming apparatus 100, these processes can be performed by being able to perform the film formation and the planarization process of the boron film in one chamber 101, etc. It can be done with high throughput.

  Furthermore, similarly to the processing by the boron film forming apparatus 100, the high frequency bias is not applied to the wafer W (the mounting table 102) in forming the boron film by plasma CVD, and the high frequency bias is applied in the planarization processing. Therefore, problems such as deterioration of the boron film do not occur at the time of film formation of the boron film, and the action of rare gas ions such as Ar ions on the boron film is enhanced by applying a high frequency bias at the time of planarization. Can further enhance the effect of flattening.

<Example of experiment>
Next, experimental examples will be described.
[Experimental Example 1]
Here, the effect of Ar plasma processing was confirmed.
Using the apparatus shown in FIG. 7, the film thickness is 260 nm by plasma CVD with microwave plasma under the conditions of stage temperature: 300 ° C., pressure: 50 mTorr, microwave power: 3.5 kW, B ₂ H ₆ flow rate: 500 sccm, time: 10 min. As-deposited samples (as depo samples) were prepared. Similarly, after a boron film is formed to a film thickness of 260 nm, the stage temperature: 300 ° C., pressure: 50 mTorr, microwave power: 3.0 kW, Ar gas flow rate: 500 sccm, high frequency bias: 900 W in the same apparatus. A sample (Ar plasma-treated sample) subjected to Ar plasma treatment was produced under the condition of time: 1 min. And these surface states were compared.

  The results are shown in FIG. FIG. 10 is an SEM photograph of a cross section and a bird view of an as depo sample and an Ar plasma treated sample. As shown in these figures, the surface of the boron film is planarized by Ar plasma treatment, and the surface roughness RMS of the as depo boron film is 2.2 nm, whereas the surface of the boron film after Ar plasma treatment is The roughness RMS was 0.8 nm, and it was confirmed that the boron film surface roughness RMS was flattened to 1 nm or less by Ar plasma treatment. In addition, film reduction and impurity contamination were hardly generated by Ar plasma treatment.

  Next, similarly, after forming a boron film to a film thickness of 260 nm, a sample was prepared which was subjected to the same He plasma processing as Ar plasma processing except that Ar gas was replaced with He gas in the same apparatus. The surface states of this sample and the above as depo sample and Ar plasma treated sample were compared.

  The results are shown in FIG. FIG. 11 is an AFM image of these samples. As shown in these, the surface roughness RMS of the He plasma-treated sample was flattened more than the 1.8 nm and as depo samples. However, it did not reach RMS 0.8 nm of the sample subjected to Ar plasma treatment.

[Experimental Example 2]
Here, the influence of the processing time of Ar plasma processing on surface roughness was grasped.
Similar to Experimental Example 1, plasma plasma plasma by microwave plasma under the conditions of stage temperature: 300 ° C., pressure: 50 mTorr, microwave power: 3.5 kW, B ₂ H ₆ flow rate: 500 sccm, time: 10 min. After forming a boron film by CVD, the time of Ar plasma processing was changed in the same apparatus. The conditions for Ar plasma processing were stage temperature: 300 ° C., pressure: 50 mTorr, microwave power: 3.0 kW, Ar gas flow rate: 500 sccm, and high frequency bias: 600 W. The relationship between the time and the surface roughness RMS was investigated.

  The relationship between the time and the surface roughness RMS is shown in FIG. As shown in this figure, although the Ar plasma processing time has a flattening effect even at 10 seconds, the effect is remarkable at about 60 seconds, and it is confirmed that the effect tends to be saturated at about 180 seconds.

[Experimental Example 3]
Here, the influence of the high frequency bias in Ar plasma treatment on the surface roughness was confirmed.
After forming a boron film in the same manner as in Experimental Example 2, the value of the high frequency bias of Ar plasma processing was changed to 900 W in the same apparatus. The conditions for Ar plasma processing were a stage temperature of 300 ° C., a pressure of 50 mTorr, a microwave power of 3.0 kW, an Ar gas flow rate of 500 sccm, and a time of 60 seconds. The relationship between the high frequency bias and the surface roughness RMS at that time was investigated.

The relationship between the high frequency bias and the surface roughness RMS at that time is shown in FIG. As shown in this figure, it is confirmed that the flattening effect is enhanced by applying a high frequency bias, and that the higher the value of the high frequency bias is, the more flat effect is in the range up to 900 W. It was also confirmed that the RMS was about 1 nm or less at high frequency bias of 600 W or more (power density 0.8 W / cm ² or more).

[Experimental Example 4]
Here, the effects of the second embodiment were confirmed.
First, using the apparatus shown in FIG. 7, boron is produced by plasma CVD using microwave plasma under the conditions of stage temperature: 300 ° C., pressure: 50 mTorr, microwave power: 3.5 kW, B ₂ H ₆ flow rate: 500 sccm, time: 50 min. A film was formed. FIG. 14 (a) is a SEM photograph at that time. As shown in this photograph, as a result of the thick film thickness, the growth of nuclei proceeded and the surface became rough, and the surface roughness RMS had a large value of 5.1 nm.

Next, using the apparatus shown in FIG. 7, boron is applied by plasma CVD using microwave plasma under the conditions of stage temperature: 300 ° C., pressure: 50 mTorr, microwave power: 3.5 kW, B ₂ H ₆ flow rate: 500 sccm, time: 10 min. After forming the film, the same apparatus continues using the same apparatus, stage temperature: 300 ° C., pressure: 50 mTorr, microwave power: 3.0 kW, Ar gas flow rate: 500 sccm, high frequency bias: 600 W, time: 2 min, Ar plasma A set for processing was repeated 5 cycles to form a boron film having a total film thickness of 1.5 μm. FIG. 14 (b) is a SEM photograph at that time. As shown in this photograph, Ar plasma treatment is performed before the boron film becomes thick, and by repeating such thin boron film formation and Ar plasma treatment, the total boron film thickness is 1.5 μm. The surface roughness RMS values of 1.6 nm and less than 2 nm were obtained despite the fact that

  FIG. 15 is a view showing the relationship between the film thickness of the boron film and the surface roughness RMS, and the film thickness is changed by changing the time under the same conditions as the above except the time, according to the film thickness of the boron film The change in RMS and the change in RMS due to the film thickness when Ar plasma treatment is performed under the above conditions after forming the boron film, and the Ar plasma treatment after forming a boron film with a film thickness of 300 nm under the above conditions It shows the value of RMS when repeating the set for 5 cycles.

  In the as depo boron film, the surface roughness increases as the film thickness increases, and the surface roughness RMS exceeds 5 nm at a film thickness of 1.5 μm (1500 nm), and reaches about 7 nm at a 1.8 μm (1800 nm) The When Ar plasma processing is performed after forming the boron film, the growth of the nucleus of the boron film proceeds and the surface undulation or the like occurs when the thickness of the boron film is 1.5 μm, so that the surface is sufficiently flat. Can not be achieved, and the RMS value exceeds 3 nm. On the other hand, in the case where the total film thickness is 1.5 μm by repeating the set of the film thickness 300 nm boron film deposition and the Ar plasma processing five times, the increase from the RMS with the thin boron film is extremely small, Of less than 2 nm.

<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.

  Further, in the above embodiment, the case of forming the boron-based film by plasma CVD is described, but the method of CVD is not limited, and plasma CVD may be performed by methods other than the above embodiment. And other CVD such as thermal CVD.

  Furthermore, although the boron film has been mainly described in the above embodiment, according to 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 BC film Needless to say, even in the present invention, a surface with good flatness can be obtained.

  Furthermore, the boron-based film forming apparatus described in the above-described embodiment is merely an example, and it goes without saying that the present invention can be practiced with apparatuses having various other configurations.

1, 101; chamber 2, 102; mounting table 5, 105; heater 6, 106; gas supply mechanism 9, 109; high frequency power source for bias voltage application 20; microwave plasma source 24, 124; exhaust system 50, 150; part _68,168; B 2 _{H 6} gas source 69,169; Ar gas supply source 70, 170; the He gas supply source 100, 200; boron-based film forming apparatus 107; plasma generating high frequency power source 110, showerhead to W; Semiconductor wafer (substrate to be processed)

Claims (20)

A method of forming a boron-based film for forming a boron-based film mainly composed of boron on a substrate, comprising:
Forming a boron-based film on the substrate by CVD using a processing gas containing a boron-containing gas;
And b. Planarizing the surface of the boron-based film with a plasma of a rare gas.   The method for forming a boron-based film according to claim 1, wherein argon gas is used as a rare gas in the step of performing the planarization process.   3. The method for forming a boron-based film according to claim 1, wherein in the step of performing the planarization process, a high frequency bias voltage is applied to a substrate to draw rare gas ions in the plasma into the substrate. 4. The method of forming a boron-based film according to claim 3, wherein the power density of the high frequency bias voltage is 0.4 to 1.7 W / cm < ² >.   5. The method for forming a boron film according to any one of claims 1 to 4, wherein a processing time of the step of planarizing is 10 to 600 seconds.   6. The process according to any one of claims 1 to 5, wherein in the step of forming the boron-based film, a boron film containing boron and unavoidable impurities is formed as the boron-based film. Method of forming a boron-based film. The method for forming a boron-based film according to any one of claims 1 to 6, wherein in the step of forming the boron-based film, a B ₂ H ₆ gas is used as a boron-containing gas.   The method of forming a boron-based film according to any one of claims 1 to 7, wherein in the step of forming the boron-based film, the boron film is formed by plasma CVD.   The method of forming a boron-based film according to any one of claims 1 to 8, wherein the step of forming the boron-based film further includes a rare gas as the processing gas.   10. The method of forming a boron-based film according to claim 9, wherein argon gas and / or helium gas are used as the rare gas.   11. The boron-based film according to any one of claims 8 to 10, wherein the step of forming the boron-based film and the step of performing the planarization process are continuously performed in the same apparatus. How it is formed.   12. The process according to claim 11, wherein the step of forming the boron-based film and the step of performing the planarization process are continuously performed in the same apparatus without stopping the plasma while supplying a rare gas. Of forming a boron-based film.   13. The method according to claim 11, wherein the step of forming the boron-based film is performed without applying a bias voltage to the substrate, and the step of planarizing is performed by applying a bias voltage to the substrate. Method for forming a boron-based film as described above.   The method of forming a boron-based film according to any one of claims 8 to 13, wherein the step of forming the boron-based film and the step of performing the planarization process are performed by microwave plasma. .   The step of forming the boron-based film and the step of performing the planarization process are performed at a pressure of 0.67 to 33.3 Pa and a temperature of 500 ° C. or less. A method of forming a boron-based film according to any one of the items 1 to 4.   The method for forming a boron-based film according to any one of claims 1 to 15, wherein the step of forming the boron-based film and the step of performing the planarization process are repeated a predetermined number of times.   17. The boron according to claim 16, 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 step of planarizing treatment. Method of forming a base film   The method of forming a boron-based film according to claim 17, wherein in the step of forming the boron-based film, the film thickness per one time is 10 nm or more. A boron-based film forming apparatus for forming a boron-based film mainly composed of boron on a substrate, comprising:
A chamber for containing a substrate,
A mounting table for supporting a substrate in the chamber;
A gas supply mechanism for supplying a processing gas containing at least a boron-containing gas and a rare gas into the chamber;
An exhaust device for exhausting the inside of the chamber;
Plasma generation means for generating plasma in the chamber;
A processing gas containing the boron-containing gas is supplied into the chamber by the gas supply mechanism, plasma of a gas containing the boron-containing gas is generated by the plasma generation means, and the boron-based film is formed. A processing gas containing the noble gas is supplied into the chamber by a gas supply mechanism, and plasma of a gas containing the noble gas is generated by the plasma generation means to perform a planarization process on the surface of the boron-based film. An apparatus for forming a boron-based film, comprising: a control unit to control.   The apparatus further includes high frequency bias voltage application means for applying a high frequency bias voltage to the substrate via the mounting table, and the control unit is configured to apply the high frequency bias voltage application means when the boron-based film is formed. 20. The apparatus for forming a boron-based film according to claim 19, wherein said control is performed so that said high frequency bias voltage is applied to said substrate by said high frequency bias voltage applying means during said flattening process.